September 9th-10th Severe Threat

[snowlover2]

I know that I'm not trusting the NAM...yet. It's been kinda on it's own so far.

Wish i had a nickel for everytime i see this phrase posted especially during the winter.

[snowlover2]

New day 2

 

 

 

DAY 2 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK  
1210 PM CDT MON SEP 08 2014  
 
VALID 091200Z - 101200Z  
 
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE CENTRAL PLAINS TO THE  
UPPER MS VALLEY...  
   
..SUMMARY  
 
SEVERE STORMS ARE EXPECTED LATE TUESDAY AFTERNOON INTO TUESDAY NIGHT  
ACROSS PARTS OF THE CENTRAL PLAINS AND MID MISSOURI VALLEY  
REGION...NORTHEASTWARD INTO THE UPPER MIDWEST. THESE STORMS WILL BE  
ACCOMPANIED BY THE RISK FOR SWATHS OF DAMAGING WIND GUSTS...A FEW  
TORNADOES...AND PERHAPS LARGE HAIL.  
   
..CENTRAL PLAINS TO UPPER MS VALLEY  
 
LATEST SHORT-RANGE MODEL GUIDANCE SUGGESTS WELL DEFINED SHORT-WAVE  
TROUGH OFF THE NRN CA COAST WILL DEAMPLIFY AND EJECT INLAND ACROSS  
THE GREAT BASIN TO A POSITION FROM SRN WY INTO ERN UT BY 10/00Z.  
HEIGHTS SHOULD THEN FALL ACROSS THE NRN/CNTRL PLAINS DURING THE  
LATTER HALF OF THE PERIOD AS A BELT OF MODEST 500 MB FLOW...ON THE  
ORDER OF 40KT...SPREADS ACROSS THE CNTRL HIGH PLAINS INTO THE MID MO  
VALLEY. THIS FEATURE SHOULD INDUCE LEE CYCLOGENESIS OVER SWRN  
NEB/NWRN KS BY LATE AFTERNOON WHICH SHOULD INCREASE LOW LEVEL  
CONVERGENCE NECESSARY FOR SFC-BASED CONVECTION DOWNSTREAM WITHIN  
INCREASINGLY SHEARED ENVIRONMENT.  
 
EARLY IN THE PERIOD WEAK ELEVATED CONVECTION MAY BE ONGOING WITHIN  
WARM ADVECTION ZONE ACROSS IA/MO. OTHER ISOLATED ELEVATED STORMS  
MAY BE NOTED ALONG THE NOSE OF HIGH PLAINS LLJ ACROSS THE CNTRL  
PLAINS. THIS EARLY ACTIVITY IS NOT EXPECTED TO BE PARTICULARLY  
INTENSE...THOUGH ROBUST UPDRAFTS COULD GENERATE MARGINALLY SEVERE  
HAIL. MORE SIGNIFICANT CONVECTION IS EXPECTED TO EVOLVE DURING THE  
AFTERNOON AHEAD OF AFOREMENTIONED LEE CYCLONE AS TEMPERATURES WARM  
INTO THE LOWER 90S ACROSS KS...JUST SOUTH OF SHARPENING WARM FRONT.  
CONVECTIVE TEMPERATURES SHOULD BE BREACHED BY 21Z AND SCT HIGH-BASED  
TSTMS ARE EXPECTED TO EVOLVE WITHIN VEERED BUT CONVERGENT LOW LEVEL  
FLOW OVER KS. THIS ACTIVITY SHOULD SPREAD/DEVELOP INTO THE WARM  
FRONTAL ZONE OVER SRN NEB WHERE NUMEROUS THUNDERSTORMS ARE EXPECTED  
FROM LATE AFTERNOON INTO THE EVENING HOURS. DEEP VEERING WITH  
HEIGHT AND INCREASING VERTICAL SHEAR SUPPORT ORGANIZED UPDRAFTS.  
INITIAL DISCRETE STRUCTURES SHOULD OBTAIN SUPERCELL  
CHARACTERISTICS...BUT UPWARD GROWTH AND STORM MERGERS SHOULD RESULT  
IN ONE OR MORE MCS-TYPE CLUSTERS ALONG NOSE OF LLJ ACROSS THE MID MO  
VALLEY AFTER DARK. AN EXPANDING CORRIDOR OF CONVECTION SHOULD  
EXTEND ACROSS ERN NEB...ACROSS WRN/CNTRL IA INTO SRN MN IMMEDIATELY  
AHEAD OF EJECTING SFC CYCLONE. FORECAST SHEAR PROFILES SUGGEST A  
FEW TORNADOES MAY BE NOTED WITH SUPERCELLS...THOUGH DAMAGING WIND  
COULD ULTIMATELY BE THE GREATEST THREAT IF ORGANIZED SQUALL LINE  
EVOLVES. LARGE HAIL MAY ALSO BE NOTED BUT WARMING TEMPERATURES  
ALOFT WILL SUPPRESS LAPSE RATES SOMEWHAT.  
 
