Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 040936
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
436 AM EST WED MAR 4 2015

.SYNOPSIS...
ISSUED AT 434 AM EST WED MAR 4 2015

MOSTLY CLOUDY SKIES ARE EXPECTED TODAY AS AN UPPER LEVEL DISTURBANCE
MOVES ACROSS THE REGION. THIS DISTURBANCE MAY RESULT IN SOME LIGHT
SNOW FROM CENTRAL INDIANA INTO PORTIONS OF NORTHWEST OHIO. ARCTIC
AIR WILL FILTER INTO THE REGION TODAY AND TONIGHT...WITH MANY
LOCATIONS EXPECTED TO REACH HIGH TEMPERATURES THIS MORNING. HIGHS ON
THURSDAY WILL ONLY REACH INTO THE TEENS FOR MOST LOCATIONS...WITH
SUBZERO LOW TEMPERATURES FOR THURSDAY NIGHT. A MODERATING
TEMPERATURE TREND IS THEN EXPECTED FOR THE UPCOMING WEEKEND AS
DEPARTING HIGH PRESSURE ALLOWS SOUTH WINDS TO DEVELOP.

&&

.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 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 117 AM EST WED MAR 4 2015

MVFR CIGS EXPECTED THROUGH MUCH OF THE PERIOD IN POST FRONTAL COLD
ADVECTION REGIME. SECONDARY FRONTAL BOUNDARY EXPECTED TO DROP DOWN
INTO THE AREA ON WEDNESDAY. STRENGTHENING COLD ADVECTION AND
DEEPENING MIXED LAYER WILL ALLOW FOR SOME INCREASE IN
WEST/NORTHWEST WIND GUSTS INTO THE 15 TO 20 KNOT RANGE WEDNESDAY
AFTERNOON. TERMINALS SHOULD REMAIN DRY WITH ANY LINGERING LIGHT
PRECIP EXPECTED TO REMAIN SOUTHEAST OF THE TERMINALS.

&&

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

$$

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


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