FXUS63 KDVN 232140
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
340 PM CST WED DEC 23 2009
.SYNOPSIS...
WIDESPREAD PRECIPITATION WAS COVERING THE ENTIRE FORECAST AREA THIS
AFTERNOON AS THE LARGE...COMPLEX OF UPPER SYSTEMS CONTINUE TO EVOLVE
AND DEEPEN OVER THE S CENTRAL AND WESTERN CONUS. UPPER FORCING AND
ISENTROPIC LIFT AHEAD OF THE LEAD SHORTWAVE OVER NE KS THIS
MORNING...LIFTING OVER THE SHALLOW COLD AIR AND STRONG E-NE LOW
LEVEL FEED OF RELATIVELY COLD DRY AIR OUT OF AN ONTARIO HIGH HAS
RESULTED IN WIDESPREAD FREEZING RAIN. RESULTING ICE ACCUMULATIONS
HAVE SO FAR BEEN PRIMARILY NORTH OF I-80. THE MAIN UPPER LOW
WAS EVIDENT ON WV IMAGERY OVER CENTRAL NM THIS AFTERNOON...WITH
ANOTHER STRONG UPPER LOW DROPPING SOUTH OUT OF ALBERTA. AT THE
SURFACE...AN INVERTED TROUGH WAS IN PLACE OVER THE MO
VALLEY...EXTENDING NORTH FROM A WEAK LOW IN NE OK. STRONG LOW LEVEL
E-NE WINDS BETWEEN THE TROUGH AND A HIGH OVER ONTARIO WAS FEEDING
SUB FREEZING TEMPERATURES AND WET BULB TEMPERATURES INTO NRN IL AND
NE IA UNDER THE STRONG WARM ADVECTION PATTERN ABOVE H9. WIDESPREAD
PRECIPITATION TO CONTINUE OVER THE NEXT 48 HOURS AS THE NORTHERN AND
SOUTHERN STREAM LOWS PHASE INTO A LARGE UPPER LOW NEARLY OVER THE
FORECAST AREA BY THE WEEKEND.
&&
.SHORT TERM...TONIGHT AND THURSDAY...
THE INITIAL CHALLENGE IS HOW MUCH ADDITIONAL ICE ACCUMULATIONS WILL
OCCUR THIS EVENING WITH FREEZING RAIN AND DRIZZLE ACROSS THE NORTH.
WITH CONTINUED SLOW NORTHWARD MIGRATION OF THE 32 DEGREE SURFACE
ISOTHERM SHOWN BY SHORT TERM MODELS...WILL DROP THE SOUTHERN
COUNTIES OF THE CURRENT WINTER WX ADVISORY AND KEEP THE NORTHERN
GOING UNTIL 00Z. THIS NORTHWARD MOVEMENT AND SFC TO 925 MB WINDS
BECOMING MORE SE WITH TIME SHOULD EVENTUALLY ALLOW THE ENTIRE CWA TO
CLIMB ABOVE FREEZING OVERNIGHT. MAIN CONCERN IS THAT THIS MAY BE A VERY SLOW
PROCESS...AND THE UPPER 20S DEWPOINTS AND SUB FREEZING WETBULB
TEMPERATURES ADVECTING IN ON THE CURRENT E-NE WINDS OUT OF SRN WI
AND NRN IL MAY KEEP EVAPORATIVE COOLING AND FREEZING PROCESSES GOING
IN THE NORTH. WILL KEEP A STRONGLY WORDED ADVISORY GOING FOR
ADDITIONAL ICE ACCUMULATIONS AND MINOR SNOW/SLEET ACCUMULATIONS IN
THE NRN 2 TIERS OF COUNTIES THROUGH THE NIGHT COUNTING ON THE
WARMING TO EVENTUALLY WIN OUT AND A BACK EDGE IN THE PRECIP ON 88D
IN S CENTRAL IA TO SLOW ACCUM RATES. HAVE ALREADY HAD NUMEROUS REPORTS OF
QUARTER INCH AND A ISOLATED HALF INCH REPORTS OF ICE ACCUMS SO FAR
IN EAST CENTRAL IA TODAY...BUT THIS HAS BEEN PRIMARILY ON ELEVATED
SURFACES SURFACES.
