FXUS63 KDVN 060948
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
348 AM CST SUN DEC 6 2009
.SYNOPSIS...
00Z UA ANALYSIS HAS A STRONG NORTHERN STREAM SHORTWAVE WITH A TROF
RUNNING FROM LAKE SUPERIOR INTO IOWA. A DEVELOPING WINTER STORM WAS
IN THE OKLAHOMA PANHANDLE WITH A MINIMAL LLJ RUNNING FROM THE GULF
NORTHWARD INTO TEXAS AND OKLAHOMA. SATELLITE TRENDS SHOW HIGH LEVEL
CI/CS STREAMING INTO THE GREAT LAKES WITH LOWER CLOUDS ASSOCIATED
WITH THE TROF ACROSS WISCONSIN. 06Z SFC ANALYSIS HAS A WEAK LOW NEAR
KLSE WITH A TRAILING COLD FRONT ACROSS IOWA AND INTO CENTRAL KANSAS.
THE DEVELOPING WINTER STORM HAD A SFC LOW WEST OF KGUY WITH A TROF
DROPPING SOUTHEAST INTO TEXAS. DEW POINTS WERE IN THE TEENS ACROSS
THE AREA WITH 20 DEWPOINTS POOLING ALONG THE COLD FRONT AND 30 DEW
POINTS APPROACHING THE RED RIVER.
&&
.SHORT TERM...TODAY AND TONIGHT...
QUIET CONDITIONS THIS MORNING AND INTO EARLY AFTERNOON. BY LATE
AFTERNOON TOP DOWN SATURATION WILL HAVE OCCURRED ACROSS ABOUT THE
NORTHWEST THIRD OF THE CWFA TO ALLOW -SN TO DEVELOP. CONDENSATION
PRESSURE DEFICITS REMAIN QUITE HIGH OVER THE REMAINDER OF THE AREA.
ONCE PRECIP BREAKS OUT THIS AFTERNOON...TEMPERATURES SHOULD DROP
OVER THE NORTHWEST THIRD. AT THE VERY WORST...A LIGHT DUSTING SHOULD
BE SEEN BY 00Z.
TONIGHT...THE LOWER ATMOSPHERE COMPLETES SATURATION BY 06Z ACROSS
THE ENTIRE AREA PER CONDENSATION PRESSURE DEFICITS. SNOW SHOULD
EXPAND OR QUICKLY BREAK OUT DURING THE EVENING HOURS ACROSS THE
REMAINDER OF THE CWFA. BASED ON THE OVERALL FORCING...THE NORTHWEST
40 PERCENT OF THE CWFA WILL HAVE THE HIGHEST AMOUNTS OF 2-3 INCHES
BY SUNRISE. THE FAR EAST/SOUTHEAST PARTS OF THE CWFA SHOULD SEE LESS
THAN AN INCH WITH 1-1.5 INCHES FROM ABOUT KOTM TO KSQI.
I DEBATED WHETHER OR NOT TO ISSUE HEADLINES FOR THIS EVENT. PROS TO
DO SO WOULD BE THE FIRST WIDESPREAD SNOW ACCUMULATION...AN EARLY
SEASON EVENT...AND POTENTIAL FOR SLICK ROADS WITH PAVEMENT
TEMPERATURES AROUND FREEZING. THE SIGNIFICANT CON IS THAT THIS EVENT
WILL BE GREATLY OVERSHADOWED BY THE MAJOR WINTER STORM TUESDAY INTO
WEDNESDAY. THEREFORE...HAVE OPTED TO NOT ISSUE ANY HEADLINES IN
ORDER TO AVOID ANY CONFUSION AND TO AVOID DOWNPLAYING THE
SIGNIFICANCE OF THE HIGH IMPACTS WITH THE NEXT STORM.
...08...
.LONG TERM...MONDAY THROUGH NEXT SATURDAY...
...HIGH IMPACT...POTENTIALLY CRIPPLING WINTER STORM TUE/WED THE
FORECAST CHALLENGE...
OVERALL INITIALIZATION AND VERIFICATION ABOVE AVERAGE WITH SOME
RESOLUTION OF LATENT HEAT CONVECTIVE FEEDBACK OF SOUTH PLAINS STORM.
THIS SUPPORTS A RAPIDLY DEEPENING STORM AND AN EXTREME WINTER STORM
EVENT FOR FORECAST AREA. USED BLEND OF GEM-NHEM AND HI-RES ECMWF
WITH FORCING FROM 18Z 80 KM NAM-WRF. BEYOND DAY 3...USED BLEND HI-
RES ECMWF AND GEM-NHEM WITH SOME FORCING FROM GFS.
MONDAY...NEARLY STEADY TEMPS IN UPPER 20S TO LOWER 30S WITH LINGERING
FLURRIES AND LIGHT SNOW INTO THE EARLY AFTERNOON. LOTS OF LOW CLOUDS
SUGGESTED WITH PATCHY FOG POSSIBLE INTO MONDAY NIGHT.
MONDAY NIGHT...LOTS OF LOW CLOUDS SUGGEST KEEPING LOWS ABOVE
GUIDANCE. ENOUGH LOW LEVEL CONVERGENCE AHEAD OF APPROACHING WINTER
STORM SUPPORTS FLURRIES. LATER SHIFTS MAY NEED TO ADD PATCHY FOG
DUE TO LIGHT EAST WINDS AND MOIST LOW LEVELS.
