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000
FXUS63 KIWX 061138
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
638 AM EST FRI DEC 6 2013

.SYNOPSIS...
ISSUED AT 635 AM EST FRI DEC 6 2013

ANOTHER UPPER LEVEL DISTURBANCE WILL BRING MORE ACCUMULATING SNOW TO
PORTIONS OF FAR NORTHEAST INDIANA AND NORTHWEST OHIO THROUGH THIS
EVENING. A RIDGE OF HIGH PRESSURE WILL BUILD INTO THE REGION ON
SATURDAY BEHIND THIS SYSTEM. DRY CONDITIONS ARE EXPECTED SATURDAY
AND SATURDAY NIGHT...ALTHOUGH SCATTERED LIGHT LAKE EFFECT SNOW
SHOWERS WILL BE POSSIBLE SATURDAY MORNING. ANOTHER DISTURBANCE WILL
RACE INTO THE REGION LATE THIS WEEKEND...BRINGING A PERIOD OF LIGHT
SNOW SUNDAY EVENING. HIGH TEMPERATURES THIS AFTERNOON WILL REACH
INTO THE MID AND UPPER 20S. LOW TEMPERATURES TONIGHT WILL DROP INTO
THE TEENS.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 508 AM EST FRI DEC 6 2013

A WEAK AREA OF FRONTAL LIFT MAINLY JUST SOUTHEAST OF THE FORECAST
AREA WILL MOVE NORTH AS A WAVE MOVES NORTHEAST ALONG A BOUNDARY.
FAVORED THE HI RES ARW EAST WHICH APPEARS TO BE HANDLING THIS EVENT
REASONABLY WELL AND HAS INCORPORATED THE DRY SUB CLOUD LAYERS THAT
HAVE BEEN HINDERING THE NORTHWARD DEVELOPMENT/SPREAD OF
PRECIPITATION. KEPT THE ONGOING TIMING OF THE WINTER WEATHER
HEADLINES...WITH JUST SNOW EXPECTED. COLD AIR ADVECTION WILL
CONTINUE TODAY...WITH THE THICKNESSES STAYING BELOW THE CRITICAL
RAIN/SNOW LOW AND MID LEVEL THRESHOLDS. ALSO...LATEST DUAL POL
CORRELATION COEFFICIENTS ABOVE 0.99 EVEN TO THE SOUTHEAST OF
LIMA/AOH SUPPORT JUST SNOW. OTHERWISE...LOWERED TEMPS TONIGHT
OVER SOUTHERN AREAS SUPPORTED BY THE GFS...NAM AND EC.

&&

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 508 AM EST FRI DEC 6 2013

MAIN ITEMS OF INTEREST FOR THE LONG TERM PERIOD WITH BE INCREASING
PRECIP CHANCES SUNDAY/SUNDAY NIGHT FOLLOWED BY ARCTIC AIR MASS
OVERSPREADING THE AREA AND INCREASING LAKE EFFECT SNOW CHANCES EARLY
NEXT WEEK.

ANTICYCLONE ASSOCIATED WITH ARCTIC AIR MASS WILL CONTINUE TO BUILD
INTO THE OHIO VALLEY AND SOUTHERN GREAT LAKES ON SATURDAY PROVIDING
DRY CONDITIONS BUT MUCH BELOW NORMAL TEMPERATURES. STRONG SYNOPTIC
SCALE MID LEVEL SUBSIDENCE/DRYING ACROSS THE REGION FOR SATURDAY
STILL LENDING TO LOWER END CONCERN FOR ANY SCATTERED LAKE EFFECT
SNOW SHOWERS. FCST SOUNDINGS STILL DEPICT LAKE INDUCED EQUILIBRIUM
LEVELS OF AROUND 7-8K FT SATURDAY MORNING BUT VERY DRY AIR MASS WILL
BE LIMITING FACTOR AND HAVE MAINTAINED JUST LOW TO MID RANGE CHANCE
POPS...ESPECIALLY IN THE MORNING. OTHERWISE...FEW CHANGES MADE TO
PREVIOUS FORECAST WITH MIXING UP TO AROUND 900 HPA SUPPORTING HIGHS
ONLY IN THE LOWER TO MID 20S.

