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000
FXUS63 KIWX 230057
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
857 PM EDT WED MAY 22 2013

.SYNOPSIS...
ISSUED AT 508 PM EDT WED MAY 22 2013

A LOW PRESSURE SYSTEM CURRENTLY MAKING ITS WAY THROUGH THE REGION
WILL MOVE OFF INTO SOUTHERN ONTARIO TONIGHT. A WEAK COOL FRONT
WILL TRAIL TO THE SOUTH OF THE LOW AND MOVE EAST ACROSS SOUTHERN
MICHIGAN... INDIANA... AND MOST OF OHIO BY THURSDAY MORNING...
WHILE A SECOND STRONGER COLD FRONT DROPS SOUTH ACROSS THE UPPER
GREAT LAKES. SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED
ALONG AND AHEAD OF THE FIRST COOL FRONT...WHILE SCATTERED SHOWERS
MAY ACCOMPANY THE SECOND COLD FRONT.

&&

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 321 PM EDT WED MAY 22 2013

UPPER LOW CURRENTLY OVER S MN/N IA WILL CONTINUE TO
DROP SE INTO UPPER GREAT LAKES WITH ASSOCIATED SURFACE LOW OVER N IL
MOVING EAST ACROSS LWR MI THIS AFTERNOON INTO SOUTHERN ONTARIO BY
THURS MORNING. FIRST OF TWO COLD FRONTS IS CURRENTLY PROGRESSING
EASTWARD TOWARD NW IN THIS AFTERNOON. SHOWERS AND ISOLATED
THUNDERSTORMS HAVE FIRED AHEAD OF FRONT IN AREAS OF PARTIAL CLEARING
AS UPPER LVL VORT MAX ROTATES AROUND BASE OF TROF. ALTHO LL SHEAR
AND PWAT VALUES ARE DECENT...MEAGER DESTABILIZATION HAS OCCURRED
WITH WEAK MID LVL LAPSE RATES AND IS PREVENTING OVERALL
ORGANIZATION TO CONVECTION. LATEST HIRES MODELS HAVE CAPTURED
THIS FAIRLY WELL. THIS SHOULD LIMIT SEVERE POTENTIAL THIS
AFTERNOON INTO EVENING ACROSS MOST OF THE AREA WITH BEST FORCING
AND POTENTIAL TO THE FAR EAST OF CWA ACROSS EASTERN OH/WESTERN PA.
CANNOT RULE OUT A STRAY STRONG TO SEVERE STORM WITH GUSTY WINDS
BUT SUSPECT THIS IS LOW PROBABILITY. SCT SHOWERS WILL CONTINUE
OVERNIGHT TONIGHT INTO THURS BEFORE TAPERING OFF FROM WEST TO EAST
BY THURS EVENING AS SECONDARY COLD FRONT MOVES THRU. HAVE ONLY
MADE MINOR CHANGES TO POPS/WX GRIDS LATE TONIGHT INTO THURS.
GRADIENT IN TEMPS TONIGHT WITH LOWS AROUND 50 NEAR LK MI AND NEAR
60 IN THE SE. HIGHS WILL BE AROUND 10 TO 15 DEG COOLER ON THURS AS
COOLER AIR MOVES IN FROM THE NW BEHIND 2ND COLD FRONT.

&&

.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 321 PM EDT WED MAY 22 2013

HIGH LATITUDE BLOCKING EXPECTED FRIDAY INTO THE HOLIDAY WEEKEND WITH
UPPER TROUGHS SETTING UP ALONG THE COASTS WITH AN OMEGA-LIKE UPPER
RIDGE ACROSS CENTRAL NORTH AMERICA. THIS WILL PLACE THE IWX CWA IN
COOL NORTHWEST FLOW ALOFT WITHIN DOWNSTREAM PORTION OF LARGE CENTRAL
CONUS UPPER RIDGE. DRY/BENIGN WX IS ANTICIPATED FRIDAY THROUGH
SUNDAY WITH SFC HIGH ANCHORED OVER THE GREAT LAKES AND ACTIVE LOW
LEVEL BAROCLINIC ZONE DISPLACED WELL WEST-SOUTHWEST OF THE LOCAL
AREA.

UPPER RIDGE WILL SHIFT EAST OVER THE AREA NEXT WEEK IN RESPONSE TO A
STRONG EAST PACIFIC JET CORE FORECAST TO INFILTRATE THE WESTERN US.
THIS WILL SUPPORT A SUBSTANTIAL MODERATING TREND MONDAY THROUGH
WEDNESDAY. MODELS TRY TO MIX THE INCREASINGLY DIFFUSE FRONTAL
BOUNDARY NORTH THROUGH THE AREA SOMETIME AROUND TUESDAY OR
WEDNESDAY...WITH THE GFS QUICKER/MORE PROGRESSIVE THAN THE PREFERRED
ECMWF SOLUTION. AS A RESULT CONTINUED TO HOLD WITH PREVIOUS DRY FCST
MONDAY AND TUESDAY AND ADDED LOW CHC POPS FOR SHOWERS/STORMS ON
WEDNESDAY. ONLY MADE MINOR TWEAKS TO TEMPS THROUGH THE PERIOD AS
FAVOR WARMER MOS HIGHS OVER THE 12Z MODEL CONSENSUS INITIATION.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z THURSDAY EVENING)
ISSUED AT 855 PM EDT WED MAY 22 2013

WELL STABILIZED ATMOS IN WAKE OF SURFACE FRONTAL PASSAGE WITH LITTLE
MORE THAN WEAK SHRA REMAINDER OF NIGHT. CONCERN WITH STRATUS
FORMATION TOWARD DAYBREAK AS COOLING BOUNDARY LAYER CONTINUES TO
DEEPEN. STRONG PERTURBATION WITHIN SATURATED LAYER AS UPSTREAM MID
TROPOSPHERIC OCCLUDED LOW ACROSS EASTERN IOWA LIFTS OUT ACROSS
SOUTHERN GREAT LAKES. DETERIORATING CONDITIONS MOST LIKELY INTO FUEL
ALTERNATE BY 10 UTC ACROSS NORTHERN INDIANA WITH IFR MET CONDITIONS
EVEN PROBABLE AT KSBN WITH GREATER MAGNITUDE COOLING BELOW CROSSOVER
TEMPERATURE AND POTENTIAL MARINE LAYER INFLUENCE GIVEN STRONG
ONSHORE COMPONENT WITHIN LOWEST 100 MB IN 10-14 UTC TIMEFRAME.
CONTINUED 925MB COLD AIR ADVECTION WITH STRONG ISOTHERMAL GRADIENT
ALIGNED WITH SURFACE TROF AXIS THROUGH SOUTHERN ONTARIO TO
CHICAGOLAND AT 12 UTC THAT WILL SHUNT SEWD AMID 1030 MB SURFACE HIGH
ACROSS SOUTHERN CANADA INTRUDES INTO NW GREAT LAKES BY END OF
FORECAST PERIOD. INCREASINGLY SUBSIDENT AIRMASS WITH DRY AIR
ENTRAINMENT TO HELP BREAK/LIFT INTO BKN HIGH END MVFR CU DECK BY MID
AFTERNOON.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...GALE WARNING FROM 10 AM TO 8 PM EDT THURSDAY FOR LMZ043-046.

&&

$$

SYNOPSIS...CEO/KG
SHORT TERM...CEO
LONG TERM...STEINWEDEL
AVIATION...MURPHY


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