Area Forecast Discussion
Issued by NWS Huntsville, AL

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000
FXUS64 KHUN 300157 AAB
AFDHUN

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE HUNTSVILLE AL
857 PM CDT TUE JUL 29 2014

.UPDATE...
NO CHANGES NEEDED

&&

.DISCUSSION...
QUIET WX PREVAILS ACROSS THE CNTRL TN VALLEY THIS TUE EVENING UNDER
PREDOM CLR SKIES. STRONG HIGH PRESSURE OUT OF THE LOWER MS VALLEY/MID
SOUTH REGIONS CONTINUES TO WORK ITS WAY INTO THE AREA...WITH LIGHT
NLY FLOW PERSISTING IN SOME LOCATIONS. THE MAIN STORY WILL CONTINUE
TO BE OVERNIGHT LOWS...AS WEAK COLD AIR ADVECTION LINGERS OUT OF THE
NNW. WITH DEW PT TRENDS HOVERING IN THE MID/UPPER 50S RANGE...IT`S
REASONABLE TO XPCT TEMPS TO CONTINUE GRADUALLY FALLING HEADING INTO
THE EARLY MORNING HRS...WITH SFC WINDS DECOUPLING OR REMAINING LIGHT.
A FEW MID/HIGH CLOUDS EMBEDDED WITHIN A STOUT NWLY FLOW REGIME IN
PLACE SHOULD DO LITTLE TO MITIGATE ADDITIONAL RADIATIONAL COOLING
OVERNIGHT. ONGOING FORECAST LOOKS TO HAVE THIS OVERALL WX PATTERN
WELL IN HAND...WITH NEAR RECORD/RECORD LOWS POSSIBLE BY WED MORNING.

09

&&

.AVIATION...
/ISSUED 621 PM CDT TUE JUL 29 2014/
FOR 00Z TAFS...WITH STRONG HIGH PRESSURE OVER THE LOWER MS VALLEY
BUILDING INTO THE AREA...VFR CONDS ARE XPCTED THROUGH THE PERIOD.

09

&&

.PREV DISCUSSION...
/ISSUED 335 PM CDT TUE JUL 29 2014/
IT IS AFTER 3 PM ON JULY 29TH, AND HSV HAS FINALLY HIT 80 DEGREES FOR
THE DAY. HSV WILL GET CLOSE TO TYING ITS RECORD LOW MAXIMUM (SEE
CLIMATE SECTION BELOW), WHILE MSL, WHICH IS STILL JUST 79 AT LAST
CHECK, STILL HAS AN OUTSIDE SHOT OF TYING ITS RECORD. MEANWHILE,
DEWPOINTS ACROSS HAVE FALLEN INTO THE UPPER 40S IN SOME AREAS, AND
THESE LOW DEWPOINTS CORRESPONDED WELL TO A DIMINISHED CU FIELD
STRETCHING FROM SMITH LAKE INTO EAST TENNESSEE. NOT SURPRISINGLY,
NORTHWEST FLOW IS NOTED ALOFT DUE TO AN ANOMALOUSLY DEEP (3-4
STANDARD DEVIATIONS BELOW NORMAL) TROUGH, WITH ITS AXIS CENTERED
ALONG/WEST OF THE APPALACHIANS.

THE MAIN QUESTION FOR TONIGHT IS: WILL WE BREAK ANY RECORDS? WITH
DEWPOINTS RUNNING UNDER SOME MODEL PROJECTIONS AND TEMPERATURES STILL
MOSTLY BELOW 80, HAVE UNDERCUT NAM AND GFS MOS AND TRENDED TOWARD
THE COOLER ECMWF MOS. THE NUMBERS PROPOSED BELOW WOULD EASILY BREAK
RECORDS AT HSV AND COME CLOSE AT MSL. SOUNDINGS SUGGEST THAT SOME
LIGHT CIRRUS COULD DRIFT IN LATER, WHICH MIGHT PUT A DAMPER ON
RADIATIONAL COOLING, BUT FOR NOW, IT IS HARD TO ARGUE AGAINST A
COOLER FORECAST. TOMORROW SHOULD BE A COUPLE DEGREES WARMER WITH COLD
AIR ADVECTION DIMINISHING, BUT IT SHOULD STILL BE WELL BELOW NORMAL.

