Area Forecast Discussion
Issued by NWS Huntsville, AL

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FXUS64 KHUN 071717 AAC
AFDHUN

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE HUNTSVILLE AL
ISSUED BY NATIONAL WEATHER SERVICE BIRMINGHAM AL
1217 PM CDT TUE JUL 7 2015

.UPDATE...
FOR 18Z TAFS

&&

.DISCUSSION...
/ISSUED 937 AM CDT TUE JUL 7 2015
 BY NATIONAL WEATHER SERVICE BIRMINGHAM AL/
NO LARGE CHANGES PLANNED FOR THE MORNING FORECAST UPDATE. SATELLITE
DERIVED PRECIPITABLE WATER ANALYSIS SHOWS VALUES BELOW 1.5 INCHES
ACROSS NORTH ALABAMA. WILL KEEP THE SLIGHT CHANCE OF STORMS FOR THE
AFTERNOON IN DEFERENCE TO CLIMO...WITH A SLIGHTLY ENHANCED CHANCE
OVER THE ELEVATED HEAT SOURCE EAST OF I-65. OTHERWISE...FORECAST
APPEARS TO BE ON TRACK.

/61 AT BMX/

&&

.AVIATION...
FOR 18Z TAFS...

HIGH PRESSURE RIDGE IN PLACE WITH CENTER OF RIDGE TO THE EAST OF
ALABAMA AND WEAK SOUTH TO SOUTHWEST FLOW OVER THE NORTH ALABAMA TAFS.
ONLY VERY ISOLATED DIURNALLY DRIVEN HEAT INDUCED CONVECTION IS
ANTICIPATED AND WILL LEAVE MENTION OUT OF TAFS AT THIS TIME.
OTHERWISE ONLY SOME GENERALLY FAIR WEATHER CUMULUS AND MAINLY VFR
EXPECTED. WINDS WILL BE A TAD GUSTY WITH HIGHER GRADIENT SOUTHWEST
WINDS THIS AFTERNOON AHEAD OF NEXT SYSTEM BUT SHOULD LIGHTEN TURNING
MORE SOUTHERLY OVERNIGHT BUT MAY NOT CALM COMPLETELY.

08/KEISER AT BMX

&&

.PREV DISCUSSION...
/ISSUED 405 AM CDT TUE JUL 7 2015/
A LOW PRESSURE SYSTEM MOVING THROUGH SOUTHERN CANADA/GREAT LAKES
REGION WAS NOTED ON SATELLITE IMAGERY THIS MORNING. A COLD FRONT
EXTENDS SWWRD FROM THIS LOW INTO SW TEXAS. A FEW ISOLATED
SHOWERS/THUNDERSTORMS HAVE FORMED OUT AHEAD OF THE FRONT AND ARE
MOVING THROUGH WEST CENTRAL TENNESSEE AS OF 0830Z THIS MORNING. BASED
ON RADAR TRENDS THESE STORMS WILL REMAIN TO THE NORTH. HOWEVER...
OUTFLOW FROM THESE STORMS COULD GENERATE AN ISOLATED SHOWER ALONG THE
AL/TN BORDER THIS MORNING BUT ANYTHING THAT DOES DEVELOP WILL BE
SHORT LIVED.

NAM/GFS/ECMWF GUIDANCE ARE ALL IN FAIR AGREEMENT IN DEVELOPING
MULTIPLE WAVES ALONG THE COLD FRONT THROUGH WEDNESDAY. AS THESE
DEVELOP THE GENERAL TREND WILL BE TO TAKE THE SYSTEMS TO THE E/NE
INTO THE OHIO VALLEY...WHILE PROGRESSING THE COLD FRONT SLOWLY
EASTWARD. SHORT RANGE MODELS DEVELOP A LINE OF SHOWERS AND
THUNDERSTORMS TODAY WITH THE FIRST WAVE AND BRING THEM EAST TOWARDS
THE AREA THIS EVENING/OVERNIGHT. BUT WITH THE ADVERTISED HIGH
PRESSURE SYSTEM BEGINNING TO BUILD WESTWARD TODAY THESE STORMS WILL
BE SHUNTED NORTHWARD AND MOST ACTIVITY SHOULD REMAIN IN TENNESSEE.
A SIMILAR SITUATION IS EXPECTED AGAIN ON WEDNESDAY AND HAVE KEPT
ISOLATED SHOWERS AND THUNDERSTORMS IN THE FORECAST FOR BOTH DAYS.

