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000
FXUS63 KIWX 150621
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
220 AM EDT WED MAY 15 2013

.SYNOPSIS...
ISSUED AT 726 PM EDT TUE MAY 14 2013

AN UPPER LEVEL DISTURBANCE TRACKING OUT OF THE PACIFIC NORTHWEST
WILL MOVE INTO ONTARIO TONIGHT. A COLD FRONT TRAILING SOUTH FROM
THIS DISTURBANCE WILL DROP INTO THE REGION ON WEDNESDAY PROVIDING
A CHANCE OF SHOWERS AND THUNDERSTORMS WEDNESDAY AFTERNOON THROUGH
THURSDAY. HIGH TEMPERATURES WILL BE IN THE LOW TO MID 80S ON
WEDNESDAY BEFORE MODERATING TO THE UPPER 70S ON THURSDAY.

&&

.UPDATE...
ISSUED AT 937 PM EDT TUE MAY 14 2013

ALTHOUGH EVE SOUNDINGS QUITE DRY/CAPPED...SCT SHOWERS/THUNDERSTORMS
WHICH DEVELOPED ALONG THE CDFNT TO THE NW THIS AFTN SURVIVING INTO
SRN WI/NRN IL BORDER REGION ATTM. CONCERNED THERE MAY BE
SUFFICIENT ELEVATED FORCING/INSTABILITY FOR SOME OF THIS
CONVECTION TO PERSIST INTO FAR NRN PORTION OF OUR CWA
OVERNIGHT... ESPECIALLY GIVEN LATEST MODELS DEPICTION OF
STRENGTHENING LLJ AHEAD OF THE FRONT. THUS, INTRODUCED SLIGHT
CHANCE POPS ACROSS THE FAR NORTH OVERNIGHT AND BUMPED UP
WINDS/TEMPS ACROSS MUCH OF THE AREA FOR THE SAME TIME FRAME.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 343 PM EDT TUE MAY 14 2013

THE MAIN CHALLENGES THIS PERIOD ARE CHANCES AND LOCATIONS FOR ANY
THUNDERSTORMS TONIGHT AND WEDNESDAY AFTERNOON. A VERY STRONG WARM
FRONT WAS LIFTING NORTH ACROSS THE AREA THIS AFTERNOON. THE PRESSURE
GRADIENT WILL TIGHTEN OVER THE AREA OVERNIGHT...PREVENTING WINDS
FROM DECOUPLING MUCH. FAVORED THE WARMER MET TEMPS IN THIS
REGARD...GIVEN THIS UNUSUAL VERY WARM PATTERN INCLUDING TUESDAY
AFTERNOON HIGHS JUST UPSTREAM IN THE 90S...AND TOPPING 100 DEGREES
FURTHER WEST. AN IMPRESSIVE AXIS OF THETA E ALONG THE FRONT WITH
VALUES OF 337K AT 850 MB WILL SURGE SOUTHEAST OVERNIGHT. REALLY A
HARD CALL ABOUT INTRODUCING CONVECTION OVERNIGHT...BUT BELIEVE MID
LEVEL CAPPING AND ESPECIALLY A DRY LOWER ENVIRONMENT WILL INHIBIT
CONVECTION. THE NAM/WRF WAS SHOWING TOO MUCH MOISTURE IN THE LOW
LEVELS...SO FOR NOW LEFT THE FORECAST FOR TONIGHT DRY. AS FOR
WEDNESDAY...LOWERED THUNDERSTORM CHANCES OVER MOST AREAS. AGAIN...
BELIEVE MID LEVEL CAPPING AND DRY CONDITIONS IN THE LOW LEVELS WILL
INHIBIT CONVECTION.

&&

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 343 PM EDT TUE MAY 14 2013

FORECAST PERIOD TO BEGIN WITH STALLED FRONTAL BOUNDARY OVER THE
REGION WITH LATEST MODEL GUIDANCE TRENDING FURTHER SOUTH SUGGESTING
GREATER POTENTIAL FOR DRY FCST WED NIGHT OVER MUCH OF THE FORECAST
AREA...HAVE CONTINUED DOWNWARD TREND IN POPS FOR THIS PERIOD
ACCORDINGLY. SOUTHERN STREAM SHORTWAVE WILL BE MOVING ACROSS THE TN
VALLEY ON THURSDAY WITH MODELS OFFERING VARYING SOLNS ON RESULTING
POSITION OF SFC FRONT...SO LEANING TOWARD NO CHANGES TO THIS PERIOD
AND STAYING WITH DRY FCST FOR ALL BUT EXTREME SOUTHERN PORTION OF
THE CWA. UPSTREAM PATTERN THEN BEGINS TO AMPLIFY ON FRIDAY AS UPPER
TROF DIGS INTO THE WEST COAST. RIDGING IN THE PLAINS IN RESPONSE TO
THIS ALONG WITH WEAK SHORTWAVE COMING OUT OF THE MID MS VALLEY WILL
BRING NORTHWARD MOVEMENT TO SFC FRONT AND INCREASING PRECIP CHANCES
GOING INTO THE WKND. UPPER TROF EJECTS OUT OF THE FOUR CORNERS ON
SAT INDUCING LEE SIDE CYCLOGENESIS IN THE WESTERN PLAINS AND ALSO
SHIFTING UPPER RIDGE AXIS OVER OUR AREA. END RESULT MAY BE A CAPPED
WARM SECTOR OVER US AND A DRY DAY FOR SUNDAY. PLENTY OF UNCERTAINTY
REMAINS WITH THIS SCENARIO PLAYING OUT SO STILL MAY NEED TO CARRY A
SMALL CHANCE POP ATTM. LOW CONFIDENCE PATTERN BEING OFFERED TOWARD
THE END OF THE FCST PERIOD WITH A VERTICALLY STACKED AND CLOSED
SYSTEM SOMEWHERE IN THE WESTERN GREAT LAKES/NORTHERN PLAINS. THIS
PATTERN WOULD LEND ITSELF TOWARD SOME TYPE OF PRE-FRONTAL TROF
AND/OR SHORT WAVE EJECTING OUT OF THE CLOSED LOW PRIOR TO THE
ARRIVAL OF THE PRIMARY FRONT AND THEREFORE FAVORING A CONTINUED
CHANCE OF SH/TSRA THROUGH DAY 7. TEMPS ON AVERAGE EXPECTED TO BE
5-10F ABOVE NORMAL THROUGH THE EXTENDED PERIOD.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY MORNING)
ISSUED AT 220 AM EDT WED MAY 15 2013

VFR CONDS WILL CONT THROUGH THE VALID TAF PD. UPSTREAM CDFNT ACRS
ERN IA IN ASSOCN/W SW TROUGH PROGRESSING EWD THROUGH CNTRL ONTARIO
THIS MORNING WILL ACCELERATE EWD NR TERM.  TRAILING SRN PORTION OF
THIS BNDRY XPCD TO STALL OUT THROUGH CNTRL IL/IN THIS AFTN ALG NRN
TERMINUS OF MID LVL CONFLUENCE ZONE. HWVR THIS FTR XPCD TO SETTLE
FAR ENOUGH S TO PRECLUDE ANY ASSOCD WX AT EITHER TERMINAL THIS PD AS
POST FNTL FLW VEERS NWRLY AND STG LK SHADOWING COMMENCES THIS AFTN.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 8 AM EDT WEDNESDAY FOR LMZ043-046.

&&

$$

UPDATE...JT
SYNOPSIS...BENTLEY
SHORT TERM...SKIPPER
LONG TERM...JAL
AVIATION...T


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