Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 201649
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
1249 PM EDT WED MAY 20 2015

.SYNOPSIS...
ISSUED AT 1249 PM EDT WED MAY 20 2015

COOL HIGH PRESSURE WILL HOLD FIRM ACROSS THE WESTERN GREAT LAKES
THROUGH TOMORROW. A WEAKENING UPPER LEVEL DISTURBANCE MAY BRING A
FEW SPRINKLES AND PERHAPS A PERIOD OF LIGHT RAIN TO THE AREA LATER
THIS AFTERNOON AND EVENING...BEST CHANCES ALONG AND SOUTH OF HIGHWAY
30. TEMPERATURES THIS AFTERNOON WILL CONTINUE WELL BELOW NORMAL
WITH HIGHS IN THE MID TO UPPER 50S EXPECTED. LOWS TONIGHT ARE
EXPECTED TO DROP INTO THE 40S...WITH HIGHS RECOVERING INTO THE LOW
TO MID 60S ON THURSDAY.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 325 AM EDT WED MAY 20 2015

POLAR RIDGE ANCHORED FM THE CNTRL PLAINS EWD INTO THE WRN OH VALLEY
XPCD TO DOMINATE THIS PD WHILE PLAINS SW TROUGH SHEARS EWD AND WKNS
TDA. GIVEN THE BREATH AND EXTENT OF DRYNESS NOTED WITHIN LL RIDGE
AXIS AND DECAYING UPR SPRT THIS AFTN SEE LTL REASON NOT TO REDUCE
POPS FURTHER.

OTRWS MUCH BLO NORMAL TEMPS TO CONT W/LTL ADVECTIVE CHG SEEN IN LL
THERMAL PROGS AND IN LIGHT OF THICKENING MID-HIGH CLD CVR TDA WITHIN
INCREASING NE SFC FLW SIDED W/COLDER SPECTRUM OF GUIDANCE TEMPS THIS
AFTN. CLDS XPCD TO PERSIST A BIT LONGER PER 00Z GUIDANCE CONSENSUS
WHICH AGAIN SHLD STAVE OFF ANY SUBSTANTIAL FROST THREAT PRIMARILY
ACRS WRN/NWRN ZONES.

&&

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 325 AM EDT WED MAY 20 2015

BENIGN WEATHER TO CLOSE OUT THE WEEK WITH A RETURN TO MORE ACTIVE
PATTERN EARLY NEXT WEEK. SLOWLY EXITING EASTERN CANADA HEIGHT
ANOMALY AND DIGGING SOUTHWEST CONUS TROUGH WILL LEAD TO GRADUAL
MID/UPPER LEVEL RIDGE BUILDING IN OUR REGION THROUGH THE WEEKEND.
RISING HEIGHTS/AVA AND CONFLUENCE ALOFT WILL SUPPORT GENERAL
SUBSIDENCE WITH PREDOMINATELY DRY CONDITIONS THROUGH SATURDAY. THERE
IS A WEAK SURFACE PRESSURE TROUGH THAT WILL MOVE THROUGH THE AREA
LATE THURSDAY NIGHT AND COULD GENERATE AN ISOLATED SPRINKLE IN OUR
FAR NORTHEAST ZONES BUT CHANCES ARE VERY LOW GIVEN NEGLIGIBLE
FORCING IN A VERY DRY/STABLE ENVIRONMENT. BUILDING RIDGE WILL ALSO
SUPPORT TEMPS MODERATING BACK TO NEAR SEASONAL AVERAGES BY THE
WEEKEND.

RIDGE AXIS PASSES OVERHEAD EARLY SUNDAY WITH PRONOUNCED LOW LEVEL
THETA-E SURGE BRINGING BACK THE CHANCES FOR SCT SHOWERS AND
THUNDERSTORMS IN SOUTHWEST FLOW AHEAD OF EJECTING WESTERN CONUS
TROUGH. WILL PROBABLY BE A GOOD SURGE OF ISENTROPIC ASCENT ON THE
LEADING EDGE BUT MODELS DISAGREE ON EXACTLY WHEN/WHERE WITH THE
LATEST GFS KEEPING MOST OF THIS ACTIVITY NORTH OF US ON SUNDAY.
CHANCES FOR RAIN THEN CONTINUE INTO MEMORIAL DAY BUT ZEALOUS MODEL
QPF/CP SCHEMES LIKELY DO NOT ACCURATELY DEPICT THE TRUE SENSIBLE
WEATHER OF THE DAY...AS WE HAVE SEEN IN RECENT EVENTS. THERE WILL
CERTAINLY BE SCT PRECIP AT TIMES BUT WITH SUBTLE (CONVECTIVELY
ENHANCED) SHORTWAVES THE ONLY FORCING MECHANISMS TO KEY IN
ON...NAILING DOWN EXACT TIMING AND COVERAGE IS IMPOSSIBLE AT THESE
TIME RANGES. THEREFORE PREFER TO MAINTAIN TREND OF PREVIOUS SHIFTS
AND HOLD POPS GENERALLY UNDER LIKELY CATEGORY...THOUGH DID ACQUIESCE
TO A FEW 60 POPS IN OUR WEST ON MONDAY TO BETTER LINE UP WITH
SURROUNDING OFFICES. WILL TRY TO ADD MORE DETAIL IN THE NEXT FEW
DAYS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1249 PM EDT WED MAY 20 2015

DRY ENE FLOW IN THE LOWEST 5-7 KFT ON THE SOUTHERN FRINGE OF SFC
RIDGE AXIS ACROSS THE UPPER MIDWEST/GREAT LAKES WILL KEEP VFR
CONDITIONS IN PLACE THROUGH THE TAF CYCLE. WEAK ELEVATED WARM
ADVECTION/ISENTROPIC ASCENT WITH A WEAK UPPER LEVEL DISTURBANCE
WILL ADVANCE EAST THROUGH NORTHERN INDIANA THIS EVENING. THE
RESULT WILL BE LOWERING OF INITIAL HIGH BASED CIGS TO BTW 5-10
KFT...AND POSSIBLY A FEW SPRINKLES OR A PERIOD OF LIGHT RAIN
DURING THIS TIME.

&&

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

$$

SYNOPSIS...STEINWEDEL
SHORT TERM...T
LONG TERM...AGD
AVIATION...STEINWEDEL


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