December 23-27th Storm System's/Severe Weather Potential

[Stebo]

ILN wrote a novel this morning... I won't post the whole thing but they brought up an interesting point 

 

 

The rest of it:

http://forecast.weather.gov/product.php?site=NWS&issuedby=ILN&product=AFD&format=CI&version=1&glossary=1&highlight=off

It might not reach ILN's CWA until after 09z so it makes sense for them to say that, this is more of a IL/IN S MI potential for this region.

[HillsdaleMIWeather]

Based on the model data, it looks like Southern MI is gonna have fun.

[OHweather]

It might not reach ILN's CWA until after 09z so it makes sense for them to say that, this is more of a IL/IN S MI potential for this region.

Some of the hi-res models do develop storms along a pre-frontal trough in the evening farther east into parts of OH/KY...although would rather have the cold front as I'm not sure forcing will support much convection ahead of the front. Shear will be plenty strong so if we can realize 500-1000 J/KG of MUCAPE maybe there will be enough instability to get a few storms farther east. I'm not confident but it's probably Ohio's best shot for severe out of this due to ILN's concern about the front weakening some as it moves farther east.

[Hoosier]

i think we'll see a tornado or two in LOT's cwa

 

 

I think the hail threat could be greater than we're used to at this time of year, especially if some of the higher instability progs pan out.  Freezing levels drop to around 8,000 feet tomorrow evening. 

[ClicheVortex2014]

It might not reach ILN's CWA until after 09z so it makes sense for them to say that, this is more of a IL/IN S MI potential for this region.

I dunno about 09z... looking at both NAMs and GFS VV, it should reach the CWA before or around 06z. Either way... not good timing.

[Stebo]

Some of the hi-res models do develop storms along a pre-frontal trough in the evening farther east into parts of OH/KY...although would rather have the cold front as I'm not sure forcing will support much convection ahead of the front. Shear will be plenty strong so if we can realize 500-1000 J/KG of MUCAPE maybe there will be enough instability to get a few storms farther east. I'm not confident but it's probably Ohio's best shot for severe out of this due to ILN's concern about the front weakening some as it moves farther east.

With the lower forcing along the pre-frontal trough the potential of isolated/scattered convection is good, so if they are discounting the potential along the pre-frontal trough that is a mistake.

[OHweather]

With the lower forcing along the pre-frontal trough the potential of isolated/scattered convection is good, so if they are discounting the potential along the pre-frontal trough that is a mistake.

It looks like they gave it a passing mention:

 

IF ADDITIONAL CONVECTION DEVELOPS OUT AHEAD OF THE FRONT IN THE WARM

SECTOR (IN THE EARLY EVENING)...THE STRONG SHEAR WILL LEAD TO AT

LEAST SOME POTENTIAL FOR STRONG TO SEVERE STORMS AT THAT TIME AS

WELL.

 

With weaker forcing with the pre-frontal trough we'd need more instability to get updrafts that aren't apart by all of the shear that will be in place, which is my main concern. If some of the hi-res models showing up to 1000 J/KG of MUCAPE verify that may be enough instability, so we'll see. I'm again not confident but any convection would probably be discrete along the pre-frontal trough as you said so it could be interesting. I'll give it a 1/4 chance of actually occurring though.

[Hoosier]

All December tornadoes...no surprise here, the map is loaded south of us

 

 

 

 

 

Checked this again and noticed that Michigan hasn't recorded a tornado in December.  Does the streak come to an end tomorrow? 

[Stebo]

Checked this again and noticed that Michigan hasn't recorded a tornado in December.  Does the streak come to an end tomorrow? 

We did just break a streak of never having a tornado between the hours of 6-8am this year in November no less. So anything is certainly possible.

[ClicheVortex2014]

It looks like they gave it a passing mention:

 

With weaker forcing with the pre-frontal trough we'd need more instability to get updrafts that aren't apart by all of the shear that will be in place, which is my main concern. If some of the hi-res models showing up to 1000 J/KG of MUCAPE verify that may be enough instability, so we'll see. I'm again not confident but any convection would probably be discrete along the pre-frontal trough as you said so it could be interesting. I'll give it a 1/4 chance of actually occurring though.

