Ice Storm and Heavy Snow in Pennsylvania, February 13 to 14, 2007

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
202 AM EST TUE FEB 13 2007

.SHORT TERM /TODAY THROUGH WEDNESDAY/...
NOT MANY CHANGES TO CURRENT FORECAST AS WHAT WE HAVE GOING IS VERY
REASONABLE. THERE ARE SOME IMPACT DIFFERENCES WITH LATEST MODEL
RUNS.

BOTH MODELS ARE SHOWING THE COLDER AIR HOLDING LONGER ACROSS
THE AREA. THIS IS SETTING UP CURRENTLY AS DRIER AIR WITH LOWER TADS
IS SLOWLY MOVING SOUTHWARD ACROSS THE AREA. RADAR IMAGES SHOWS
BROAD AREA OF SNOWFALL OVER MY SOUTHERN ZONES...HOWEVER ALMOST
ALL OF IT IS EVAPORATING BEFORE IT REACHES THE GROUND. WILL TAKE
SOME TIME TO MOISTEN UP THE LOWER LEVELS WITH THE LOW TADS.

THE COLDER SOLUTION TO MODELS SHOULD MEAN HIGHER SNOWFALL TOTALS
AND ALSO GREATER THREAT FOR ICE PROBLEMS IN MY SOUTH. SNOW SHOULD
OVERSPREAD THE ENTIRE AREA BY LATE MORNING WITH SNOWFALL RATES
INCREASING ACROSS THE SOUTH AT THIS TIME. HAVE PUSHED BACK ONSET
OF MIXING JUST A BIT TO ACCOUNT FOR COLDER AIR IN THE BL. WILL
KEEP MENTION OF ZR TO THE SOUTH OF PIT THROUGHOUT THE ENTIRE
FORECAST PERIOD. CURRENT FORECAST SOUNDINGS SHOW WARM LAYER
DEVELOPING LATE THIS AFTERNOON AND SLOWLY MOVING NORTHWARD AND
REACHING PIT AROUND 00Z. SOUTH OF PIT THIS LAYER IS WARMER AND
LARGER ALLOWING FOR MORE OF A ZR SITUATION HOWEVER ACROSS PIT THE
LAYER REMAIN AROUND 5000FT AND BELOW THIS WELL BELOW FREEZING
TEMPS. THIS APPEARS TO BE A CLASSIC PL SOUNDING WHICH WILL
PROVIDE A LAYER OF ICE ON TOP OF THE SNOW.

ONCE THE MIXING BEGINS...SNOWFALL ACCUMULATIONS WILL BE GREATLY
SHAVED. FURTHER NORTH THE CHANGE OVER WILL TAKE LONGER...WITH THE
NORTHERN MOST TIER MORE THAN LIKELY NEVER SEEING THIS CHANGE OVER.

CSI BANDING A GOOD POSSIBILITY TODAY WITH TIGHT THERMAL GRADIENT
INTO THE EVENING HOURS. WITH 85H LOW HEADING DIRECTLY TOWARD THE
AREA WILL PROVIDE ADDITIONAL LIFT INTO TONIGHT. AT THE SFC
EVERYTHING STILL POINTING TOWARD COASTAL SYSTEM DEVELOPING RAPIDLY
AFTER MIDNIGHT. ONCE THIS COASTAL SYSTEM GET GOING COLDER AIR WILL
RAPIDLY FILL INTO THE AREA TURNING ANY MIX BACK TO SNOW BY 12Z
WED. GOOD WRAP AROUND SNOWFALL STILL POSSIBLE INTO WED AFTERNOON
SO ADDITIONAL ACCUMULATIONS ARE EXPECTED.

BOTTOM LINE HIGHEST ACCUMULATIONS EXPECTED ACROSS FAR NORTHERN
TIER WITH GOOD CHANCE OF ICE ACCUMULATIONS ACROSS THE FAR SOUTH.
IN BETWEEN...GOOD SNOW ACCUMULATIONS WITH A COATING OF ICE OVER
TOP POSSIBLE.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
BY WEDNESDAY NIGHT...STORM IS RAPIDLY HEADING TOWARD MAINE AND
SHOULD BRING AN END TO ANY LINGERING SNOW SHOWERS. THE ARCTIC AIR
OVER THE PAST COUPLE OF WEEKS HAS PROVIDE ICE ON THE LAKES WHICH
WILL MAKE ANY LES WED NIGHT AND THU LESS OF A THREAT IN THE SOUTH.
COLD AIR TAKES HOLD ONCE AGAIN THROUGH THE WEEKEND. CLIPPER SYSTEM
EXPECTED ON SATURDAY WITH SOME ADDITIONAL LIGHT ACCUMULATIONS
POSSIBLE.

