Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 300902
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
402 AM CDT TUE SEP 30 2014

.SYNOPSIS...
ISSUED AT 400 AM CDT TUE SEP 30 2014

A BACKDOOR COLD FRONT CONTINUED TO SURGE S-SW THROUGH THE REGION
EARLY THIS MORNING...MARKED BY AN EXPANSIVE DECK OF POST FRONTAL
STRATUS. AT 3 AM...THE FRONT WAS ROUGHLY FROM SPRINGFIELD IL W-NW
ALONG THE IA/MO BORDER...WITH STRATUS LAGGING WELL BEHIND FROM ABOUT
PEORIA NW THROUGH WASHINGTON TO NEWTON IN IA. SATELLITE IR CHANNEL
SHOWED THIS STRATUS DECK WITH PATCHY THIN SPOTS COVERING MOST OF THE
GREAT LAKES AND REACHING WEST ACROSS WI INTO EASTERN MN. TO OUR
WEST...HIGH CLOUDS WERE ENCROACHING INTO SW IA AHEAD OF A STRONG AND
NEARLY VERTICALLY STACKED UPPER LOW OVER THE NEB PANHANDLE. 00Z
ANALYSIS AND RECENT WV IMAGERY SHOWED THIS PLAINS LOW TRENDING MORE
NORTHWARD AS IT PUSHED INTO A SHARP UPPER LEVEL RIDGE AXIS THAT
REACHED FROM TX TO MN. EAST OF THIS RIDGE...A STRONG SHORTWAVE WAS
MOVING SE THROUGH THE GREAT LAKES...DRIVING THE BACKDOOR COLD FRONT
THROUGH THE LOCAL AREA.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 400 AM CDT TUE SEP 30 2014

INITIAL CONCERN IS THE TODAY/S TEMPERATURE FORECAST...WHICH WILL BE
CLOSELY TIED TO CLOUD TRENDS AND PRESENT A LARGE BUST POTENTIAL.
OVERNIGHT...THE FOCUS TURNS TO THE ADVANCING PLAINS SYSTEM...WHICH
WILL SPREAD CONVECTIVE PRECIPITATION EASTWARD...POSSIBLY REACHING
INTO EASTERN IA TOWARD MORNING.

TODAY...HOW FAST AND TO WHAT EXTENT THE STRATUS DECK BREAKS DOWN
WILL BE KEY TO HIGH TEMPERATURES. THE STRATUS WAS ASSOCIATED WITH A
SOMEWHAT THIN LAYER OF MOISTURE SITUATED BELOW THE INVERSION AROUND
800 TO 850 MB...LOOKING AT UPSTREAM 00Z SOUNDINGS. THE LOW LEVEL
INVERSION WILL BE REINFORCED BY THE NORTHEASTERLY WINDS OUT OF THE
GREAT LAKES...WHICH ARE EXPECTED TO SLOWLY VEER TO EAST AND THEN
MORE SOUTHEASTERLY TODAY AS THE UPPER RIDGE BREAKS DOWN/ADVANCES
EAST...AND THE LOW LIFTS NORTHEAST THROUGH THE NORTHERN PLAINS.
OVERALL IMPRESSION IS THAT MODELS WILL BE TOO OPTIMISTIC CLEARING
OUT THIS STRATUS...ESPECIALLY IN THE CENTRAL AND NORTH. THE
AFOREMENTIONED HIGH CLOUDS ADVANCING NORTHEAST OVER THE AREA TODAY
FILTERING THE ALREADY LIMITED FALL SUNSHINE...ALONG WITH THE
WEAK WARM ADVECTION ABOVE THE INVERSION LAYER WILL NOT HELP IN THIS
CLEARING. THUS...HAVE GONE ON THE PESSIMISTIC SIDE EXPECTING THE LOW
CLOUDS TO ONLY SLOWLY BREAKUP...AND NOT OCCUR IN WIDESPREAD FASHION
UNTIL AFTERNOON. THIS WOULD HOLD HIGHS TO THE LOWER TO MID 60S NORTH
OF I-80...WHILE A GREATER LIKELIHOOD OF EARLIER CLEARING IN THE FAR
SOUTH WILL JUSTIFY LOWER TO POSSIBLY MID 70S. THIS WILL COME AS A
SHARP CHANGE AFTER OUR PAST WEEK/S STRETCH OF WIDESPREAD MID 70S TO
MID 80S. IF CLOUDS WERE TO BREAKUP MUCH SOONER...HIGHS COULD BE 3 TO
5 DEGREES WARMER THAN ADVERTISED.

