Area Forecast Discussion
Issued by NWS Huntsville, AL

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000
FXUS64 KHUN 141722 AAB
AFDHUN

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE HUNTSVILLE AL
1122 AM CST SUN FEB 14 2016

.UPDATE...
UPDATED WX/POPS...CLOUD COVER...AND HOURLY TEMPS FOR TODAYS
FORECAST AND FOR 18Z TAFS.

&&

.DISCUSSION...
OVERNIGHT LOWS IN THE LOWER 20S HAVE WARMED UP INTO THE MID 30S WITH
BKN/OVC CLOUD COVER CURRENT ACROSS THE TN VALLEY. DEWPOINTS HAVE
CLIMBED OUT OF THE SINGLE DIGITS IN A FEW LOCATIONS SINCE EARLIER
THIS MORNING...BUT THE LARGE DEWPOINT SPREAD IS STILL PROVING TOO
MUCH FOR PRECIP TO REACH THE GROUND.

PUSHED BACK THE ARRIVAL OF THE PRECIP...COMPLETELY REMOVED THE
FREEZING RAIN AND MOST OF THE SLEET AS SOUTHEASTERLY WINDS ARE
ALREADY IN PLACE. DID LEAVE IN A SHORT PERIOD OF TIME FOR SLEET IN
SOUTHERN MIDDLE TN FOR EARLY THIS AFTN WHERE TEMPS ARE FAVORABLE AND
SOUNDINGS SHOW THE WETBULB COULD ASSIST WITH FURTHER COOLING. WITH
FROZEN OR LIQUID PRECIP...WE STILL NEED TO GET PAST THE DRIER AIR IN
THE LOWER LEVELS. WITH THE CLOSEST SFC OBS CURRENTLY REPORTING
PRECIP BEING ALL THE WAY UP IN SW TN...MAY HAVE TO DELAY AGAIN IN
ANOTHER UPDATE. OTHERWISE...EXPECT BREEZY CONDITIONS WITH GUSTS AT
TIMES UP TO 25MPH...OVC SKIES AND TEMPS IN THE 40S TODAY.

JMS

&&

.AVIATION...
FOR 18Z TAFS...EVEN WITH PREDOM OVC SKIES AROUND 4-5K FT IN PLACE
ACROSS MOST OF THE AREA...VFR CONDS PREVAIL FOR NOW AS LITTLE CHANGE
IN THESE CLOUD BASES IS XPCTED INTO THE EVENING HRS. MOST OF THE
LIGHT PRECIP ALSO LOOKS TO REMAIN N OF THE TWO MAIN TERMINALS FOR
THE NEXT SEVERAL HRS. CLOUD BASES MAY BEGIN TO LOWER INTO THE MVFR
CAT HEADING INTO THE OVERNIGHT PERIOD...AS -RA BEGINS TO SPREAD SWD
ACROSS MUCH OF THE AREA. SFC WINDS LOOK TO REMAIN OUT OF THE SSE
NEAR 10-12KT FOR THE MAJORITY OF THE TAF PERIOD.

09

&&

.PREV DISCUSSION...
/ISSUED 625 AM CST SUN FEB 14 2016/
WATER VAPOR SATELLITE ANIMATION DEPICTS A STRONG 500-MB SHORTWAVE
TROUGH DIGGING SOUTHEASTWARD INTO THE MISSOURI VALLEY THIS
MORNING...WITH A SERIES OF LOWER AMPLITUDE DISTURBANCES TRACKING
EAST-SOUTHEASTWARD ACROSS THE RED RIVER VALLEY REGION OF OK/TX.
ACROSS THE LOCAL AREA...MID/UPPER-LEVEL FLOW CONTINUES TO GRADUALLY
BACK TO THE WEST THIS MORNING IN RESPONSE TO THE MOTION OF THE
CENTRAL PLAINS TROUGH. THE STEADY STREAM OF HIGH CLOUDS PROVIDED BY
THIS FLOW -- COUPLED WITH A LIGHT EASTERLY WIND AT THE SURFACE -- HAS
PREVENTED TEMPERATURES FROM DROPPING BELOW THE MID 20S FOR MOST OF
THE REGION. WE ARE CURRENTLY MONITORING THE RAPID DEVELOPMENT OF
CONVECTIVE PRECIPITATION ACROSS THE OZARKS...WHICH HAS BEEN
INSTIGATED BY INTENSE LOW-LEVEL WARM ADVECTION TO THE SOUTH/EAST OF
THE MISSOURI VALLEY TROUGH. THIS ACTIVITY WILL CONTINUE TO
DEVELOP/SPREAD EASTWARD THROUGH THE MORNING HOURS -- POTENTIALLY
IMPACTING LOCATIONS ALONG AND NORTH OF THE TENNESSEE RIVER LATER
TODAY.

