Early May (1st-7th) Severe Chances

[andyhb]

Yeah, I had a feeling the UL forcing would diminish rapidly with southward extent, it looks rather anemic beyond Tuesday.

[IWXwx]

It looks like there will be daily "minor" threats this week, gravitating from Texas today to our subforum's area by midweek.

The possibility is there, but it's really hard to pinpoint the exact timing and location of convection in this kind of pattern.

There's often a diurnal cycle to MCS development superimposed on the timing of the triggering synoptic waves. Often a nocturnal MCS will form first on the nose of the initial 850 LLJ surge, being mostly elevated instability with mainly a heavy rain and isolated hail threat. Then subsequent severe convection will fire the following afternoon/evening on the southern outflow boundaries set up by the initial MCS.

You really gotta have the shear parameters and jet/synoptic forcing correlating well with the diurnal cycle to get a widespread severe outbreak. It seems to happen so often that great shear and instability is in place, but the jet streak will be in the wrong place with the right-exit or left-entrance, rather than left-exit or right-entrance region overhead, and as a result the cap remains largely in place. Or the jet dynamics might be perfect, but only after a previous nocturnal/morning MCS wiped most of all the instability.

In any case, with no major surface low development, just a series of waves rippling through the SW flow, I don't see a whole lot of directional shear for supercells, except possibly isolated ones near surface boundaries.

Based on what I see on the 28/12z ECMWF and GFS, it seems to me that the severe weather threat will move north the next 7 days or so. It could impact the Upper Mississippi Valley on Tuesday and than move into the western Great Lakes on Wednesday, including southern WI and Northern IL. From there it could affect the central great lakes area south into the OH valley area. The ECMWF shows it also could impact the Upper Mississippi Valley area next weekend.

I am moderately surprised that more attention hasn't been paid to this potential threat on the various different threads. Seems strange to me how quiet the conversation's have been about this.

I did make brief mention of this in the other thread. Frostfern hit the nail on the head. To try to pinpoint any particular threat at this juncture would be very speculative. Even SPC removed their threat area on their 4-8 last night. Not to worry, severe enthusiasts are watching this pattern closely and it will be a day-by-day thing.

[Indystorm]

Agree with recent posters here regarding this week's svr thinking as I plan to head out to the Ozarks region for a little vacation and it would be nice not to have to worry about svr wx. But remember, the jet was not all that strong for Saturday's huge hailers in the St. Louis metro area either. Models can and do change as well. I've learned that svr wx forecasting is basically a day of concern unless you have a huge trough coming in that you can see a week ahead.

[TimChgo9]

I noted yesterday's D5 with a bit of interest, and with that same interest noted that it was not present this morning, on what would be D4.

I think this is going to be a day by day thing, and wouldn't be surprised at all to the the SLGT risk returned in tomorrows D3. LOT is looking at a chance of rain, and storms early on Wednesday, with more storms possible late, and then hinting at severe possibilities for late Wednesday. Of course, this was yesterday's forecast, haven't looked at the what the current one says. That being said, if we are due for a rain/storms Wednesday, early, then that means an MCS is expected through the area at one point or another (either in the overnight, or in the very early morning 4am-6am) The early morning MCS's tend to reduce our chances for later in the day storms, depending on how rapidly it clears out, and how much day time heating we get.

Nonetheless, I will be keeping and eye on this....

OT: Check out this wind map. It's an "art project" so to speak, but it is useful in showing wind patterns. Tom Skilling linked it on his FB page about 2 weeks ago. It's zoomable, but the drawbacks are that it doesn't show state boundaries, nor does it show the Great Lakes. Other than that it's cool. :-) .

http://hint.fm/wind/

[Thundersnow12]

You see that on TV? I wonder if Thundersnow was out today.

lol no not me.

[Geos]

lol no not me.

Lol, I was confused at what BowMe was exactly getting at.

Didn't see you here yesterday - thought you might have went chasing those hail makers!