..DARROW.. 09/08/2014 

[A-L-E-K]

LOT hitting on the heavy rain in the latest disco...going to be super efficient rain producer

 

noice

 

THE NET EFFECT OF THIS EVOLUTION WILL BE TO SLOW THE
PROGRESSION OF THE SRN END OF THE FRONT...WITH EXTENSIVE TRAINING OF
THUNDERSTORMS IN THE DEEPER LEVEL SWLY FLOW ALOFT.  WITH THE LATEST
FORECAST UPDATE...WILL CARRY AROUND 2 INCHES OF STORM TOTAL
WIDESPREAD QPF WITH THE SYSTEM FROM LATE TUESDAY NIGHT INTO EARLY
WEDNESDAY EVENING.  HOWEVER...WITH TRAINING THUNDERSTORMS LIKELY
ALONG WITH A VERY MOIST AIRMASS...THE 2 INCH AMOUNTS MAY BE A
CONSERVATIVE AREAL AVERAGE AMOUNT AS LOCALIZED TRAINING AND STRONG
TO POTENTIALLY SEVERE THUNDERSTORMS WILL BE VERY EFFICIENT PCPN
PRODUCERS.  THE PERIOD OF TIME WHICH THE HEAVIEST RAINFALL IS
EXPECTED WILL BE FROM LATE MORNING THROUGH LATE AFTERNOON WEDNESDAY
AS THE LEADING EDGE OF A 50KT+ LOW LEVEL JET POINTS INTO NRN IL/SERN
WI AND THEN SLOWLY TRANSLATES INTO NWRN INDIANA. 

[Hoosier]

18z is gonna be another run where the NAM is relatively jacked up it would appear. 

[Thunder Road]

Through the 18z runs, the GFS is still farther south with the CAPE gradient than the NAM.  Fwiw, the RGEM is somewhere in the middle, but closer to the NAM.

 

Basic climatology tells us to be skeptical of the northern extent of destabliziation in a cool-season event like this, so let's see.

[daddylonglegs]

wet...more lawn mowing

 

.RESULTING IN VERY STRONG MOISTURE
TRANSPORT ACROSS IOWA INTO SOUTHERN WISCONSIN. STRONG LIFT
ASSOCIATED WITH THIS LOW-LEVEL JET WILL RESULT IN WIDESPREAD
SHOWERS AND THUNDERSTORMS WITH RAINFALL RATES LIKELY EXCEEDING AN
INCH PER HOUR. WIDESPREAD ACCUMULATIONS FROM 1.5 TO 3 INCHES ARE
LIKELY WITH ISOLATED POCKETS UP TO 5 INCHES. FLASH FLOODING AND
RIVER FLOODING WILL BE A CONCERN...BUT WILL ALLOW FOR ONE MORE
MODEL CYCLE TO DETERMINE WHEN/WHERE WATCH HEADLINES MAY BE
NECESSARY. SEE HYDROLOGY DISCUSSION FOR MORE INFORMATION.

[Stebo]

Through the 18z runs, the GFS is still farther south with the CAPE gradient than the NAM.  Fwiw, the RGEM is somewhere in the middle, but closer to the NAM.

 

Basic climatology tells us to be skeptical of the northern extent of destabliziation in a cool-season event like this, so let's see.

I wouldn't really consider this a cool season event, since it is September. I mean the setup is similar to something we'd see later in the year but it isn't a cool season event.

[Hoosier]

I wouldn't really consider this a cool season event, since it is September. I mean the setup is similar to something we'd see later in the year but it isn't a cool season event.

 

 

It sorta seems like a hybrid.  We may end up with cool season type instability values but the airmass is more summerlike.

