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000
FXUS63 KIWX 020918
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
418 AM EST MON MAR 2 2015

.SYNOPSIS...
ISSUED AT 415 AM EST MON MAR 2 2015

SKIES WILL BECOME PARTLY CLOUDY TODAY FOLLOWED BY INCREASING
CLOUDINESS LATE THIS AFTERNOON. HIGHS TODAY WILL RANGE FROM 25 TO
30. SKIES WILL BECOME CLOUDY TONIGHT...WITH STEADY OR SLOWLY
RISING TEMPERATURES. A MIX OF PRECIPITATION WILL SPREAD NORTH LATE
TONIGHT AND TUESDAY...STARTING AS SNOW. THERE WILLL BE A
TRANSITION TO SLEET AND FREEZING RAIN...AND THEN TO JUST RAIN WITH
HIGHS MAINL IN THE 30S.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 410 AM EST MON MAR 2 2015

AN UPPER LEVEL TROF WAS MOVING ACROSS THE REGION EARLY THIS MORNING.
AN AREA OF CLOUDS ASSOCIATED WITH THIS SYSTEM WILL MOVE EAST OUT OF
THE WESTERN GREAT LAKES REGION BEFORE DAYBREAK. MUCH COLDER AIR WILL
BRIEFLY RETURN TO THE AREA TODAY...KEEPING TEMPERATURES 10 TO 15
DEGREES BELOW NORMAL. WENT A FEW TO SEVERAL DEGREES ABOVE NAM/MET
GFS/MAV AND THE EC GUIDANCE. GIVEN RECENT INTRUSIONS OF ARCTIC AIR
WITH CLEAR/PARTLY CLOUDY SKIES...GUIDANCE HIGH TEMPERATURES HAVE
BEEN TOO COOL LATELY WITH THE LATE FEBRUARY AND EARLY MARCH SUN. FOR
TONIGHT... MOISTURE AND ISENTROPIC LIFT INCREASE RAPIDLY...WITH
PRECIPITATION LIKELY BEFORE DAYBREAK. FAVOR THE 12KM NAM AND ECMWF
THAT HAVE BEEN HANDLING THIS SYSTEM REASONABLY WELL. A MASSIVE LOWER
LEVEL DRY LAYER WILL TAKE A LITTLE WHILE TO SATURATE. HOWEVER...LOW
LEVEL FLOW WILL HAVE LITTLE IF ANY DRY AIR ENTRAINMENT. REMOVED
CHANCES FOR FREEZING RAIN ALL BUT THE FAR SOUTHWEST AFTER 6 AM.
PROFILES SUPPORT JUST SNOW THROUGH THE NIGHT WITH GROUND
TEMPERATURES WELL BELOW FREEZING.

&&

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 410 AM EST MON MAR 2 2015

FORECAST STILL FOCUSED ON NEXT STORM SYSTEM FOR TUESDAY. MODELS
CONTINUE TO HONE IN ON IMPORTANT THERMODYNAMIC DETAILS BUT STILL
SOME DIFFERENCES AS TO BE EXPECTED WITH SUCH A COMPLICATED SCENARIO.
DIFFERENCE OF JUST A DEGREE OR TWO FROM SURFACE THROUGH 1-2KFT WILL
MAKE A SIGNIFICANT DIFFERENCE ON PCPN TYPE AND AMOUNT OF SNOW OR ICE
ACCUMULATION. GENERALLY FOLLOWED THE NAM12 AND 00Z ECMWF WITH WHAT
APPEARS TO BE BETTER RESOLUTION OF LOW LEVEL THERMAL DETAILS. GFS
SEEMS TOO QUICK AND TOO WARM WITH NEAR SURFACE TEMPS. IT STILL
APPEARS THAT A WINTER WEATHER ADVISORY WILL BE NEEDED FOR AT LEAST
TUE MORNING GIVEN MIXED PCPN WITH MAIN IMPACTS COMING FROM THE LIGHT
ICE ACCUMULATIONS. AFTER COLLABORATION WITH NEIGHBORING OFFICES
OPTED TO HOLD OFF ON HEADLINES AND DEFER WITH QUESTIONS REMAINING ON
TIMING OF CHANGEOVER AND DURATION.