Nice collection of video/news clips of the hail storms in St. Louis. http://kplr11.com/2012/04/29/hail-damage-ofallon-il-maryland-heights-storms/

Last one is particularly good - shows baseball hail falling in Maryland Heights.

[Hoosier]

Yeah, the upper level winds aren't looking good, but there is still 30-50 kts at 500 mb.  I think this means that convective mode could tend to get a little messy but even with this scenario I'd still say there is a relatively decent chance of severe weather in the mid to late week period.

[Hoosier]

Right now, seems like the NAM would be most favorable with stronger flow overlapping the warm sector.

[andyhb]

The 12z NAM suggests Tuesday could be rather substantial, although primarily west of the forum's coverage area. That said, there are still several factors that could limit this, and the Global guidance isn't exactly as enthusiastic as the NAM in any sense of the word.

[frostfern]

As usual it looks like all the lower and upper level jet dynamics is trending further NW with each model run. It doesn't look too promising for SW Michigan. Not with the SW flow off Lake Michigan in the warm sector. It seems like to get a good spring severe weather outbreak here in western Michigan, you need a strong surface low nearby. If it was early July with 3000 j/kg CAPE, dp's in the lower 70s, and lake temperatures near the same, this pattern would be enough for a nasty bow-echo. For springtime though the dynamics aren't all that impressive.

[frostfern]

Hmm...

New NAM looks good for MN and WI on Wednesday. Now Thursday looks like the better day for MI.

[hm8]

DTX

WITH THIS SOUTHWEST FLOW PATTERN SETTING UP...MOISTURE/INSTABILITY

WILL BE ON A STEADY INCREASE INTO THE MIDDLE OF THE WEEK AS WELL

WITH THE AFOREMENTIONED SHORTWAVE IMPULSES HELPING TO TRIGGER

PERIODIC EPISODES OF SHOWERS/THUNDERSTORMS...PARTICULARLY INTO THE

THURSDAY TIME FRAME. WHILE IT IS A BIT TOO FAR OUT TO GET VERY

SPECIFIC...WOULD ANTICIPATE THAT INSTABILITY SHOULD BE SUFFICIENT BY

PERHAPS LATE WEDNESDAY AND MOST DEFINITELY BY THURSDAY TO SUPPORT

SEVERE WEATHER GIVEN OUR RELATIVE PROXIMITY TO THE STRONGER MID

LEVEL WEST/SOUTHWEST WHICH MAXIMIZES TO OUR NORTHWEST OVER THE UPPER

MIDWEST/NORTHERN GREAT LAKES. MODEST MID LEVEL FLOW ALONG THE

SOUTHERN EDGE OF THESE STRONGER WINDS WOULD BE MORE THAN SUFFICIENT

TO BRING ORGANIZED CONVECTION AS ML CAPES REACH AT LEAST 2000-2500

J/KG BY THURSDAY.

[andyhb]

...CNTRL PLAINS THROUGH UPPER MS VALLEY AND GREAT LAKES...

LEAD IMPULSE WILL EJECT INTO SWRN QUEBEC EARLY IN THE PERIOD WITH

SWLY FLOW ALOFT BECOMING NEAR PARALLEL TO FRONT THAT WILL EXTEND

FROM MN SWWD INTO THE CNTRL PLAINS EARLY WEDNESDAY. MOIST WARM

SECTOR WILL RESIDE SOUTH OF THE FRONT WITH DEWPOINTS IN THE 60S.

STORMS WILL PROBABLY BE ONGOING AT THE START OF THE PERIOD IN THIS

REGION AND MIGHT CONTRIBUTE TO EFFECTIVE BOUNDARY RESIDING SOUTH OF

THE SYNOPTIC FRONT. INITIAL CONVECTION WILL SHIFT EWD AND

WEAKEN...ALLOWING FOR BOUNDARY LAYER DESTABILIZATION IN ITS WAKE.