&&

.AVIATION /07Z-06Z/...
RECENT GFS AND NAM-WRF MODEL RUNS CONTINUE TO SHOW STRONG
ISENTROPIC LIFT DEVELOPING ALONG THE STRONG LOWLEVEL TEMPERATURE
GRADIENT OVER THE UPPER OHIO VALLEY TODAY AND TONIGHT IN CONJUNCTION
WITH THE ONSET OF THE DEVELOPING LOW PRESSURE SYSTEM. HENCE, EXPECT
FLIGHT CONDITIONS TO LOWER INTO THE IFR RANGE 11Z-14Z. LOWEST
CONDITIONS SHOULD BE NORTH THIS AFTERNOON AND EARLY TONIGHT WHEN
SNOWFALL INTENSITY IS GREATEST.

FROM KPHD-KPIT SOUTH...THERE WILL BE A CHANGEOVER TO ICE PELLETS AND
FREEZING RAIN THIS AFTERNOON AND TONIGHT, BASED ON NAM-WRF
SOUNDINGS. VISIBILITIES IN THIS ZONE MAY THEN GO MVFR.

WINDS WILL BECOME MORE EASTERLY TODAY AND TONIGHT 10-17KTS.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...WINTER STORM WARNING FROM 5 AM EARLY THIS MORNING TO 6 PM EST
     WEDNESDAY FOR MDZ001.

OH...WINTER STORM WARNING FROM 5 AM EARLY THIS MORNING TO 6 PM EST
     WEDNESDAY FOR OHZ039>041-048>050-057>059-068-069.

PA...WINTER STORM WARNING FROM 5 AM EARLY THIS MORNING TO 6 PM EST
     WEDNESDAY FOR PAZ007>009-013>016-020>023-029>032.

WV...WINTER STORM WARNING FROM 5 AM EARLY THIS MORNING TO 6 PM EST
     WEDNESDAY FOR WVZ001>004-012-021>023-041.

&&

22/22/11/

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE PITTSBURGH PA
322 AM EST TUE FEB 13 2007

MDZ001-OHZ039>041-048>050-057>059-068-069-PAZ007>009-013>016-
020>023-029>032-WVZ001>004-012-021>023-041-140830-
GARRETT-TUSCARAWAS-CARROLL-COLUMBIANA-COSHOCTON-HARRISON-
JEFFERSON OH-MUSKINGUM-GUERNSEY-BELMONT-NOBLE-MONROE-MERCER-
VENANGO-FOREST-LAWRENCE-BUTLER-CLARION-JEFFERSON PA-BEAVER-
ALLEGHENY-ARMSTRONG-INDIANA-WASHINGTON-WESTMORELAND-GREENE-
FAYETTE-HANCOCK-BROOKE-OHIO-MARSHALL-WETZEL-MARION-MONONGALIA-
PRESTON-TUCKER-
322 AM EST TUE FEB 13 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF WESTERN
MARYLAND...EAST CENTRAL OHIO...NORTHWEST PENNSYLVANIA...SOUTHWEST
PENNSYLVANIA...WEST CENTRAL PENNSYLVANIA...NORTHERN WEST VIRGINIA
AND NORTHERN PANHANDLE OF WEST VIRGINIA.

.DAY ONE...TODAY AND TONIGHT
NATIONAL WEATHER SERVICE PITTSBURGH HAS A HEAVY SNOW WARNING FOR
THE INTERSTATE 80 CORRIDOR AND A WINTER STORM WARNING FOR THE REST
OF THE UPPER OHIO VALLEY. SNOW AMOUNTS CAN GO OVER 6 INCHES NORTH
OF INTERSTATE 70 AND ON THE HIGHER MOUNTAINS. SOUTH OF INTERSTATE
70...THERE CAN BE A THICK COATING OF ICE. TRAVEL WILL BE DIFFICULT.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY
NATIONAL WEATHER SERVICE PITTSBURGH SAYS THE HEAVY SNOW WARNING
FOR THE INTERSTATE 70 CORRIDOR AND WINTER STORM WARNING FOR THE
REST OF THE UPPER OHIO VALLEY WILL CONTINUE INTO LATE WEDNESDAY
AFTERNOON. BY WEDNESDAY MORNING...THE PRECIPITATION WILL TURN ALL
TO SNOW ACROSS THE UPPER OHIO VALLEY. BRISK WINDS WILL CAUSE
DRIFTING AND BLOWING SNOW. TRAVEL WILL REMAIN DIFFICULT INTO
WEDNESDAY NIGHT.

ON THURSDAY AND FRIDAY...SUBZERO WIND CHILL CAN OCCUR.

.SPOTTER INFORMATION STATEMENT...
THE SPOTTER NET HAS BEEN ACTIVATED. SKYWARN SPOTTERS SHOULD CALL
WITH EACH NEW 2 INCH SNOW ACCUMULATION. ALSO REPORT ICE
ACCUMULATIONS OF MORE THAN ONE EIGHTH INCH THICKNESS.