Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 260521
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1121 PM CST TUE NOV 25 2014

.UPDATE...
ISSUED AT 536 PM CST TUE NOV 25 2014

WHILE THE UPCOMING CLOUDS AND WARM ADVECTION SHOULD ARRIVE ON
SCHEDULE IN A FEW HOURS...THE EVENING CLEAR SKIES AND CALM WINDS
HAVE ALREADY ALLOWED TEMPERATURES TO FALL BELOW FORECAST MINS.
THUS...I HAVE UPDATED THE MINS ABOUT 4 DEGREES LOWER IN MOST
CASES...AND HAVE UPDATED THE HOURLY TEMP GRIDS TO ACCOUNT FOR
RISING OVERNIGHT TEMPS AFTER MIDNIGHT.
ERVIN

&&

.SYNOPSIS...
ISSUED AT 326 PM CST TUE NOV 25 2014

QUIET DAY TODAY WITH THE MIDWEST IN BETWEEN WEATHER SYSTEMS. VISIBLE
SATELLITE IMAGERY HIGHLIGHTS SNOW COVER ACROSS EASTERN IOWA BUT BARE
GROUND TO THE WEST AND NORTHWEST. A WEAK SFC-850 MB BAROCLINIC ZONE
WILL SET UP RIGHT ALONG THE SNOW COVER GRADIENT FOR TONIGHT AND
TOMORROW. AN ALBERTA CLIPPER WILL THEN RIDE THIS BAROCLINIC ZONE
SOUTHEASTWARD BRINGING LIGHT SNOW TO THE DVN CWA ON WEDNESDAY.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 326 PM CST TUE NOV 25 2014

LIGHT SNOW WILL MOVE INTO THE FAR WESTERN CWA MAINLY AFTER 11Z OR
12Z/WED. NEGATIVE OMEGA IN THE 700-500 MB LAYER IS MAXIMIZED OVER
THE WESTERN CWA DURING THE MORNING AND THE CENTRAL CWA DURING THE
AFTN. THE CLIPPER WILL PROVIDE 700 MB WAA AND A PERIOD OF DCVA TO
KEEP UVV GOING THROUGH THE DAY. THE MAIN VORTICITY MAX AND SFC LOW
PRESSURE CENTER WILL CONTINUE TO DIVE SOUTHEASTWARD INTO THE
EVENING...TAKING THE BETTER DYNAMICS WITH IT. AS A RESULT...SNOW
ACCUMULATIONS WILL BE LIGHTEST IN THE NORTHEAST CWA.

SFC TEMPS MAY BECOME PROBLEMATIC DURING THE AFTN ACROSS THE SE CWA
BUT I BELIEVE ONGOING SNOW SHOULD HOLD TEMPS DOWN IN THE LOWER 30S
PRIOR TO THE EARLY/MID AFTN. TOP DOWN THERMAL ANALYSIS SUPPORTS ALL
SNOW ACROSS THE AREA WITH ONLY A VERY SMALL ABOVE FREEZING LAYER
NEAR THE SFC DURING THE AFTN. EVAPORATIVE COOLING WILL HOLD TEMPS
NEAR FREEZING UNTIL THE SNOW INTENSITY DECREASES. THE SREF DOES SHOW
THE SFC WET BULB 32 F ISOTHERM REACHING NORTH OF BURLINGTON BY
21Z/WED BUT THINK MOST OF THE STEADIER SNOW WILL HAVE ALREADY OCCURRED.

MID/LOWER THERMAL PROFILES ARE RELATIVELY MILD IN THAT TEMPS ARE
WARMER THAN -12 C WHICH MEANS THE DGZ IS ONLY SATURATED WAY UP
AROUND 700 MB. WITH THE DGZ DEPTH LESS THAN 100 MB AND SFC TEMPS
NEAR OR ABOVE 30 F...AVG SLRS AROUND 12:1 SEEM LIKE A GOOD BET.

BY 00Z/THU...SNOW ACCUMULATIONS WILL RANGE FROM VIRTUALLY NOTHING IN
THE FREEPORT AREA TO AROUND 1 INCH IN THE QUAD CITIES TO 2-2.5
INCHES W/SW OF CEDAR RAPIDS. SINCE WINDS WILL AVERAGE LESS THAN 20
MPH AND SNOW ACCUMULATIONS ARE FORECAST TO BE UNDER 3 INCHES FELT AN
ADVISORY WAS NOT NECESSARY.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 326 PM CST TUE NOV 25 2014

FORECAST FOCUS ON A ROLLER-COASTER RIDE OF TEMPERATURES AND MAINLY
DRY THROUGH THIS EXTENDED PERIOD.

