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Feb. 23-25th Winter Storm Potential


Chicago Storm

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ILX going with a watch for the NE 1/4, ILX really needs to start putting county names in the watch,warning, advisory column instead of the numbers cuz I have no clue how far west that'll go or how far south.. Oh NM it just came out:

URGENT - WINTER WEATHER MESSAGENATIONAL WEATHER SERVICE LINCOLN IL320 PM CST WED FEB 23 2011...WINTER STORM WATCH FOR PORTION OF CENTRAL AND EAST CENTRALILLINOIS FOR THURSDAY EVENING AND INTO LATE THURSDAY NIGHT.... A LOW PRESSURE SYSTEM WILL DEVELOP OVER THE WESTERN PLAINSEARLY THURSDAY...AND MOVE EAST ALONG A STATIONARY FRONT. AS THELOW MOVES OVER SOUTHERN ILLINOIS AND SOUTHERN INDIANA THURSDAYNIGHT...COOLER AIR WILL FILTER INTO THE AREA. RAIN WILL DEVELOPOVER CENTRAL ILLINOIS ON THURSDAY...CHANGING OVER TO SNOW THURSDAYEVENING AND BECOMING HEAVY. SNOWFALL AMOUNTS WILL BE HEAVIEST INTHE EAST CENTRAL HALF OF ILLINOIS...NORTHEAST OF A LINE FROM EL PASO...TO DECATUR...TO MATTOON...TO PARIS.ILZ038-043>046-053>057-240530-/O.NEW.KILX.WS.A.0002.110225T0000Z-110225T1200Z/MCLEAN-DE WITT-PIATT-CHAMPAIGN-VERMILION-MACON-MOULTRIE-DOUGLAS-COLES-EDGAR-INCLUDING THE CITIES OF...BLOOMINGTON...NORMAL...CHAMPAIGN...URBANA...DANVILLE...DECATUR...CHARLESTON...MATTOON320 PM CST WED FEB 23 2011...WINTER STORM WATCH IN EFFECT FROM THURSDAY EVENING THROUGHLATE THURSDAY NIGHT...THE NATIONAL WEATHER SERVICE IN LINCOLN HAS ISSUED A WINTER STORMWATCH...WHICH IS IN EFFECT FROM THURSDAY EVENING THROUGH LATETHURSDAY NIGHT. * TIMING...SNOW IS EXPECTED TO DEVELOP THURSDAY EVENING AND CONTINUE INTO LATE THURSDAY NIGHT. * ACCUMULATIONS...SNOW AMOUNTS OF FROM 5 TO 7 INCHES WILL BE POSSIBLE IN THE WATCH AREA.* WIND...WINDS WILL BE NORTH NORTHEAST AT 15 TO 20 MPH. * IMPACTS...THE HEAVY WET SNOW WILL MAKE TRAVEL DANGEROUS ON THURSDAY NIGHT. ROADS WILL BE SLICK AND HAZARDOUS IN MANY LOCATIONS AS BLOWING AND DRIFTING SNOW WILL ALSO

Going along and NE of IL 121 for locals

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I see csnavy lurking, care to share your thoughts?

The NAM has pulled inside of its useful range, and the trend is unmistakably north, along with the GFS. The SREF has uncharacteristically and abruptly begun to change course at the last minute, with many of its members suddenly developing a strong deformation zone, and thus expanding the precip shield to the north of the track. This is a classic case where staying ahead of the game is crucial to getting a good forecast out soon enough. It's pretty clear that the shortwave coming in off the Pacific is stronger than was originally calculated, and that... unfortunately, we were getting some pretty abysmal feedback errors in earlier runs.

Earlier runs also tended to shred the wave as it entered the SW, but in the process of doing so, seemed to have lost track of the fact that the overall DPVA was actually increasing as it opened from a shear-dominated lobe into an advection lobe. With a good baroclinic zone already in place, that's a great recipie for lee-cyclogenesis, which seemed overly delayed. In fact, we're already seeing a pressure response over Texas/western High Plains.

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yeah the GFS has a long ways to go, the NAM started showing signs of a north jog at 12z.

This will be a tough one to take if it doesn't pan out here...in some ways tougher than the Groundhog blizzard even though that was bigger. We had favorable trends up until 12z but it appears to be reversing now. Ah well, enough venting from me.

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The NAM has pulled inside of its useful range, and the trend is unmistakably north, along with the GFS. The SREF has uncharacteristically and abruptly begun to change course at the last minute, with many of its members suddenly developing a strong deformation zone, and thus expanding the precip shield to the north of the track. This is a classic case where staying ahead of the game is crucial to getting a good forecast out soon enough. It's pretty clear that the shortwave coming in off the Pacific is stronger than was originally calculated, and that... unfortunately, we were getting some pretty abysmal feedback errors in earlier runs.