[Thunder Road]

True, the moisture is not November-like.  But surface pressures approaching or dropping below 988 mb (and flirting with the record low MSLP value for the month of September for much of its track), and the associated low/mid level winds fields, are not August or September-like either, so I guess hybrid is the way to go.

[A-L-E-K]

liking chances for re-initiation right overhead on Wed more than i was earlier

 

early day heavy rain event still on track

[IWXwx]

Even with the crappy lapse rates and the possibility of lack of instability developing, shear alone should produce storms that lead to numerous wind damage reports on Wednesday.

 

I know that the odds are stacked against the big dog, but hey, it still should be pretty decent for September.

[cyclone77]

Not expecting any severe for the QCA as tomorrow night's storms will be more heavy rain producers by the time they reach the area late in the night.  Wed the action probably fires off just east.  Typical of a big synoptic event for this area it seems.  Still expecting some decent rains over the next 36hrs or so.

[hm8]

SREF CAPE probs (ignore the date at the top, it appears like its one day off)

 

>500 j/kg

 

 >1000 j/kg

 

 

DTW plume

 

[Stebo]

If we can get into the 1000 J/kg range we would be in a good position for some severe weather, even the mean though isn't too bad.

[Thundersnow12]

NAM coming in even stronger...992mb at 9z Weds in nrn IA

[Quincy]

12z Euro had an area of 500-1000 J/kg SBCAPE from northern Indiana into southwestern lower Michigan. Have to wonder if any meaningful instability will reach north of the IN/MI border.

Edit: Climo has a mean MLCAPE value of 523 J/kg for tornado cases in the area mentioned above.

[TimChgo9]

Locally, (meaning IMBY) the rain potential has got some of the neighbors in a bit of an uproar, if the 2 inches of rain materializes.  The area just south of me, from about 47th St to 55th St and farther south, from Brainard Ave. east to LaGrange Rd flooded rather bad during the last heavy rain a couple of weeks ago.  The heavy rain caused sewage back ups and houses to flood that had never flooded before with up to a foot of water and slop.  There was a board meeting here in town a couple of weeks ago, the flooded out residents were demanding the village do something.  It all stems from the fact that the Country Club down the street had made some changes over the last couple of years that causes the run off from heavy rain to head through the neighborhoods to the east.  This last rain, however, was the worst, and it has even caused some of the folks who live there to tear down their garages due to water and flood damage.  Back yards and basements were flooded with a foot of water or more in many places. 

 

Looking like Wednesday is going to be interesting around here.  I live north of the affected area, but it is still a cause for concern. 

[andyhb]

NAM coming in even stronger...992mb at 9z Weds in nrn IA

 

Wind profiles are really nasty through IN especially at 18-21z.

 

Near Ft. Wayne @ 21z using MLCAPE:

 

[Stebo]

NAM coming in even stronger...992mb at 9z Weds in nrn IA

Yeah brings MLCAPE over 1000 well into MI.

[Powerball]

If we can get temps to around 80*F or greater in the warm sector, that would definitely help to lock in the severe weather risk...

 

Even with the cloud cover, it won't take much to get there with a few peeks of sunshine and the deep southerly flow of warmer air aloft...

[Stebo]

If we can get temps to around 80*F or greater in the warm sector, that would definitely help to lock in the severe weather risk...

FWIW DTX is going for a high of 81 for Detroit.

[Powerball]

DTX's sounding on the NAM has an impressively long and curved hodograph during the late afternoon/early evening hours on Wednesday...

[Thundersnow12]

Will be interesting to watch the heating trends on Weds. NAM wants to get 80's up to southeast WI with the max heating/thermal axis right along the front before having temps crash into the 50's six hours later. 

 

A little more SBCAPE and who knows. 

[Stebo]

GFS barely gets us to 70 and has most of the southern part of the state 65-70, needless to say I think the surface thermodynamic profile of the GFS is wrong.

[Hoosier]

[tornadotony]

I just don't buy it.  Color me unimpressed.  I've bitten on too many setups like this in the past with initial convection in IA/NE the day before and what LOOKS like a substantial threat for the lower Lakes on day 2.  But what invariably happens is the first complex moves through in the morning, veers out the flow, significantly hampers low-level forcing, the mid-levels warm, and presto chango severo busto.  You can already see signs of this in the 00z NAM with flow veering significantly right off the deck.  Think 4/10/11 and 4/15/12.

