FXUS63 KLOT 030411
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1011 PM CST WED DEC 2 2009
.DISCUSSION...
308 PM...FORECAST CHALLENGES TONIGHT ARE MANY...INCLUDING QPF
AMOUNTS...CHANGE OVER/MIX TO SNOW...TIMING OF CHANGE OVER AS WELL
AS TEMPS. THEN MUCH COLDER TEMPS THRU THIS WEEKEND.
LOW PRESSURE OVER THE OHIO VALLEY WILL CONTINUE TO LIFT NORTHEAST
TO NEAR LAKE ONTARIO BY THURSDAY MORNING. AREA OF LIGHT/MODERATE
RAIN LIFTING NORTH/NORTHEAST ACROSS THE SOUTHEAST PART OF THE CWA
THIS AFTERNOON. AS THE LOW CONTINUES NORTHEAST...EXPECT THIS AREA
OF RAIN TO BEGIN TO PIVOT WITH THE BACK EDGE OF THE RAIN/PRECIP
LIKELY OCCURRING THRU THE CENTRAL PORTION OF THE CWA. THUS WILL
CONTINUE WITH JUST CHANCE POPS ACROSS THE NORTHWEST TO CAT POPS
ACROSS THE SOUTHEAST. WHILE MOST OBSERVATIONS HAVE ONLY REPORTED
LIQUID PRECIP TO OUR SOUTH THIS AFTERNOON...THERE HAVE BEEN A FEW
REPORTS OF SNOW MIXING WITH THE RAIN. THERMAL PROFILES WOULD
SUGGEST PRECIP TO START AS RAIN ACROSS MOST OF THE CWA BUT WITH
COOLER AIR SLOWLY FILTERING IN FROM THE NORTH AND ALREADY A FEW
REPORTS OF MIXED SNOW...HAVE OPTED TO START PRECIP AS A MIX OF
RAIN/SNOW GENERALLY NORTH OF A PNT/GYY LINE. IF PRECIP DOES START
AS RAIN...PROBABLY WON/T BE TOO LONG BEFORE IT BEGINS TO MIX.
FURTHER SOUTHEAST...EXPECT MAINLY LIGHT RAIN.
AMOUNTS HOWEVER...APPEAR TO BE RATHER LIGHT. THOUGH MODELS...
ESPECIALLY THE NAM SUGGESTS THE POTENTIAL FOR SOME LAKE
ENHANCEMENT DURING THE MID/LATE EVENING HRS OVER FAR NORTHEAST IL.
AND BY THE TIME THE COLUMN IS COOL ENOUGH TO SUPPORT ALL SNOW...
THE BULK OF THE PRECIP HAS SHIFTED TO THE EAST...THOUGH DO EXPECT
SOME LIGHT SNOW OVERNIGHT. IN ADDITION...THE WARM GROUND WILL
LIKELY BE A FACTOR...THUS ANY ACCUMULATIONS WILL LIKELY BE MINOR
AND ON GRASSY AND ELEVATED SURFACES. IN ADDITION...WHILE PRECIP
MAY FALL AS SNOW...OR A MIX...TEMPS TO OUR NORTH ARE NOT THAT COLD.
THUS DESPITE NORTHERLY FLOW...AIR ADVECTING INTO THE AREA IS NOT
SIGNIFICANTLY COOLER SO HAVE BUMPED TEMPS UP THRU THE EVENING AS
TEMPS SLOWLY SLIDE THRU THE UPPER 30S INTO THE MID 30S.
PROBABLY THE MOST SIGNIFICANT CHANGE WITH THIS SYSTEM IS THE MUCH
COLDER TEMPERATURES EXPECTED ACROSS THE AREA. WHILE NOT UNUSUAL
FOR EARLY DECEMBER...GIVEN THE MID 50S TUESDAY...MID 40S TODAY...
THE EXPECTED HIGHS IN THE MID 30S THURSDAY AND PERHAPS BARELY 30
ON FRIDAY WILL FEEL COLDER THAN THEY REALLY ARE. HAVE STAYED IN
LINE WITH GOING FORECAST HIGHS BOTH THURSDAY AND FRIDAY...WHICH
ARE SEVERAL DEGREES COLDER THAN GUIDANCE. WITH THE AMOUNT OF
SUNLIGHT APPROACHING ITS YEARLY MINIMUM AND COLD AIR ADVECTION
BOTH DAYS ALONG WITH CLOUD COVER...EXPECT LITTLE IF ANY RECOVERY
IN HIGH TEMPS. LOWS WELL INTO THE LOWER 20S FRIDAY MORNING WITH
TEENS EXPECTED SATURDAY MORNING.
