Severe Thunderstorm Warning 254, NWS Huntsville, AL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HUNTSVILLE AL
1117 AM CDT THU JUL 21 2011

.UPDATE...
MORNING UPDATE TO PUBLIC FORECAST.

&&

.DISCUSSION...
MAJOR CHANGES HAVE BEEN MADE TO THE FIRST PERIOD FORECAST...TO LOWER
HIGH TEMPERATURES...INCREASE POPS...AND CANCEL HEAT ADVISORY. IT
APPEARS THAT WEAK LOW-LEVEL MOISTURE CONVERGENCE ACROSS THE REGION
HAS BEEN SUFFICIENT TO GENERATE CONVECTION IN VERY MOIST/UNSTABLE AIR
MASS...AS THE STABILIZING EFFECTS OF RIDGING ALOFT HAVE NOW SHIFTED
TO THE NORTH OF THE LOCAL AREA. TO COMPLICATE MATTERS FURTHER...AN
MCS IS TRACKING SOUTHWESTWARD ACROSS THE CUMBERLAND PLATEAU IN
TENNESSEE...AND ALL INDICATIONS ARE THAT EITHER THE REMNANTS OF THIS
SYSTEM OR NEW CONVECTIVE CELLS GENERATED ALONG ITS OUTFLOW WILL
AFFECT THE AREA LATER THIS AFTERNOON. BASED ON CLOUD COVER AND
EXPECTATIONS OF NUMEROUS SHOWERS/STORMS HAVE LOWERED HIGH
TEMPERATURES -- BY AS MUCH AS 10-15 DEGREES -- IN PORTIONS OF THE
AREA...AND CANCELLED HEAT ADVISORY. A FEW LOCATIONS IN SOUTHERN
MIDDLE TENNESSEE AND FAR NORTHWEST ALABAMA MAY APPROACH 105 /HEAT
INDEX/ BEFORE THICKER CLOUDS ARRIVE...BUT CONDITIONS WILL NOT BE
WIDESPREAD ENOUGH TO WARRANT MAINTAINING THE ADVISORY. UPDATED
NPWHUN...HWOHUN...AND ROUTINE PUBLIC PRODUCTS HAVE ALREADY BEEN
TRANSMITTED.

70/DD

&&

.AVIATION DISCUSSION... /ISSUED 638 AM CDT THU JUL 21 2011/

PATCHY FOG THIS MORNING MAY IMPACT EITHER TERMINAL WITH REDUCTIONS
IN VISIBILITY BEFORE DISSIPATING QUICKLY AS MIXING ENSUES. EXPECTING
ISOLATED TO SCATTERED THUNDERSTORM DEVELOPMENT TODAY...POSSIBLY
LINGERING INTO THIS EVENING. GIVEN THE UNCERTAIN NATURE OF THESE
STORMS...OPTED FOR A CB GROUP ATTM. PATCHY FOG MAY AGAIN DEVELOP LATE
IN THE PERIOD...ESPECIALLY WHERE PRECIPITATION FALLS TODAY.

&&

.PREV DISCUSSION.../ISSUED 345 AM CDT THU JUL 21 2011/

FORECAST FOCUS OVER THE NEXT SEVEN DAYS WILL INVOLVE THE CONTINUING
SAGA OF THE BROAD, STRONG UPR RIDGE THAT IS NOW EXPANDING INTO THE
EASTERN CONUS. WEAK VORT MAXIMA WILL CONTINUE TO MOVE AROUND THE
PERIPHERY OF THE UPR RIDGE AND ACROSS THE TN VALLEY OVER THE NEXT
FEW DAYS...PROVIDING A FOCUS FOR SHOWER/TSTM DEVELOPMENT. THE TIMING
AND PRECISE LOCATION OF THESE REMAINS PROBLEMATIC AND STILL PRESENTS
A BIT OF A FCST CHALLENGE...ESPECIALLY WHEN TRYING TO DISCERN
FAVORED AREAS FOR CONVECTION. A WESTWARD RETREAT IN THE UPR RIDGE
STILL LOOKS LIKELY FOR EARLY/MID NEXT WEEK...AND MAY BE ENOUGH TO
ALLOW A WEAK SFC FRONT TO MOVE INTO THE REGION. THEN...CONSENSUS IS
BUILDING THAT THE UPR RIDGE WILL EXPAND AND STRENGTHEN BACK INTO THE
EASTERN CONUS AGAIN LATE NEXT WEEK.

