Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 291756
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1256 PM CDT MON SEP 29 2014

.SYNOPSIS...
ISSUED AT 346 AM CDT MON SEP 29 2014

LATEST SFC ANALYSIS WAS INDICATING BROAD RIDGE COMPLEX HOLDING ON
FOR NOW ACRS THE SOUTHEASTERN INTO CENTRAL PLAINS...UP INTO THE
CENTRAL GRT LKS. A SHARP COLD FRONTAL BOUNDARY WAS NUDGING
SOUTHEASTWARD INTO THE NORTHERN FLANK OF THIS FEATURE FROM ACRS
NORTHEASTERN CO...NORTHEASTWARD ACRS THE NEB/SD/IA/MN QUAD-STATE
REGION...AND UP INTO NORTHERN WI/THE NORTHERN GRT LKS. IR SATELLITE
IMAGERY WAS INDICATING EXTENSIVE POST-FRONTAL CLOUD DECK HELPING
DELINEATE THE TIGHTENING LLVL THERMAL RIBBON...AND BAND OF SHOWERS
ON SOUTH EDGE OF UPPER JET STREAK FROM ACRS SD...CENTRAL MN AND OVER
THE LK SUPERIOR BSN. LLVL RETURN FLOW UP THE PLAINS CONVERGING INTO
THIS BOUNDARY HELPING DEVELOPING ONGOING SHOWER CLUSTERS ALONG THE
NE/SD BORDER REGION INTO NW IA. ALOFT...00Z UPPER AIR ANALYSIS AND
MID/HIGH LEVEL MOISTURE TRENDS ON THE CURRENT WATER VAPOR LOOP WERE
INDICATING UPSTREAM OMEGA RIDGE ACRS THE PLAINS TO LEE OF LARGE
CUT-OFF UPPER LOW SPIRALING ACRS THE WEST CENTRAL INTERMOUNTAIN
REGION.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 346 AM CDT MON SEP 29 2014

TODAY...LOOMING STRONG LLVL ANTICYCLONE STARTING TO SPILL DOWN THE
NORTHERN PLAINS AND SOUTH OF THE BORDER OUT OF CANADA TO HAVE IT/S
PUSH ON THE FRONT TODAY...WITH SREF PLACEMENT SHUNTING THE BOUNDARY
INTO THE NORTHERN QUARTER OR EVEN THIRD OF THE CWA BY 00Z THIS
EVENING. BEFORE THIS INCOMING FRONT STARTS TO HAVE IT/S IMPACT...
BULK OF THE DVN CWA TO WARM UP WELL ABOVE NORMAL AGAIN SIMILAR TO
YESTERDAY/S HIGHS IF CLOUD COVER HOLDS OFF LONG ENOUGH...LOW TO MID
80S. LLVL CONVERGENT FIELDS AS WELL AS ISENTROPIC LIFT PROGS UP OVER
THE BOUNDARY SUGGEST SCTRD SHOWERS TO TAIL THEIR WAY INTO THE FAR
NORTHERN CWA BY LATE AFTERNOON SIMILAR WHAT IS CURRENTLY GOING ON
ALONG THE EASTERN SD/ND BORDER REGION. WILL KEEP POPS LOW FOR NOW
WITH THE NEAR TERM MODELS SUGGESTING BETTER LIFT AND SATURATION
PROFILES REMAINING JUST TO THE NORTH OF THE CWA ALONG THE IA/MN
BORDER REGION ACRS INTO SOUTHERN WI. POST FRONTAL CLOUDS AND
DEEPENING LLVL NORTH/NORTHEASTERLY FLOW TO MAKE QUITE A TEMP GRADIENT
FROM THE FAR NORTHERN CWA TO THE SOUTH BY LATE AFTERNOON.

