100 replies to this topic

[tornadotony]

In the broad, general synoptic sense, the confluent flow in the warm sector, the deep low, and intense yet compact shortwave are hallmarks of a Midwestern tornado outbreak. A lot needs to be realized, however, to make that a reality. If we see the general moisture/instability fields that the GFS has be realized, then we've got a good shot at a tornado event of substance next week for the upper 1/3 of the Mississippi valley.

[Hoosier]

In the broad, general synoptic sense, the confluent flow in the warm sector, the deep low, and intense yet compact shortwave are hallmarks of a Midwestern tornado outbreak.  A lot needs to be realized, however, to make that a reality. If we see the general moisture/instability fields that the GFS has be realized, then we've got a good shot at a tornado event of substance next week for the upper 1/3 of the Mississippi valley.

My biggest concern at this point is probably the moisture return.

[MnWeatherman]

Monday looks downright nasty. Hodos are off the hook, dewpoints in the 60s with temps in upper 70s/ low 80s in central south dakota. It appears the ECMWF did lead the way and now 18z GFS is similar in track and timing.

[baroclinic_instability]

My biggest concern at this point is probably the moisture return.

Yeah I agree with that. The rapid ejection with a relatively short period of leeside troughing combined with the weak front that pushes through the GOM as that cutoff slowly progresses eastward won't be conducive to rich moisture return. Dewpoints will struggle to reach 60 since vegetation is still sparse.

[baroclinic_instability]

Monday looks downright nasty. Hodos are off the hook, dewpoints in the 60s with temps in upper 70s/ low 80s in central south dakota. It appears the ECMWF did lead the way and now 18z GFS is similar in track and timing.

I didn't see any 60F dewpoints in the ECMWF or GFS.

[MnWeatherman]

I didn't see any 60F dewpoints in the ECMWF or GFS.

Yeah, your right. Around 60 is plausible, but as of the 00z GFS run i'm a bit worried of the moisture return myself. Also, the GFS has warm 700mb temps to induce a cap. It's lagging in bringing in the cooler temps from the west, but given the amplification of this system, I wouldn't doubt if storms fire up before dark.

[brettjrob]

The best chance for convective initiation on Monday might be in the southern High Plains along the dryline, where higher theta-e air in the BL will be resident under H7 temps that are similar to those farther north. Weaker flow and high LCLs will likely mitigate the sig svr threat, though. The most potent environment kinematically will be over NE and SD, but I'm not sure moisture will recover in time.

[cyclone77]

Based on the new GFS I like south-central into central SD on Monday. Deep moisture is a bit questionable, but everything else looks great IMO. Love the kinematics, and the nice funneling of theta-e into that area.

[cyclone77]

As for Tue the GFS still forecasts very nice soundings/hodos from central/eastern Iowa up into southern Minnesota. The forecast instability is very marginal, but given the tendency for the GFS to low ball temps in these types of setups I'm not taking that too seriously. A little more instability in the presence of this highly sheared environment and we'll have a fantastic setup for tornadic supercells IMO.

[baroclinic_instability]

Some of the hodographs across SD are off the charts near/along the warm front. Obviously surface based initiation will be challenging if not possible...but much is dependent upon timing as well as the quality of ejection (i.e., how strong of a shortwave we are dealing with).

[cyclone77]

Some of the hodographs across SD are off the charts near/along the warm front. Obviously surface based initiation will be challenging if not possible...but much is dependent upon timing as well as the quality of ejection (i.e., how strong of a shortwave we are dealing with).

If we can get some surface based storms in that environment it should do quite well. Whenever we see a funneling effect of the low-level moisture/theta-e like what's being forecast by tonight's GFS into a region just ahead of the surface cyclone I always feel pretty good about chances of convection rooting into the BL. I guess we'll see how it goes.

[baroclinic_instability]

The best chance for convective initiation on Monday might be in the southern High Plains along the dryline, where higher theta-e air in the BL will be resident under H7 temps that are similar to those farther north. Weaker flow and high LCLs will likely mitigate the sig svr threat, though. The most potent environment kinematically will be over NE and SD, but I'm not sure moisture will recover in time.

