Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 270548
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
1248 AM EST TUE JAN 27 2015

.SYNOPSIS...
ISSUED AT 1240 AM EST TUE JAN 27 2015

SOME VERY LIGHT SNOW OR FREEZING DRIZZLE WILL BE POSSIBLE EARLY
THIS MORNING ACROSS FAR WESTERN AND NORTHWESTERN INDIANA AS WELL
AS ILLINOIS. PRECIPITATION IS EXPECTED TO DIMINISH TOWARD SUNRISE.
LOWS TONIGHT WILL RANGE FROM SINGLE DIGITS OVER CENTRAL AND
NORTHWEST OHIO TO THE MIDDLE 20S OVER PARTS OF INDIANA AND
ILLINOIS. HIGHS ON WEDNESDAY WILL BE IN THE UPPER 20S AND 30S WITH
PARTLY TO MOSTLY CLOUDY SKIES.

&&

.UPDATE...
ISSUED AT 951 PM EST MON JAN 26 2015

NR TERM EXPANSION OF -SN/FZDZ ACRS NE IL AND PLETHORA OF ACCIDENT
REPORTS HAS PROMPTED THE ISSUANCE OF A WINTER WX ADVISORY ACRS
FAR SW INCLUDING WHITE AND PULASKI COUNTIES. CONTD LWRG OF CIG
HGTS AND NARROWING SFC TD DEPRESSIONS OVR NW IN SUGGESTS SFC
PRECIP IMMINENT FAR SW ALG LL BAROCLINIC ZONE. WHILE SIG ICING NOT
XPCD SHRT TERM HIGHRES GUIDANCE SUGGESTING UPWARD OF .05 INCH
LIQUID EQUIVALENT PSBL W/MUCH OF THAT IN FORM OF FZDZ. THUS GIVEN
TIMING AND SFC TEMPS IN THE MID/UPR 20S GLAZING LIKELY.

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 325 PM EST MON JAN 26 2015

AREA OF SHEARED CYCLONIC VORTICITY EMBEDDED WITHIN THE LEFT EXIT
REGION OF A 140 KT 3H JET WILL CONTINUE TO DROP INTO THE MID
MS/WESTERN OH VALLEYS THIS EVENING INTO THE EARLY OVERNIGHT. A
NARROW BAND OF -SN ORIENTED NW TO SE ACROSS WI-IL (AS OF 20Z) ALONG
THE ASSOCIATED FGEN INDUCED CIRCULATION/TIGHTENING THERMAL GRADIENT
MAY CLIP OUR FAR WSW WITH A LIGHT COATING OF SNOW DURING THIS TIME.
LIMITING FACTOR FOR ANYTHING MORE THAN A MID CHC POP HERE WILL BE A
PRONOUNCED LOW LEVEL DRY WEDGE WITH MUCH BETTER CHANCES JUST WEST OF
THE IWX CWA. DRY OUTSIDE OF A FEW FLURRIES OTHERWISE TONIGHT.

STRONG SUBSIDENCE/RAPID HEIGHT RISES WITH WEAK CONVERGENCE/PCPN
SETTLING WELL SOUTH SHOULD ENSURE A DRY TUESDAY AS WESTERN/CENTRAL
LAKES LOW LEVEL RIDGING BECOMES RE-ESTABLISHED. CLOUD COVER REMAINS
THE MAIN UNCERTAINTY WITH SIG MID LVL DRYING HOPEFULLY ALLOWING FOR A
N-S CLEARING TREND. WILL TREND TOWARD PARTLY CLOUDY WORDING FOR NOW
IN HOPE THAT BOUNDARY LAYER STRATOCU THINS/BREAKS UP.
OTHERWISE...ONLY MINOR TWEAKS MADE TO TEMPS.

&&

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 421 PM EST MON JAN 26 2015

SFC HIGH EXPECTED TO MOVE ACROSS THE CWA TUE NGT. STRONG RADIATIONAL
COOLING WITH NEARLY CLEAR SKIES/LIGHT WINDS/SNOW COVER SHOULD
COMPENSATE FOR WK WAA ON BACKSIDE OF SFC HIGH AND UPR RIDGE BUILDING
IN... LOWERED GOING FCST MINS A FEW DEGREES TO RANGE FROM UPR TEENS
WEST... TO UPR SINGLE DIGITS EAST WHERE LESS CLOUDS/MORE SNOW COVER
EXPECTED. BETTER RESPONSE TO WAA EXPECTED WED AS LOW PRESSURE MOVES
EAST FROM THE CENTRAL PLAINS INCREASING MIXING.... HIGHS FCST TO
RANGE FROM THE U20S EAST TO THE M30S WEST.

