[LeArc] Forecast Discussion : MLI@ 3/9/03 2:34:24 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 092043
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
240 PM CST SUN MAR 9 2003

ANOTHER UNSEASONABLY COLD NIGHT IN STORE FOR THE CWA...WITH ARCTIC
HIGH AND VERY COLD AIRMASS IN PLACE OVER SNOW COVER ENSURING NEAR OR
POSSIBLE RECORD LOWS AGAIN TONIGHT. EVEN WITH FULL MARCH INSOLATION
AND GOOD MIXING...HIGHS HAVE STRUGGLED THIS AFTERNOON AND WON'T HAVE
FAR TO GO TO DIP BELOW COOLER MET AND MAV LOWS TONIGHT...AGAIN
SUB-ZERO OVER MUCH OF THE CWA AND NEAR RECORD LOW LEVELS. WILL WORD
POSSIBILITY IN ZONES.  INCOMING HIGH TO MID CLOUDS THICKENING ALONG
LOW TO MID LEVEL BAROCLINIC RIBBON...WILL BE COUNTER-ACTED BY WINDS
FINALLY SUBSIDING AS SFC RIDGE SETTLES OVER THE AREA...THUS FEEL
TEMPS WILL STILL BOTTOM OUT TO...OR JUST BELOW COOLEST GUIDANCE.
THE WIND WILL STILL BE BRISK ENOUGH THIS EVENING TO COMBINE WITH
FALLING TEMPS FOR WIND CHILL VALUES LOW ENOUGH TO BE MENTIONABLE IN
ZONES...AND MAY BE CLOSE TO ADVISORY CRITERIA ACRS THE NORTH. DBQ
-3...MLI -2...AND BRL 0 MOST AT RISK OF APPROACHING RECORDS TONIGHT.

NEXT QUESTION OF INCOMING RIDGE-RIDING VORT/CLIPPER TYPE SYSTEM FOR
LATE TONIGHT AND MONDAY AND AMOUNT OF FORCING AND MOISTURE IT WILL
HAVE FOR SNOW GENERATION. ETA/META STILL WEAKEST ON FORCING AND
VORT STRENGTH...AND AGAIN CREATES LITTLE OR NO PRECIP OVER THE DVN
CWA...WHILE AVN-GFS STILL CLIPS SOUTHWEST AND SOUTHERN CWA WITH AN
INCH OR LESS OF SNOW BY MID MONDAY AFTERNOON. WHILE AVN HAS BEEN
CONSISTENT PAST FEW RUNS...WILL LEAN TOWARD ALSO CONSISTENT UKMET
WITH PRECIP AND SYNOPTIC SCALE FEATURES AND TRENDS. UKMET EVEN
DRIER THIS RUN WITH SOUTH JUST GETTING A DUSTING TO HALF INCH. WILL
TAKE OUT MENTION OF SNOW CHANCE LATE TONIGHT WITH SUCH DRY LLVLS TO
OVERCOME...AND SHORT RANGE MODELS SUGGESTING BEST FORCING MIDDAY AND
INTO MONDAY AFTERNOON JUST AHEAD OF MAIN VORT NOW ROUNDING TOP OF
RIDGE OVER PACIFIC NW. LOOKING AT 285 K ISENTROPIC ANALYSIS...BEST
BUT BRIEF LIFT ACTUALLY TOMORROW AFTERNOON AHEAD OF MAIN VORT AND
BRUNT OF CVA...BUT MODELS VARY ON EXTENT OF LIFT AND SATURATION.
INTERESTING ETA ACTUALLY SATURATES MORE AND ADVERTISES MORE OF A
DIRECT LIFT UP SFCS...WHILE GFS HAS LIFT MORE PARALLEL AND HIGHER
COND P-DEFS. BUT EACH OTHERS PRECIP/QPF ALGORITHMS WOULD SUGGEST THE
OPPOSITE. AGAIN...SOUTHERN CWA MAY STILL BE WORTHY OF LIKELY POPS AND
MINIMAL ACCUMULATION/DUSTING WORDING FOR MONDAY LOOKING AT UKMETS'
FORCING AND PROPAGATION ALONG SLIGHTLY ELEVATED THERMAL GRADIENT...
BUT TO AVOID FLIP-FLOPPING WILL KEEP ONGOING CHANCE POPS FOR NOW.
WILL ALSO MAINTAIN FLURRIES ACRS THE NORTH. FAR NORTHEAST CWA MAY
RECEIVE FILTERED SUNSHINE AND NO PRECIP TOMORROW. TEMPS WILL BE
TRICKY ON MONDAY WITH COLD START...LIGHT SFC FLOW...BACKING H85 FLOW
ALOFT WITH WAA KICKING IN...AND POSSIBLE PRECIP...EVAPORATIVE COOLING
AND SKY COVER. MOST OF THESE PARAMETERS SUGGEST PLAYING COLD SIDE AND
WILL GO WITH COOLEST MAV HIGHS...OR EVEN UNDERCUT THEM SOME.

