Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 161850
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
250 PM EDT THU APR 16 2015

.SYNOPSIS...
ISSUED AT 1105 AM EDT THU APR 16 2015

WITH A DISTURBANCE MOVING THROUGH THE REGION RAIN CHANCES WILL BE
AROUND TODAY. THESE CHANCES WILL MOVE ON OUT OF THE REGION THIS
EVENING INTO TONIGHT. HIGH TEMPERATURES TODAY WILL BE IN THE 50S
NEAR LAKE MICHIGAN AND RANGE FROM THE LOWER 60S IN SOUTHERN
MICHIGAN TO THE UPPER 60S NEAR THE OHIO RIVER. LOW TEMPERATURES
TONIGHT WILL RANGE FROM THE LOWER 40S NEAR LAKE MICHIGAN TO THE
MIDDLE 50S ALONG THE OHIO RIVER.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 357 AM EDT THU APR 16 2015

COMPACT MID LEVEL CIRCULATION EMBEDDED WITHIN BROAD/WEAK UPPER
LEVEL TROUGH WILL LIFT NORTHEAST THROUGH NW IN/SW LOWER MI EARLY
THIS MORNING. OCCASIONAL RAIN WILL ACCOMPANY THIS FEATURE WEST OF
INTERSTATE 69 AS CORRIDOR OF ENHANCED MOISTURE CONVERGENCE/THETA-E
ADVECTION ON EASTERN FLANK OF CIRC LIFTS THROUGH. MAY SEE SOME
LOCALIZED (NEEDED) RAINFALL TOTALS EXCEED A HALF INCH GIVEN AMPLE
MOISTURE (850 MB DEWPOINTS NEAR 9C) AND LOW CHANCE FOR A
CONVECTIVE COMPONENT. NOT OVERLY IMPRESSED WITH MID LEVEL LAPSE
RATES (6-7 C/KM) OR BACKGROUND FLOW/FORCING FOR THUNDER
CHANCES...BUT CANNOT COMPLETELY RULE OUT THUNDER INTO AT LEAST
SOUTHWESTERN PORTIONS OF THE FA GIVEN UPSTREAM TRENDS UNDER
VORTICITY CENTER.

TRAILING SFC TROUGH WILL THEN EDGE SLOWLY EAST INTO
CENTRAL/EASTERN PORTIONS OF THE FA THIS AFTN/EVE. THERE SHOULD BE
ENOUGH LOW LEVEL MOISTURE POOLING/CONVERGENCE, SOME DIURNAL
HEATING, AND ADDITIONAL/WEAKER SHORTWAVE FILAMENTS EMBEDDED IN
LARGER SCALE TROUGH TO FORCE A FEW SHOWERS ALONG THIS FEATURE.
CONTEMPLATED REMOVING SLIGHT CHC THUNDER MENTION ACROSS
CENTRAL/SOUTHEAST ZONES GIVEN EXPECTED CLOUD COVER/LACKING
INSTABILITY...BUT GIVEN FAVORABLE DIURNAL TIMING AND OVERSPREAD OF
DRIER AIR OVER AN INCREASINGLY MOIST BL OPTED TO RETAIN MENTION
FOR NOW. OTHERWISE EXPECT CLOUDS/MOISTURE TO LIMIT TEMP RISES
SOMEWHAT TODAY.

