000
FXUS63 KILX 032045
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
245 PM CST WED DEC 3 2008
.DISCUSSION...
ISSUED 245 PM CST WED DEC 3 2008
INITIAL CONCERN DEALS WITH PRE FRONTAL SPRINKLES/LIGHT RAIN THAT IS
FINALLY BEGINNING TO DEVELOP...AND POST FRONTAL SNOW FOR LATE THIS
AFTERNOON AND EVENING. THEN ATTENTION TURNS TO THE COLD FRONT AND
SNOW CHANCES FOR FRIDAY NIGHT AND SATURDAY. NEXT WEEK MONDAY NIGHT
AND TUESDAY ANOTHER STORM IS TAKING SHAPE IN THE CENTRAL
PLAINS...PASSING BY TO OUR SOUTH. A BAND OF SNOW MAY DEVELOP IN
OUR AREA ON THE NORTH SIDE OF THAT LOW...BUT PRECIP TYPE/TIMING
AND THE PATH OF THE LOW ARE STILL IN QUESTION. WILL BE CONTINUING
SOME MENTION OF PRECIP WITH THAT SYSTEM.
MODELS ARE IN RELATIVE AGREEMENT ON THE EVENING WEATHER
SCENARIO. THE RUC SEEMS TO HAVE A GOOD HANDLE ON THE CURRENT
CONDITIONS A PROGRESSION...SO WILL LEAN TOWARD THE RUC FOR THE
NEAR TERM AND USE A BLEND FOR THE REMAINDER OF THE SHORT TERM
FORECAST. THE MODELS ARE NOT FAR APART WITH THE EARLY WEEKEND
COLD FRONT. THE NAM IS MORE CONSERVATIVE WITH THERMO- DYNAMICS AND
KEEPS PRECIP FARTHER NORTH THAN THE GFS. THE ECMWF IS IN THE
MIDDLE...AND SEEMS LIKE A REASONABLE SOLUTION.
SHORT TERM...TONIGHT THROUGH FRIDAY.
THE COLD FRONT HAS FINALLY REACHED A LINE FROM SHELBYVILLE TO
CMI AS OF 19Z. THE NARROW REGION OF JET DYNAMICS IS ENTERING OUR
CWA AND THE BAND OF SNOW HAS REACH A LINE FROM MACOMB TO LACON.
RAIN HAS ALSO DEVELOPED JUST AHEAD OF THE FRONT IN
CMI/DNV/MTO...AND THAT AREA OF PRECIP SHOULD CONTINUE TO EXPAND
SOUTHEAST THROUGH EARLY EVENING.
BASED ON UPSTREAM SNOW REPORTS...RADAR TRENDS...AND THE LATEST
RUC MODEL...IT APPEARS THE BEST SNOW PRODUCTION IN OUR CWA WILL BE
MAINLY CONFINED TO THE AFTERNOON HOURS...WITH TAPERING SNOW
SHOWERS THIS EVENING AS THEY PROGRESS EASTWARD. OUR N CWA WILL
MOSTLY LIKELY SEE AROUND 1 INCH OF SNOW AS FAR SOUTH AS PIA...WITH
UP TO 2 INCHES FOR GBG TO WYOMING. A HALF INCH MAY FALL AS FAR
SOUTH AS HAVANA TO BLOOMINGTON...WITH A DUSTING TO TRACE AMOUNTS
SOUTH OF THERE. DUE TO THE VARIABLE NATURE AND TIMING OF THE
SNOW...WILL BE INCLUDING A LATE AFTERNOON SECTION FOR THE
AFTERNOON ZONES. THIS WILL HIGHLIGHT THE HEAVIER SNOWS IN THE
NW...AND THE RAIN IN THE E LATER THIS AFTERNOON.
TURBULENT MIXING BEHIND THE FRONT WILL PRODUCE GUSTY WINDS UP TO 25
MPH...WHICH WILL BLOW AND DRIFT THE 1 TO 2 INCHES OF SNOW THAT
FALLS IN THE NORTH. TRAVEL WILL BE DIFFICULT DESPITE A RELATIVELY
LOW AMOUNT OF SNOW. PLENTY OF COLD AIR WILL FILTER INTO OUR AREA
BY MORNING...WITH MID TEENS FOR LOWS IN OUR NW ZONES. THOSE COLD
TEMPS WILL ADD TO TRAVEL HAZARDS FOR THE MORNING...AS ANY MELTING
FROM ROAD TREATMENTS WILL HAVE A CHANCE TO REFREEZE. THE SAME
SENTIMENT WILL APPLY TO THE EAST WHERE SOME RAIN FALLS THIS AFTERNOON
AND EVENING.
THE PRECIP IS EXPECTED TO COME TO AN END BY MIDNIGHT...WITH
PARTIAL CLEARING POSSIBLE IN THE WEST. THAT WILL HELP TEMPS FALL
TO EXPECTED LOWS IN THE TEENS IN THE NW.
