FXUS63 KDVN 260908
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
308 AM CST THU NOV 26 2009
.SYNOPSIS...
A PROGRESSIVE UPPER LOW IS MOVING EAST OVER NORTHEAST IL EARLY THIS
MORNING. AS OF 2 AM...THIS CONTINUES TO CREATE A DEFORMATION ZONE
BAND OF RAIN AND SNOW FROM EASTERN IOWA...INTO SOUTHERN WI AND IL.
THANKFULLY...THE LOW LEVEL THERMAL PARAMETERS MUCH DISCUSSED IN THE
PAST 24 HOURS...WERE REALIZED TONIGHT...AS LOW LEVELS REMAIN JUST
WARM ENOUGH TO OFFSET SNOW ACCUMULATION...WITH A PROLONGED MIXED
PRECIPITATION PHASE DOMINATING THE DEFORMATION ZONE. SO FAR...ONLY
WI HAS REPORTED WET SNOW ACCUMULATIONS. HERE AT THE NWS OFFICE...WE
HAVE BEEN MIXED RAIN AND SNOW SINCE MIDNIGHT...AND RECENTLY
TRANSITIONED TO SNOW AT 215 AM. HOWEVER...LOOKING UPSTREAM...ONCE
THE PEAK INTENSITY OF THE DEFORMATION ZONE WORKS THROUGH...SITES
ONCE AGAIN TRANSITION BACK TO EITHER A MIX...OR RAIN.
&&
.SHORT TERM...TODAY AND TONIGHT...
AS WAS DISCUSSED IN PRIOR AFDS...THE MIXED PHASE HAS DOMINATED THIS
DEF ZONE EVENT...AND WITH TEMPERATURES AND DEWPOINTS HOLDING AT OR
JUST ABOVE FREEZING...IT APPEARS THERE WILL BE NO SNOW ACCUMULATION
OUTSIDE OF A FEW SHORT LIVED DUSTINGS.
TODAY AND TONIGHT ARE RATHER STRAIGHT FORWARD...THE UPPER LOW WILL
CONTINUE TO MOVE EAST...ENDING PCPN CHANCES AROUND 12Z. THOUGH
FLURRIES MAY LINGER FOR A SHORT TIME...MEASURABLE PCPN...AND ANY
SNOW LOOKS BE A VERY LOW THREAT. IN ALL...TODAY WILL BE A BRISK COLD
DAY UNDER CLOUDS THIS MORNING...WITH SOME CLEARING LATE IN THE
AFTERNOON. TONIGHT...UNDER CLEARING OR CLEAR SKIES...TEMPERATURES
WILL DIP WELL INTO THE 20S AS WINDS BECOME CALM AFTER MIDNIGHT.
...ERVIN...
.LONG TERM...FRIDAY THROUGH NEXT WEDNESDAY...
NICE WARM-UP STILL ON SCEDULE FOR FRIDAY AND SATURDAY WITH RETURN TO
A SOUTHWEST FLOW ALOFT. WITH RIDGING IN THE GULF PREVENTING ANY
MOISTURE RETURN THERE SHOULD BE PLENTY OF SUNSHINE BOTH DAYS. HAVE
RAISED TEMPS A TAD SO ENJOY THIS WHILE IT LASTS BECAUSE THIS WARM-UP
WILL BE BRIEF...AFTER ALL ITS ALMOST DECEMBER. COLD FRONT ARRIVES BY
SUNDAY AS AN UPPER TROUGH SWINGS ACROSS IN THE NORTHERN STREAM.
ECMWF/GFS/GEM DEVELOP TWO STORM SYSTEMS LATE THIS WEEKEND AND INTO
NEXT WEEK THAT EITHER STAYS SOUTHEAST OF THE DVN CWA...OR JUST
GRAZES OUR CWA. THE FIRST SYSTEM EXPECTED ABOUT SUNDAY INTO MONDAY
AND THE SECOND ABOUT THE MIDDLE OF NEXT WEEK. FOR NOW WILL MAINTAIN
THE SLIGHT TO VERY SMALL POPS FOR SUNDAY INTO MONDAY. NORTHERN
STREAM TROUGH SENDS COLDER AIR INTO THE REGION SO WILL HAVE MIX OF
RAIN AND SNOW OR ALL SNOW...BUT THIS ASSUMES WE GET GRAZED BY THIS
SYSTEM. IF LATER TRENDS SHOVE PRECIPITATION FARTHER SOUTHEAST OF THE
DVN CWA THEN LATER SHIFTS CAN REMOVE POPS.
EXACTLY HOW THE NORTHERN AND SOUTHERN STREAMS PHASE IS YET TO BE
DETERMINED SO SOMEWHAT NERVOUS HOW THIS ALL PLAYS OUT. A SHIFT TO
THE NORTH A BIT WOULD BRING A POTENTIAL SNOW STORM TO PORTIONS OF
THE CWA. THE MID WEEK EVENT IS WAY TOO FAR IN THE FUTURE TO WORRY
ABOUT THAT AT THIS POINT. HOWEVER WHAT DOES SEEM TO BE MORE CERTAIN
IS THE MODELS ADVERTISING ARCTIC AIR PLUNGING SOUTHWARD INTO THE
CENTRAL UNITED STATES BY THE END OF NEXT WEEK. THIS OCCURRING AS
DEEP TROUGH SETS UP SHOP ACROSS THE MIDWEST AND GREAT LAKES...AND
MAY STAY AWHILE. STAY TUNED.
..HAASE..
&&
.AVIATION...
LOW PRESSURE WILL CONTINUE TO MOVE AWAY FROM THE TAF SITES
TODAY...WITH SNOW ENDING PRIOR TO 12Z AT ALL SITES...ALTHOUGH A
BRIEF FLURRY MAY STILL BE POSSIBLE WITH GOOD VISIBILITIES THROUGH
MID MORNING. DESPITE THE LOW MOVING AWAY...EXTENSIVE MVFR CIGS
AROUND 2000FT WILL LINGER NEARLY ALL DAY...POSSIBLY CLEARING AT CID
BY 20Z...AND OTHER SITES AROUND 00Z. VERY EARLY THIS
EVENING...CLEAR SKIES AND UNLIMITED VISIBILITY IS EXPECTED AT ALL
SITES. ...ERVIN...
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
HAASE/ERVIN
