[LeArc] Forecast Discussion : MLI@ 1/27/03 2:51:16 PM

[learc@mailman.qth.net]

The following weather message is provided by McDonough County E.S.D.A.


FXUS63 KDVN 272053
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
250 PM CST MON JAN 27 2003

MAIN FCST CONCERN IS POTENTIAL FOR WINTERY MIX ON TUE AND NEED FOR
ADVISORY. WEST-NORTHWEST FLOW JUST ALOFT WILL CONTINUE TO BUILD AND
REINFORCE WARM WEDGE ALOFT ACRS THE AREA THROUGH TUE MORNING...
BEFORE H85 COLD FRONT STARTS TO DROP SOUTH AGAIN LATER TUE AFTERNOON.
PROBLEM IS COLD GROUND AND SLOWER WARMING AT SFC. SFC TEMPS WILL
CLIMB OVERNIGHT AS SOUTH BREEZE CONTINUES...WITH TEMPS REACHING MID
20S BY 12Z ACRS THE NORTH...AND UPPER 20S SOUTH...MUCH LIKE ONGOING
PACKAGE ALREADY ADVERTISING. LEAD VORT DROPPING IN FROM NORTHERN
PLAINS...ALONG WITH ONGOING BRISK WAA IN LOW TO MID LEVELS MAKING
FOR PLENTY OF UVM'S/POS OMEGAS LATE TONIGHT FOR AT LEAST MID CLOUD
GENERATION ACRS THE NORTH HALF AS NIGHT PROGRESSES. FCST SOUNDINGS
AND PROG LIFTING MECHANISMS SUGGEST SPOTTY FREEZING DRIZZLE
POSSIBLE ACRS THE NORTH LATE TONIGHT...AND WILL ADD THREAT. PREFER
GFS VORT HANDLING AND SFC FEATURE DEVELOPMENT OVERNIGHT AND INTO
TUE...WHICH PRODUCES NICE ROUND OF LOW TO MID LEVEL FORCING TO THE
NORTH OF DEVELOPING WAVE ON INCOMING COLD FRONT...RIGHT OVER THE
NORTHERN 2/3'S OF THE DVN CWA. THIS COMBINED WITH ROBUST
ISENTROPIC LIFT...LOOKING AT 295 K SFCS...WILL MAKE FOR A CATEGORICAL
PRECIPITATION EVENT FOR TUE OVER MOST OF THE CWA. FCST SOUNDINGS AND
WARM WEDGE ALOFT...PAINT FREEZING RAIN AND SLEET PICTURE FOR THE
MORNING OVER NORTHERN 2/3'S...BEFORE COOLING ALOFT FROM INCOMING CAA
FROM THE NORTH...AND DYNAMICAL COOLING PROCESSES MAKE A SWITCH OVER
TO ALL SNOW. POTENTIAL SNOW AMOUNTS OF COURSE DEPEND ON SPEED OF
SWITCH OVER FROM RAIN AND SLEET ALOFT...TO A FROZEN STATE TO
MAKE MOST OF AVAILABLE MOISTURE. INITIAL THOUGHTS SUGGEST SWITCH OVER
TO OCCUR LATE ENOUGH FOR ONLY 1-2 INCHES OF ACCUMULATION...BUT
LINGERING FORCING AND SOME DENDRITIC POTENTIAL COULD ADD UP TO
RATHER NARROW SWATH OF 3 INCHES FROM WEST OF CLINTON...TO MOUNT
CARROLL AND STERLING BY EARLY EVENING. THUS WITH SOME ICING
POSSIBLE...AND FOLLOWING LIGHT SNOW OVER THAT...FEEL NEED FOR
WINTER WX ADVISORY TUESDAY GENERALLY FROM I-80 ON NORTH FOR TRAVEL
IMPACT. NIGHT SHIFT WILL HAVE TO ACCESS THREAT FURTHER SOUTH...BUT
FEEL SFC TEMPS TO RECOVER TO ABOVE FREEZING BY TIME BULK OF PRECIP
REACHES DOWN THERE...BUT SOME SLEET MAY IMPACT THOSE AREAS AS WELL
WITH ONSET. LINGERING SNOW WILL DIMINISH IN THE EVENING FROM NORTH-
TO-SOUTH WITH LITTLE ADDITIONAL ACCUMULATION EXPECTED. WILL BANK ON
PRECIP AND CLOUD COVER TO KEEP TEMPS GENERALLY IN THE MID 30S ON
TUE(MAYBE TOUCH WARMER ACRS SOUTH)...WITH INCOMING COLD AIR AND
SOME CLEARING TO DROP TEMPS INTO THE TEENS BY WED MORNING.

