Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 200549
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1149 PM CST WED NOV 19 2014

.SYNOPSIS...
ISSUED AT 334 PM CST WED NOV 19 2014

A MID-LEVEL TROUGH WILL REMAIN ENTRENCHED OVER THE MIDWEST AND GREAT
LAKES AREA THROUGH THURSDAY. SIGNIFICANT HEIGHT RISES WILL COMMENCE
THURSDAY NIGHT AT THE SAME TIME THAT A SURFACE HIGH PRESSURE SYSTEM
MOVES ACROSS THE FORECAST AREA. THE COLDEST AIR SO FAR THIS FALL MAY
OCCUR THURSDAY NIGHT WITH LOW TEMPERATURES NEAR ZERO IN
CENTRAL/NORTHERN VALLEY LOCATIONS...WHICH IS 25-30 DEGREES BELOW
AVERAGE FOR MID NOVEMBER.

&&

.SHORT TERM...(THIS EVENING THROUGH THURSDAY NIGHT)
ISSUED AT 334 PM CST WED NOV 19 2014

TONIGHT...FORECAST SOUNDINGS SHOW A SATURATED LAYER...TRAPPED
BETWEEN 900-850 MB BY AN INVERSION...SLOWLY DRYING THROUGH THE
EVENING AND OVERNIGHT PERIOD. THEREFORE...LIGHT SNOW SHOWER OR
FLURRY CHANCES WILL DIMINISH. ALSO...AS THE SFC PRESSURE GRADIENT
WEAKENS...NW WINDS WILL BACK TO THE WEST AND DECREASE TO BETWEEN 10
TO 20 MPH. LOWS WILL BE IN THE TEENS FOR MOST AREAS.

THURSDAY...DAYTIME MIXING INTO A COLD POOL ALOFT AND STEADY NW WINDS
WILL RESULT IN COLD AND BREEZY CONDITIONS. HIGHS WILL RANGE FROM THE
UPPER TEENS ACROSS THE NORTH TO NEAR 30 IN THE FAR SOUTH. NORMAL
HIGHS THIS TIME OF YEAR SHOULD BE IN THE LOWER TO UPPER 40S. 850 MB
TEMPS AT -12 C ACROSS THE CENTRAL CWA ARE 2 STANDARD DEVIATIONS
BELOW NORMAL ON THE NAEFS...BUT THESE VALUES BEGIN TO WARM
SUBSTANTIAL THURSDAY NIGHT WHICH WILL MANIFEST AS WARMER SFC TEMPS
ON FRIDAY.

THURSDAY NIGHT...BITTERLY COLD. LOWS WILL BE IN THE SINGLE DIGITS TO
NEAR ZERO IN FAVORED COLD VALLEY LOCATIONS. DEPENDING ON HOW QUICKLY
MID/HIGH LEVEL CLOUDS INCREASE LATE THURSDAY NIGHT...SOME LOCATIONS
MAY DIP A FEW DEGREES BELOW ZERO. LUCKILY...SURFACE WINDS WILL BE
LIGHT SO THE WIND CHILL WILL BE NEGLIGIBLE.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 334 PM CST WED NOV 19 2014

THE STRONG STORM SYSTEM STILL PROGGED TO DEVELOP AND AFFECT THE AREA
OVER THE WEEKEND IS THE MAIN CHALLENGE. THE CURRENT EXPECTED STORM
TRACK WILL RESULT IN PRIMARILY A MODERATE TO POSSIBLY SEASONABLY
HEAVY RAIN PRODUCING SYSTEM OVER THE FORECAST AREA WITH A POSSIBLE
MIX OF FREEZING PRECIPITATION AT THE ONSET FRIDAY NIGHT. THE 12Z
CANADIAN...GFS AND ECMWF HAVE TRENDED TOWARD A SIMILAR SOLUTION OVER
THE PAST 2 TO 3 RUNS...SHOWING A DEEPENING SURFACE LOW LIFTING NORTH
THROUGH IL SUNDAY NIGHT...WHICH CONTINUES TO STRENGTHEN AND THEN
OCCLUDES OVER UPPER MI OR THE LAKE SUPERIOR REGION EARLY NEXT
WEEK...WITH THE ENSUING WRAP-AROUND MOISTURE RETURNING WINTER
WEATHER TO THE LOCAL AREA. HOWEVER...THERE REMAIN ENOUGH DIFFERENCES
IN THE TIMING AND DETAILS OF HOW...AND TO WHAT EXTENT...NORTHERN AND
SOUTHERN STREAM SHORTWAVES PHASE TO FORM THE STRONG UPPER LOW AND
OCCLUDING SYSTEM OVER THE UPPER MS VALLEY AND GREAT LAKE BY EARLY
NEXT WEEK TO KEEP A FAIR AMOUNT OF UNCERTAINTY IN CRITICAL DETAILS
OF THE FORECAST...ESPECIALLY EARLY NEXT WEEK.

