Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 211813
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1213 PM CST FRI NOV 21 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 402 AM CST FRI NOV 21 2014

TODAY...RETURN FLOW AND MOISTURE INCREASE CURRENTLY GATHERING ACRS
THE SOUTHERN PLAINS AND LOWER MS RVR VALLEY. 30 TO 40 KT SOUTH-
SOUTHWESTERLY LLVL FLOW WILL EVENTUALLY CONVEYOR THIS HIGHER
THETA-E POOL UP ACRS THE SOUTHERN THIRD OF THE FCST AREA BY LATE
AFTERNOON-EARLY EVENING...AND ENGULF THE ENTIRE CWA TONIGHT.
BEFORE THEN...LARGE COLD CORE SFC ANTICYCLONE WILL LOOK TO
CONTINUE TO MIGRATE EASTWARD OUT OF THE REGION TODAY...WITH
WESTERN FLANK RETURN FLOW EFFECT INCREASING THIS AFTERNOON. THE
WARM MOIST CONVEYOR WILL FEED UP AHEAD AND INTERACT WITH
APPROACHING SHORT WAVE NOW ACRS THE EASTERN GRT BSN REGION FOR A
PRECIP EVENT TONIGHT...WITH ENOUGH SATURATION DEPTH FOR PRECIP TO
DEVELOP NOT OCCURRING UNTIL AFTER 00Z FOR MOST OF THE CWA. BUT
SOME SIGNALS OF TRANSPORT BEING QUICKER THAN SEVERAL OF THE SHORT
RANGE MODELS INDICATE AND WILL KEEP SLIGHT CHC POPS IN THE FAR
SOUTHWESTERN CWA AFTER 22Z THIS AFTERNOON. TEMPS WILL BE WARMING
THROUGH THE DAY WITH HIGHS NOT TIL LATE AFTERNOON. WILL KEEP
PREVIOUS SHIFT/S TRENDS OF SIDING WITH MORE OF A GFS/ECMWF TEMP
BLEND AND THROW AWAY THE NAM WITH IT/S COLD BIAS/FALSE SNOWPACK
FEEDBACK. COLD GROUND...VERY COLD START TO THE DAY AND INCREASING
CLOUD COVER THIS AFTERNOON WILL HAVE ITS/ EFFECTS ON TEMPS HOWEVER
SO AM A BIT HESITANT ON GOING AS WARM AS THE ECMWF OR GFS BUT WILL
STILL LEAN THAT WAY FOR NOW FOR CONSISTENCY. IF PRECIP DOES MANAGE
TO GET INTO THE SOUTHERN CWA BEFORE 00Z...EVEN IF AMBIENT TEMPS
RISE ABOVE 32 DEGREES DOWN THERE...COLD FROZEN GROUND WILL MAKE
THE CHC FOR FREEZING RAIN ON GROUND CONTACT.

TONIGHT...KEEPING THE TREND OF COLD FROZEN GROUND AND RAIN
INCREASING OR EVEN TRENDING TO A SHOWERY REGIME AS UPPER WAVE
APPROACHES AND WITH SEVERAL MODELS INDICATING SOME LOW TO MID
LAYER/ELEVATED UNSTABLE LAPSE RATES...WILL GO WITH A CWA-WIDE
FREEZING RAIN ADVISORY. WILL INCREASE THE POPS TO LIKELY FROM SOUTH
TO NORTH AS THE EVENING AND OVERNIGHT PROGRESS. THE SOUTHERN THIRD
OF THE DVN CWA WILL START AT 00Z AND GO TO 09Z SAT MORNING...AREAS
TO THE NORTH OF THAT WILL START AT 03Z AND RUN TO 12Z SAT MORNING.
EVEN AS LLVL WARM AIR ADVECTION TRENDS TEMPS AND THE BOUNDARY LAYER
ABOVE FREEZING FROM NORTH TO SOUTH AS THE NIGHT PROGRESSES...
WORRIED ABOUT THE REFRIGERATION EFFECT OF FROZEN GROUND STILL
PRODUCING FREEZING ON CONTACT AS THE RAIN CONTINUES. DEPENDING ON
TEMP AND PRECIP TRENDS WITH THIS IN MIND...THE NEXT SHIFT MAY HAVE
TO TWEAK START AND END TIMES OF THE FREEZING RAIN ADVISORIES AS THEY
SEE HOW THINGS EVOLVE TODAY....JUST WANTED TO GET A GOOD BASE IN
THERE FOR TONIGHT. TEMPS MAY HAVE AN INITIAL DROP OFF WITH EVAPO
COOLING IN THE EVENING...BUT GENERAL NON-DIURNAL STEADY TO SLOW RISE
OVERNIGHT INTO SAT MORNING. SEVERAL OF THE MODELS HAVE TRENDED
HIGHER WITH QPF TONIGHT OF SWATHS OF 0.10 TO OVER TWO TENTHS
COMBINING LIFT AND SATURATION. BUT WITH OVER SATURATION BIAS OF
SEVERAL RUNS MAY MAKE FOR MORE OF A WIDESPREAD 0.05 TO AROUND A
TENTH OF AN INCH. AS FOR ICE ACCUMS...WILL STICK WITH A LIGHT GLAZE
ESPECIALLY INITIALLY AS LATENT HEAT FROM ADDITIONAL RAINFALL POSSIBLY
AT TIMES OF A MODERATE SHOWER FROM MID EVENING INTO THE OVERNIGHT EAT
AT A THICKER BUILD UP ESPECIALLY ON ELEVATED SURFACES.    ..12..

