Area Forecast Discussion
Issued by NWS Huntsville, AL

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000
FXUS64 KHUN 282335 AAA
AFDHUN

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE HUNTSVILLE AL
635 PM CDT MON JUL 28 2014

.UPDATE...
FOR 00Z TAFS

&&

.DISCUSSION...
/ISSUED 256 PM CDT MON JUL 28 2014/
WHAT A DIFFERENCE A DAY MAKES! A COLD FRONT THAT SWEPT ACROSS THE
AREA EARLIER TODAY HAS RESULTED IN COOLER AND MUCH DRIER CONDITIONS.
20Z TEMPS WERE IN THE LWR-MID 80S /5-10F DEGREES COOLER THAN THIS
TIME YESTERDAY/. DEWPTS/HUMIDITY WERE NOTICEABLY LOWER /AROUND 60F/
COMPARED TO THE MID 70S YESTERDAY AFTN. EXPECT A SLIGHT INCREASE IN
CLOUDS THROUGH THE AFTERNOON AS A BROAD SCT-BKN CU FIELD WORKS ITS
WAY SOUTH.

ON THE BACKSIDE OF AN UPR LVL LOW IMPACTING NEW ENGLAND...A
UNUSUALLY DEEP /FOR LATE JULY/ LONGWAVE TROUGH WILL AFFECT THE
EASTERN CONUS THROUGH MUCH OF THE WEEK. THIS WILL RESULT IN BELOW
NORMAL TEMPERATURES AND MUCH LOWER HUMIDITY. THE NEXT POTENTIAL FOR
ANY RAINFALL WILL ARRIVE THURSDAY AS AN AREA OF LOW PRESSURE
APPROACHES FROM THE ARKLATEX REGION.

THE MAIN STORY OVER THE NEXT COUPLE DAYS WILL BE THE UNSEASONABLY
COOL AND DRY CONDITIONS. SOME LOCATIONS WILL APPROACH RECORD LOW
VALUES TONIGHT AND ESPECIALLY TUESDAY NIGHT/WEDNESDAY MORNING. THE
OFFICIAL RECORD LOW IN HUNTSVILLE FOR JULY 30TH IS 60F SET IN 1914
/WE ARE FORECASTING A LOW OF 58F AT THIS TIME/. THE NORMAL LOW IS
70F.

THE UPR LVL PATTERN IS NOT EXPECTED TO CHANGE MUCH THROUGH THE WEEK
AS A DEEP UPR LVL VORTEX REMAINS NEARLY STATIONARY OVER THE HUDSON
BAY IN EASTERN CANADA. UPSTREAM "ENERGY" AND MOISTURE THAT HAS BEEN
RECYCLING AROUND THE PERSISTENT UPR RIDGE OVER THE INTERMOUNTAIN
WEST WILL GRADUALLY BREAK OFF AND SLIDE DOWN THE BACKSIDE OF THE
BROAD UPR TROUGH AFFECTING THE EASTERN CONUS. AS THIS OCCURS...
A COMPLEX OF SHOWERS AND THUNDERSTORMS IS EXPECTED TO BREAK OUT
WEDNESDAY NIGHT ALONG/NORTH OF A WARM FRONT NEAR THE RED RIVER VALLEY
OF OK/TX. MODELS SPREAD THIS PRECIP SOUTH/EAST...POSSIBLY AFFECTING
PORTIONS OF THE TN VALLEY BY THURSDAY. THE 12Z/NAM INITIATES FARTHER
NORTH WITH THE PRECIP - IN SRN MO/NRN AR. BOTH THE GFS AND NAM SPREAD
SOME LIGHT (ELEVATED/ISENTROPICALLY-DRIVEN) PRECIP ACROSS THE AREA
THURSDAY. WPC GUIDANCE APPEARS TO BE LEANING TOWARD THE ECMWF WHICH
KEEPS THE BULK OF ANY PRECIP SOUTH/WEST OF THE AREA. TO ACCOUNT FOR
THE DIFFERENCES...WENT AHEAD AND INSERTED JUST A "SLIGHT CHANCE" FOR
SHOWERS/STORMS ON THURSDAY.

BEYOND THURSDAY...THE DEEP TROUGH WILL REMAIN FIRMLY ENTRENCHED
ACROSS THE EASTERN HALF OF THE CONUS. MEDIUM RANGE MODELS ARE IN
PRETTY GOOD AGREEMENT KEEPING THE DEEPEST MOISTURE/FORCING SOUTH AND
EAST OF THE FORECAST AREA -- FROM THE GULF COAST AND UP THE EAST
COAST. THIS MAKES SENSE GIVEN THE POSITIONING OF THE UPR TROUGH AXIS
WHICH IS PROGGED TO BE NEARLY OVERTOP NRN AL/SRN TN. THIS ALSO MAKES
IT CHALLENGING TO PREDICT POPS/WX. WENT AHEAD AND LEANED TOWARD THE
HPC/WPC GUIDANCE FOR POPS...SHOWING LOW CHANCE POPS (25-30%) ACROSS
NORTHEAST AL AND NIL TO SLIGHT CHANCE POPS WEST. GIVEN THE UPR LVL
PATTERN...EXPECT TEMPS TO REMAIN JUST BELOW NORMAL THROUGH THE
PERIOD WITH HIGHS IN THE MID-UPR 80S AND LOWS GENERALLY IN THE 60S.

DJN.83

&&

.AVIATION...
FOR 00Z TAFS...
VFR CONDS WILL PREVAIL AT BOTH TAF SITES THRU THE PERIOD, WITH ONLY A
FEW CLOUDS OVERHEAD. A WEAK DISTURBANCE PROVIDING ANOTHER SHOT OF
DRY AIR WILL PASS THROUGH THE TERMINALS OVERNIGHT, BUT ONLY A SLIGHT
INCREASE IN CLOUD COVER IS NOTED (AND A TEMPO GROUP WAS ADDED TO
ACCOUNT FOR THIS). OTHERWISE, A FEW CLOUDS ARND 5KFT AND LIGHT
NORTHERLY WINDS WILL PREVAIL THRU 00Z WEDNESDAY.

12

&&

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

$$

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



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