FXUS63 KLOT 051042
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
442 AM CST SAT DEC 5 2009
.DISCUSSION...
247 AM CST
FORECAST CHALLENGES THIS MORNING REVOLVE AROUND WEAK STORM SYSTEM
SLATED TO ARRIVE SUNDAY NIGHT...THEN THE MUCH STRONGER STORM SYSTEM
TO AFFECT THE REGION THE MIDDLE OF NEXT WEEK.
IN THE SHORT TERM...THE STORM SYSTEM THAT HAS PLAGUED OUR REGION FOR
DAYS WILL CONTINUE TO LOOSEN ITS GRIPS ON THE REGION TODAY. 11-3.9
MICRON GOES IMAGERY EARLY THIS MORNING SHOWS THAT THE BACK EDGE OF
THE FLURRYING STATUS DECK IS MAKING GOOD PROGRESS NORTHEASTWARD AND
REALLY DONT SEE ANY REASON THIS TREND WONT CONTINUE THIS MORNING
WITH SKIES CLEARING OUT. STEEP LOW LEVEL LAPSE RATES AND LINGERING
COLD AIR ALOFT WOULD TEND TO FAVOR FAIRLY EXTENSIVE DIURNAL
STRATOCUMULUS...HOWEVER VERY DRY LOW LEVEL AIR MASS IN PLACE SHOULD
TEND TO SOMEWHAT LIMIT DIURNAL STRATOCU DEVELOPMENT.
ATTENTION THEN TURNS TO THE TROUGH/CLOSED LOW CURRENTLY OVER THE
NORTHERN INTERMOUNTAIN WEST POISED TO GET BOOTED EASTWARD ACROSS THE
LOWER GREAT LAKES SUNDAY NIGHT. MODELS ARE ALL GENERALLY DEVELOPING
A WEAK SURFACE REFLECTION AND TRACKING THAT LOW ACROSS NORTHERN
ILLINOIS SUNDAY NIGHT. TRACK OF 500MB VORT MAX AND SURFACE LOW WOULD
BOTH POINT TOWARD BAND OF ACCUMULATING SNOW SETTING UP FROM IOWA ENE
INTO SOUTHERN WISCONSIN AND POSSIBLY BRUSHING FAR NORTHERN ILLINOIS.
WILL GO AHEAD AND CARRY AND AN INCH OR SO OF SNOW ACCUM IN THE GRIDS
ALONG THE WI BORDER FOR SUNDAY NIGHT...BUT IF SFC LOW TRACK REMAINS
UNCHANGED THIS MAY BE A BIT GENEROUS WITH BETTER ACCUMS NORTH OF THE
BORDER.
INTERESTINGLY...MODELS REMAIN RATHER BULLISH WITH QPF ALONG AND
SOUTH OF THE TRACK OF THE SURFACE LOW...WHICH GIVEN NO GOOD MOISTURE
RETURN AND LESS THAN STELLAR FORCING...IT DOES LOOK SUSPICIOUS.
ISENTROPIC ASCENT SHOULD BE MAXIMIZED ALONG TIGHTER THERMAL GRADIENT
ALONG/NORTH OF LOW TRACK WITH ONLY WEAK ISENTROPIC ASCENT SOUTH FROM
THERE...CERTAINLY NOT ENOUGH TO JUSTIFY LIKELY POPS SOUTH OF
FORECAST SURFACE LOW TRACK. AM ALSO SOMEWHAT CONCERNED ABOUT P-TYPE
OVER OUR SOUTHERN COUNTIES...DESPITE FORECAST SOUNDINGS SUGGESTING
ALL SNOW...IT ISN'T COMMON TO SEE SNOW SOUTH OF A SURFACE LOW TRACK
FOLLOWING A GOOD 12+ HOURS OF WARM AIR ADVECTION. WILL LEAVE P-TYPE
AS ALL SNOW IN GRIDS ACROSS THE ENTIRE CWA FOR NOW GIVEN SUCH STRONG
SUPPORT FOR ALL SNOW IN FORECAST SOUNDINGS...BUT WOULDNT BE
SURPRISED IF ANY PRECIP THAT DOES END UP FALLING SOUTH OF THE SFC
LOW ENDS UP MIXING WITH SOME SLEET OR EVEN LIGHT RAIN.
