Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 041746
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
1246 PM EST WED MAR 4 2015

.SYNOPSIS...
ISSUED AT 1133 AM EST WED MAR 4 2015

MOSTLY CLOUDY SKIES ACROSS THE REGION TODAY AS AN UPPER LEVEL
DISTURBANCE MOVES THROUGH. SOME SNOW MAY FALL ACROSS CENTRAL
AND SOUTHERN PORTIONS OF THE REGION TODAY AND TONIGHT. SOME LIGHT
LAKE EFFECT SNOW COULD FALL IN SOUTHWEST MICHIGAN TO FAR NORTHERN
INDIANA TONIGHT AS HIGH PRESSURE BUILDS INTO THE REGION. THE HIGH
WILL ALSO USHER IN COLDER AIR. HIGHS TODAY WILL BE IN THE LOWER
30S. LOW TEMPERATURES TONIGHT WILL RANGE FROM THE SINGLE POSITIVE
DIGITS IN SOUTHERN MICHIGAN TO THE LOWER TEENS NEAR THE OHIO
RIVER.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 434 AM EST WED MAR 4 2015

TEMPERATURE TRENDS GIVEN STRENGTHENING LOW LEVEL COLD ADVECTION
TODAY AND WITH PRECIP CHANCES ACROSS THE FAR SOUTH/SOUTHEAST WILL
CONTINUE TO BE THE PRIMARY SHORT TERM FORECAST CHALLENGES TODAY
AND TONIGHT.

AXIS OF DEEPER MID LEVEL MOISTURE APPEARS TO BE TRANSLATING TO
THE SOUTHEAST OF THE LOCAL AREA EARLY THIS MORNING WHICH SHOULD
PROVIDE AT LEAST A TEMPORARY LULL IN LIGHT PRECIP CHANCES ACROSS
SOUTHEAST PORTIONS OF THE FORECAST AREA THIS MORNING. WATER
VAPOR/RAP ANALYSES DEPICT A LOW AMPLITUDE...HIGHLY SHEARED VORT
MAX ACROSS SOUTHERN IOWA THIS MORNING...WHICH SHOULD TRACK ACROSS
THE SOUTHERN GREAT LAKES THIS AFTERNOON. APPROACH OF THIS WAVE
WILL BE ACCOMPANIED BY A NARROW MID/UPPER LEVEL FGEN AXIS ALONG
WITH A BRIEF NORTHWARD SURGE OF MORE PRONOUNCED MID LEVEL
MOISTURE ACROSS SOUTHEAST PORTIONS OF THE FORECAST. 03Z SREF POPS
FOR THIS AFTERNOON ALSO SEEM TO KEY IN ON THIS FEATURE WITH
TEMPORARY UPSWING IN THE 18Z-00Z PERIOD ACROSS THE SOUTHEAST.
WHILE LOW LEVEL THERMAL PROFILES WOULD NOT SUPPORT -SN WITH LACK
OF SATURATION ABOVE FRONTAL INVERSION...MID LEVEL FGEN FORCING
AND MID LEVEL CLOUD DECK COULD PROVIDE SEEDER FEEDER MECHANISM TO
INTRODUCE A LOW END CHANCE OF SOME FLURRIES OR LIGHT SNOW. NOT
MUCH CHANGE MADE TO PREVIOUS FORECAST...AND WILL FOCUS THESE LOW
POPS ACROSS THE SOUTHEAST THIS AFTERNOON.

ELSEWHERE...HOURLY TEMPERATURE TRENDS THROUGH THIS AFTERNOON WILL
BE A CHALLENGE GIVEN SKY COVER AND ADVECTION CONSIDERATIONS. LOW
CLOUDS HAVE HELD TEMPERATURES IN THE UPPER 20S TO MID 30S THROUGH
MUCH OF THE NIGHT...WITH ONLY LIMITED TEMP DROPS ANTICIPATED OVER
THE NEXT SEVERAL HOURS. PERHAPS SOME WINDOW OF CLEARING MAY EXIST
TOWARD DAYBREAK ACROSS WESTERN LOCATIONS THAT COULD ALLOW TEMPS
TO DROP INTO THE LOWER TO MID 20S. STRONG LOW LEVEL COLD
ADVECTIVE SURGE TO WORK ACROSS THE SOUTHERN GREAT LAKES THIS
AFTERNOON AS BROADER POSITIVELY TILTED UPPER TROUGH BEGINS TO
WORK ACROSS THE NORTHERN GREAT LAKES. THIS SHOULD ALLOW FOR
STEADY OR SLOWLY FALLING TEMPERATURES EARLY THIS AFTERNOON...WITH
A SHARPER TEMPERATURE DROP LATE AFTERNOON/EARLY EVENING. MOST
LOCATIONS WILL REACH MAX TEMPS THIS MORNING DUE TO LOW CLOUD DECK
AND TIMING OF STRONGER LOW LEVEL COLD ADVECTION LATER THIS
AFTERNOON.

