FXUS63 KDVN 062101 CCA
AFDDVN
AREA FORECAST DISCUSSION...CORRECTED LONG TERM
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
257 PM CST SUN DEC 6 2009
.SYNOPSIS...
A BROAD H5 TROF WAS IN PLACE OVER THE WESTERN THIRD OF THE U.S. THIS
MORNING. S/W ENERGY CONTINUES TO DIG THROUGH THE PAC NW INTO THE
BASE OF THE TROF AS ANOTHER S/W EJECTS OUT OF THE TROF INTO THE SRN
PLAINS. A COLD FRONT WAS LOCATED FROM SRN WI AND ERN IA SW INTO A
DEVELOPING SFC LOW OVER SWRN OK. SNOW ON THE COLD SIDE OF THE
BOUNDARY HAS BEEN DEVELOPING OVER THE SRN AND CENTRAL PLAINS AND
SPREADING EAST TODAY. RADAR RETURNS WERE AS FAR EAST AS NE MO INTO
EAST CENTRAL IA....BUT LOOKING AT SURFACE REPORTS YOU HAD TO GO BACK
TO NEAR THE MO RIVER TO FIND ANY -SN REACHING THE GROUND.
&&
.SHORT TERM...TONIGHT THROUGH MONDAY...
MODELS CONTINUE TO SHOW SURFACE LOW MOVING NE ALONG THE FRONT
TONIGHT AND MONDAY MORNING...AHEAD OF THE EJECTING S/W TROF. EXPECT
ONGOING SNOW OVER SWRN IA ERN NE AND NERN KS TO SPREAD EAST
REACHING THE NWRN CWA EARLY THIS EVENING.
BASED ON THE PROGGED TRACK OF THE SURFACE LOW ACROSS NE MO THROUGH
WCNTRAL IL AND THE H8 LOW TRACKING FROM NR KOMA TO KFEP HAVE BACKED
OFF ON SNOW AMOUNTS SOUTH OF I80 TO GENERALLY LESS THAN AN INCH.
LOOKING AT MID LEVEL FGEN TONIGHT AND EARLY MONDAY...THE DEEPEST
FORCING IS EXPECTED OVER THE NRN QUARTER OF THE CWFA. MID LEVEL
LAPSE RATES AROUND 5.5C/KM SUGGEST ONLY MODEST FORCING SO KEPT
SNOWFALL AMOUNTS IN THE 2-3 INCH RANGE ALONG THE HWY 20 CORRIDOR.
THESE AMOUNTS ARE JUST UNDER ADVISORY CRITERIA AND SINCE PART OF THE
AREA RECEIVED MEASURABLE SNOW LATE LAST WEEK...OPTED NOT TO GO WITH
AND ADVISORY AT THIS TIME. FURTHER SOUTH THROUGH I80 AMOUNTS
EXPECTED IN THE 1-2 INCH RANGE WITH AN INCH OR LESS OVER THE REST OF
THE CWFA. THE SYSTEM WILL PULL AWAY FROM THE CWFA MONDAY MORNING
AND ENDED MEASURABLE SNOW THREAT AT 18Z. LOW LEVEL RH REMAINS HIGH
OVER THE NRN CWFA MONDAY AFTERNOON. FCST SOUNDINGS SHOW DECENT
LOW LEVEL LAPSE RATES DURING THE AFTERNOON...SO HELD ON TO SOME
FLURRY WORDING ACROSS THE NRN HALF.
TEMPS ARE NOT EXPECTED TO FALL MUCH TONIGHT AS THE SURFACE LOW MOVES
TOWARD THE CWFA SO STAYED WITH THE WARMER GUIDANCE ALLOWING FOR
ABOUT A 10 DEGREE DROP. FOR MONDAY EXPECT MINIMAL TEMP RISE OF
ABOUT 5 DEGREES OR SO WITH CLOUDS/FRESH SNOW ESPECIALLY N/AND WEAK
CAA. ...DLF..
.LONG TERM...MONDAY NIGHT THROUGH NEXT SUNDAY...