If the pre-frontal activity is my best shot, I'll gladly take the gamble. Could be nasty if something like 4km NAM verifies... but it's not really the most reliable model 

[Hoosier]

We did just break a streak of never having a tornado between the hours of 6-8am this year in November no less. So anything is certainly possible.

 

 

Expanding out to include DJF, there's been a grand total of 2 tornadoes in Michigan in those months (one in January, one in February).  Certainly up against it in terms of climo but if climo always won, we wouldn't have outliers. 

[Hoosier]

We did just break a streak of never having a tornado between the hours of 6-8am this year in November no less. So anything is certainly possible.

 

 

Did you see the 12z ECMWF has a pocket of CAPE ~1000 in southern MI at 3z Thursday.

[Stebo]

Did you see the 12z ECMWF has a pocket of CAPE ~1000 in southern MI at 3z Thursday.

Yes I did, incredible stuff to say the least. I work until midnight tomorrow night so if anything is close by after work I'll be able to chase. Of course things could come to me as well.

[ilstormchaser]

SPC is def underestimating things a lot. It should be a moderate risk for dixie ally and borderline enhanced risk as far North as Central IL. I just put in for a day off work for chasing tomorrow as I might as well make it the last day for me at work this week. Hopefully the local offices will be more bullish about the setup and mention the risks in their HWO to let the public know especially considering severe weather is not on a lot of peoples mind this time of year.

[Superstorm93]

NSSL-WRF

 

Moves a bunch of junk through at 15z, but clearing occurs and cells are able to fire over IL in some pretty decent parameters for a late season event 

 

[on_wx]

Checked this again and noticed that Michigan hasn't recorded a tornado in December. Does the streak come to an end tomorrow?

FWIW Ontario's lone December tornado occurred at 630pm December 12, 1946 touched down near Exeter (north of london) and was on the ground for 52 km moving northeast. Up to 1.2km in width and ec estimates it was an F2

[PGM]

SPC is def underestimating things a lot. It should be a moderate risk for dixie ally and borderline enhanced risk as far North as Central IL. I just put in for a day off work for chasing tomorrow as I might as well make it the last day for me at work this week. Hopefully the local offices will be more bullish about the setup and mention the risks in their HWO to let the public know especially considering severe weather is not on a lot of peoples mind this time of year.

Agreed. 4k nam is pretty crazy. The SPC is lowballing on their outlooks... I'm glad they upgraded to enhanced today though.

[CoachLB]

Torcon outlook.

[ClicheVortex2014]

WRF-NMM has some good activity ahead of the front... even has a cell over SW OH by 20z. 

 

[HillsdaleMIWeather]

I definitely feel the SPC is underestimating the threat further north, all of the models have been coming in stronger, including the radar simulations.

[Hoosier]

I think we'll see a northward expansion in the risk categories if the 00z models don't back off.  I'd probably go with a slight risk into the rest of northeast IL/northern IN/southern MI as the GFS is really the only holdout with crappy instability and we know how that usually goes. 

[Hoosier]

El Oh Tee afternoon disco

 

