Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 242035
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
335 PM CDT FRI OCT 24 2014

.SYNOPSIS...
ISSUED AT 259 PM CDT FRI OCT 24 2014

WIDESPREAD FOG AND STRATUS FROM THIS MORNING HAS SINCE NARROWED DOWN
TO A ROUGHLY 100 MILE WIDE AXIS FROM SE MN THROUGH CENTRAL AND
EASTERN IA TO FAR NORTHERN MO. 18Z SURFACE ANALYSIS SHOWED THIS WAS
A FAVORABLE AREA OF LOW LEVEL MOISTURE ADVECTION AHEAD OF A SURFACE
TROUGH THAT REACHED FROM S CENTRAL MN THROUGH WESTERN IA TO N
CENTRAL KS. SURFACE DEWPOINTS OVER CENTRAL IA WERE IN THE UPPER 50S
TO LOWER 60S EARLY THIS AFTERNOON...WHILE LOWER TO MID 50S WERE MORE
COMMON TO THE EAST OVER THE LOCAL FORECAST IN THE DEEPER MIXING AND
SUNSHINE. THE BOUNDARY OVER WESTERN IA WILL ADVANCE SLOWLY EAST
TONIGHT...WITH ITS ASSOCIATED TONGUE OF MOISTURE AND CONVERGENCE
LIKELY LEADING TO A RESURGENCE OF LOW CLOUDS AND FOG.

&&

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 259 PM CDT FRI OCT 24 2014

MAIN FOCUS IS ON THE POTENTIAL FOR FOG TONIGHT. LIGHT SOUTHERLY
WINDS AHEAD OF THE ADVANCING SURFACE TROUGH OVER WESTERN IA WILL
CONTINUE TO ADVECT LOW LEVEL MOISTURE...HOLDING DEWPOINTS IN THE MID
TO UPPER 50S THIS EVENING. FOG WILL LIKELY DEVELOP AS WINDS DECOUPLE
FROM THE WEAK GRADIENT FLOW UNDER INITIALLY MOSTLY CLEAR
SKIES...LEADING TO RADIATIONAL COOLING. THIS FOG WILL MOST LIKELY
DEVELOP FIRST IN THE WEST AND NW...CLOSEST TO THE EXISTING STRATUS
FIELD AND THEN EXPAND SOUTHEASTWARD INTO NW IL BY LATE EVENING. A
THERMAL RIDGE AT 850 MB...MIGRATING THROUGH THE AREA BY 06Z WILL
REINFORCE THE LOW LEVEL INVERSION AND ASSIST THE FOG PROCESS. A
DEVELOPING DEEP DRY LAYER ABOVE THE INVERSION MAY LEAD TO
DRIZZLE...WHICH HAS BEEN INCLUDED ACROSS THE NORTH...TIMED WITH PEAK
CONVERGENCE WITH THE SURFACE FRONTAL PASSAGE. THE BIG QUESTION FOR
TONIGHT IS HOW THICK THE FOG WILL GET AND THEN HOW LONG BEFORE THE
DEVELOPING POST FRONTAL LOW LEVEL COOL AND DRY AIR ADVECTION LEADS
TO DISSIPATION SATURDAY MORNING. WITH LOW CONFIDENCE ON THE COVERAGE
OF DENSE FOG...WILL HOLD OFF ON AN ADVISORY FOR NOW...BUT INCLUDE
WIDESPREAD FOG FROM LATE EVENING THROUGH EARLY MORNING. LOW
TEMPERATURES WERE KEPT CLOSE TO THE PREVIOUS FORECAST...FROM THE
UPPER 40S NW TO THE LOWER 50S SOUTHEAST.

SATURDAY...A DEVELOPING NW FLOW RESULTING FROM AN UPPER RIDGE BUILDING
OUT WEST...AND ADVANCING SURFACE RIDGE WILL LEAD TO MOSTLY SUNNY
SKIES AND LIGHT WINDS. A LARGE THERMAL RIDGE OVER THE PLAINS...WITH
850 MB TEMPERATURES INTO THE TEENS AS FAR NORTH AS THE DAKOTAS...
WILL LEAD WARM TEMPERATURES FOR LATE OCTOBER. UNDER THIS THERMAL
RIDGE...SURFACE TEMPERATURES WERE IN THE 70S AND 80S THIS AFTERNOON
ACROSS NEB AND SD...WITH THE HELP OF DEEP MIXING AND DOWNSLOPE
COMPRESSIONAL WARMING. HOWEVER...EVEN WITH RELATIVELY SHALLOW MIXING
SHOWN IN MODEL SOUNDINGS...TEMPERATURES IN THE LOCAL AREA SATURDAY
SHOULD REACH AT LEAST THE MID 60S TO LOWER 70S.

.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 259 PM CDT FRI OCT 24 2014

MILD AND MAINLY DRY INTO MONDAY BEFORE NEXT FRONT BRINGS PERIOD OF
WET WEATHER FOLLOWED BY COOLER TEMPS /NEAR NORMAL/.

