Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 220849
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
349 AM EST SAT NOV 22 2014

.SYNOPSIS...
ISSUED AT 342 AM EST SAT NOV 22 2014

THE COMBINATION OF AN UPPER LEVEL DISTURBANCE AND WARMER AIR
MOVING BACK INTO THE REGION WILL RESULT IN LIGHT RAIN AND LIGHT
FREEZING RAIN THIS MORNING. THE THREAT OF FREEZING RAIN WILL COME
TO AN END SHORTLY AFTER DAYBREAK. THERE IS A CONTINUED CHANCE OF
RAIN THIS AFTERNOON...AND RAIN WILL BECOME LIKELY AGAIN TONIGHT.
HIGH TEMPERATURES THIS AFTERNOON WILL REACH INTO THE MID AND UPPER
40S. LOW TEMPERATURES TONIGHT WILL RANGE FROM 40 TO 45.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 342 AM EST SAT NOV 22 2014

A SHORT WINDOW OF FREEZING RAIN POTENTIAL EARLY THIS MORNING ALONG
WITH CONTINUED CHANCES OF RAIN THIS AFTERNOON/NIGHT WILL CONTINUE TO
BE THE PRIMARY SHORT TERM CHALLENGES.

KIWX VAD WIND PROFILE DEPICTS 45-50 KNOT SOUTHWESTERLY WINDS IN
THE 3-5K FT LAYER MARKING STRONG LOW LEVEL WARM/MOISTURE ADVECTION.
IN ADDITION TO BROAD ISENTROPIC FORCING...WATER VAPOR IMAGERY
INDICATES AN UPPER LEVEL SHORT WAVE CENTERED ACROSS NORTHERN
ILLINOIS/SOUTHERN WISCONSIN EARLY THIS MORNING. MOST WIDESPREAD
PRECIP AT 08Z PER REGIONAL RADAR MOSAIC EXTENDS FROM NEAR
MICHIGAN CITY INDIANA TO NORTH OF KOKOMO INDIANA...CORRELATING WELL
TO STRONGEST 900-800 HPA MOISTURE FLUX CONVERGENCE. PRECIP TYPES
WILL BE QUITE TRICKY THIS MORNING DUE TO COMPETING PROCESSES OF
EVAPORATIVE/WET BULB COOLING AND STRONG LOW LEVEL WAA. FOR THE MOST
PART...UPSTREAM LOCATIONS ACROSS ILLINOIS HAVE EXPERIENCED
RELATIVELY LIMITED KNOWN IMPACTS TO THIS POINT AS SFC TEMPERATURES
HAVE RISEN TO AT OR ABOVE FREEZING SHORTLY AFTER PRECIP ONSET.
HOWEVER...HAVE NOTED SOME COOLING CLOUD TOPS ACROSS NORTHEAST
ILLINOIS/NORTHWEST INDIANA OVER THE PAST COUPLE OF HOURS WITH PRECIP
A BIT MORE CONVECTIVE IN NATURE....WHICH POSES SOME CONCERN FOR A
BRIEF PERIOD OF BETTER PRECIP RATES BEFORE PROFILES BECOME
SUPPORTIVE OF MAINLY RAIN. HAVE GONE AHEAD AND ISSUED A FREEZING
RAIN ADVISORY FOR ALL OF THE FORECAST AREA THIS MORNING. WITH TIME
WINDOW STILL LOOKING NARROW FOR FREEZING PRECIP...HAVE CARRIED THE
ADVISORY THROUGH 12Z FOR MOST LOCATIONS...EXCEPT THE FAR NORTHEAST
WHERE HAVE GONE WITH A 14Z EXPIRATION.

