000
FXUS63 KIWX 171715
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
115 PM EDT FRI MAY 17 2013

.SYNOPSIS...
ISSUED AT 1039 AM EDT FRI MAY 17 2013

A FRONTAL BOUNDARY WILL SLOWLY SHIFT NORTH TODAY...BRINGING A
CHANCE FOR SHOWERS AND THUNDERSTORMS TO PORTIONS OF NORTHERN
INDIANA. THIS FRONT WILL REMAIN IN THE GENERAL AREA THROUGH
SATURDAY BEFORE SHIFTING NORTH OF THE REGION SUNDAY. BETTER
CHANCES FOR SHOWERS AND THUNDERSTORMS WILL ARRIVE BY TUESDAY INTO
WEDNESDAY.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 441 AM EDT FRI MAY 17 2013

THE CHALLENGES FOR TODAY AND TONIGHT INCLUDE COVERAGE AND TIMING OF
ANY SHOWERS AND THUNDERSTORMS. A NORTHEAST FETCH OF VERY DRY
CANADIAN AIR WILL CONTINUE TO KEEP DEW POINTS IN THE 30S AND 40S
NORTHEAST OF THE FRONT. OVERNIGHT...THE FRONT HAD REMAINED
STATIONARY FROM JUST SOUTH OF LOGANSPORT TO NEAR LIMA. SOME
OVERNIGHT STORMS WEST OF THE AREA OCCURRED SOUTH OF CHICAGO ALONG
THE FRONT NEAR THE INTERSECTION OF LOW LEVEL WIND MAXIMUM AND THE
FRONT. EXPECT THE FRONT TO BECOME ACTIVE THIS AFTERNOON WITH DAYTIME
HEATING...WITH SFC BASED CONVECTION DEVELOPING ALONG AND SOUTH OF
THE FRONT. NAM12 BUFKIT CAPES REACH 1000-1500 J/KG BY LATE
AFTERNOON...AND SHOULD SUPPORT AT LEAST ISOLATED THUNDERSTORMS OVER
SOUTH AND SOUTHWEST AREAS. THEREFORE...ADDED SHOWERS AND ISOLATED
THUNDER OVER THESE AREAS. OTHERWISE...NAM MET/GFS MAV HIGHS LOOK GOOD
TODAY. LOWERED TEMPS FAR NORTH 1-2 DEGREES WITH COOLER NORTHEAST
FETCH. GUT FEELING LOWS IN THE NORTH AND NORTHEAST ARE STILL TOO
WARM AND WILL NEED TO BE LOWERED MORE.

&&

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 441 AM EDT FRI MAY 17 2013

SPORADIC INSIPID CONVECTION TO PERSIST INTO SATURDAY...ONCE AGAIN
FOCUSED IN THE SOUTHERN THIRD OF THE CWA AND DURING AFTERNOON PEAK
HEATING. MARGINAL PRECIP CHANCES BEING SUPPORTED BY WEAK
PERTURBATION IN THE MIDLEVEL HEIGHT FIELD DRIFTING ACROSS THE
SOUTHERN OHIO VALLEY. HOWEVER...PALTRY MIDLEVEL LAPSE RATES COUPLED
WITH SURFACE DEWPOINTS BARELY IN THE LOW 60S RESULTS IN ONLY ABOUT
500 J/KG OF 0-1KM MLCAPE. FURTHERMORE...MODEST EASTERLY COMPONENT TO
THE LOW LEVEL FLOW EMANATING FROM EASTERN CANADA ANTICYCLONE WILL
LIKELY CONTINUE ON SATURDAY AND RESULT IN MORE STABLE LAKE-MODIFIED
AIRMASS ACROSS MICHIGAN AND OUR NORTHERN CWA. OLD SURFACE FRONTAL
BOUNDARY AND ASSOCIATED CONVERGENCE ALSO BECOME INCREASINGLY
DIFFICULT TO PINPOINT BY LATE SATURDAY AS THE UPPER WAVE SHIFTS
EAST. GIVEN THESE CONDITIONS...EXPECT SCATTERED THUNDERSTORMS AT
BEST AND MAINLY ACROSS THE SOUTH. WITH A RATHER HOMOGENEOUS AIRMASS
IN PLACE AND NO THERMAL ADVECTIONS TO SPEAK OF...HIGH TEMPS ON
SATURDAY WILL BE VERY SIMILAR TO TODAY AND YESTERDAY...AROUND 80F.