ANY LINGERING LAKE EFFECT SNOW SHOWERS/FLURRIES TO END LATE SATURDAY
AFTERNOON AS LOW LEVEL ANTICYCLONE SHIFTS EAST OF THE AREA PROVIDING
CONTINUED DRY CONDITIONS ACROSS THE REMAINDER OF THE AREA THROUGH
SATURDAY NIGHT. MEDIUM RANGE MODELS HAVE BEEN CONSISTENT IN
DEPICTING NEXT SIGNIFICANT WESTERN CONUS TROUGH DIGGING ACROSS THE
SOUTHERN ROCKIES SATURDAY NIGHT...EVENTUALLY SETTING UP RENEWED
ISENTROPIC UPGLIDE/POSITIVE LOW LEVEL THETAE ADVECTION ACROSS THE
OHIO VALLEY SUNDAY MORNING/AFTERNOON. INITIAL ISENTROPIC UPGLIDE/WAA
FORCING WILL LIKELY BE SPENT IN TOP DOWN SATURATION PROCESS SUNDAY
MORNING THROUGH EARLY AFTERNOON...WITH BETTER CHANCE OF PRECIP BY
LATE SUNDAY AFTERNOON AND ESPECIALLY SUNDAY NIGHT. LARGE SCALE
SYNOPTIC SUPPORT TO INCREASE BY THIS TIME PERIOD AS COUPLED JET
STRUCTURE SHOULD SETUP ACROSS THE GREAT LAKES REGION...AND AS
MID/UPPER LEVEL TROUGH LIFTS INTO THE MID MS RIVER VALLEY BY SUNDAY
EVENING. IT STILL APPEARS AS THOUGH MAIN LIMITING FACTOR TO SNOW
ACCUMULATIONS SUNDAY NIGHT WILL BE THE FACT THAT DEEPER MOISTURE
TONGUE WILL BE SHIFTING EAST OF THE AREA AS LOW LEVEL WINDS VEER
MORE SOUTHWESTERLY. MID LEVEL DRY SLOT ALSO IS EXPECTED TO RAPIDLY
ADVECT NORTHEASTWARD INTO THE AREA LENDING TO THE POSSIBILITY OF
SOME PATCHY FREEZING DRIZZLE LATER SUNDAY NIGHT. IN ADDITION...A
WEAK ELEVATED WARM LAYER MAY ADVECT ACROSS FAR SOUTHEAST PORTIONS OF
THE AREA SUNDAY EVENING WITH SOME POSSIBILITY OF A BRIEF PERIOD OF
LIGHT SLEET/SNOW MIX. ONLY A VERY BRIEF WINDOW APPEARS TO EXIST WITH
DEEPER MOISTURE PROFILES IN PLACE AND ONSET OF MORE PRONOUNCED
MID/UPPER LEVEL FORCING SUNDAY EVENING BEFORE DRY SLOT ADVECTS INTO
THE AREA. WOULD SUSPECT THIS WOULD KEEP SNOW ACCUMULATIONS GENERALLY
ON THE ORDER OF AN INCH OR SO...AND ESPECIALLY ACROSS NORTHERN THIRD
WHICH SHOULD BE IN CLOSER PROXIMITY TO STRONGER MID LEVEL
FORCING...AND WHERE EFFECTS FROM DRYING MID LEVELS WILL BE DELAYED
UNTIL LATE NIGHT.

