[LeArc] Forecast Discussion : MLI@ 3/19/03 3:06:33 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 192111 CCA
AFDMLI

AREA FORECAST DISCUSSION...CORRECTED TYPOS
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
305 PM CST WED MAR 19 2003

REGIONAL AND LOCAL 88D LOOPS INDICATING MAIN RAIN SHIELD MAKING ITS
WAY NORTH-NORTHWEST OVER THE CWA. THIS PRECIP BAND...BEING INDUCED
ALONG AND NORTH OF LARGE ELONGATED VORT SPOKE PIN-WHEELING AROUND
SOUTHERN PLAINS CUT-OFF CYCLONE COMPLEX...SHOULD CONTINUE TO LIFT
NORTH AND WEST OF THE CWA THIS EVENING. EXTRAPOLATION...WHICH
AGREES ALONG WITH LATEST META AND RUC SOLUTIONS...TAKES BULK OF
THIS PRECIP BAND OUT OF THE CWA BY 03 TO 04Z THIS EVENING. BOTH
MODELS SUGGEST SOME MUCH MORE SPOTTY SHOWERS/RAIN TO BE GENERATED
ALONG AND NORTH OF APPROACHING WARM FRONT(NOW PUSHING ACRS NORTHEAST
MO AND SOUTH CENTRAL IL) ACRS THE SOUTHEAST CWA AFTER MAIN BAND HAS
EXITED. THIS SECONDARY PRECIP PROGGED TO LINGER AFTER MIDNIGHT...BUT
FEEL INCOMING NVA BEHIND VORT WING AND NOCTURNAL EFFECT FROM 06Z ON
...CONCEPTUALLY DOESN'T SUPPORT MUCH PRECIP FOR SECOND HALF OF
TONIGHT AND MAY NOT MENTION LATE NIGHT PRECIP POSSIBILITY. WILL
LIMIT ELEVATED EMBEDDED THUNDER WORDING JUST TO THE SOUTH THIS
EVENING...AS PRECIP MOVING INTO COOLER AND STABLER AIR HAVING ITS
EFFECT. TEMPS TO BE TRICKY TONIGHT...WITH AFTERNOON TEMPS
CURRENTLY BELOW PROJECTED LOWS FOR THE OVERNIGHT PERIOD. AS WARM
FRONT LIFTS UP ACRS AT LEAST SOUTHEAST THIRD OF THE CWA..THAT PART
TO EXPERIENCE STEADY OR SLOWLY RISING TEMPS OVERNIGHT...BUT WILL SIDE
WITH COLDER FWC LOWS ACRS THE NORTH AND NORTHWEST...WHERE COOL
NORTHEAST SFC INFLUX LASTS THE LONGEST(GENERALLY UPPER 30S). COULD
BE WIDE RANGE OF TEMPS FROM CID...TO MACOMB BY MORNING. THE WINDS
WILL DECREASE ACRS THE CWA THROUGH 06Z-08Z AS WARM FRONT/INVERTED
TROUGH ROTATES TO THE NORTHWEST AND DIVIDES THE CWA FROM NORTHEAST-
TO-SOUTHWEST. LIGHTER CONVERGENT FLOW INTO THIS BOUNDARY...ALONG WITH
LINGERING MOISTURE FROM THIS EVENINGS RAINS...MAY PRODUCE ENOUGH FOG
FOR ZONE MENTION AFTER MIDNIGHT.

THURSDAY TO BE INTERESTING. LLVL FRONT/TROUGH TO CONTINUE TO SET
UP IN NORTH-TO-SOUTH FASHION JUST TO THE WEST OF THE CWA...WITH 15-25
KT SOUTHERLY H85 FLOW PUMPING UP TEMPS AND THTA-E ALONG AND EAST OF
THE CWA...AND ESPECIALLY OVER EASTERN IL BY EARLY THU AFTERNOON.
FLOW MUCH WEAKER AND COLD CONVEYOR BELT INFLUENCED OVER CENTRAL AND
WESTERN IA. ETA SUGGESTS CAPE TO BREACH THE 1K J/KG MARK BY EARLY
AFTERNOON OVER EASTERN IL. THUS...AS SOUTHERN EXTENT OF VORT
COMPLEX DUMBBELLS BACK EAST ACRS MO AND SOUTHERN IL THU AFTERNOON...
EXPECT CONVECTION TO DEVELOP FROM EAST CENTRAL MO...UP INTO
NORTHERN IL. NORTHERN PORTION OF VORT COMPLEX ALSO TO GET PUSHED EAST
MORE DIRECTLY ACRS THE DVN CWA THU AFTERNOON AND EVENING...AS
INTERACTION WITH VIGOROUS RIDGE-RIDING VORT IN NORTHERN
STREAM TAKES PLACE. THIS NORTHERN FEATURE WILL DROP ACRS THE
NORTHEAST PLAINS AND NORTHWEST MN AND IS PROGGED TO CUT OFF. THUS
ANOTHER FORCING/POS OMEGA PUNCH EXPECTED OUT AHEAD OF THIS PROCESS
OVER THE CWA BY LATE THU AFTERNOON....ALONG WITH SOME UPPER
DIFFLUENCE AHEAD OF APPROACHING 60-70 KT SMALL JET MAX PUNCHING TO
THE SOUTHEAST OUT OF THE NORTHERN PLAINS. BUT AGAIN...BEST
INSTABILITY AND CAPES FOR STRONGER STORMS WILL BE SHUNTED EAST OF THE
AREA OF CONCERN BY THEN. BIG TEMP CONTRAST POSSIBILITY TO CONTINUE ON
THU...FROM COOLER WEST...TO WARMER POTENTIAL IN THE EAST. IF ENOUGH
BREAKS IN CLOUD COVER AND BETWEEN CONVECTION CAN OCCUR...A 70 COULD
BE REACHED ACRS THE FAR EAST AND SOUTHEAST BY MID AFTERNOON...WHILE
FAR WEST AND NORTHWEST CWA MAY HAVE TROUBLE GETTING OUT OF THE 50S.
AS SFC WAVE RIPPLES UP EASTWARD ALONG ADVANCING FRONT...AND UPPER
VORT SHEARS ACRS THE AREA...PRECIP THREAT WARRANTED FOR THU EVENING.
THEN COLDER AIR TO MAKE ITS WAY INTO THE AREA LATE THU NIGHT/FRI
MORNING ON INCREASING NORTHWEST WINDS IN WAKE OF RETREATING FRONT.
GUIDANCE UPPER 30S ACTUALLY LOOK GOOD AROUND 12Z FRI...GO FIGURE.