THE ATMOSPHERE WILL LIKELY BECOME MODERATELY UNSTABLE DURING THE

AFTERNOON. WEAK SHORTWAVE RIDGING WILL MOVE THROUGH THE AREA BEFORE

THE NEXT UPSTREAM TROUGH APPROACHES BY EVENING. AS THE SFC LAYER

WARMS...ADDITIONAL STORMS WILL LIKELY DEVELOP ALONG THE FRONT OR

RESIDUAL OUTFLOW BOUNDARIES FROM NEB INTO THE UPPER MS VALLEY. NRN

EXTENT OF WARM SECTOR WILL REMAIN WITHIN BELT OF STRONGER WLYS WITH

VERTICAL SHEAR SUFFICIENT FOR ORGANIZED SEVERE STORMS. A PORTION OF

THIS AREA MAY NEED TO BE INCLUDED IN HIGHER PROBABILITIES IN LATER

OUTLOOKS ONCE UNCERTAINTY REGARDING THE EVOLUTION OF THE EARLY

CONVECTION HAS BEEN MITIGATED.

..DIAL.. 04/30/2012

[Stebo]

DTX's take on later in the week

FOR THE REST OF THE WEEK...THE WEATHER PATTERN IS SURE TO BECOME A

HEADACHE. MODELS ARE IN AGREEMENT THE MAIN UPPER LEVEL JET AXIS WILL

BE IN POSITION IMMEDIATELY NORTH OF THE GREAT LAKES FROM WEST TO

EAST. THIS POSITION IS NORTH ENOUGH TO ALLOW HIGHER THETA E CONTENT

TO RIDGE INTO AND SPREAD ACROSS SOUTHEASTERN MICHIGAN...BUT CLOSE

ENOUGH TO ALLOW THE VARIOUS TRAVELING SHORTWAVES TO EXERT A DIRECT

INFLUENCE/IMPACT ON THE CWA. IT IS SURE TO BE AN ACTIVE TIME

PERIOD...BUT A VERY LOW CONFIDENCE FORECAST IN TIMING THE EPISODIC

PRECIPITATION/SHOWER/THUNDERSTORMS. WILL HIGHLIGHT...A BETTER CHANCE

APPEARS WEDNESDAY NIGHT AS A RIGHT ENTRANCE REGION DEVELOPS ON A

UPPER LEVEL JETLET. THE AREA OF HEIGHT FALLS ASSOCIATED WITH THIS

FORCING IS EXPECTED TO BRING A CONCERTED PUSH OF SOUTHERLY

FLOW/MOISTURE NORTHWARD INTO LOWER MICHIGAN ON A SECONDARY WARM

FRONTAL SURGE. THAT SUPPORTS THE INHERITED LIKELY POPS. TEMPERATURES

WARMING TO NEAR 80 DEGREES WITH DEWPOINTS IN THE 60S BOTH

WEDNESDAY/THURSDAY BRINGS CONCERN FOR SOME STRONGER THUNDERSTORM

ACTIVITY. NOT SEEING MUCH IN THE WAY OF STRONG EML ADVECTIONS INTO

THE STATE...WHICH KEEPS THE 700-500MB LAYER RELATIVELY COOL. A

POSITIVE FOR CAPE DENSITIES AND RESULTANT CONVECTIVE VIGOR. LATEST

MODEL DATA KEEPS THE WET/UNSETTLED PATTERN GOING RIGHT INTO THE

WEEKEND.

GRR's take for later in the week

WE CONTINUE TO MONITOR THE POTENTIAL FOR STRONG THUNDERSTORMS

WEDNESDAY THROUGH FRIDAY AS A FRONTAL SYSTEM WIGGLES AROUND THE

GREAT LAKES.

