492
FXUS63 KIWX 091521
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
1020 AM EST TUE FEB 9 2010
UPDATE
UPDATE TO GRIDS THIS MORNING TO ADJUST SNOW AMOUNTS SLIGHTLY BASED
ON LATEST RADAR TRENDS AND REPORTS. MANY AREAS REPORTING 1 TO 3
INCHES ALREADY. THE HIGHER AMOUNTS HAVE BEEN RATHER LOCALIZED AS WE
ARE SEEING OVERALL SMALL FLAKE SIZE WHICH IS REDUCING AMOUNTS BUT
OCCASIONAL HEAVIER POCKETS OF MODERATE TO BRIEFLY HEAVY SNOW
YIELDING THE HIGHER AMOUNTS. LATEST RADAR ANALYSIS INDICATES
HEAVIEST SNOW BAND ACROSS NORTHWEST OHIO AND EXTENDING SOUTHWEST
INTO CENTRAL INDIANA. THIS IN AN AREA OF STRONGER ISENTROPIC LIFT
AND WARM AIR ADVECTION WHICH SHOULD PERSIST IN FAR EAST THROUGH MID
AFTERNOON AND YIELD HIGHER AMOUNTS THERE. DRY SLOT ALREADY HAMPERING
SNOW IN WESTERN AREAS AND ESPECIALLY SOUTHWEST. DGZ NOT GREAT RIGHT
NOW AS IT REMAINS RATHER HIGH WITH LESS THAN OPTIMAL LIFT LEADING TO
OUR SMALL DENDRITES. STILL EXPECT A PROLONGED PERIOD OF LIGHT TO
MODERATE SNOW MOST AREAS WITH HEAVY SNOW CONFINED TO EAST THIS
AFTERNOON. AMOUNTS WILL BE LOWER IN THE SOUTHWEST NOW BUT STILL
EXPECT WARNING CRITERIA TOTAL AMOUNTS. DEFORMATION AND STRONG TROWAL
FEATURE LOOKS REASONABLE TONIGHT AND BUFKIT SOUNDINGS SUGGEST BETTER
DGZ OVERNIGHT. COUNTING ON THIS FOR LARGER FLAKE SIZE AND BETTER
ACCUMS OVERNIGHT. IN ADDITION...STRONG WINDS STILL EXPECTED WITH
DEEPENING LOW TO OUR EAST. WILL EVALUATE 12Z MODEL DATA FURTHER FOR
ADDITIONAL ADJUSTMENTS TO TONIGHT AND WEDNESDAY PERIODS. NO CHANGES
TO WARNING AREA PLANNED.
AVIATION /12Z TAFS/
IFR/LIFR CONDITIONS WILL DOMINATE THE NEXT 24 HOURS AS LOW
PRESSURE TRACKS UP THE OHIO VALLEY TODAY...NEARING CLEVELAND THIS
EVENING...BEFORE TRANSFERRING IT/S ENERGY TO A REDEVELOPING LOW
OFF THE ATLANTIC COAST. LIGHT TO OCCASIONALLY MODERATE SNOW IS
EXPECTED THROUGH THE TAF PERIOD...WITH THE HEAVIEST SNOWFALL
LIKELY FALLING FROM MID MORNING TODAY THROUGH THIS EVENING.
TONIGHT...WHILE SNOWFALL RATES MAY WEAKEN SOMEWHAT /PARTICULARLY
AT FWA/ WINDS WILL STRENGTHEN SUBSTANTIALLY WITH BLOWING SNOW
BECOMING AN ISSUE AFTER MIDNIGHT.
HAVE IFR VSBYS/MVFR CIGS DETERIORATING TO LIFR VSBYS AND IFR CIGS
DURING THE MORNING...WITH THESE CONTINUING INTO THE EVENING. WHILE
A PERIOD OF IFR VSBYS IS POSSIBLE THROUGH THE EVENING AT
FWA...EXPECT SBN TO REMAIN LIFR. AFTER MIDNIGHT...WITH BLOWING
SNOW DEVELOPING...EXPECT LIFR VSBYS WITH IFR CIGS TO CONTINUE
THROUGH THE END OF THE TAF PERIOD. SOME 1/4SM VSBYS ARE NOT OUT OF
THE QUESTION TOWARDS THE VERY END OF THE TAF PERIOD IN SNOW AND
BLOWING SNOW...BUT ARE MORE LIKELY AFTER 12Z WEDNESDAY.
