Area Forecast Discussion
Issued by NWS Northern Indiana

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842
FXUS63 KIWX 080215
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
915 PM EST SUN FEB 7 2016

.SYNOPSIS...
ISSUED AT 650 PM EST SUN FEB 7 2016

SCATTERED LIGHT RAIN IS POSSIBLE THROUGH THE EARLY PORTIONS OF THE
OVERNIGHT HOURS MAINLY EAST OF INTERSTATE 69 AS A COLD FRONTAL
BOUNDARY TRACKS ACROSS THE AREA. A SERIES OF UPPER LEVEL
DISTURBANCES WILL THEN AFFECT THE AREA FROM MONDAY THROUGH
WEDNESDAY. ACCUMULATING SNOWFALL WILL BE SEEN ACROSS THE ENTIRE
REGION OVER THE UPCOMING WEEK WITH THE HEAVIEST AMOUNTS EXPECTED
CLOSER TO LAKE MICHIGAN. COLDER AIR WILL CONTINUE TO FILTER INTO
THE REGION FOR THE FIRST HALF OF THE WEEK...ESPECIALLY BY TUESDAY
TUESDAY AND WEDNESDAY.

&&

.UPDATE...
ISSUED AT 900 PM EST SUN FEB 7 2016

A FAIRLY STRONG MID LEVEL FRONT WILL CONTINUE TO WORK ACROSS
EASTERN PORTIONS OF THE FORECAST AREA THROUGH 06Z. AN APPROACHING
MID/UPPER VORT MAX AND SOME MODEST INCREASE IN FRONTOGENETIC FLOW
WITH THIS MID LEVEL BAROCLINIC ZONE SHOULD ALLOW FOR SOME LIGHT
RAIN TO DEVELOP ACROSS THE FAR EAST. WILL KEEP LOW TO MID CHANCE
POPS GOING MAINLY EAST OF INTERSTATE 69 THROUGH 06Z...WITH SLIGHT
CHANCE PROBS OVERNIGHT AS MID LEVEL BAROCLINIC ZONE BEGINS TO
SLOW ITS EASTWARD PROGRESSION A BIT. OTHERWISE NEXT FEATURE TO
WATCH FOR OVERNIGHT WILL BE FAIRLY STRONG VORT MAX CURRENTLY
DROPPING EAST-SOUTHEASTWARD ACROSS SOUTH CENTRAL IOWA. GIVEN
SOUTHEAST TRACK OF STRONGEST FORCING...BEST CHANCE OF LATE NIGHT
SNOW SHOWERS MAY BE CONFINED TO SOUTHWEST PORTIONS OF THE AREA.
NO CHANGE TO LIKELY POPS AFTER 12Z ACROSS THE WEST AS NEXT LOW
LEVEL BAROCLINIC APPROACHES IN ASSOCIATION WITH THIS PV ANOMALY.

&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 300 PM EST SUN FEB 7 2016

UPPER TROUGH OVER THE UPPER MIDWEST WILL DIG SE INTO THE EASTERN US
TONIGHT-MONDAY IN RESPONSE TO WEST COAST RIDGE AMPLIFICATION. AT THE
SFC...997 MB LOW NEAR DULUTH MN WILL BROADEN SE INTO LOWER MI
FORCING A CDFNT THROUGH ON LEADING EDGE OF EXTREME HEIGHT FALLS EAST
TONIGHT. THE RESULT WILL BE A TREND TOWARD COOLER TEMPS AND CHANCES
FOR PRECIPITATION.

FIRST OPPORTUNITY FOR A LIGHT RAIN/SNOW MIX WILL COME THIS EVENING
INTO THE EARLY OVERNIGHT MAINLY ALONG/EAST OF INTERSTATE 69 AS
INCREASING UPPER DIVERGENCE AND STRONG MID LVL DCVA ENHANCE LOW-MID
LEVEL CONVERGENCE ALONG SFC FRONT ONCE REACHING OHIO. HELD POPS IN
CHANCE RANGE HERE GIVEN INITIAL FIGHT WITH DRY AIR IN LOWEST 10 KFT.
ONSET OF PCPN (IF IT DEVELOPS) WOULD LIKELY BE RAIN GIVEN WARM NEAR
SFC LAYER...AND THEN TRANSITION TO A BRIEF RAIN/SNOW MIX (LITTLE TO
NO ACCUMULATION) LATE EVENING/OVERNIGHT BEFORE ENDING.

MONDAY WILL FEATURE SCATTERED TO NUMEROUS SNOW SHOWERS AS DEEPER
MOISTURE/SATURATION OVERSPREADS UNDER CLOSED MID LVL CIRCULATION.
ASSOCIATED SECONDARY PV PUSH/CDFNT WITH LAPSE RATES STEEPENING UNDER
COLD POCKET ALOFT COULD ALLOW FOR BRIEF HEAVIER SQUALLS WHICH COULD
LAY DOWN A QUICK DUSTING TO HALF INCH. ROADS FOR THE MOST PART
SHOULD BE IN DECENT SHAPE GIVEN MARGINAL SFC TEMPS.