MY OVERALL CONFIDENCE IN THIS FORECAST IS HIGH AT THE START BUT

FADES INTO THE WEEKEND. THE DEEPENING WEST COAST TROUGH HELPS BUILD

AN UPPER RIDGE OVER THE CENTRAL PLAINS INTO THE GREAT LAKES MID

WEEK. ONCE THERE IT LARGELY HOLDS INTO THE WEEKEND THAT FORCES THE

POLAR JET NORTH OF THE CANADIAN BOARDER BY WEDNESDAY AND IT STAYS

THERE INTO SATURDAY. MEANWHILE THERE IS AN ISSUE WITH HOW FAR SOUTH

A DIGGING UPPER LEVEL SYSTEM OVER NORTHEASTERN CANADA ACTUALLY DIGS

SOUTHWARD TOWARD THE NORTHERN CONUS IN THE THURSDAY TO FRIDAY TIME

FRAME. THE TREND OVER THE PAST FEW DAYS IS LESS DIGGING INTO THE

NORTHERN CONUS IN THE FRIDAY TIME FRAME.

THAT ALL OF THIS MEANS IS THE WARM FRONT PUSHES THROUGH WITH

THUNDERSTORMS WEDNESDAY MORNING WITH A 40 KNOT LOW LEVEL JET AIMED

AT SOUTHERN LAKE MICHIGAN. THAT IS OUR HIGHEST RISK TIME FOR

THUNDERSTORMS.

BEYOND THAT THEN SOUTHWEST MICHIGAN STAYS IN THE WARM AIR INTO

SATURDAY BEFORE THE REAL COLD FRONT FINALLY COMES THROUGH. BEING IN

WARM UNSTABLE AIR THROUGH MOST OF THIS TIME MEANS THERE IS THE

THREAT OF THUNDERSTORMS EACH DAY. ANOTHER JET CORE PASSES OVER

NORTHERN LOWER MICHIGAN THURSDAY NIGHT. THAT IS WITH ANOTHER

SHORTWAVE THE PUSHES A WEAK COLD FRONT SOUTH TO I-94 FRIDAY MORNING

(GFS AND ECMWF SIMILAR HERE). THAT DOES NOT REALLY PUT US IN THE

COOL AIR THROUGH. THEN ANOTHER FRONTAL WAVE SEEMS TO COME ALONG

FRIDAY NIGHT INTO SATURDAY. THAT SHOULD BRING THE COLDER AIR IN

LATER SATURDAY. THROUGH THE WED AFTERNOON INTO SATURDAY TIME FRAME

THE UPPER JET STAYS IN CANADA. SO THERE IS NOT MUCH DEEP LAYERED

SHEAR. SO WHILE SURFACE CAPES ARE ABOVE 2000 J/K AT TIMES... AND THE

TQ INDEX STAYS ABOVE 18C INTO SAT EVENING... WITH NOT MUCH UPPER JET

FORCING ORGANIZED SEVERE STORMS SEEM UNLIKELY AT THIS TIME.

ONE OTHER POINT... THE 1000/925 MB THICKNESS FORECAST FIELDS KEEP

WARMING WITH EACH NEW MODEL RUN FOR WED - FRI. IT WOULD SEEM GETTING

INTO THE 80S (AWAY FROM LAKE MICHIGAN) IS LIKELY EVEN WITH SOME

CLOUDS AROUND EACH AFTERNOON.

Personally at this juncture I think at least pulse severe looks possible across MI for Wed/Thurs with the instability in place. If any ripple comes along during that time frame that would enhance the chances considerably. Friday into Saturday as the front drops South a better chance at severe would present itself as better forcing moves into the area along with a trigger (the front). Heavy rain will be a very substantial threat with anything this week, PWATs are high for this time of the year, from Tuesday until Sunday/Monday the PWATs stay around 1.2" or higher for most of the region. So needless to say any storms that form will be accompanied by heavy rains something many in the region could use hopefully not all at once.

[Stebo]

SPC's Day 4-8 hinting at eventual Friday risk area.