The high amplitude shortwave ridge is going to cause major capping problems across the SD where the best kinematic environment exists. There may be a narrow opportunity near the surface low/cold front, but it seems much of the best environment will be strongly capped.

[baroclinic_instability]

The 00Z GEM has major capping issues...no surprise. High amplitude shortwave ridge with extreme height falls owing to a deamplifying bowling ball low in SW flow doesn't incite confidence.

[andyhb]

As for Tue the GFS still forecasts very nice soundings/hodos from central/eastern Iowa up into southern Minnesota. The forecast instability is very marginal, but given the tendency for the GFS to low ball temps in these types of setups I'm not taking that too seriously. A little more instability in the presence of this highly sheared environment and we'll have a fantastic setup for tornadic supercells IMO.

This, it does get 60s dews into E IA and IL for Tuesday (although I can still see issues with moisture quality/depth), and with that said, I can already see there is a big difference in the sfc temps between the NAM and GFS at 72 hrs. Given the likely capping problems on Monday, I tended to think Tuesday held the greater potential here, but of course that could change being 4-5 days out still.

[andyhb]

[attachment=61068:day48prob.gif]

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0345 AM CDT FRI MAR 23 2012

VALID 261200Z - 311200Z

...DISCUSSION...
THE ECMWF AND GFS MODELS ARE IN EXCELLENT AGREEMENT IN DEPICTING A
POTENT SHORTWAVE TROUGH...NOW OVER THE ERN PACIFIC...EJECTING NEWD
ACROSS WY AND INTO THE NRN HIGH PLAINS ON MON/D4. BOTH MODELS ALSO
DEPICT A DEEP SURFACE LOW...WITH 1-2 MB/HR PRESSURE FALLS PERSISTING
ALL DAY OVER SD AND WRN NEB NEAR THE SURFACE LOW. WITH THE COMPACT
NATURE OF THIS SYSTEM...A TIGHT PRESSURE FALL/RISE COUPLET IS
EXPECTED...WHICH WILL INTERACT WITH STEEP LAPSE RATES AND SUFFICIENT
INSTABILITY TO PRODUCE A DAMAGING WIND THREAT FROM WRN SD INTO N
CNTRL NEB.

THE UPPER SHORTWAVE TROUGH WILL TAKE MORE OF AN EWD DIRECTION ON
TUE/D5 AS IT MOVES ACROSS THE UPPER MS VALLEY. WITH STRONG VORTICITY
ALOFT...BANDS OF STORMS ARE LIKELY ALONG THE LEADING EDGE OF THE
VORTICITY MAX. HOWEVER...IT APPEARS THAT THE SURFACE MOIST AXIS WILL
BECOME NARROW...AND STRONG MIXING MAY OCCUR AS WELL. THE RESULT
COULD BE A SMALL WINDOW OF OPPORTUNITY FOR SEVERE STORMS. AT THIS
TIME...IT IS TOO UNCERTAIN TO INTRODUCE SUCH A SMALL AREA.

AS THIS TROUGH CONTINUES EWD ACROSS THE GREAT LAKES...A COLD FRONT
WILL TRAIL SWWD ACROSS THE OH VALLEY INTO THE MID MS VALLEY...WITH A
CONTINUED THREAT OF THUNDERSTORMS. ALTHOUGH SOME LOCALIZED SEVERE
MAY OCCUR IN THE FORM OF WIND AND HAIL...NO LARGE SCALE AREAS APPEAR
WARRANTED AT THIS TIME.

..JEWELL.. 03/23/2012

[trapperman]

At least for up here, someone wake me up in late April.

Next.

[andyhb]

[attachment=61121:day3otlk_0730.gif]

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0120 AM CDT SAT MAR 24 2012

VALID 261200Z - 271200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE BLACK HILLS NEWD INTO
NWRN MN...