TUESDAY AND WEDNESDAY...EXTREME WINTER STORM...POTENTIALLY CRIPPLING
WITH NEAR HISTORIC POTENTIAL. THIS WILL BE DUE TO A COMBINATION OF
HEAVY SNOW...HIGH WINDS...PRODUCING BLIZZARD TO NEAR BLIZZARD
CONDITIONS TUESDAY NIGHT AND ESPECIALLY WEDNESDAY. STORM EVENT HEAVY
SNOW TOTALS OF 6 TO 12 PLUS INCHES SUGGESTED WITH LOCALLY HIGHER
AMOUNTS POSSIBLE.
TUESDAY...HAVE UPPED POPS WITH SNOW OVERSPREADING ENTIRE REGION
BETWEEN MID MORNING AND MID AFTERNOON. SLEET MAY MIX WITH SNOW
SOUTH OF A PRINCETON TO GALESBURG TO KEOSAUQUA LINE. NORTHEAST
WINDS OF 10 TO 20 MPH SHOULD NOT POSE A MAJOR BLOWING AND DRIFTING
CONCERN UNTIL TUESDAY NIGHT.
TUESDAY NIGHT...SNOW...HEAVY AT TIMES WITH SOME SLEET FAR SE IN THE
EVENING WITH WINDS INCREASING AFTER MIDNIGHT TO 20 TO 35+ MPH FROM
NW TO SE WITH AREAS OF BLOWING SNOW. TRAVEL WILL BECOME EXTREMELY
DIFFICULT IF NOT IMPOSSIBLE BY DAYBREAK WITH THUNDER-SNOW SUGGESTED
OVER MOST LOCATIONS. SNOWFALL RATES OF 1 TO 2 INCHES AN HOUR AND
STRONG WINDS TO RESULT IN NEAR WHITEOUT CONDITIONS COMMON BY THE
OVERNIGHT HOURS. TEMPERATURES WILL BEGIN TO RAPIDLY FALL TOWARD
DAYBREAK.
WEDNESDAY...PROLONGED BLIZZARD CONDITIONS APPEAR LIKELY OVER LARGE
AREAS ALONG AND WEST OF THE MISSISSIPPI RIVER. THIS DUE TO CONTINUED
SNOW...HEAVY AT TIMES IN THE MORNING...DIMINISHING TO FLURRIES BY
AFTERNOON. ALL STUDIES SHOW VERY STRONG WINDS OF 30 TO 50 MPH WITH
SOME GUSTS NEAR TO POSSIBLY OVER 60 MPH SUGGESTED. THIS WILL RESULT
IN NEAR WHITEOUT CONDITIONS CAUSING IMPOSSIBLE TRAVEL CONDITIONS MOST
OF THE DAY WEDNESDAY. THESE HIGH WIND SPEEDS LIKELY WOULD ALSO CAUSE
SIGNIFICANT...PROLONGED AND WIDESPREAD POWER OUTAGES. SNOW DRIFTS OF
3 TO OVER 6 FEET DEEP WILL BE COMMON BY LATE AFTERNOON. TEMPERATURES
WILL FALL INTO THE TEENS TO LOWER 20S WITH EXTREMELY LOW WIND CHILLS.
WEDNESDAY NIGHT...WINDS TO DECREASE TO 10 TO 20 MPH BY MIDNIGHT BUT
DEEP DRIFTS MAY KEEP MOST ROADS CLOSED. HAVE TRIMMED LOWS AND
WITH CLEARING SKIES AND DEEP SNOW COVER...MINS BELOW ZERO APPEAR
PLAUSIBLE.
THURSDAY...MINOR CHANGES MADE WITH HIGHS IN THE TEENS TO LOWER 20S.
INCREASING CLOUDS THURSDAY NIGHT SHOULD LIMIT LOWS AHEAD OF WEAK
DISTURBANCE.
FRIDAY AND SATURDAY..NO CHANGES MADE. LARGE DISCREPANCIES SUGGESTED
WITH NEXT SYSTEM.
WILL SUGGEST IF TRENDS CONTINUE AS APPEARS VERY LIKELY...DAY SHIFT
SHOULD ISSUE A BLIZZARD WATCH OVER AT LEAST WESTERN 1/2 TO 2/3 AREA
TUESDAY AND WEDNESDAY. WILL USE HEADLINE FORM OF HWO PRODUCT AND ALSO
FOR WEB PAGE. THIS STORM MAY BE A ONCE IN DECADE OR MORE EVENT...ALL
IMPACTED PARTIES SHOULD TAKE THE UTMOST PREPARATIONS. ..NICHOLS..
&&
.AVIATION...
VFR WX EXPECTED THROUGH 18Z/06. 18Z-21Z CONDITIONS TO SLOWLY
DETERIORATE AS TOP DOWN SATURATION OCCURS. AFT 21Z...SN TO BREAK OUT
AFFECTING KCID FIRST AND THEN KDBQ. CIGS EXPECT TO EVENTUALLY DROP
TO 3KFT WITH 1KFT CIGS OR LOWER DEVELOPING IN THE 00Z/07 TO 06Z/07
TIME FRAME WITH VSBYS DROPPING TO 1SM OR LESS. SIMILAR TRENDS WILL
BE SEEN FOR KMLI/KBRL BUT WILL OCCUR ABOUT 6 HRS LATER. AFT 06Z/07
THERE IS A GOOD CHC OF CIGS BLO 1KFT AT ALL TAF SITES WITH VSBYS
NEAR 1SM OR BELOW.
...08...
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
08/NICHOLS