SOME MODERATION IN TEMPS OVER THE WEEKEND ESPECIALLY SUNDAY AS THE
FLOW TURNS SOUTHERLY WHICH SHOULD HELP TEMPS WARM BACK INTO THE
UPPER 30S. BUT A WEAK LOW LIFTS NORTH ACROSS THE MIDWEST/WESTERN
LAKES SUNDAY NIGHT/EARLY MONDAY AND WHILE IT WILL HAVE LIMITED
MOISTURE...THIS MAY BE ABLE TO SQUEEZE OUT ENOUGH QPF FOR A
DUSTING OF SNOW...TEMPS WILL CERTAINLY BE COLD ENOUGH FOR ALL
SNOW. NEXT SYSTEM MOVES FROM THE PLAINS TO THE OHIO VALLEY TUESDAY
NIGHT INTO WEDNESDAY. TOO EARLY FOR ANY DETAILS...BUT THIS WILL
NEED TO BE MONITORED FOR THE POTENTIAL FOR AN ACCUMULATING SNOW.
CMS
&&
.AVIATION...
1011 PM CST
0600 UTC TAFS...THE LOW LEVELS OF THE ATMOSPHERE HAVE FINALLY
MOISTENED UP ENOUGH TO PRODUCE SOME PRECIPITATION ACROSS THE TAF
REGION WITH A BAND OF LIGHT RAIN/DRIZZLE ACROSS FAR NORTHEAST
IL/NORTHWEST IN WITH A SECONDARY BAND OF LIGHT SNOW EXTENDING FROM
SOUTH CENTRAL WISCONSIN INTO NORTH CENTRAL ILLINOIS. VIS HAS
GENERALLY BEEN MVFR BETWEEN 4 TO 6SM...BUT FURTHER SOUTH PEORIA
BRIEFLY WENT TO IFR WITH AN OB OF 2 1/2SM FOR LESS THAN A HALF
HOUR. FORECAST GUIDANCE IS SUGGESTING THAT THIS SNOW BAND IS GOING
TO FALL APART BY THE TIME IT REACHES ORD/MDW...SO FOR THE TIME
BEING...HAVE JUST GONE WITH A BRIEF TWO HOUR WINDOW FOR 6SM -SN
FOR EARLY THURSDAY MORNING.
AFTER THIS BAND OF SNOW MOVES THROUGH...LOOKS LIKE A SCATTERING OF
VFR TO MVFR CIGS ACROSS THE REGION...BUT HAVE REMAINED A BIT ON
THE PESSIMISTIC SIDE WITH HIGH END MVFR CIGS PERSISTING THROUGH
THE REST OF THE TAF PERIOD. SCATTERED SNOW SHOWERS STILL APPEAR
LIKELY THURSDAY AFTERNOON INTO THE EVENING HOURS.
EXPECT MAINLY MVFR CONDITIONS WITH SOME BRIEF BREAKS TO VFR
POSSIBLE OVERNIGHT BEING THE SNOW BELT.
HALBACH
&&
.MARINE UPDATE...
WIND GUSTS ALONG THE SOUTHERN RIM OF LAKE MICHIGAN HAVE HAD A
NUMBER OF REPORTS OF GALE FORCE GUSTS...THEREFORE HAVE UPPED THE
SMALL CRAFT ADV TO A GALE WARNING FOR THE SOUTHERN HALF OF THE
LAKE INCLUDING THE NEARSHORE ZONES. WINDS SHOULD COME DOWN
OVERNIGHT AS THE LOW PRESSURE SYSTEM MOVES OFF TOWARD THE EAST
COAST.
HALBACH
&&
.MARINE...
153 PM CST
NORTHWEST WINDS WILL BE MAINTAINED ACROSS THE LAKE TODAY AS AN
AREA OF LOW PRESSURE DEPARTS TO THE NORTHEAST AND A SECONDARY AREA OF
LOW PRESSURE TRACKS NORTHEAST INTO THE LOWER MIDWEST. WITH THIS
AREA OF LOW PRESSURE MOVING INTO THE REGION...PRESSURE GRADIENT OVER
THE LAKE WILL INCREASE THIS AFTERNOON INTO THE EVENING. THIS ALONG
WITH A GOOD AMOUNT OF COLD AIR ADVECTION...WILL HELP INCREASE
NORTH GUSTS ACROSS THE LAKE TO JUST ABOVE 30 KT. WIND GUSTS WILL
STAY BELOW GALES AS MAIN LOW WILL STAY SOUTH OF THE LAKE...BUT A
BRIEF GUST TO GALE FORCE WOULD NOT BE OUT OF THE QUESTION. AREA OF
LOW PRESSURE WILL CONTINUE OFF TO THE NORTHEAST ON THURSDAY WITH
WINDS BACKING TO MORE OF A NORTHWESTERLY COMPONENT...AND WITH
WINDS ALSO DECREASING THROUGHOUT THE DAY. WEST WINDS WILL BE
MAINTAINED THROUGH FRIDAY AS THE NEXT SYSTEM DROPS SOUTH OUT OF
CANADA INTO THE LOWER MIDWEST.
RODRIGUEZ
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ080-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-LMZ742-
LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ872-LMZ874-LMZ876-
LMZ878 UNTIL 6 AM THURSDAY.
SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...6 AM THURSDAY TO 3
PM THURSDAY.
SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...6 AM THURSDAY TO 6
PM THURSDAY.
&&
$$