SEVERE WEATHER THREAT...WE ARE LOOKING AT A LOW CAPE/HIGH SHEAR  ENVIRONMENT CAPABLE OF PRODUCING DAMAGING WINDS AND POSSIBLY  TORNADOES. CIPS ANALOG EVENTS SUPPORT THIS OUTLOOK WITH THE BEST  SYNOPTIC MATCHES ALSO FEATURING MOSTLY DAMAGING WIND REPORTS WITH A  FEW ISOLATED TORNADO REPORTS.     DEWPOINTS CLIMB INTO THE UPPER 50S TO LOW 60S WEDNESDAY. CAPE VALUES  INCREASE ACROSS THE REGION THROUGH THE AFTERNOON WITH MAX VALUES OF  250-500 J/KG DEPENDING ON WHAT MODEL YOU LOOK AT. THE NAM FEATURES  THE HIGHEST CAPE VALUES AS IT TYPICALLY DOES. THE MORE IMPRESSIVE  CAPE VALUES ARE SOUTH OF I-80 WHERE THE PRIMARY SEVERE WEATHER  THREAT WILL BE. 6KM BULK SHEAR VALUES ARE AROUND 60 KT AND 1KM BULK  SHEAR VALUES ARE 30-50 KT ACROSS THE CWA. WINDS 1800 FT AGL WILL BE  AROUND 50 KT SO GUSTY WINDS ARE EXPECTED OUTSIDE OF ANY STORMS. SOME  MODELS FEATURE EVEN FURTHER BACKED SURFACE WINDS WHICH WOULD  INCREASE THE LOW LEVEL SHEAR AND LEAD TO A GREATER CHANCE OF  TORNADOES.      EXPECTING THUNDERSTORM ACTIVITY TO INCREASE IN THE AFTERNOON WITH A  CHANCE OF SEVERE STORMS BETWEEN 2PM-8PM CST ESPECIALLY SOUTH OF I-  80.  THE POTENTIAL EXISTS FOR THE SEVERE WEATHER THREAT SHIFT A BIT  FURTHER NORTH OVER THE NEXT 24 HOURS AS WELL.  THE SCATTERED STORMS  WILL EVOLVE INTO BOWING SEGMENTS OR A SQUALL LINE AS THE COLD FRONT  SWINGS THROUGH IN THE LATE AFTERNOON/EVENING.  THE LINE OF STORMS  WOULD THEN CONTINUE EAST MAINLY PRODUCING DAMAGING WINDS.  

[ClicheVortex2014]

IND

 

FOCUS THEN SHIFTS TO WEDNESDAY AND WEDNESDAY EVENING ACROSS THE
AREA. STRONG LOW PRESSURE WILL DEVELOP OVER THE CENTRAL PLAINS AND
PUSH NORTHEAST ACROSS THE GREAT LAKES. VERY STRONG DYNAMICS WILL BE
IN PLACE ACROSS THE AREA WITH A 50 TO 60 KT SOUTH SOUTHWESTERLY LOW
LEVEL JET AND A STRENGTHENING CYCLONIC UPPER LEVEL JET. FORECAST
SOUNDINGS AND MODEL INSTABILITY INDICES INDICATE MORE THAN ADEQUATE
INSTABILITY PROFILES FOR THE TIME OF YEAR. EVEN WITH SOME CORRECTION
FOR THE TENDENCY OF MODELS TO BE TOO AGGRESSIVE ON POLEWARD MOISTURE
TRANSPORT...SHOULD STILL BE SUFFICIENT INSTABILITY FOR THUNDER
ACROSS THE AREA...AND GIVEN THE VERY STRONG DEEP LAYER SHEAR AND
GOOD LOW LEVEL HODOGRAPHS...ALL SEVERE THREATS WILL BE ON THE TABLE
ACROSS CENTRAL INDIANA.

BULLSEYE OF MAXIMUM SEVERE THREAT WILL BE SOUTH OF THE AREA...AS
WELL DESCRIBED IN SPC DAY 2 OUTLOOK...BUT AN AMPLE SEVERE THREAT
WILL EXIST ACROSS CENTRAL INDIANA WEDNESDAY AFTERNOON AND EVENING.

 

 

I can see enhanced reaching up to Indianapolis tomorrow

[Hoosier]

IND

 

I can see enhanced reaching up to Indianapolis tomorrow

 

 

At least.  I could envision I-80 if the higher instability pans out. 

[kperk014]

Hey forumers

 

I live in northwest Alabama and I see Dr Forbes has us with a Torcon of 7 for Wednesday (what is it about Wednesdays?!). Every time really severe weather hits, I lose electricity and cable for days. As with the 4/27/2011 outbreak, I was in the dark about what happened until May 1st when I was able to access this board and catch up. You guys were amazing! If we get it again, I hope I can depend on your intelligence and diligence once again. Have a good day!

