Chicago Discussion
Posted by
JAC on 12/21/2009, 11:29 am
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL 429 AM CST MON DEC 21 2009
.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY.
A MORE POTENT STORM SYSTEM IS EXPECTED TO AFFECT THE MIDWEST AS EARLY AS WEDNESDAY AFTERNOON AND CONTINUE INTO CHRISTMAS DAY. CURRENT INDICATIONS ARE THAT AN AREA OF LOW PRESSURE WILL DEVELOP OVER THE SOUTHERN PLAINS WEDNESDAY...THEN LIFT NORTHWARD ALONG THE MISSISSIPPI RIVER THURSDAY NIGHT INTO EARLY FRIDAY MORNING. IF THE STORM WERE TO TAKE THIS TRACK...THIS COULD RESULT IN A PERIOD OF MIXED PRECIPITATION INCLUDING SNOW...SLEET...AND FREEZING RAIN BY WEDNESDAY NIGHT. SOME SIGNIFICANT SNOW AND ICE ACCUMULATIONS ARE POSSIBLE OVER NORTH CENTRAL AND PERHAPS FAR NORTHERN ILLINOIS BEFORE PRECIPITATION CHANGES TO ALL RAIN. THIS WOULD ALSO IMPLY AN AREA OF HEAVY SNOW WEST OF THE FORECAST AREA...ACROSS PARTS OF IOWA AND WISCONSIN.
COLD AIR WRAPPING AROUND THE BACK SIDE OF THE DEPARTING LOW IS THEN EXPECTED TO CHANGE RAIN BACK TO SNOW OR SNOW SHOWERS OVER MOST OF THE REGION BY DAYBREAK CHRISTMAS MORNING.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL 544 AM CST MON DEC 21 2009
.DISCUSSION... 345 AM CST
RUNNING A BIT BEHIND THIS MORNING...SO PARDON WORDING IF IT SEEMS A BIT TERSE.
WILL GO CLOUDY THROUGH TODAY AS ACARS SOUNDINGS AND MODEL FCST SOUNDINGS SHOW FAIRLY HIGH RH TRAPPED BELOW TOP OF INVERSION AT AROUND 8 THSD FT...AND LITTLE IF ANY WIND IN LLVLS.
HAVE GONE WITH CATEGORICAL POPS FOR OVERNIGHT AS MODELS REMAIN CONSISTENT IN DEVELOPING A BAND OF WARM ADVECTION SNOW ACROSS NRN IL AND PERHAPS AS FAR E AS NWRN INDIANA...MAINLY AFTER MIDNIGHT. THIS SEEMS PLAUSIBLE...NOT ONLY BASED ON MODEL CONSISTENCY...BUT ALSO LOOKING AT WATER VAPOR IMAGERY THAT SHOWS FAIRLY WELL INTACT SHORT WAVE TOPPING LARGER SCALE RIDGE OVER ROCKIES. THIS FEATURE WILL HELP INDUCE MODEST LLVL WARM ADVECTION...WITH NOSE OF BETTER ISENTROPIC UPGLIDE FOCUSED ON ERN IA/NWRN IL BY 06Z. THEREFORE WILL GO WITH HIGHEST QPF OVR NWRN PORTIONS OF FA...AND TAPER POPS AND SNOW AMTS HEADING OFF TO S AND E. RIGHT NOW LOOKS LIKE RELATIVELY MINOR EVENT...WITH 2 TO 4 INCH ACCUMULATIONS POSSIBLE N OF I-88...TAPERING TO AROUND AN INCH ALONG I-80 AND LESS THAN AN INCH SWD FROM THERE.
AREA IS IN A LULL AS THIS SHORT WAVE MOVES OFF TO E AND UPR RIDGING IS INDUCED W OF MS RVR IN RESPONSE TO MUCH STRONGER SYS FCST TO MOVE ACROSS U.S./MEXICO BORDER AREA BY 12Z WED. THIS SYSTEM IS EXPECTED TO EMERGE OVER SRN PLAINS DURG WEDNESDAY...AND QUICKLY DVLP INTO A CLOSED SYS BY WED EVENING. GUIDANCE COMING INTO MUCH BETTER AGREEMENT IN LIFTING OCCLUDING LOW NNEWD OVR OR JUST TO W OF MS RVR WED NIGHT-THURSDAY NIGHT. THIS WILL CREATE A REAL MESS OVR FA. INITIAL WARM ADVECTION PRECIP MAY BEGIN AS SNOW...WITH LONGEST RESIDENCE TIME OF FROZEN PRECIP BEING OVR N CNTRL IL...BUT OF ADDED CONCERN IS PROSPECT OF SOME SIGNIFICANT ICING FROM FREEZING RAIN/SLEET COMBO OVR MUCH OF THE REGION WED AND WED NIGHT AS COLD HIGH PRESSURE SLOWLY BUILDS OVER ONTARIO...JUST TO NE OF LK SUP. THIS SHOULD MAINTAIN COLD LLVL ELY FLOW INTO WED EVENING...BEFORE HIGH GETS DISPLACED FURTHER TO E AND LLVL FLOW VEERS A LTL MORE INTO SE. BOTH 00Z RUNS OF GFS AND NAM ADVERTISE SOUNDINGS THAT KEEP SFC TEMPS BLO FREEZING THROUGH WED NIGHT OVR MUCH OF NRN IL ALONG AND N OF I-80.
EVENTUALLY...ENTIRE FA SHOULD CHG OVER TO ALL RAIN. THIS IS EXPECTED TO TAKE PLACE WED EVENING OVR SERN FA...BUT MAY NOT OCCUR UNTIL THURSDAY MORNING IN RFD AREA...WHERE SVRL INCHES OF SNOW AND ICE MAY ACCUMULATE AS WAA CRANKS UP LATE WED-WED NIGHT. COULD SEE ADVSRY CONDITIONS N CNTRL AND FAR NRN IL BEFORE CHANGE OVER TO LIQUID.
WILL LIKELY BE FLIPPING BACK TO OCNL LIGHT SNOW OR FLURRIES BY CHRISTMAS MORNING AS COLD AIR WRAPS IN FROM SW.
MERZLOCK
|
52
In this thread:
A MAJOR HOLIDAY STORM BREWING -
JAC,
12/21/2009, 10:00 am- Winter Storm Warnings - JAC, 12/22/2009, 1:35 pm
- A new surface low going up the east coast - JAC, 12/22/2009, 9:16 am
- WARNING: Freezing rain to threaten holiday travelers - JAC, 12/22/2009, 8:41 am
- Re: A MAJOR HOLIDAY STORM BREWING - Anung Mwka, 12/22/2009, 7:20 am
- Could see significant freezing rain thru the Midwest - JAC, 12/21/2009, 10:34 am
- Stu's A-B-C's of a Winter Storm - JAC, 12/21/2009, 10:22 am
- Artic Air Funnel - 500mb - JAC, 12/21/2009, 10:13 am
- The Forecasted Surface-Low on GFS - JAC, 12/21/2009, 10:08 am
Post A Reply
This thread has been archived and can no longer receive replies.