FXUS63 KDVN 260910
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
310 AM CST SAT DEC 26 2009
.SYNOPSIS...
A LARGE UPPER LEVEL LOW PRESSURE SYSTEM CONTINUES TO SLOWLY MOVE
ACROSS THE UPPER MIDWEST AS BOTH SURFACE AND UPPER LEVEL WAVES
ROTATE AROUND THE SYSTEM. CURRENTLY A WAVE OVER NORTHERN IOWA AND
SURFACE TROUGH IN THE SOUTHEAST PART OF THE CWA ARE SUPPORTING AN
AREA OF LIGHT TO MODERATE SNOW ACROSS THE SOUTHERN PART OF THE CWA.
&&
.SHORT TERM...TODAY AND TONIGHT
MODELS PROG A PAIR OF UPPER LEVEL WAVES TO ROTATE ACROSS THE CWA
TODAY AND TONIGHT...AS THE SURFACE LOW PRESSURE SYSTEM GRADUALLY
MOVES ACROSS THE AREA DURING THE DAYTIME HOURS. THIS WILL SUPPORT
CONTINUED PERIODS OF LIGHT SNOW WITH MODEST ACCUMULATIONS OF A
ABOUT 1-3 INCHES OF DRY SNOW BY SUNDAY MORNING. MAX TEMPS TODAY IN
THE 20S AND LOWS OVERNIGHT IN THE TEENS LOOK ON TRACK GIVEN WHAT
VERIFIED TO OUR WEST UNDER THE UPPER LEVEL LOW YESTERDAY AND THIS
MORNING. WOLF
.LONG TERM...SUNDAY THROUGH FRIDAY...
WITH A GOOD DEPTH OF FRESH FALLEN SNOW OVER THE ENTIRE CWA TO START
THE EXTENDED PERIOD...OUR MAIN CHALLENGE WILL BE FORECASTING
TEMPERATURES THROUGH TUESDAY. IT NOW APPEARS NEARLY ALL AREAS OF
THE CWA WILL HAVE AT LEAST 2 INCHES ON THE GROUND...AND THIS SNOW IT
HIGHLY LIKELY TO REMAIN IN PLACE FOR SOME TIME. THE EXTENSIVE UPPER
LOW SHOULD MOVE OFF SUNDAY...BUT CYCLONIC FLOW SHOULD CONTINUE
THROUGH MONDAY. THIS WILL RESULT IN A CHALLENGING FORECAST FOR SKY
COVER...WITH THE LIKELIHOOD OF STRATUS PLAGUING THE AREA THROUGH
MONDAY INCREASING IN THREAT. SCATTERED SNOW SHOWERS STILL LOOK
POSSIBLE SUNDAY...MAINLY IN THE EAST AND NORTH WHERE DEEPER
SATURATION IS EXPECTED. COLD ADVECTION IS EXPECTED TO MAINLY FOCUS
TO THE EAST OF THE CWA MONDAY...BUT THIS WILL NEED TO BE WATCHED FOR
POTENTIALLY LOWERING MONDAYS HIGHS. IN THE MAIN TIME...UNDER CLOUDS
AND WITH FRESH SNOW...WE WILL UNDERCUT GUIDANCE AND FORECAST LOWER
TO MID 20S SUNDAY...AND MID TO UPPER 20S MONDAY. WITH CLOUDS SUNDAY
NIGHT...LOWS SHOULD RANGE FROM 12 TO 16 CWA WIDE. MONDAY
NIGHT...RIDGING TAKES CONTROL...AND I FIND LITTLE SUPPORT FOR
CONTINUING THE STRATUS CLOUD COVER. THIS OPENS THE DOOR FOR A CALM
AND VERY COLD NIGHT. I WILL UNDERCUT GUIDANCE AND FORECAST LOWS OF 5
TO 10 CWA WIDE. IF CONFIDENCE INCREASES ON A TOTALLY CLEAR
RADIATIONAL COOLING NIGHT...WE MAY NEED TO SHAVE ANOTHER 5 DEGREES
FROM THIS FORECAST PERIOD.
TUESDAY INTO WEDNESDAY...A DEEP WESTERN TROF IS EXPECTED TO SHIFT
OUT OF THE ROCKIES AND THROUGH THE MID SECTION OF THE COUNTRY. ALL
MODELS SUGGEST THE MAIN ENERGY WILL REMAIN WELL SOUTH...POSSIBLY
RIDING THE GULF COAST. THUS...OUR FORECAST REMAINS INTACT...WITH
CHANCE POPS FOR ISENTROPIC LIFT SNOW MAINLY WEDNESDAY...BUT I DID
ADD SOME SLIGHT CHANCE POPS SOUTH TUESDAY NIGHT TO COVER AN ONSET
PRIOR TO 12Z WEDNESDAY. AMOUNT APPEAR LIGHT AT THIS TIME...AND
SHOULD REMAIN THAT WAY UNLESS THE UPPER TROF CAN SLOW ENOUGH FOR A
STRONGER MOISTURE RETURN.
WEDNESDAY NIGHT THROUGH FRIDAY...ARCTIC AIR LOOKS TO TAKE
HOLD...WITH SOME THREAT OF FLURRIES OR LIGHT SNOW. ERVIN
&&
.AVIATION...
LUMBERING STORM SYSTEM WILL SLOWLY MOVE ACROSS THE FORECAST AREA
TODAY AND TONIGHT PRODUCING PERIODS OF LIGHT SNOW AS A PAIR OF
UPPER LEVEL ANS SURFACE TROUGHS ROTATE AROUND THE LOW. WIDESPREAD
MVFR CONDITIONS WILL PREVAIL MUCH OF THE PERIOD...WITH OCCASIONAL
PERIODS OF IFR VSBYS IN THE MORE INTENSE SNOWBANDS...WHICH ARE
EXPECTED MAINLY THIS MORNING AND AGAIN AFTER AROUND 6Z TONIGHT.
WOLF
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
WOLF/ERVIN
