Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 262121
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
421 PM EST MON JAN 26 2015

.SYNOPSIS...
ISSUED AT 355 AM EST MON JAN 26 2015

WEAK HIGH PRESSURE WILL BE ACROSS THE AREA TODAY. CLOUDS ARE
EXPECTED TO INCREASE THIS AFTERNOON AND TONIGHT. THERE IS A
CHANCE FOR VERY LIGHT SNOW ACROSS NORTHEAST ILLINOIS...INDIANA...AND
FAR SOUTHWEST LOWER MICHIGAN THIS EVENING AND TONIGHT. HIGHS TODAY
WILL BE IN THE IN THE 20S...BUT AREAS WHICH SAW SEVERAL INCHES OF
SNOW MAY STRUGGLE TO GET OUT OF THE TEENS. LOWS TONIGHT WILL BE IN
THE TEENS...EXCEPT COLDER SINGLE DIGITS IN THOSE SAME AREAS WITH
DEEPER SNOW.

&&

.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 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1148 AM EST MON JAN 26 2015

WEAK HIGH PRESSURE OVER THE GREAT LAKES AND PRONOUNCED DRY LAYER
IN THE LOWEST 5 KFT WILL KEEP TERMINALS MAINLY VFR INTO TOMORROW.
AREA OF LIGHT SNOW AND ASSOCIATED VIS/CIG RESTRICTIONS ALONG A
TIGHT THERMAL GRADIENT SHOULD REMAIN JUST WEST OF SBN/FWA LATE
THIS AFTN INTO TONIGHT AS SHEARED VORT MAX SLIDES SE THROUGH
ILLINOIS. ALTHOUGH CANNOT RULE OUT A FEW FLURRIES DURING THIS TIME
ACROSS NORTHERN INDIANA. OTHERWISE...WINDS WILL GENERALLY REMAIN
UNDER 6 KNOTS INTO TONIGHT. BE LIGHT/VARIABLE.

&&

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

$$

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


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