FXUS63 KLOT 041722
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1122 AM CST FRI DEC 4 2009
.DISCUSSION...
314 AM CST
.TODAY AND TONIGHT...THE SNOW SHOWERS THAT ARE OCCURRING THIS EARLY
MORNING WILL REMAIN NORTH OF INTERSTATE 88. THIS IS A BAND OF SNOW
RESULTING FROM WEAK SURFACE TROUGH MOVING THROUGH NORTHEASTERN
ILLINOIS. THE BLUE RIVER WISCONSIN PROFILER SHOWS THE WIND
BACKING BETWEEN 04 UTC AND 05 UTC. THE UPPER AIR TROUGH IS PASSING
THROUGH. THE POSITIVE VORTICITY ADVECTION AT 500 MB ON THE MODELS
SHOW THIS. BY 12 UTC WE EXPECT MOST OF THE SHOWERS TO END. WE WILL
FORECAST SCATTERED VERY LIGHT SNOW SHOWERS FOR THE REST OF THE
DAY. THE 850 MB ANALYSIS SHOWS VERY COLD AIR MOVING INTO OUR
FORECAST AREA TODAY. WE LOWERED THE HIGH TEMPERATURE FORECAST A
LITTLE TODAY. WE WILL FORECAST A LOWER TEMPERATURE THAN MODEL
OUTPUT STATISTICS FOR THE LOW TEMPERATURE TONIGHT.
SATURDAY THROUGH MONDAY...A LARGE HIGH WILL MOVE FROM THE ROCKY
MOUNTAINS AND GREAT PLAINS TO VIRGINIA BY MONDAY. WE EXPECT DRY
WEATHER SATURDAY AND SUNDAY. A COLD FRONT IS FORECAST TO MOVE
THROUGH SUNDAY NIGHT. WE WILL ADD A CHANCE OF SNOW SUNDAY NIGHT
AND MONDAY. WE USED THE ECMWF MODEL AND WE NOTE THAT THE POLAR JET
STREAM OVER ILLINOIS WILL MOVE EAST TO NEW ENGLAND BY SATURDAY
MORNING. THE HIGH TEMPERATURES WILL INCREASE TO THE MIDDLE 30S BY
SUNDAY AND WILL FALL TO THE LOWER 30S BY MONDAY.
OUTLOOK...A STRONG LOW IS FORECAST TO MOVE FROM OKLAHOMA TO
MICHIGAN TUESDAY NIGHT. THE LOW IS FORECAST OT BE IN ONTARIO BY
WEDNESDAY NIGHT. WE SEE THIS ON THE ECMWF AND THE GFS MODELS. WE
WILL KEEP THE CHANCE OF SNOW FOR TUESDAY THROUGH THURSDAY AT THIS
TIME.
&&
.AVIATION...
1800 UTC TAFS...MORE SOLID STRATOCU DECK IS MOVING EAST...HOWEVER
MORE CELLULAR DIURNAL STRATOCU SHOULD FILL IN OVER N IL THIS
AFTERNOON. GENERALLY EXPECT CHARACTER OF THE SKY TO BE SCT
TODAY...THOUGH THERE WILL PROBABLY BE SOME PERIODIC BKN MVFR CIGS
FROM TIME TO TIME THIS AFTERNOON. STILL POSSIBLE THAT THERE COULD
BE A COUPLE SNOW FLAKES LEAK OUT OF THE STRATOCUMULUS THIS
AFTERNOON BUT NO IMPACT ON AVIATION OPS ANTICIPATED. DIURNAL
STRATOCU SHOULD FADE AT SUNSET WITH CLEARING SKIES SAVE FOR SOME
CIRRUS STARTING TO SPILL INTO THE AREA OVERNIGHT INTO SATURDAY
MORNING. WINDS SHOULD SUBSIDE QUICKLY THIS EVENING AND BACK TO
MORE SSW ALBEIT LIGHTLY OVERNIGHT.
IZZI
&&
.MARINE...
200 AM CST
LOW PRESSURE MOVING NORTHWARD FROM SOUTHERN QUEBEC WITH A STRONG
RIDGE OF HIGH PRESSURE CONTINUING TO BUILD EAST OVER THE OH VALLEY
WILL MAINTAIN MODERATE W WINDS ACROSS LAKE MI TODAY...GRADUALLY
WEAKENING AND BACKING TO SW OVERNIGHT AND SAT AS THE LOW IN QUEBEC
CONTINUES TO MOVE NNW AND THE W-E RIDGE BECOMES ORIENTED SW-NE
FROM E TX ACROSS THE UPPER OH VALLEY TH THE ST. LAWRENCE VALLEY.
NEXT COLD FRONT/TROF SLIPS ACROSS NORTHERN LAKE MI LATE SAT NIGHT AND
EARLY SUN MORNING. LOW PRESSURE TO MOVE NE ALONG FRONT ACROSS THE
MID MS VALLEY SUN NIGHT REACHING LAKE MI BY MON MORNING.
WILL ALLOW SMALL CRAFT ADVISORY TO RIDE TIL 15Z MAINLY FOR
RESIDUAL WAVES AS WIND SPEEDS HAVE BEEN TRENDING DOWN AS NIGHT
PROGRESSES.
TRS
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...INDIANA NEARSHORE WATERS UNTIL 4 PM FRIDAY.
&&
$$