BIGGEST WEATHER STORY CONTINUES TO BE THE STRONG SHORTWAVE CURRENTLY
CRESTING THE ALASKAN RIDGE AND MOVING ACROSS THE NORTHWEST
TERRITORY. THIS SYSTEM IS FORECAST TO CLOSE OFF A MID-LEVEL
CIRCULATION AS IT DIVES SOUTHWARD ALONG THE WESTERN NOAM COAST THIS
WEEKEND. MEDIUM RANGE MODELS THEN DIG THIS SYSTEM A BIT DEEPER INTO
THE DESSERT SOUTHWEST BEFORE EJECTING IT QUICKLY NORTHEAST TOWARD
THE GREAT LAKES BY MIDWEEK. TREND IN THE LAST COUPLE RUNS OF THE GFS
AND ECMWF HAVE BEEN FOR SLIGHTLY LESS AMPLIFICATION WHICH HAS
RESULTED IN A BIT OF A SHIFT TO THE RIGHT IN THE TRACK OF THE
SURFACE LOW WHICH IS ALSO IN LINE WITH THE UKMET. THE
CMC/DGEX/NOGAPS ALL REMAIN MORE AMPLIFIED AND FARTHER TO THE NORTH
WITH THE SURFACE LOW TRACK. REALLY ONLY TALKING ABOUT A DIFFERENCE
OF A COUPLE/FEW HUNDRED MILES IN THE FORECAST TRACK OF THE SURFACE
LOW AMONG THE VARIOUS MODELS...WHICH THIS FAR OUT ISNT ALL THAT
UNUSUAL. AT THIS DISTANCE...REALLY HARD TO HANG MY HAT ON ANY ONE
SOLUTION...THOUGH GIVEN RECENT TRENDS WOULD SUSPECT A SOLUTION MORE
IN LINE WITH THE LATEST GFS/ECMWF/UKMET PROBABLY IS THE WAY TO GO.
SHOULD THE LESS AMPLIFIED/FARTHER SOUTHWARD TRACK IN THE ECMWF AND
GFS VERIFY...THEN MOST IF NOT ALL OF OUR CWA WOULD REMAIN COLD
ENOUGH FOR ALL SNOW. WHILE THE 500MB AND MSLP ANOMALIES SUGGEST
THAT WE WOULD STILL BE LOOKING AT A STRONG SYSTEM...IT WOULD LIKELY
BE MOVING TOO QUICKLY TO REALLY TAP INTO QUALITY GULF MOISTURE. THE
FAST MOVEMENT WOULD ALSO TEND TO ARGUE AGAINST A GANGBUSTERS TYPE
QPF EVENT. THE CMC/NOGAP/DGEX SOLUTION WOULD TAKE THE SFC LOW ON AN
UNFAVORABLE TRACK FOR SNOW FOR OUR CWA...WITH A TRANSITION FROM
SNOW/MIX TO RAIN MORE LIKELY IN THIS MODEL CAMP.