THE HIGH PRESSURE/UPPER RIDGE BECOMES ANCHORED OVER THE SOUTHEASTERN
STATES LATER THIS WEEK AND WILL RESULT IN HOT AND HUMID CONDITIONS.
HEIGHTS AND 850MB TEMPS STEADILY INCREASE EACH DAY AND VALUES FRIDAY
THROUGH SUNDAY WILL BE SIMILAR TO THOSE WE SAW TOWARDS THE END OF
JUNE. ECMWF/GFS GUIDANCE HAS COME IN WARMER THAN PREVIOUS GUIDANCE
FOR THE THURSDAY TO SUNDAY TIME FRAME AND HAVE NUDGED TEMPS UPWARDS
A DEGREE OR TWO EACH DAY FROM INHERITED FORECAST. FRIDAY THROUGH
SUNDAY WILL LIKELY BE THE HOTTEST DAYS OF THE WEEK WITH TEMPS IN THE
MID 90S FOR MOST LOCATIONS WITH A FEW PLACES REACHING INTO THE UPPER
90S. WHILE THE SUBSIDENCE ASSOCIATED WITH THE HIGH WOULD SUGGEST
THINGS REMAINING DRY LATE THIS WEEK...THE HOT TEMPS COULD ALLOW FOR
AN ISOLATED SHOWER/THUNDERSTORM TO POP UP AND HAVE KEPT A SLIGHT
CHANCE IN EACH AFTERNOON.

THE DIFFICULT ITEM WITH THE CURRENT FORECAST WILL BE THE AFTERNOON
DEWPOINTS/MOISTURE FROM THURSDAY THROUGH SUNDAY. MODELS HAVE COME IN
A BIT DRIER AND SHOW MORE OF THIS DRY AIR MIXING DOWN TO THE SURFACE
EACH AFTERNOON WITH VALUES DROPPING INTO THE LOW TO MID 60S. THINK
THIS MIGHT BE OVER DONE AS RECENT RAINFALL SHOULD PROVIDE A BIT MORE
LOW LEVEL MOISTURE AND IS NOT REPRESENTED WELL IN THE MODEL
FORECASTS. CURRENT FORECAST KEEPS DEWPOINTS IN THE UPPER 60S TO NEAR
70 DEGREES IN THE AFTERNOON. THIS SHOULD RESULT IN HEAT INDICES
RANGING FROM THE UPPER 90S TO LOWER 100S FOR THE TENNESSEE VALLEY
FRIDAY THROUGH SUNDAY. EITHER WAY...IT WILL BE THE TYPICAL HOT AND
HUMID CONDITIONS EXPECTED DURING THE SUMMER TIME IN THE SOUTHERN US.

HEADING INTO NEXT WEEK THE MODELS HAVE DIVERGED SLIGHTLY IN REGARDS
TO THE FORECASTED TROUGH DEVELOPING ACROSS THE EASTERN US. THE ECMWF
DIGS THE TROUGH A BIT FURTHER SOUTH MONDAY/TUESDAY WITH THE POTENTIAL
FOR RAIN. THE GFS AND GFS ENSEMBLE MEMBERS HAVE A MORE FLAT/ZONAL
APPROACH THE RIDGE/TROUGH NEXT WEEK AND KEEP HOT TEMPS GOING INTO
EARLY NEXT WEEK. STILL WAY OUT IN THE EXTENDED BUT WORTH WATCHING.

STUMPF

&&

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

$$

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


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