Winter Storm Warning 9, NWS Pittsburgh, PA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
301 AM EST SUN DEC 5 2010

.SYNOPSIS...
A SERIES OF DISTURBANCES IN COLD NORTHWEST FLOW WILL SUPPORT
PERIODS OF SNOW SHOWERS THROUGH TUESDAY, WITH SIGNIFICANT SNOW
ACCUMULATIONS EXPECTED NORTH OF INTERSTATE 80 AND ALONG THE
RIDGES.

&&

.NEAR TERM /THROUGH TONIGHT/...
AN INTENSIFYING UPPER LOW IN NEW YORK STATE WILL PRODUCE
INCREASING NORTHWEST FLOW ACROSS LAKES HURON AND ERIE. WITH 850
MBE TEMPERATURES AT -10 AND COLDER GOOD LAKE EFFECT SNOW BANDS
CAN BE EXPECTED THIS AFTERNOON INTO TONIGHT. HEAVY LAKE EFFECT ACCUMULATIONS
CAN BE EXPECTED INTO TONIGHT ACROSS MERCER...VENANGO AND FOREST
COUNTY WHERE LAKE EFFECT SNOW WARNING IS IN EFFECT FROM NOON
TODAY THROUGH TUESDAY NIGHT. THE STRONG NORTHWEST FLOW WILL BRING
SIGNIFICANT OROGRAPHIC LIFT ALONG THE MOUNTAIN RIDGES. A WINTER STORM
WARNING HAS BEEN POSTED FOR THE MOUNTAINS WHERE HEAVY SNOW
ACCUMULATIONS ARE POSSIBLE IN THE HIGHER ELEVATIONS INTO TUESDAY.
SNOW SHOWERS WILL BE LIKELY ACROSS MUCH OF THE REMAINDER OF THE
FORECAST AREA BUT WITH LIGHTER SNOW ACCUMULATION EXPECTED.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY/...
SNOW SHOWERS WILL CONTINUE FOR MONDAY INTO MONDAY NIGHT WITH
WINDS INCREASING AS THE STRONG UPPER LOW CONTINUES TO DEEPEN. INITIAL
LAKE ERIE EFFECT WILL BE JOINED BY A LAKE HURON TAP AND INCREASED
UPSLOPING FOR MONDAY INTO TUESDAY. THE RESULT WILL BE WIDESPREAD
SNOW SHOWERS FOR MOST AREAS...WITH SIGNIFICANT ACCUMS FOR THE I-80
CORRIDOR AND THE RIDGES...AND AT LEAST SOME ACCUMULATION FOR ALL
AREAS. IN ADDITION...SURFACE PRESSURE GRADIENTS TIGHTEN WITH
INCREASING WINDS ALOFT WILL RESULT IN BRISK/BLUSTERY CONDITIONS
WITH AREAS OF BLOWING SNOW MONDAY INTO TUESDAY. THE LAKE EFFECT
SNOW WARNING CONTINUES FOR MERCER/VENANGO/FOREST COUNTIES...AND A
WINTER STORM WARNING IS IN EFFECT FOR THE PRESTON/TUCKER/GARRETT
COUNTIES...AS WELL AS FOR THE RIDGES OF WESTMORELAND AND FAYETTE
COUNTIES. WITH THE WINDY CONDITIONS MONDAY/TUESDAY AND LOWS IN THE
TEENS AND LOWER 20S...WIND CHILL READINGS WILL FALL INTO THE
SINGLE DIGITS LATE EARLY MONDAY MORNING AND TUESDAY MORNING.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
GFS/ECMWF/NAEFS SHOW MODEL AGREEMENT TUESDAY NIGHT WITH THE AREA
REMAINING IN A CYCLONIC FLOW AS AN UPPER LOW ACROSS QUEBEC CONTINUES
TO DRIVE THE SYNOPTIC WEATHER PATTERN. THIS WILL ALLOW THE UPPER
OHIO VALLEY TO BE IN A NORTHWESTERLY FLOW. TO BEGIN THE PERIOD THERE
WILL BE MORE OF A NORTHERLY COMPONENT IN THE MID-LEVELS AS A SHORT
WAVE PUSHES EAST OF THE AREA. THE MOIST LOW-LEVEL FLOW OFF OF THE
GREAT LAKES WILL SHIFT TO MORE WEST-NORTHWESTERLY THROUGH THE DAY ON
WEDNESDAY. THIS WILL ALLOW FOR THE BEST CHANCE OF SNOW SHOWERS TO BE
CONFINED TO THE LAKE EFFECT ZONES ALONG THE I-80 CORRIDOR AND
EASTERN RIDGES WITH LOWER CHANCE TO SCHC POPS IN WESTERN PA AND
EASTERN OHIO.