MEDIUM RANGE MODELS REMAIN IN EXCELLENT AGREEMENT THROUGH TUESDAY
WITH NEXT NORTHERN STREAM SHORT WAVE ROTATING AROUND WESTERN
PERIPHERY OF POLAR LOW...ALLOWING FOR SOUTHWARD ADVECTION OF ARCTIC
AIR MASS THAT WILL AFFECT THE REGION FOR THE EARLY TO MIDDLE
PORTIONS OF NEXT WEEK. LAKE EFFECT SNOW SHOWER CHANCES WILL INCREASE
THROUGH THIS PERIOD WITH BEST CHANCES OF ACCUMULATING LAKE EFFECT
SNOW ACROSS WESTERN LOWER MICHIGAN GIVEN INITIAL WESTERLY
FETCH...ALTHOUGH MORE VEERED NORTHWESTERLY TRAJECTORIES MAY BECOME
FAVORED TOWARD THE END OF THE PERIOD. PLENTY OF UNCERTAINTY AT THIS
FORECAST DISTANCE...BUT IT APPEARS AS THOUGH WINDOW OF GREATEST LAKE
INDUCED INSTABILITY MAY EXIST FROM THE LATE TUESDAY/EARLY WEDNESDAY
TIMEFRAME. OUTSIDE OF LAKE EFFECT SNOW CHANCES...CANNOT DISCOUNT
PERIODS OF SNOW SHOWER CHANCES IN THE TUE-THU TIMEFRAME WITH WEAK
CLIPPER TYPE SYSTEMS POISED TO DROP INTO THE REGION. WHILE THESE
CLIPPER SYSTEMS WILL LIKELY HAVE A STRONG BAROCLINIC ZONE TO WORK
WITH...WILL OMIT SYNOPTIC POPS AT THIS TIME GIVEN MEAGER MOISTURE
PROFILES. BY DAY 7/8...DETERMINISTIC AND ENSEMBLE SOLUTIONS SUPPORT
UPPER FLOW DEAMPLIFICATION AND NORTHWARD RETREAT OF ARCTIC AIR MASS
PROVIDING MODERATION JUST BEYOND THIS FORECAST VALID PERIOD.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 635 AM EST FRI DEC 6 2013

PRIMARY QUESTION FOR THIS FORECAST WILL BE NORTHWARD EXTENT OF LIGHT
SNOW IN ASSOCIATION WITH ANOTHER SHORT WAVE EXPECTED TO LIFT
NORTHEAST OUT OF THE SOUTHERN PLAINS THIS AFTERNOON. MID/UPPER LEVEL
FRONTOGENESIS WILL INCREASE ACROSS NORTHERN INDIANA THIS AFTERNOON
AS THIS WAVE APPROACHES...WHICH SHOULD ALLOW FOR NORTHWARD EXTENT OF
LIGHT SNOW TO REACH AS FAR NORTH AS KFWA DURING THE MID TO LATE
AFTERNOON HOURS. SOME LIGHT ACCUMULATIONS OF GENERALLY LESS THAN AN
INCH ARE POSSIBLE AT KFWA FROM 20Z-02Z. HOWEVER...GIVEN RELATIVELY
LOW CONFIDENCE IN EXACTLY WHERE THIS ELEVATED FRONTOGENESIS AXIS
SETS UP LATER TODAY AND SHARP NORTHWARD EDGE TO -SN...WILL HOLD OFF
ON IFR CONDS AT KFWA AT THIS TIME. OTHERWISE...MVFR CIGS OF 2-3K FT
ARE EXPECTED TO PERSIST FOR MOST OF THE DAY AT KSBN. MVFR CIGS MAY
PERSIST INTO TONIGHT AT KSBN GIVEN LAKE MICHIGAN INFLUENCE/LAKE
EFFECT CLOUDS.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...WINTER WEATHER ADVISORY UNTIL 8 PM EST THIS EVENING FOR INZ026-
     027-032>034.

MI...NONE.
OH...WINTER WEATHER ADVISORY UNTIL 8 PM EST THIS EVENING FOR OHZ016-
     024-025.

LM...SMALL CRAFT ADVISORY UNTIL 11 PM EST SATURDAY FOR LMZ043-046.

&&

$$

SYNOPSIS...MARSILI
SHORT TERM...SKIPPER
LONG TERM...MARSILI
AVIATION...MARSILI/SKIPPER


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