...SYNOPSIS...
A POTENT SHORTWAVE TROUGH WILL MOVE FROM THE GREAT BASIN MON MORNING
INTO THE NRN HIGH PLAINS BY LATE AFTERNOON. AT THE SURFACE...LOW
PRESSURE WILL RAPIDLY DEEPEN FROM ERN MT INTO WRN SD/NEB. AN INTENSE
COLD FRONT WILL MATERIALIZE OVER WY AND CO...AFFECTING SD AND NEB
DURING THE EVENING WITH STRONGLY FORCED CONVECTION CAPABLE OF
DAMAGING WINDS.

...DAKOTAS INTO WRN MN...
ELEVATED THUNDERSTORMS MAY BE ONGOING OVER THE ERN DAKOTAS WITH A
CONDITIONAL THREAT OF LARGE HAIL DRIVEN BY WARM ADVECTION WITH THE
LOW LEVEL JET. THESE STORMS MAY CONTINUE THROUGH MIDDAY AS THEY
GRADUALLY SHIFT NWD ACROSS ND AND PERHAPS NWRN MN.

TO THE S...THE PLAINS WILL BE CAPPED MOST OF THE DAY. PRESSURES WILL
FALL RAPIDLY OVER NRN HIGH PLAINS AHEAD OF THE TROUGH...WITH
CONVERGENCE INTENSIFYING AS A COLD FRONT SURGES ACROSS WY AND CO.

SINCE THE FRONT WILL ARRIVE LATE...PEAK HEATING WILL HAVE BEEN
ACHIEVED AND VERY STEEP LOW TO MID LEVEL LAPSE RATES WILL BE IN
PLACE. DEWPOINTS MAY ONLY BE IN THE 40S TO LOWER 50S F...BUT CAPE
WILL BE NONZERO AND SHEAR WILL BE VERY STRONG. HIGH BASED CONVECTION
IS EXPECTED ALONG THE FRONT BEGINNING OVER WY...AND SPREADING
RAPIDLY NEWD ACROSS THE DAKOTAS. MODELS HAVE BEEN CONSISTENT IN
DEPICTING A RAPID AND STRONG WIND SHIFT WITH WLY 850 MB POST FRONTAL
FLOW IN EXCESS OF 60 KT. SO WHILE INSTABILITY WILL BE THE LIMITING
FACTOR...STRONG FORCING AND STEEP LAPSE RATES SHOULD COMPENSATE AND
DAMAGING WINDS ARE EXPECTED.

OTHER STORMS WILL PERSIST N OF THE WARM FRONT...FROM THE ERN DAKOTAS
INTO MN WITH A LARGE HAIL THREAT.

..JEWELL.. 03/24/2012

[Derek Heide]

Latest NAM (even GFS) are more north with the low pressure system on Monday/Tuesday. NAM actually has the low cutting a bit into southern Manitoba. That would give me a great show at elevated convection, especially Monday night and Tuesday morning.

Looking forward to this event. Regardless, we should get some much needed precip up here in southern MB. Fires have already been igniting in southeastern portions this past week.

[andyhb]

[attachment=61222:day1otlk_1200.gif]
[attachment=61223:day1probotlk_1200_torn.gif]

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1258 AM CDT MON MAR 26 2012

VALID 261200Z - 271200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE DAKOTAS
INTO NWRN MN...

...SYNOPSIS...
COMPACT SHORTWAVE TROUGH...CURRENTLY MOVING THROUGH SRN CA PER WATER
VAPOR IMAGERY...WILL REMAIN PROGRESSIVE THIS FORECAST PERIOD
TRACKING FROM THE GREAT BASIN TO ND BY 12Z TUESDAY. THIS TROUGH IS
EXPECTED TO EVOLVE INTO A RATHER POTENT SYSTEM AS IT REMAINS
NEGATIVELY-TITLED AND UNDERGOES DEEPENING MONDAY NIGHT INTO A CLOSED
LOW OVER ND. AT THE SURFACE...A LEE CYCLONE WILL DEEPEN OVER ERN MT
INTO THIS AFTERNOON AND THEN TRACK ENEWD ACROSS ND THIS
EVENING/OVERNIGHT. A COLD FRONT TRAILING SWD FROM THIS PRIMARY
SYNOPTIC LOW IS EXPECTED TO EMERGE INTO THE NRN HIGH PLAINS LATE
THIS AFTERNOON OR BY 27/00Z. THIS BOUNDARY WILL THEN ADVANCE
QUICKLY ENEWD ACROSS THE DAKOTAS AND NEB THROUGH 27/12Z.
MEANWHILE...A WARM FRONT WILL MOVE NWD ACROSS MUCH OF SD TODAY...AND
SHOULD EXTEND SEWD FROM ERN MT INTO SOUTH CENTRAL ND TO ERN SD AND
WRN IA BY LATE THIS AFTERNOON.

