Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 251732
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
1232 PM EST THU DEC 25 2014

.SYNOPSIS...
ISSUED AT 1221 PM EST THU DEC 25 2014

CLOUDY SKIES EARLY THIS AFTERNOON WILL GIVE WAY TO CLEARING SKIES
BY EARLY THIS EVENING ACROSS THE AREA. LOWS OVERNIGHT WILL BE IN
THE LOWER 30S. DRY CONDITIONS ARE EXPECTED THROUGH THE DAY ON
FRIDAY...WITH HIGH TEMPERATURES IN THE MID 40S UNDER PARTLY CLOUDY
SKIES. RAIN CHANCES RETURN TO THE AREA FRIDAY NIGHT INTO SATURDAY.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 317 AM EST THU DEC 25 2014

QUIET/DRIER WX ON TAP TODAY INTO TONIGHT AS MID LEVEL RIDGING
OVERSPREADS IN WAKE OF DEEP CYCLONE LIFTING NORTH THROUGH WESTERN
QUEBEC. AMPLE LEFTOVER LOW LEVEL MOISTURE WITHIN STRENGTHENING
SUBSIDENCE INVERSION SHOULD KEEP BKN-OVC LOW CLOUDS LOCKED IN FOR
MUCH OF THE MORNING AND EARLY AFTERNOON...WITH ANY LINGERING SCT
FLURRIES/PATCHY DRIZZLE LIFTING OUT OF THE AREA FROM SW TO NE
EARLY THIS MORNING. OTHERWISE...MILD FOR LATE DECEMBER WITH WARM
ADVECTION/SW FLOW QUICK TO KICK BACK IN LATER TODAY-TONIGHT IN
ADVANCE OF NEXT SHORTWAVE DROPPING INTO THE FOUR CORNERS.

&&

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 317 AM EST THU DEC 25 2014

BROAD SOUTHWESTERLY LOW LEVEL FLOW AND RELATIVELY MILD CONDITIONS TO
BEGIN THE PERIOD AS LOCAL AREA BECOMES POSITIONED IN UPPER LEVEL
INFLECTION ZONE DOWNSTREAM OF SOUTHWEST CONUS LONGWAVE TROUGH.
FRIDAY IS SHAPING UP AS A RELATIVELY MILD DAY DUE TO POSITIONING OF
BROAD LOW LEVEL THERMAL RIDGING ACROSS THE REGION...AND POTENTIAL OF
AT LEAST SOME INSOLATION. LOW LEVEL THETAE ADVECTION SHOULD RAMP UP
LATER IN AFTERNOON AND ESPECIALLY BY FRIDAY NIGHT WITH EXPECTATION
THAT LOW STRATUS SHOULD TEND TO FILL IN ACROSS THE AREA FRIDAY
NIGHT. DEPENDING ON THIS LOW CLOUD EVOLUTION...HIGHS COULD PUSH INTO
THE UPPER 40S FRIDAY ACROSS THE SOUTH...BUT HAVE NOT STRAYED FAR
FROM INHERITED LOW TO MID 40S HIGHS AT THIS TIME. PRECIP CHANCES
APPEAR TO BE QUITE LOW DURING THE EVENING FRIDAY AS STRONGER UPPER
FORCING REMAINS WEST/SOUTHWEST OF THE AREA AND MOISTURE OF
ANY NOTE REMAINS QUITE SHALLOW. MOISTURE DEPTH SHOULD INCREASE SOME
LATE FRIDAY NIGHT AS AXIS OF STRONGER LOW LEVEL THETAE ADVECTION
SHIFTS NORTHEASTWARD...AND HAVE MAINTAINED SOME LOW CHANCE LIGHT
RAIN POPS IN THE 06Z-12Z PERIOD WHICH MAY END UP TO BE MORE OF A
PATCHY DRIZZLE SCENARIO.