MODEL CONSENSUS IS THAT A GENERAL QUASI-ZONAL FLOW PATTERN WILL

REMAIN OVER THE U.S. THROUGH DAY 5 BEFORE AND UPPER LOW EVOLVES OVER

THE WRN STATES. SEVERAL IMPULSES WILL MOVE THROUGH THIS REGIME WITH

MODEL DIFFERENCES IN TIMING AND AMPLITUDE OF THESE SMALLER SCALE

FEATURES. BEST CHANCE FOR A GREATER COVERAGE OF ORGANIZED SEVERE

STORMS THROUGH DAY 5 WILL EXIST FROM ERN PARTS OF THE CNTRL PLAINS

INTO THE UPPER MS VALLEY...GREAT LAKES AND OH VALLEY REGIONS. A

CATEGORICAL RISK WILL LIKELY NEED TO BE INTRODUCED AT SOME POINT.

HOWEVER...GIVEN THAT HIGHER SEVERE COVERAGE LOCATION ON A GIVEN DAY

WILL DEPEND ON MESOSCALE DETAILS SUCH AS EVOLUTION OF EARLY

CONVECTION AS WELL AS TIMING AND STRENGTH OF INDIVIDUAL SHORTWAVE

TROUGHS...OVERALL PREDICTABILITY FOR A 30% OR GREATER COVERAGE AREA

REMAINS LOW AT THIS TIME.

[hawkeye_wx]

Euro is showing a cluster/line of strong storms moving through eastern Iowa for five straight nights beginning Tuesday night. This is the first time I've had access to detailed Euro maps, so I don't know how well it handles convection in this kind of pattern, but it should at least be an interesting week.

[A-L-E-K]

Euro is showing a cluster/line of strong storms moving through eastern Iowa for five straight nights beginning Tuesday night. This is the first time I've had access to detailed Euro maps, so I don't know how well it handles convection in this kind of pattern, but it should at least be an interesting week.

based on pattern alone, we should be in line for a few rounds during this period. Not so sure about severe but I don't really care about that anyways.

[wisconsinwx]

based on pattern alone, we should be in line for a few rounds during this period. Not so sure about severe but I don't really care about that anyways.

Yeah, I would agree, but I hope at least one of these rounds occur during the day. At the end of the day, the anticipation of MCS' moving in and watching the skies darken is the most interesting aspect of severe weather for me. It's been awhile (last September) since I've had that opportunity.

[Geos]

Yeah, I would agree, but I hope at least one of these rounds occur during the day. At the end of the day, the anticipation of MCS' moving in and watching the skies darken is the most interesting aspect of severe weather for me. It's been awhile (last September) since I've had that opportunity.

Wednesday night definitely looks like a high probability of t-storms. Looks like 60% chance here. Seems like the pattern for a lot of MCS' has been from NW/NC IA to the east and east southeast the last several summers.

I like seeing the shelf and roll clouds move in during the day!

[frostfern]

I think this is a good setup for nocturnal MCS action in my area. It's just that the afternoon/evening trigger zone looks to stay further west in the IA, WI, IL region which is where the LLJ will be more squarely aimed at most of the time. If a stronger surface circulation can develop later in the period there might be enough backing to set up an afternoon lake breeze trigger. Not that any models are showing that at the moment, but I can hope. It looks more like a setup for night-time heavy rain producers to me though, at least here in MI. Lake Michigan always puts a damper on afternoon outbreaks this time of year. The lake isn't as cold as normal for this time of year though, considering the mild winter and spring, so that's a plus.

[Geos]

I think this is a good setup for nocturnal MCS action in my area. It's just that the afternoon/evening trigger zone looks to stay further west in the IA, WI, IL region which is where the LLJ will be more squarely aimed at most of the time. If a stronger surface circulation can develop later in the period there might be enough backing to set up an afternoon lake breeze trigger. Not that any models are showing that at the moment, but I can hope. It looks more like a setup for night-time heavy rain producers to me though, at least here in MI. Lake Michigan always puts a damper on afternoon outbreaks this time of year. The lake isn't as cold as normal for this time of year though, considering the mild winter and spring, so that's a plus.

