FXUS63 KIWX 152340
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
640 PM EST TUE DEC 15 2009

.AVIATION...
LAKE EFFECT CLOUDS AND LIGHT SNOW CONTINUE TO OFFER MVFR CIGS AND
VIS ACROSS PORTIONS OF MI...WITH JUST MVFR CIGS OVER EXTREME
NORTHERN INDIANA. LOOK FOR A WANING TREND IN LAKE EFFECT ACTIVITY
THROUGH THE NIGHT AS INVERSION HEIGHTS FALL AND VERY DRY AIR
PUSHES INTO THE REGION. WINDS WILL SLOWLY BACK MORE SOUTHERLY AS
HIGH PRESSURE BUILDS INTO THE REGION. NO OTHER AVIATION CONCERNS
ATTM.

&&

.PREV DISCUSSION... /ISSUED 300 PM EST TUE DEC 15 2009/ 

SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/...

VERY DRY AIRMASS RAPIDLY MOVING ACROSS THE FA THIS AFTERNOON WITH 
CLEARING SKIES ALREADY SHOWING UP IN FAR W/SW SECTIONS. EXPECT THIS 
TREND TO CONTINUE INTO THIS EVENING GENERALLY SOUTHWEST OF US 30. 
NORTHEAST OF THIS AREA...BECOMES MORE CHALLENGING DUE TO LAKE EFFECT 
ISSUES. DRY AIR ENTRAINMENT HAS COMBINED WITH THE LOW INVERSION HGT 
TO BRING ANY ORGANIZED BANDS TO A SCREECHING HALT ACROSS THE CWA. 
RADAR INDICATED POCKETS OF FLURRIES OR VERY LIGHT SNOW SHOWERS 
OCCURRING ATTM. WITH MSTR CONTINUING TO WANE AND FLOW SLOWLY 
BEGINNING TO SHIFT MORE WESTERLY AND EVEN SW INTO WEDS...HAVE 
SIGNIFICANTLY REDUCED PRECIP CHANCES INTO WEDS. ALL MENTION OF 
CAT/LIKELY POPS HAVE BEEN REMOVED AND ONLY SCT SHOW SHOWERS IS IN 
PLACE FOR THIS EVENING DOWNWIND OF THE LAKE...TAPERING TO FLURRIES 
OVERNIGHT AND EARLY WEDS. UPSTREAM CLEAR SKIES AND VERY LOW DEWPTS 
AND TEMPS SUGGESTS THAT LOWS NEED TO BE DROPPED IN FAR SW SECTIONS 
TONIGHT. HAVE LOWERED A FEW DEGREES WITH EVE SHIFT TO MONITOR 
TRENDS. 

OTHER THAN SOME LINGERING FLURRIES IN THE MORNING CLOSE TO THE 
LAKE...A DECENT DAY LOOKS TO BE SHAPING UP FOR WEDNESDAY...ALBEIT ON 
THE COOL SIDE. AFTER THE COLD START MENTIONED ABOVE...TEMPS WILL 
REBOUND INTO THE MID TO UPPER 20S. WAA WILL CONTINUE INTO WEDS NGT 
BUT LL COOLER AIR MASS WILL ALLOW FOR LOWS TO DROP INTO THE TEENS. 

LONG TERM...

..THURSDAY THROUGH TUESDAY...

FEW CHANGES NEEDED TO LONG TERM FORECAST PERIODS AS OVERALL TREND OF 
BECOMING COLDER WITH PERIODS OF LIGHT SNOW OR LAKE EFFECT SNOW 
SHOWERS STILL LOOKS ON TRACK. MEDIUM RANGE MODELS CONTINUE TO SHOW 
MANY DIFFERENCES IN THE DETAILS WITH MOST SIGNFICANT IMPACTS THIS 
WEEKEND. ZONAL FLOW STILL EXPECTED TO TRANSITION TO MORE HIGHLY 
AMPLIFIED PATTERN WITH DEEP TROUGH DEVELOPING FROM GREAT LAKES TO 
EAST COAST. MODELS STRUGGLING WITH SHORT WAVE ENERGY WITHIN THIS 
TROUGH WHICH RESULTS IN DIFFERENCES ON CLIPPER TYPE SYSTEM...DEGREE 
OF COLD AIR INTRUSION AND POSSIBLE DEVELOPMENT OF A STRONG NORTHEAST 
COAST WINTER STORM. HAVE CONTINUED TO SIDE TOWARD A COLDER PATTERN 
WITH DEVELOPING TROUGH NEARLY CERTAIN. GFS SHOWING NUMEROUS SHORT 
WAVES AND NOT AS AMPLIFIED AS ECWMF...THUS GFS IS WARMER NOW THAN 
PREVIOUS RUNS. GRIDS GENERALLY IN AGREEMENT WITH HPC WHICH TAKES A 
MORE MIDDLE OF THE FIELD APPROACH WITH SLIGHT NOD TOWARD ECMWF. WEAK 
SHORT WAVES TO BRING FLURRIES OR LIGHT SNOW AT TIMES BUT DETAILS 
REMAIN SKETCHY AND NO MORE THAN LOW CHANCE POP THROUGH SEVERAL 
PERIODS WARRANTED AT THIS TIME. ECMWF DOES SHOW A SLIGHT NEGATIVE 
TILT TO CLIPPER SYSTEM WITH WEAK LOW DEVELOPING IN OHIO VALLEY SAT 
AND SAT NIGHT AND INVERTED TROUGH INTO OUR AREA. OTHERWISE EXPECT 
PERIODS OF LAKE EFFECT SNOW SHOWERS WITH DELTA T VALUES IN MID TO 
UPPER TEENS BUT GIVEN NUMEROUS UNRESOLVED SHORT WAVES A RATHER BROAD 
AREA HAS BEEN OUTLINED WITH LOW CHANCE POPS.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 5 PM EST WEDNESDAY FOR LMZ043-046.

&&

$$

SHORT TERM...FISHER
LONG TERM...LASHLEY
AVIATION...JC