.LONGER RANGE(THU-MON)...LOOKS LIKE SOME TEMP RECOVERY ON BACKSIDE
OF RETREATING RIDGE FOR THU...BUT FEEL SLOSH BACK EFFECT WITH
SOUTHEAST SFC FLOW FROM RIDGE CENTER...TO KEEP TEMPS FROM WARMING
ABOVE THE MID 30S. WAVE DROPPING ACRS THE MN ARROWHEAD WITH TRAILING
TROUGH DOWN ACRS THE LOCAL AREA TO BRING PRECIP THREAT FOR THU NIGHT.
MRF HAS COOLER LLVL THERMAL PARAMETERS FOR ALL SNOW THREAT..WHILE
ECMWF WARMER WEDGE ALOFT MAY SUPPORT RAIN OR FREEZING RAIN...
DEPENDING ON SFC TEMPS. WILL GO CHANCE OF SNOW OR ZR FOR NOW. WILL
CONTINUE LIGHT RAIN OR SNOW THREAT INTO MAINLY FRI MORNING PER
EXTENDED GFS AND ECMWF...AS WAVE DIGS AND SETTLES ACRS THE SOUTHERN
GRT LKS AND OH RVR VALLEY. WOULD EXPECT PRECIP AND CLOUD COVER TO
KEEP TEMPS IN MID 30S FOR FRI HIGHS. MEDIUM RANGE MODEL ENSEMBLE OF
SOLUTIONS OVER THE WEEKEND START TO DIVERGE IN HANDLING EXTENT OF
FLATTENING/ZONAL FLOW PATTERN...INCLUDING WARMING AND NEXT BIG PIECE
OF PACIFIC NORTHWEST WAVE ENERGY THAT WILL EVENTUALLY PROPAGATE THRU
THIS FLOW. IN ANY CASE...WARM UP LOOKS ON TAP WITH LOW TO MID 40S
LOOKING REASONABLE FOR SAT...EVEN WITH EXPECTED BOUT OF WAA
PRECIP/RAIN. UKMET AND EURO FARTHER NORTH WITH DEVELOPING LOW CENTER
FROM ABOVE MENTIONED INCOMING WAVE...WITH PLACEMENT OVER THE NORTHERN
PLAINS...WHILE MRF OVER CENTRAL KS AT 12Z SUN. FEEL MRF MAY BE TOO
QUICK TO ROLL SUCH A STRONG FEATURE OUT TOWARD THE CWA ON SUNDAY...
AND WILL PLAY IT AS A MAINLY DRY AND CONTINUED STRONG WAA DAY...
50 DEGREES MAY BE CONSERVATIVE. IN-BETWEEN SOLUTION WOULD
CREATE POSSIBLE SET UP FOR SEVERE WX THREAT ACRS THE SOUTHERN PLAINS
AND INTO THE MID MS RVR VALLEY LATE SUN AND SUN NIGHT...WHILE SNOW
STORM RAGES ACRS THE NORTHERN AND CENTRAL PLAINS...INTO MN. WILL
ANXIOUSLY AWAIT FURTHER RUNS. TOO FAR AWAY FOR DETAILS...BUT LOCAL
CWA MAY GET DRY SECTORED SUNDAY NIGHT...WITH JUST SOME COOLING WRAP
AROUND MIXED PRECIP ON MON BEHIND DEPARTING SYSTEM.


COORDINATED WITH ARX...DVMX...THANX!

.DVN...
IA...WINTER WEATHER ADVISORY TUESDAY FOR NORTHEAST AND EAST CENTRAL
IA...INDEPENDENCE AND DUBUQUE DOWN TO SIGOURNEY TO WAPELLO
IL...WINTER WEATHER ADVISORY TUESDAY FOR NORTHWEST IL...GENERALLY
ALONG AND NORTH OF I-80.
MO...NONE.

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