[Hoosier]

dprog/dt of the GFS shows that it has been trending toward bringing better instability farther north. 

[Hoosier]

I just don't buy it.  Color me unimpressed.  I've bitten on too many setups like this in the past with initial convection in IA/NE the day before and what LOOKS like a substantial threat for the lower Lakes on day 2.  But what invariably happens is the first complex moves through in the morning, veers out the flow, significantly hampers low-level forcing, the mid-levels warm, and presto chango severo busto.  You can already see signs of this in the 00z NAM with flow veering significantly right off the deck.  Think 4/10/11 and 4/15/12.

 

 

Gives me pause when you're not excited as you often seem to lean on the bullish side (not a knock). 

[tornadotony]

dprog/dt of the GFS shows that it has been trending toward bringing better instability farther north. 

If the forcing goes down the crapper with poor lapse rates aloft, it probably won't be enough.

[Hoosier]

DAY 2 CONVECTIVE OUTLOOK    NWS STORM PREDICTION CENTER NORMAN OK  1236 AM CDT TUE SEP 09 2014    VALID 101200Z - 111200Z    ...THERE IS A SLGT RISK OF SVR TSTMS WEDNESDAY ACROSS SOUTHERN  PORTIONS OF THE GREAT LAKES REGION INTO THE MIDDLE MISSISSIPPI AND  LOWER OHIO VALLEYS...     ..SUMMARY    SEVERE STORMS ARE POSSIBLE WEDNESDAY ACROSS SOUTHERN PORTIONS OF THE  GREAT LAKES REGION INTO PARTS OF THE MIDDLE MISSISSIPPI AND LOWER  OHIO VALLEYS.  THIS WILL BE ACCOMPANIED BY THE RISK FOR DAMAGING  WIND GUSTS...POSSIBLY A COUPLE OF TORNADOES...AND COULD IMPACT THE  CHICAGO...DETROIT...INDIANAPOLIS AND CLEVELAND METROPOLITAN AREAS BY  WEDNESDAY EVENING.     ..SYNOPSIS    A BELT OF STRONG CYCLONIC FLOW WITHIN THE POLAR WESTERLIES APPEARS  LIKELY TO DIG ACROSS THE NORTHERN ROCKIES INTO THE NORTHERN PLAINS  DURING THIS PERIOD...AROUND THE SOUTHERN PERIPHERY OF AN ELONGATED  LOW/POSITIVELY TILTED TROUGHING PROGRESSING ACROSS THE INTERNATIONAL  BORDER AREA.  MODELS STILL INDICATE THAT THIS WILL BE PRECEDED BY  THE CONTINUED EAST NORTHEASTWARD PROPAGATION OF A HIGH-LEVEL JET  WHICH HAS EMERGED FROM THE PACIFIC...ACROSS THE UPPER MIDWEST AND  GREAT LAKES REGION.    CYCLOGENESIS SUPPORTED BY THIS LATTER FEATURE ALONG A SOUTHWARD  ADVANCING COLD FRONT APPEARS LIKELY TO PROCEED...WITH A CONTINUED  SLOW DEEPENING OF THE LOW FORECAST AS IT MIGRATES NORTHEASTWARD OUT  OF IOWA EARLY WEDNESDAY...ACROSS NORTHERN LOWER MICHIGAN...INTO  WESTERN QUEBEC AROUND OR SHORTLY AFTER 12Z THURSDAY.  WHILE THE  MOISTENING WARM SECTOR OF THE LOW SURGES ACROSS THE LOWER GREAT  LAKES REGION AND OHIO VALLEY DURING THE DAY...THE SOUTHEASTWARD  ADVANCING COLD FRONT IN ITS WAKE IS EXPECTED TO REACH THE LOWER  GREAT LAKES...LOWER OHIO VALLEY...OZARK PLATEAU AND SOUTHERN PLAINS  BY THE END OF THE PERIOD.    