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000
FXUS63 KLOT 090927 CCA
AFDLOT
AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
424 AM CDT SAT MAY 9 2009
.DISCUSSION...
350 AM CDT
THE NEXT SEVERAL DAYS WILL HAVE DRY WEATHER.
TODAY THROUGH SUNDAY...THE 500 MB TROUGH WILL BE OVER MICHIGAN BY
THIS AFTERNOON. THE SCATTERED LINGERING SHOWERS WILL MOVE EAST OF
NORTHERN ILLINOIS AND NORTHWEST INDIANA BY THIS AFTERNOON. THIS
IS BASED ON MOVEMENT FROM THE SATELLITE IR IMAGERY LOOPS AND USING
THE LOCAL WRF MODEL AND GFS MODEL. A SURFACE LOW HAS
INTENSIFIED...WITH THE PRESSURE FALLING 4.1 MB FROM 01 UTC TO 08
UTC. THIS IS 1.0 MB MORE DECREASE IN PRESSURE THAN THE LOCAL WRF
OR GFS MODELS SHOW. THE WIND WILL BE FROM THE NORTHWEST TODAY WITH
SOME GUST TO 26 MPH. THIS IS BECAUSE THE LOW DECREASES IN PRESSURE
AND RESULTS IN AN INCREASE IN THE PRESSURE GRADIENT WEST OF THE
LOW. WE WILL USE THE MOS GUIDANCE FROM THE NAM MODELS FOR
TEMPERATURE FORECAST. WE NOTICE A 2 DEGREE MEAN ABSOLUTE ERROR OR
THE SIZE OF THE ERRORS...FOR THE LAST TEN DAYS IN THE LOCAL WRF
AND NAM MODEL TEMPERATURE FORECASTS. THE NAM HAD A LOWER BIAS AND
THIS BIAS WAS ON THE COOL SIDE OF THE ACTUAL HIGH TEMPERATURES. WE
WILL USE THIS BIAS TO ADJUST THE TEMPERATURE FORECAST FOR TODAY
THROUGH MONDAY. THE LOCAL WRF PERFORMED BETTER WITH THE HOURLY
DEWPOINT FORECASTS. DRY AND COOLER WEATHER WILL OCCUR ON
SUNDAY...AS A LARGE HIGH MOVES INTO NORTHERN ILLINOIS.
MONDAY THROUGH TUESDAY...THERE WILL BE ZONAL FLOW OVER THE GREAT
LAKES MONDAY NIGHT AT 500 MB. A 500 MB RIDGE BUILDS OVER THE
GREAT LAKES DURING TUESDAY. THERE WILL BE A FRONT AND TWO LOWS IN
THE GREAT PLAINS BY TUESDAY NIGHT. WE USED THE GFS MODEL BECAUSE
OF ITS TIMING WITH THE SUNDAYS SURFACE LOW. THE WEATHER WILL
BECOME WARMER ON TUESDAY. A 500 MB TROUGH AND FRONT WILL MOVE
TOWARDS ILLINOIS WEDNESDAY. WE EXPECT THUNDERSTORMS ON WEDNESDAY
AND SHOWERS ON THURSDAY. BY THURSDAY EVENING ANOTHER HIGH WILL
MOVE INTO ILLINOIS. WE EXPECT DRY WEATHER FOR FRIDAY.
&&
.AVIATION...
155 AM CDT
0600 UTC TAFS...AT 05Z UPPER LOW MOVING FROM SOUTHEAST MN INTO WEST
CENTRAL WI WITH DEEPENING SURFACE LOW OVER FAR SOUTHWEST WI WITH ALL
OF RAIN AND THUNDERSTORMS IN THE WARM AIR ADVECTION/ISENTROPIC LIFT
ZONE LIFTING NORTHEASTWARD ACROSS SOUTHEASTERN WI AND SOUTHERN
LAKE MI WHILE A COLD FRONT MOVES QUICKLY ACROSS FAR SOUTHWEST WI
AND EASTERN IA. MVFR STRATOCU ADVANCING INTO NORTHERN IL WITH THE
LOW LEVEL CAA AND WILL CONTINUE TO SPREAD ACROSS THE LOCAL
TERMINALS EARLY THIS MORNING.