FOR TODAY...WILL KEEP THE HEAT ADVISORY ONGOING FOR ALL AREAS
ALTHOUGH CLOUDS AND SHOWERS PRESENT A CAVEAT TO HEATING POTENTIAL.
THE PRESENCE OF DEEP CONVECTION IN CENTRAL AL AND UPSTREAM IN THE
CENTRAL/SOUTHERN APPS EARLY THIS MORNING BELIES THE PRESENCE OF A
COUPLE OF WEAK VORT MAXIMA. THE VORT MAX IN CENTRAL AL IS LIKELY TO
CONTINUE A GENERAL WESTERLY COURSE ARND THE BASE OF THE UPR
RIDGE...BUT THE ONE OVER THE APPS APPEARS POISED TO APPROACH THE
AREA LATER THIS AFTN. WHILE THE BEST LIFT IN ASSOC/W THIS FEATURE
WILL LIKELY STAY JUST TO OUR NORTH AND EAST...SHOWERS/TSTMS WILL
HAVE A TENDENCY FOR NE TO SW MOVEMENT TODAY. SO...SHOWERS/STORMS
DEVELOPING OUTSIDE OF OUR AREA MAY DRIFT IN LATE IN THE AFTN INTO
THE EARLY EVENING. NEVERTHELESS...SUFFICIENT SFC HEATING ALONG THE
EDGE OF THE UPR WAVE SHOULD PROVIDE ENOUGH SUPPORT FOR SCTD
CONVECTION MAINLY IN CENTRAL/EASTERN AREAS. THE BEST CHANCES OVERALL
WILL BE IN THE EAST AND NORTH...CLOSER TO THE EFFECTS OF THE VORT
MAX. DEPENDING ON HOW EARLY CONVECTION FIRES WILL LIMIT
HEATING...BUT IT MAY BE LATE ENOUGH SO THAT MOST LOCATIONS MEET OR
AT LEAST APPROACH HEAT ADVISORY CRITERIA. STILL HAVE MORE CONFIDENCE
THAT WESTERN/CENTRAL LOCATIONS WILL MEET CRITERIA...WITH HEAT
INDICES ARND 105 TO 108 EXPECTED.

THE VORT MAX...ALTHOUGH INCREASINGLY SHALLOW BY TONIGHT WILL CROSS
THE AREA. LIFT/INSTABILITY SHOULD BE SUFFICIENT TO ALLOW FOR
ISOLD/SCTD SHOWERS AND STORMS EXTENDING INTO THE OVERNIGHT PERIOD.
ALTHOUGH SHOWER/STORM COVERAGE MAY BE LIMITED...THE VERY HIGH
ATMOSPHERIC MOISTURE CONTENT -- PW VALUES ARND 2.2-2.4 INCHES! --
AND SLOW STORM MOTION MAY PRESENT A FLASH FLOOD THREAT THIS EVENING
AND TONIGHT. THIS WILL LIKELY BE THE MAIN WEATHER THREAT WITH ANY
STORMS. WILL ALSO LEAVE IN A MENTION OF PATCHY FOG DUE TO THE VERY
MOIST AND PERHAPS RAIN-COOLED AIRMASS IN SCTD LOCATIONS.

THE UPR RIDGE WILL EXPAND BRIEFLY EASTWARD TOWARD THE EAST COAST ON
FRIDAY...WHILE ANOTHER WEAK VORT MAX APPROACHES THE AREA FROM THE
SOUTH. THIS ALONG WITH DAYTIME HEATING WILL AGAIN INSTIGATE
SHOWER/TSTM DEVELOPMENT MAINLY DURING THE AFTERNOON. FAR SOUTHERN
AND FAR NORTHERN AREAS MAY BE FAVORED FOR DEVELOPMENT...GIVEN THE
UPR WAVE TO THE SOUTH AND THE PREVIOUS ONE STILL LINGERING JUST TO
OUR NORTH BY THAT TIME. CURRENTLY...TEMPS ARE FCST TO BE MAINLY IN
THE LOW/MID 90S AND COMBINED WITH THE HUMIDITY...HEAT INDICES ARE
FCST TO BE AROUND 100-105. FOR NOW...WILL NOT EXTEND THE HEAT
ADVISORY DUE TO THE MARGINAL CONDITIONS. HOWEVER...ANY INCREASES IN
TEMPS OR DEW POINTS BY THE DAY SHIFT MAY NECESSITATE THE EXTENSION
OF THE HEAT ADVISORY INTO FRIDAY.