THE FORECAST GETS MURKIER LATE WEDNESDAY INTO THURSDAY. DRY AIR
ADVECTION WILL EASE, ALLOWING SOME MODEST LOW-LEVEL MOISTURE TO
RETURN, AND ANOTHER SHORTWAVE WILL DIVE INTO THE RED RIVER & LOWER
MISSISSIPPI VALLEYS. MODELS ARE IN GOOD AGREEMENT ON PRODUCING A
SIZABLE SWATH OF QPF OVER OK/AR/LA, BUT MOISTURE RETURN DOES NOT GET
GOING HERE IN THE TENNESSEE VALLEY UNTIL LATER THURSDAY INTO FRIDAY.
THE QPF AND POPS SEEM A LITTLE OVERDONE WITH THE ANTICIPATED
MOISTURE AVAILABILITY, BUT THE POP FORECAST WILL BE LEFT MOSTLY
UNCHANGED THURSDAY AFTERNOON AND NIGHT. THURSDAY TEMPERATURES WILL
HINGE ON THIS PRECIP AND CLOUD COVER, AND IF THAT MATERIALIZES, THE
NAM AND GFS MOS WILL BE VASTLY OVERDONE. THEREFORE THE FORECAST WILL
TREND TOWARD/JUST BELOW THE COOLER ECMWF MOS, PARTICULARLY IN
NORTHWEST AL. MOISTURE WILL CONTINUE FILTERING INTO THE AREA FRIDAY
INTO SATURDAY AND MODEL CONSENSUS BRINGS A SHORTWAVE AROUND THE BASE
OF THE TROUGH, RESULTING IN INCREASED POPS.

AS THE PARENT UPPER LOW LIFTS BACK INTO CANADA LATE IN THE WEEK AND
OVER THE WEEKEND, IT WILL LEAVE BEHIND A BAGGY, LESS-DEFINED TROUGH.
THIS WILL PLACE THE AREA IN A TRANSITION ZONE BETWEEN GREATER
MOISTURE AMID SW FLOW TO THE EAST, AND DRIER CONDITIONS AMID NW FLOW
TO THE WEST. WHILE MEDIUM-RANGE MODELS AGREE ON THE PRESENCE OF THE
TROUGH, AGREEMENT ON THE TROUGH AXIS POSITION IS NOT AS GOOD. THE
FORECAST WILL MAINTAIN A LOW-END POP SUNDAY THROUGH TUESDAY AS A
COMPROMISE. TEMPERATURES WILL REBOUND CLOSER TO NORMAL DURING THIS
TIME PERIOD, BUT THEY STILL MAY NOT GET TO 90 DEGREES AGAIN UNTIL
THIS TIME NEXT WEEK. BASED ON VERIFICATION PERFORMANCE, TEMPERATURES
WILL TREND 2-4 DEGREES BELOW THE GFSX MOS FOR HIGHS, AND 1-3 BELOW
FOR LOWS.

BCC

&&

.CLIMATE...
/ISSUED 335 PM CDT TUE JUL 29 2014/
RECORDS FOR TODAY, TONIGHT, AND THE 31ST:

RECORD LOW MAXIMUM (TODAY):
HUNTSVILLE 81/2006 - MUSCLE SHOALS 79/2003

RECORD LOW (TONIGHT):
HUNTSVILLE 60/1914 - MUSCLE SHOALS 56/1914

RECORD LOW (31ST):
HUNTSVILLE 58/1965 - MUSCLE SHOALS 55/1965

BCC

&&

.HUN WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
TN...NONE.
&&

$$

FOR MORE INFORMATION PLEASE VISIT OUR WEBSITE
AT WEATHER.GOV/HUNTSVILLE.


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