914
FXUS63 KIND 091038
AFDIND
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
540 AM EST TUE FEB 9 2010
AVIATION
DISCUSSION FOR 091200Z TAF ISSUANCE. WIDESPREAD
IFR/AREAS LIFR DUE TO SNOW CURRENTLY ACROSS THE AREA. MODELS SUGGEST
MAIN FORCING WILL BE PASSING OFF TO THE NORTHEAST BY THE MID TO LATE
MORNING HOURS...SO SHOULD SEE SNOW INTENSITY TAPERING OFF AND A
RESULTANT IMPROVEMENT IN THE VISIBILITIES BY 091600Z OR SO...BUT
PREFER TO HOLD ONTO IFR CEILINGS UNTIL PASSAGE OF SURFACE TROUGH
AROUND MIDDAY. CEILINGS SHOULD LIFT INTO THE MVFR CATEGORY FOR A
TIME THIS AFTERNOON IN THE WAKE OF SURFACE TROUGH...BUT IFR
CONDITIONS IN SNOW SHOULD REDEVELOP AFT 092100Z WITH THE APPROACH OF
UPPER LOW.
SURFACE WINDS EXPECTED TO SHIFT AROUND TO 250-270 HEADINGS AS TROUGH
MOVES THROUGH IN THE 091600-091900Z TIME FRAME. TIGHTENING OF THE
PRESSURE GRADIENT LATER THIS AFTERNOON SUGGESTS SOME WIND GUSTS
AROUND 25 KTS PROBABLE IN THE WAKE OF TROUGH PASSAGE.
DISCUSSION
SNOW HAS SPREAD ACROSS OUR ENTIRE FORECAST AREA DURING THE EARLY
MORNING HOURS. RADAR LOOPS LAST SEVERAL HOURS SHOWS SNOW HAS BEEN
FILLING IN SOME TO OUR WEST AND SOUTH.
SURFACE ANALYSIS AT 07Z INDICATED A SURFACE LOW OVER WESTERN ALABAMA
WITH AN INVERTED TROUGH EXTENDING NORTH ACROSS ILLINOIS. WATER
VAPOR IR INDICATED THE STRONG UPPER LOW WAS OVER SOUTHWEST IOWA AND
IT WAS MOVING SOUTHEAST AND CLOUD TOPS WERE COOING EAST OF THE UPPER
LOW.
SNOW WILL CONTINUE THROUGH THE MORNING AS STRONG ISENTROPIC LIFT
CONTINUES ACROSS OUR REGION. MODELS TRACK THE UPPER LOW EAST ACROSS
SOUTH CENTRAL INDIANA THIS EVENING. THEY ALSO PUSH A DRY SLOT EAST
ACROSS SOUTHERN INDIANA THIS AFTERNOON AND DEVELOP A TROWEL ACROSS
THE SOUTHERN GREAT LAKES. THIS DRY SLOT SHOULD LIMIT SNOW AMOUNTS
ACROSS OUR SOUTHERN AREAS AND OUR SOUTHERN AREAS AND THIS WILL
PROBABLY KEEP SNOW AMOUNTS BELOW WARNING CRITERIA. WILL CHANGE THE
WINTER STORM WARNING TO A WINTER WEATHER ADVISORY IN OUR SOUTHWEST.
HPC GRAPHICS ONLY HAS 2 TO 3 INCHES ACROSS OUR SOUTHWEST...BUT THIS
SEEMS A BIT TOO LOW.
ELSEWHERE WILL LEAVE WINTER STORM WARNING INTACT...BUT I WILL TRIM
TOTAL SNOW AMOUNTS SLIGHTLY...EXCEPT IN THE FAR NORTH. AS FAR AS
TOTAL SNOW AMOUNTS WILL FORECAST 4 TO 5 INCHES ACROSS OUR
SOUTHWEST...AROUND 6 INCHES MOST OTHER AREAS BUT CLOSER TO 9 INCHES
ACROSS OUR FAR NORTH.
MODELS ARE IN PRETTY GOOD AGREEMENT AND WILL USE BLEND. SURFACE
LOW WILL TRACK NORTH ACROSS THE OHIO VALLEY AND ACROSS WESTERN OHIO
THIS EVENING. MODELS INDICATE A STRONG PRESSURE GRADIENT BEHIND THE
LOW. WINDS WERE SOMEWHAT HIGHER THAN MOS NUMBERS WITH THE LAST
SYSTEM AFTER THE LOW MOVED BY...SO WILL TWEAK UP A LITTLE. THIS
SHOULD PRODUCE QUITE A BIT OF BLOWING AND DRIFTING SNOW AS SNOW WILL
BE MORE POWDER LIKE THIS TIME AROUND AS TEMPERATURES ARE COLDER.
LONG TERM.../THURSDAY THROUGH MONDAY/
ECM AND GFS RELATIVELY CLOSE. THIS INDICATES A SLIGHT CHANCE OF SNOW
FRIDAY NIGHT INTO SATURDAY AS WEAK CLIPPER SYSTEM PASSES. HPC POPS
CAPTURE THIS...BUT IT IS NOT HIGHLIGHTED IN THEIR GRAPHIC
SINCE POPS STILL BELOW CLIMATOLOGY. OTHERWISE ECM...GFS...AND HPC IN
DECENT AGREEMENT ABOUT DRY PERIOD AND DID NOT CHANGE THAT.
FOR TEMPERATURES...THICKNESS AND PROBABILITY OF CONSIDERABLE SNOW
COVER SUGGEST HPC A LITTLE HIGH DURING DAYS. ALSO ECM HAS BEEN
PREFORMING THE BEST LATELY AND IS A LITTLE COLDER THAN GFS.
CONSIDERING THESE...ENSEMBLE AVERAGE DAYTIME TEMPERATURES SEEMED
BEST AND SHADED TOWARD THOSE.
FOR LOWS...ENSEMBLE AVERAGE WAS RELATIVELY CLOSE TO MEX/HPC. LOWS
WILL BE VERY SENSITIVE TO BOTH CLOUDS AND WINDS AND HARD TO MAKE
INTELLIGENT CHANGES TO GUIDANCE. STAYED CLOSE TO HPC ON MINIMUMS.
IND WATCHES/WARNINGS/ADVISORIES
WINTER STORM WARNING UNTIL 1 PM EST WEDNESDAY FOR INZ021-028>031-
035>049-054>057-062>065-070>072.
WINTER WEATHER ADVISORY UNTIL 1 PM EST WEDNESDAY FOR INZ051>053-
060-061-067>069.
AVIATION...JAS
SHORT TERM...JH
LONG TERM...RYAN
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