Dense Fog in Maryland, September 29, 2011

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
831 PM EDT WED SEP 28 2011

.SYNOPSIS...
A CUTOFF LOW PRESSURE SYSTEM OVER MICHIGAN WILL CONTINUE TO DRIFT
EAST THROUGH TONIGHT. AN ASSOCIATED COLD FRONT IS EXPECTED TO MOVE
INTO THE MID-ATLANTIC REGION THURSDAY. AN UPPER-LEVEL DISTURBANCE
WILL TRACK INTO THE REGION FRIDAY AND SATURDAY BEFORE HIGH
PRESSURE BUILDS OVERHEAD SUNDAY INTO EARLY NEXT WEEK.

&&

.NEAR TERM /TONIGHT/...

WE RCVD A REPORT OF 1.25" OF RAIN IN UNDER ONE HR IN ERN PRINCE.
WLLM COUNTY. GIVEN THE HISTORY OF HVY RAFL DURG THE PAST MONTH WE
HV ISSUED A FLSH FLD WRNG INCLUDING DC.

I'M SEARCHING MY MENTAL DATA BANK FOR AN EXAMPLE WHERE A LOW PRES
AREA WAS STATIONARY FOR SO LONG. I'M SURE THIS HAS HAPPENED
BEFORE...BUT THIS IS CERTAINLY OUT OF THE ORDINARY. I DID A SFC
ANLYS AT 17Z YDA AND AGN AT 19Z TDA. THE SFC LOW LOOKS LK IT'S
TRACKED ABT 30 MILES IN 26 HRS - "GLACIAL" MVMNT.

ON W.V. IMGRY THE OCCLUSION XTNDG FM THE LOW OVR THE UPR MIDWEST
IS APPARENT. FM THERE THE POSN OF THE WARM/COLD FNT BECOMES
SOMEWHAT DIFFICULT TO FIND...AS THE TEMP/MOISTURE GRADIENT BECOMES
QUITE DIFFUSE...SO WHEN THE COLD FNT FINALLY DOES PUSH INTO THE
AREA DON'T XPCT TO FEEL MUCH OF A DIFFERENCE. HOWEVER THE W.V. IMGRY DOES
SHOW SVRL BOUNDARIES DROPPING ACROSS PA INTO THE MID ATLC...AND
CNVCTN IS FIRING ALONG ONE OF THE THESE IN THE DC AREA ATTM.
PCPTBL WATER IN 00Z IAD SNDG ALMOST 1.7". NRML AT THIS TIME OF YR
ARND 0.9"...SO WE ARE STILL +2 STNDRD DEV ABV NRML...HENCE FLSH
FLDG RMNS A PSBLTY.

LOWS RANGING FM THE MU60S E OF I-95 TO THE LM50S IN THE HIGHLANDS.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY/...

COOLER AND NOTICEABLY LESS HUMID CONDITIONS ARE EXPECTED BEHIND
THE COLD FRONT THURSDAY NIGHT THROUGH FRIDAY. MIN TEMPS THURSDAY
NIGHT WILL RANGE FROM THE 40S IN THE POTOMAC HIGHLANDS TO NEAR 60
IN WASHINGTON AND BALTIMORE. MAX TEMPS FRIDAY WILL RANGE FROM THE
50S IN THE MOUNTAINS TO THE UPPER 70S IN CENTRAL VIRGINIA.

A POTENT UPPER-LEVEL SHORTWAVE WILL DROP SOUTHWEST FROM CANADA INTO
THE GREAT LAKES THURSDAY NIGHT AND FRIDAY. THIS SYSTEM WILL CARVE
OUT AN UPPER-LEVEL TROUGH OVER THE MID-ATLANTIC DURING THIS TIME.
DESPITE THE COLDER AIR ALOFT...MOST PLACES WILL REMAIN DRY WITH JUST
SOME CLOUDS DUE TO A WESTERLY DOWNSLOPING FLOW BEHIND THE COLD
FRONT. THE ONE EXCEPTION WILL BE ACROSS THE ALLEGHENY AND POTOMAC
HIGHLANDS. AN UPSLOPE COMPONENT TO THE LOW-LEVEL FLOW MAY TRIGGER A
FEW SHOWERS...ESPECIALLY FRIDAY AFTERNOON WHERE THERE MAY BE LIMITED
INSTABILITY.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...

ANOTHER SHORTWAVE WILL ROTATE AROUND THE TROUGH CAUSING AN
UPPER-LEVEL LOW TO CLOSE OFF FRIDAY NIGHT INTO SATURDAY. A NORTHWEST
FLOW WILL AROUND THIS SYSTEM WILL USHER IN MORE MOISTURE FROM THE
GREAT LAKES. DEEPER MOISTURE ALONG WITH INCREASED LIFT FROM THE
UPPER-LEVEL LOW WILL CAUSE PLENTY OF CLOUDS ALONG WITH THE
POSSIBILITY OF SHOWERS. THE BEST CHANCE FOR SHOWERS WILL BE ACROSS
THE ALLEGHENY AND POTOMAC HIGHLANDS DUE TO AN UPSLOPE COMPONENT TO
THE LOW-LEVEL FLOW.

