FXUS63 KLOT 210702
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
202 AM CDT SUN MAR 21 2010

.DISCUSSION...
258 PM CDT

BAND OF MIXED PRECIPITATION CONTINUES ALONG STRONG BAROCLINIC
ZONE WITH HEAVIEST NOW ALONG I-55 CORRIDOR. THERE HAS BEEN A
GRADUAL SHIFT SOUTHEASTWARD TODAY...WITH SNOW DIMINISHING TOWARD
WI BORDER. RAIN-SNOW LINE APPEARS TO BE ALONG I-55. LATEST
SURFACE OBS SHOW PRECIP HAS CHANGED TO SNOW AT PIA BUT RAIN AT
PNT. FOR OVERNIGHT WILL GO WITH HIGHEST POPS S AND SW PART OF
FORECAST AREA WITH LOWER POPS NEAR WI BORDER. EXPECT ALL SNOW
NORTH BUT A MIX OF RAIN AND SNOW AND MAYBE SOME SLEET ALONG I-55
CORRIDOR. FAR SE PART OF AREA SHOULD JUST SEE RAIN. SOME AREAS...S
OF CHICAGO TO OTTAWA...COULD SEE UP TO AN INCH THE REST OF THIS
AFTERNOON AND THIS EVENING BUT MOSTLY ON GRASSY AREAS WITH LITTLE
OR NO TRAVEL IMPACTS. OVERALL TREND IN MODELS IS FOR THE
BAROCLINIC ZONE TO GRADUALLY WEAKEN OVERNIGHT AS UPPER LOW SPINS
UP IN SOUTHERN PLAINS/LOWER MS VALLEY. LOW LEVEL TEMPS GRADUALLY
WARM ABOVE FREEZING BY SUN MORNING. AT THE SAME TIME RH IN THE
DENDRITIC GROWTH ZONE OF -10C TO -15C DECREASES. THUS ONLY EXPECT
A CHANCE OF LIGHT RAIN/SNOW IN THE EARLY MORNING...THEN JUST A
CHANCE OF LIGHT RAIN THE REST OF THE DAY SUNDAY.

AS UPPER LOW LIFTS NE INTO THE APPALACHIANS MONDAY AND TUESDAY THE
BULK OF THE PRECIP WILL STAY SE OF FORECAST AREA. EXPECT CLEARING
N TO S ACROSS FORECAST AREA. TEMPS SHOULD RECOVER SOMEWHAT SUNDAY
WITHOUT PRECIP...AND EVEN MORE MONDAY AND TUESDAY WITH INCREASING
ISOLATION. EXCEPTION WILL BE ALONG THE LAKE WITH WEAK
NORTHEASTERLY WINDS. WINDS MAY SHIFT SW BY TUESDAY AFTERNOON IN
ADVANCE OF APPROACHING COLD FRONT. GFS NOW MORE IN LINE WITH ECMWF
IN BRINGING WEAK COLD FRONT THROUGH TUESDAY NIGHT/WEDNESDAY
MORNING. EXPECT TO SEE SOME CLOUDINESS BUT ONLY SLIGHT CHANCE OF A
SPRINKLE. NOT A LOT OF COOLING BEHIND THIS FRONT BUT LAKE
INFLUENCE WILL BE ENHANCED WITH SYNOPTIC NE WINDS.

YET ANOTHER LOW TO PASS TO OUR SOUTH FOR THE END OF THE WEEK. AT
THIS TIME WILL INCLUDE A CHANCE OF RAIN SOUTH...OTHERWISE DRY.

ALLSOPP

&&

.AVIATION...
200 AM CDT

0600 UTC TAFS...MVFR AND AREAS OF IFR IN -SN/-RASN/-DZ TO PERSIST
TIL PRE-DAWN ACROSS CHI AREA TERMINALS THEN IMPROVE TO VFR AROUND
SUNRISE. KRFD TO REMAIN VFR. NE SFC WINDS GENERALLY 10-12 KT
TODAY WITH SOME OCNL 15-18 KT THIS MORNING. WINDS DROP BLO 10 KT
FOR THIS EVE.