A lot of times Lake Michigan kills the severe weather here too. Especially April and May. I think SW winds are forecast for Wednesday, that might take western MI out of the severe picture. The lake is above normal, but not what it was in March! You can see our warm up nicely on this graph;

[wisconsinwx]

A lot of times Lake Michigan kills the severe weather here too. Especially April and May. I think SW winds are forecast for Wednesday, that might take western MI out of the severe picture. The lake is above normal, but not what it was in March! You can see our warm up nicely on this graph;

Yeah, I was going to say that as well for areas of Illinois and Wisconsin within about 30 miles or so of the lake. It doesn't help that the afternoon development this time of year tends to be near the Upper Mississippi Valley, and we get the leftovers, which are oftentimes still severe, but tough to get supercells developing nearby this time of year.

[frostfern]

A lot of times Lake Michigan kills the severe weather here too. Especially April and May. I think SW winds are forecast for Wednesday, that might take western MI out of the severe picture. The lake is above normal, but not what it was in March! You can see our warm up nicely on this graph;

I think if you have a strong enough low-level flow, the warm inflow layer can sometimes glide right over the lake inversion without ingesting too much lake-cooled air. The supercell that produced the April 3, 1956 Hudsonville-Standale tornado survived crossing lake Michigan. In that case though the wind was backed to the SSE due to a strong surface low, so storms intensified as the came onshore.

What the lake does tend to do is inhibit new thunderstorm formation. If a storm doesn't already have a well established inflow by the time it reaches the lake it tends to eat the cold air and croak. Nothing ever forms during peak daytime heating hours directly over the lake. We always have to wait for already well-established convection to cross the lake, and by that time it's often well past peak-heating. That is unless the winds are backed enough to set up a lake-breeze trigger.

[A-L-E-K]

I think if you have a strong enough low-level flow, the warm inflow layer can sometimes glide right over the lake inversion without ingesting too much lake-cooled air. The supercell that produced the April 3, 1956 Hudsonville-Standale tornado survived crossing lake Michigan. In that case though the wind was backed to the SSE due to a strong surface low, so storms intensified as the came onshore.

What the lake does tend to do is inhibit new thunderstorm formation. If a storm doesn't already have a well established inflow by the time it reaches the lake it tends to eat the cold air and croak. Nothing ever forms during peak daytime heating hours directly over the lake. We always have to wait for already well-established convection to cross the lake, and by that time it's often well past peak-heating. That is unless the winds are backed enough to set up a lake-breeze trigger.

happens all the time

[Bryan Wood]

I think if you have a strong enough low-level flow, the warm inflow layer can sometimes glide right over the lake inversion without ingesting too much lake-cooled air. The supercell that produced the April 3, 1956 Hudsonville-Standale tornado survived crossing lake Michigan. In that case though the wind was backed to the SSE due to a strong surface low, so storms intensified as the came onshore.

What the lake does tend to do is inhibit new thunderstorm formation. If a storm doesn't already have a well established inflow by the time it reaches the lake it tends to eat the cold air and croak. Nothing ever forms during peak daytime heating hours directly over the lake. We always have to wait for already well-established convection to cross the lake, and by that time it's often well past peak-heating. That is unless the winds are backed enough to set up a lake-breeze trigger.

Correct me if I'm wrong, but didn't the Chicago hail/wind storm on June 30th of last year develop over Lake Michigan and then push ashore close to peak heating/sunset?

[Radtechwxman]

DAY 2 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

1224 PM CDT MON APR 30 2012

VALID 011200Z - 021200Z

...THERE IS A SLGT RISK OF SVR TSTMS TUE ACROSS THE NORTH CENTRAL

PLAINS/MID MISSOURI VALLEY REGION INTO THE UPPER MISSISSIPPI

VALLEY...

...SYNOPSIS...

A STRONG...GENERALLY ZONAL MID/UPPER JET ACROSS PORTIONS OF THE

NORTH CENTRAL AND NORTHEASTERN PACIFIC IS CURRENTLY NOSING INTO THE

PACIFIC NORTHWEST COAST...WHERE A SIGNIFICANT SHORT WAVE IMPULSE IS

IN THE PROCESS OF MIGRATING INLAND. MODELS ARE SUGGESTIVE THAT THIS

FEATURE WILL CONTINUE EASTWARD INTO THE NORTHERN ROCKIES BY 12Z

TUESDAY...BEFORE SLOWLY LIFTING INTO THE CENTRAL CANADIAN/U.S.

