359
FXUS63 KDVN 082124
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
323 PM CST SUN NOV 8 2009
SYNOPSIS
WARM FRONT SURGED QUICKLY NORTH OF THE CWA THIS MORNING WITH MIXING.
THIS AFTN CWA SITS FIRMLY ENTRENCHED IN WARM SECTOR WITH GUSTY
SOUTHERLY WINDS AND FULL SOLAR INSOLATION RESULTING IN WIDESPREAD
TEMPS IN THE L/M 70S... WHICH IS ABOUT 20-25 DEGS ABOVE NORMAL
FOR TIME OF YEAR... AND ALSO AROUND 5 DEGS OR SO OFF RECORD HIGHS
AT CWA ASOS CLIMATE SITES. AT 20Z WEAK SFC LOW WAS POSITIONED IN
SOUTHWEST MN... WITH WARM FRONT DRAPED ACROSS SOUTHERN MN
AND SOUTHERN WHILE COLD FRONT TRAILS THROUGH EASTERN NE INTO CENTRAL
KS. DECENT LOW LEVEL MOISTURE POOLING AHEAD OF FRONT WITH SFC
DEWPTS IN THE MID 50S. DEEPER MOISTURE THOUGH LACKING AND HANGING
BACK ACROSS WESTERN TX WHERE H85 DEWPTS WERE IN THE RANGE OF 10-12C.
AS RESULT WITH FORCING LIMITED ATTIM COLD FRONT IS DRY. SUBJECTIVE
UPPER AIR ANALYSIS AND WATER VAPOR LOOP SHOWS SHORTWAVE LIFTING
THROUGH WESTERN TX. SOUTHWESTERLY FLOW DOMINATES CENTRAL CONUS WITH
130 KT H3 JET PASSING THROUGH MN WITH LIFT FROM RRQ... MID LEVEL
FRONTOGENESIS AND WEAK SHORTWAVE ASSISTING BANDED LIGHT PCPN SHIELD
LIFTING ACROSS EASTERN DAKOTAS INTO ARROWHEAD OF MN. LAST BUT NOT
LEAST IS HURRICANE IDA WHICH EARLY AFTN WAS PASSING BETWEEN THE
YUCATAN PENINSULA AND CUBA.
..MCCLURE..
SHORT TERM...TONIGHT AND MONDAY
MAIN FCST CHALLENGE IS PCPN CHCS. SFC FRONT TO CONTINUE SLIDING
EAST AND EXPECTED TO PASS ACROSS CWA LATE TNGT AND MON AM...
ROUGHLY IN THE 09Z-15Z TIMEFRAME. MUCH OF E/SE HALF OR SO
OF THE CWA TO REMAIN IN PRE-FRONTAL WARM SECTOR THROUGH THE NIGHT
WITH S/SW WINDS AND COUPLED WITH INCREASE IN CLOUDS HAVE GONE
AT OR ABOVE WARMEST GUIDANCE THIS AREA... WHILE SIDING NEAR BLEND
IN THE NORTHWEST.
AS FOR PCPN... WITH PRE-FRONTAL MOISTURE SHALLOW... AND LACKING
COHERENT TRIGGER OR FORCING MECHANISM ASIDE FROM WEAK FRONTAL
CONVERGENCE... ANTICIPATE PCPN IN OUR CWA TO BE POST FRONTAL FORCED
NEAR THE H85 BOUNDARY. 12Z RUN OF NAM HAD SUGGESTED SOME POTENTIAL
FOR CONVECTION ACROSS S/E SECTIONS OVRNGT WITHIN ZONE OF ENHANCED
WARM ADVECTION ATTRIBUTED TO THE MODEL DEVELOPMENT OF WEAK SFC WAVE
ALONG BOUNDARY. HOWEVER...18Z NAM NO LONGER SHOWING THIS WEAK SFC
LOW AND SUBSEQUENT RAMPING UP OF WARM ADVECTION...WHICH THE LACK OF
SUCH WAVE IS SUPPORTED BY OTHER MODELS. AS RESULT OF ALL THIS BELIEVE
PCPN POTENTIAL TOO LIMITED FOR MENTION TNGT. DEPTH OF COLD AIR
PER NAM AND GFS BUFR SOUNDINGS TO NEAR H85 AT KDBQ COUPLED WITH
DRY MID LEVELS PRECLUDES PCPN POTENTIAL FAR NORTH DURING DAY ON MON.
HAVE ADJUSTED POPS TO FOCUS PROXIMITY OF H85 FRONTAL ZONE... OR
ROUGHLY FROM HWY 30 ON SOUTH... WITH HIGHEST POPS ALBEIT CHC ACROSS
THE SOUTH. NAM AND GFS TSECTS SHOW SATURATION AND FORCING COMING
TOGETHER FOR GREATER LIKELIHOOD OF PCPN AFT 00Z TUE IN THE SOUTH.
HIGH TEMPS MON WILL BE COOLER MOST AREAS BY 10-15+ DEGS... AND IN THE
RANGE OF AROUND 60 NW TO M60S SE... BUT STILL ABOVE NORMAL. A SURE
SIGN OF JUST HOW WARM IT HAS BEEN AROUND HERE IN RECENT DAYS.
..MCCLURE..
LONG TERM...MONDAY NIGHT THROUGH NEXT SUNDAY
INITIAL FOCUS IS RAIN CHANCES MONDAY NIGHT. REMAINDER OF WEEK LOOKS
DRY WITH CONTINUED ABOVE NORMAL TEMPERATURES IN A MOSTLY ZONAL FLOW.