TRANSIENT MID/UPPER LEVEL RIDGING WILL BE IN PLACE ON SUNDAY.
RELATIVELY DRY TROPOSPHERE AND GENERAL SYNOPTIC SUBSIDENCE SHOULD
KEEP MOST AREAS PRECIP-FREE. LATEST NAM AND GFS BUFR SOUNDINGS ARE A
BIT WORRISOME THOUGH WITH MODERATE INSTABILITY AND A VERY WEAK CAP
THAT MAY WELL BE OVERCOME BY STRONG DIURNAL HEATING. LACK OF FORCING
MECHANISM AND DEEPER MOISTURE WILL LIKELY LIMIT COVERAGE BUT CANT
RULE OUT SOME ISOLATED CONVECTION AND WILL CONTINUE WITH BLANKET
SLIGHT CHANCE POPS. WEAK WIND SPEEDS ALOFT/LOW BULK SHEAR VALUES
WILL PREVENT ORGANIZED CONVECTION DESPITE POTENTIAL FOR MODERATELY
HIGH CAPE VALUES. HIGH TEMPS ON SUNDAY MAY CLIMB A FEW DEGREES
HIGHER GIVEN VEERING LOW LEVEL WINDS AND STRONG SOLAR INSOLATION.
850MB TEMPS LOOK TO BE AROUND 16C BY THE AFTERNOON...SUPPORTING
HIGHS IN THE LOW TO MID 80S.

PRECIP CHANCES THEN LOOK TO STEADILY INCREASE EARLY NEXT WEEK AS A
VERTICALLY STACKED SYSTEM SLOWLY APPROACHES THE GREAT LAKES REGION.
DEEP SOUTHWEST FLOW WILL DEVELOP BY MONDAY...ADVECTING HIGH THETA-E
AIR INTO THE REGION. 850MB TEMPS CONTINUE TO CREEP INTO THE UPPER
TEENS AND AFTERNOON SURFACE TEMPS MONDAY WILL LIKELY PUSH INTO THE
MID 80S ONCE AGAIN. INCREASING MOISTURE AND APPROACHING HEIGHT FALLS
WILL LEAD TO INCREASING COVERAGE OF SHOWERS AND THUNDERSTORMS WITH
THE BEST CHANCE FOR WIDESPREAD PRECIP IN THE TUES/WED TIMEFRAME.
INCREASED CLOUDS/PRECIP WILL TEMPER HIGHS A BIT DURING THIS PERIOD
BUT STILL EXPECT AFTERNOON TEMPS AROUND 80F. COOLER/DRIER CONDITIONS
THEN EXPECTED BY THE END OF THE WEEK AS TROUGH AXIS EXITS EASTWARD
AND CANADIAN SURFACE HIGH BUILDS OVER THE GREAT LAKES.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 109 PM EDT FRI MAY 17 2013

VFR CONDITIONS EXPECTED THROUGH THE TAF PD AT TERMINALS. LIGHT
EASTERLY FLOW WILL PERSIST WITH FRONTAL BOUNDARY SOUTH OF THE AREA
THROUGH THE PERIOD. AFTERNOON SHOWERS/ISOLATED STORMS ARE EXPECTED
TO DEVELOP SOUTH AND SOUTHWEST OF TERMINALS. LATEST MODEL GUIDANCE
SUGGESTS CONVECTION SHOULD REMAIN OUT OF TERMINALS...HOWEVER THERE
IS A SMALL CHANCE THAT DYING THUNDERSTORMS COULD ADVECT INTO THE
VICINITY OF TERMINALS...WITH A RISK OF -SHRA FROM 21Z THROUGH JUST
AFTER 00Z. CONFIDENCE TOO LOW TO INCLUDE -SHRA MENTION IN
TAFS...AND WILL MONITOR CONVECTIVE TRENDS THIS AFTERNOON AND
UPDATE TAFS AS NEEDED.

&&

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

$$

SYNOPSIS...FISHER
SHORT TERM...SKIPPER
LONG TERM...AGD
AVIATION...NG


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