BORDER AREA...AS ANOTHER PERHAPS STRONGER IMPULSE MIGRATES INLAND

ACROSS THE PACIFIC NORTHWEST COAST AND NORTHERN INTERMOUNTAIN

REGION. AS THIS OCCURS...MID/UPPER RIDGING NOW BUILDING THROUGH

MUCH OF THE SOUTHEAST IS EXPECTED TO EXPAND NORTHWARD THROUGH MOST

AREAS EAST OF THE MISSISSIPPI VALLEY.

IN LOWER LEVELS...AIDED BY AN INFLOW OFF AN INCREASINGLY MOIST GULF

BOUNDARY LAYER...CONTINUED SLOW MOISTENING IS EXPECTED THROUGH MOST

AREAS EAST OF THE HIGH PLAINS. A DRY LINE MAY SHARPEN ACROSS THE

PLAINS BY LATE TUESDAY AFTERNOON...TO THE SOUTH OF A WEAK SURFACE

FRONTAL WAVE WHICH MAY MIGRATE FROM THE NORTH CENTRAL PLAINS THROUGH

THE UPPER MISSISSIPPI VALLEY/GREAT LAKES REGION. THIS LATTER

FEATURE IS EXPECTED TO PROVIDE A GENERAL FOCUS FOR THE MOST

SIGNIFICANT CONVECTIVE POTENTIAL DURING THIS PERIOD...BUT

THUNDERSTORMS WILL ALSO BE POSSIBLE ON THE SOUTHERN FRINGE OF THE

WESTERLIES...ACROSS THE GREAT BASIN INTO THE CENTRAL ROCKIES AND

ADJACENT HIGH PLAINS...AS WELL AS WITHIN A GENERAL LOWER/MID

TROPOSPHERIC WARM ADVECTION REGIME ACROSS THE OHIO VALLEY AND MID

ATLANTIC COAST STATES. OTHER THUNDERSTORMS APPEAR POSSIBLE IN MOIST

SOUTHEASTERLY LOW-LEVEL FLOW ACROSS PARTS OF THE GULF

STATES...PARTICULARLY WHERE SEA BREEZES ENHANCE LOW-LEVEL

CONVERGENCE.

...N CNTRL PLAINS/MID MO VALLEY INTO UPPER MISSISSIPPI VALLEY...

TORNADIC POTENTIAL FOR THIS PERIOD REMAINS A BIT UNCLEAR. LARGE

CLOCKWISE CURVED LOW-LEVEL HODOGRAPHS COINCIDING WITH STRONGER DEEP

LAYER SHEAR MAY REMAIN CONFINED TO THE IMMEDIATE VICINITY OF A

NORTHWARD LIFTING WARM FRONTAL ZONE ACROSS THE UPPER MISSISSIPPI

VALLEY. THIS POTENTIAL MAY PEAK DURING THE LATE AFTERNOON/EARLY

EVENING HOURS...ACROSS PARTS OF CENTRAL MINNESOTA INTO NORTHWEST

WISCONSIN...MOST LIKELY NORTHWEST THROUGH NORTH OF MINNEAPOLIS.

WHILE CONDITIONS CONDUCIVE TO TORNADIC DEVELOPMENT MAY BE LIMITED TO

A RELATIVELY NARROW CORRIDOR...IT APPEARS POSSIBLE THAT WIND

PROFILES MAY BE SUPPORTIVE OF STORM MOTION TRACKING ALONG THE WARM

FRONT. ONE OR TWO LONG LIVED SUPERCELLS MAY NOT BE OUT THE

QUESTION...WITH THE RISK FOR A STRONG TORNADO.