SHORT WAVE THAT HAS BEEN LIFTING NORTHWARD OVER NORTHEASTERN MO
HAS SPREAD A BIT HEAVIER LIGHT SNOW BACK INTO NORTH CENTRAL AND NE
IL AS OF 05Z WITH MVFR VISIBILITIES REPORTED UNDER STRONGER RADAR
ECHOES. THIS SHORT WAVE IS STARTING TO SHEAR NORTHWESTWARD AS IT
HAS MOVED THROUGH THE NE QUAD OF THE UPPER LOW AND IS NOW TURNING
TOWARD TO NW.

UPPER TROUGH MOVING E FROM THE UPPER MIDWEST OVER THE UPPER GREAT
LAKES TO SUPPRESS NORTHWARD EXTEND OF ANY REMAINING PRECIP TO THE
S OF THE LOCAL TERMINALS BY 12Z...SAVE POSSIBLY KGYY DUE TO ITS
SOUTHEASTERN-MOST LOCATION.

CONTINUED ADVECTION OF LOW DEW POINT AIR ACROSS THE LOCAL AREA
HAS RESULTED IN VFR CEILINGS PREVAILING EXCEPT UNDER SOUTHERN
PORTION OF PRECIP BAND WHERE DRYING HAMPERED BY CONTINUED
MOISTURE ADDITION FROM ABOVE VIA PRECIP...AND A BIT OF MOISTURE
BEING BROUGHT INLAND OFF OF FAR SOUTHERN LAKE MI.

WITH CENTER OF UPPER LOW MOVING E ACROSS NORTHERN MS AND AL
TONIGHT ONLY MID AND HIGH CLOUDS OF EDGE OF ASSOCIATED CLOUD
SHIELD TO REACH THE LOCAL TERMINALS.

TRS

&&

.MARINE...

224 PM...A COLD FRONT/TROUGH OF LOW PRESSURE EXTENDS FROM NEW
ENGLAND SOUTHWEST TO THE WESTERN GULF OF MEXICO....WITH A RIDGE OF
HIGH PRESSURE EXTENDING ACROSS THE NORTHERN LAKES. NEW LOW
PRESSURE WILL DEVELOP ALONG THIS COLD FRONT OVER ARKANSAS TONIGHT
THEN SLOWLY MOVE NORTHEAST ACROSS THE OHIO VALLEY WHILE DEEPENING.
THE RIDGE ACROSS THE UPPER LAKES WILL SAG SOUTH AS ANOTHER AREA OF
LOW PRESSURE MOVES ACROSS NORTHERN ONTARIO AND JAMES BAY SUNDAY.
AS A RESULT OF THIS COMPLEX PATTERN...LIGHT AND VRB WINDS OVER THE
NORTHERN PARTS OF LAKE MICHIGAN WILL TURN SOUTHWESTERLY TONIGHT.
ANY AREA OF LIGHT WINDS WILL PERSIST ACROSS CENTRAL LAKE MICHIGAN
SUNDAY AND SUNDAY EVENING UNTIL THE RIDGE WEAKENS. FURTHER
SOUTH... IN RESPONSE TO A TIGHTENING GRADIENT FROM THE LOW MOVING
ACROSS THE OHIO VALLEY...EXPECT A PERSISTENT NORTHEAST FLOW OVER
SOUTHERN LAKE MICHIGAN THROUGH MONDAY NIGHT...WHEN A RIDGE OF HIGH
PRESSURE MOVES ACROSS THE ENTIRE LAKE. THIS NORTHEAST FLOW COULD
BE A BIT STRONG A TIMES...15-20KTS SEEMS REASONABLE WITH HIGHER
GUSTS POSSIBLE. WITH A SHORT BREAK IN WINDS EXPECTED SUNDAY
MORNING... WILL EXTEND THE SMALL CRAFT ADVISORY THRU 12Z SUNDAY
MAINLY FOR WAVE ACTION. CMS

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 7 AM SUNDAY.

&&

$$