475
FXUS63 KIWX 121051
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
651 AM EDT MON MAY 12 2008
AVIATION
MAINLY VFR XPCD THROUGH THE PD. HWVR PESKY BORDERLINE IFR/MVFR CIGS
STILL CONT TO ADVT SWD WITHIN MOIST BNDRY LYR UNDERNEATH SHARPENING
POST FNTL INVERSION. CLEARLY OBSERVATIONAL TRENDS DICTATE LOW STRATUS
WEDGE WILL EXPAND/DROP SEWD AND OVERSPREAD BOTH TERMINALS FOR
SOMETIME THIS MORNING AND WILL HAVE TO MAKE AMENDS W/12Z ISSUANCE.
HWVR STILL XPC IMPROVEMENT THIS AFTN W/CONTD SUBSIDENCE EROSION ESP
AT KSBN W/LK SHADOW THIS AFTN. KFWA WILL REMAIN IN MOIST CYCLONIC
FLW LONGER W/EVENTUAL CIG PUSH INTO VFR MID AFTN W/CLRG HOLDING OFF
TWD EVENING.
GUSTY WINDS THIS MORNING WILL CONT TO DIMINISH THROUGH THE DAY.
SHORT TERM
SFC OCCLUSION OVR ERN OH CONTS TO WEAKEN W/COASTAL CYCLOGENESIS WELL
UNDERWAY AND RAPID BREAKDOWN OF OLD LARGE SCALE DEFORMATION ZONE
NOTED THIS MORNING AND END OF RAIN ACRS NW OH. INCREASING SUBSIDENCE
ALOFT WEST OF MID LVL TROUGH AXIS HAD ERODED LOW CLOUD DECK YET
ENOUGH RESIDUAL LEFT OVR TO CU BACK UP AFT MORNING SUN EAST HALF.
OTHERWISE SFC RIDGING BLDG EWD THIS AFTN WILL RESULT IN DIMINISHING
GRADIENT WINDS. PRIMARY NR TERM PROB WILL BE INLAND EXTENT OF LK
SHADOW ESP W/HEATING GIVEN CONT LL NW FLW TRAJECTORY AND PRETTY MUCH
BUTCHERED TEMPS ACRS LAPORTE/BERRIEN TO REFLECT LIKELY PNEUMONIA
FRONT THERE.
SFC RIDGE PASSED OVERNIGHT W/AT LEAST WK RTN FLW BY MORNING
W/INCREASING HIGH CLDS SPILLING OUT OF THE PLAINS INADV OF TROUGH
BREAKING ACRS THE ROCKIES THIS MORNING. WILL KEEP W/COOLER SPECTRUM
OF GUIDANCE NUMBERS GIVEN CLR SKIES AND QUICK DECOUPLING XPCD THIS
EVENING WITHIN SFC RIDGE AXIS.
STG WAA DVLPS ON TUE AHD OF FAST MOVING NRN STREAM TROUGH SHIFTING
OUT OF THE PLAINS AND LOOKS LIKE THE WARMEST DAY OF THE WEEK. STG
LLJ AIDES THETA-E SURGE OUT OF SRN PLAINS TUE NIGHT IN RESPONSE TO
AMPLIFYING TROUGH AND JET STREAK CROSSING SRN LAKES LATE AHD OF
CDFNT AND BUMPED POPS HIGHER LATE.
LONG TERM
WEDNESDAY THROUGH SUNDAY...A COLD FRONT SHOULD BE MOVING INTO THE
AREA WEDNESDAY...BUT MOISTURE FLUX INTO NORTHERN INDIANA AND NW OH
APPEARS MARGINAL. KEPT A CHANCE FOR THUNDER BUT SEVERE NOT
ANTICIPATED WITH FORECAST CAPES LESS THAN 500 J/KG. FOR THIS
PACKAGE...REFINED TIMING OF PRECIPITATION WEDNESDAY AND WEDNESDAY
EVENING TO COINCIDE WITH FROPA. PRECIPITATION SHOULD END BY MIDNIGHT
WEDNESDAY NIGHT AS HIGH PRESSURE BUILDS INTO THE REGION. PREFER THE
ECMWF/CANADIAN GEM/UKMET FOR THE REST OF THE FORECAST. THE 00Z GFS
APPEARS TO BE AN OUTLIER OVERDEVELOPING AN UPPER LOW DOWNSTREAM OF
THE MAIN RIDGE. THEREFORE...REMOVED RAIN CHANCES THURSDAY NIGHT.
SUBSEQUENT SHIFTS MAY NEED TO REMOVE RAIN CHANCES FRIDAY WITH
SFC RIDGE PERSISTING OVER THE AREA. CPC AND ANALOG SIGNALS ACROSS
THE BOARD SUPPORT A DEEP NEGATIVE HEIGHT ANOMALY INTO THE WESTERN
GREAT LAKES REGION THIS WEEKEND. THE ECMWF 700 MB FCST TEMPS RANGE
FROM -7C TO -11C SATURDAY EVENING INTO SUNDAY. BELIEVE WITH STEEP
LAPSE RATES AND A DEEP UPPER LOW EVENTUALLY DROPPING INTO THE REGION
THAT SHOWERS AREA POSSIBLE. TEMPERATURES SHOULD BE WELL BELOW
NORMAL...WITH READINGS POSSIBLY BEING HELD IN THE 50S.
IWX WATCHES/WARNINGS/ADVISORIES
IN...NONE.
MI...NONE.
OH...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 4 PM EDT MONDAY FOR LMZ043-046.
SHORT TERM...HOLSTEN
LONG TERM...SKIP
AVIATION...HOLSTEN
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