Area Forecast Discussion
Issued by NWS Huntsville, AL

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000
FXUS64 KHUN 201120
AFDHUN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HUNTSVILLE AL
620 AM CDT WED AUG 20 2014

.UPDATE...
FOR 12Z TAFS

&&

.DISCUSSION...
/ISSUED 156 AM CDT WED AUG 20 2014/
WE WILL BE MONITORING CONVECTIVE TRENDS DURING THE NEXT FEW HOURS AS
THE RAP CONTINUES THE TREND OF THE NAM OF THE PAST FEW DAYS AT
FORECASTING NOCTURNAL CONVECTION FROM MIDDLE TN INTO NRN AL. IN FACT,
IR IMAGERY AND OBS INDICATE SOME CU DEVELOPMENT ACROSS PORTIONS OF
OUR FORECAST AREA. SPC MESOANALYSIS INDICATED MUCAPES OF 3000-4000
J/KG ACROSS THE REGION (AND EVEN HIGHER TO OUR WEST). THE OHX 00Z
RAOB INDICATED THIS AS WELL, ABOVE A CAPPING INVERSION. THE
CONVECTION WILL LIKELY FIRE JUST ABOVE THE CAP AS A LLJ OF 25-30KT
DEVELOPS. IF STORMS FIRE, THEY COULD BECOME STRONG TO SEVERE RATHER
QUICKLY, DESPITE LIMITED WIND SHEAR.

STORMS ARE PROGGED TO DECAY THIS MORNING AS THEY MIGRATE S-SE. THE
CAPPING INVERSION WILL LIKELY SUPPRESS CONVECTION FOR MOST OF THE
AREA TODAY. THE "EDGE" OF THE CAP APPEARS TO BE DEPICTED BY THE NAM
QPF FROM MIDDLE TN INTO NRN GA LATE THIS AFTN AND EVENING, POSSIBLY
JUST CLIPPING OUR EASTERN COUNTIES. FOR NOW, HAVE MAINTAINED A SCHC
POP FOR THE AREA FOR BOTH THIS MORNING AND POSSIBLE AFTERNOON
CONVECTION. THE DAY SHIFT MAY BE ABLE TO TRIM THIS BACK IN OUR
WESTERN ZONES AS TRENDS BECOME BETTER DEFINED.

SYNOPTICALLY, THE FORECAST HAS NOT CHANGED MUCH WITH A LARGE UPPER
RIDGE BUILDING OVER THE CENTRAL GULF STATES DURING THE LATTER HALF OF
THE WEEK, EXPANDING N AND W WITH TIME. THIS WILL RESULT IN THE
LONGEST HEAT WAVE OF THE SUMMER THUS FAR. WEAK NORTHERLY 5H FLOW
WILL BRING WEAK NARROW SHORTWAVES OVER THE RIDGE AND INTO THE SE. THE
CAP IS EXPECTED TO SUPPRESS DEEP CONVECTION, SO WILL KEEP A DRY
FORECAST GOING. DESPITE THE BUILDING RIDGE, THE GFS/EC MOS APPEAR A
BIT TOO WARM GIVEN PAST PERFORMANCE, AND WILL SIDE WITH THE NAM IN
THE SHORT TERM, AND ADJUST DOWNWARD SLIGHTLY IN THE MEDIUM RANGE
FORECAST. WITH TIME, DEEPER MIXING WILL LOWER AFTN DEW POINT VALUES.
HEAT INDEX VALUES WILL LIKELY FALL SHORT OF HEAT ADVISORY CRITERIA
DURING THIS PERIOD. HOWEVER, THE MAIN HAZARD WILL BE THE LONGEVITY OF
THE HEAT WAVE. THIS WILL BE ESPECIALLY APPARENT SINCE WE HAVE HAD A
VERY COOL SUMMER TO THIS POINT.

AK

&&

.AVIATION...
FOR 12Z TAFS...UNDER NW FLOW THIS MRNG A FEW SHRA/TSRA HAVE DEVELOP
OVER PORTIONS OF MID TN (EAST OF BNA). BASED ON STLT/RADAR TRENDS
THINKING THAT THIS PCPN WILL STAY NORTH/EAST OF THE TAF SITES.
A LARGE UPPER RIDGE WILL CONTINUE TO BUILD TOWARDS THE TN VALLEY
TODAY AND THRU THE REMAINDER OF THE WORK WEEK. OTHERWISE MAINLY VFR
CONDITIONS ARE EXPECTED THRU THE FCST PERIOD.

07

&&

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

$$

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



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