FXUS63 KIWX 140541
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
1241 AM EST TUE FEB 14 2012
.AVIATION...
LIGHT SNOW IMPACTING BOTH TAFS SITES WITH MVFR/IFR CONDITIONS TO
SETTLE IN THROUGH THE NIGHT. WHILE MAIN IMPACT WILL BE FROM
LOWERING CIGS...POCKETS OF VSBYS BETWEEN 1/2SM AND 1SM WILL BE
POSSIBLE WITH A HANDFUL OF UPSTREAM SITES IN ILLINOIS REPORTING
THIS FROM TIME TO TIME. SNOW WILL LIKELY TAPER OFF TOWARDS 12Z
BUT STILL POTENTIAL FOR SOME LINGERING DRIZZLE OR FREEZING DRIZZLE
THROUGH THE MORNING. DESPITE ENDING OF PRECIP...CONTINUATION OF
IFR CIGS ANTICIPATED THROUGH 06Z. 
&&
.PREV DISCUSSION... /ISSUED 959 PM EST MON FEB 13 2012/ 
UPDATE...
GOING FCSTS IN GOOD SHAPE AND ONLY MINOR CHANGES MADE THIS EVE.
LOW LEVEL WAA AHEAD OF TROF MOVG INTO IA/MO THIS EVE WAS PROVIDING
SUFFICIENT LIFT TO SUPPORT A RATHER LARGE AREA OF LIGHT SNOW
SPREADING INTO OUR CWA. DTX/ILN EVE SOUNDINGS VERY DRY IN LOW
LEVELS AS EXPECTED... BUT OBS/RADAR SUGGESTS SATURATION OCRG FROM
SW-NE ACROSS OUR AREA. MADE MINOR ADJUSTMENT TO POP/QPF GRIDS TO BETTER
REFLECT THE ORIENTATION OF SNOW OVERSPREADING THE AREA IN THE 03Z-
06Z TIMEFRAME...BUT OVERALL GOING FCST REASONABLE WITH 1-2 INCHES
TOTAL ACCUMS EXPECTED ACROSS THE AREA....PROBABLY HEAVIEST ACROSS
SWRN 1/2 OF CWA WHERE BETTER MOISTURE WILL BE AVAILABLE.
PREV DISCUSSION... /ISSUED 400 PM EST MON FEB 13 2012/
SHORT TERM... / TONIGHT THROUGH TUE NIGHT /
PRIMARY FOCUS ON SNOW ACCUM WITH TONIGHTS SYSTEM. FAVORING STRONG
AGREEMENT IN SHORT TERM OF ARW/NAM/PAST TWO ECMWF/GFS IN HANDLING
OF UPSTREAM DISJOINTED OPEN WAVE ACRS CNTL PLAINS WITH MULTIPLE
MINOR EMBEDDED WAVES. THIS SYSTEM EXHIBITING SPORADIC DOWNSTREAM
POCKETS OF DEEPER MSTR PER WV IMAGERY PRESENTING AS A LARGELY
DISHEVELED APPROACHING. MUNDANE DENDRITIC GROWTH ZONE DEPTH AND
SATURATION WITHIN...SAVE FOR WRN/NWRN CWA WHERE EARLIER
PRECONDITIONING NOTED...SHOULD MAKE FOR RATHER MEAGER RATIOS
OVERALL. IN ADDITION...WARM NEAR FREEZING SFC TEMPS SHOULD ALLOW
FOR TIGHT COMPACTION OF PRIMARILY SMALLER NON-AGGREGATED FLAKES.
GNRLY INCH OR LESS OVERNIGHT...SAVE FOR WRN CWA IN AFOREMENTIONED
HIR SATURATION LEVEL IN DGZ AND SRN TIER OF CWA WHERE GRTR BULK
MSTR RESIDES WITH 2.8-3 G/KG WITHIN UPSLOPING 280-285K ISENT LYR.