BY LATE MORNING...AXIS OF DEEPER MOISTURE SHOULD BEGIN TO SHIFT
EAST/SOUTHEAST OF THE LOCAL AREA WITH CONTINUED BROAD ISENTROPIC
UPGLIDE. WITH DIFFICULTY IN LATCHING ONTO A CLEAR FORCING MECHANISM
THIS AFTERNOON OUTSIDE OF BROAD WARM ADVECTION AND LOSS OF DEEPER
MOISTURE...HAVE TRANSITIONED WEATHER GRIDS TO SCATTERED RAIN
SHOWERS. NAM CONTINUES TO DEPICT RELATIVELY STEEP 700-500 HPA LAPSE
RATES OF 7-8 DEG CELSIUS/KM THROUGH THE AFTERNOON
HOWEVER...PARTICULARLY ACROSS THE NORTHWEST TWO THIRDS OF THE AREA
IN CLOSER PROXIMITY TO LOW LEVEL THERMAL RIDGE AXIS...WHERE HAVE
MAINTAINED THE HIGHEST POPS. DIURNAL RANGES WILL BE LIMITED TODAY
DUE TO EXPANSIVE LOW CLOUD COVER ALTHOUGH STRENGTH OF WAA SHOULD
YIELD HIGHS IN THE MID 40S...TO POSSIBLY UPPER 40S ACROSS THE
SOUTHWEST.

FOR TONIGHT...A MID/UPPER LEVEL TROUGH TRACKING ACROSS THE
SOUTHERN/CENTRAL PLAINS WILL ALLOW FOR BACKING MID LEVEL WINDS AND
SURGE OF DEEPER MOISTURE BACK INTO THE OHIO VALLEY/SOUTHERN GREAT
LAKES WITH INCREASING CHANCES OF RAIN ONCE AGAIN. DID ADD SOME AREAS
OF FOG FOR LOCATIONS WHICH WILL BE EXPERIENCING MELTING SNOWCOVER
TODAY ACROSS EXTREME NORTHERN INDIANA/SOUTHERN LOWER MICHIGAN. LOWS
TONIGHT UNDER THE INFLUENCE OF CLOUDS/PRECIP SHOULD REMAIN AROUND
40/LOWER 40S.

&&

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 342 AM EST SAT NOV 22 2014

A NORTHERN STREAM TROUGH AMPLIFYING INTO THE CENTRAL US WILL HELP
FORCE A POTENT PV ANOMALY (PRESENTLY DIGGING INTO FAR NORTHERN
MEXICO) NORTHEAST THROUGH THE REGION LATER SUNDAY/SUNDAY NIGHT.
PHASING OF THESE FEATURES AND ASSOCIATED DEEP UVM/MOISTURE PLUME
WILL SUPPORT RAPID CYCLOGENESIS...WITH SFC REFLECTION TRACK MODELED
NNE TO SRN LAKE MI SUNDAY NIGHT AND POTENTIALLY SUB-980 MB INTO THE
NRN LAKES MONDAY. SURGE OF DEEPER MOISTURE CONVERGENCE (PWATS
EXCEEDING 1") AND DEEP ASCENT UNDER COUPLED JET STRUCTURE WILL
LIKELY BRING A SOLID 0.60-1.20" OF RAIN TO THE LOCAL AREA LATER
SUNDAY INTO SUNDAY NIGHT. PCPN COVERAGE/INTENSITY DIMINISHES ON
MONDAY...ESPECIALLY SOUTHERN/EASTERN ZONES AS MID LVL DRY SLOT
OVERSPREADS AND WELL PRONOUNCED DEFORMATION AXIS MOST LIKELY SETS UP
NW OF IWX CWA. IF THE STRONGER GFS/GEM SOLUTIONS VERIFY A WIND
ADVISORY MAY BE NEEDED (00Z GFS DEEPENS CYCLONE TO 966 MB NEAR SAULT
STE. MARIE BY 18Z MONDAY...HOPEFULLY OVERDONE). OTHERWISE...EXPECT
FALLING TEMPS IN WAKE OF THE TRAILING COLD FRONT.