TONIGHT...POTS-FRONTAL REGIME OF INCREASING NORTH TO NORTHEASTERLY
SFC WINDS...CLOUDS AND ISOLATED TO SCTRD SHOWERS TO CONTINUE TO SAG
TOWARD THE I80 CORRIDOR BEFORE LIFT WANES AND UPSTREAM OMEGA RIDGE
SLIDES ACRS THE MID/UPPER MS RVR VALLEY. WILL KEEP LOW POPS IN THESE
AREAS FOR NOW DURING THE EARLY TO MID EVENING PERIOD...BUT THEY MAY
HAVE TO BE RAISED AND EXTENDED LATER INTO THE NIGHT. SLIGHTLY
ELEVATED FRONTOGENETICAL FORCING MAY CONTINUE WRING OUT SPRINKLES
OUT OF THE POST FRONTAL CLOUD DECK ALONG AND NORTH OF I80 INTO THE
OVERNIGHT AND TOWARD TUE MORNING...BUT LIMITED IMPACT OF THIS MAY
NOT BE WORTH MENTIONING AT THIS JUNCTURE OF THE FCST PROCESS.
INCREASING POST-FRONTAL NORTH/NORTHEASTERLY FLOW ON NOSE OF
BACKDOOR STYLE HIGH PRESSURE TO COOL ADVECT AND BRING SOME OF THE
UPPER OR EVEN MID 40S SEEN NOW ACRS CENTRAL AND NORTHERN MN...DOWN
INTO THE NORTHEASTERN THIRD OF THE CWA LATE TONIGHT. THIS WHILE THE
FAR SOUTHWESTERN CWA MAY HAVE TEMPS HAVING TROUBLE DIPPING OUT OF
THE UPPER 50S BY SUNRISE TUE.    ..12..

.LONG TERM...(TUESDAY THROUGH NEXT SUNDAY)
ISSUED AT 346 AM CDT MON SEP 29 2014

A MORE ACTIVE WEATHER PATTERN EVOLVING EARLY THIS WEEK WILL FEATURE
INCREASING RAIN CHANCES AROUND MIDWEEK TO LATE WEEK...ALONG WITH
TEMPERATURES TRENDING BACK CLOSER TO NORMAL AND THEN LIKELY BELOW
NORMAL BY NEXT WEEKEND.

TUESDAY...THE BACKDOOR COLD FRONT DROPPING SOUTH OUT OF THE UPPER
GREAT LAKES IS TRENDING STRONGER AND IS DEPICTED PENETRATING FURTHER
SOUTH INTO THE FORECAST AREA IN THE LATEST MODEL RUNS. LOOKING AT
THE STRENGTH OF THE UPPER WAVE AND THE AMOUNT OF COLD AIR BEHIND THE
COLD FRONT THAT WAS RESULTING IN SNOW REPORTED IN SURFACE
OBSERVATIONS AT 07Z NORTH OF LAKE SUPERIOR EARLY THIS MORNING...THIS
TREND LOOKS REASONABLE. THE 00Z MODELS HAVE THIS FRONT REACHING AS
FAR SOUTH AS CENTRAL IL...NW THROUGH SE IA INTO CENTRAL IA AT 12Z.
THIS WOULD RESULT IN STRATUS OVERSPREADING MUCH OF THE FORECAST
AREA...WHERE IT WILL SLOWLY BURN OFF DURING THE DAY AS THE FRONT
SLOWLY WASHES OUT. THIS CLOUD COVER...AND EASTERLY COMPONENT TO
SURFACE WINDS WILL LIMIT WARMING AND HAVE LOWERED HIGHS TO A RANGE
FROM THE MID 60S NORTH TO MID 70S SOUTH. THIS IS IN THE MIDDLE RANGE
OF 00Z MOS GUIDANCE...WITH THE COLDEST NAM/WRF HIGHS IN A RANGE FROM
THE UPPER 50S NORTH TO NEAR 70 SOUTH...NOT OUT OF THE QUESTION
DEPENDING ON THE DEPTH OF THE COLD AIR AND MOISTURE THAT COULD KEEP
STRATUS IN PLACE THROUGH MUCH OF THE DAY.

TUESDAY NIGHT INTO WEDNESDAY...LOW PRESSURE AT THE SURFACE AND
ALOFT LIFTS NORTHEAST OUT OF THE ROCKIES INTO THE NORTHERN
PLAINS...SPREADING WARM AIR ADVECTION AND GULF MOISTURE INTO THE
FORECAST AREA. THIS WARM ADVECTION PRECIPITATION WILL INITIALLY BE
MORE LIKELY WEST OF THE FORECAST AREA...UNDER THE MORE FAVORABLE MID
LEVEL FORCING...UNTIL AT LEAST MIDDAY WEDNESDAY. WILL MAINTAIN LOW
CHANCES FOR SHOWERS AND ISOLATED THUNDERSTORMS OVER THE FAR WEST FOR
LATE TUE NIGHT INTO WED MORNING. BY AFTERNOON...AN EASTWARD SHIFTING
AND STRENGTHENING SW FLOW ALOFT AND WEAK LOW LEVEL CONVERGENCE WILL
INCREASE PRECIPITATION CHANCES AND HAVE CHANCE TO LIKELY POPS MAINLY
WEST OF THE MS RIVER. HIGH TEMPERATURES MAY REACH THE UPPER 70S SOUTH
ONLY IF THE DEEPER MIXING CAN OCCUR...WHILE TEMPERATURES SHOULD BE
LIMITED TO THE UPPER 60S TO LOWER 70S AT BEST ELSEWHERE...DEPENDING
ON CLOUD COVER AND PRECIPITATION.