...NRN PLAINS TO NWRN MN...
A VERY STRONG EML/PLUME OF MIDLEVEL LAPSE RATES /7.5-9 C PER KM/
WILL CONTINUE TO SPREAD ENEWD ACROSS THE NRN AND CENTRAL PLAINS
TODAY...EFFECTIVELY CAPPING THE WARM SECTOR THROUGH THE AFTERNOON.
THE EXCEPTION MAY BE ALONG THE E/NERN EXTENT OF THE CAP...WHERE
STRONG LOW LEVEL WAA WITHIN THE NOSE OF STRENGTHENING SLY LLJ
EXTENDING INTO THE ERN DAKOTAS/WRN MN SUPPORTS ELEVATED TSTM
ACTIVITY THIS MORNING INTO THE AFTERNOON. EFFECTIVE BULK SHEAR TO
AROUND 40 KT AND MUCAPE TO AROUND 1000 J/KG SUGGEST THE STRONGER
ELEVATED STORMS WILL BE CAPABLE OF PRODUCING SEVERE HAIL.

THE FOCUS FOR LATE AFTERNOON/EARLY EVENING STRONG TO SEVERE STORM
INITIATION SHIFTS TO WRN SD AS STRONG FORCING FOR ASCENT/90-120
METER HEIGHT FALLS SPREAD INTO THE NRN HIGH PLAINS. THIS FORCING IS
EXPECTED TO BE SUFFICIENT FOR WEAKENING THE CAP/INHIBITION FOR THE
DEVELOPMENT OF HIGH BASED STORMS. MLCAPE UP TO 1000 J/KG OVER WRN
SD AND EFFECTIVE BULK SHEAR OF 35-50 KT WILL SUPPORT STORM
ORGANIZATION WITH SEVERE HAIL AND DAMAGING WINDS THE INITIAL PRIMARY
THREATS.

FORECAST SOUNDINGS SUGGEST PARCELS WILL TEND TO BE ROOTED ABOVE THE
SURFACE...OR MORE ELEVATED...WITH ENEWD EXTENT ACROSS CENTRAL/NERN
SD INTO SRN/ERN ND EARLY MONDAY EVENING WITH THE APPROACH OF THE
SURFACE LOW AND COLD FRONT. HOWEVER...THE STRONG FORCING FOR ASCENT
ALONG THE TRACK OF THE DEEPENING TROUGH MAY PROVE SUFFICIENT IN
OVERCOMING THE CAP SUCH THAT SURFACE BASED STORMS WILL BE POSSIBLE.
FOR THIS REASON...THE THREAT FOR DAMAGING WINDS HAS BEEN EXTENDED
FARTHER ENEWD THAN INDICATED BY THE PREVIOUS OUTLOOKS FOR THIS
REGION. IN ADDITION...A CONDITIONAL TORNADO THREAT WILL EXIST
ACROSS CENTRAL SD INTO SOUTH CENTRAL ND...WHERE THE 12Z ECMWF AND
00Z NAM SUGGEST A SUB-SYNOPTIC SURFACE LOW WILL TRACK FROM
SWRN-NORTH CENTRAL SD EARLY THIS EVENING. ENHANCED LOW LEVEL SHEAR
WITH THIS LOW AND RELATIVELY HIGHER SURFACE DEWPOINTS SUGGEST AN
ISOLATED TORNADO THREAT IS POSSIBLE...WITH SFC-1 KM SHEAR EXCEEDING
30 KT.

