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578
FXUS63 KDVN 240559
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1159 PM CST SUN NOV 23 2014

.UPDATE...
ISSUED AT 1159 PM CST SUN NOV 23 2014

MSAS SURFACE ANALYSIS AT 05Z SUGGESTED THE PRIMARY LOW PRESSURE
CENTER WAS BEGINNING TO ORGANIZE NEAR CHICAGO...FROM AN EARLY
DOUBLE LOW COMPLEX OVER IL AND INDIANA. THE DEVELOPING COLD FRONT
WAS LAGGING WELL TO THE WEST...CLOSER TO THE 850 MB TROUGH AXIS
JUST CROSSING THE FORECAST AREA ALONG THE MS RIVER. THIS
FRONT...AND POST FRONTAL SURGE OF 20 TO 30 KT WINDS WAS CLEARING
OUT THE DENSE FOG...WHICH WILL LIKELY BE PUSHED OUT OF OUR NW IL
COUNTIES BY 2 AM. AREA RADARS SHOWED WIDESPREAD RAIN AND DRIZZLE
WITH ENHANCED RAIN OVER MO CLOSER TO A STRONG VORT LIFTING
NORTHEAST OUT OF KS. LESS FOCUSED LIFT AHEAD OF THE PRIMARY UPPER
TROUGH...FROM NW MN THROUGH EASTERN NEB WAS KEEPING AN AREA OF
PRECIPITATION OVER CENTRAL IA.

SURFACE REPORTS WERE SHOWING A GRADUAL TRANSITION TO SNOW
BEGINNING TO OCCUR IN CENTRAL AND NORTHERN IA. THIS PROCESS
SHOULD TRANSLATE EAST THROUGH THE FORECAST AREA OVERNIGHT...LIKELY
TAKING ALL NIGHT TO REACH OUR EASTERN ZONES. WARM GROUND AND THE
32 DEGREE ISOTHERM STILL WELL BACK OVER NW AND WESTERN
IA...SUGGESTS LITTLE ACCUMULATION OVERNIGHT.

HAVE ADJUSTED THE FORECAST FOR THE FRONTAL TIMING...FOG TRENDS...
AND THE EAST TO WEST CHANGEOVER FROM RAIN TO SNOW OVERNIGHT WITH
A BRIEF MIX OF SLEET STILL POSSIBLE OVER THE NORTH CENTRAL AND NE
IN THE EARLY DAYLIGHT HOURS. WITH LARGEST PRESSURE RISES WELL TO
THE SOUTH IN THE SOUTHERN PLAINS...WINDS SHOULD REMAIN UNDER
ADVISORY CRITERIA.

ANALYSIS OF UPPER AIR DATA...SURFACE OBSERVATIONS...AND QUICK LOOK
AT 00Z GFS...NAM AND GEM...SUGGEST THE SURFACE LOW MOVING ACROSS
SOUTHERN LAKE MI INTO LOWER MI OVER THE NEXT SEVERAL HOURS WITH A
PERIOD OF MODERATE UPPER LEVEL FORCING FROM A MODEST UPPER JET
COUPLET AND STRONG VORT LIFTING NORTHEAST OUT OF THE MAIN UPPER
TROUGH IN A NEGATIVE TILT FASHION SUPPORTS A PERIOD OF LIGHT TO
MODERATE SNOW OVER ESPECIALLY THE NORTHEAST HALF OF THE FORECAST
AREA FROM ABOUT 12Z TO 18Z. MODEL QPF AND SNOW ACCUMS HAVE BACKED
OFF TO MORE OF A 1 TO 3 INCH RANGE...DOWN CONSIDERABLY FROM THE
PREVIOUS RUN...AND HAVE MADE MINOR DOWNWARD ADJUSTMENTS TO SNOW
TOTALS FOR MONDAY. HOWEVER...WITH STRONG WINDS ACCOMPANYING THE
SNOW...WILL KEEP THE ADVISORY GOING. BASED ON CURRENT TRENDS...
MAY NEED TO TRIM OFF SOME SOUTH AND SW COUNTIES IN THE ADVISORY WERE
SNOW TOTALS COULD BE LESS THAN 1 INCH.

&&

.SYNOPSIS...
ISSUED AT 306 PM CST SUN NOV 23 2014

A RAPIDLY DEVELOPING LOW PRESSURE SYSTEM IN THE SOUTHERN PLAINS IS
PRODUCING LOTS OF RAIN WITH AREAS OF FOG ACROSS THE UPPER MIDWEST.
ANALYSIS TRENDS SUGGEST STRONG COLD FRONT IN THE NORTHERN PLAINS TO
PHASE WITH THIS LOW LATE TONIGHT RESULTING A PERIOD OF SNOW WITH
LIGHT TO LOCALLY MODERATE SNOW TOTALS INTO MONDAY AFTERNOON AND
FALLING TEMPERATURES TO WELL BELOW NORMAL.