REALLY HARD TO IMPROVE UPON GOING FORECAST AT THIS DISTANCE WITH
LIKELY POPS CERTAINLY JUSTIFIABLE. P-TYPE AND AMOUNTS WILL HINGE ON
THE EVENTUAL TRACK THIS SYSTEM TAKES...WHICH QUITE FRANKLY IS
ANYONES GUESS AT THIS POINT. MODEL TRENDS WILL CERTAINLY NEED TO BE
WATCHED THE NEXT COUPLE/FEW DAYS AS THERE IS DEFINITELY A CHANCE OF
SIGNIFICANT SNOW IN OUR NECK OF THE WOODS. WITH ALL MEDIUM RANGE
MODELS FORECASTING AN INTENSE SURFACE LOW EAST OF THE AREA BY WED
NIGHT INTO THURSDAY IT WOULD SEEM THAT STRONG WINDS ARE PROBABLY THE
ONE THING THAT CAN BE FORECAST WITH A MODERATELY HIGH DEGREE OF
CONFIDENCE AT THIS DISTANCE.
NO CHANGES MADE TO THE FORECAST BEYOND WEDNESDAY.
IZZI
&&
.AVIATION...
442 AM CST
1200 UTC TAFS...AREAS OF VFR STRATOCU SPITTING OUT A FEW FLURRIES
PERSIST ACROSS THE LOCAL TERMINALS AS MID LEVEL TROUGH AXIS
CURRENTLY OVER SE MN AND EASTERN IA. AS TROUGH CONTINUES TO ROTATE
ACROSS THE AREA TO LAKE MI AND IND BY LATE MORNING STRATOCU TO
TRANSITION FROM OVC TO BKN TO SCT TO SKC WITH JUST SOME CI ON THE
WESTERN HORIZON TO EVENTUALLY SPREAD OVERHEAD AS NOSE OF JET MAX
S OF SHEARING UPPER LO ON MT-WY BORDER PUSHES ACROSS THE MID MO
VALLEY AND THEN ACROSS THE MID MS VALLEY BY LATER AFTERNOON.
SW SFC FLO TO PERSIST BETWEEN NE-SW RIDGE AXIS FROM E TX OVER THE
LOWER AND MID OH VALLEY INTO THE AND THE TROUGHING DROPPING
SOUTHEASTWARD OVER THE UPPER MIDWEST. GRADIENT TIGHTENS OVER LOCAL
AREA SOMEWHAT OVERNIGHT AS CENTER OF ANTICYCLONE MOVES FM LA TO
THE TN VALLEY BUT SFC TO BE FAIRLY WELL DECOUPLED AT THIS TIME.
TRS
&&
.MARINE...
126 AM CST
MODERATE TO FRESH SW BREEZE TODAY BETWEEN NE-SW ORIENTED SURFACE
RIDGE FROM THE ST. LAWRENCE VALLEY ACROSS THE MIDWEST AND LOWER OH
VALLEY..AND MODEST LOW PRESSURE MOVING SE TO THE MID MO VALLEY.
WIND TO SHIFT TO NW ACROSS NORTHERN PORTION OF LAKE MI OVERNIGHT
TONIGHT AND EARLY SUN MORNING AS WEAK COLD FRONT/SURFACE TROUGH
THOUGH EXPECTED TO BE RATHER LIGHT AT THIS TIME. WEAK LOW
PRESSURE TO MOVE NE ACROSS THE MID MS VALLEY OVERNIGHT SUNDAY AND
EARLY MONDAY...TRACKING ACROSS THE SOUTHERN PORTION OF THE LAKE.
THREAT OF SIGNIFICANT STORM SYSTEM TO AFFECT THE REGION FROM TUE
EVENING THROUGH THU AS DEEP LOW PRESSURE TRACKS FROM THE KS-OK
BORDER AREA CURVING NORTHEASTWARD ACROSS THE MID MS VALLEY AND
INTO THE CENTRAL GREAT LAKES. CONSENSUS OF LATEST MODELS IS THAT
THE LOW WILL BE NEAR/OVER FAR SOUTHERN LAKE BY AT 12Z WED WITH
STRONG COLD ADVECTION SPREADING ACROSS THE REGION AS THE SYSTEM
LIFTS INTO SOUTHERN ONTARIO DURING THE DAY WITH GALES POSSIBLE WED
NIGHT ON THE S 1/2.
TRS
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