&&

.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 300 PM EST SUN FEB 7 2016

AN EXTENDED STRETCH OF BELOW NORMAL TEMPS AND LONG DURATION LAKE
ENHANCED/EFFECT SNOW EVENT MONDAY NIGHT THROUGH THURSDAY THE PRIMARY
FOCUS THROUGH THE EXTENDED...

MODELS REMAIN IN GOOD AGREEMENT IN LOW LEVEL CIRCULATION/TROUGH
EDGING SLOWLY EAST OVER THE EASTERN GREAT LAKES MONDAY NIGHT THROUGH
WEDNESDAY...WITH CONTINUED COLD ADVECTION IN NW FLOW (850 MB TEMPS
-10C MONDAY NIGHT TO -18C WEDNESDAY) AND AMPLE BACKGROUND MOISTURE
TO SET UP A PROLONGED NW FLOW LAKE ENHANCED/EFFECT SNOW EVENT.
IMPRESSIVE MOISTURE DEPTH TO 15 KFT AND 20-25 KNOTS WITHIN 925-800
MB LAYER SHOULD FAVOR GOOD INLAND PENETRATION OF LAKE ENHANCED SNOW
SHOWERS LATER MONDAY NIGHT THROUGH EARLY WEDNESDAY. LIMITING FACTOR
FOR HEAVIER SNOWFALL RATES/RATIOS AT LEAST INITIALLY (LATE MONDAY
NIGHT-TUESDAY) WILL BE SOMEWHAT MARGINAL DELTA T/S AND BETTER
OMEGA/HIGHER THETA-E LAPSE RATES TAKING PLACE JUST BELOW THE DGZ.
THIS OVERLAP AND RESULTING POTENTIAL FOR MORE IMPRESSIVE
BANDING/HIGHER RATIOS BECOMES MORE FAVORABLE BY TUESDAY NIGHT-
WEDNESDAY AS LAKE-700 MB DIFFERENTIALS PUSH WELL INTO THE 20S. A
LONG DURATION ADVISORY WILL LIKELY BE NEEDED FOR AT LEAST ST JOE
IN/CASS MI/BERRIEN COUNTIES LATER MONDAY NIGHT THROUGH
WEDNESDAY...WITH LIGHTER ACCUMS/IMPACTS TO TRAVEL ANTICIPATED WELL
INLAND. DRIER POLAR AIR AND BACKING WINDS/LOWERING INVERSION HEIGHTS
SHOULD ALLOW FOR LAKE EFFECT SNOW TO WIND DOWN INTO LATER WEDNESDAY-
THURSDAY AS EASTERN LAKES SYSTEM FINALLY LIFTS OUT.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z MONDAY EVENING)
ISSUED AT 650 PM EST SUN FEB 7 2016

A COLD FRONT WILL TRACK ACROSS NORTHEAST INDIANA THIS EVENING
BRINGING A LOW PROBABILITY OF LIGHT RAIN TO KFWA. CURRENT
THINKING IS THAT HIGHER PROBABILITIES OF LIGHT RAIN WILL AFFECT
AREAS EAST OF KFWA...AND THUS WILL KEEP THE TERMINAL DRY THIS
EVENING. LOW LEVEL COLD ADVECTION TO THEN CONTINUE OVERNIGHT WITH
GENERALLY VFR CONDITIONS EXPECTED UNTIL LATE TONIGHT WHEN MVFR
CIGS ARE EXPECTED TO DEVELOP. CONFIDENCE IN CIGS BELOW FUEL
ALTERNATE CRITERIA IS TOO LOW TO MENTION AT THIS TIME THROUGH 12Z.
SECONDARY FRONTAL BOUNDARY WILL APPROACH NORTHWEST INDIANA EARLY
MONDAY MORNING WITH BAND OF SNOW SHOWERS EXPECTED TO DEVELOP ALONG
AND JUST AHEAD OF THIS BOUNDARY. THIS FORCING SHOULD BE
ACCOMPANIED BY GREATER CHANCE OF IFR CONDITIONS FROM MID TO LATE
MORNING AT KSBN...AND IN THE AFTERNOON AT KFWA. SOUTHWEST WINDS
AROUND 10 KNOTS WILL BECOME WEST 5 TO 10 KNOTS TONIGHT...AND THEN
WEST-NORTHWEST 10 TO 15 KNOTS LATER MONDAY BEHIND SECONDARY
FRONTAL PASSAGE.


&&

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

$$

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


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