&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 306 PM CST SUN NOV 23 2014

SHORT TERM FORECAST CONFIDENCE ASSESSMENT...FAIR WITH OVERALL TRENDS
GOOD BUT TIMING OF TRANSITION TO SNOW AND POSSIBLE PERIOD OF SLEET
MAIN ISSUE...PLUS FOG THIS EVENING. TEMPERATURES TO FALL RAPIDLY A
COUPLE OF HOURS AFTER THE FRONT PASSES WITH ISALLOBARIC GUSTS TO
40 MPH...NEAR WIND ADVISORY CRITERIA.

TONIGHT...THIS EVENING...WIND TO LIGHTEN WITH AREAS OF FOG...LOCALLY
DENSE POSSIBLE UNTIL FRONT PASSES TOWARD MIDNIGHT INTO OVERNIGHT HOURS.
A DENSE FOG ADVISORY IS NOT LIKELY...BUT COULD BE CLOSE FOR SOME
AREAS NEAR WHERE SURFACE LOW TRACKS. RAIN TOTALS TONIGHT SHOULD BE
A TENTH OF AN INCH OR LESS MOST LOCATIONS. TEMPERATURES NEARLY STEADY
UNTIL FRONT PASSES WITH 5 TO 8 DEGREE DROPS PER HOUR EXPECTED AFTER
FRONT PASSES FOR 3 TO 4 HOURS WITH 20 TO 35 MPH WIND AND GUSTS TO
40 MPH AND ISOLATED HIGHER GUSTS NOT OUT OF QUESTION IF LOW PRESSURE
STRENGTHENS MORE THAN FORECAST. THERMAL PROFILES ARE FAVORABLE FOR
AN HOUR OR TWO OF SLEET AS RAIN TRANSITIONS TO SNOW DUE TO STRONG CAA.

MONDAY...FALLING TEMPERATURES WITH WEAK UPPER WAVE INTERACTING WITH
FRONT TO PRODUCE A 2 TO 4 HOUR PERIOD OF LIGHT TO MODERATE SNOW. SNOW
MAY INITIALLY MELT AND FREEZE WITH LOCAL TOOLS SUGGESTING 2 TO 4 INCHES
OVER AT LEAST NORTHERN 1/2 TO 2/3 AREA AND WITH STRONG WINDS...FALLING
TEMPERATURES AND FREEZING FOR BLACK ICE AND LOCALIZED DRIFTING AND
POSSIBLY LOW END BLOWING OF SNOW TOWARD END TO THE EVENT IMPACTING
VISIBILITIES. HIGHS WILL BE NEAR 8 AM FOR ALMOST ALL THE AREA WITH
25 TO 35+ MPH WINDS AND SOME GUSTS NEAR 40 MPH MAKING NEAR WIND
ADVISORY CRITERIA.

DUE TO COMBINATION OF SNOW...WIND AND CRASHING TEMPERATURES ARE REASON
FOR WINTER WEATHER ADVISORY UNTIL 6 PM MONDAY WEST AND 9 PM EAST
MONDAY EVENING.

.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 306 PM CST SUN NOV 23 2014

THE STORM SYSTEM WILL EXIT THE AREA MONDAY NIGHT ALLOWING SNOW TO
END FROM WEST TO EAST. AN ADDITIONAL DUSTING TO POSSIBLY ONE HALF
INCH OF ACCUMULATION WILL BE POSSIBLE.

TUESDAY AND TUESDAY EVENING WILL BE QUIET AND DRY AS HIGH PRESSURE
QUICKLY MOVES THROUGH THE MIDWEST. TEMPERATURES WILL AVERAGE BELOW
NORMAL. ATTENTION THEN TURNS TO THE NEXT STORM SYSTEM.

LATE TUESDAY NIGHT INTO WEDNESDAY A CLIPPER TYPE SYSTEM WILL MOVE
THROUGH THE MIDWEST. THE SPREAD ON THE MODEL SOLUTIONS IS QUITE
LARGE BUT OVERALL TRENDS SUGGEST THE SURFACE LOW WILL PASS JUST
NORTH OF THE AREA.

AS SUCH...AN AREA OF SNOW IN THE WARM/MOIST RETURN FLOW WILL MOVE
THROUGH THE AREA LATE TUESDAY NIGHT AND WEDNESDAY. THE BETTER SNOW
CHANCES LOOK TO BE ALONG/NORTH OF I-80 WHERE THE BETTER FORCING IS
LOCATED.

