FXUS63 KDVN 070930
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
330 AM CST MON DEC 7 2009
.SYNOPSIS...
00Z UA ANALYSIS HAS A RESPECTABLE SHORTWAVE OVER NORTHEAST KANSAS
WITH A LLJ OF 30-40 KTS RUNNING FROM EASTERN TEXAS INTO MISSOURI.
SATELLITE TRENDS SHOW PLENTY OF LOW CLOUDS RUNNING FROM THE WESTERN
GREAT LAKES INTO THE LOWER MISSISSIPPI VALLEY WITH RADAR INDICATING
LIGHT SNOW FROM THE WESTERN SHORES OF LAKE MICHIGAN BACK TO THE
MISSOURI RIVER. 06Z SFC ANALYSIS HAS THE LOW BETWEEN KCDJ AND KDMO
WITH A STATIONARY FRONT RUNNING NORTHEAST ACROSS NORTHERN ILLINOIS
INTO LOWER MICHIGAN. A COLD FRONT RAN FROM THE LOW SOUTHWEST INTO
CENTRAL TEXAS. DEW POINTS WERE GENERALLY IN THE 20S AHEAD OF THE LOW
WITH 30 DEW POINTS FROM CENTRAL MISSOURI INTO THE LOWER MISSISSIPPI
VALLEY.
&&
.SHORT TERM...TODAY AND TONIGHT...
CURRENT SYSTEM IS MOVING THROUGH THE AREA WITH GEM DOING THE BEST OF
ANY MODEL REGARDING SFC LOW POSITION AT 06Z. GEM AND 08Z RUC SHOW
LOW CONDENSATION PRESSURE DEFICITS THROUGH MID MORNING BEFORE
INCREASING SUGGESTING MINIMALLY LIKELY POPS EARLY THIS MORNING.
RADAR TRENDS THROUGH 09Z SUGGEST THAT THIS IS THE WAY TO GO.
SO...HIGH CHC TO LIKELY POPS THROUGH MID MORNING WITH PRECIP
SHUTTING DOWN QUICKLY BY MID DAY. SATURATED LOW LEVELS SHOULD LEAVE
THE ATMOSPHERE PRIMED FOR --SN IN THE AFTERNOON WITH ANY PASSING
RIPPLE ALOFT.
FLURRIES SHOULD BE SEEN THIS EVENING AS THE LOWER ATMOSPHERE REMAINS
SATURATED. AFT 06Z THINGS GET MORE INTERESTING. CONDENSATION
PRESSURE DEFICITS BEGIN TO LOWER QUICKLY AGAIN PER THE GEM/ECMWF AND
FORCING INCREASES. THUS EXPECT -SN TO BREAK OUT AS A DEFORMATION
ZONE BEGINS TO DEVELOP WITH THE FIRST VORT MAX. PARTS OF THE
SOUTHWEST TO WEST AREAS OF THE CWFA SHOULD SEE SOME NEW ACCUMULATION
PRIOR TO SUNRISE. ..08..
.LONG TERM...TUESDAY THROUGH NEXT SATURDAY...
...HIGH IMPACT...POTENTIALLY CRIPPLING WINTER STORM TUE/WED REMAINS
THE FORECAST CHALLENGE...
OVERALL INITIALIZATION AND VERIFICATION GOOD. AGAIN...HI-RES ECMWF
THE GEM-NHEM AND NOW UKMET ARE MOST ACCURATE...CONSISTENT AND
RELIABLE. THE GFS AND NAM CONTINUE TO SHOW LATENT HEAT FEEDBACK
ISSUES..THE 06Z NAM FORCING IS SLOWLY GETTING BETTER. THE HI-RES
ECMWF SHOWS THE DEFORMATION ZONE NICELY WEDNESDAY AM WHICH MOST OR
ALL SOLUTIONS SHOULD CAPTURE BY TONIGHT/S RUNS.
