070 
FXUS64 KHUN 241120 AAA
AFDHUN

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE HUNTSVILLE AL
620 AM CDT MON JUN 24 2013

.UPDATE...
FOR 12Z TAFS 

&& 

.DISCUSSION...
/ISSUED 518 AM CDT MON JUN 24 2013/
CURRENT WATER VAPOR SATELLITE ANIMATION INDICATES THAT A BROAD/WEAK
CYCLONIC FLOW ALOFT REMAINS IN PLACE ACROSS NORTHERN ALABAMA AND
SOUTHERN MIDDLE TENNESSEE THIS MORNING -- AS THE REGION IS LOCATED
BETWEEN A MID-LEVEL HIGH CENTERED OFF THE SOUTHEAST ATLANTIC COAST
AND A SHORTWAVE TROUGH EXTENDING FROM THE LOWER OHIO VALLEY SOUTH-
SOUTHWESTWARD INTO THE LOWER MISSISSIPPI VALLEY. OVER THE COURSE OF
THE DAY...SHORT TERM NWP GUIDANCE SUGGESTS THAT THE EASTERN SEABOARD
RIDGE WILL BEGIN TO RETROGRADE ACROSS FLORIDA/GEORGIA...WITH THE
SHORTWAVE TROUGH EXPECTED TO ADVANCE EASTWARD ACROSS THE FORECAST
AREA. ALTHOUGH THE STRONGEST LARGE SCALE FORCING FOR ASCENT WILL
LIKELY OCCUR TO THE NORTH OF THE REGION...AT LEAST WIDELY SCATTERED
CONVECTION IS EXPECTED TO DEVELOP AS WEAK LIFT OCCURS WITHIN THE
INCREASINGLY MOIST AIRMASS /PWAT VALUES NOW IN THE 1.4-1.6 INCH
RANGE/. WE ARE ONLY EXPECTING ACTIVITY TO BE ISOLATED/WIDELY
SCATTERED AT MOST...BUT POPS WERE INCREASED A BIT ACROSS NORTHWEST
ALABAMA -- WHERE AN OUTFLOW BOUNDARY MAY APPROACH FROM THE NORTHWEST
AND SERVE AS A FOCUS FOR DEVELOPING CONVECTION. A LOW CHANCE OF
SHOWERS/STORMS WAS RETAINED FOR MOST OF THE AREA THIS EVENING...AS
STRENGTHENING NORTH/NORTHWEST FLOW ALOFT IN THE WAKE OF THE DEPARTING
MID-LEVEL TROUGH AXIS MAY ALLOW LATE AFTERNOON CONVECTION ACROSS
MIDDLE AND EASTERN TENNESSEE TO SPREAD SOUTHWARD INTO THE REGION.
HAVE FORECASTED HIGH TEMPERATURES TODAY TO BE A DEGREE OR SO
COOLER...WITH EXPECTATIONS OF THICKER MORNING CLOUD COVER AND MORE
SHOWER/THUNDERSTORM ACTIVITY THIS AFTERNOON. LOWS TONIGHT WILL ONCE
AGAIN BE AROUND 70 FOR MOST LOCATIONS.

