Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 252341
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
741 PM EDT WED MAR 25 2015

.SYNOPSIS...
ISSUED AT 735 PM EDT WED MAR 25 2015

LOW PRESSURE WILL MOVE THROUGH THE OHIO VALLEY TONIGHT AND WILL
BRING RAIN TO ALL BUT FAR NORTHERN PORTIONS OF INDIANA AND LOWER
MICHIGAN. THE RAIN COULD MIX WITH SNOW TOWARD DAYBREAK WITH SOME
LIGHT ACCUMULATIONS POSSIBLE OVER NORTHEAST INDIANA AND NORTHWEST
OHIO. LOW TEMPERATURES TONIGHT WILL GENERALLY BE IN THE 30S. HIGHS
ON THURSDAY WILL ONLY BE IN THE LOWER TO MIDDLE 40S WITH MOSTLY
CLOUDY SKIES.

&&

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 331 PM EDT WED MAR 25 2015

MAIN FOCUS IS ON TIMING/AMOUNTS/PTYPE OF PCPN THROUGH THE AREA
TONIGHT INTO THURSDAY MORNING AS A FRONTAL WAVE TRACKS NE THROUGH
THE OH VALLEY...

TEMPS HAVE UNDERPERFORMED TODAY THANKS TO LOW STRATUS THAT HAS
REMAINED LOCKED IN UNDER BRIEF DRYING/SUBSIDENCE ALOFT. THIS
COOLER BOUNDARY LAYER PROFILE SHOULD ALLOW RAIN TO MIX OR CHANGE
OVER TO SNOW LATER TONIGHT/THU AM...QUESTIONS ARE WHEN/WHERE/HOW
MUCH. SYNOPTICALLY...PHASING/APPROACH OF SHORTWAVE ENERGY DROPPING
SE FROM THE UPPER MIDWEST AND A SEPARATE PV ANOMALY EMERGING INTO
THE CENTRAL PLAINS WILL HELP REORIENT ISOTHERMS ALONG THE
DEFORMATION AXIS...AND THEREFORE TIGHTEN/DEEPEN THE LOW-MID LEVEL
FRONTOGENETICAL RESPONSE INTO OH/IN LATER TONIGHT INTO THURSDAY
MORNING. THIS TIGHTENING OF THE THERMAL FIELD WILL NO DOUBT
STRENGTHEN A GREAT LAKES UPPER JET STREAK...WITH THE LOCAL AREA
PLACED IN THE RIGHT ENTRANCE REGION OF THIS FEATURE BY THIS TIME.
MODELS AGREE FOR THE MOST PART ON ALL BUT FAR NW ZONES GETTING
INTO THE 750-600 MB PORTION OF THE FRONTAL CIRCULATION...WITH
MOISTURE (PER 3-4 G/KG PUSH ON 290K CHARTS) APPEARING SUFFICIENT
FOR A DECENT BURST OF PCPN. THERE WILL BE A SHARP CUT OFF ON THE
NW FRINGE WHICH UNFORTUNATELY LOOKS TO BE OVER OR JUST SE OF THE
SOUTH BEND/ELKHART AREA MAKING FOR A LOW CONFIDENCE POP/QPF
FORECAST HERE. LOOKS LIKE A SLAM DRUNK ACROSS SOUTHERN/EASTERN
ZONES WHERE CATEGORICAL POPS AND QPF AMOUNTS UP TO NEAR A HALF
INCH WERE RETAINED (ALTHOUGH CONVECTION INTO THE WESTERN OH VALLEY
COULD LIMIT NWD TRANSPORT OF MOISTURE AND AMOUNTS A BIT)

AS FOR PTYPE...PCPN WILL BEGIN AS RAIN ALONG THE INITIAL/NARROW FGEN
BAND INTO CENTRAL PORTIONS OF THE AREA LATER THIS EVENING/EARLY
OVERNIGHT...THEN LIKELY MIX WITH OR CHANGE TO A BRIEF PERIOD OF SNOW
LATER TONIGHT/THU AM AS DEEPER LIFT/COOLING WORKS IN. MODELED WET
BULB TEMPERATURES IN THE LOWEST 2KFT FEET MARGINAL FOR RAIN OR SNOW
MAKING FOR A DIFFICULT PTYPE FCST (OPTED FOR MIX WORDING AS A
RESULT). ALSO ADDED IN SOME LIGHT ACCUMS (LOW CONFIDENCE
...DUSTING-1") ALONG/SE OF A MONTICELLO-WARSAW-HILLSDALE
LINE...ALTHOUGH WPC 1-3" AMOUNTS POSSIBLE IF A QUICKER/FULL
CHANGEOVER OCCURS. COOL/DRY OTHERWISE IN WAKE OF THIS SYSTEM INTO
THURSDAY AFTERNOON.

&&

.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 331 PM EDT WED MAR 25 2015

VIGOROUS LL CAA WING TO SWEEP SOUTH TO START THE PD THU NIGHT IN
ASSOCD/W AMPLIFYING SECONDARY TROUGH ACRS THE LAKES. AGAIN
UNSEASONABLY COLD TEMPS EXPECTED FRI-SAT BFR MODERATING BACK TWD
NORMAL EARLY NXT WEEK AS PATTN ALOFT FLATTENS AND SOME ASSEMBLANCE
OF TROUGHING DVLPS OUT ACRS THE NRN ROCKIES. HWVR PROGRESSION OF A
SERIES OF SRN STREAM SW TROUGH THEREAFTER IS MIRED IN UNCERTAINTY
GIVEN CONFLICTING MED RANGE SOLUTIONS ALOFT AND WILL HOLD SHY OF
BUCKING AGAIN GOING DRY FCST YET.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z THURSDAY EVENING)
ISSUED AT 732 PM EDT WED MAR 25 2015

SOME BREAKS IN MVFR CLOUD DECK HAD DEVELOPED BUT WEST TO SOUTHWEST
LOW LEVEL FLOW THIS EVENING WAS HELPING UPSTREAM CIGS MOVE BACK
ACROSS THE TAF SITES. FLOW WILL VEER THIS EVENING AND COULD SEE
LOW CLOUDS MOVE JUST SOUTHEAST OF KSBN OVERNIGHT. HOWEVER...RAIN
WILL BE SPREADING NORTHEAST TOWARD KFWA AND THIS MAY HELP LOCK
CLOUDS IN. DIFFICULT FORECAST WITH RESPECT TO CIGS AT KSBN BUT
TRIED TO TREND CIGS UPWARD INTO THURSDAY MORNING. RAIN WILL BRING
IFR CIGS AND VIS TO KFWA OVERNIGHT INTO THURSDAY MORNING. A BRIEF
PERIOD OF SNOW REMAINS POSSIBLE ALONG BACK EDGE OF PCPN SHIELD.
TIMING BETWEEN ARRIVAL OF COLDER AIR AND EXIT OF PCPN WILL BE
CRITICAL IN DETERMINING IF IT REMAINS JUST A MIX OR CHANGES OVER
TO ALL SNOW AT KFWA. PCPN ENDS BY MID MORNING WITH MVFR CIGS
HOLDING ON INTO AFTERNOON.

&&

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

$$

SYNOPSIS...LASHLEY
SHORT TERM...STEINWEDEL
LONG TERM...T
AVIATION...LASHLEY


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