SNOW WILL LIKELY BE SPREADING ACROSS THE AREA AT BEGINNING OF PERIOD
TUESDAY. SOUNDINGS SHOW A RATHER PRONOUNCED DRY WEDGE LATE MONDAY
NIGHT THAT ERODES QUICKLY AS SUBTROPICAL MOISTURE SURGE...SEEN
NICELY ON WATER VAPOR INTO THE SOUTHWEST CONUS THIS
MORNING...SPREADS ACROSS OUR AREA. LOW LEVEL JET WILL BE INCREASING
ALONG WITH DEVELOPING SYSTEM RELATIVE ISENTROPIC LIFT ACROSS THE
REGION. THIS SHOULD AID PCPN DEVELOPMENT AND EXPANSION ACROSS THE
AREA. MODELS CONTINUE TO BACK OFF ON QPF TOTALS FOR THIS EVENT. IT
APPEARS THAT STRONG JET ENERGY OFF THE CA COAST DIGGING INTO
SOUTHWEST CONUS TROUGH WILL BE STRONG ENOUGH TO LEAVE AN UPPER LOW
IN THAT AREA WHILE PARTIAL ENERGY EJECTS NORTHEAST. PREVIOUS RUNS
WERE BRINGING THIS ENTIRE TROUGH EAST WITH STRONGER FORCING. AN
IMPRESSIVE UPPER LEVEL JET DOES DEVELOP TUESDAY BUT OUR AREA LOOKS
TO BE IN UNFAVORABLE RIGHT FRONT QUAD. THUS PCPN AMOUNTS HAVE BEEN
ON THE WANE WITH THESE MODEL DIFFERENCES. STILL ENOUGH PCPN EXPECTED
TO CAUSE ISSUES TUESDAY AS SNOW TRANSITIONS TO FREEZING RAIN FOR A
FEW HOURS MID MORNING. THIS REMAINS THE TRICKY PART OF FORECAST WITH
QUESTIONS REMAINING ON HOW FAST NEAR SURFACE TEMPS AND ACTUAL
SURFACE TEMPS RISE ABOVE FREEZING. AS MENTIONED PREVIOUSLY...HAVE
USED BLEND OF NAM12 AND ECMWF TO GENERATE THERMAL PROFILES FOR PCPN
TYPE. LATEST FORECAST SIMILAR TO PREVIOUS WITH TRANSITION FROM SOUTH
TO NORTH DURING THE MORNING. NOW HAVE A FEW HOURS OF FZRA AFTER 18Z
ACROSS THE NORTH BEFORE BECOMING ALL RAIN. SNOW ACCUMS GENERALLY 1
TO 2 INCHES WITH HIGHEST AMOUNTS ACROSS MI COUNTIES. ICE ACCUMS
STILL COMING OUT LESS THAN TWO TENTHS OF AN INCH AND REALLY CLOSER
TO ONE TENTH. EXCEPTION IN THE SOUTH WHERE A TENTH OF AN INCH OR
LESS OF ICE EXPECTED WITH FASTER TRANSITION TO RAIN.

COLD FRONT TO MOVE THROUGH TUE NIGHT. MOISTURE LOOKS TO PULL OUT
QUICKLY SO KEPT CHANCE POPS NORTHWEST AND LIKELY TO CATEGORICAL
SOUTHEAST. THIS STILL MAY NEED REFINING IF MOISTURE LINGERS LONGER
IN THE WEST. VERY COLD AIR RETURNS WEDNESDAY AND THURSDAY. HIGHS IN
THE TEENS AND LOWS AROUND ZERO OR SLIGHTLY BELOW ZERO EXPECTED.
BUMPED POPS UP IN THIS PERIOD OVER THE NORTHWEST AS SOME LAKE EFFECT
SNOW SHOWERS POSSIBLE GIVEN DELTA T VALUES RISING INTO THE 20S. DRY
AIR...LOW INVERSION HEIGHTS AND LIMITED AREA OF OPEN WATER ON LAKE
MICHIGAN SHOULD KEEP THIS A MAINLY LIGHT EVENT.

THIS WILL BE A SHORT DURATION COLD SPELL AS TEMPS WILL BEGIN TO
MODERATE BY WEEKEND AND MAKE A RUN TOWARD NORMAL HIGHS FOR EARLY
MARCH. KEPT LATER PERIODS PCPN FREE WITH NO STRONG SIGNALS FOR PCPN
AT THIS TIME.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 154 AM EST MON MAR 2 2015

AN AREA OF CLOUDS ASSOCIATED WITH AN UPPER LEVEL TROF WILL DRIFT
ACROSS THE AREA OVERNIGHT. THE TRAJECTORY INDICATES SBN MAY BECOME
MVFR FOR A FEW HOURS...SO LEFT A TEMPO MVFR GROUP AT SBN.
OTHERWISE...PRECIPITATION FROM THE NEXT SYSTEM WILL HOLD OFF UNTIL
AFTER THE END OF THE TAF PERIOD.


&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...NONE.

&&

$$

SYNOPSIS...SKIPPER
SHORT TERM...SKIPPER
LONG TERM...LASHLEY
AVIATION...SKIPPER


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