THURSDAY SHOULD FEATURE CONTINUED CAA UNDER SURFACE RIDGING. TEMPS
WILL STRUGGLE TO CLIMB THROUGH THE 20S IN MOST AREAS...DESPITE
SOME PERIODS OF SUNSHINE. A FEW FLURRIES WILL BE POSSIBLE FROM PIA
AND NORTH...AS UPPER LEVEL DPVA OCCURS AHEAD OF AN H5 VORTEX. H85
TEMPS WILL DROP FROM -10C TO -13C IN THE NORTHERN HALF OF THE CWA.
THAT WILL PUT HIGHS AROUND NORMAL LOWS FOR THIS TIME OF YEAR.
THURSDAY NIGHT...A CONTINUED CHANCE OF FLURRIES IS EXPECTED IN THE
NORTH...AS THE UPPER TROUGH CONTINUES TO DROP SE ACROSS OUR
AREA...PROVIDING ADDITIONAL COOLING IN THE LOWER TROP. H85 TEMPS
WILL DIP TO -15C BY 12Z FRI MORNING. THAT WILL SET THE STAGE FOR
ANOTHER VERY COLD MORNING AND DAY FRIDAY...WITH LOWS AND HIGHS
WELL BELOW NORMAL.
LONG TERM...FRIDAY NIGHT THROUGH WEDNESDAY.
THE NEXT COLD FRONT IS EXPECTED TO PASS ACROSS OUR CWA LATE FRIDAY
NIGHT AND SATURDAY...AS A CLIPPER SURFACE LOW MOVES ACROSS S
MN...WI AND LOWER MICHIGAN. ALL MODELS INDICATE A FOCUSED AREA OF
WAA WILL ACCOMPANY AN AREA OF Q-VECTOR CONVERGENCE DURING THAT
TIME. THE GFS IS MORE PRONOUNCED...BUT IS SUPPORTED BY THE ECMWF
AND NAM. FOLLOWING AN ECMWF SOLUTION...WE EXPECT THE FORCING
SHOULD BE ENOUGH TO PRODUCE LIGHT ACCUMULATING SNOWS IN THE
NORTHERN HALF OF THE CWA...WITH TRACE AMOUNTS SOUTH OF THERE.
ACCUMULATION AROUND AN INCH WILL BE POSSIBLE FRI NIGHT AND
SAT...ESPECIALLY N OF I-74. GUSTY NW WINDS ARE EXPECTED BEHIND
THAT FRONT...WHICH WILL BLOW AROUND THE LIGHT SNOW THAT FALLS
EARLIER IN THE DAY. A REINFORCING SHOT OF COLD AIR WILL ALSO TRAIL
THE FRONT. TEMPS SAT NIGHT AND SUNDAY WILL BE 10 TO 15 DEG BELOW
NORMAL.
THE GFS AND ECMWF ARE TRYING TO RESOLVE THE STORM SYSTEM FOR THE
FIRST HALF OF NEXT WEEK. THE 12Z ECMWF ALTERED ITS SOLUTION FROM
THE 00Z RUN QUITE A BIT. IT NOW IS KEEPING THE PRIMARY LOW NORTH
OF ILLINOIS...WITH WEAKER SECONDARY CYCLOGENESIS SOUTH OF US...AND
LATER IN THE SYSTEM PROGRESSION. THE NEW SOLUTION IS PUTTING A
SHORT PERIOD OF PRECIP IN THE SE HALF OF OUR CWA MONDAY NIGHT AND
PUSHING THE TUESDAY PRECIP EAST OF ILLINOIS. THE 12Z GFS CONTINUES
TO SHOW A STRONGER LOW TO OUR SOUTH...AND A LONGER PERIOD OF
PRECIP CONTINUING ON TUESDAY IN THE SE HALF OF THE CWA. THEY ARE
BOTH TRENDING TWRD DRIER CONDITIONS IN THE NW HALF OF THE
CWA...BUT WILL NOT TRY TO GET TOO FANCY WITH POPS JUST YET.
SHIMON
&&
.AVIATION...
ISSUED 1132 AM CST WED DEC 3 2008
NOT A LOT OF CHANGE IN THE FORECAST FOR THE AFTERNOON AND
OVERNIGHT. RAIN SHOWERS AHEAD OF THE FRONT MAY BE SCATTERED ENOUGH
TO NOT WARRANT A MENTION IN ANY ONE PARTICULAR TERMINAL.
HOWEVER...FRONT SEEMS TO BE RIGHT ON TRACK...THOUGH PROGRESSING
SLOWLY. POST FRONTAL SNOW LAGGING BEHIND THE WIND SHIFT SOMEWHAT.
CIGS ON THE WAY TO MVFR AS THE WARM MOISTURE SURGE FROM THE SOUTH
CATCHES UP WITH THE DROPPING CIGS ASSOCIATED WITH THE COLD FRONT.
AFTERNOON PRECIP THAT DEVELOPS ACROSS THE SOUTH MAY STILL REMAIN
LIQUID FOR DEC AND SPI BEFORE THE COLD AIR CATCHES UP TO CHANGE
THE PRECIP OVER TO SNOW. SNOW TONIGHT WITH VISBY DROPPING TO
IFR/LIFR CONDITIONS UNTIL MIDNIGHT. ON THE OTHER SIDE OF 06Z...NO
PRECIP AND VFR.
HJS
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
