Area Forecast Discussion
Issued by NWS Huntsville, AL

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000
FXUS64 KHUN 141042
AFDHUN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HUNTSVILLE AL
542 AM CDT MON JUL 14 2014

.DISCUSSION...
QUIET CONDITIONS ARE CURRENTLY OBSERVED ACROSS THE CENTRAL TENNESSEE
VALLEY THIS MORNING...WITH PARTLY CLOUDY SKIES AND TEMPERATURES
NEARLY STEADY IN THE LOWER 70S. WE ARE MONITORING DEVELOPING
CONVECTION TO THE SOUTHEAST OF THE AREA /ASSOCIATED WITH
STRENGTHENING LOW-LEVEL WARM ADVECTION/ AS WELL AS MORE WIDESPREAD
RAIN AND STORMS TO THE NORTHWEST OF THE AREA. AS A STRONG UPPER LOW
CURRENTLY DIGGING SOUTHEASTWARD ACROSS NORTHERN MINNESOTA CONTINUES
TO SHIFT SOUTHWARD INTO THE WESTERN GREAT LAKES...GRADUAL HEIGHT
FALLS ALOFT WILL PROVIDE AN ENVIRONMENT MORE CONDUCIVE FOR SHOWERS
AND THUNDERSTORMS TODAY. BASED ON THIS REASONING AND INDICATIONS IN
SOME OF THE HIGH RESOLUTION MODEL GUIDANCE THAT A WEAK LOW-LEVEL
CONVERGENCE AXIS WILL DRIFT SOUTHWARD INTO THE REGION THIS
AFTERNOON...WE WILL CONTINUE TO ADVERTISE 40-60 PERCENT POPS DESPITE
A LACK OF SYNOPTIC SCALE ASCENT IN THE MID/UPPER-LEVELS. MODELS
CONTINUE TO SUGGEST THAT DEEP-LAYER SHEAR WILL REMAIN GENERALLY WEAK
ACROSS THE REGION TODAY WITH VALUES IN THE 15-20 KNOT RANGE.
HOWEVER...TEMPERATURES IN THE LOWER/MID 90S AND DEWPOINTS IN THE
LOWER 70S WILL LEAD TO VERY UNSTABLE CONDITIONS THIS AFTERNOON WITH
CAPES IN THE 2000-3000 J/KG RANGE. THUS...WE ARE STILL EXPECTING AN
ELEVATED THREAT FOR SEVERE THUNDERSTORMS WITH DAMAGING WINDS/LARGE
HAIL THE PRIMARY THREATS.

A SEPARATE ROUND OF CONVECTION WILL DEVELOP ALONG THE ACTUAL COLD
FRONT AS IT APPROACHES THE AREA FROM THE NORTHWEST OVERNIGHT. DEEP-
LAYER SHEAR WILL INCREASE TO 20-30 KNOTS DURING THIS PERIOD...AND THE
ATMOSPHERE WILL LIKELY REMAIN SUFFICIENTLY UNSTABLE /CAPES OF
500-1500 J/KG/ TO SUPPORT A THREAT FOR SEVERE STORMS OVERNIGHT.
HOWEVER...THE THREAT MAY SLOWLY TRANSITION FROM SEVERE TO HEAVY
RAINFALL/FLASH FLOODING BY EARLY TUESDAY MORNING. THE COLD FRONT IS
EXPECTED TO BE LOCATED FROM MIDDLE TENNESSEE SOUTHWESTWARD INTO
NORTHERN MISSISSIPPI AT 12Z TUESDAY AND SHOULD MAKE STEADY SOUTHWARD
PROGRESS -- EXITING THE SOUTHEASTERN COUNTIES BETWEEN 18-21Z. A
CANADIAN SURFACE HIGH WILL SETTLE SOUTHWARD ACROSS THE NORTHERN
PLAINS/UPPER MISSISSIPPI VALLEY FROM TUESDAY THROUGH WEDNESDAY...WITH
DEWPOINTS IN THE LOWER 50S BEING ADVECTED INTO THE REGION BY LIGHT
NORTHERLY WINDS. THE COMBINATION OF CLOUDS/PRECIPITATION AND WEAK
COLD ADVECTION WILL RESULT IN HIGHS IN THE LOWER/MID 80S TUESDAY...
WITH TEMPERATURES REMARKABLY A FEW DEGREES COOLER ON WEDNESDAY EVEN
WITH STRONG AFTERNOON INSOLATION. LOWS ON TUESDAY NIGHT WILL FALL
INTO THE UPPER 50S/LOWER 60S AS SKIES CLEAR BY LATE EVENING.