COLDER AIR ALOFT ALONG WITH INCREASED CLOUD COVER AND MOISTURE WILL
COMBINE WITH A NORTHWEST FLOW TO USHER IN THE COOLEST AIRMASS OF THE
SEASON. MIN TEMPS FRIDAY NIGHT WILL RANGE FROM THE 30S IN THE
MOUNTAINS TO THE LOWER 50S IN WASHINGTON AND BALTIMORE. MAX TEMPS
SATURDAY WILL REMAIN IN THE 30S ACROSS THE RIDGE TOPS OF THE
ALLEGHENY AND POTOMAC HIGHLANDS TO NEAR 60 IN WASHINGTON AND
BALTIMORE. STRONG COLD ADVECTION AND LIFT MAY CAUSE ENOUGH COLD AIR
ALOFT FOR A FEW SNOW SHOWERS TO MIX IN ACROSS THE RIDGE TOPS OF THE
ALLEGHENY AND POTOMAC HIGHLANDS OVERNIGHT FRIDAY...GENERALLY FOR
ELEVATIONS ABOVE 3KFT. NO ACCUMULATION IS EXPECTED.

AN UPPER-LEVEL TROUGH WILL REMAIN OVERHEAD SATURDAY NIGHT CAUSING
MORE UNSETTLED AND COOL CONDITIONS. THE MID-LEVEL TROUGH WILL SLOWLY
MOVE EAST SUNDAY AND HIGH PRESSURE IS EXPECTED TO BUILD OVERHEAD
LATER SUNDAY THROUGH THE MIDDLE PORTION OF NEXT WEEK. DRY CONDITIONS
ARE EXPECTED DURING THIS TIME ALONG WITH A MODERATING TREND IN
TEMPERATURES.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...

CONVECTION WILL SLOWLY PUSH EASTWARD OVERNIGHT...WITH LINGERING
SHRA/TSRA FOR THE EARLY HALF OF THURSDAY.

VFR CONDITIONS ARE EXPECTED THURSDAY NIGHT THROUGH FRIDAY. WESTERLY
WINDS MAY GUST AROUND 20 KNOTS...ESPECIALLY FRIDAY AFTERNOON. AN
UPPER-LEVEL TROUGH WILL BRING UNSETTLED CONDITIONS FRIDAY NIGHT
THROUGH SATURDAY. SCATTERED SHOWERS ALONG WITH MVFR CIGS/VSBYS ARE
POSSIBLE. NORTHWEST WINDS WILL GUST AROUND 20 KNOTS.

HIGH PRESSURE WILL SLOWLY BUILD OVER THE TERMINALS SUNDAY THROUGH
EARLY NEXT WEEK.

&&

.MARINE...
S/SW WINDS AOB 15 KT THROUGH THURSDAY. STRONG/SEVERE CONVECTION MAY
LEAD TO SMW THROUGH THE OVERNIGHT HOURS. A WEAK FRONT WILL CROSS THE
WATERS TOMORROW.

WESTERLY WINDS ARE EXPECTED BEHIND A COLD FRONT THURSDAY NIGHT
THROUGH FRIDAY. AN SCA MAY BE NEEDED FOR PORTIONS OF THE WATERS
FRIDAY.

AN UPPER-LEVEL TROUGH WILL BUILD OVER THE WATERS FRIDAY NIGHT
THROUGH SATURDAY. AN SCA WILL LIKELY BE NEEDED FOR PORTIONS OF THE
WATERS. HIGH PRESSURE WILL SLOWLY BUILD OVERHEAD SUNDAY INTO EARLY
NEXT WEEK. A SMALL CRAFT ADVISORY CONDITIONS ARE LIKELY DURING THIS
TIME.

&&

.TIDES/COASTAL FLOODING...
TIDAL ANOMALIES ARE RUNNING AROUND A FOOT ABOVE NORMAL THIS
AFTERNOON. WILL LEAVE THE CFW HEADLINE AS IS BUT WL PRBLY NEED TO
BE XTND IN TIME. POSITIVE ANOMALIES WILL CONTINUE UNTIL A W/NW WIND
OCCURS.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...COASTAL FLOOD ADVISORY UNTIL 11 PM EDT THIS EVENING FOR DCZ001.
MD...COASTAL FLOOD ADVISORY UNTIL 1 AM EDT THURSDAY FOR MDZ007-011-
     014-017-018.
     COASTAL FLOOD ADVISORY UNTIL 11 PM EDT THIS EVENING FOR MDZ013-
     016.
VA...COASTAL FLOOD ADVISORY UNTIL 11 PM EDT THIS EVENING FOR
     VAZ052>055-057.
WV...NONE.
MARINE...NONE.

&&

UPDATE...WOODY!
PRVS...NWL/BJL

<!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>

<!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>

<!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>

<!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>