Earlier runs also tended to shred the wave as it entered the SW, but in the process of doing so, seemed to have lost track of the fact that the overall DPVA was actually increasing as it opened from a shear-dominated lobe into an advection lobe. With a good baroclinic zone already in place, that's a great recipie for lee-cyclogenesis, which seemed overly delayed. In fact, we're already seeing a pressure response over Texas/western High Plains.

thanks a bunch, appreciate you taking the time.

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The NAM has pulled inside of its useful range, and the trend is unmistakably north, along with the GFS. The SREF has uncharacteristically and abruptly begun to change course at the last minute, with many of its members suddenly developing a strong deformation zone, and thus expanding the precip shield to the north of the track. This is a classic case where staying ahead of the game is crucial to getting a good forecast out soon enough. It's pretty clear that the shortwave coming in off the Pacific is stronger than was originally calculated, and that... unfortunately, we were getting some pretty abysmal feedback errors in earlier runs.

Earlier runs also tended to shred the wave as it entered the SW, but in the process of doing so, seemed to have lost track of the fact that the overall DPVA was actually increasing as it opened from a shear-dominated lobe into an advection lobe. With a good baroclinic zone already in place, that's a great recipie for lee-cyclogenesis, which seemed overly delayed. In fact, we're already seeing a pressure response over Texas/western High Plains.

Nice analysis. It did seem we were at the point where the upper wave--which was being sheared apart partially by earlier runs as it interacted with the fast westerlies along the north end--would be weakened through mid tropospheric warming owing to convection. I personally don't believe the GFS was "convective feedback" but actually a realistic depiction based on its weak and sheared/elongated S/W--NAM seemed to have some convective feedback though. It does seem the upper wave is much stronger than progged and the convectiion is now not weakening the wave but actually enhancing pressure falls and that is now combined with the enhanced DPVA as the S/W ejects eastward--hence the rapid and sudden shift in intensity and track by the weaker models. "Uncle" UKie as Canuck says it had this solution quite a ways ago. UK has a clue every now and then--even I didn't think it would be as intense as the UK had it.

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Nice analysis. It did seem we were at the point where the upper wave--which was being sheared apart partially by earlier runs as it interacted with the fast westerlies along the north end--would be weakened through mid tropospheric warming owing to convection. I personally don't believe the GFS was "convective feedback" but actually a realistic depiction based on its weak and sheared/elongated S/W--NAM seemed to have some convective feedback though. It does seem the upper wave is much stronger than progged and the convectiion is now not weakening the wave but actually enhancing pressure falls and that is now combined with the enhanced DPVA as the S/W ejects eastward--hence the rapid and sudden shift in intensity and track by the weaker models. "Uncle" UKie as Canuck says it had this solution quite a ways ago. UK has a clue every now and then--even I didn't think it would be as intense as the UK had it.

Just for the record, I got that from your boys in the SNE thread.

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DTX

REMAINING DISCUSSION ON THIS SYSTEM IS BASED ON LATEST CONSENSUS.

SLIGHTLY SLOWER TIMING BRINGS ONSET OF SYSTEM SNOWFALL FOR

LENAWEE/MONROE COUNTIES AFTER MIDNIGHT FRIDAY WHILE CONTINUING

NORTHWARD DURING THE OVERNIGHT. A DRY NORTHEASTERLY FEED OF AIR

BETWEEN 800-700MB SHOULD KEEP A SHARP GRADIENT TO ACCUMULATIONS

IMMEDIATELY NORTH OF THE DEFORMATION. MOST IMPACT/HIGHEST

SNOWFALL RATES WILL OCCUR BETWEEN 6-12Z FRIDAY AS VERY STRONG RIGHT

ENTRANCE REGION DYNAMICS INTENSIFY. LATEST THINKING IS FOR TOTAL

SNOWFALL ACCUMULATIONS BY MIDDAY FRIDAY OF 4-6 INCHES FOR

LENAWEE/MONROE/WAYNE COUNTIES...WITH 2-4 INCHES FOR THE SOUTHERN

LIVINGSTON TIER DOWN INTO WASHTENAW COUNTIES. DID DROP SNOWFALL

ACCUMULATIONS OFF CONSIDERABLY TO THE NORTH GIVEN THE DRY AIR. WILL

SAY OUTRIGHT THIS IS SUBJECT TO REVISION GIVEN THE NORTHERLY TREND.

NORTH TO NORTHEASTERLY WINDS ARE EXPECTED TO BE STRONG WITH THIS

EVENT...VALUES LIKELY REACHING 30 MPH.

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