THURSDAY...DEVELOPING H8 LOW SHOWN IN ALL MODELS OVER WESTERN AR
WITH RESULTING INVERTED TROUGH INTO THE DAKOTAS. A LOW LEVEL JET OF
50 TO 60KTS OR MORE EAST OF THESE FEATURES AIMS NEARLY DIRECTLY
INTO THE FORECAST AREA SUPPORTING WIDESPREAD MODERATE TO HEAVY RAIN
AND WILL KEEP FLOOD WATCH GOING AS 1 TO 2 INCH AMOUNTS STILL
REASONABLE. DEEP IN THE WARM ADVECTION...TEMPERATURES WILL BE WELL
INTO THE 30S TO LOWER 40S...EXCEPT IN THE FAR N AND NW AND HAVE A
MENTION OF LIGHT MIXED PRECIP THERE.
.LONG TERM...THURSDAY NIGHT THROUGH WEDNESDAY...
...LARGE...STRONG AND SLOW MOVING WINTER STORM SYSTEM THROUGH SATURDAY
MAJOR FORECAST ISSUE THIS CYCLE...
OVERVIEW...MODEL INITIALIZATION AVERAGE WITH MISSING NW MEXICO UPPER
AIR OBS IMPACTING QUALITY OF THESE RUNS. ALL NOWCAST TOOLS AND
ANALYSIS FIELDS SUGGEST SW CONUS SYSTEM STRONGER...SLOWER AND
FURTHER SOUTH. QUESTION IS HOW MUCH. UKMET INITIALIZES AND VERIFIES
BEST AT 18Z WITH THIS ENERGY ISSUE. GOOD CONFIDENCE OF MAJOR
PHASING OF SW AND NW UPPER LOWS OVER FORECAST AREA...CALLED THE
"FUJIWARA EFFECT". MAIN ISSUE IS SPEED OF CYCLOGENESIS FROM LATENT
HEAT RELEASE IN SOUTH PLAINS IMPACTING RATE OF OCCLUSION AND
EVENTUAL LOW TRACK AND WEATHER FOR THE FORECAST AREA. ANALYSIS
SUGGEST THIS MAY NOT BE ABLE TO FULLY CLARIFIED UNTIL THURSDAY
WHEN THIS ENERGY MOVES INTO TEXAS.
THURSDAY NIGHT...STRONG SURFACE LOW TO MOVE INTO FAR NE MISSOURI WITH
ALL TECHNIQUES SUPPORTING SEASONALLY HEAVY OVERNIGHT RAINS OF .5
UP TO 1.5 INCHES. STRONG EAST WINDS OF 20 TO 35+ MPH WITH TEMPS IN
30S TO MAKE FOR A COLD AND RAW NIGHT. "LIFT" TOOL...ALL SOLUTIONS
SUPPORT ISOLATED EMBEDDED THUNDER FROM STRONG UPPER LEVEL FORCING
AND HAVE ADDED TO FORECAST. AREAS NORTH OF HIGHWAY 30 STILL INDICATE
RISK OF FREEZING AND SLEET AS ENE ISALLOBARIC WIND USHERS IN COLDER
AIR. THIS COULD PRODUCE LOCALLY SIGNIFICANT ICE..MAINLY ON ELEVATED
SURFACES THERE. THUS...HAVE KEPT EXISTING WINTER STORM WATCH IN PLACE
FOR LATER SHIFTS TO RECONSIDER AS PATH AND TRACK BETTER CLARIFIED.
FRIDAY AND FRIDAY NIGHT...RAPIDLY FALLING DAY TEMPERATURES AS COLD AIR
MOVES IN FROM WITH WEST ON STRONG SOUTHWEST TO WEST WINDS OF 20 TO 35+
MPH WITH GUST TO 45 MPH POSSIBLE. LOCAL TECHNIQUES SUPPORTS A MIX OF
SNOW AND SLEET...CHANGING TO ALL SNOW VERY QUICKLY. FAR NORTHWEST AND
WEST SECTIONS MAY EXPERIENCE SIGNIFICANT SNOW AMOUNTS WITH WRAPAROUND
MOISTURE DEPENDING OF SFC LOW TRACK. BEST ESTIMATE IS 2 TO 5 INCHES
ATTM THERE...THIS COULD RESULT IN SOME BLOWING AND DRIFTING SNOW BY
FRIDAY NIGHT AND HAVE EXTENDED WATCH UNTIL SATURDAY MORNING...OTHER
LOCATIONS MAY NEED TO BE ADDED IF SURFACE LOW TRACK IS MUCH FURTHER
EAST...AS TRENDS PAST 24 HOURS HAVE SUGGESTED.
SATURDAY AND SATURDAY NIGHT...LINGERING SNOW AND WIND WITH ADDITIONAL
LIGHT ACCUMULATIONS UP TO 2 INCHES POSSIBLE. LOWERED TEMPERATURES A
FEW DEGREES. DEPENDING ON TRACK OF SURFACE LOW...STRONGER WINDS MAY
NEED TO BE ADDED.
