Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 231017
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
417 AM CST SUN NOV 23 2014

.SYNOPSIS...
ISSUED AT 415 AM CST SUN NOV 23 2014

LATEST SFC ANALYSIS WAS INDICATING A DEVELOPING SFC LOW JUST NORTH OF
THE OK PANHANDLE...WITH AN EVEN DEEPER SECONDARY LOW ACRS THE NORTH
DAKOTA/CANADIAN BORDER REGION. THE MAIN WARM FRONT CONNECTED TO
THIS DEVELOPING FRONTAL COMPLEX ACRS THE PLAINS WAS CURRENTLY LAID
OUT FROM WEST TO EAST ACRS THE EASTERN DAKOTAS...MN...WI AND WESTERN
LOWER MI. THE DVN CWA BATHED IN FULL ON WARM SECTOR WITH SFC DPTS
IN THE UPPER 40S TO AROUND 50 AND AMBIENT TEMPS SIMILAR OR A FEW
DEGREES WARMER. MIXING SOUTHERLY BREEZE LIMITING FOG PRODUCTION FOR
NOW. WATER VAPOR IMAGERY INDICATING MAIN SLUG OF UPPER WAVE ENERGY
ORGANIZING ACRS THE GRT BSN REGION IN DEEPENING L/W TROF BASE...
GETTING READY TO EJECT OUT TOWARD THE MID MS RVR VALLEY BY LATE
TONIGHT/MON MORNING.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 415 AM CST SUN NOV 23 2014

TODAY...ANALYZING SEVERAL OF THE 00Z MODEL RUNS AND EVOLVING
SITUATION UPSTREAM ACRS THE SOUTHEAST PLAINS...IT APPEARS A SREF
BLEND OF INCOMING SYSTEM AND SYNOPTIC SCALE FEATURE IN ORDER WITH
MINOR ADJUSTMENTS. FCST SOUNDINGS SUPPORT IDEA OF ENHANCED WARM
MOIST CONVEYOR IN 40+ KT LOW TO MID LEVEL SOUTHERLY FLOW TO
EVENTUALLY DEEPENING SATURATION TO AN EXTENT THAT PWATS REACH 1
INCH OR MORE BY AFTERNOON...OVER 200 PERCENT OF NORMAL FOR THIS
TIME OF YEAR. DEEPENING LIFT AND IDEAL INITIAL SURGE OF MID TO UPPER
JET ENERGY IN AMPLIFYING SOUTHWESTERLIES TO WRING OUT THIS MOISTURE
PLUME IN A FORM OF VIGOROUS OVERRUNNING RAIN OR SHOWER COMPLEX...
CURRENTLY DEVELOPING NOW ACRS AR INTO MO...THAT WILL BUILD UP ACRS
THE HEART OF THE DVN CWA AS THE DAY PROGRESSES. BEFORE MAX SATURATION
DEPTH IS ACHIEVED...THERE MAY EVEN BE SOME EMBEDDED THUNDER IN AT
LEAST THE SOUTHERN HALF OF THE CWA BUT FOR NOW WILL LEAVE OUT
MENTION. EXTENT OF LIFT COMBINED WITH SATURATED PROFILES SUPPORTS
MUCH OF THE CWA GETTING AVERAGE RAINFALL AMOUNTS BY LATE EVENING
WHEN THE RAIN TAPERS TO LIGHTER RAIN AND DRIZZLE...OF 0.75 TO 1.2
INCHES. SOME LOCALLY HIGHER AMOUNTS PUSHING AN INCH AND A HALF MAY
ALSO OCCUR. WITH PARTIALLY FROZEN GROUND AND DORMANT VEGETATION...
THIS TYPE OF RAINFALL WILL EVENTUALLY PRODUCE QUITE A BIT OF RUN OFF
THAT WILL PRODUCE SOME STANDING WATER IN DRAINAGE DITCHES AND OTHER
LOW LYING AREAS. SOME NUISANCE/MINOR URBAN FLOODING POSSIBLE AS
WELL. WHILE RIVERS ARE LOW AND WILL ABSORB THE RUN-OFF WITH JUST IN-
BANK RISES...SOME SMALLER CREEKS MAY GET TO BANKFULL OR EVEN HIGHER
BY EVENING. WITH CURRENT TEMP IN THE UPPER 40S TO LOWER 50S...IT
WON/T TAKE LONG TO GET TO PROJECTED HIGHS FOR TODAY EVEN WITH
PRECIP BECOMING WIDESPREAD.

