-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPBZ 241016
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
516 AM EST TUE FEB 24 2015

.SYNOPSIS...
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A REINFORCING COLD FRONT WILL MOVE THROUGH TUESDAY NIGHT WITH
LIGHT SNOW MAINLY NORTH OF PITTSBURGH. BELOW AVERAGE TEMPERATURES
WILL REMAIN THROUGH THE WEEK.
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&&

.NEAR TERM /THROUGH TONIGHT/...
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...BITTERLY COLD TEMPERATURES THROUGH MID-MORNING...

CURRENT IR SATELLITE IMAGERY SHOWING CLEAR SKIES ACROSS THE
CWA. THE CLEAR SKIES...CALM WINDS...AND SIGNIFICANT DRY AIR HAVE
COMBINED FOR YET ANOTHER ROUND OF TEMPERATURES AT OR BELOW ZERO
FOR MOST LOCATIONS. SEVERAL LOCATIONS...MAINLY NORTH OF PITTSBURGH
ARE ALREADY AROUND -20F. SOME OF THE WARMER LOCATIONS AT THIS HOUR
ARE THE URBAN HEAT ISLAND OF DOWNTOWN
PITTSBURGH...MORGANTOWN...AND SELECT LOCATIONS IN THE HIGHER
ELEVATIONS THAT ARE ABOVE THE INVERSION. ALTHOUGH THESE AREAS ARE
WARMER...THEY STILL REMAIN NEAR 0F.

WITH A FEW MORE HOURS OF COOLING TO GO...EXPECT TEMPERATURES TO
CONTINUE CREEPING DOWNWARDS. THE ONLY RELIEF IN SIGHT IS A THIN
VEIL OF HIGH CIRRUS THAT MAY SKIRT OUR NORTHWEST ZONES BY
12Z...WHICH COULD HELP CURTAIL SOME OF THE RADIATIONAL COOLING.
OTHERWISE...TEMPERATURES WILL STAY BITTERLY COLD UNTIL MIXING
BEGINS TO KICK IN NEAR SUNRISE. WINDS HAVE BEEN CALM THROUGH THE
NIGHT...BUT AS WE BEGIN TO MIX AND RE-COUPLE THE ATMOSPHERE...THERE
WILL BE A SEVERAL HOUR WINDOW WHERE THE COLD TEMPERATURES WILL
COMBINE WITH THE RELATIVELY LIGHT 5-10KT WINDS TO KEEP WIND CHILLS
BELOW NEGATIVE 10F. THINKING IT WILL TAKE A FEW MORE HOURS FOR
THIS TO OCCUR THAN PREVIOUSLY FORECAST...SO THE WIND CHILL
ADVISORY HAS BEEN EXTENDED UNTIL 11AM.

UNLIKE THE REMARKABLE COLD OF LAST WEEK...WHERE NEAR RECORD 850MB
TEMPERATURES WERE SAMPLED...THE LOW-LEVEL TEMPERATURES ABOVE THE
CURRENT INVERSION ARE ACTUALLY MUCH WARMER. IN FACT...SINCE 00Z
THE 850MB TEMPERATURES HAVE RISEN NEARLY 7C AS WARM AIR ADVECTION
TAKES PLACE ABOVE THE INVERSION. THIS SHOULD PROVIDE A GLIMMER OF
HOPE ACROSS OUR FROSTY LANDSCAPE AS A RELATIVELY QUICK WARM-UP IS
POISED TO OCCUR. INCREASINGLY STRONG LATE FEBRUARY SUNSHINE AND
ENHANCED SOUTHERLY FLOW SHOULD EFFECTIVELY ERADICATE THE COLD
AIR AND REBOUND DAYTIME HIGHS NICELY. DIURNAL RANGES COULD BE 30 TO 40
DEGREES TODAY.

TONIGHT...YET ANOTHER COLD FRONT WILL ARRIVE TO REINFORCE THE
BELOW AVERAGE TEMPERATURES. MID- AND UPPER-LEVEL MOISTURE
COMPLETELY OVERRUNS THE LOW-LEVEL FRONT AND ASSOCIATED MOISTURE.
THIS WILL HELP TAKE THE PUNCH OUT OF AN ALREADY RELATIVELY DRY
FRONT. CLOUDS WILL OVERSPREAD THE FORECAST AREA THIS
AFTERNOON/EVENING...FOLLOWED BY LIGHT SNOW SHOWERS. THE BEST
FORCING AND DEEPEST MOISTURE STAYS WELL TO OUR NORTH...BUT OUR
NORTHERN ZONES SHOULD SEE A AT LEAST A FEW HOURS OF LIGHT SNOW.
SNOW GENERATION SHOULD BE FAIRLY EFFICIENT WITH SNOW RATIOS
PROGGED AT 15 OR 20 TO 1. ALL TOLD 0.5 TO 1" IS POSSIBLE ALONG AND
NORTH OF I-80. MOISTURE DEPTH REALLY DROPS OFF NEAR PITTSBURGH AND
SOUTH...SO CONFIDENCE IN MEASURABLE SNOWFALL IS NOT HIGH. LOWS
TONIGHT WILL BE CONSIDERABLY WARMER THAN CURRENT
TEMPERATURES...BUT THATS NOT SAYING MUCH.
TAX
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&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
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EXPECT THE SURFACE FRONT TO BE ACROSS THE RIDGES BY 12Z
WEDNESDAY...BUT COLDER AIR WILL LAG THE BOUNDARY A BIT AND NOT
ARRIVE IN EARNEST UNTIL LATER IN THE DAY.  LOW LEVEL NW FLOW AND
MOISTURE IN THE DENDRITIC GROWTH LAYER WILL ALLOW SOME ISOLATED SHSN
TO CONTINUE THROUGH MIDDAY...WITH ONLY AN ADDITIONAL LIGHT COATING
OF SNOW AT MOST.  AFTERNOON CLEARING WILL BE SHORT-LIVED...AS
MIDLEVEL FLOW SETTLES TOWARDS THE WEST AND THEN SOUTHWEST WEDNESDAY
NIGHT...PULLING MID AND HIGH CLOUDS BACK INTO THE REGION.