MOISTURE AVAILABILITY AND TEMPERATURES WILL BE IMPORTANT REGARDING
OVERALL SNOW AMOUNTS. IF THE STORM SYSTEM TRACKS FURTHER NORTH AS
SUGGESTED BY ONE MODEL THEN SNOW AMOUNTS WOULD BE LESS.

A VERY PRELIMINARY ESTIMATE IS FOR AREAS SOUTH OF I-80 TO SEE LESS
THAN AN INCH OF ACCUMULATION. FOR I-80 TO HIGHWAY 20 AN INCH OF SNOW
IS POSSIBLE. THE HIGHWAY 20 CORRIDOR MAY SEE 1 TO POSSIBLY 2 INCHES
OF ACCUMULATION.

WEDNESDAY NIGHT ON...
WEDNESDAY NIGHT THROUGH THURSDAY NIGHT THE MODEL CONSENSUS HAS DRY
AND COLD CONDITIONS AS HIGH PRESSURE MOVES THROUGH THE MIDWEST.
TEMPERATURES WILL AVERAGE WELL BELOW NORMAL.

ON FRIDAY...A WEAK DISTURBANCE IS FORECAST TO MOVE THROUGH THE AREA.
MOISTURE AVAILABILITY IS IN QUESTION WITH THE EXITING HIGH PRESSURE
BUT THE MODEL CONSENSUS HAS SLIGHT CHANCE POPS FOR THE AREA.
TEMPERATURES WILL CONTINUE TO AVERAGE BELOW NORMAL.

FRIDAY NIGHT THROUGH SATURDAY NIGHT THE MODEL CONSENSUS AGAIN HAS
DRY AND COLD CONDITIONS AS ANOTHER HIGH PRESSURE MOVES THROUGH THE
MIDWEST. TEMPERATURES WILL STILL AVERAGE BELOW NORMAL.

ON SUNDAY THE MODEL CONSENSUS HAS MAINLY DRY CONDITIONS FOR THE
AREA. THERE IS AN ADDITIONAL UPPER LEVEL DISTURBANCE FORECAST TO
MOVE THROUGH IN THE FLOW ALOFT BUT THE MODEL SOLUTIONS DIVERGE ON
WHERE THE DISTURBANCE WILL GO AND HOW MUCH MOISTURE IS AVAILABLE.
THE MODEL CONSENSUS DOES AGREE THAT TEMPERATURES WILL CONTINUE TO BE
LOWER THAN NORMAL.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 1126 PM CST SUN NOV 23 2014

THE STORM SYSTEM MOVING INTO THE GREAT LAKES WILL PROVIDE WINDY
CONDITIONS TONIGHT INTO MONDAY WITH RAIN CHANGING TO SNOW OVER
EASTERN IA INTO NW IL. STRONG NW WINDS BEHIND A PASSING COLD FRONT
WILL HAVE DRIVEN THE FOG AND DRIZZLE EAST OF ALL THE TERMINALS BY
07Z...BUT WILL BE FOLLOWED BY MVFR TO IFR CONDITIONS DUE TO
LOW CIGS AND THEN LOWERING VISIBILITIES AS THE RAIN CHANGES TO
SNOW. SNOW WILL BE HEAVIEST BETWEEN 12Z TO 18Z WHERE IFR TO LIFR
CONDITIONS ARE IN THE TAFS. SNOW SHOULD DIMINISH TO SNOW SHOWERS
OR FLURRIES IN THE AFTERNOON WITH MVFR CIGS LIKELY LINGERING WELL
INTO THE EVENING HOURS.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...WINTER WEATHER ADVISORY FROM 6 AM TO 9 PM CST MONDAY FOR CLINTON-
     DUBUQUE-JACKSON-SCOTT.

     WINTER WEATHER ADVISORY FROM 3 AM TO 6 PM CST MONDAY FOR CEDAR-
     DELAWARE-JOHNSON-JONES-LINN-LOUISA-MUSCATINE-WASHINGTON.

IL...WINTER WEATHER ADVISORY FROM 6 AM TO 9 PM CST MONDAY FOR BUREAU-
     CARROLL-HENRY IL-JO DAVIESS-MERCER-PUTNAM-ROCK ISLAND-
     STEPHENSON-WHITESIDE.

MO...NONE.
&&

$$

UPDATE...SHEETS
SYNOPSIS...NICHOLS
SHORT TERM...NICHOLS
LONG TERM...08
AVIATION...SHEETS







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