GNRL ASCENT PER MIDLVL HGHT FALLS MAXIMIZED NOW THROUGH 06 UTC
TONIGHT...THEN FALTER TOWARD DAYBREAK INTO LWR GRTLKS/NEW ENGLAND
CONFLUENCY. LOSS OF ICE NUCLEATION IN MORE SHALLOW MSTR SPREADS
W-E ACRS IN/MI TUE MORNING AND TO NWRN OH BY AFTN. WEAKENING
ASCENT/MSTR TO GRTLY HAMPER ACCUM POTNL...MINOR/TRACE PATCHY FZDZ
RETAINED COINCIDENT WHERE COLD BLYR SLOWLY RECEDES. BY SFC TEMPS
SHOULD WARM TO JUST AOA FZG IN CONTD WEAK LLVL WAA FOR CHANGEOVER
TO PTCHY DZ/LIGHT DIMINISHING SNOW CHCS FM W-E. OPTED FOR NO
MENTION ATTM FOR PTCHY FZDZ TUE GIVEN LACK OF IMPETUS SEEN FOR
VIGOROUS MIXING WITH GNRTY WEAK WIND FIELD/WEAK VERTICAL MOTION IN
THE LINGERING/VERY MOIST BLYR. WEAK ZONALLY-ORIENTED ND WAVE TO
REMAIN ORPHANED FM PLAINS SYSTEM PUSHING EWD. THIS WAVE TO ALSO
UNDERGO SIG MINORING TUE AS IT MOVES INTO THE WRN GRTLKS TUE NIGHT
IN RESPONSE TO MORE UNIFIED MERIDIONAL NRN CANADA TO SWRN STATES
ND PLAINS SYSTEM TO AFFECT REGN WED NIGHT INTO THU TIMEFRAME...AND
ANYHOW INFLUENCE SHOULD LKLY REMAIN NORTH OF CWA.&&
LONG TERM... / WEDNESDAY THROUGH MONDAY /
A SOUTHERN STREAM POSITIVE PV ANOMALY OVER CALIFORNIA WILL ROUND THE 
BASE OF A WESTERN CONUS MEAN TROUGH...AND THEN QUICKLY EJECT NEWD 
TOWARDS THE SOUTHERN GREAT LAKES WED NIGHT-THU ON THE NOSE OF A 140 
KT UPPER JET STREAK. THIS COMPACT YET POTENT SHORTWAVE LOOKS TO AT 
LEAST PARTIALLY PHASE WITH A NORTHERN STREAM SHORTWAVE DIGGING IN 
BEHIND IT...WITH THE ASSOCIATED DEEPENING SFC LOW PROGGED TO TRACK 
THROUGH THE FA. THIS WOULD LIKELY RESULT IN A PERIOD OF MODERATE 
RAIN FOR MOST LOCATIONS AS AMPLE GULF MOISTURE GETS DRAWN NWD INTO 
THIS SYSTEM WITH PCPN MAINLY TIED TO THE 9-7H THETA-E SURGE AND 
STRONG DEEP LAYERED QG FORCING. EXPECT RAINFALL NEAR A HALF INCH FOR 
MOST LOCATIONS WITH THE BULK OF THIS PCPN FALLING WED NIGHT INTO THU 
MORNING. THERE REMAINS THE CHANCE THAT PCPN COULD BEGIN AS A BRIEF 
PERIOD OF WET SNOW OR SLEET WEDNESDAY NIGHT IN THE NORTH GIVEN THE 
INITIAL DRY 9-6H LAYER. DEFORMATION/FGEN FORCED MIXED PCPN MAY CLIP 
OUR NORTHWESTERN ZONES THURSDAY INTO THURSDAY NIGHT...ALTHOUGH IT 
STILL APPEARS AS IF ANY ACCUMULATING SNOW SHOULD REMAIN NORTH OF THE 
FA.  
A TRANSITION TO MORE NORTHERN STREAM DOMINANCE CAN BE EXPECTED 
FRIDAY INTO THE WEEKEND AS THE AFOREMENTIONED NORTHERN STREAM 
SHORTWAVE PIVOTS THROUGH THE GREAT LAKES. PERTURBATIONS IN THE 
RESULTING WNW FLOW ALOFT MAY SUPPORT SOME LIGHT PCPN BY FRIDAY OR 
SATURDAY WITH LES NOT OUT OF THE QUESTION GIVEN LOW LVL CAA. WILL 
CONTINUE WITH TEMPS NEAR NORMAL AND MAINLY DRY CONDITIONS AS TRYING 
TO TIME/TRACK ANY LOW AMPLITUDE NRN STREAM WAVES THIS FAR IN ADVANCE 
A LOST CAUSE. OTHERWISE...MEDIUM RANGE MODELS CONTINUE TO HINT AT 
THE NEXT GOOD CHANCE FOR PCPN (PROBABLY RAIN) BEING EARLY NEXT WEEK 
AS THE NEXT SOUTHERN STREAM WAVE EJECTS OUT OF THE ROCKIES. 
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...NONE.
&&
$$
SHORT TERM...MURPHY
LONG TERM...STEINWEDEL
UPDATE...JT
AVIATION...FISHER