THERE MAY BE LARGE BREAKS IN THE CLOUD COVER FRIDAY MORNING...AS
PROGGED DRY SLOT AND 60-70 KT H3 MB JET-LET WHIRLS TO THE SOUTH OF
CUT-OFF LOW SETTLING OVER UPPER MS RVR VALLEY. FCST SOUNDINGS SUGGEST
STEEPENING LLVL LAPSE RATES...AND WITH SOME INSOLATION...EXPECT
ENOUGH MIXING FOR BREEZY CONDITIONS AND TEMPS WARMING JUST ABOVE
GUIDANCE(AROUND 50). INSTABILITY SHOWERS MAY LOOK TO BREAK OUT ON
NOSE OF INCOMING CVA WITH UPPER SYSTEM FRIDAY AFTERNOON...ALTHOUGH
MODELS SUGGEST BULK OF PRECIP TO REMAIN NORTH. WILL KEEP CHANCE POPS
ACRS THE NORTHERN TWO THIRDS FOR NOW.

.LONGER RANGE(SAT-WED)...AS NORTHERN STREAM VORTEX OVER THE GRT
LKS PULLS AWAY ON SAT...LLVL NORTHWEST FLOW WILL CONTINUE
TO INFILTRATE THE AREA BEHIND IT. NORTHWEST FLOW SHOULD ACTUALLY
START MODERATING FROM THE NORTHWEST HOWEVER...AND EXPECT MILDER DAY
SAT THAN FRI. THEN LOW AMPLIFIED AND BROAD UPPER RIDGING-ALMOST ZONAL
FLOW TO BUILD ACRS THE AREA FOR CONTINUED MODERATING TEMPS ON SUNDAY.
MEDIUM RANGE MODELS THEN VARY ON HANDLING SURGE OF WAVE ENERGY OUT OF
PACIFIC NORTHWEST AND THROUGH NORTHERN STREAM WESTERLIES ON MONDAY.
TRAILING COLD FRONT OFF DEEPENING SFC LOW...SKIRTING ACRS SOUTHERN
CANADA...WILL EVENTUALLY SWEEP THROUGH THE LOCAL CWA. TIMING AND
EXTENT OF WARMING AHEAD OF IT AT QUESTION WITH MODEL DIFFERENCES.
ECMWF QUICKEST WITH ALMOST A MIDDAY MONDAY FROPA...WHILE MRF AND
UKMET NOT UNTIL MONDAY EVENING. WITH LATER FROPA SCENARIO...PRE-
FRONTAL WARMING SOUTHWEST FLOW COULD BOOST TEMPS TO NEAR THE 70
DEGREE MARK IF RAIN HOLDS OFF AND SOME INSOLATION OCCURS. WILL PLAY
LATER UKMET/MRF TRENDS AND GO ABOVE GUIDANCE HIGHS...AND MENTION
SHOWER THREAT LATE. ALL MEDIUM RANGE MODELS SUGGEST FRONT TO LAY OUT
FROM EAST-TO WEST ALONG AND JUST SOUTH OF THE CWA MONDAY NIGHT INTO
TUE...AS SOUTHERN STREAM WAVE HOLDS IT UP AS IT STARTS TO PULL OUT OF
SOUTHERN PLAINS. THIS WOULD SUGGEST GOOD POSSIBILITY FOR A SLIGHTLY
ELEVATED SHOWER AND THUNDERSTORM EVENT ON FOR TUE. AS WAVE ROLLS UP
ALONG FRONT AND EXITS...COOLER WRAP AROUND RAIN FOR WED. EARLY
INDICATIONS/EXTENDED THERMAL PROFILES SUGGEST POSSIBLE RAIN/SNOW MIX
POSSIBLE ACRS THE NORTH...BUT WILL KEEP ALL RAIN FOR NOW WITH HIGHS
IN THE 40S. NEXT WED MAY BE SIMILAR TO TODAY.

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

$$

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