[Hoosier]

Substantial increase in CAPE on the 18z NAM.  Closer to what the 4km has been advertising.

 

 

[snowlover2]

New ILN AFD

 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON OH
328 PM EST TUE DEC 22 2015

.SYNOPSIS...
SHOWERS AND POSSIBLY A FEW STORMS WILL SPREAD BACK INTO THE OHIO
VALLEY LATER TONIGHT...AHEAD OF A STRONG WEATHER SYSTEM SHIFTING
THROUGH THE MISSISSIPPI VALLEY AND GREAT LAKES ON WEDNESDAY AND
WEDNESDAY NIGHT. THIS SYSTEM WILL CONTINUE THE LIKELIHOOD OF
SHOWERS AND A FEW STORMS THROUGH WEDNESDAY NIGHT...AS WELL AS NEAR
RECORD TO RECORD TEMPERATURES. CHRISTMAS EVE DAY WILL BRIEFLY DRY
OUT FOR MUCH OF THE AREA...BEFORE MORE RAIN REDEVELOPS ACROSS THE
AREA CHRISTMAS DAY AND INTO THE UPCOMING WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS WAS DETAILED VERY NICELY IN AFD ISSUED BY OVERNIGHT SHIFT...THE
WINDOW OF DRYING THIS AFTERNOON VIA WEAK BUBBLE HIGH PRESSURE AND
SUBSIDENCE IN WAKE OF LAST NIGHT/S RAIN-MAKER IS SLOWLY CLOSING.
GOES WATER VAPOR LOOPS LATE THIS AFTERNOON INDICATE A SHORTWAVE
TROUGH AND ASSOCIATED PV ANOMALY OVER LOUISIANA...EJECTING
NORTHEAST UP THE WRN SIDE OF MASSIVE WRN ATLANTIC MID/UPPER LEVEL
ANTICYCLONE. SFC BAROCLINIC ZONE TIED TO LAST NIGHT/S WAVE HAS
FRONTOLYSIZED /WASHED OUT/ OVER THE FORECAST AREA WITH TEMPS IN
THE MID 40S IN WCNTL OHIO WITH WESTERLY FLOW...AND LOWER 60S OVER
NRN KY WITH SOUTHERLY FLOW. AS THE LOUISIANA WAVE EJECTS TOWARD
THE AREA THIS EVENING...SOUTHERLY FLOW WILL INCREASE AND PUSH
WARMER AIR QUICKLY NORTHWARD TONIGHT...SO WE EXPECT STEADY TEMPS
IN THE SOUTH AND QUICKLY RISING TEMPS IN THE NORTHERN AREAS. IN
ADDITION...CLOUDS WILL INCREASE/THICKEN AND ENOUGH
FORCING/VERTICAL MOTION TIED TO THE WAVE WILL AGITATE MOISTURE-
LADEN AIRMASS TO PRODUCE EXPANDING AREA OF SHOWERS ESP AFTER 06Z
AND TOWARD 12Z ACROSS MUCH OF THE FORECAST AREA. WHILE THE FORCING
IS CENTERED QUITE HIGH UP...A 30KT LLJ WILL ISENTROPICALLY LIFT
PARCELS TO THE LFC WHERE SEVERAL HUNDRED JOULES OF ELEVATED CAPE
WILL EXIST WITHIN A SEMI-DRY LAYER ABOVE THE MOIST BOUNDARY
LAYER...THUS EXPECT A FEW STORMS SIMILAR TO LAST NIGHT. IN
FACT...SOME FCST SOUNDINGS ARE ROBUST WITH THE ELEVATED
INSTBY...AND THUS CAN/T RULE OUT A SMALL HAILSTONE OR TWO WITH THE
MOST VIGOROUS UPDRAFTS LATER TONIGHT OVER NRN KY/SCNTL OH.
MAINTAINED RAIN CHANCES AS INHERITED...WITH TWEAKS TO
TIMING/COVERAGE PER LATEST CONVECTIVE ALLOWING GUIDANCE.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
WE/VE BEEN WATCHING THE WED/WED NIGHT TIMEFRAME FOR MANY DAYS NOW
GIVEN THE PATTERN/ANALOGS /CIPS/ THAT HAD SO NICELY HIGHLIGHTED
POTENTIAL IMPACTS AND WHAT THIS PATTERN COULD PRODUCE DAYS AGO.
UNFORTUNATELY...DETAILS FROM THE 22.12Z SUITE OF EXPLICIT AND
PARAMETERIZED CONVECTION MODELS FAILED TO CLEAR OR IMPROVE ON
UNCERTAINTIES THAT WERE INHERITED WITH TODAYS PACKAGE. REFERENCE
THE OVERNIGHT AFD FROM WFO ILN FOR AN EXCELLENT SUMMATION OF
ONGOING CONCERNS REGARDING STORM COVERAGE/INTENSITY.