TONIGHT...GULF MOISTURE AND WARM ADVECTION ALOFT REACHES INTO
CENTRAL AND ESPECIALLY WESTERN IA AS THE UPPER RIDGE BREAKS DOWN AND
THE LOW LIFTS INTO ND. CONDITIONS WILL BE MOST FAVORABLE FOR
ELEVATED CONVECTION WELL WEST OF THE AREA THROUGH THE NIGHT AND MOST
MODELS DEPICT THE PRECIPITATION REMAINING WEST...OR POSSIBLY
ADVANCING INTO FAR WESTERN OR NW PORTIONS OF THE FORECAST AREA
TOWARD MORNING. WILL THUS KEEP SLIGHT TO LOW END CHANCE POPS TOWARD
MORNING IN THE W AND NW. OTHERWISE...SKIES WILL BE MOSTLY CLOUDY
WITH A LOW LEVEL SOUTHEAST FLOW KEEPING A COOL...DRY MODIFIED
CANADIAN/GREAT LAKES AIRMASS OVER MUCH OF THE AREA THROUGH THE
NIGHT. HAVE THUS KEPT LOWS ON THE COOL SIDE...FROM THE MID 40S
NORTHEAST TO THE MID AND UPPER 50S SOUTH AND SOUTHWEST.


.LONG TERM...(WEDNESDAY THROUGH NEXT MONDAY)
ISSUED AT 400 AM CDT TUE SEP 30 2014

WEDNESDAY AND THURSDAY...00Z RUN SUITE OF MODELS IN GENERALLY
CONTINUE TO SUGGEST SFC FRONT TO GET ALIGNED PARALLEL UNDER MEAN FLOW
SOUTHWESTERLIES ACRS WESTERN IA INTO CENTRAL MN ON WED AS UPSTREAM
L/W TROF CONTINUES TO PHASE/DIG ACRS THE WESTERN PLAINS. INCREASING
SOUTH TO SOUTHWESTERLY LLJ AHEAD OF THIS PROCESS TO ACT AS WARM
MOIST CONVEYOR THAT WILL INCREASE THROUGH THU. EXPECT ELEVATED
SHOWERS AND SOME THUNDERSTORMS TO INCREASE INTO THE WESTERN CWA AS
WED PROGRESSES...WHILE AREAS EAST OF THE MS RVR IN SOUTHEASTERLY
BOUNDARY LAYER FETCH MAY STAY DRY UNTIL WED EVENING. THE DVN CWA TO
BE INCREASINGLY UNDER THE INFLUENCE OF THE WARM SECTOR WED AND THE
LONGER DURATION OF RAIN/CLOUD FREE AREAS IN THE SOUTHEASTERN HALF OF
THE FCST AREA MAY WARM UP INTO THE MID TO UPPER 70S WITH EVEN AN 80
DEGREE READING POSSIBLE. A QUICKER ARRIVAL OF RAIN AND COLUMN
SATURATION WILL MAKE THE FCST/ADVERTISED TEMPS TOO WARM
CWA-WIDE...BUT FEEL IN SUCH A SYNOPTIC SCALE SET-UP A SLOWER TREND
IN SHOWER ONSET WILL UNFOLD. LLVL CYCLOGENESIS WILL LIKELY BLOSSOM
TO LEE OF THE UPPER L/W TROF BASE ACRS THE SOUTHERN PLAINS WED
NIGHT...AND DEEPENING LIFT ON LEFT EXIT NOSE OF UPPER JET STREAK TO
INCREASE ACRS THE REGION AS THE NIGHT PROGRESSES. WITH ONGOING
THTA-E FEED BY LLVL JET PROCESS...THE SET-UP FOR ROUNDS OF ELEVATED
SHOWERS AND STORMS ACRS MOST OF THE CWA WED NIGHT INTO THU MORNING
APPEARS TO BE THERE TO WARRANT HIGH POPS. BEFORE SATURATION
DEEPENS...A FEW INITIAL ELEVATED THUNDERSTORMS MAY PRODUCE SOME HAIL
WED NIGHT INTO THU AM. AS FOR RAINFALL AMOUNTS...EXTENT OF CURRENTLY
PROGGED LIFT AND INCOMING MOISTURE FEED SUGGEST MUCH OF THE CWA TO
GET FROM 0.20 OF AN INCH ON THE LOW END...WITH A FEW HIGHER SWATHS
OF AREAS GETTING UP TO 0.75 OF AN INCH BY 12Z THU. LIKE THE RUN TO
RUN TRENDS OF PULLING OUT DEEPENING SFC CYCLONE FURTHER TO THE
NORTHWEST WITH STRENGTH OF APPROACHING L/W TROF...GENERALLY FROM
ACRS CENTRAL IA INTO NW WI ON THU. DEPENDING ON WHERE THE LOW/S
ASSOCIATED TRIPLE POINT RIPPLES UP OR LAYS OUT...SOME POTENTIALLY
STRONG OR EVEN SVR STORMS MAY BE POSSIBLE ACRS THE SOUTHERN OR
SOUTHEASTERN CWA BY THU AFTERNOON AND EARLY EVENING. FCST SOUNDINGS
SUGGESTING COLUMN SATURATION FURTHER TO THE NORTH OF 1.5 TO 1.7
INCHES IS SEASONABLY HIGH AND COULD FUEL LOCALLY HEAVY RAINFALL OF
OVER AN INCH BY THU EVENING IN SOME LOCATIONS. CURRENT MODEL TIMING
OF POST-FRONTAL SWEEP SUGGESTS BULK OF PRECIP EXITING THE DVN CWA BY
04Z TO 06Z FRI...WITH TIGHTENING LLVL CYCLONIC FLOW MAKING FOR BRISK
WEST TO NORTHWEST SFC WINDS AND LLVL COLD AIR ADVECTION MACHINE
RAMPING UP INTO FRI MORNING. IMPRESSIVE DEEPENING CYCLONE ACRS THE
CENTRAL LK SUPERIOR BSN LATE THU NIGHT...WITH THE UPPER TROF REALLY
BECOMING COLD CORE WITH NORTHERN CANADA FETCH.