DEEPENING SURFACE LOW RESULTING IN INCREASING SOUTHWEST WINDS AHEAD
OF THE COLD FRONT AND MODERATELY STRONG WEST TO WEST-NORTHWEST WINDS
GUSTING TO AROUND 30 KNOTS BEHIND THE COLD FRONT. STRONGEST SURFACE
PRESSURE RISES AND LOW LEVEL COLD ADVECTION PROGGED ACROSS SOUTHERN
WI...NORTHERN IL AND SOUTHERN LAKE MI INTO SOUTHWEST LOWER MI AND
NORTHWEST IN THIS MORNING AND EXPECT THE GUSTY WEST TO WEST-NORTHWEST
TO SPREAD ACROSS THESE AREAS THOUGH TO DROP OFF PRETTY QUICKLY DURING
THE AFTERNOON AS THE SURFACE LOW MOVES RAPIDLY TO THE CHAMPLAIN
VALLEY/UPPER ST. LAWRENCE VALLEY BY 00Z.
RAIN WRAPPED BACK AROUND THE NORTH AND NORTHWEST SIDE OF THE
MID/UPPER LOW TO OVER SOUTHEAST MN AND NORTHEAST IA TO REMAIN
NORTH OF THE STATE LINE AS THE SYSTEM LIFTS EAST-NORTHEAST ACROSS
THE WESTERN GREAT LAKES TODAY. WITH LOW LEVEL DRYING UNDER WAY
ACROSS THE LOCAL AREA TODAY THE MVFR STRATOCU CEILINGS TO LIFT TO
VFR AS DEW POINT DEPRESSIONS INCREASE AS A RESULT OF ADVECTION OF
MID AND LOWER 40S SURFACE DEW POINTS ACROSS INTO THE AREA AS WELL
AS DIURNAL TEMPERATURE RISE.
TRS
&&
.MARINE...
424 AM CDT
DEEPENING SURFACE LOW MOVING ACROSS FAR SOUTHERN LAKE MI RESULTING
IN INCREASING SOUTHWEST WINDS FAR SOUTH AND INCREASING NORTH TO
NORTHEAST WINDS CENTRAL AND NORTH PORTIONS EARLY THIS MORNING. AS
THE LOW MOVES QUICKLY EASTWARD TO THE EASTERN GREAT LAKES TODAY
WINDS WILL DROP OFF PRETTY QUICKLY DURING THE AFTERNOON AS THE
PRESSURE GRADIENT ACROSS THE LAKE DROPS OFF SIGNIFICANTLY BY MID
TO LATE AFTERNOON WITH THE LOW WELL REMOVED TO THE EAST AND THE
CENTER OF A HIGH PRESSURE RIDGE WELL WEST OVER THE CANADIAN PRAIRIE
AND THE NORTHERN AND CENTRAL PLAINS. THIS RIDGE TO GRADUALLY DRIFT
EAST AND SOUTHEASTWARD OVER THE MS VALLEY...UPPER GREAT LAKES AND
OH VALLEY BY SUNDAY NIGHT AND MONDAY RESULTING IN LIGHT WIN REGIME
OVER THE UPPER LAKES UNTIL LATE TUESDAY-TUESDAY NIGHT WHEN THE
HIGH MOVES OF TO THE EAST AND A TROUGH WILL BE MOVING EAST ACROSS
CENTRAL CANADA AND THE PLAINS WITH INCREASING SOUTHEAST TO SOUTH
WINDS TUESDAY NIGHT AND WEDNESDAY.
TRS
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ080-LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-
LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ868-
LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 UNTIL 4 PM SATURDAY.
&&
$$