&&

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 357 AM EDT THU APR 16 2015

QUIET END TO THE WEEK STILL ON TAP AS CONFLUENCE ALOFT MAINTAINS
WEAK HIGH PRESSURE OVER THE GREAT LAKES AHEAD OF SLOWLY APPROACHING
CUTOFF LOW. MOSTLY SUNNY SKIES EXPECTED ON FRIDAY AND WITH 850MB
TEMPS AROUND 8C...AFTERNOON HIGHS SHOULD CLIMB INTO AT LEAST THE
LOWER 70S. MAV GUIDANCE EVEN SUGGESTS SOLID MID 70S AND THIS IS
CERTAINLY NOT OUTSIDE THE REALM OF POSSIBILITY GIVEN NEARLY FULL
INSOLATION AND ANOTHER DAY OF DEEP PBL MIXING. GUIDANCE HAS
STRUGGLED IN THESE SETUPS LATELY AND HAVE ADJUSTED MAX TEMPS UP BY
SEVERAL DEGREES. LOW LEVEL THERMAL PROFILES ARE A TOUCH WARMER FOR
SATURDAY BUT MAY BE PARTIALLY OFFSET BY INCREASING MID/UPPER LEVEL
CLOUDINESS. HIGHS WILL PROBABLY BE SIMILAR TO FRIDAY AND HAVE BUMPED
THOSE UP AS WELL.

CHANCES FOR RAIN INCREASE PRECIPITOUSLY EARLY SUNDAY MORNING AS
FIRST SLUG OF LOW LEVEL THETA-E ADVECTION AND 295-300K SYSTEM
RELATIVE ISENTROPIC ASCENT LIFT INTO THE AREA. MIDLEVEL
HEIGHT/VORTICITY FIELDS ALSO SHOW A DECENT EMBEDDED SHORTWAVE
LIFTING THROUGH THE REGION WITH GOOD 700MB FGEN AND OMEGA
SIGNATURES. LATEST MODELS ARE IN FAIRLY GOOD AGREEMENT AND HAVE
INCREASED POPS FOR THE SUNDAY MORNING PERIOD GIVEN DEGREE OF
SYNOPTIC FORCING IN A VERY MOIST ENVIRONMENT (PW VALUES CLIMB TO
AROUND 1.25 INCHES). DID STOP JUST SHORT OF CATEGORICAL
THOUGH...SINCE IT IS STILL ROUGHLY THREE DAYS OUT. EXPECT A BRIEF
BREAK SUNDAY AFTERNOON BEFORE SECONDARY WAVE OF PRECIP ASSOCIATED
WITH MAIN TROUGH AXIS MOVES INTO THE AREA SUNDAY NIGHT. VERY LITTLE
LEFT OF OLD CUTOFF LOW BY THIS POINT...AS IT IS ABSORBED BY
STRENGTHENING NORTHERN STREAM WAVE. STILL...BOTH GFS AND ECMWF SHOW
A DECENT RESIDUAL VORT MAX CLIPPING THE SOUTHERN GREAT LAKES AND LOW
END LIKELY POPS APPEAR WARRANTED. BEHEMOTH CLOSED LOW THEN MEANDERS
OVER ONTARIO AND THE NORTHERN GREAT LAKES FOR MUCH OF NEXT WEEK.
MODELS SUGGEST A LOW CHANCE OF SHOWERS...MAINLY DURING THE
AFTERNOON...EACH DAY BUT WOULDN`T BE SURPRISED IF BULK OF THE PERIOD
REMAINED DRY GIVEN NORTHWARD DISPLACEMENT OF NEGATIVE HEIGHT
ANOMALY. THIS PATTERN WILL LIKELY KEEP US ON THE COOL SIDE OF
CLIMATOLOGICAL AVERAGES THOUGH...WITH HIGHS IN THE 50S AND LOWS IN
THE 30S.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 242 PM EDT THU APR 16 2015

A WEAK UPPER TROF WITH SOME LOW LEVEL MOISTURE HAS BEEN SUFFICIENT
TO PRODUCE SOME SHOWERS OVER THE AREA THROUGH MIDDAY. SUBSIDENCE
BEHIND THIS SYSTEM SHOULD HELP TO ELIMINATE SHOWERS TONIGHT...AND
TO ALLOW SOME CLEARING. ADDED SOME MVFR FOG AT SBN FROM 09Z TO 13Z
WHERE SKIES SHOULD BE PARTLY CLOUDY.

&&

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

$$

SYNOPSIS...LOTHAMER
SHORT TERM...STEINWEDEL
LONG TERM...AGD
AVIATION...SKIPPER


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