DURING THE PERIOD FROM TUESDAY THROUGH TUESDAY NIGHT...MODELS AGREE
THAT THE MID-TROPOSPHERIC SUBTROPICAL RIDGE WILL CONTINUE TO
RETROGRADE ALONG THE GULF COAST...AND BECOME CENTERED ACROSS NORTHERN
SONORA/NORTHERN CHIHUAHUA BY TUESDAY EVENING. SEVERAL LOW AMPLITUDE
500-MB WAVES WILL ADVANCE EASTWARD ACROSS THE LOWER GREAT LAKES
REGION DURING THIS PERIOD...BUT DEEP-LAYER FORCING ASSOCIATED WITH
THESE FEATURES WILL BE VERY WEAK THIS FAR TO THE SOUTH. A LOW CHANCE
FOR SHOWERS/STORMS WILL BE MAINTAINED ON TUESDAY AFTERNOON...BASED ON
EXPECTATIONS OF AN EVEN MORE MOIST AIRMASS IN PLACE ACROSS THE LOCAL
AREA...BUT THIS MAY EVEN BE TOO OPTIMISTIC. HOWEVER...SHOWER AND
THUNDERSTORM CHANCES WILL INCREASE MORE SUBSTANTIALLY ON WEDNESDAY
THE SUBTROPICAL RIDGE IS FORECAST TO INTENSIFY AND BUILD NORTHWARD
INTO ARIZONA/NEW MEXICO -- INDUCING WEAK NORTHWEST FLOW ALOFT ACROSS
THE TENNESSEE VALLEY. GLOBAL MODELS INDICATE THAT A STRONGER MID-
LEVEL DISTURBANCE WILL DIG SOUTHEASTWARD ACROSS THE AREA ON
WEDNESDAY...LEADING TO A HIGHER COVERAGE OF CONVECTION AND
POTENTIALLY BRINGING A GREATER THREAT FOR STRONG STORMS AS MID-LEVEL
NORTHWEST FLOW WILL INCREASE TO 20-25 KNOTS DURING THE AFTERNOON.

MEDIUM RANGE GUIDANCE CONTINUES TO ADVERTISE A HIGHLY AMPLIFIED
LONGWAVE PATTERN BECOMING ESTABLISHED ACROSS THE CONUS FOR THE
REMINDER OF THE WEEK/UPCOMING WEEKEND...AS THE WESTERN U.S. RIDGE
AMPLIFIES FURTHER AND BUILDS NORTHWARD INTO UTAH/COLORADO WHILE A
STRONG UPPER CYCLONE DIGS SOUTHEASTWARD ACROSS ONTARIO AND THE GREAT
LAKES. AN EVEN STRONGER MID-LEVEL SHORTWAVE WILL LIKELY IMPACT THE
REGION ON THURSDAY/THURSDAY NIGHT...BRINGING ANOTHER ROUND OF SHOWERS
AND STORMS. AFTER A BRIEF RESPITE ON FRIDAY...ANOTHER EVEN MORE
ROBUST WAVE WILL BRING A MORE WIDESPREAD COMPLEX OF CONVECTION TO THE
REGION ON FRIDAY NIGHT. DEEP-LAYER SHEAR AND INSTABILITY PARAMETERS
INDICATE THAT EACH ROUND OF STORMS WILL HAVE THE CAPABILITY TO
PRODUCE SEVERE WEATHER...WITH DAMAGING WINDS BEING THE PRIMARY
HAZARD. THE PASSAGE OF A WEAK COLD FRONT WILL LIKELY END THE THREAT
FOR SIGNIFICANT SHOWER/THUNDERSTORM ACTIVITY BY SATURDAY EVENING...
BUT A SLIGHT CHANCE POP WILL BE RETAINED THROUGH THE END OF THE
FORECAST PERIOD AS THE FRONT MAY STALL NEAR THE FORECAST AREA. AFTER
WARMING INTO THE LOWER/MID 90S ON WEDNESDAY-FRIDAY...HIGHS WILL FALL
BACK INTO THE UPPER 80S OVER THE WEEKEND...WITH LOWS DROPPING INTO
THE MID 60S BY SATURDAY/SUNDAY.

70/DD

&&

.AVIATION...
FOR 12Z TAFS... MOIST SOUTHERLY FLOW JUST ABOVE THE SURFACE HAS 
LED TO THE DEVELOPMENT OF LOW CLOUD DECKS.  CIGS ARE IN THE IFR
AND MVFR RANGE DEPENDING ON THE LOCATION. AT THIS TIME, HAVE
FORECASTED MVFR CONDS AT KHSV UNTIL 15Z. CIGS HAVE A LOWER CHC OF
ARRIVING AT KMSL, SO HAVE GONE WITH A TEMPO GROUP THERE. ISOLATED TO
SCATTERED TS ARE EXPECTED TO DEVELOP BY THIS AFTN. THE PROBS ARE TOO
LOW TO INCLUDE AT EITHER TAF SITE ATTM. THE STRONGER STORMS WILL BE
CAPABLE OF +RA, BRIEF GUSTY WINDS, AND FQT LIGHTNING STRIKES.

AK

&&

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

$$ 

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