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000
FXUS63 KIWX 071637
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
1137 AM EST SAT DEC 7 2013

.SYNOPSIS...
ISSUED AT 1136 AM EST SAT DEC 7 2013

LAKE EFFECT SNOW SHOWERS AND FLURRIES WILL COME TO AN END THIS
AFTERNOON WITH DECREASING CLOUDINESS. ANOTHER DISTURBANCE WILL
RACE INTO THE REGION LATE THIS WEEKEND...BRINGING A PERIOD OF
LIGHT SNOW SUNDAY AFTERNOON ALONG WITH A POSSIBILITY OF SOME
FREEZING DRIZZLE SUNDAY NIGHT. HIGHS TODAY AND SUNDAY WILL BE IN
THE 20S. LOWS TONIGHT WILL MAINLY BE IN THE TEENS.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 418 AM EST SAT DEC 7 2013

INITIAL LOW INVERSION HEIGHTS WITH A LIMITED FETCH SHOULD HELP KEEP
JUST FLURRIES THIS MORNING...ESPECIALLY GIVEN THE LATEST OBS AND
TRENDS. WILL MAINTAIN SOME LOW END POPS EARLY THIS MORNING ACROSS
FAR NORTHWEST...BUT EXPECTING MOST AREAS WILL NOT SEE MEASURABLE
SNOW. EARLY MORNING TEMPERATURES WERE ALREADY FALLING WELL DOWN
INTO THE TEENS OVER AREAS THAT HAVE CLEARED...BUT HOLDING IN THE
20S UNDER CLOUD COVER. LINGERING CLOUD COVER DOWNSTREAM OF LAKE
MICHIGAN WELL INTO TODAY WITH WEAK COLD AIR ADVECTION SHOULD LIMIT
DIURNAL WARMING. HOWEVER...INCREASING DEEP LAYER SUBSIDENCE SHOULD
HELP SCATTER OUT CLOUDS THIS AFTERNOON AS WINDS BACK A LITTLE MORE
TO THE WEST...TAKING FOCUS FOR ANY ADDITIONAL FLURRIES OR SLIGHT
SNOW SHOWERS CONFINED TO MAINLY SOUTHWEST LOWER MICHIGAN.

&&

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 418 AM EST SAT DEC 7 2013

FORECAST CONCERNS FOR THE LONG TERM REMAIN CENTERED ON PRECIP
CHANCES SUNDAY AFTERNOON/SUNDAY NIGHT...FOLLOWED BY ARCTIC AIR MASS
OVERSPREADING THE AREA FOR THE EARLY PARTS OF NEXT WEEK WHICH WILL
BE ACCOMPANIED BY INCREASING LAKE EFFECT SNOW SHOWER CHANCES.

A COMPACT UPPER LEVEL JET STREAK OFF THE PACIFIC NORTHWEST COAST
THIS MORNING WILL BEGIN TO CARVE OUT A MORE SUBSTANTIAL UPPER TROUGH
ACROSS SOUTHWEST CONUS TODAY...AND THIS FEATURE WILL MERGE FROM THE
LEE OF THE ROCKIES ON SUNDAY. AS THIS OCCURS...AN ABRUPT TRANSITION
TO SOUTHERLY LOW LEVEL FLOW WILL OCCUR SETTING UP FAIRLY STRONG
ISENTROPIC UPGLIDE OVER COLD DOME. NAM/GFS ISENTROPIC PROGS DEPICT A
RAPID REDUCTION OF CONDENSATION PRESSURE DEFICITS ON THE 285K SFC
FROM 12Z-18Z SUNDAY. PREVIOUS INCREASING CHANCE -SN POPS FROM SOUTH
TO NORTH ON SUNDAY STILL APPEAR REASONABLE...ESPECIALLY CONSIDERING
INCREASE IN LARGE SCALE SYNOPTIC SUPPORT WITH COUPLED UPPER JET
STRUCTURE DEVELOPING ACROSS THE SOUTHERN GREAT LAKES. MUCH OF THE
INITIAL LIFT FROM THIS WAA/ISENTROPIC UPGLIDE FORCING WILL BE SPENT
ON TOP DOWN SATURATION PROCESSES WHICH SHOULD LIMIT SNOW
ACCUMULATIONS SUNDAY AFTERNOON TO LESS THAN A HALF INCH ESPECIALLY
CENTRAL/SOUTH. FORECAST CHALLENGE FOR LATER SUNDAY AFTERNOON/SUNDAY
NIGHT WILL BE ON TRICKY PTYPE SETUP WITH MID LEVEL DRY SLOT
ADVECTING INTO THE AREA AS DEEPER MOISTURE TONGUE SHIFTS EAST OF THE
AREA. CONFIDENCE IS BEGINNING TO INCREASE THAT DRY SLOT WILL RESULT
IN LOSS OF ICE INTRODUCTION BY LATE AFTERNOON/EARLY EVENING FROM
SOUTH TO NORTH AND HAVE MAINTAINED TREND OF PREVIOUS FORECASTS IN
FZDZ INTRODUCTION DURING THIS PERIOD. DID HOLD INTO LIKELY
-SN/CHANCE FZDZ MENTION ACROSS THE FAR NORTH WHERE STRONGER DPVA AND
MID/UPPER FORCING MAY ALLOW FOR SUFFICIENT SATURATION DEPTHS TO KEEP
PREDOMINANT PTYPE AS LIGHT SNOW. A QUICK INCH OF SNOW ACCUMULATION
IS POSSIBLE ESPECIALLY ACROSS THE FAR NORTH/NORTHWEST IN SOUTHERN
LOWER MICHIGAN...WITH CONCERN FOR REMAINDER OF THE AREA
TRANSITIONING TO A POSSIBILITY OF LIGHT ICE GLAZING WITH AREAS
OF FZDZ. WILL CONTINUE TO MENTION THIS POSSIBILITY IN THE HWO THIS
MORNING