UPPER LOW EJECTS OUT OF THE SOUTHWEST U.S. TONIGHT AND TRACKS ACROSS
THE SOUTHERN STATES...BEFORE SWINGING ACROSS THE CAROLINAS AS A
SHEARING WAVE INTO THURSDAY MORNING.  NAM KEEPS A SHARPER WAVE AND
MORE NORTHERLY LOW THAN OTHER MODELS...WHICH ARE A LITTLE MORE
SUPPRESSED.  WHILE THIS IS HAPPENING...ENERGY DROPS FROM THE
NORTHERN PLAINS INTO THE SOUTHERN GREAT LAKES INTO FRIDAY...WHICH
DRAGS ANOTHER ARCTIC FRONT TOWARDS US.  AHEAD OF THE
FRONT...MOISTURE GETS INTO THE REGION IN DEEP SW FLOW.  MODELS SEEM TO
BE STRUGGLING WITH DETAILS...BUT SLIGHTLY INCREASED CONFIDENCE IN
PRECIP LED TO CHANCE POPS AREAWIDE FOR THURSDAY AND THURSDAY NIGHT.
STILL APPEARS TO BE A LOW QPF EVENT...WITH PERHAPS AN INCH OF SNOW
IN SOME LOCATIONS.  HIGH PRESSURE BRIDGES IN FROM THE MISSISSIPPI
VALLEY ON FRIDAY...WITH DRY WEATHER. BELOW ZERO READINGS EXPECTED
AGAIN THURSDAY NIGHT...WITH HIGHS STILL IN THE TEENS ON FRIDAY.  CL
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&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
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DRY WEATHER CONTINUES THROUGH FRIDAY NIGHT AND SATURDAY.  AFTER
ANOTHER FRIGID NIGHT...SW RETURN FLOW BEHIND HIGH ON SATURDAY SHOULD
ALLOW FOR SOME TEMPERATURE MODERATION.  PATTERN MUDDIES THEREAFTER
AS MAIN BAROCLINIC ZONE SETS UP SHOP IN OR JUST SOUTH OF OUR REGION
FROM SUNDAY INTO EARLY NEXT WEEK.  MOIST SW FLOW AND A FEW
SHORTWAVES WILL PROVIDE OPPORTUNITIES FOR PRECIPITATION...THE BEST
OF WHICH APPEARS TO BE SUNDAY NIGHT INTO MONDAY AT PRESENT TIME.
PRECIPITATION TYPE REMAINS UNCERTAIN THROUGH THIS PERIOD.  ENSEMBLES
LIKELY WOULD PROVIDE THE PATH OF LEAST REGRET AT THIS POINT.
NEVERTHELESS...THE RISING H500 HEIGHTS POINT TO TEMPERATURES AT
LEAST GETTING WITHIN THE REALM OF SEASONABLE VALUES BY THE END OF
THE EXTENDED PERIOD.  CL
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&&

.AVIATION /09Z TUESDAY THROUGH SATURDAY/...
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MAINLY CLEAR SKIES WILL CONTINUE AS DRY AIR ADVECTS IN WITH
NORTHWEST FLOW. VFR IS EXPECTED TO CONTINUE THROUGH TUESDAY WITH
HIGH PRESSURE OVER THE GREAT LAKES. TONIGHT ANOTHER RELATIVELY DRY
COLD FRONT WILL APPROACH FROM THE NORTHWEST. EXPECTING LOW MVFR
CIGS WITH THE FRONT. SNOW SHOULD REMAIN MOSTLY LIGHT...BUT ANY
INDIVIDUAL MODERATE SNOW BANDS MAY REDUCE VISIBILITIES AT TIMES TO
BELOW MVFR. CONFIDENCE IN TIMING AND LOCATION NOT HIGH ENOUGH FOR
INCLUSION OF SUB-MVFR RESTRICTIONS AT THIS TIME. TAX

OUTLOOK.../TUESDAY NIGHT THROUGH SATURDAY/...
RESTRICTIONS ARE POSSIBLE AREA WIDE WITH A LATE THURSDAY DISTURBANCE
SOUTH OF PIT.
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&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
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MD...WIND CHILL ADVISORY UNTIL 11 AM EST THIS MORNING FOR MDZ001.
OH...WIND CHILL ADVISORY UNTIL 11 AM EST THIS MORNING FOR
     OHZ039>041-048>050-057>059.
PA...WIND CHILL ADVISORY UNTIL 11 AM EST THIS MORNING FOR
     PAZ007>009-013>016-020>023-029-031-073>076.
WV...WIND CHILL ADVISORY UNTIL 11 AM EST THIS MORNING FOR
     WVZ001>004-022-023-041.
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&&

$$