...POWERFUL WINTER STORM TO AFFECT THE AREA TUESDAY THROUGH
WEDNESDAY...LONG RANGE MODELS ARE STILL ON TRACK WITH DEVELOPING A
MAJOR WINTER STORM ACROSS THE MIDWEST FROM TUESDAY AFTERNOON THROUGH
WEDNESDAY EVENING. THE ECMWF/GFS ARE IN CLOSE AGREEMENT WITH MOVING
A RAPIDLY INTENSIFY SURFACE LOW PRESSURE SYSTEM FROM THE
OKLAHOMA/KANSAS BORDER ON TUESDAY MORNING...ACROSS CENTRAL MISSOURI
TO JUST SOUTH OF CHICAGO BY 12Z WEDNESDAY. THE ECMWF IS THE STRONGER
OF THE TWO MODELS AND PRODUCES A 980 MB SURFACE LOW AT THIS TIME.
WITH THIS STORM TRACK AND STRENGTH POSSIBLE...I HAVE ISSUED A WINTER
STORM WATCH FOR THE ENTIRE FORECAST AREA STARTING AT 12Z TUESDAY
MORNING. A MIXTURE OF RAIN...SLEET...AND SNOW...IS POSSIBLE TUESDAY
AFTERNOON SOUTH OF HIGHWAY 34 AS WARMER AIR IS PULLED NORTHWARD BY
THE SYSTEM.
AT A MINIMUM...THE UPPER MISSISSIPPI VALLEY WILL EXPERIENCE A
SIGNIFICANT WINTER STORM TUESDAY AND WEDNESDAY WHICH WILL HAVE A
MAJOR IMPACT ON TRAVEL. THE WORST OF THE STORM...WHICH COULD PRODUCE
NEAR BLIZZARD CONDITIONS...SHOULD OCCUR FROM LATE TUESDAY EVENING
THROUGH WEDNESDAY AFTERNOON. SUSTAINED NORTHWEST WINDS OF 25 TO 35
MPH...WITH GUSTS NEAR 50 MPH...WILL PRODUCE AREAS OF WHITE OUT
CONDITIONS...ESPECIALLY IN OPEN RURAL AREAS.
SURFACE TEMPERATURES WILL ALSO TO DROP INTO THE SINGLE DIGITS
WEDNESDAY NIGHT. THESE COLD TEMPERATURES COMBINED WITH NORTHWEST
WINDS OF 15 TO 20 MPH...WILL PRODUCE WIND CHILL TEMPERATURES IN THE
SINGLE DIGITS BELOW ZERO ACROSS THE SOUTHERN TWO THIRDS OF THE
FORECAST AREA AND FROM 10 TO 15 DEGREES BELOW ZERO NORTH OF HIGHWAY
30. ...KUHL...
&&
.AVIATION...
CONDITIONS TO GRADUALLY DETERIORATE TO IFR AT ALL SITES TONIGHT
WITH SN DEVELOPING OVER THE AREA. AT KCID/KDBQ IFR CONDITIONS
EXPECTED TO DEVELOP LATE THIS EVENING AND AFTER MIDNIGHT A
KMLI/KBRL. AT THIS TIME KEPT CIGS/VSBYS ON THE LOW END OF THE IFR
CATEGORY...BUT A BRIEF PERIOD OF +SN AT KCID/KDBQ LATE TONIGHT
COULD DROP CONDITIONS TO LIFR FOR A SHORT TIME. AT KMLI/BRL THE
ISSUE WILL BE A COMBINATION OF -SN/BR OR FG LOWERING CIGS/VSBYS TO
LIFR WITH THE SURFACE LOW MOVING CLOSE TO THESE LOCATIONS LATE
TONIGHT AND EARLY MONDAY MORNING. ALSO...WHILE NOT INCLUDED IN THE
TAF...THERE IS LOW POTENTIAL FOR A MIX OF -RA/SN OR -FZRA/SN AT
KBRL LATE TONIGHT. THIS WILL DEPEND ON THE TRACK OF THE SURFACE
LOW. ...DLF...
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...WINTER STORM 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...WINTER STORM WATCH FROM TUESDAY MORNING THROUGH WEDNESDAY
AFTERNOON FOR BUREAU-CARROLL-HANCOCK-HENDERSON-HENRY IL-JO
DAVIESS-MCDONOUGH-MERCER-PUTNAM-ROCK ISLAND-STEPHENSON-
WARREN-WHITESIDE.
MO...WINTER STORM WATCH FROM TUESDAY MORNING THROUGH WEDNESDAY
AFTERNOON FOR CLARK-SCOTLAND.
&&
$$
DLF/KUHL