SATURDAY NIGHT...HIGH PRESSURE TO SETTLE OVER REGION WITH DRY AND
COOL CONDITIONS. IDEAL RADIATIONAL COOLING SETUP WITH LIGHT
WIND...DRIER AIR AND MAINLY CLEAR SKIES SUPPORTIVE OF STAYING NEAR
TO JUST BELOW COOLER SIDE OF GUIDANCE FOR MINS.

SUNDAY AND SUNDAY NIGHT...HIGH PRESSURE OVERHEAD SUNDAY AM WILL
SHIFT EAST DURING THE AFTERNOON AHEAD OF DEVELOPING SYSTEM IN THE
PLAINS. STRENGTHENING PRESSURE GRADIENT BETWEEN DEPARTING HIGH AND
PLAINS LOW TO RESULT IN INCREASING SOUTHEAST WINDS 10-20+ MPH.
KEPT HIGHS CLOSE TO PREVIOUS FCST RANGING FROM MID 60S NORTH TO
NEAR 75 FAR SOUTH... BUT THESE TEMPS COULD BE FEW TO SEVERAL DEGS
TOO MILD GIVEN NON-FAVORABLE WARMING SOUTHEAST WIND COMPONENT AND
POTENTIAL FOR BAND OF WARM ADVECTION CLOUDS. EVEN IF LOWER WOULD
STILL BE MAINLY 60S TO AROUND 70 FOR HIGHS WHICH IS STILL ABOVE NORMAL.
CONTINUED WITH SMALL SHOWER CHANCES SUNDAY NIGHT NORTH OF I 80 WITH
SURGE OF THETA-E ADVECTION ON NOSE OF 40-50 KT LOW LEVEL JET AHEAD OF
NORTHWARD ADVANCING SURFACE WARM FRONT. LOWS SUNDAY NIGHT MAY ACTUALLY
OCCUR IN THE EVENING WITH STEADY TO RISING TEMPS OVERNIGHT WITH THE
PASSAGE OF WARM FRONT AND SOUTHERLY WINDS 10-20 MPH.

MONDAY THROUGH TUESDAY...WHILE STILL SOME VARIANCES ON STRENGTH OF
NEXT UPPER LEVEL TROUGH MAKING INROADS FROM THE PLAINS... THE SIGNAL
OVERALL INCREASING FOR PERIOD OF WET WEATHER BY MONDAY NIGHT INTO
TUESDAY WITH COLD FRONTAL PASSAGE. HAVE RAISED POPS INTO LIKELY CAT
EASTERN HALF OF CWA BUT FAVORABLE JET STRUCTURE WITH POTENTIAL SURFACE
WAVE IN ENTRANCE REGION... UPPER DIFFLUENCE AND AMPLE MOISTURE SUGGEST
LIKELY TO CATEGORICAL POPS NEEDED MOST IF NOT ALL OF CWA WITH MAINLY
MODERATE QPF AMOUNTS 0.20 TO 0.60 INCH. MONDAY LOOKS TO BE LAST OF THE
ABOVE NORMAL WARMTH...WITH PRE-FRONTAL WARM SECTOR FEATURING DEEP MIXING
ON GUSTY SOUTH/SOUTHWEST WINDS FUELING WIDESPREAD HIGHS IN THE 70S.
RAIN ANTICIPATED TO SHIFT EAST AS DAY PROGRESSES ON TUESDAY WITH FRONTAL
PASSAGE FOLLOWED BY COOLER AND DRIER CONDITIONS ON GUSTY NORTHWEST WINDS.

WEDNESDAY THROUGH FRIDAY...COOLER BUT ONLY BACK TO AROUND NORMAL WITH
QUASI-ZONAL UPPER FLOW. QUICK MOVING SYSTEM SUGGESTED LATER WEDNESDAY
AND THURSDAY BUT WITH MOISTURE LIMITED POPS WERE KEPT IN SLIGHT CHANCE
CATEGORY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1235 PM CDT FRI OCT 24 2014

WIDESPREAD FOG AND LOW CLOUDS OVER THE AREA THIS MORNING WILL
CONTINUE TO LIFT WITH MOST SITES IMPROVING TO VFR FOR A PERIOD
THIS AFTERNOON. HOWEVER...LINGERING MOISTURE AND A SLOW MOVING
WEAK COLD FRONT WILL LIKELY LEAD TO A RETURN OF LOW CLOUDS AND FOG
AFTER SUNSET. THE LATEST FORECASTS HAVE A RETURN TO IFR CONDITIONS
THIS EVENING AT ALL SITES...WITH LIFR AND POSSIBLY VLIFR LIKELY AT
ESPECIALLY DBQ AND MLI...WHILE THERE IS A LOWER CONFIDENCE LEVEL
THAT THE LOWER CONDITIONS WILL AFFECT CID AND BRL. AN IMPROVEMENT
TO AT LEAST MVFR IS LIKELY AT ALL SITES BY MID MORNING...FOLLOWED
BY VFR CONDITIONS SATURDAY AFTERNOON.


&&

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

$$

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





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