GOES WATER VAPOR THIS AFTERNOON SHOWS TWO PRIMARY FEATURES OF
INTEREST BEYOND THE LOUISIANA WAVE THAT WILL IMPACT LATER TONIGHT
AND WED MORNING...

1) SHORTWAVE ENERGY MIGRATING SLOWLY THROUGH THE
DAKOTAS AND
2) MORE SUBTLE SHORTWAVE ENERGY SHIFTING THROUGH NEW MEXICO.

THE LATTER EXISTS WITHIN THE BASAL PORTION OF THE LONGWAVE TROUGH
WHICH HAS STEADILY ALBEIT SLOWLY BEEN ADVANCING EAST THIS WEEK. ON
WEDNESDAY...AS THE LOUISIANA BASED WAVE EJECTS AWAY FROM THE
AREA...TAKING THE SCT SHRA/STORM THREAT WITH IT...A GENERAL LULL
IN PCPN WILL BE SEEN ACROSS THE WFO ILN FORECAST AREA.
HOWEVER...TO OUR WEST/SOUTHWEST...THE TWO SHORTWAVES WILL SLOWLY
BEGIN A PHASING/ACCELERATION WITHIN THE LONGWAVE TROUGH...WITH THE
NEW MEXICO-BASED WAVE DEEPENING AND SHIFTING QUICKLY NORTHEAST TO
SOMEWHAT /DEGREE YET UNKNOWN/ PHASE WITH THE SHORTWAVE ENERGY
PASSING THRU THE DAKOTAS INTO MN. THE RESULT OF THIS WILL BE A
RAPIDLY DEEPENING SFC LOW RUNNING FROM KS TO IOWA INTO WI AND
ONTARIO WEDNESDAY/WED NIGHT.

SO...WE/RE DOWN TO THE PERIODS OF INTEREST...LATER WED AFTN AND
WED NIGHT. AS MENTIONED ABOVE...DETAILS OF IMPACTFUL WEATHER STILL
UNCLEAR. WHAT REMAINS CERTAIN IS THIS...

1) ANOMALOUS /LIKELY RECORD BREAKING/ WARMTH STILL IN PLACE OVER
OHIO VALLEY AHEAD OF THE WAVE
2) ANOMALOUS MOISTURE PLUME STILL IN PLACE OVER OHIO VALLEY AHEAD
OF THE WAVE WITH PWAT EXPECTED TO BE 1.30 TO 1.50".
3) VERY STRONG LOW/MID LEVEL FLOW WITH SOME DIRECTIONAL SHEAR
FROM BOUNDARY LAYER THROUGH THE LOWER TROPOSPHERE AS THE LOW
DEEPENS AND SHIFTS NORTHEAST INTO CANADA.
4) STRONGEST DPVA AND LARGE SCALE FORCING WILL ONLY GLANCE THE
FORECAST AREA...WITH STRONGEST PV ADVECTION AND JET DYNAMICS
FOCUSING WEST/NORTHWEST OF ILN CWA. IN FACT...AFTER VERY MINOR
HEIGHT FALLS WED AFTN IN WRN OHIO...MID/UPPER HEIGHTS ACTUALLY
RISE QUITE A BIT AFTER 00Z WHICH TYPICALLY ISN/T PRESENT IN
ORGANIZED COOL SEASON SVR EVENTS
5) A PRETTY CLEAR SIGNAL THAT (BECAUSE OF #4) SURFACE FRONT WILL
BE WEAKENING AND SLOWING DOWN AS IT APPROACHES THE ILN CWA AFTER
MIDNIGHT WED NIGHT...WITH ONLY MODEST/WEAK CAA JUST GETTING INTO
WRN AREAS.