WEDNESDAY NIGHT...WILL WALK OUT ANY LINGERING LIGHT SNOW WEDNESDAY
EVENING AS THE CLIPPER SYSTEM MOVES SOUTHEAST OF THE CWA. ADDITIONAL
ACCUMULATIONS IN THE EVENING SHOULD BE UP TO ONE-HALF INCH. LATER
WEDNESDAY NIGHT CANADIAN HIGH PRESSURE WILL BE BUILDING INTO THE CWA
WITH DECREASING CLOUDS IN THE NW CWA. MINIMUM TEMPERATURES WILL
RANGE FROM 11 AT INDEPENDENCE TO 22 AT MACOMB AND PRINCETON IL.

THANKSGIVING DAY...COLD BUT QUIET AS HIGH PRESSURE WILL THEN SETTLE
INTO THE AREA PROVIDING PLENTY OF SUNSHINE. MAXIMUM TEMPERATURES
WILL RANGE FROM THE UPPER TEENS NW TO THE UPPER 20S SE.

THURSDAY NIGHT AND FRIDAY...HIGH PRESSURE SHIFTS TO OUR EAST WITH
INCREASING WARM AIR ADVECTION MID/HIGH CLOUDS ADVANCING INTO THE CWA
THURSDAY NIGHT. ANOTHER ALBERTA CLIPPER ORGANIZES AND TRACKS TO
NORTHEAST MT AS ZONAL FLOW ALOFT AND SOUTHWEST SURFACE WINDS RETURN.
A STRONG WARM FRONT QUICKLY LIFTS ACROSS THE CWA BUT THE MAJORITY OF
THE MODELS KEEP THE WARM SECTOR DRY WITH THE SATURATION OCCURRING IN
MN AND WI. THE ECMWF DOES TRY TO PAINT SOME VERY LIGHT QPF IN OUR
FAR NORTHERN CWA SO WILL MAINTAIN THE SLIGHT POPS FRIDAY MORNING.
WARMER ON FRIDAY WITH HIGHS IN THE MID 30S NORTH TO MID 40S SOUTH.

THIS WEEKEND...EVEN WARMER ON SATURDAY AHEAD OF A STRONG COLD FRONT
DROPPING SOUTHWARD INTO THE NORTHERN PLAINS AND UPPER MIDWEST...AS
THE CLIPPER TRACKS TO NEAR JAMES BAY. HIGHS SHOULD PUSH WELL INTO
THE 40S TO LOWER 50S...BUT THIS MAY NOT BE WARM ENOUGH FOR LATER
SHIFTS TO RE-EVALUATE...DEPENDING ON IF ANY SNOW COVER. COLD FRONT
SWEEPS ACROSS THE CWA BY SUNDAY WITH COLDER WEATHER AGAIN ON
SUNDAY...WITH HIGHS IN THE MID 20S NW TO UPPER 30S SE IN THE MORNING.

EARLY NEXT WEEK...STILL COLD ON MONDAY AS A 1044MB HIGH SETTLES INTO
THE CWA. HOWEVER...THIS HIGH PRESSURE SHIFTS TO THE EAST BY TUESDAY
WITH TEMPERATURES IN THE 40S TO LOWER 50S RETURNING. THE GFS HINTS
AT SOME LIGHT RAIN IN THE STRONG RETURN FLOW BUT THE ECMWF IS DRY.
FOR NOW WILL HAVE ONLY SMALL POPS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1118 PM CST TUE NOV 25 2014

CLEAR SKIES AND HIGH PRESSURE WITH CALM WINDS WILL QUICKLY GIVE
WAY TO CLOUDY SKIES WITH CIGS ABOVE 3000 FT BY 14Z. WINDS WILL BECOME
SOUTHEAST AROUND 8 KTS TOWARD 06Z TONIGHT...AND BY MORNING EAST TO
SOUTHEAST WINDS OF 8 TO 15 KTS WILL BE FOUND OVER IOWA. SNOW WILL
SPREAD EAST AFTER 14Z INTO EASTERN IOWA...BUT SHOULD REMAIN WEST
OF TERMINALS ALONG THE MISSISSIPPI RIVER THROUGH LATE MORNING.
LIGHT SNOW WILL FALL WITH 2 TO 4 MILE VISIBILITIES ALL DAY AT
CID...BUT FARTHER EAST...MUCH BETTER VISIBILITIES ARE FORECAST AS
SNOW WILL BE VERY LIGHT. LIGHT SNOW WITH MVFR CIGS WILL LIKELY
LINGER WELL INTO WEDNESDAY EVENING.

ERVIN

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&

$$

UPDATE...ERVIN
SYNOPSIS...UTTECH
SHORT TERM...UTTECH
LONG TERM...HAASE
AVIATION...ERVIN





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