LOW LEVEL THERMAL TROUGH TO BECOME ENTRENCHED TONIGHT WITH UPPER
LEVEL TROUGH TRACKING THROUGH THE REGION. SOME INCREASE OF AT
LEAST SCATTERED LAKE EFFECT SNOW SHOWERS IS EXPECTED...ALTHOUGH
LARGE SCALE SYNOPTIC SUBSIDENCE AND RELATIVELY LARGE DEW POINT
DEPRESSIONS ABOVE THE INVERSION SHOULD LIMIT OVERALL THREAT. SOME
LIGHT ACCUMULATIONS OF LESS THAN AN INCH ARE POSSIBLE...BUT WILL
MAINTAIN HIGH CHANCE POPS FOR NORTHWEST FETCH LAKE EFFECT PRONE
AREAS TONIGHT. LACK OF DECOUPLING AND POSSIBILITY OF LOW CLOUDS
PERSISTING SHOULD KEEP MINS IN THE 5 ABOVE TO 12 ABOVE RANGE
TONIGHT...WITH WIND CHILLS IN THE 5 ABOVE TO 5 BELOW RANGE.

&&

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 434 AM EST WED MAR 4 2015

ONE LAST ARCTIC SURGE OF BITTERLY COLD WILL INVADE THE AREA
BEFORE THE THE NORTHERN STREAM FINALLY BECOMES MORE HIGH ZONAL
AND ALLOWS TEMPERATURES TO RECOVER TO NEAR AND ABOVE NORMAL EARLY
NEXT WEEK. INHERENT CHALLENGES THIS PERIOD INCLUDE WEAK UPPER
LEVEL TROFS THAT MAY BE ABLE TO PRODUCE SOME LIGHT PRECIPITATION
AND BRIEFLY TAP SOME COOLER AIR. VERY COLD AIR HAS BEEN OVER THE
AREA FOR NEARLY 3 WEEKS WITH THE AVERAGE TEMPERATURE AT FT WAYNE
ONLY 11.5 SINCE FEBRUARY 12TH. DURING THIS PERIOD...NCEP
TEMPERATURE GUIDANCE FOR HIGHS HAVE HAD A MARKED COOL BIAS IN THE
COLD AIR WITH CLEAR TO PARTLY CLOUDY SKIES. THE COLDEST RECORD
COLD HIGHS FOR THURSDAY...MARCH 5TH IN OVER A HUNDRED YEARS ARE
20 AND 17 FOR SOUTH BEND AND FORT WAYNE RESPECTIVELY.
THEREFORE...WITH ALL OF THIS CONSIDERED...HAVE GONE 4 TO 5
DEGREES ABOVE NCEP GUIDANCE FOR HIGHS THURSDAY. FOR THURSDAY
NIGHT...RECORD LOWS ARE -7 AND -4 AT SOUTH BEND AND FT WAYNE
RESPECTIVELY. EXPECT IDEAL RADIATIONAL COOLING THURSDAY
NIGHT...WHICH SHOULD ALLOW TEMPERATURES TO DROP BELOW ZERO. HAVE
LOWERED LOWS 3 TO 4 DEGREES TO COME IN LINE CLOSER TO THESE
RECORD LOWS GIVEN RECENT HUGE DIURNAL SWINGS IN THIS COLD
PATTERN. OTHERWISE...A WEAK LAKE RESPONSE IS POSSIBLE WITH
FAVORABLE DELTA T VALUES...BUT LOW INVERSION HEIGHTS THURSDAY
INTO THURSDAY NIGHT. MUCH WARMER WEATHER IS EXPECTED STARTING
THIS WEEKEND. DEEP SNOW COVER MAY INITIALLY INHIBIT THE WARMUP
OVER NORTHERN AREAS...SO WENT A LITTLE COLDER OVER FAR NORTHERN
INDIANA AND SOUTHWEST LOWER MICHIGAN. KEPT CONDITIONS DRY EXCEPT
FOR A CHANCE FOR SNOW SUNDAY NIGHT WITH THE PASSAGE OF A WEAK
UPPER TROF.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1242 PM EST WED MAR 4 2015

HIGH END MVFR TO LOW END VFR MET CIGS ANTCIPATED THROUGH THE
FORECAST PD AS CONTD LOW LEVEL COLD AIR ADVECTION CONTS. NRN
FRINGE OF LESSER/SECONDARY MID LEVEL DEFORMATION AXIS COULD BRING
AFTN/EVE FLURRIES...THOUGH OF NO VSBY IMPACT. BETTER CHC FOR
NOMINAL LAKE EFFECT RESPONSE INVOF KSBN LATE TONIGHT INTO
THU,..THOUGH AGAIN LITTLE IF ANY IMPACT TO VSBY ANTICIPATE.

&&

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

$$

SYNOPSIS...LOTHAMER
SHORT TERM...MARSILI
LONG TERM...SKIPPER
AVIATION...MURPHY


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