FRIDAY AND SATURDAY...BOTH THE 00Z RUN GFS AND ECMWF IN GENERAL
AGREEMENT OF SUGGESTING 0C OR EVEN SUB-ZERO C H85 MB TEMPS TO
ADVECT DOWN ACRS THE CWA BY FRI EVENING. ONGOING TIGHT CYCLONIC FLOW
AND STOUT COLD AIR ADVECTION TO MAKE FOR A WINDY RAW DAY FRI...
NORTHWEST WINDS OF 20-30 MPH WITH HIGHER GUSTS AND TEMPS HELD IN
THE 50S. WRAP AROUND RAIN SHOWERS TO THE NORTHEAST ACRS WI MAY MIX
WITH SNOW BY FRI EVENING IF CURRENT FCST VERTICAL PROFILES ARE
CORRECT AND THE MODELS ARE NOT OVERDOING THE COLD SIGNAL. WEST TO
NORTHWEST SFC WINDS WILL KEEP UP FRI NIGHT INTO SAT MORNING IN
ONGOING CYCLONIC GRADIENT...BUT COLD ADVECTION ITSELF MAY STILL
PLUMMET TEMPS WELL DOWN IN THE 30S BY SAT MORNING. DEPENDING ON
CLOUD COVER AND MIXING...TEMP RECOVERY ON SAT MAY ONLY MAKE THE LOW
TO MID 50S...MORE CLOUDS AND THEN SOME AREAS HELD IN THE 40S IF H85
MB TEMPS IN THE -1 TO -3C DEGREE RANGE PAN OUT. SOME SIGNALS OF A
CLIPPER TYPE SYSTEM RIPPLING DOWN IN HIGH AMPLITUDE PATTERN/STEEP
NORTHWESTERLIES ON WESTERN FLANK OF DEEP L/W TROF AXIS...THAT MAY
ACTUALLY INDUCE SOUTHERLY RETURN FLOW AHEAD OF IT MAKING FOR A
MILDER NIGHT SAT NIGHT THAN FRI NIGHT. BUT IF THIS LOW DOES NOT
MATERIALIZE...SECOND NIGHT AFTER COLD FRONT RULE MAY SET THE STAGE
FOR THE FIRST WIDESPREAD FROST ADVISORY OR EVEN FREEZE POTENTIAL OF
THE FALL SEASON SAT NIGHT.

SUNDAY THROUGH NEXT MONDAY...IF THE CLIPPER SYSTEM VERIFIES...ALONG
WITH MODERATING TEMPS IT BRINGS AHEAD OF IT..THERE MAY BE A CHANCE
FOR SOME SCTRD SHOWERS SUNDAY AND SUNDAY NIGHT.    ..12..

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1125 PM CDT MON SEP 29 2014

WIDESPREAD POST COLD FRONTAL STRATUS BETWEEN 700 AND 1500 FT WILL
CONTINUE TO SPREAD SOUTHWEST OVER ALL OF EASTERN IOWA AND
NORTHWEST ILLINOIS THROUGH THE NIGHT. MVFR TO OCCASIONAL IFR CIGS
WILL PERSIST THROUGH MUCH OF TUESDAY MORNING...WITH GRADUAL
LIFTING TO MVFR CIGS AROUND 2500 FT BY LATE MORNING TUESDAY.
MODELS ARE NOT HANDLING THE WIDESPREAD NATURE OF THIS VERY
WELL...AND WE MAY WELL BE CLOUDY THROUGH LATE AFTERNOON BASED ON
CURRENT OBSERVED DATA. WHILE CLOUDY WITH NORTHEAST WINDS...THERE
SHOULD BE LITTLE IF ANY SHOWER ACTIVITY WITH THIS GLOOMY DAY.
ERVIN

&&

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

$$

SYNOPSIS...SHEETS
SHORT TERM...SHEETS
LONG TERM...12
AVIATION...ERVIN






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