SHRTWV APCHG PAC NW/SW CANADA TODAY KICKING OUT CUT-OFF LOW WEST OF
BAJA. THESE TWO SYSTEMS EXPECTED TO PHASE OVER THE MIDWEST THU. TOP
DOWN SATURATION EXPECTED IN OUR AREA WED NGT AS THIS SYSTEM
APPROACHES. WARM LAYER ALOFT SHOULD RESULT IN LIQUID PRECIP BUT
EVAPORATIONAL COOLING MAY KEEP PRECIP PREDOMINANTLY SNOW IN PORTIONS
OF THE AREA... MAINLY NORTH. A PERIOD OF FREEZING RAIN ALSO PSBL.

FOR THE REST OF THE PERIOD...ANOTHER STRONG NORTHERN STREAM SYSTEM
WILL DROP SOUTH INTO THE MAIN LONGWAVE TROF OVER CENTRAL NORTH
AMERICA. GIVEN THE SUPERIOR ECMWF HANDLING WITH THE PAST SYSTEM...HAVE
REJECTED THE GFS/MOS HEAVY SNOW SUNDAY. KEPT A CHANCE FOR SNOW
SATURDAY NIGHT AND SUNDAY...HOWEVER...CONFIDENCE IS LOW WITH THIS
SYSTEM.  OTHERWISE...TEMPERATURES WILL BE MUCH BELOW NORMAL FRIDAY
THROUGH TUESDAY AS NORTHWEST FLOW ALOFT CONTINUES WITH CROSS POLAR
FLOW. CONCERN FOR BITTERLY COLD AIR REACHING THE FORECAST AREA AGAIN
WITH ECMWF 850 MB TEMPS NEAR -40C OVER HUDSON BAY SATURDAY.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1237 AM EST TUE JAN 27 2015

ANOTHER TRICKY AVIATION FORECAST WITH RESPECT TO CLOUD HEIGHTS
THIS PERIOD. TERMINALS REMAIN VFR AT ISSUANCE BUT MVFR AND IFR
CONDITIONS EXISTS JUST WEST OF KSBN. KMCY AND KOXI HAVE DROPPED
TO 25HFT WHILE KVPZ DOWN TO 1KFT WITH SOME LIGHT SNOW AT TIMES.
LOW LEVEL FLOW BEING SHOWN BY HIRES GUIDANCE TO SLOWLY TURN
NORTHEAST AND INCREASE SLIGHTLY TO AROUND 5-8 KNOTS NEXT FEW
HOURS. THIS SHOULD SLOW OR END THE EASTWARD EXPANSION OF MVFR CIGS
AND EVENTUALLY PUSH THEM SOUTHWEST. HOWEVER...WITH PROXIMITY TO
KSBN HAD TO ADD A FEW HOURS OF TEMPO MVFR TO ACCOUNT FOR
POSSIBILITY OF THESE CLOUDS. NORTHEAST FLOW SHOULD EVENTUALLY
ALLOW SLIGHTLY DRIER LOW LEVEL AIR TO WORK WEST WITH VFR
CONDITIONS INTO TUESDAY. NEXT CONCERN IS LOW LEVEL CLOUDS OVER
CENTRAL OHIO MAKING A RUN WEST AS THIS LOW LEVEL FLOW CHANGES. RUC
MODEL BRINGS HIGHER RH INTO KFWA TUESDAY MORNING. HAVE INTRODUCED
A SCATTERED DECK AT 25HFT FOR NOW BUT THIS WILL BE MONITORED FOR
POSSIBLE ADDITION OF MVFR CIGS TO LATER FORECASTS.


&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...FREEZING RAIN ADVISORY UNTIL 6 AM EST EARLY THIS MORNING FOR
     INZ013-020.

MI...NONE.
OH...NONE.
LM...NONE.
&&

$$

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


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