CHANCES FOR MAINLY AFTERNOON/EVENING SHOWERS AND STORMS WILL LINGER
THROUGH THE WEEKEND WITH THE PRESENCE OF WEAK VORT MAXIMA STILL
REPRESENTED IN MED RANGE GUIDANCE. THE UPR RIDGE WILL BUILD BACK
QUICKLY INTO THE WESTERN STATES IN RESPONSE TO A VIGOROUS UPR LOW IN
WESTERN CANADA...AND THE LOSS OF SOME DEGREE OF SUBSIDENCE WILL
RESULT IN SLIGHTLY LOWER AIR TEMPS FOR THE WEEKEND. HOWEVER...THE
HUMID AIRMASS WILL REMAIN IN PLACE...AND HEAT INDICES WILL CONTINUE
TO BE ARND 100-105 DEGREES IN THE AFTERNOON. HEAT ADVISORIES MAY
STILL BE NEEDED DURING THIS PERIOD.

WITH THE UPR RIDGE MORE FIRMLY IN THE WESTERN/CENTRAL CONUS BY EARLY
NEXT WEEK...NW FLOW ALOFT MAY BE SUFFICIENT OVER THE OH/TN VALLEY
REGION TO ALLOW A WEAK SFC FRONT TO CROSS THE AREA ON MON OR TUES.
WITH THE ADDED POTENTIAL FOR DYNAMIC FORCING...WILL INCREASE POPS TO
HIGHER CHANCE CATEGORY FOR MONDAY. DUE TO UNCERTAINTY WITH REGARD TO
THE TIMING OF THE FRONTAL BOUNDARY...WILL LEAVE IN A LOWER CHANCE
POP FOR TUESDAY. ALTHOUGH...MOST CONVECTION WILL PROBABLY
EFFECTIVELY END BEHIND THE FRONTAL PASSAGE.

A BRIEF DROP IN DEW POINTS IS POSSIBLE ON WED IN THE POST FRONT
ENVIRONMENT...IF IT DOES END UP MAKING IT THIS FAR SOUTH. THIS
REMAINS TO BE DETERMINED...SO WILL ONLY DROP DEW POINTS INTO THE UPR
60S FOR NOW.

THEN...A RETURN TO VERY HIGH HEAT/HUMIDITY LOOKS SET FOR LATE NEXT
WEEK AND BEYOND AS THE UPR RIDGE EXPANDS BACK ACROSS THE EASTERN
CONUS.

&&

.HUN WATCHES/WARNINGS/ADVISORIES...

AL...NONE.

TN...NONE.

&&

UPDATE...70/DD
AVIATION...JLL
PREV DISCUSSION...KDW

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE HUNTSVILLE AL
1055 AM CDT THU JUL 21 2011

ALZ001>010-016-TNZ076-096-097-220000-
LAUDERDALE-COLBERT-FRANKLIN AL-LAWRENCE-LIMESTONE-MADISON-MORGAN-
MARSHALL-JACKSON-DEKALB-CULLMAN-MOORE-LINCOLN-FRANKLIN TN-
1055 AM CDT THU JUL 21 2011

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

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

HEAT INDEX VALUES WILL BRIEFLY APPROACH 105 DEGREES THROUGH THE
EARLY AFTERNOON HOURS IN SOUTHERN MIDDLE TN.

SHOWERS AND THUNDERSTORMS ARE EXPECTED THROUGH THE AFTERNOON AND
EVENING HOURS. SOME THUNDERSTORMS MAY BE CAPABLE OF PRODUCING STRONG
WIND GUSTS...SMALL HAIL...AND FREQUENT LIGHTNING. SOME ISOLATED
INSTANCES OF FLASH FLOODING ARE POSSIBLE DUE TO THE SLOW MOVMENT OF
THESE STORMS.

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

HOT TEMPERATURES AND HIGH HUMIDITY WILL LEAD TO HIGH HEAT INDICES ON
FRIDAY...AND PERHAPS LASTING INTO THE WEEKEND. HEAT INDEX VALUES WILL
LIKELY BE AROUND 100 TO 105 DEGREES IN MANY LOCATIONS...WHICH CAN
LEAD TO SERIOUS HEAT RELATED ILLNESSES.