SO THAT SETS UP A PRETTY POLARIZED CAMP OF PROS/CONS FOR SEVERE
WEATHER. HARD NOT TO ACKNOWLEDGE THE SHEAR AND INSTBY IN PLACE AS
REGION IS GLANCED BY UPPER LEVEL FORCING WED AFTN/EVE...AND AHEAD
OF WEAK FRONT AS IT SPREADS SLOWLY IN WED NIGHT...BUT THINGS
CERTAINLY NOT LOOKING AS CONCERNING AS FARTHER WEST/SOUTHWEST
EITHER. IN ADDITION...TRIED AND TRUSTED HI-RES CAMS LIKE ARW-WRF
AND NSSL-WRF SHOWING TWO AREAS OF LIKELY FOCUS...AN INITIAL BAND
OF WEAKENING SHOWERS/STORMS FALLING APART WED AFTN/EVE AS IT
ENTERS THE FCST AREA /FOCUS ON WCNTL OH/...AND A MORE INTENSE BAND
DEVELOPING OVER KY/TN AND SPREADING RAPIDLY NORTHEAST OVER NRN
KY/SRN OHIO AFTER DARK. THE FORCING AT THIS TIME FINDS LOW LEVEL
SHEAR VECTORS NEARLY PARALLEL THE FORCING...AND WELL AHEAD OF THE
FRONT...SO IT BECOMES UNCLEAR IF WE/LL BE DEALING WITH QLCS/SQUALL
LINE WIND THREATS /INCLUDING A BRIEF/WEAK TORNADO THREAT/...OR
JUST A BAND OF ENHANCED CONVECTIVE RAINS. THIS WILL LIKELY REMAIN
UNCERTAIN UNTIL LATER IN THE DAY WEDNESDAY TO SEE SPATIAL OVERLAP
OF CAPE/SHEAR AND TIMING/IMPACT OF SHORTWAVE ENERGY. ALL THIS
BEING SAID...WE/RE STILL FOCUSED ON A 6 PM TO 3 AM WINDOW OF LOW-
END SEVERE WEATHER POTENTIAL...WITH ANCILLARY THREATS OF LOCALIZED
RUNOFF ISSUES SHOULD CONVECTIVE RATES DEVELOP.

 

[A-L-E-K]

always good to be ticking up at the last minute

[Central Illinois]

ILX

The calendar may say it is nearly Christmas, but we have the potential for severe thunderstorms to affect the area Wednesday afternoon and evening.

Locations Affected: Everywhere east of the Illinois River

Main Period of Concern: 2 pm to 6 pm west of I-55, 4 pm to 8 pm east of I-55

Threats: Damaging wind gusts in excess of 60 mph are the main concern, as well as large hail. Any tornadoes will be more isolated in nature.

An unseasonably warm and moist airmass will stream northward into Illinois ahead of an approaching storm system, with near-record high temperatures reaching the middle 60s and surface dewpoints climbing well into the 50s. This will produce unusually strong instability for this time of year. In addition, low-level wind shear (change of wind direction and speed) will increase markedly, particularly along/south of I-70. As low pressure tracks from northeast Kansas to northern Wisconisn on Wednesday, it will pull a cold front into central Illinois during the afternoon and evening. Several lines of thunderstorms will likely develop ahead/along the front, with the main severe weather threats being damaging wind gusts and large hail. An isolated tornado will also be possible, especially across southeast Illinois.

[Chambana]

always good to be ticking up at the last minute

Ain't that a fact jack. Gotta love when things trend stronger as the event draws closer, the potential is real.