BY SATURDAY...CHANNELED VORTICITY MAXIMUM EMANATING FROM SHEARING
UPPER LEVEL WAVE ACROSS THE ROCKIES SHOULD ALLOW FOR INCREASED
PRECIP CHANCES...ALONG WITH A POTENTIAL OF AT LEAST A BRIEF PERIOD
OF DEEPER MOISTURE PROFILES IN THE VICINITY OF ASSOCIATED LOW/MID
LEVEL TROUGH AXIS. A BIT CONCERNED THOUGH THAT MOISTURE DEPTH MAY
CONTINUE TO BE IN ISSUE INTO SATURDAY...AND MUCH OF THIS WILL DEPEND
ON EXACT STRENGTH OF SOUTHERN/CENTRAL ROCKIES PV ANOMALY AS IT GETS
INGESTED INTO THE MID MS VALLEY. HAVE GENERALLY TAKEN A BLENDED
APPROACH BETWEEN THE STRONGER GEM/EC AND WEAKER GFS IN HANDLING
NORTHEASTWARD EJECTION OF THIS TROUGH...AND THIS BLENDED APPROACH
FITS WELL INTO PREVIOUSLY FORECASTED MID TO HIGH CHANCE -RA POPS FOR
SATURDAY. THE INCREASINGLY SHEARED NATURE TO UPPER WAVE MAY ALLOW
FOR ENOUGH LOW/MID LEVEL FRONTOGENESIS TO PERSIST LONG FOR A BRIEF
PERIOD OF SOME SNOW TOWARD ENDING OF PRECIP SATURDAY EVENING...BUT
STILL EXPECTING LITTLE OR NO ACCUMULATION IF THIS SCENARIO WERE TO
UNFOLD.

FOR MONDAY...MEDIUM RANGE MODELS STILL DEPICT 1050+ MB SFC HIGH
OVERSPREADING NORTHERN PLAINS IN WAKE OF SOUTH CENTRAL CANADIAN
UPPER LOW...WITH A TREND TO COLDER CONDITIONS FOR THE EARLY PARTS OF
NEXT WEEK. GUIDANCE HAS BACKED OFF ON MAGNITUDE OF COLD AIR FOR THIS
PERIOD HOWEVER...WITH ACTUALLY REASONABLE AGREEMENT IN 00Z EC/GFS IN
TRENDING TO MORE OF SOUTHWEST CONUS CUT-OFF UPPER TROUGH. OUTSIDE OF
POTENTIAL LAKE EFFECT SNOW SHOWERS EARLY NEXT WEEK...HAVE MAINTAINED
DRY FORECAST WITH EXPECTATION THAT STRONG LOW LEVEL ANTICYCLONE
SHOULD TEND TO SUPPRESS ANY SHORT WAVES KICKING OUT OF SOUTHWEST
CONUS CUT-OFF TROUGH. A FEW WEAK PERTURBATIONS IN NORTHWEST UPPER
FLOW IN A MORE MOISTURE STARVED NORTHERN STREAM COULD ALLOW FOR A
FEW PERIODS OF LIGHT SNOW/FLURRIES GIVEN EXPECTED STRONG
BAROCLINICITY ACROSS THE REGION...BUT NOTHING THAT APPEARS WORTH A
MENTION AT THIS TIME. PRECIP CHANCES MAY EVENTUALLY INCREASE JUST
OUTSIDE OF THIS FORECAST PERIOD AS CUT OFF UPPER TROUGH EVENTUALLY
GETS INGESTED BACK INTO MAIN BELT OF WESTERLIES BUT CONFIDENCE AT
THIS FORECAST DISTANCE OBVIOUSLY QUITE LOW.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1221 PM EST THU DEC 25 2014

MVFR CIGS WILL CONTINUE OVER THE NEXT FEW HOURS WITH MOIST LAYER
UNDERNEATH A SUBSIDENCE INVERSION. BACK EDGE OF LOW CLOUDS NOTED
NEAR IN/IL BORDER...AND IS EXPECTED TO PUSH THROUGH TERMINALS
AROUND THE 21Z TIME FRAME. VFR CONDITIONS EXPECTED FOR THE REST OF
THE PERIOD AS SFC RIDGING BUILDS ACROSS THE REGION. LOW LEVEL JET
WEST OF THE REGION TONIGHT WILL NOSE INTO THE AREA AROUND
09Z...WITH LOW LEVEL WIND SHEAR POSSIBLE...HOWEVER HELD OFF ON
LLWS MENTION IN THE TAF FOR THIS ISSUANCE GIVEN WEAKENING NATURE
OF THE JET.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 10 PM EST THIS EVENING FOR LMZ043.

     SMALL CRAFT ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR LMZ046.

&&

$$

SYNOPSIS...NG
SHORT TERM...STEINWEDEL
LONG TERM...MARSILI
AVIATION...NG


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