TONIGHT...ACCEPTED SREF SFC LOW TRACK ALMOST UP THE MS RVR THIS
EVENING WILL PRODUCE A CONVERGENT LIGHTER WIND ZONE FROM NORTH TO
SOUTH ON EITHER SIDE OF THE WAVE. THIS WOULD BE A TEMPORARY FOG
FORMING AREA...POSSIBLY DENSE...IF THE RAINFALL TEMPORARILY LETS UP
ENOUGH OR TRANSITIONS TO MORE OF A DRIZZLE PHENOMENA. WILL KEEP THE
PATCHY FOG MENTION FOR NOW. AS THE SFC LOW LOOKS TO DEEPEN TO THE
LOW 980/S AND PROPAGATE TOWARD NORTHEASTERN IL OR SOUTH CENTRAL WI BY
MON MORNING...UPPER TROF AXIS STILL OFF TO THE WEST AND H85 TO H7 MB
LOW WILL LOOK TO ROLL RIGHT ACRS THE CWA AND PRODUCE A SECONDARY DEF
ZONE PRECIP BAND ACRS THE CWA FROM MIDNIGHT INTO MON MORNING. WITH
INCREASING LLVL COLD CONVEYOR IN SHARPLY VEERING LLVL WIND
PROFILES...THE RACE WILL BE ON TO COOL THERMAL PROFILES ENOUGH FOR A
TRANSITION TO RAIN-SNOW MIX AND THEN ALL SNOW FROM WEST-TO-EAST.
SEVERAL SOLUTIONS REALLY VARY IN TIMING OF THIS OCCURRENCE AND AMOUNT
OF LEFT OVER PRECIP TO TURN TO SNOW BY 12Z MON. WILL AGAIN USE A SREF
BALANCE AND LOOKING AT BUFKIT SOUNDINGS FOR NOW WHICH SUGGESTS
RAIN/SNOW MIX INTO THE FAR WESTERN CWA FROM 07Z-09Z...INCLUDING
CEDAR RAPIDS DOWN TO FAIRFIELD IA...AND THE MIX REACHING THE MS RVR
BY AROUND 11Z TO 12Z MON. A SWITCH OVER TO ALL SNOW AFTER 09Z FROM
MANCHESTER IA...TO IOWA CITY...TO MOUNT PLEASANT IN SOUTHEAST IA...
TO EVEN MEMPHIS IN NORTHEAST MO WITH A HALF INCH TO POSSIBLY AN INCH
OF SNOW ACCUM WEST OF THIS LINE POSSIBLE BY DAWN MON MORNING. SURGING
NORTHWEST WINDS OF 15 TO 25 MPH AND HIGHER GUSTS MAY REALLY LIMIT
VISIBILITIES IN THE SNOW BANDS LATE TONIGHT AND THERE MAY BE A
EVENTUAL NEED FOR AN WINTER WX ADVISORY FROM LATE TONIGHT INTO MON.
MORE MONDAY DETAILS IN DISCUSSION BELOW. A FEW MODELS SUCH AS THE 00Z
RUN ECMWF EVEN SUGGESTS HEAVIER SNOW FURTHER SOUTH WITH SEVERAL
INCHES POSSIBLE BY 12Z MON SOUTHWEST OF A FAIRFIELD...TO BURLINGTON
IA LINE...IN A HANG-BACK DEF ZONE PRECIP BAND PLENTY COOLED OFF
ENOUGH FOR ALL SNOW AT THE SFC.THIS A DEVIATION FROM PREVIOUS RUNS
AND WILL NOT JUMP ON YET...BUT AGAIN THE 12Z SUNDAY MODEL RUNS WILL
HAVE TO BE SCRUTINIZED FOR POSSIBLE HEADLINES LATE TONIGHT INTO
MONDAY.     ..12..


.LONG TERM...(MONDAY THROUGH NEXT SATURDAY)
ISSUED AT 415 AM CST SUN NOV 23 2014

MAIN FORECAST CONCERNS IN THE LONG TERM FOCUSED ON POTENTIAL
ADVISORY LEVEL SNOW/BLOWING SNOW EVENT MONDAY AND A CLIPPER SYSTEM
AHEAD OF THE THANKSGIVING HOLIDAY.