BETTER-MORE SUBSTANTIAL WAA REGIME IN MORE OF A LAYER TO COMMENCE
MONDAY NIGHT AND LAST ON INTO TUE AS SFC RIDGE DEPARTS DOWN THE OH
RVR VALLEY. WITH H85-H7 WAA AND POTENTIAL VORT DROPPING ALOFT OVER
THE AREA IN LINGERING NORTHWEST FLOW...PROGGED MID LEVEL CONVERGENT
QG FORCING...AND POS OMEGAS SUGGEST A LIGHT SNOW CHANCE FOR LATE
MONDAY NIGHT AND TUE MORNING...MAINLY ACRS THE NORTH. AFTER MORNING
PRECIP THREAT...LLVL RETURN FLOW SHOULD BUMP TEMPS INTO THE UPPER 30S
TO LOWER 40S. THIS IS WELL BELOW GUIDANCE...BUT EXPECT STILL ENOUGH
SNOW COVER TO TEMPER WARM UP POTENTIAL...EVEN WITH BRISK SOUTHWEST
WINDS AT SFC. WESTERN IL/MACOMB AREA WITH LESS SNOW COVER...WILL BE
THE WARM SPOT AND MAY STRIVE INTO THE UPPER 40S/NEAR 50 TUE
AFTERNOON.

.LONGER RANGE(WED-SUN)...MEDIUM RANGE MODEL ENSEMBLES CONTINUE TO
SUGGEST ROBUST TEMPERATURE MODERATION TOWARD THE END OF NEXT WEEK...
AS BROAD UPPER RIDGE AND ASSOCIATED WARMER THERMAL POOL BUILD ACRS
THE REGION FROM OUT OF THE WESTERN CONUS. ALL MODELS NOW WARMER WITH
LLVL THERMAL PATTERN FROM THURSDAY ON...AND WILL OPTIMISTICALLY HAVE
TO TREND UP. SOME DIFFERENCE EARLIER IN PERIOD FOR WED AS UKMET
FURTHER NORTH AND EAST OVER THE GRT LKS IN HANDLING WITH INCOMING SFC
HIGH OUT OF WESTERN CANADA. THIS WOULD ALLOW SOUTHERN STREAM SYSTEM
AND PROBABLE RAIN THREAT TO MAKE IT MUCH FURTHER NORTH AND AFFECT
THE AREA BY MIDWEEK. LATEST MRF AND ECMWF SUGGEST CANADIAN HIGH TO
BUILD FURTHER SOUTH AND WEST OVER THE UPPER MS RVR VALLEY...
EFFECTIVELY DEFLECTING PRECIP SOUTH OF AREA OF CONCERN. WILL LEAN
TOWARD EURO/MRF CONSENSUS AND KEEP WED DRY WITH REINFORCING BUT VERY
TEMPORARY COOL SHOT. WED HIGHS WILL LOOK TO RANGE IN UPPER 30S TO MID
40S. LATEST RUNS AND NOW QUICKER SOLUTION OF INCOMING BROAD UPPER
RIDGE DEFLECTS RIDGE-RIDING CLIPPER FURTHER TO THE NORTH AS IT TRIES
TO DROP ACRS THE GRT LKS ON THU. THIS SUGGESTS BULK OF PRECIP TO STAY
NORTH OF THE CWA ON THU...BUT THAT FAR OUT WILL STILL LEAVE PRECIP
THREAT FOR THE NORTH ANYWAY...AND AWAIT FURTHER MODEL RUNS AND
TRENDS. QUICKLY REBOUNDING THERMAL PROFILES SUGGEST MAINLY RAIN
THREAT ON THU EVEN ACRS THE NORTH. AS IT APPEARS NOW...STRENGTH OF
RETURN FLOW BEHIND RETREATING SFC HIGH SUGGEST TEMPS WELL INTO THE
50S AS EARLY AS FRI...AND A 60 DEGREE PLUS TEMPERATURE POSSIBLE FOR
NEXT WEEKEND.

.DVN...
IA...NONE.
IL...NONE.
MO...NONE.

$$

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