.LONG TERM...(SATURDAY THROUGH NEXT THURSDAY)
ISSUED AT 402 AM CST FRI NOV 21 2014

NUMEROUS WEATHER CHALLENGES IN THE LONG TERM PERIOD...INCLUDING
POTENTIAL FOR DENSE FOG...LOCALLY HEAVY RAIN ON FROZEN
GROUND...FOLLOWED BY A CLIPPER SYSTEM WITH POSSIBLE ACCUMULATING
SNOW.

ON SATURDAY...EXPECT PERIODS OF LIGHT RAIN/DRIZZLE AND LOW
CLOUDS/FOG THROUGH THE DAY. HAVE TEMPERED AFTERNOON HIGHS INTO THE
LOW 40S/LOW 50S DUE TO THE EXTENSIVE CLOUD COVER/PRECIP. FOG WILL
BECOME MORE WIDESPREAD SATURDAY NIGHT WITH MOISTURE ADVECTING OVER
THE STILL COLD SOIL. WOULD NOT BE SURPRISED IF A DENSE FOG ADVISORY
WILL BE NEEDED EVENTUALLY OVER MUCH OF THE FORECAST AREA. OVERNIGHT
LOWS WILL HOLD UP IN THE UPPER 30S/MID 40S.

FOR SUNDAY...AN UNSEASONABLY POTENT SURFACE CYCLONE WILL PUSH
NORTHEAST THROUGH THE REGION...SPREADING WIDESPREAD RAIN ACROSS
EASTERN IOWA AND NORTHWEST ILLINOIS. THE CONSENSUS OF THE SYNOPTIC
MODELS SUPPORTS THE HEAVIER RAIN ALONG AND EAST OF THE MISSISSIPPI
RIVER...WITH TOTAL AMOUNTS OF AN INCH OR MORE A GOOD BET. WITH THE
FROZEN GROUND...SIGNIFICANT RUNOFF IS EXPECTED...POTENTIALLY
PROBLEMATIC FOR AREA RIVERS. WILL BE WATCHING THE HYDRO SITUATION
CLOSELY INTO NEXT WEEK.

COLDER AIR WILL BEGIN TO SURGE INTO THE FORECAST AREA SUNDAY
NIGHT...AND COULD SUPPORT A CHANGE OVER TO SNOW...ESPECIALLY ACROSS
THE WESTERN COUNTIES. FOR MONDAY THROUGH THANKSGIVING DAY...EXPECT
COLDER TEMPERATURES...WITH AFTERNOON HIGHS IN THE 20S AND 30S...AND
OVERNIGHT LOWS IN THE TEENS TO LOWER 20S. ADDITIONAL SIGNIFICANT
WEATHER INCLUDES WINDY CONDITIONS...POSSIBLY NEAR ADVISORY
CRITERIA...AND MORE LIGHT SNOW ON MONDAY...THEN THE POTENTIAL FOR A
CLIPPER SYSTEM WHICH COULD BRING ACCUMULATING SNOW TO THE AREA ON
WEDNESDAY.    RP KINNEY

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1212 AM CST FRI NOV 21 2014

IFR CONDITIONS EXPECTED BEGINNING MAINLY AFTER 02Z/SAT. MOISTURE
WILL RAPIDLY STREAM IN FROM THE S/SW LATE THIS AFTN WHICH WILL
DROP CIGS AND VSBYS TO LESS THAN 1 KFT AGL AND BETWEEN 1-3 SM
LATER THIS EVENING. MAIN CONCERN BETWEEN 02Z-07Z/SAT IS -FZRA
WHICH WILL TRANSITION TO -FZDZ AFTER THIS TIME. AS SFC TEMPS
SLOWLY WARM ABOVE FREEZING FROM SOUTH TO NORTH...A TRANSITION TO
-DZ WILL OCCUR...LIKELY NOT REACHING KDBQ UNTIL AROUND 12Z/SAT.
CIGS MAY OCCASIONALLY DROP TO LIFR DURING THIS PERIOD AS WELL.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...FREEZING RAIN ADVISORY FROM 9 PM THIS EVENING TO 6 AM CST
     SATURDAY FOR BENTON-BUCHANAN-CEDAR-CLINTON-DELAWARE-DUBUQUE-
     IOWA-JACKSON-JOHNSON-JONES-KEOKUK-LINN-LOUISA-MUSCATINE-
     SCOTT-WASHINGTON.

     FREEZING RAIN ADVISORY FROM 6 PM THIS EVENING TO 3 AM CST
     SATURDAY FOR DES MOINES-HENRY IA-JEFFERSON-LEE-VAN BUREN.

IL...FREEZING RAIN ADVISORY FROM 9 PM THIS EVENING TO 6 AM CST
     SATURDAY FOR BUREAU-CARROLL-HENRY IL-JO DAVIESS-MERCER-
     PUTNAM-ROCK ISLAND-STEPHENSON-WHITESIDE.

     FREEZING RAIN ADVISORY FROM 6 PM THIS EVENING TO 3 AM CST
     SATURDAY FOR HANCOCK-HENDERSON-MCDONOUGH-WARREN.

MO...FREEZING RAIN ADVISORY FROM 6 PM THIS EVENING TO 3 AM CST
     SATURDAY FOR CLARK-SCOTLAND.

&&

$$

SHORT TERM...12
LONG TERM...RP KINNEY
AVIATION...UTTECH





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