ON MONDAY...SYNOPTIC MODELS HAVE NARROWED TO A GENERAL CONSENSUS
FAVORING A MORE WIDESPREAD SNOW EVENT ACROSS THE FORECAST AREA. ANY
LINGERING RAIN/SNOW MIX IN FAR NW ILLINOIS MONDAY MORNING WILL
QUICKLY CHANGE OVER TO ALL SNOW...WITH HIGH TEMPERATURES MOST AREAS
OCCURRING IN THE MORNING. BELIEVE 12Z-18Z WPC QPF IS SOMEWHAT
UNDERDONE GIVEN THE TRENDS TOWARD A MORE POTENT SYSTEM...AND HAVE
BLENDED WITH THE MORE ROBUST ECMWF. HAVE BOOSTED SNOWFALL AMOUNTS
FROM PREVIOUS FORECAST. STORM TOTALS FROM SUNDAY NIGHT THROUGH
MONDAY NIGHT ARE NOW AN INCH OR LESS SOUTH OF HIGHWAY 34...1-3
INCHES NORTH OF HIGHWAY 34 WITH THE HIGHEST AMOUNTS FROM DUBUQUE TO
FREEPORT. THE 12KM NAM HAS SIGNALS OF AN ENHANCED SNOW
BAND...CERTAINLY SOMETHING TO WATCH CLOSELY WITH FUTURE RUNS.

EVEN THOUGH FORECAST SNOWFALL AMOUNTS ARE CURRENTLY
SUB-ADVISORY...THE COMBINATION OF SNOW AND BLOWING SNOW FROM A
STRONG W/NW WIND MAY VERY WELL WARRANT HEADLINES...ESPECIALLY WITH
POTENTIAL IMPACTS DURING THE MORNING COMMUTE. WILL PASS CONCERNS TO
LATER SHIFTS TO EVALUATE SNOWFALL PLACEMENT/AMOUNTS AND FAVORED
AREAS FROM IMPACTS FROM BLOWING SNOW. GUSTS OF 35-40 MPH WITH
PERIODS OF MODERATE SNOWFALL INTENSITY WOULD EASILY DROP
VISIBILITIES BELOW A HALF MILE...ESPECIALLY FROM MID MONDAY MORNING
THROUGH MID AFTERNOON. LIGHT SNOW WILL TAPER OFF IN THE FAR
NORTHEAST MONDAY EVENING.

LOOKING AHEAD...A CLIPPER SYSTEM STILL LOOKS ON TRACK FOR LATE
TUESDAY NIGHT AND WEDNESDAY. SNOWFALL AMOUNTS DO NOT LOOK VERY
IMPRESSIVE RIGHT NOW...PERHAPS AN INCH OR TWO...BUT ANY SNOW DURING
PRE-HOLIDAY TRAVEL WOULD NOT BE WELCOME. EXPECT A COLD AND MAINLY
DRY THANKSGIVING DAY WITH HIGHS IN THE LOW 20S TO LOW 30S. THE
23/00Z ECMWF IS INDICATING POTENTIAL FOR MORE LIGHT SNOW ON
FRIDAY...BUT WILL NOT JUMP ON THIS LATEST RUN YET.    RP KINNEY

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1134 PM CST SAT NOV 22 2014

THE POTENTIAL FOR FOG AND DRIZZLE TONIGHT HAS DIMINISHED
CONSIDERABLY AND THE TRANSITION TO PREVAILING IFR CONDITIONS HAS
BEEN DELAYED IN THE LATEST FORECASTS. CIGS WILL LIKELY BECOME IFR
BEFORE SUNRISE...WITH VISIBILITIES LOWERING TO AN MVFR RANGE. AS A
DEVELOPING STORM SYSTEM APPROACHES FROM THE PLAINS...RAIN AND FOG WILL
OVERSPREAD THE TERMINALS IN THE MORNING AND CONTINUE THROUGH THE
DAY WITH PREVAILING IFR CONDITIONS AND PERIODS OF IFR OR EVEN LIFR
FROM LATE AFTERNOON TOWARD EVENING AS THE POTENTIAL FOR DENSE FOG
INCREASES. A LATE EVENING FRONTAL PASSAGE WILL LIKELY BRING A
SHIFT IN WINDS FROM SOUTH TO WEST OR NORTHWEST...FOLLOWED BY
PRECIPITATION CHANGING FROM RAIN...OR A RAIN/SNOW MIX...TO ALL
SNOW...JUST BEYOND THE RANGE OF THE CURRENT FORECASTS LATE SUNDAY
NIGHT.

&&

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

$$

SYNOPSIS...12
SHORT TERM...12
LONG TERM...RP KINNEY
AVIATION...SHEETS





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