[LeArc] Forecast Discussion : MLI@ 12/1/02 3:01:45 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 012113
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
310 PM CST SUN DEC 1 2002

LATEST SFC ANALYSIS AND MSAS LOOP INDICATING STRONG AND LARGE
PRESSURE FALL BULLSEYE SHIFTING FROM EAST IA TO CENTRAL/NORTHEAST IL
ATTM...WITH WEST-TO-EAST ORIENTED COLD FRONT SAGGING SOUTH TOWARD
THE FALLS ACRS SOUTHERN MN AND CENTRAL WI. POST FRONTAL STRATUS DECK
SEEN ON VIS LOOP ORGANIZING IN CYCLONIC FLOW OVER THE NORTHWEST GRT
LKS...POISED TO DROP DOWN AND CONTINUE TO DEVELOP AFTER LLVL
BAROCLINICITY ARRIVAL ACRS THE NORTHERN CWA LATE TONIGHT.

MAIN FORECAST CHALLENGE CONTINUES TO BE LIGHT SNOW EVENT ON MONDAY.
W/V IMAGERY INDICATING VORT SHEARING OUT OF THE GRT BASN...WHICH
SHORT RANGE MODELS SIMILARLY DRAW TOWARD CONFLUENCE AREA ACRS THE
EAST CENTRAL PLAINS. BRUNT OF CVA WITH THIS FEATURE TO GET SHUNTED
TO THE SOUTH ACRS MO...BUT IT WILL ALSO INDUCE WEAK CYCLOGENESIS ON
WEST END OF THE COLD FRONT THIS EVENING. SFC LOW WILL CONTINUE TO
TRY AND RIPPLE EAST AS LLVL THERMAL GRADIENT PUSHES SOUTH...WITH
INHERENT MID LEVEL LIFT AND FORCING CREATING BAND OF PRECIP TO THE
NORTH OF IT...IN THIS CASE DEVELOPING ACRS NORTHERN IA...INTO IL BY
MONDAY MORNING. AS LLVL BAROCLINICITY TIGHTENS AND DROPS FURTHER
SOUTH...IT WILL COMBINE WITH MID LEVEL FORCING AND RIGHT REAR EFFECT
OF 100+ KT STREAKING H3 JET ACRS THE SOUTHERN GRT LKS FOR A RATHER
SHORT LIVED BOUT OF DECENT POS OMEGAS FROM 12Z TO 19Z OR SO. PROBLEM
OF DEEP RH'S/LLVL SATURATION DURING PEAK LIFT SHOULD LIMIT
PRECIP AMOUNT POTENTIAL TO ALREADY ADVERTISED INCH OF SNOW OR SO ACRS
THE NORTH HALF BY 00Z TUE...BUT ALSO CONCERNED THAT NARROW SWATH OF
ENHANCED LIFT TO THE NORTHEAST OF VORT NOSE...OVER CONVERGING LLVL
NORTHEAST FLOW MAY PRODUCE LOCALIZED 2-3 INCH AMOUNTS FROM JUST
NORTH OF THE QUAD CITIES...TO MOUNT CARROLL AND FREEPORT. SOUTH
THIRD APPEARS LAST TO SATURATE...WITH TRACE TO JUST LIGHT PRECIP
EVENT TO OCCUR THERE. MAY BE SOME INITIAL LIQUID FORM AS WELL...BUT
SHOULD CHANGE TO ALL SNOW/FLURRIES BY MIDDAY WITH COOLING COLUMN.
WILL UP AMOUNTS TO 1-2 INCH RANGE ACRS NORTHEAST AND EAST CENTRAL
ZONE GROUPINGS...AND ALLOW FOR MID SHIFT TO MAKE FINAL DETAILED
ACCUMULATION POTENTIAL FORECAST.

DEEPENING NORTHEAST FLOW AT SFC SHOULD MAKE FOR "SLOSH BACK" EFFECT
WITH STRATUS OFF LK MI FOR CLOUDS TO CONTINUE ACRS MUCH OF THE CWA
MON NIGHT INTO TUE...AND WITH NEXT UPSTREAM VORT DROPPING OFF TOP
OF WEST COAST REX BLOCK AND ACRS MN/WI/NORTHERN IL MON NIGHT...MAY
MAKE FOR LINGERING FLURRIES OUT OF EASTERN ADVECTED STRATUS. YET
ANOTHER NORTHERN STREAM VORT DROPPING QUICKLY DOWN THROUGH
REINFORCED NORTHWEST FLOW BY LATE TUE MAY GENERATE MORE LIGHT SNOW
SHOWERS/FLURRIES TUE AFTERNOON. WILL CHILL DOWN TUE NIGHT LOWS...
OTHERWISE ONGOING TEMPS LOOK GOOD WITH NOT MUCH CHANGE NEEDED.

.LONGER RANGE(WED-SUN)...MEDIUM RANGE MODELS GENERALLY SIMILAR TO
START OFF EXTENDED RANGE DURING THE MIDWEEK PERIOD. COLD SFC
ANTICYCLONE IN PLACE ACRS NORTHERN PLAINS AND UPPER MIDWEST UNDER
BROAD CYCLONIC FLOW/LONG WAVE PATTERN ALOFT OCCUPYING MOST OF THE
CONUS...WITH WAVE SHEARING SOUTHEAST TOWARD GENERAL CONFLUENCE
BETWEEN SOUTHERN AND NORTHERN STREAM. FEATURE SHOULD WRING OUT AT
LEAST SOME FLURRIES ON WED WITH HIGHS STRUGGLING TO REACH MID 20S.
MODELS START TO DIFFER FROM HERE...BUT GENERAL CONSENSUS MAKES FOR
ONE MORE COLD DAY THU...THEN MODERATING TEMPS ON FRI AHEAD OF NEXT
MAJOR WAVE DROPPING ACRS SOUTHERN CANADA. CYCLONIC FLOW MAY FLATTEN
SOME AHEAD OF THIS WAVE FOR WARM UP FROM WEST ON FRI PROBABLY
ABOVE GUIDANCE VALUES...BEFORE NEXT REINFORCING COLD SHOT DUMPS DOWN
ACRS THE UPPER MIDWEST NEXT WEEKEND. TIMING DIFFERENCES ON MAIN
ARCTIC FRONT...WITH UKMET QUICKEST FOR SAT COOL DOWN...WHILE MRF-
GFS AND EURO SLOWER AND WOULD ALLOW FOR ANOTHER MID-UPPER 30 DEGREE
DAY. WILL TREND DOWN ONGOING 40S INTO THE MID-UPPER 30S FOR NEXT
SAT...WITH CHILL DOWN INTO UPPER 20S/LOWER 30S FOR NEXT SUN. LOOKS
GENERALLY DRY THU-SAT WITH BLOCKING GULF RIDGE...BUT NEXT UPPER
WAVE/VORT DUE NEXT SUN IN CONTINUING CYCLONIC FLOW SAGA FOR AT
LEAST FLURRIES.

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

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