WEDNESDAY NIGHT THROUGH THURSDAY NIGHT...FORECAST CONFIDENCE REMAINS
LOW DUE TO SIGNIFICANT MODEL DIFFERENCES...BOTH AT THE SURFACE AND
ALOFT INVOLVING THE PHASING OF UPPER LEVEL WAVES AND HANDLING OF A
POSSIBLE WAVE OF LOW PRESSURE AT THE SURFACE. FOR NOW...LIKELY POPS
ARE MAINTAINED FOR WED NIGHT INTO THU FOR SHOWERS AND AT LEAST
ISOLATED THUNDERSTORMS. THERE IS BETTER CONSENSUS IN SHIFTING THE
PRECIPITATION TO THE EAST THURSDAY NIGHT...WHERE ONLY CHANCES ARE
MAINTAINED. MODEL CONSENSUS HAS HIGHS IN THE LOWER TO MID 70S FOR
THU...WHICH MAY BE TOO OPTIMISTIC CONSIDERING THE SETUP WITH CLOUDS
AND PRECIPITATION. TOTAL QPF FOR THIS PERIOD COULD BE AS HIGH AS
WIDESPREAD ONE HALF TO LOCALLY AN INCH OR MORE...LOOKING AT THE
FORECAST PW VALUES PUSHING 200 PERCENT OF NORMAL...BUT THIS WILL BE
LARGELY DEPENDENT ON WHERE THE SURFACE LOW TRACKS.

FRIDAY THROUGH NEXT WEEKEND...A DEEP NW FLOW FOLLOWING THE UPPER
TROUGH PASSAGE WILL RESULT BELOW NORMAL TEMPERATURES AND LITTLE
POTENTIAL FOR PRECIPITATION. WHILE THE LATEST FORECAST DOES LOWER
TEMPERATURES A FEW DEGREES...TO DAYTIME HIGHS IN THE UPPER 50S TO
UPPER 60S AND LOWS IN THE UPPER 30S TO LOWER 40S FRIDAY AND
SATURDAY...FURTHER DOWNWARD ADJUSTMENTS WILL LIKELY OCCUR IN LATER
FORECASTS AS MODELS CATCH UP ON THE STRENGTH OF THE COLD AIR SHOWN
RUSHING INTO THE NORTHERN PLAINS AT 850 MB. TEMPERATURES SHOULD
MODERATE SUNDAY AS A WEAK LOW PRESSURE SYSTEM SHOWN PASSING TO THE
NORTH WOULD RESULT IN WARM ADVECTION ALONG WITH POTENTIAL SHOWERS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1246 PM CDT MON SEP 29 2014

COLD FRONT MOVING THROUGH FAR NORTHEAST IA EARLY THIS AFTN WILL CONTINUE
TO SHIFT SOUTH AND PASS THROUGH THE TERMINALS TNGT. THE FRONT WILL BE
ACCOMPANIED BY WIND SHIFT TO NORTH/NORTHEAST AT AROUND 10 KTS... WITH
BRIEF PERIOD OF SOME LOCAL GUSTS 15-20 KTS POSSIBLE WITH THE PASSAGE.
THERE IS A LOW CHANCE FOR STRAY SHOWER OR LIGHT RAIN BRIEFLY THIS
EVENING MAINLY AT KDBQ AS AREA BRUSHED BY PASSING UPPER LEVEL DISTURBANCE.
LIKELY TO SEE STRATUS WITH LOW MVFR TO IFR CIGS DEVELOP WITHIN A FEW HOURS
AFTER FRONTAL PASSAGE AND LINGER THROUGH TUE AM.

&&

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

$$

SYNOPSIS...12
SHORT TERM...12
LONG TERM...SHEETS
AVIATION...05





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