OVERVIEW...MINOR CHANGES TO CURRENT PACKAGE EXCEPT UPGRADED WNW 1/2
TO 2/3 ARE FOR BLIZZARD WATCH AS BLIZZARD CONDITIONS WILL OVERSPREAD
AT LEAST ALL THIS REGION AFTER MIDNIGHT TUESDAY NIGHT AND THROUGH
MOST TO ALL OF THE DAY WEDNESDAY. THUNDER-SNOW ALSO EVIDENT MOVING
INTO AREA TUESDAY NIGHT OVER MOST OR ALL THE REGION. SNOW EVENT
AMOUNTS OF 6 TO 12 INCHES REMAIN ON TAP WITH LOCALLY HIGHER AMOUNTS
OF 12+ INCHES...LOCALLY UP TO 15 INCHES SUGGESTED +/- 40 MILES OF A
FREEPORT TO IOWA CITY TO OTTUMWA LINE. THIS SYSTEM REMAINS ON TRACK
TO BE ONE OF THE MOST SIGNIFICANT HIGH IMPACT EVENTS IN THIS AREA FOR
SEVERAL YEARS...IF NOT LONGER.
TUESDAY...HAVE UPPED POPS WITH SNOW OVERSPREADING ALL AREA WITH SNOW
AMOUNTS OF 1 TO 4 PLUS INCHES BY EVENING. HEAVIER SNOW MAY ARRIVE
IN FAR SW SECTION LATE PM THAT LATER SHIFTS MAY NEED TO UP TOTALS
AS LEAD VORT MAX MAY BE STRONGER THAN CURRENT SOLUTIONS INDICATE. NE
WINDS OF 10 TO 20 MPH SHOULD LIMIT SNOW TO JUST MINOR DRIFTING
UNTIL LATER. ALONG AND SOUTH OF HIGHWAY 34 STILL SUGGESTS SNOW...
MIXED AT TIMES WITH SLEET. LOCAL ANALYSIS SUGGEST MOST PRECIPITATION
SHOULD STILL BE SNOW.
TUESDAY NIGHT...A WILD NIGHT WITH SNOW...HEAVY AT TIMES WITH THUNDER-
SNOW AND WINDS INCREASING FROM NW TO SE. LOCAL TOOLS SHOW 1 TO 2
INCH SNOWFALL RATES REMAIN PLAUSIBLE. SOME SUGGESTION OF INTERNAL
GRAVITY WAVES MAY RESULT IN GUSTS AOA 40-45 MPH THAT WOULD CREATE
BRIEF WHITEOUT CONDITIONS FOR LATER SHIFTS TO CONSIDER. BLOWING SNOW
AND AREAS OF BLOWING SNOW TO OCCUR OVER ALL BUT FAR EAST SECTIONS
THAT WILL RENDER TRAVEL CONDITIONS DIFFICULT IF NOT IMPOSSIBLE BY
DAYBREAK. MOST OF THE HEAVIEST SNOW WILL OCCUR IN THIS PERIOD.
WEDNESDAY...EXTREME WINTER STORM WILL RESULT IN LARGE PERIODS AND
AREAS OF BLIZZARD CONDITIONS...POTENTIALLY CRIPPLING THE AREA. OVER A
DOZEN TOOLS INDICATE SUSTAINED WINDS AT LEAST OF 25 TO 40+ MPH WITH
GUSTS OF 50 MPH OR MORE. SUSTAINED WINDS OF 30 TO 45 MPH APPEAR
QUITE PROBABLE WITH SOME GUSTS TO ~55-60 MPH. A VIGOROUS DEFORMATION
ZONE SHOULD REMAIN FROM DBQ TO NEAR BRL THAT WILL LIFT NE TOWARD MID
DAY. WIDESPREAD AND PROLONGED POWER OUTAGES BASED ON PAST SNOW
AMOUNTS AND WIND SPEEDS APPEAR LIKELY. TEMPERATURES WILL FALL
THROUGHOUT THE DAY INTO THE SINGLE DIGITS TO LOWER TEENS BY DUSK.
