FXUS63 KIWX 250845
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
345 AM EST FRI DEC 25 2009
.SHORT TERM...
STRONG LOW PRESSURE THAT WILL PLAGUE THE CWA THROUGH THE WEEKEND
SLOWLY LIFTING THROUGH EASTERN MISSOURI. BROAD AREA OF
PRECIPITATION LEADING ALL THE WAY TO ITS STRONG GOMEX CONNECTION IS
LIFTING NORTHWARD TO THE EAST OF THE LOW WHILE UPPER WAVE CENTERED
JUST SOUTH OF THE SFC CIRCULATION WILL ALSO LIFT NORTH AND PHASE
WITH SECONDARY WAVE DROPPING SOUTH ALONG THE LEE OF THE ROCKIES.
SFC LOW WILL BECOME DEEPLY OCCLUDED AS IT RETROGRADES INTO WESTERN
IOWA BEFORE LOOPING BACK TO THE NE ALONG WITH ITS WOBBLING UPPER
CIRCULATION.
SOUTHERN END OF THE STEADY RAINS WITH DEEP MOISTURE PLUME IS LIFTING
INTO THE SW CORNER OF THE CWA AS DRY SLOTTING ESP ABOVE H7 IS
WORKING NORTHWARD OVER THE CWA. PRECIPITATION WILL BECOME MORE
INTERMITTENT IN NATURE THOUGH ENOUGH ACTIVITY IS ONGOING AND
REDEVELOPING UPSTREAM TO CONTINUE CATEGORICAL POPS. AS COLD AIR
WRAPS AROUND OCCLUDING SFC LOW FRONT WILL LIFT FROM SOUTHWEST TO
NORTHEAST DURING THE AFTERNOON CHANGING RAIN SHOWERS OVER TO SNOW
SHOWERS WHICH WILL REMAIN VARIABLE AND LIGHT INTO FRIDAY NIGHT.
AS THE LLEVEL CIRCULATION SLOWLY WEAKENS AND WHILE MEANDERING WITH
THE UPPER LOW TO OUR WEST AND NORTHWEST...SNOW SHOWERS WILL BE
POSSIBLE THROUGH THE REMAINDER OF THE SHORT TERM PERIOD. PROBLEMATIC
TO ATTEMPT TO PINPOINT BETTER CHANCES AFTER FRIDAY NIGHT AS MORE
MOISTURE WRAPS AROUND THE LOW INTO THE CWA...THUS NO MAJOR CHANGES
TO GRIDS WITH TWEAKS FOR 00Z MODEL RUNS INCLUDING A SLOWER
CHANGEOVER TO SNOW...INCREASE IN HIGH TEMPS TODAY BEFORE COLD AIR
ARRIVES... AND MINOR CHANGES TO SAT/SAT NIGHT QPF/SNOW AMTS WHEN
WEAKENING SFC/H85 CIRCULATION IS LOCATED JUST TO OUR WEST.
&&
.LONG TERM.../SUNDAY THROUGH THURSDAY/...
ONCE AGAIN LONG TERM GRIDS IN VERY GOOD SHAPE AND FEW CHANGES
NEEDED. GENERALLY FOLLOWING ECMWF WHICH CONTINUES TO HAVE GOOD RUN
TO RUN CONTINUITY AND MATCHES WELL WITH INHERITED GRIDS.
