330
FXUS64 KHUN 222353
AFDHUN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HUNTSVILLE AL
553 PM CST SUN NOV 22 2009
UPDATE
FOR 00Z TAFS
AVIATION
UPPER TROF ACROSS THE AL/GA BORDER ATTM WITH A WEAK
UPPER HIGH ALONG THE MS RIVER. LOCAL RADARS WERE SHOWING THAT THE
PCPN IS OVER FOR BOTH TAF SITES. HOWEVER MODELS ARE SHOWING
CLOUDS WILL LIKELY DROP TO IFR CONDITIONS AT BOTH TAF SITES ARND
09Z MONDAY MRNG. THIS COULD PRODUCE SOME PATCHY DRIZZLE UNTIL ARND
15Z. OTHERWISE MODEL TIME SECTIONS KEEP LOW LEVEL MOISTURE ALL DAY
ON MONDAY...WITH MVFR CONDITIONS (DUE TO CLOUDS) EXPECTED FROM
15Z AND THRU THE REMAINDER OF THE TAF FCST.
PREV DISCUSSION
/ISSUED 249 PM CST SUN NOV 22 2009/
SYNOPSIS...A CUTOFF LOW SITUATED JUST OFF THE FL PANHANDLE HAS
SPREAD LIGHT RAIN AND CLOUD COVER ACROSS MUCH OF THE SOUTHEAST.
MEANWHILE...A SHORTWAVE TROUGH OVER THE CENTRAL AND SOUTHERN PLAINS
APPROACHES THE AREA FOR TUESDAY. ALSO...A LONGWAVE TROUGH OVER THE
PACIFIC NORTHWEST CONTINUES ITS TRACK EASTWARD ACROSS WA/OR/ID. THIS
WILL BE THE MAIN PLAYER IN THE WEATHER LATER THIS WEEK.
SHORT TERM (TONIGHT THROUGH WEDNESDAY NIGHT)...BY TONIGHT THE
MAJORITY (IF NOT ALL) THE RAIN SHOULD PRETTY MUCH COME TO AN
END...BUT A COUPLE OF WEAK WAVES MAY BRING SOME DRIZZLE TONIGHT.
THUS...A COOL DRIZZLY NIGHT IS IN STORE FOR THE TN VALLEY AS THE
CUTOFF LOW IS SWIFTLY LIFTED NORTHEAST AND LOWS STAY NEAR STEADY IN
THE MID TO UPPER 40S. FURTHERMORE...A LOW CLOUD DECK IS EXPECTED
WHICH WILL LEAD TO FOG PROBLEMS ESPECIALLY AT HIGHER ELEVATIONS.
AS THE CUTOFF LOW SHIFTS NORTHEAST...MOST OF THE CLOUD COVER WILL
LINGER LEADING TO A COOL DAY WITH DAYTIME HIGHS IN THE LOW TO
MID 50S. THE DRIZZLE WILL CONTINUE THROUGH TOMORROW MORNING AS THE
LOW CLOUD DECK REMAINS. THE SHORTWAVE APPROACHING FROM THE CENTRAL
PLAINS MAY PUSH THE CLOUD DECK EASTWARD SOMEWHAT BEFORE
LIFTING...BUT NOT ANTICIPATING MUCH HEADWAY IN CLEARING. THUS...AS
WITH PREVIOUS SHIFT...HAVE KEPT LOW TO MID 50S FOR DAYTIME HIGHS.
SOME LINGERING SHOWERS/DRIZZLE MAY BE POSSIBLE OVER NE AL DUE TO
OROGRAPHIC LIFT WITH THE WEAK WAVES CROSSING THE REGION. HAVE KEPT
THE AREAS OF FOG FOR MONDAY NIGHT GIVEN THE AMOUNT OF MOISTURE
PRESENT.
MEANWHILE BY TUESDAY...THE AFOREMENTIONED TROUGH OVER THE PACIFIC
NORTHWEST WILL HAVE MOVED EASTWARD OVER THE CENTRAL PLAINS...PUSHING
A COOL DRY AIR MASS OVER THE REGION. THERE IS NOT MUCH MOISTURE WITH
THIS SYSTEM...BUT THERE WILL LIKELY BE SOME REMAINING MOISTURE OVER
THE AREA. HAVE PLACED SOME LOW END POPS MAINLY OVER NW AL TUESDAY
NIGHT. ONE THING THAT IS STILL PERPLEXING IS THE TEMP FORECAST FOR
TUESDAY HIGHS. GUIDANCE IS STILL QUITE DIVERGENT FOR DAYTIME HIGHS
WITH MAVMOS IN THE MID 60S AS OPPOSED TO THE METMOS IN THE LOW 50S.
AM THINKING THIS HAS TO DO WITH A DIFFERING SOLUTION TO THE TEMP OF
THE AIR MASS THAT WILL BE ADVECTING NORTHWARD DURING THE DAY. HAVE
CHOSEN TO BLEND THE MET/MAV.
THE AIR MASS BEHIND THE FRONT APPEARS TO BE MAINLY DRY AS OPPOSED TO
COLD. SKY CONDITIONS WILL IMPROVE BY TUESDAY NIGHT INTO WEDNESDAY
GIVING WAY TO LOW 60S FOR DAYTIME HIGHS. GIVEN THE DRY AIR ADVECTION
OVER THE REGION...EXPECTING NIGHTTIME LOWS IN THE MID TO UPPER 30S.
THESE TEMPS MAY BE LOWER IF THE LONGWAVE TROUGH PUSHING EAST ACROSS
THE UPPER MS RIVER VALLEY INCREASES VELOCITY.
LONG TERM (THANKSGIVING DAY THROUGH SUNDAY)...ANOTHER WAVE
OF COLD AIR WILL ADVECT OVER THE AREA BEHIND A COLD FRONT EXPECTED
EARLY ON THANKSGIVING MORNING. THE FRONT SHOULD BE MAINLY A DRY COOL
PASSAGE. BREEZY NW WINDS WILL USHER TEMPS DOWN INTO THE LOW 50S. IN
FACT...TEMPS MAY ACTUALLY DROP DURING THE DAY WITH DAYTIME HIGHS
ACTUALLY OCCURRING AROUND MIDNIGHT. AS CLOUDS CLEAR LATE THAT DAY
INTO THE EVENING...TEMPS WILL CONTINUE TO DROP RAPIDLY.
CLOSE TO FREEZING TEMPS WILL BE POSSIBLE FOR FRIDAY MORNING. DRY
CONDITIONS WILL THEN CONTINUE ON FRIDAY THROUGH SATURDAY AS THE COLD
NW FLOW ADVECTS OVER THE AREA. BY FRIDAY NIGHT INTO SATURDAY...IF
THE FIRST FREEZE HAS NOT ALREADY OCCURRED ON FRIDAY MORNING...
EXPECTING TEMPS TO DROP TO AROUND FREEZING. TEMPS WILL THEN RISE
INTO THE LOW TO MID 50S ON SATURDAY. OTHERWISE...HAVE INCREASED
CLOUDS ON SUNDAY AS MED RANGE MODELS INDICATE ANOTHER WEAK SYSTEM IS
POSSIBLE OVER THE TN VALLEY.
HUN WATCHES/WARNINGS/ADVISORIES
AL...NONE.
TN...NONE.
007
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