SNOW TO DIMINISH TO FLURRIES BUT WITH BLOWING SNOW WILL BE HARD TO
ASCERTAIN THE DIFFERENCE UNTIL LATE AFTERNOON MANY LOCATIONS. SNOW
DRIFTS OF 3 TO OVER 6 FEET DEEP WILL BE COMMON BY LATE AFTERNOON.
COMBINE THIS WITH PERIODS OF WHITEOUT CONDITIONS WILL MAKE TRAVEL
CONDITIONS DIFFICULT AT BEST TO IMPOSSIBLE WITH LIFE THREATENING
CONDITIONS POSSIBLE DUE TO VERY LOW WIND CHILLS BELOW ZERO BY
AFTERNOON.
WEDNESDAY NIGHT...WINDS TO DECREASE TO 15 TO 20 MPH BY MIDNIGHT BUT
DEEP DRIFTS MAY KEEP MOST ROADS CLOSED. HAVE TRIMMED LOWS TO NEAR
TO BELOW ZERO AS SKIES CLEAR AND IMPACTS OF A FRESH..DEEP SNOW
COVER. MINS MAY NEED LOWER SEVERAL MORE DEGREES.
THURSDAY AND FRIDAY...FAIR AND COLD. LOWERED TEMPERATURES WITH
SUGGESTION A FURTHER LOWERING OF 2 TO 5 DEGREES APPEARS REASONABLE.
FLURRIES MAY BE POSSIBLE WITH WEAK DISTURBANCES FOR DAY SHIFT TO
CONSIDER.
SATURDAY AND SUNDAY..NO CHANGES MADE. EVIDENCE OF LARGE NEGATIVE
FEEDBACK FROM SNOW COVER WITH CHANGES THAT SHOULD BE BETTER
CLARIFIED TODAY. SUGGESTION OF LIGHT SNOWFALL WITH SLOWLY
MODERATING TEMPERATURES. WINTER HAS ARRIVED. ..NICHOLS..
&&
.AVIATION...
LOW CONDENSATION PRESSURE DEFICITS AND RESPECTABLE FORCING SHOULD
KEEP -SN GOING THROUGH 15Z BEFORE TAPERING TO FLURRIES AND POSSIBLY
ENDING. 1-2SM VSBYS WITH POCKETS OF 3-5SM WILL CONTINUE THROUGH 15Z
BEFORE IMPROVING TO 6SM. FCST SOUNDINGS SUGGEST A TRAPPING INVERSION
KEEPING CIGS GENERALLY IN THE 1-2KFT RANGE. AFT 06Z/08 INCREASED
FORCING AND LOWERING CONDENSATION PRESSURE DEFICITS TO INITIATE THE
NEXT ROUND OF -SN BY 09Z/08. KCID MAY SEE CIGS BLO 1KFT PRIOR TO
12Z/08. KBRL/KMLI/KDBQ CIGS/VSBYS TO QUICKLY DETERIORATE AFT 12Z/08.
..08..
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...BLIZZARD WATCH FROM TUESDAY MORNING THROUGH WEDNESDAY AFTERNOON
FOR BENTON-BUCHANAN-CEDAR-CLINTON-DELAWARE-DES MOINES-
DUBUQUE-HENRY IA-IOWA-JACKSON-JEFFERSON-JOHNSON-JONES-
KEOKUK-LEE-LINN-LOUISA-MUSCATINE-SCOTT-VAN BUREN-WASHINGTON.
IL...BLIZZARD WATCH FROM TUESDAY MORNING THROUGH WEDNESDAY AFTERNOON
FOR CARROLL-JO DAVIESS-ROCK ISLAND-STEPHENSON.
WINTER STORM WATCH FROM TUESDAY MORNING THROUGH WEDNESDAY
AFTERNOON FOR BUREAU-HANCOCK-HENDERSON-HENRY IL-MCDONOUGH-
MERCER-PUTNAM-WARREN-WHITESIDE.
MO...BLIZZARD WATCH FROM TUESDAY MORNING THROUGH WEDNESDAY AFTERNOON
FOR CLARK-SCOTLAND.
&&
$$
08/NICHOLS/08