ANY MIXED PRECIP ISSUES SHOULD COME TO AN END MONDAY AS STRONG LOW
LEVEL CAA ENSUES IN THE WAKE OF THE LOW LEVEL REFLECTION OF THIS
WAVE. THIS WILL MARK THE ONSET OF AN EXTENDED PERIOD OF LAKE EFFECT
SNOW CHANCES WITH PRIMARILY WESTERLY FETCH FOR THE MONDAY-WEDNESDAY
PERIOD...THOUGH POSSIBLY FAVORING MORE WEST-NORTHWEST BY WEDNESDAY.
WHILE CONFIDENCE REMAINS SOMEWHAT LOW IN TIMING SMALLER SCALE WAVES
DROPPING INTO THE AREA AROUND WESTERN PERIPHERY OF POLAR LOW...BULK
OF 00Z MEDIUM RANGE MODEL GUIDANCE STILL SUPPORTS THE TUESDAY-EARLY
WEDNESDAY TIME PERIOD WITH THE PEAK LAKE INDUCED INSTABILITY. STILL
PLENTY OF QUESTIONS TO RESOLVE IN TERMS OF MID LEVEL MOISTURE/DRY
AIR ENTRAINMENT CONCERNS...BUT THERE DOES APPEAR TO BE A GOOD CHANCE
OF ACCUMULATING LAKE EFFECT SNOW DURING THIS PERIOD ACROSS WESTERN
LOWER MICHIGAN. HAVE MAINTAINED MID TO HIGH CHANCE POPS AT THIS TIME
UNTIL CONFIDENCE IN FETCH AND TIMING INDIVIDUAL SHORT WAVES
INCREASES.

AFTERNOON HIGHS SHOULD TOP OUT ONLY AROUND 20 FOR TUESDAY/WEDNESDAY
WITH NIGHTTIME LOWS POSSIBLY DIPPING INTO THE SINGLE DIGITS ABOVE
ZERO AWAY FROM LAKE MICHIGAN DEPENDING ON EXTENT OF BOUNDARY LAYER
MIXING. MOST OF THIS PERIOD SHOULD BE BLUSTERY WITH SOME SUBZERO
WIND CHILLS STILL A POSSIBILITY. BY THURSDAY...MEDIUM RANGE MODELS
STILL TRYING TO DEPICT SOME FLATTENING OF WESTERN CONUS UPPER RIDGE
ALLOWING FOR NORTHWARD RETREAT OF ARCTIC AIR MASS...BUT HAVE OPTED
TO UNDERCUT CR ALLBLEND TEMPS A BIT TOWARD THE END OF THE PERIOD
ESPECIALLY ACROSS THE NORTH WHERE SOME NEW SNOW COVER WILL BE
POSSIBLE ALONG WITH LIKELY LIMITED MIXING DEPTHS WITH ONSET OF LOW
LEVEL WAA.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 532 AM EST SAT DEC 7 2013

A MARGINAL LAKE EFFECT SNOW SHOWER SETUP THIS MORNING WILL BRING
CONTINUED FLURRIES TO KSBN THROUGH THE MORNING. SYNOPTIC SCALE
SUBSIDENCE AND DRY MID LEVEL PROFILES SHOULD KEEP CONDITIONS
MAINLY VFR...ALTHOUGH CLOUD BASES MAY DROP TO HIGHER END MVFR IN
THE 2500-3000 FT RANGE FOR A TIME THIS MORNING. LAKE EFFECT
LOW CLOUDS MAY PERIST INTO THE EVENING AT KSBN BUT EXPECTING
THESE CIGS WOULD BE AT VFR LEVELS. OTHERWISE NORTHWEST WINDS
AROUND 10 KNOTS TODAY SHOULD BECOME LIGHT AND VARIABLE THIS
EVENING AS SFC HIGH PRESSURE BUILDS IN FROM THE WEST.


&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 11 PM EST THIS EVENING FOR LMZ043-046.

&&

$$

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


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