FRIDAY...A DEVELOPING DEEP SOUTHERLY FLOW WILL REPLACE THE CURRENT
ARCTIC AIRMASS. STRONG WARM/MOIST ADVECTION ALOFT WILL LEAD TO
CLOUDY SKIES BY AFTERNOON...WITH SURFACE TEMPERATURES RISING THROUGH
THE EVENING HOURS. HIGHS FOR THE DAY WILL LIKELY BE IN THE
EVENING...FROM THE MID 20S NORTH TO THE MID 30S SOUTH WITH STEADY OR
RISING TEMPERATURES THROUGH THE NIGHT. ISENTROPIC LIFT WILL LEAD TO
LIGHT PRECIPITATION...IN THE FORM OF DRIZZLE OR LIGHT RAIN...BEGINNING
IN THE SOUTH IN THE EVENING AND SPREADING NORTH OVERNIGHT. WHERE AIR
TEMPERATURES WILL BE INITIALLY BELOW FREEZING...THIS MAY LEAD TO A
PERIOD OF LIGHT FREEZING PRECIPITATION OR POSSIBLE GLAZE OF ICE AS
THE GROUND IS LIKELY FROZEN SEVERAL INCHES OVER MOST OF THE AREA.
WILL KEEP CHANCE POPS AND A FEW HUNDREDTHS OF AN INCH OF QPF TO
COVER THIS...BUT CONFIDENCE IN WHETHER THERE THIS PERIOD OF WARM
ADVECTION WILL RESULT IN PRECIPITATION...AND IN WHAT FORM...IS LOW
AT THIS TIME.

SATURDAY...THE WARM ADVECTION SOUTHERLY FLOW STRENGTHENS AND SHOULD
DRIVE THE ENTIRE AREA WELL ABOVE FREEZING. CONTINUED THETAE
ADVECTION WILL KEEP A POTENTIAL FOR DRIZZLE OR LIGHT RAIN
GOING...ESPECIALLY ACROSS THE SOUTH AND SOUTHEAST. THERE...WHERE THE
SNOW COVER IS LACKING OR NEGLIGIBLE...TEMPERATURE WILL POTENTIALLY
PUSH INTO THE LOWER 50S BY LATE DAY.

SATURDAY NIGHT THROUGH SUNDAY...THE SOUTHERN STREAM SHORTWAVE MOVING
ACROSS TX IS PROGGED TO DEVELOP A SURFACE LOW...WHICH LIFTS
NORTHEAST AND RAPIDLY DEEPENS SATURDAY NIGHT INTO SUNDAY. THIS THEN
MERGES INTO A NEARLY STACKED SYSTEM OVER THE UPPER MS VALLEY/WESTERN
GREAT LAKE BY SUNDAY NIGHT. THIS WOULD TRACK A DEFORMATION ZONE AND
WARM CONVEYOR BELT THROUGH THE FORECAST AREA WITH A POTENTIAL FOR
WIDESPREAD 1 TO 1.5 INCHES OR GREATER RAINFALL AMOUNTS OVER MUCH OF
THE FORECAST AREA. THIS COULD LEAD TO AT LEAST MINOR HYDRO
ISSUES DUE TO THE FROZEN GROUND. THIS WILL ALSO BE A FAVORABLE SETUP
FOR WIDESPREAD FOG...WHICH WOULD BE POSSIBLE SATURDAY THROUGH SUNDAY
NIGHT. WILL INITIALLY MENTION FOG IN THE SATURDAY NIGHT PERIOD FOR
NOW...WHERE THE SETUP WITH BACKING WINDS...DEEP MOISTURE
POOLING...AND LIGHTER PRECIPITATION...LOOKS MOST FAVORABLE...AND IS
ALSO BACKED BY THE GFS ENSEMBLE FOG PROBABILITY GUIDANCE.
TEMPERATURES WILL LIKELY BE WELL INTO THE 40S OVER MOST OF THE AREA
UNTIL THE TRAILING COLD FRONT PUSHES THROUGH SUNDAY NIGHT.

SUNDAY NIGHT ONWARD...THE OCCLUDED FRONT WILL LIKELY SWEEP THROUGH
SUNDAY NIGHT...CHANGING RAIN TO SNOW FROM WEST TO EAST. LIGHT SNOW
AND STRONG W-NW WINDS WILL FOLLOW MONDAY AND POSSIBLY WELL INTO
TUESDAY. MEASURABLE SNOW WILL BE POSSIBLE THROUGH THIS
PERIOD...ESPECIALLY OVER THE NORTH AND NORTHEAST. TEMPERATURES WILL
FALL BACK AT LEAST INTO THE 20S AND 30S...WITH THE REAL COLD PUNCH
HOLDING OFF UNTIL THE FILLING SYSTEM AND DEVELOPING STRONGER NW FLOW
ALLOWS A STRONGER COLD FRONTAL PASSAGE SOMETIME TUESDAY. THIS WILL
RETURN TEMPERATURES BACK TO WELL BELOW NORMAL THROUGH AT LEAST MID
WEEK. ANOTHER SIGNIFICANT SYSTEM IS SUGGESTED FOR LATE WEEK INTO THE
NEXT WEEKEND...BUT THERE IS VERY POOR AGREEMENT OR CONSISTENCY IN
THE MODELS TO LEND MUCH CONFIDENCE.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 1138 PM CST WED NOV 19 2014

VFR CONDITIONS EXPECTED THROUGH THE TAF CYCLE WITH SCTD TO AREAS
OF BKN CLOUDS WITH BASES 2500-4000FT AGL. WEST TO NORTHWEST WINDS
WILL PREVAIL AROUND 10 KTS AND BECOME GUSTY AT TIMES TO 15-20 KTS
FROM MID MORNING THROUGH MID AFTERNOON. HIGH PRESSURE WILL BUILD
IN THURSDAY NIGHT BRINGING CLEAR SKIES AND LIGHT WINDS.

&&

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

$$

SYNOPSIS...UTTECH
SHORT TERM...UTTECH
LONG TERM...SHEETS
AVIATION...MCCLURE




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