FXUS63 KDVN 250928
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
328 AM CST FRI DEC 25 2009
.SYNOPSIS...
COMPLEX SURFACE AND UPPER LEVEL CONDITIONS EXIST OVER THE REGION
THIS MORNING. 9Z ANALYSIS SHOWS A 986MB SURFACE LOW IN NORTH
CENTRAL MISSOURI WHICH IS DRIFTING NORTHWARD. THE WARM SECTOR HAS
PUSHED INTO THE CWA WITH EOK AT 50 DEGREES...WHILE AN INVERTED
TROUGH JUST WEST OF THE CWA SEPARATES RAIN FROM SNOW. COLD AIR IS
ROTATING AROUND THE LOW INTO CENTRAL MO AND WILL MOVE INTO THE CWA
FROM THE SOUTHWEST THROUGH THE DAY. DRIER AIR CURRENTLY WRAPPING
INTO THE UPPER LEVEL LOW IS CHARACTERIZED BY A TRANSITION FROM
STRATIFORM TO CONVECTIVE RAINFALL ON RADAR.
&&
.SHORT TERM...TODAY AND TONIGHT...
MAIN FORECAST CONCERNS ARE THE SIGNIFICANT CHANGE IN TEMPERATURES
TODAY WHICH WILL SIGNAL THE TRANSITION FROM SNOW TO RAIN.
MODEL CONSENSUS...WHICH IS IN LINE WITH CURRENT CONDITIONS...BRINGS
A SHARP PUSH OF COLDER AIR INTO THE SOUTHERN PART OF THE CWA LATE
THIS MORNING AND THE NORTHERN PART EARLY THIS AFTERNOON. RAIN WILL
CHANGE TO SNOW...WITH PERHAPS A BRIEF PERIOD OF ICE PELLETS...AS THE
COLD FRONT MOVES NORTHEAST. TEMPERATURES WILL DROP SHARPLY AND
COULD RESULT IN PONDED WATER FREEZING ON AREAS ROADS AND
SIDEWALKS. THIS WILL ALSO COMPLICATE RIVER FORECASTS AS RECENTLY
FALLEN RAIN MAY FREEZE BEFORE GETTING IN THE RIVERS.
WITH THE SURFACE AND UPPER LOW MOVING LITTLE OVERNIGHT...LIGHT
SNOW WILL CONTINUE. WHILE EVENT TOTALS COULD EXCEED ADVISORY
CRITERIA OF 3-PLUS INCHES...THIS WILL OCCUR OVER AN EXTENDED
PERIOD...THUS OPTED NOT TO GO WITH ANY HIGHLIGHTS. FLOOD WATCH
WILL ALSO BE ALLOWED TO EXPIRE AT 12Z.
.LONG TERM...SATURDAY THROUGH THURSDAY...
THE CURRENT WINTER STORM WILL CONTINUE TO DOMINATE THE WEATHER INTO
SUNDAY...AS THE GIANT OCCLUDED STORM SPINS OVER IOWA...AND DRIFTS
EAST WITH TIME. ESSENTIALLY..MODELS ARE FORECASTING THE DRY SLOT TO
BE NORTH OF...OR ALONG AND NORTH OF OUR NORTHERN BORDER SATURDAY
INTO SUNDAY MORNING. THIS POSITION SHOULD ALLOW FOR DEEP
SATURATION...AND BOUTS OF WRAP AROUND SNOW OVER THE SOUTHERN
2/3RDS...OR THE ENTIRE CWA. DESPITE THE SYSTEMS OCCLUDED STATE...THE
DYNAMICS SHOULD CONTINUE TO BE RATHER IMPRESSIVE. THUS...SNOW FALL
MAY BE MODERATE IN INTENSITY AT TIMES SATURDAY AND SATURDAY
NIGHT...ESPECIALLY ACROSS THE SOUTH 2/3RDS. ADDITIONAL AMOUNTS
DURING THIS PERIOD SHOULD RANGE FROM 1 TO 3 INCHES. RESULTING IN
STORM TOTAL SNOW ACCUMULATIONS OF 1 TO 4 INCHES FROM NORTHWEST TO
SOUTH. THE HIGHEST AMOUNTS SHOULD OCCUR IN THE CENTRAL AND
SOUTH...WHERE SATURATION REMAINS SUFFICIENT FOR SNOW PRODUCTION
THROUGHOUT THE DURATION OF THE UPPER LOWS INFLUENCE. SOME LOCATIONS
COULD REACH AROUND 5 INCHES FOR A STORM TOTAL...BUT AT THIS POINT IT
WOULD APPEAR ISOLATED AND DIFFICULT TO PREDICT. THUS...DUE TO LONG
DURATION OF GENERALLY LIGHT SNOW...WE WILL NOT ISSUE AN ADVISORY FOR
THIS EXTENDED EVENT.