850MB WINDS WILL CONTINUE TO BACK FURTHER ON THURSDAY AS A LONG WAVE
TROUGH ACROSS EASTERN CANADA PIVOTS FURTHER EAST AND A SURFACE HIGH
BUILDS IN FROM THE SOUTHWEST. THE MID-LEVEL FLOW WILL FLATTEN ON
FRIDAY...BECOMING MORE ZONAL ON FRIDAY AND ALLOWING TEMPS TO FINALLY
BEGIN TO MODERATE. GFS/ECMWF/GFSE ARE ALL SUPPORTIVE OF A TROUGH AND
ITS ASSOCIATED SURFACE LOW APPROACHING FROM THE
NORTHWEST...INCREASING THE CHANCE FOR SNOW WITH THE PASSAGE OF A
COLD FRONT LATE ON FRIDAY INTO EARLY SATURDAY.

FORECAST TEMPS ARE SUPPORTED BY THE NAEFS...WHICH SHOWS LITTLE
SPREAD IN THE ENSEMBLE THROUGH THURSDAY. IN ADDITION...CLOUD
COVERAGE IN A NORTHWESTERLY FLOW WILL CONTINUE TO LIMIT THE DIURNAL
RANGE (10-15F DIFFERENCE BETWEEN HIGHS AND LOWS) IN TEMPS UNTIL
FRIDAY. FORECAST TEMPS ARE AROUND 10 DEGREES BELOW NORMAL THROUGH
THURSDAY...WITH TEMPS AROUND 5 DEGREES BELOW NORMAL ON FRIDAY AND
SATURDAY.

&&

.AVIATION /08Z SUNDAY THROUGH THURSDAY/...

A NORTHWEST TO NORTH FLOW ACROSS THE GREAT LAKES WILL PERSIST
THROUGH THE MIDDLE OF THE WEEK. THIS WILL RESULT IN THE POTENTIAL
FOR PERIODIC REDUCED CONDITIONS IN LAKE EFFECT SNOW BANDS. IN
HEAVIER SQUALLS...IFR AND LOWER CONDITIONS WILL BE POSSIBLE. IN
ADDITION...A FAIRLY TIGHT PRESSURE GRADIENT WILL RESULT IN PRIMARILY
DAYTIME WIND GUSTS OF 20 TO 25 KNOTS THROUGH TUESDAY.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...WINTER STORM WARNING FROM NOON TODAY TO 7 PM EST TUESDAY FOR
     MDZ001.
OH...NONE.
PA...WINTER WEATHER ADVISORY FROM NOON TODAY TO 7 PM EST TUESDAY
     FOR PAZ013>016-022-023.
     WINTER STORM WARNING FROM NOON TODAY TO 7 PM EST TUESDAY FOR
     PAZ074-076.
     LAKE EFFECT SNOW WARNING FROM NOON TODAY TO 7 PM EST TUESDAY
     FOR PAZ007>009.
WV...WINTER STORM WARNING FROM NOON TODAY TO 7 PM EST TUESDAY FOR
     WVZ023-041.

&&

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>