IT STILL APPEARS AS IF MID-LEVEL WINDS WILL BACK TO THE SOUTHWEST ON
THURSDAY...AS THE INITIAL LONGWAVE TROUGH AXIS LIFTS NORTHEASTWARD
AND THE ATLANTIC SUBTROPICAL RIDGE BUILDS NORTHWESTWARD INTO THE
SOUTHERN GULF OF MEXICO. A FEW WEAK MID-LEVEL WAVES WILL SPREAD
ACROSS THE REGION WEDNESDAY NIGHT...BUT THE LOWER/MIDDLE TROPOSPHERE
WILL REMAIN TOO DRY TO SUPPORT ANYTHING MORE THAN AN INCREASE IN
CLOUD COVER. THE GFS/ECMWF/GEM HAVE COME INTO BETTER AGREEMENT
NOW...IN SUGGESTING FAIRLY SIGNIFICANT IMPACTS BY LATE IN THE WORK
WEEK FROM A MORE PRONOUNCED MID-LATITUDE TROUGH -- WHICH SHOULD BE
MOVING EASTWARD ACROSS THE CENTRAL PLAINS ON THURSDAY. ALTHOUGH THE
STRONGEST PORTION OF THIS WAVE AND FORCING FOR UVM WILL LIKELY REMAIN
TO THE NORTH OF OUR AREA...SEVERAL LOWER AMPLITUDE FEATURES IN THE
SOUTHWEST FLOW ALOFT WILL TRACK ACROSS THE REGION ENHANCING DEEP-
LAYER ASCENT FROM THURSDAY NIGHT THROUGH SATURDAY MORNING. A
RELATIVELY DRY AIRMASS WILL REMAIN ENTRENCHED AT THE SURFACE THROUGH
THURSDAY NIGHT...SUPPORTING MAINLY ELEVATED CONVECTION AS MID-LEVEL
LAPSE RATES BEGIN TO STEEPEN. AS A WEAK SURFACE LOW SHIFTS
NORTHEASTWARD FROM THE ARKLATEX INTO NORTHERN KENTUCKY BY SATURDAY
MORNING...MOIST AND UNSTABLE AIR WILL RETURN TO THE CENTRAL TENNESSEE
VALLEY FRIDAY WITH NUMEROUS SHOWERS/STORMS EXPECTED FROM FRIDAY INTO
FRIDAY NIGHT. ALTHOUGH DEEP-LAYER SHEAR WILL BE MARGINAL FOR THE
DEVELOPMENT OF ORGANIZED CONVECTION...THE SOUTHWESTERLY LOW- LEVEL
JET WILL INCREASE TO 35-40 KNOTS AND THIS MAY LEAD TO ANOTHER
ELEVATED THREAT FOR STRONG/SEVERE STORMS. THE MID-LEVEL TROUGH AXIS
WILL SHIFT EASTWARD ON SATURDAY...WITH THE COLD FRONT/SURFACE TROUGH
ATTACHED TO THE NORTHERN KENTUCKY SURFACE LOW BECOMING INCREASINGLY
DIFFUSE. WILL RETURN POPS TO CLIMO VALUES FOR THE SECOND HALF OF NEXT
WEEKEND...WITH TEMPERATURES REBOUNDING INTO THE UPPER 80S/LOWER 90S
BY SUNDAY AND MONDAY.

70/DD

&&

.AVIATION...
/ISSUED 1230 AM CDT MON JUL 14 2014/
FOR 06Z TAFS...VFR CONDITIONS WILL PREVAIL AT KHSV AND KMSL THROUGH
THE TAF PERIOD. SOUTHWESTERLY WINDS WILL PICK BACK UP TO 10KTS WITH
SHOWERS AND THUNDERSTORMS DEVELOPING AROUND 22Z. STORMS WILL INCREASE
IN COVERAGE AS THE COLD FRONT MOVES INTO THE AREA. TIMING OF THE
FRONT IS STILL UNCERTAIN ATTM. MVFR CONDITIONS COULD BE POSSIBLE IN
THE STRONGER STORMS.

JMS/KTW

&&

.PRELIMINARY POINT TEMPS/POPS...
HUNTSVILLE    93  71  85  60 /  40  90  60  10
SHOALS        94  71  84  59 /  50  90  40  10
VINEMONT      92  70  84  60 /  40  90  70  10
FAYETTEVILLE  92  69  82  58 /  60  90  50  10
ALBERTVILLE   90  70  83  62 /  40  90  80  10
FORT PAYNE    91  70  83  60 /  40  90  80  10

&&

.HUN WATCHES/WARNINGS/ADVISORIES...

AL...NONE.

TN...NONE.

&&

$$

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



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