LARGE-SCALE FORCING FOR UPWARD VERTICAL MOTION ASSOCIATED WITH THE  CYCLONE...AND ALONG THE TRAILING COLD FRONT...ARE EXPECTED TO  PROVIDE THE FOCUS FOR THUNDERSTORM ACTIVITY WEDNESDAY AND WEDNESDAY  NIGHT.  SOME OF THESE STORMS ARE EXPECTED TO BE SEVERE...WITH SWATHS  OF POTENTIALLY DAMAGING WIND GUSTS POSSIBLE ACROSS SOUTHERN PORTIONS  OF THE GREAT LAKES REGION.     ..GREAT LAKES REGION INTO MIDDLE MS AND LOWER OH VALLEYS    IT STILL SEEMS THAT AN EXTENSIVE AREA OF GENERALLY WEAKENING  CONVECTION WILL SPREAD WITH THE STRONGER LARGE-SCALE  ASCENT...NORTHEAST AND EAST OF THE SURFACE CYCLONE...INTO A  PROGRESSIVELY MORE STABLE ENVIRONMENT ACROSS MUCH OF LOWER MICHIGAN  AND ADJACENT AREAS OF THE GREAT LAKES TO THE NORTH EARLY IN THE DAY.  IT REMAINS UNCLEAR WHETHER CONVECTION ON THE SOUTHERN FLANK OF THIS  ACTIVITY WILL REMAIN STRONG...AND GRADUALLY RE-INTENSIFY AS  DESTABILIZING NEAR-SURFACE INFLOW STRENGTHENS BY MIDDAY...OR NEW  DEVELOPMENT OCCURS IN RESPONSE TO LOW-LEVEL WARM ADVECTION ALONG A  TRAILING OUTFLOW BOUNDARY/DIFFERENTIAL HEATING ZONE ACROSS NORTHERN  ILLINOIS/INDIANA.    REGARDLESS...GUIDANCE CONTINUES TO INDICATE RAPID LOW-LEVEL MOISTURE  RETURN WILL OCCUR AHEAD OF THE CONVECTIVE BOUNDARY AND COLD  FRONT...WITH PRECIPITABLE WATER INCREASING TO 2+ INCHES...AND  SURFACE DEW POINTS INCREASING TO NEAR 70F AS FAR NORTH AS SOUTHERN  LOWER MICHIGAN BY AFTERNOON.  ALTHOUGH THE CORE OF THE STRONGER  LOWER/MID TROPOSPHERIC WIND FIELDS...ON THE ORDER OF 50-70 KT...MAY  SHIFT TO THE EAST OF THE CYCLONE...AND TO THE NORTH OF THE MORE  SUBSTANTIVE BOUNDARY LAYER DESTABILIZATION...40 TO 50 KT WESTERLY  MEAN FLOW APPEARS LIKELY TO PERSIST ACROSS MUCH OF THE SOUTHERN  GREAT LAKES REGION THROUGH THE DAY.  GIVEN THESE SPEEDS...AND THE  POTENTIAL FOR HEAVY PRECIPITATION LOADING WITHIN THE EVOLVING  EASTWARD PROPAGATING CONVECTIVE SYSTEM...SWATHS OF SEVERE SURFACE  WIND GUSTS MAY ACCOMPANY ACTIVITY.    IT DOES NOT SEEM OUT OF THE QUESTION THAT PEAK GUSTS COULD AT LEAST  APPROACH SIGNIFICANT SEVERE CRITERIA /65 KT/.  A COUPLE OF TORNADOES  ALSO APPEAR POSSIBLE...PARTICULARLY NEAR THE INITIAL CONVECTIVE  BOUNDARY WHICH COULD TEMPORARILY STALL ROUGHLY NEAR THE SOUTHERN  MICHIGAN/INDIANA AND OHIO BORDER AREA. UNCERTAINTIES   ..HOWEVER  STILL APPEAR TOO LARGE FOR AN INTRODUCTION OF 10  PERCENT SIG SEVERE PROBABILITIES...AND AN ASSOCIATED HIGHER  CATEGORICAL SEVERE OUTLOOK...AT THE PRESENT TIME.    WEAKENING PRE-COLD FRONTAL WIND FIELDS/SHEAR...AND MID/UPPER FORCING  FOR ASCENT...WITH SOUTHWARD EXTENT ACROSS THE MIDDLE  MISSISSIPPI/LOWER OHIO VALLEYS INTO THE SOUTHERN PLAINS IS EXPECTED  TO RESULT IN SIMILAR TRENDS CONCERNING SEVERE WEATHER POTENTIAL  WEDNESDAY INTO WEDNESDAY EVENING.    ..KERR.. 09/09/2014