Heat Advisory 13, NWS Huntsville, AL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HUNTSVILLE AL
312 PM CDT THU AUG 4 2011

.DISCUSSION...
LATEST WATER VAPOR IMAGERY AND H5 RUC ANALYSIS INDICATE THE QUASI
STAGNANT PATTERN OF RIDGING ACROSS THE ARKLATEX CONTINUES. AROUND
THE PERIPHERY OF THIS RIDGE AND CLOSE TO HOME...A DECAYING MCS IS
VERY SLOWLY SLIDING OUT OF THE SOUTHEAST PORTION OF THE CWFA.
CONVECTION IS JUST BEGINNING ACROSS THE EXTREME NORTHWEST PORTION OF
THE CWFA ASSOCIATED WITH OUTFLOW FROM THE EARLIER MCS ACROSS
MISSOURI. SURFACE OBSERVATIONS SUGGEST A BOUNDARY CONTINUES TO
LINGER ALONG THE TN/AL LINE...WITH SOUTHERLY FLOW AND MOISTURE
POOLING ACROSS MUCH OF THE CWFA.

GIVEN THE COMBINATION OF THE SURFACE FRONT...OUTFLOW
BOUNDARIES...AND HIGH INSTABILITY IN THE WEST WHERE EARLY AFTERNOON
CLEARING ALLOWED TEMPERATURES TO QUICKLY JUMP INTO THE 90S...EXPECT
SCATTERED CONVECTION TO CONTINUE INTO THE EVENING HOURS. WHILE THE
SURFACE LAYER SHOULD BECOME STABLE OVERNIGHT...ELEVATED INSTABILITY
WILL PERSIST. GIVEN THE TYPICALLY UNSETTLED NATURE OF NORTHWEST FLOW
ALOFT...WILL MAINTAIN ISOLATED THUNDERSTORM CHANCES IN THE FORECAST
THROUGH THE NIGHT. HOWEVER...GIVEN THE PROGGED WESTWARD MOTION OF
THE UPPER RIDGE...WOULD NOT BE SURPRISED IF CONVECTIVE CHANCES ARE
REMOVED BY THE EVENING SHIFT. GIVEN THE COVERAGE AND AMOUNT OF
PRECIPITATION LAST NIGHT COUPLED WITH EXPECTED LIGHT WINDS
OVERNIGHT...HAVE ADDED PATCHY FOG TO THE FORECAST. OTHERWISE...LOOK
FOR FAIRLY MUGGY CONDITIONS WITH LOWS IN THE LOW TO MIDDLE 70S.

FOR TOMORROW...EXPECT A SHORTWAVE MOVING NORTH OF THE AREA TO SPARK
SCATTERED THUNDERSTORM DEVELOPMENT DURING THE MORNING HOURS.
SOUNDINGS SUGGEST AMPLE ELEVATED INSTABILITY WILL BE PRESENT...WHICH
STORMS SHOULD EVENTUALLY BE ABLE TO TAP INTO. STRONG STORMS MAY
EXIST TOMORROW...WITH GUSTY WINDS AND LOCALLY HEAVY RAINFALL THE
MAIN THREATS. SOME OF THE STRONGEST STORMS COULD BECOME
SEVERE...WITH DAMAGING WINDS POSSIBLE. WHILE THE BEST CHANCES FOR
THIS ACTIVITY SHOULD BE IN THE SOUTHWEST PORTION OF THE
CWFA...POTENTIAL CLOUD COVERAGE ASSOCIATED WITH THIS ACTIVITY LIMITS
CONFIDENCE FOR AFTERNOON HIGH TEMPERATURES. THE GFS SHOWS FAIRLY
DEEP AFTERNOON MIXING...AND ITS CORRESPONDING MOS SUGGESTS HIGHS IN
THE LOW TRIPLE DIGITS FOR MANY AREAS. HOWEVER...DO NOT BELIEVE WE
WILL REALIZE THIS KIND OF HEATING OR MIXING...SO WAS MORE
CONSERVATIVE WITH TEMPERATURES /IN THE MID 90S FOR MANY LOCATIONS/.
AS CURRENTLY FORECAST...THIS WILL KEEP HEAT INDEX VALUES JUST SHY OF
ADVISORY CRITERIA...ALTHOUGH IF MODELS CAN OFFER A GREATER CONSENSUS
ON A WARM SOLUTION FOR TOMORROW...THE MID SHIFT MAY NEED TO CONSIDER
A HEAT ADVISORY FOR A PORTION OF THE CWFA.

