FXUS63 KIWX 031048
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
548 AM EST THU DEC 3 2009

.AVIATION...
MULTICELLULAR LAKE EFFECT BAND COMING ONSHORE IN BERRIEN COUNTY
WILL BRING PERIODIC SHOWERS TO KSBN WHERE VFR VSBYS AND MVFR CIGS
WILL PERSIST. EXPECTING PREDOMINATELY LIQUID AS BAND COMING OFF
WARMER MARINE LAYER WILL DELAY TRANSITION UNTIL COLDER AIR WORKS
IN THIS MORNING...BUT A CHANGEOVER TO A MIX OR NON ACCUMULATING SNOW
SHOWER IS STILL POSSIBLE TODAY BEFORE WINDS BACK TO WEST SHIFTING
LAKE EFFECT NORTH OF TERMINAL. LOW STRATUS MVFR CIGS WILL CONTINUE
THROUGH THE PD AT KSBN WHILE KFWA SHOULD IMPROVE TO LOW VFR PER
UPSTREAM OBS ONCE WINDS BACK ENOUGH TO PUSH ENHANCED CLOUDS TO THE
NORTH. FLURRIES ARE POSSIBLE THIS AFTERNOON THROUGH THE END OF TAF
PD WITH NW WINDS BACKING WSW 10-15 KNOTS. 

&&

.PREV DISCUSSION... /ISSUED 342 AM EST THU DEC 3 2009/ 

SHORT TERM...

RAINY EARLY DECEMBER SYSTEM DEPARTING THE REGION TONIGHT WITH THE LAST
VESTIGES OF DEFORMATION ZONE DRIFTING THROUGH THE CWA. LAST
NIGHTS 00Z NAM NAILED THE SFC LOW TRACK BUT FAILED TO GRASP
MAGNITUDE OF DEEPENING AND AS A RESULT UNDERESTIMATED WARMTH OF BL
OVER THE CWA. PTYPE HAS REMAINED RAIN EVERYWHERE...EXCEPT FOR A
FEW WIDELY DISPERSED AND LOCALIZED AREAS WHERE HEAVIER PRECIP
PRODUCED ENOUGH DIABATIC COOLING TO BRIEFLY TURN PRECIP OVER TO
SNOW...BEFORE SHIFTING RIGHT BACK TO LIQUID.

IN SYSTEMS WAKE...THE CWA WILL BE LEFT WITH A CLOUDY DREARY DAY WITH 
CAA KEEPING ANY SIGNIFICANT TEMP RECOVERY AT BAY. MAX TEMPS
UPSTREAM YDAY WERE ONLY IN THE MID 30S...AND HIGHS FOR TODAY HAVE
BEEN KEPT BELOW GUIDANCE AS PERSISTENTLY CLOUDY SKIES TAKE HOLD
WITH FLURRIES POSSIBLE AS UPPER TROF CONTINUES TO BUILD SOUTHEAST.
ANY CHANCE OF MEASURABLE SNOW APPEARS RESTRICTED TO AREAS SUBJECT
TO LAKE EFFECT THIS AFTERNOON THROUGH FRIDAY AS VERY COLD AIR
MOVES IN WITH NW WINDS BACKING TO WSW BY FRIDAY NIGHT. THIS
SCENARIO HAS NOT CHANGED MUCH OVER THE PAST FEW MODEL CYCLES AND
GRIDS REFLECT FEW CHANGES. LIMITED WINDOW OF OPPORTUNITY FOR MOST
OF THE NW CWA AS WINDS BACK TODAY WITH ONLY BERRIEN/WESTERN CASS
COUNTIES HAVING MUCH OF A CHANCE TO SEE ANY ACCUMULATION AFTER
00Z.

FRIDAY NIGHT COULD BE SETTING UP AS COLDEST NIGHT SO FAR THIS SEASON 
AS SFC RIDGE AXIS IS SITUATED JUST TO OUR SOUTH WHILE CLOUDS ASSOC 
WITH WAVE ADVANCING ALONG THE GULF COAST ARE PROGGED TO REMAIN JUST 
OUTSIDE THE CWA. HAVE TRENDED TOWARDS COLDER MET GUIDANCE FOR LOWS
IN THE MID TO UPPER TEENS.

LONG TERM...
NRN STREAM TROUGH EXTENSION WILL FLATTEN IN RESPONSE TO RENEWED HGT 
FALLS ACRS THE WRN US. WK DISTURBANCE OVR THE NEPAC WILL START THIS 
PROCESS YET LIFT OUT IN FAIRLY FLAT DOWNSTREAM FLW EARLY NXT WEEK. 
THUS W/LTL FLW AMPLIFICATION TO THIS SYS AND RESULTANT LACK OF MSTR 
DOUBT IT PROMOTE MUCH IN WAY OF SIG PCPN POTENTIAL ON MON AND WILL 
LEAVE GOING LOW CHC POPS IN PLACE. GOOD MED RANGE CONSENSUS ON THE 
OTHER HAND SUGGESTS DROPPING SAID MENTION MON NIGHT W/WELL AGREED 
UPON SFC RIDGING BLDG IN.

MORE INTERESTING SYS STILL SLATED MID NXT WEEK W/RATHER DRAMATIC 
EPAC RIDGE/WRN US TROUGH AMPLIFICATION SHOWN. STILL PREFER THE 
SHARED DEEPER SOLUTIONS SEEN IN GFS/GGEM AS OPPOSED TO THE MORE 
PROGRESSIVE/WEAKER ECMWF GIVEN UPSTREAM RIDGING BLDG NWD INTO 
SIBERIA. BUT W/THAT SAID...PREVAILING MULTI-STREAM FLW AND PROBABLE 
REX BLOCK DVLPMNT OVR WRN CANADA WILL KEEP INTENSE BLD UP OF ARCTIC 
COLD CONFINED TO WRN/NRN CANADA FOR SOMETIME. A PIECE OF THIS WILL 
BREAK SWD BEHIND MID WEEK SYS AND XPC TEMPS WILL CONT BLO NORMAL 
THROUGH THE PD.

AVIATION...
SFC LOW TRACKING AS FCST TRACK CENTERED NEAR KCLE WITH DEFORMATION
BAND CONTINUING TO BRING PRECIPITATION TO THE FA. LOW HAS CONTINUED
TO DEEPEN BRINGING WARMER BL MOISTURE INTO THE FA KEEPING PTYPE
ALL RAIN. STILL EXPECT A MIX OF RASN AT KSBN AFTER 12Z WITH
CONTINUED VIS/CIG RESTRICTION AS WINDS BACK NW ROTATING A BAND OF
LAKE ENHANCED MOISTURE ACROSS THE TERMINAL TODAY PERPETUATING MVFR
VIS. AT KFWA...MORE INTENSE PRECIP WITHIN DEFORMATION MAKING ITS
WAY OVER THE TERMINAL AT ISSUANCE...BEHIND WHICH VFR VIS IS
EXPECTED TO RETURN. EVEN OUTSIDE OF LAKE INFLUENCE KFWA LOW CIGS
WILL CONTINUE FOR TODAY WITH FLURRIES OR A WIDELY SCATTERED SNOW
SHOWER CAA TAKES HOLD. WIND WILL CONTINUE WSW 10-15 KNOTS TONIGHT
AS CONDITIONS RETURN TO VFR.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 7 AM EST FRIDAY FOR LMZ043-046.

&&

$$

SHORT TERM...LUD 
LONG TERM...T
AVIATION...LUD