PHASED UPPER LOW LOOKS LIKE IT WILL FINALLY BE MAKING ITS LAST LOOP
IN THE MIDWEST ON SUNDAY AND BEGINNING TO TRANSLATE EAST IN RESPONSE
TO SHORT WAVE DROPPING SOUTH OUT OF CENTRAL CANADA. THIS KICKER
SHORT WAVE WILL BRING A BRIEF SHOT OF COLD AIR MONDAY INTO MONDAY
NIGHT BUT MODELS NOW INDICATING MORE OF A GLANCING BLOW WITH CORE OF
COLDEST AIR MOVING THROUGH THE EASTERN LAKES. SHOULD SEE A PERIOD OF
LIGHT SNOW SHOWERS ON SUNDAY AS UPPER LOW MOVES ACROSS AREA AND
POTENT VORT MAX ROTATES AROUND LOW. TIMING AND AMOUNT OF MOISTURE
REMAINS IN QUESTION ON SUNDAY. HIGH CONFIDENCE IN SNOW SHOWER
ACTIVITY BUT LOW CONFIDENCE IN WHETHER THERE WILL BE ENOUGH MOISTURE
AND LIFT TO MEASURE. GFS MORE AGGRESSIVE THAN ECMWF WITH MOISTURE
PROFILES. UPPER LOW WILL BE FILLING WITH WEAKENING SURFACE LOW AS IT
MOVES EAST BUT THIS SYSTEM HAS BEEN QUITE MOIST AND DYNAMIC SO
SUSPECT IT WILL BE ABLE TO CONTINUE PRODUCING AT LEAST LIGHT SNOW.
HAVE CHANGED WX WORDING TO REFLECT SCATTERED SNOW SHOWERS WITH LIGHT
ACCUMS POSSIBLE.
AS LOW MOVES EAST EXPECT A NORTHWEST FLOW TO DEVELOP IN ITS WAKE
WITH DELTA T VALUES INTO THE MID TEENS. CONCERN THOUGH THAT MODELS
NOT BACKING WINDS ENOUGH AHEAD OF KICKER SHORT WAVE DIVING OUT OF
CANADA SO BAND DEVELOPMENT AND POSITION REMAINS A CONCERN. WILL
CONTINUE CHANCE POPS DOWNSTREAM OF LAKE WITH REFINEMENT LATER AS
HIGHER RESOLUTION MODELS BEGIN TO PICK UP THIS TIME FRAME.
HIGH PRESSURE WILL MOVE ACROSS THE REGION TUESDAY WITH LAKE
AGGREGATE TROUGH HOLDING ON IN NORTH WITH LINGERING CLOUDS. WILL
LIKELY SEE MORE CLEARING WITH THIS HIGH BUT CLIMATOLOGY AND WEAK
UPPER SHORT WAVES SUGGEST A CONSERVATIVE PARTLY CLOUDY FOR NOW
EXCEPT IN FAR SOUTH WHERE CLEARING MORE LIKELY. HIGH WILL SLIDE
EAST BY WED WITH YET ANOTHER SHORT WAVE APPROACHING WHICH COULD
BRING SOME LIGHT SNOW BACK TO THE AREA IN DAY 7 TO DAY 8 TIME FRAME.
00Z ECMWF BRINGS A VERY COLD POCKET OF AIR INTO THE REGION BY DAY 8.
&&
.AVIATION...
DEEP LOW PRESSURE LIFTING SLOWLY THROUGH MISSOURI PROMISES STEADY
RAINS OVERNIGHT WHICH HAVE BEGUN AT THE TERMINALS IN THE PAST
HOUR. HEAVIEST PRECIP STILL TIMED FOR MORNING INTO EARLY AFTERNOON
WHERE IFR CIGS ARE EXPECTED TO PREVAIL...BUT BASED ON OBS UNDER
PRECIPITATION UPSTREAM HAVE IMPRVOED PREVAILING VSBYS TO MVFR.
WIND SHEAR STILL BEING CARRIED AS MODELS CONTINUE STRONG 0.5-1KM
WINDS INTO THE AFTERNOON PEAKING AT 60KTS DURING MORNING INTO
MIDDAY. AS DRY SLOT MOVES INTO THE REGION AFTER 18Z STEADY
IMPROVEMENT WITH SFC WINDS VEERING SOUTHERLY BUT CONTINUED GUSTING
25-30 KNOTS. SCATTERED SNOW SHOWERS CONTINUE TO END OF TAF PD AS
COLD AIR RETURNS TO THE AREA.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...GALE WARNING UNTIL 7 PM EST THIS EVENING FOR LMZ043-046.
&&
$$
SHORT TERM...LUD
LONG TERM...LASHLEY
AVIATION...LUD