THE SHORTWAVE SHOULD TRANSLATE EASTWARD FRIDAY EVENING AND
THUNDERSTORM COVERAGE SHOULD DIMINISH...LEAVING WARM TEMPERATURES
AND PATCHY FOG...BEFORE ADDITIONAL DEVELOPMENT IS EXPECTED ON
SATURDAY AS A H85 TROUGH SKIRTS THE NORTHERN PORTIONS OF THE CWFA.
BUFR SOUNDINGS FROM BOTH THE NAM AND GFS SUGGEST THE ATMOSPHERE WILL
BE QUITE MOISTURE RICH THROUGH THE WEEKEND...WITH PWATS PROGGED OVER
2.5 INCHES DURING THE AFTERNOON ON SATURDAY. ANY STORMS THAT DEVELOP
IN THIS ATMOSPHERE WILL CERTAINLY BE CAPABLE OF LOCALLY HEAVY
RAINFALL AND GUSTY WINDS.

AN UNSETTLED FORECAST WILL CONTINUE INTO NEXT WEEK AS THE H5 RIDGE
RETROGRADES AND NORTHWEST FLOW ALOFT BECOMES THE DOMINANT SYNOPTIC
TRIGGER. LOOK FOR ISOLATED TO SCATTERED THUNDERSTORM CHANCES NEARLY
EVERY PERIOD WITH HIGHS IN THE LOW 90S AND LOWS IN THE LOW/MID 70S.

&&

.PRELIMINARY POINT TEMPS/POPS...
HUNTSVILLE    75  96  76  95  76 /  20  50  30  50  30
SHOALS        76  96  75  97  75 /  20  50  20  50  20
VINEMONT      73  95  74  93  74 /  20  50  30  50  30
FAYETTEVILLE  74  95  75  94  75 /  20  40  30  50  30
ALBERTVILLE   72  95  74  93  72 /  20  50  30  50  30
FORT PAYNE    71  95  73  94  72 /  20  40  30  50  40

&&

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

JLL

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE HUNTSVILLE AL
510 PM CDT THU AUG 4 2011

ALZ001>010-016-TNZ076-096-097-051000-
LAUDERDALE-COLBERT-FRANKLIN AL-LAWRENCE-LIMESTONE-MADISON-MORGAN-
MARSHALL-JACKSON-DEKALB-CULLMAN-MOORE-LINCOLN-FRANKLIN TN-
510 PM CDT THU AUG 4 2011

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH ALABAMA AND PORTIONS OF
SOUTHERN MIDDLE TENNESSEE.

.DAY ONE...THIS AFTERNOON AND TONIGHT...

SCATTERED THUNDERSTORMS ARE LIKELY...MAINLY OVER NORTHWEST
ALABAMA...WITH GUSTY WINDS...HAIL...FREQUENT CLOUD TO GROUND
LIGHTNING STRIKES. TORRENTIAL RAINFALL IS ALSO POSSIBLE IN THESE
STORMS. A FEW OF THE STORMS COULD BECOME SEVERE...WITH DAMAGING
WINDS POSSIBLE.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY...

THERE IS A CHANCE OF MAINLY AFTERNOON AND EVENING THUNDERSTORMS
THROUGH WEDNESDAY. A FEW STRONG STORMS WILL BE POSSIBLE EACH DAY...
WITH GUSTY WINDS...LIGHTNING...AND LOCALLY HEAVY RAINFALL THE PRIMARY
HAZARDS.

HEAT INDEX VALUES MAY REACH DANGEROUS LEVELS THROUGH THE UPCOMING
WEEKEND...WITH AFTERNOON HEAT INDICES POSSIBLY WARRANTING HEAT
ADVISORIES THROUGH THE PERIOD.

.SPOTTER CALL TO ACTION STATEMENT...

ACTIVATION OF STORM SPOTTERS AND EMERGENCY MANAGEMENT PERSONNEL IS
POSSIBLE THIS AFTERNOON AND EVENING...AND STORM REPORTS ARE ALWAYS
GREATLY APPRECIATED.

DD/JLL/CA