COLD/MOIST CYCLONIC FLOW WITHIN DEEP LAYERED EASTERN CONUS TROUGH
AXIS WILL KEEP CLOUDS AND SPORADIC SNOW SHOWERS/FLURRIES AROUND
MONDAY NIGHT INTO TUESDAY...ESPECIALLY NORTHWEST ZONES WHERE SOME
LAKE ENHANCEMENT/LIGHT ACCUMS ARE EXPECTED. THE MID-LATE WEEK PERIOD
WILL BE CHARACTERIZED BY COLD NORTHWEST FLOW AND SEVERAL CHANCES FOR
LIGHT SNOW AS SHORTWAVE ENERGY DIVES DOWN THE BACKSIDE OF MEAN
EASTERN CONUS UPPER TROUGH AND INTERACTS WITH AN EXISTING NRN HIGH
PLAINS TO MID MS VALLEY BAROCLINIC ZONE.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1249 AM EST SAT NOV 22 2014

STRONG LOW LEVEL MOISTURE/THERMAL ADVECTION WILL CONTINUE TO ALLOW
FOR EASTWARD PROGRESSION OF LIGHT PRECIPITATION ACROSS
CENTRAL/SOUTHEAST ILLINOIS THROUGH THE OVERNIGHT HOURS.
THERMAL/MOISTURE PROFILES SHOULD SUPPORT APPROXIMATELY A 3 HOUR
WINDOW FOR FREEZING RAIN AT THE TERMINALS...WITH PRECIP AMOUNTS
DURING THIS PERIOD OF FREEZING RAIN EXPECTED TO TOTAL TO A FEW
HUNDREDTHS OF AN INCH. TIME PERIOD OF GREATEST THREAT OF FREEZING
RAIN APPEARS TO BE FROM 08Z-12Z...WITH PROFILES SUPPORTIVE OF
LIQUID PRECIP TYPE AFTER 12Z. PASSAGE OF WEAK UPPER LEVEL TROUGH
THIS MORNING AND AXIS OF DEEPER MOISTURE SHIFTING EAST OF THE
AREA...SHOULD TEND TO DIMINISH RAIN COVERAGE LATER THIS MORNING
INTO THIS AFTERNOON. SOME VERY WEAK ELEVATED INSTABILITY MAY
SUPPORT SOME SCATTERED LIGHT SHOWERS IN THE AFTERNOON. HAVE
CARRIED PREVAILING RAIN THROUGH MOST OF THIS PERIOD...ALTHOUGH
LATER FORECAST CYCLES MAY BE ABLE TO NARROW THIS
MENTION...ESPECIALLY THIS AFTERNOON. BY TONIGHT...SLUG OF DEEPER
MID LEVEL MOISTURE SHOULD ADVECT BACK NORTHWARD RENEWING RAIN
LIKELIHOOD. MVFR CONDITIONS EXPECTED TO OVERSPREAD TERMINALS
OVERNIGHT AND PERSIST THROUGH MUCH OF THIS FORECAST PERIOD WITH
BEST CHANCE OF CIGS BLO 2K FT AT KSBN.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...FREEZING RAIN ADVISORY UNTIL 7 AM EST /6 AM CST/ THIS MORNING
     FOR INZ003>005-012>018-020-022>027-032>034.

     FREEZING RAIN ADVISORY UNTIL 9 AM EST THIS MORNING FOR
     INZ006>009.

MI...FREEZING RAIN ADVISORY UNTIL 7 AM EST THIS MORNING FOR MIZ077-
     078.

     FREEZING RAIN ADVISORY UNTIL 9 AM EST THIS MORNING FOR
     MIZ079>081.

OH...FREEZING RAIN ADVISORY UNTIL 7 AM EST THIS MORNING FOR OHZ015-
     016-024-025.

     FREEZING RAIN ADVISORY UNTIL 9 AM EST THIS MORNING FOR OHZ001-
     002-004-005.

LM...SMALL CRAFT ADVISORY UNTIL 10 PM EST THIS EVENING FOR LMZ043-046.

&&

$$

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


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