EAST WINDS 10KTS TODAY WILL BACK NORTHEAST 10-15KTS THIS
AFTERNOON. WINDS WILL CONTINUE TO BACK NORTHERLY 14G22KTS THIS
EVENING BEFORE BECOMING NORTHWESTERLY AND INCREASING TO 20G28KTS
AFTER MIDNIGHT.
PREV DISCUSSION
/ISSUED 503 AM EST TUE FEB 9 2010/
SHORT TERM...
TODAY THROUGH WEDNESDAY NIGHT...A WELL DEFINED UPPER LOW ON THE
SATELLITE WATER VAPOR OVER SW IA WILL MERGE WITH A DEVELOPING SFC
LOW OVER MS. ISALLOBARIC ANALYSIS INDICATED LARGE PRESSURE FALLS
NORTH OF THE OHIO RIVER AND AHEAD OF THE UPPER LOW OVER IA. WARM
AIR ADVECTION WAS INCREASING OVER THIS AREA WITH SNOW
OVERSPREADING THE ENTIRE FORECAST AREA. THE GFS...NAM WRF AND THE
ECMWF CONTINUED WITH VERY GOOD RUN TO RUN CONSISTENCY WITH THE
TRACK OF THE UPPER LOW NORTH OF THE OHIO RIVER. THE TRAJECTORY OF
THE FORECAST TRACK OF THE 700 MB LOW CONTINUED TO BE OPTIMUM FOR
HEAVY SNOW OVER THE FORECAST AREA WITH THE BULK OF THE SNOW
FROM 09Z THIS MORNING TO 15Z WEDNESDAY. ALTHOUGH OMEGA VALUES NOT
PARTICULARLY IMPRESSIVE FOR THIS EVENT...THE OMEGA FIELD AND DGZ
INTERSECT VERY WELL...SO A PROLONGED EVENT WITH SNOW IS EXPECTED.
GFS 285K ISENTROPIC SFC INDICATE LIFT IN THE DENDRITIC ZONE WILL
BE OVER THE FORECAST AREA INTO WEDNESDAY... WITH THE DRY SLOT JUST
TO THE SOUTH. THE GARCIA METHOD SUPPORTS A BALLPARK 8-12 INCHES
WHICH HAS BEEN ADVERTISED FOR SEVERAL IWX FORECAST PACKAGES.
SLIGHTLY HIGHER AMOUNTS ARE EXPECTED OVER FAR SW LOWER MI INTO NW
INDIANA WHERE MODERATE TO HEAVY LAKE ENHANCED SNOW SHOWERS WILL
OCCUR. WINDS WILL INCREASE LATE TONIGHT INTO WEDNESDAY...CAUSING
BLOWING AND DRIFTING SNOW AND NEAR BLIZZARD CONDITIONS. TRIED TO
FINE TUNE THE LAKE ENHANCED SNOW SHOWERS LATE TONIGHT AND
WEDNESDAY. THE LATEST THINKING IS EVENT TOTAL SNOWFALL AMOUNTS
DOWNSTREAM OF LAKE MICHIGAN WILL BE IN THE 10 TO 15 INCH RANGE.
LONG TERM /THURSDAY THROUGH MONDAY/...
MUCH QUIETER WEATHER IS EXPECTED FOR THE EXTENDED FORECAST PERIOD
AND WHILE SOME SNOW CHANCES CAN/T BE RULED OUT THERE ARE NO
INDICATIONS THROUGH EARLY NEXT WEEK FOR ANY MAJOR STORMS.
PRIMARY CONTROLLING FEATURES THIS PERIOD WILL BE A WEAKLY POSITIVE
PNA PATTERN ALONG THE WEST COAST /FORCED BY LOW HEIGHT ANOMALIES
OVER THE GULF OF ALASKA / AND A MONSTROUS BLOCK CENTERED JUST SOUTH
OF GREENLAND...WHICH WILL BE REINFORCED EARLY THIS WEEK BY THE
COASTAL REDEVELOPMENT OF OUR TUESDAY/WEDNESDAY WINTER STORM. THIS
PATTERN SPELLS A PROLONGED PERIOD OF NORTHWEST FLOW ALOFT...WITH A
CONTINUOUS FLOW OF COLDER THAN NORMAL CONTINENTAL POLAR AIR.
