000
FXUS63 KDVN 060825
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
325 AM CDT MON OCT 6 2008
.SYNOPSIS...
LATEST SFC ANALYSIS WAS INDICATING A LOW JUST NORTH OF THE CENTRAL
ND/SD BORDER...WITH ASSOCIATED WARM FRONT EXTENDING TO THE SOUTHEAST
ACRS SOUTHEAST MN...NORTH CENTRAL IA AND DOWN ACRS CENTRAL IL. A LOW
60 SFC DPT FIELD WAS POOLED ALONG AND SOUTH OF THIS FEATURE FROM THE
DAKOTAS INTO FAR NORTH CENTRAL MO. ALOFT...W/V IMAGERY WAS INDICATING
A SUBSTANTIAL SWATH OF MID AND HIGH LEVEL MOISTURE CLOAKING MUCH OF
THE MIDWEST TO THE LEE OF DEEP L/W TROF...WHICH AXIS WAS CURRENTLY
MIGRATING EAST ACRS THE ROCKIES.
$$
.SHORT TERM...TODAY AND TONIGHT...
TIGHTENING PRESSURE GRADIENT ACRS THE MID AND UPPER MS RVR VALLEY TO
THE LEE OF CYCLOGENESIS CENTERS OVER THE PLAINS WILL INDUCE A
SOUTHEAST SFC BREEZE TODAY OF 10 TO 20 MPH BY AFTERNOON.
LOOKING UPSTREAM ON THE 00Z UA ANALYSIS...SOUTH-SOUTHEAST LLJ FETCH
WILL MAINTAIN H85 MB TEMP VALUES OF AT LEAST +13 C AND WITH DECENT
MIXING UP CLOSE TO THAT LEVEL...WILL MAKE FOR A UNSEASONABLY WARM
OCTOBER DAY. THE REGION WILL CONTINUE TO EXPERIENCE WAVES OF CI AND
POSSIBLY SOME AC TODAY WHICH WILL FILTER THE INSOLATION
SUBSTANTIALLY AT TIMES...BUT STILL EXPECT WIDESPREAD UPPER 70S TO
AROUND 80 EXCEPT THE FAR NORTH AND NORTHEASTERN CWA WHICH MAY BE
HELD IN THE MID 70S WITH EASTERLY FETCH FROM SOUTHEAST WI.
TONIGHT...AGREE WITH THE 00Z RUN GFS...ECMWF AND UKMET WHICH
MAINTAIN A MORE OPEN AND THUS PROGRESSIVE L/W TROF AXIS ARRIVAL
OVER THE MO RVR VALLEY BY 12Z TUE...AS OPPOSED TO THE SLOWER NAM AND
NGM WHICH TRY TO CUT-OFF UPPER LOW IN TROF BASE TOO QUICKLY WHICH
ALLOWS UPPER RIDGING TO LINGER LONGER AND THESE MODELS ARE DRY FOR
THE LOCAL AREA THROUGH TUE MORNING. THE OTHER FAVORED SOLUTIONS
OF THE MORE PROGRESSIVE TROF EFFECTIVELY SPILL DIFFLUENT
SOUTHWESTERLY MID AND UPPER LEVEL FLOW ACRS THE REGION LATER
TONIGHT AND SHUTTLE A LEAD VORT OVERHEAD. THIS COMBINED WITH A
SOUTHERLY 30-40 KT LLJ WARM MOIST CONVEYOR UP OFF THE WESTERN GULF
SUPPORTS MODERATE TO LIKELY CHC POPS ALREADY ADVERTISED WEST OF THE
MS RVR. ADEQUATE MOISTURE RETURN FURTHER EAST OF THAT ACRS IL STILL
IN QUESTION FOR TONIGHT. INITIAL INSTABILITY ALSO MARGINAL FOR MUCH
THUNDER UNTIL LATER TUE...AND WILL JUST ADVERTISE ISOLATED OR WDLY
SCTRD THUNDER WITH SHOWERS FOR NOW. WITH CONTINUED SOUTHEAST
BREEZE...CLOUD COVER AND INCREASING SFC DPTS...OVERNIGHT LOWS WILL
BE ON THE MILD SIDE FOR THIS TIME OF YEAR WITH WIDESPREAD MID TO
UPPER 50S...AND SOME LOCATIONS NOT DIPPING OUT OF THE 60S. ..12..
.LONG TERM...TUESDAY THROUGH NEXT SUNDAY...
TUESDAY THROUGH WEDNESDAY ARE MARKED BY THE PASSAGE OF THE UPPER
LEVEL TROUGH AND SURFACE INVERTED TROUGH. MODELS ARE STILL HAVING
SIGNIFICANT DIFFICULTIES WITH THIS FEATURE...WITH THE ECMWF AND GFS
SHOWING A MORE PROGRESSIVE PATTERN...AND THE NAM A MUCH SLOWER
PATTERN. BY WEDNESDAY THE NAM SPEEDS UP...BUT THE GFS SLOWS DOWN
WITH A CUT OFF LOW THAT FORMS TO THE SOUTHEAST. THE ECMWF APPEARS
TO BE THE MOST CONSISTENT IN KEEPING A MORE OPEN WAVE SOLUTION...AS
CAN BE SEEN IN D-PROG/D-T DISPLAYS. OTHER MODELS SEEM TO TREND
TOWARDS THIS SOLUTION...AND THEN VEER AWAY FOR OTHER TIME FRAMES.
HAVE MAINLY USED THE ECMWF THIS MORNING...WITH THE GREATEST POPS IN
TUESDAY AND TUESDAY EVENING...EXITING QUICKLY TO THE EAST ON
WEDNESDAY FOR A DRY FORECAST WEDNESDAY NIGHT THROUGH MOST OF FRIDAY.
TEMPERATURES THROUGH THE PERIOD WILL BE NEAR OR JUST BELOW NORMAL ON
TUESDAY WITH THE PRECIPITATION IN THE AREA...AND SITTING NEAR NORMAL
FOR WEDNESDAY THROUGH FRIDAY AS THERE JUST IS NOT A HUGE TEMPERATURE
DIFFERENCE TO THE AIRMASS BEHIND THIS SYSTEM. ANOTHER INTERESTING
SYSTEM DUE TO DIVE IN HERE LATE NEXT WEEKEND...BUT THERE ARE
SIGNIFICANT MODEL DIFFERENCES AND HAVE NOT YET MADE ANY CHANGES TO
THE FORECAST. TEMPERATURES COULD BE WELL ABOVE NORMAL SATURDAY AHEAD
OF THIS SYSTEM...BEFORE A DAY OR TWO OF RAINFALL MOVES THROUGH
...AND THEN COLDER EARLY NEXT WEEK. WE WILL HAVE TO WAIT AND SEE
WHAT THE TRENDS ARE. ..LE..
&&
.AVIATION...
A MAINLY VFR TAF PERIOD WITH PERIODS OF THICK CI TODAY AT 25K FT...
BUT AC WILL THICKEN FROM THE SOUTHWEST AFTER 00Z. APPROACHING
SHOWERS/ISOLATED THUNDERSTORMS AND POSSIBLY MVFR CIGS WILL ENCROACH
UPON THE CID AND BRL TERMINALS AFTER 06Z. SOUTHEAST SFC WINDS FROM
110-140 DEGREES TODAY MAY GUST TO OVER 20 KTS FROM 17Z-21Z THIS
AFTERNOON WITH DECENT MIXING UP TO THE H85 MB LEVEL. ..12..
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
12/LE