TEMPERATURES WILL BE QUITE CHILLY THROUGH MONDAY...AS SHALLOW ARCTIC
AIR WRAPS OVER THE REGION. LITTLE CHANGE HAS BEEN MADE TO THESE
TEMPS FROM YESTERDAYS ISSUANCE...BEYOND LOWERING HIGHS A FEW DEGREES
AS CLOUD COVER SHOULD KEEP LOWER TO MID 20S WIDESPREAD SATURDAY
THROUGH SUNDAY...AND MID TO UPPER 20S FOR HIGHS MONDAY. LOWS SHOULD
HOLD IN THE TEENS...BUT ANY HOLES IN CLOUD COVER WOULD LIKELY RESULT
IN SINGLE DIGITS ABOVE ZERO THROUGH MONDAY MORNING.
LOOKING BEYOND...THE GFS AND ECWMF BOTH INDICATE A BROAD ISENTROPIC
LIFT SNOW FOR TUESDAY NIGHT INTO WEDNESDAY. AFTER WHICH...THE EC
DROPS A PERSISTENT COLD UPPER LOW INTO THE GREAT LAKES....VS THE GFS
CREATING NORTHWEST FLOW WITH CLIPPER ACTIVITY IN THE REGION.
...ERVIN...
&&
.AVIATION...
SLOW MOVING BUT POTENT SURFACE AND UPPER LEVEL LOW WILL CONTINUE
MOVING INTO THE AREA THROUGH TONIGHT. WIDESPREAD IFR WITH POCKETS
OF LIFR CONDITIONS CAN BE EXPECTED...PRIMARILY DUE TO CEILINGS AND
LATER...VISIBILITIES IN SNOW. RAINFALL THIS MORNING WILL CHANGE TO
SNOW LATER THIS MORNING AT BRL THEN EARLY AFTERNOON AT MLI...CID
AND DBQ. LIGHT SNOW SHOULD THEN CONTINUE OVERNIGHT.
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...FLOOD WATCH UNTIL 6 AM CST EARLY THIS MORNING FOR BENTON-
BUCHANAN-CEDAR-CLINTON-DELAWARE-DES MOINES-DUBUQUE-HENRY IA-
IOWA-JACKSON-JEFFERSON-JOHNSON-JONES-KEOKUK-LEE-LINN-LOUISA-
MUSCATINE-SCOTT-VAN BUREN-WASHINGTON.
IL...FLOOD WATCH UNTIL 6 AM CST EARLY THIS MORNING FOR BUREAU-CARROLL-
HANCOCK-HENDERSON-HENRY IL-JO DAVIESS-MCDONOUGH-MERCER-
PUTNAM-ROCK ISLAND-STEPHENSON-WARREN-WHITESIDE.
MO...FLOOD WATCH UNTIL 6 AM CST EARLY THIS MORNING FOR CLARK-SCOTLAND.
&&
$$
WOLF/ERVIN/WOLF