OTHERWISE...LATE AFTERNOON STORM DEVELOPMENT IS STILL EXPECTED ALONG

THE COLD FRONT/DRY LINE ACROSS PARTS OF EASTERN SOUTH DAKOTA INTO

NORTHEAST NEBRASKA. LOW-LEVEL HODOGRAPHS MAY NOT BE PARTICULARLY

LARGE...BUT DEEP LAYER SHEAR SHOULD BE SUFFICIENT FOR ORGANIZED

STORM DEVELOPMENT...INCLUDING ISOLATED SUPERCELLS. IN THE PRESENCE

OF MODERATELY LARGE MIXED LAYER CAPE OF 1500-3000 J/KG...AND AT

LEAST WEAK MID-LEVEL FORCING ASSOCIATED WITH THE LEAD SHORT WAVE

IMPULSE...UPSCALE GROWTH INTO A MESOSCALE CONVECTIVE SYSTEM APPEARS

POSSIBLE BY EARLY EVENING...ACCOMPANIED BY BROADER SCALE DAMAGING

WIND POTENTIAL ACROSS PARTS OF CENTRAL/SOUTHERN MINNESOTA AND

WESTERN/NORTHERN IOWA.

...MID MS/LOWER OHIO VALLEY INTO THE MID ATLANTIC STATES...

ONE OR TWO SHORT WAVE IMPULSES EMBEDDED WITHIN 30-40+ KT WESTERLY

MID-LEVEL FLOW COULD HELP FOCUS AREAS WITH AT LEAST A LOCALIZED

STRONG/SEVERE STORM THREAT ON TUESDAY. HOWEVER...CONSIDERABLE

UNCERTAINTY REMAINS...DUE IN PART TO THE TENDENCY FOR AT LEAST WEAK

LARGER-SCALE MID-LEVEL HEIGHT RISES...AND EARLY DAY CONVECTIVE CLOUD

COVER WHICH MAY STRONGLY RESTRICT BOUNDARY LAYER DESTABILIZATION.

...CENTRAL/SOUTHERN PLAINS...

ISOLATED TO WIDELY SCATTERED STORM DEVELOPMENT IS NOT OUT OF THE

QUESTION ALONG THE DRY LINE. HOWEVER...IT STILL APPEARS PROBABLE

THAT WARM MID-LEVELS WILL TEND TO BE INHIBITIVE...EXCEPT PERHAPS

WHERE OROGRAPHY AIDS FORCING ACROSS PARTS OF SOUTHWEST TEXAS.

..KERR.. 04/30/2012

New Day 2 outlooks mentions the possibility of long lived supercells with a strong tornado threat. I can definetely see this happening with the relatively backed low level flow in the warm front corridor coiniciding with moderate to strong instability. Wind shear will also be enhanced in this region. If I were to chase tomorrow I would def make a play on the warm front in a more zonal flow setup like this. Storms will most likely line up fast on the cold front with a more unidirectional wind profile.

[frostfern]

happens all the time

But then it's not due directly to heating but due to transport of the more unstable air over the top of the stable marine layer. You need a good low-level wind flow and forcing to keep it going.

[Chicago Storm]

Correct me if I'm wrong, but didn't the Chicago hail/wind storm on June 30th of last year develop over Lake Michigan and then push ashore close to peak heating/sunset?

Correct.

[Geos]

Correct me if I'm wrong, but didn't the Chicago hail/wind storm on June 30th of last year develop over Lake Michigan and then push ashore close to peak heating/sunset?

Yeah, that storm was one of the most destructive in the area all summer! Formed right near the shore by Racine. That was an 80° day with offshore winds.

[Hoosier]

But then it's not due directly to heating but due to transport of the more unstable air over the top of the stable marine layer.  You need a good low-level wind flow and forcing to keep it going.

I'm not sure I agree. The lapse rate between the lake water and the air just above (like feet above) is often very steep. Over the lake, the slice of the atmosphere affected by the lake is usually thin. Not saying development over the lake is never retarded but I think you are overblowing it.