ISOLATED TO SCATTERED THUNDERSTORMS ARE EXPECTED MAINLY DURING THE
AFTERNOON AND EVENING FROM FRIDAY THROUGH TUESDAY. GUSTY WINDS AND
FREQUENT LIGHTNING WILL BE POSSIBLE WITH THESE STORMS...BUT INSTANCES
OF FLASH FLOODING MAY RESULT FROM SLOW MOVING THUNDERSTORMS AND
LOCALLY HEAVY RAINFALL DURING THIS PERIOD.

.SPOTTER CALL TO ACTION STATEMENT...

ACTIVATION OF STORM SPOTTERS AND EMERGENCY MANAGEMENT PERSONNEL
IS NOT ANTICIPATED AT THIS TIME.

KTW

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE HUNTSVILLE AL
1033 AM CDT THU JUL 21 2011

ALZ006-009-211615-
JACKSON-MADISON-
1033 AM CDT THU JUL 21 2011

...SIGNIFICANT WEATHER ADVISORY FOR WESTERN JACKSON AND SOUTHERN
MADISON COUNTIES UNTIL 1115 AM CDT...

AT 1027 AM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING
SCATTERED STRONG THUNDERSTORMS NEAR FARLEY AND TRENTON...MOVING WEST
AT 10 MPH.

WINDS UP TO 40 MPH...FREQUENT CLOUD TO GROUND LIGHTNING...AND HEAVY
DOWNPOURS ARE EXPECTED WITH THESE STORMS.

* LOCATIONS IN OR NEAR THE PATH INCLUDE...
  FARLEY.
  REDSTONE ARSENAL.
  TRIANA...MADISON.

STAY TUNED TO NOAA WEATHER RADIO...COMMERCIAL RADIO...OR YOUR LOCAL
TELEVISION STATIONS FOR LATER STATEMENTS AND POSSIBLE WARNINGS
CONCERNING THIS WEATHER SITUATION.

&&

LAT...LON 3464 8619 3459 8660 3456 8668 3458 8668
      3459 8670 3456 8674 3456 8678 3477 8679
      3490 8630
TIME...MOT...LOC 1532Z 068DEG 8KT 3462 8656

KTW

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE HUNTSVILLE AL
1102 AM CDT THU JUL 21 2011

ALZ006-211645-
MADISON-
1102 AM CDT THU JUL 21 2011

...SIGNIFICANT WEATHER ADVISORY FOR NORTHEASTERN MADISON COUNTY
UNTIL 1145 AM CDT...

AT 1100 AM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING
A STRONG THUNDERSTORM NEAR MAYSVILLE...MOVING SOUTHWEST AT 5 MPH.

NICKEL SIZE HAIL...HEAVY RAINFALL...WINDS UP TO 50 MPH...AND
FREQUENT LIGHTNING ARE EXPECTED WITH THIS STORM.

* LOCATIONS IN OR NEAR THE PATH INCLUDE...
  MAYSVILLE.

STAY TUNED TO NOAA WEATHER RADIO...COMMERCIAL RADIO...OR YOUR LOCAL
TELEVISION STATIONS FOR LATER STATEMENTS AND POSSIBLE WARNINGS
CONCERNING THIS WEATHER SITUATION.

&&

LAT...LON 3473 8641 3480 8655 3485 8642 3481 8638
TIME...MOT...LOC 1601Z 029DEG 4KT 3481 8643

KTW

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE HUNTSVILLE AL
1111 AM CDT THU JUL 21 2011

ALZ009-TNZ097-211700-
FRANKLIN-JACKSON-
1111 AM CDT THU JUL 21 2011

...SIGNIFICANT WEATHER ADVISORY FOR FRANKLIN AND JACKSON COUNTIES
UNTIL NOON CDT...

AT 1110 AM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING
SCATTERED STRONG THUNDERSTORMS EXTENDING FROM JUST EAST OF SHERWOOD
TO PRINCETON...MOVING SOUTHWEST AT 10 MPH.

NICKEL SIZE HAIL...WINDS UP TO 40 MPH...FREQUENT CLOUD TO GROUND
LIGHTNING...AND HEAVY DOWNPOURS ARE EXPECTED WITH THESE STORMS.

* LOCATIONS IN OR NEAR THE PATH INCLUDE...
  SHERWOOD.
  ANDERSON.
  BASS.
  JERICHO...HYTOP.

STAY TUNED TO NOAA WEATHER RADIO...COMMERCIAL RADIO...OR YOUR LOCAL
TELEVISION STATIONS FOR LATER STATEMENTS AND POSSIBLE WARNINGS
CONCERNING THIS WEATHER SITUATION.