ALSO...THERE WILL BE TWO SOURCE REGIONS FOR POTENTIAL WEATHER MAKERS
THROUGH THE PERIOD. FIRST WILL BE SHORTWAVES ROTATING AROUND THE
GULF OF ALASKA LOW. SECOND WILL BE A SHORTWAVE NOW LOCATED WEST OF
HUDSON BAY...NEAR THE LOCATION WHERE OUR CURRENT STORM SYSTEM WAS
LOCATED TWO DAYS AGO.
WITH THE BRISK NORTHWEST FLOW ALOFT THERE CONTINUE TO BE TIMING
DIFFERENCES ON EMBEDDED SHORTWAVES...WITH LOSS OF AGREEMENT ON A
SATURDAY SYSTEM AND NOW SOME INCREASING SUPPORT FOR A POTENTIAL
SYSTEM ON SUNDAY. THE FLOW TRAJECTORY THROUGH THE LOWER HALF OF THE
TROPOSPHERE INDICATES ANY SYSTEM WILL BE MOISTURE STARVED AND WELL
SEPARATED FROM THE SUPPRESSED SOUTHERN STREAM. FOR CONTINUITY...AND
COLLABORATION/S SAKE...AND DUE TO POOR AGREEMENT OVER THE PAST FEW
MODEL CYCLES...WILL CONTINUE GOING DRY FORECAST.
WHILE I FAVOR THE COOLER SURFACE THERMAL FIELDS FROM THE
GFS...BELIEVE TEMPS ALOFT WILL BE CLOSER TO A GFS/ECMWF MEAN...WHICH
SUGGESTS THAT LAKE-INDUCED INSTABILITY SHOULD NOT BE SUFFICIENT FOR
ANY LAKE EFFECT SHSN ACTIVITY...WITH THE LEVEL OF CLOUDINESS ALSO IN
QUESTION.
FOR THURSDAY...WITH TEMPS ALOFT WARMING...AGREE WITH PREVIOUS
SHIFT/S INCLUSION OF FLURRIES /BUT NO MORE/ FOR THIS PERIOD WITH
SOME LINGERING CLOUDS THAT SHOULD KEEP HIGH TEMPS IN CHECK. WILL
CONTINUE HIGHS IN THE LOWER/MID 20S.
WITH LAKE CLOUDINESS DIMINISHING THURSDAY NIGHT AND A FRESH SNOWPACK
IN PLACE...WILL CONTINUE WITH LOWS IN THE SINGLE DIGITS OVER
SOUTHERN AREAS WARMING TO THE LOWER TEENS DOWNWIND OF THE LAKE.
FOR THE FRIDAY THROUGH MONDAY PERIOD EXPECT A VERY GRADUAL INCREASE
IN HIGH TEMPS /MID-UPPER 20S/ ALTHOUGH HIGHS SHOULD REMAIN BELOW
NORMAL THROUGH THE PERIOD. WILL ALSO SLOWLY TREND LOWS UPWARD...BUT
DEPENDING ON THE AMOUNT OF LAKE-INDUCED CLOUD COVER...ADDITIONAL
NIGHTS IN THE SINGLE DIGITS TO AROUND ZERO ARE CERTAINLY POSSIBLE AS
LLEVEL FLOW WILL NOT BE ALL THAT STRONG.
IWX WATCHES/WARNINGS/ADVISORIES
IN...WINTER STORM WARNING UNTIL 7 PM EST /6 PM CST/ WEDNESDAY FOR
INZ003>009-012>018-020-022>027-032>034.
MI...WINTER STORM WARNING UNTIL 7 PM EST WEDNESDAY FOR MIZ077>081.
OH...WINTER STORM WARNING UNTIL 7 PM EST WEDNESDAY FOR OHZ001-002-004-
005-015-016-024-025.
LM...GALE WARNING FROM 7 PM THIS EVENING TO 11 PM EST WEDNESDAY FOR
LMZ043-046.
SHORT TERM...SKIPPER
LONG TERM...ARNOTT
AVIATION...ARNOTT
UPDATE...LASHLEY
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