MODELS THEN TRANSITION TO A MORE AMPLIFIED UPPER PATTERN NEXT
WEEKEND.
SHORTWAVE IN NORTHERN STREAM WESTERLIES IS PROGGED TO SEND A WEAK
WAVE ALONG THE H8 FRONT PROGGED TO BE STALLED W-E ALONG THE IA/MO
BORDER TUE NIGHT. SHORT TERM MODELS HAVE ISENTROPIC LIFT STRONGEST
ACROSS THE SOUTH...WHILE MID LEVEL QG FORCING AND UPPER LEVEL
DIVERGENCE IS FOCUSED FURTHER NORTH FROM E CENTRAL IA INTO NRN IL
LATE MON NIGHT INTO EARLY TUE MORNING. THIS SYSTEM IS SHOWN TAPPING
INTO THE AREA OF H8 MOISTURE LOCATED OVER W TX INTO THE OK PANHANDLE
THIS MORNING. PW VALUES EXCEED 1 INCH...NEARLY 200 PERCENT OF
NORMAL...ACROSS THE SOUTH BY MON EVENING. THIS SHOULD RESULT IN
SEVERAL HOURS OF LIGHT TO MODERATE RAIN OVER THE SOUTH AND HAVE
LIKELY POPS WITH QPF AS HIGH AS .25 TO .5 INCHES FOR THE EVENT.
FURTHER NORTH...INFLUX OF DRY AIR AROUND BASE OF SURFACE HIGH OVER
MN AND WI WILL LIKELY RESULT IN SHARP CUTOFF TO TRACE AMOUNTS IN THE
NORTH ALONG THE HIGHWAY 20 CORRIDOR...AND HAVE POPS TAPERING FROM
SLIGHT TO NON MENTIONABLE THROUGH THE NIGHT.
TUESDAY...WITH SLIGHTLY SLOWER TIMING OF THE SYSTEM KEEPING MID
LEVEL FORCING GOING A BIT LATER THAN EARLIER RUNS...HAVE ADDED LOW
CHANCE POP IN THE SOUTHEAST IN THE MORNING. HIGH PRESSURE TO THE
NORTH BUILDING SOUTHEAST...AND STRONG MID LEVEL SHORTWAVE
RIDGING/SUBSIDENCE SHOULD THEN BRING CLEARING DURING THE DAY. LOW LEVEL
NORTHEAST FLOW MIXING TO AT LEAST 925 MB SHOULD THEN WARM
TEMPERATURES BACK INTO THE MID 50S TO AROUND 60. THE SURFACE RIDGE
AXIS THEN PASSES OVERHEAD TUE NIGHT. LOCAL TECHNIQUE BASED ON H8
TEMPERATURES AND SYNOPTIC SETUP SUPPORTS MINS NEAR TO JUST BELOW
COOLER GFS MOS GUIDANCE FROM THE LOWER 30S NORTH TO UPPER 30S SOUTH
AND SOUTHWEST.
REMAINDER OF THE WEEK KEPT DRY WITH HIGHS GENERALLY IN THE 50S TO
LOW 60S AND LOWS IN THE UPPER 30S TO LOWER 40S...STILL SLIGHTLY
ABOVE CLIMO. ECMWF AND GFS HAVE A SURFACE CYCLONE DEVELOPING LEE OF
THE ROCKIES FRI MORNING...THEN TRACKING EAST OR NORTHEAST OVER THE
WEEKEND TO INFLUENCE THE REGION. HOWEVER...LARGE INCONSISTENCIES
AMONG THESE AND OTHER MEDIUM RANGE MODELS...BOTH FROM RUN TO RUN AND
FROM MODEL TO MODEL...LEADS TO LOW CONFIDENCE IN THE DETAILS.
FOR NOW...KEPT FORECAST CLOSE TO HPC COMPROMISE...WITH SLIGHT CHANCE
POPS FROM FRI NIGHT THROUGH SAT AND SUN AND TEMPERATURES MAINLY IN
THE 40S AND 50S THROUGHOUT. MOST LIKELY AT LEAST SEVERAL OF THESE
PERIODS WILL REMAIN DRY AND IF AREA GETS IN WARM SECTOR OF A MORE
NRLY TRACK...ONE OF THESE DAYS COULD BE CONSIDERABLY WARMER AS WELL.
..SHEETS..
AVIATION
COLD FRONT OVER EASTERN NE WILL MOVE EAST AND PASS OVER THE TERMINALS
BETWEEN 09Z-15Z. AHEAD OF FRONT EXPECT VFR CONDITIONS WITH SOUTH
WINDS AROUND 10 KTS WITH SOME GUSTS THIS EVE. SHALLOW LOW LEVEL
MOISTURE AND LACK OF SUFFICIENT TRIGGER TO PRECLUDE ANY MENTION OF
PCPN AT TERMINALS. HOWEVER... LOW LEVEL MOISTURE POOLING AHEAD OF
FRONT AND DIMINISHING WINDS SHOULD ALLOW FOR SOME FOG AND LOWER
CLOUDS TO DEVELOP... AS WAS OBSERVED ACROSS PORTIONS OF KS EARLY
THIS MORNING. HAVE GONE WITH A PERIOD OF LOWER MVFR CIGS AND VSBYS
WITHIN FEW HOURS PRIOR TO AND AFTER FRONTAL PASSAGE... THEN
GRADUALLY IMPROVE TO VFR BY MID TO LATE AM WITH NORTHERLY WINDS
INCREASING AROUND 10 KTS. ..MCCLURE..
DVN WATCHES/WARNINGS/ADVISORIES
IA...NONE.
IL...NONE.
MO...NONE.
MCCLURE/SHEETS
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