&&

LAT...LON 3519 8586 3500 8586 3498 8584 3462 8634
      3490 8633 3491 8631 3494 8632 3494 8629
      3492 8627 3493 8626 3494 8626 3497 8631
      3499 8631 3520 8587
TIME...MOT...LOC 1609Z 048DEG 10KT 3507 8588

KTW

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE HUNTSVILLE AL
1143AM CDT THU JUL 21 2011

ALZ006-TNZ096-211730-
LINCOLN-MADISON-
1144 AM CDT THU JUL 21 2011

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHERN LINCOLN AND NORTHERN
MADISON COUNTIES UNTIL 1230 PM CDT...

AT 1143 AM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING A
STRONG THUNDERSTORM NEAR NEW MARKET...MOVING WEST AT 10 MPH.

WINDS UP TO 50 MPH...DIME SIZE HAIL...FREQUENT CLOUD TO GROUND
LIGHTNING...AND HEAVY DOWNPOURS ARE EXPECTED WITH THIS STORM.

* LOCATIONS IN OR NEAR THE PATH INCLUDE...
  ELORA.
  NEW MARKET...DEPOSIT.
  MOORES MILL...HAZEL GREEN.

STAY TUNED TO NOAA WEATHER RADIO...COMMERCIAL RADIO...OR YOUR LOCAL
TELEVISION STATIONS FOR LATER STATEMENTS AND POSSIBLE WARNINGS
CONCERNING THIS WEATHER SITUATION.

&&

LAT...LON 3502 8634 3479 8635 3473 8664 3511 8675
TIME...MOT...LOC 1641Z 108DEG 8KT 3488 8636

KTW

SPECIAL WEATHER STATEMENT...CORRECTED
NATIONAL WEATHER SERVICE HUNTSVILLE AL
1145 AM CDT THU JUL 21 2011

ALZ006-TNZ096-211730-
LINCOLN-MADISON-
1145 AM CDT THU JUL 21 2011

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHERN LINCOLN AND NORTHERN
MADISON COUNTIES UNTIL 1230 PM CDT...

AT 1143 AM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING A
STRONG THUNDERSTORM NEAR NEW MARKET...MOVING WEST AT 10 MPH.

WINDS UP TO 50 MPH...DIME SIZE HAIL...FREQUENT CLOUD TO GROUND
LIGHTNING...AND HEAVY DOWNPOURS ARE EXPECTED WITH THIS STORM.

* LOCATIONS IN OR NEAR THE PATH INCLUDE...
  ELORA.
  NEW MARKET...DEPOSIT.
  MOORES MILL...HAZEL GREEN.

STAY TUNED TO NOAA WEATHER RADIO...COMMERCIAL RADIO...OR YOUR LOCAL
TELEVISION STATIONS FOR LATER STATEMENTS AND POSSIBLE WARNINGS
CONCERNING THIS WEATHER SITUATION.

&&

LAT...LON 3502 8634 3479 8635 3473 8664 3511 8675
TIME...MOT...LOC 1641Z 108DEG 8KT 3488 8636

KTW

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE HUNTSVILLE AL
1211 PM CDT THU JUL 21 2011

ALZ009-TNZ097-211745-
FRANKLIN-JACKSON-
1211 PM CDT THU JUL 21 2011

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN FRANKLIN AND
NORTHWESTERN JACKSON COUNTIES UNTIL 1245 PM CDT...

AT 1205 PM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING
AN AREA OF STRONG THUNDERSTORMS EXTENDING FROM SHERWOOD TO
FRANCISCO...MOVING NORTHWEST AT 10 MPH.

WINDS UP TO 40 MPH...FREQUENT CLOUD TO GROUND LIGHTNING...AND HEAVY
DOWNPOURS ARE EXPECTED WITH THIS STORM.

* LOCATIONS IN OR NEAR THE PATH INCLUDE...
  MAXWELL.
  COWAN.
  FRANCISCO.
  BEANS CREEK...HUNTLAND.

STAY TUNED TO NOAA WEATHER RADIO...COMMERCIAL RADIO...OR YOUR LOCAL
TELEVISION STATIONS FOR LATER STATEMENTS AND POSSIBLE WARNINGS
CONCERNING THIS WEATHER SITUATION.

&&

LAT...LON 3499 8586 3482 8618 3493 8626 3494 8626
      3495 8628 3501 8632 3504 8632 3521 8586
TIME...MOT...LOC 1708Z 150DEG 10KT 3515 8584

KTW