AN ELEVATED HAIL THREAT MAY PERSIST LATER MONDAY EVENING ACROSS
ERN/NERN ND AS STORMS BECOME MORE ELEVATED WITH NERN EXTENT.

[tornadotony]

I will be floored if there is a tornado today. Absolutely floored. I don't know what's more inhibitive, the cap or the sky-high cloud bases.

[Thundersnow12]

I will be floored if there is a tornado today. Absolutely floored. I don't know what's more inhibitive, the cap or the sky-high cloud bases.

Heck of an EML for March, H7 temps of 10 deg C in NE currently.

[Derek Heide]

I will be floored if there is a tornado today. Absolutely floored. I don't know what's more inhibitive, the cap or the sky-high cloud bases.

Yeah, far from a beauty of a set-up tornado-wise!

Pretty amazing pattern, though. I struggled to get above zero celsius yesterday. It felt like winter again. Now, I've got a threat of elevated storms tonight. Could be a decent lightning show in ND/MN this evening/overnight.

[Jim Marusak]

well, it looks like the low's jump is now progressing. the 21z sfc analysis i did here says the main low is starting to degrade in sheridan and the jump point just west of scottsbluff. the warm front is stretching from near DMO to near FSD to PIR. time to see what momma nature will whip up.

[OceanStWx]

Lots of DCAPE and steep mid level lapse rates, big time downdraft potential as updrafts help to mix down winds aloft along the cold front. A lot of 60 knot pixels down around 1000 feet near KUDX.

[OceanStWx]

Winds are already pretty strong in the CAA, but convective enhancement should get some nice gusts out of it. Custer and Chadron have both gusted over 50 knots already.

Nice isallobaric component too. SPC meso page is showing about a 5-6 mb rise/fall couplet for the last 2 hours.

[baroclinic_instability]

Winds are already pretty strong in the CAA, but convective enhancement should get some nice gusts out of it. Custer and Chadron have both gusted over 50 knots already.

Nice isallobaric component too. SPC meso page is showing about a 5-6 mb rise/fall couplet for the last 2 hours.

DMC indeed initiated across N Nebraska as expected, but activity looks marginal at best in terms of organization. Will be interesting to see if the buidling NBL can be penetrated by any gusts.

[Derek Heide]

Thought this would be interesting to you guys..

A nice cluster of thunderstorms developed and is persisting this evening north of the Riding Mountain National Park in Manitoba. Quite a bit of lightning being observed with the activity along with cloud tops around 40,000 feet in height.

That's the further north I've seen thunderstorms in March. Incredible.

Still hoping for some elevated convection here tonight. A decent cluster right now in SW ND with additional convection trying to organize east through Jamestown. SPC has extended the 15% hail contours up to the MB border.

[Jim Marusak]

some very nice t-storms up there indeed, looking at the ec radars. wonder what they're observing on hwy 6 between the lakes attm.

and the west end of bismarck/mandan area is getting clocked attm with minot next on the storm's list. wonder how those storms will get thru customs.

[Derek Heide]

Pretty amazing stuff. That area is in a snowfall warning. Expecting 10-15 cm of snow by tomorrow night.

I'm intrigued by the southern ND complex. The stuff east of the main cluster appears to be gradually strengthening. SPC Mesoanalysis shows favorable lapse rates moving up into southern MB and a good push of moisture above the surface.

[Jim Marusak]

in about 40 mins, you'll find out how much of a punch you'll get in pilot mound and killarney.

[OceanStWx]

Not sure if this is the best place for it (the date is right but the region is a little off in the title), so feel free to move this to the 3/29 thread if you think that is more appropriate.

Subtle disturbance is lifting north across Kansas right now. If you loop a visible satellite you can even see the cyclonic rotation of the low level clouds as they drift north.



Decent environment is setting up along I-70, as heating and moistening of the boundary layer takes place. This disturbance lifting north should only serve to enhance the convergence to its N/NE, right in the Salina vicinity. Very steep mid level lapse rates could produce some monster hail, but low level parameters are such that a tornado or two is entirely possible.