SUNDAY THROUGH WEDNESDAY...SEASONABLY COLD AND DRY...SOME LIGHT SNOW
STILL POSSIBLE SUNDAY. THEN DRY REST OF THE PERIOD WITH SOME INDICATIONS
LIGHT PRECIPITATION POSSIBLE WEDNESDAY WITH NEXT PACIFIC SYSTEM. WILL
RECONSIDER POPS CHANCES TOMORROW. FORCING SUGGEST ANY PRECIPITATION
WOULD BE LIGHT AND IN THE FORM OF SNOW. ..NICHOLS..
&&
.AVIATION...
WIDESPREAD IFR...AND PERIODS OF LIFR CONDITIONS TO CONTINUE
OVERNIGHT INTO THU WITH WIDESPREAD PRECIPITATION. THE PRECIPITATION
HAS CHANGED TO RAIN AT BRL AND MLI...WHILE CID AND DBQ WILL HAVE
PERIODS OF FREEZING RAIN...POSSIBLY MIXED WITH SLEET AND SNOW...WELL
INTO THE 00Z TO 06Z PERIOD BEFORE CROSSING OVER TO ALL RAIN. BRISK
EAST WINDS FROM 15 TO 25 KTS WILL HAVE THE POTENTIAL FOR GUSTS OVER
30 KTS ON THU...MAINLY BEYOND THE FORECAST PERIODS. AN ISOLATED
THUNDERSTORM IS ALSO POSSIBLE THU...BUT TOO LOW POTENTIAL FOR
INCLUSION IN FORECASTS AT THIS TIME. ..SHEETS..
&&
.HYDROLOGY...
STORM TOTALS OF 1.5 TO 2.5 INCHES OF RAIN ON TOP OF COLD...FROZEN GROUND
AND DENSE SNOW-PACK...ESPECIALLY ALONG AND NORTH OF I-80 CREATE A FAVORABLE
ENVIRONMENT OF FLOODING IN LOW LYING LOCATIONS. ICE JAMS ON RIVERS AND
TRIBUTARIES ARE POSSIBLE DUE TO RISING WATER LEVELS AND MELTING SNOW
AND ICE THAT COULD CREATE SIGNIFICANT FLOODING ALONG AREA RIVERS. A
FLOOD WATCH IS IN EFFECT UNTIL FRIDAY MORNING OVER THE AREA. ..NICHOLS..
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...FLOOD WATCH FROM THURSDAY MORNING THROUGH LATE THURSDAY NIGHT
FOR BENTON-BUCHANAN-DELAWARE-DUBUQUE-JACKSON-JONES-LINN.
WINTER WEATHER ADVISORY UNTIL 6 AM CST THURSDAY FOR BENTON-
BUCHANAN-DELAWARE-DUBUQUE-JACKSON-JONES-LINN.
WINTER STORM WATCH FROM THURSDAY EVENING THROUGH LATE FRIDAY
NIGHT FOR BENTON-BUCHANAN-DELAWARE-DUBUQUE-JACKSON-JONES-
LINN.
FLOOD WATCH THROUGH LATE THURSDAY NIGHT FOR CEDAR-CLINTON-DES
MOINES-HENRY IA-IOWA-JEFFERSON-JOHNSON-KEOKUK-LEE-LOUISA-
MUSCATINE-SCOTT-VAN BUREN-WASHINGTON.
WINTER WEATHER ADVISORY UNTIL 6 PM CST THIS EVENING FOR CEDAR-
CLINTON-IOWA-JOHNSON-SCOTT.
IL...FLOOD WATCH FROM THURSDAY MORNING THROUGH LATE THURSDAY NIGHT
FOR CARROLL-JO DAVIESS-STEPHENSON.
WINTER WEATHER ADVISORY UNTIL 6 AM CST THURSDAY FOR CARROLL-JO
DAVIESS-STEPHENSON.
WINTER STORM WATCH FROM THURSDAY EVENING THROUGH LATE FRIDAY
NIGHT FOR JO DAVIESS.
FLOOD WATCH THROUGH LATE THURSDAY NIGHT FOR BUREAU-HANCOCK-
HENDERSON-HENRY IL-MCDONOUGH-MERCER-PUTNAM-ROCK ISLAND-
WARREN-WHITESIDE.
WINTER WEATHER ADVISORY UNTIL 6 PM CST THIS EVENING FOR
WHITESIDE.
MO...FLOOD WATCH THROUGH LATE THURSDAY NIGHT FOR CLARK-SCOTLAND.
&&
$$
SHEETS/NICHOLS