HOWEVER...AT LEAST FOR THE FIRST FEW HOURS OF THE MORNING PERIOD...WE
EXPECT DRY CONDITIONS ACROSS THE LOCAL AREA. A GRADUAL INCREASE IN
CLOUD COVER AND LOWERING OF CLOUD BASES IN RESPONSE TO ELEVATED WARM
ADVECTION WILL PREVENT AN APPRECIABLE RISE IN TEMPERATURES -- WITH
MOST OF THE AREA LIKELY REMAINING NEAR OR BELOW FREEZING UNTIL
EARLY/MID AFTERNOON. OVER THE COURSE OF THE DAY...A STRONGER SOUTH-
SOUTHEAST FLOW WILL DEVELOP AS A CONSOLIDATED REGION OF SURFACE
PRESSURE FALLS DEVELOPS ACROSS NORTH CENTRAL TEXAS -- AND THIS SHOULD
ALLOW MOST OF THE REGION TO CRAWL ABOVE FREEZING DURING THE FIRST
PART OF THE AFTERNOON. IN FACT HIGH TEMPERATURES WILL LIKELY OCCUR
CLOSE TO 23Z FOR MOST FORECAST ZONES. MEANWHILE...AS CONVECTIVE
PRECIPITATION CURRENTLY DEVELOPING TO THE WEST SPREADS EASTWARD...
THE SOUTHERN FRINGES OF THIS ACTIVITY MAY CLIP LOCATIONS NORTH OF THE
TENNESSEE RIVER -- WITH PROBS HIGHEST TO THE NORTH OF U.S. 64 IN
TENNESSEE AND LOWEST SOUTH OF THE TENNESSEE RIVER WHERE LIFT WILL BE
INSUFFICIENT TO OVERCOME THE DRY BOUNDARY LAYER AIRMASS. INSPECTION
OF FORECAST SOUNDINGS SUGGESTS THAT ANY LATE MORNING/EARLY AFTERNOON
PRECIP WOULD LIKELY COME AS FREEZING RAIN OVER NORTHWEST AL...A
MIXTURE OF FREEZING RAIN AND SLEET OVER NC/NE ALABAMA AND A MIXTURE
OF SLEET AND SNOW ACROSS SOUTHERN MIDDLE TENNESSEE. GIVEN VERY LOW
DEWPOINT DEPRESSIONS AND LITTLE TO NO MOISTURE RECOVERY ANTICIPATED
PRIOR TO THE ONSET OF PRECIPITATION...INTENSITY WILL BE VERY LIGHT
WITH LITTLE TO NO ACCUMULATION.

BY THIS EVENING...MODELS CONTINUE TO SUGGEST AMPLIFICATION OF THE
MID/UPPER-LEVEL LONGWAVE TROUGH TO THE WEST -- AS A POWERFUL VORT
MAX DROPS SOUTHEASTWARD OVER THE CENTRAL HIGH PLAINS AND INTO KS/OK.
THIS WILL FORCE A SURFACE WAVE OVER NORTH CENTRAL TEXAS TO DEEPEN AND
MIGRATE EASTWARD INTO THE ARKLATEX REGION BY 12Z MONDAY. WARM FRONT
EXTENDING EASTWARD FROM THIS FEATURE WILL LIKELY SETUP JUST NORTHWEST
OF THE FORECAST AREA OVERNIGHT...AND FOCUS A FAIRLY WIDESPREAD SWATH
OF HEAVIER RAIN AND EMBEDDED THUNDERSTORMS ACROSS THE NORTHWESTERN
HALF OF THE REGION WHERE MUCAPE VALUES UP TO 250-500 J/KG WILL BE
PRESENT. HOWEVER...BASED ON STRENGTH OF ELEVATED WARM/MOIST
ADVECTION REGIME AND POTENTIAL FOR ASCENT TO BE AUGMENTED BY A
WEAKER VORT MAX EJECTING NORTHEASTWARD OUT OF THE LONGWAVE
TROUGH...FAIRLY HIGH POPS HAVE BEEN INCLUDED FOR THE ENTIRE AREA -
PRIMARILY FOR THE PERIOD FROM 06-12Z.

FORCING FOR ASCENT WILL INCREASE FURTHER DURING THE DAY ON MONDAY AS
THE LONGWAVE TROUGH MIGRATES EASTWARD AND DEEPENING SURFACE LOW
TRACKS EAST-NORTHEASTWARD ACROSS THE LOWER MISSISSIPPI VALLEY AND
INTO NORTH/CENTRAL ALABAMA. FORECAST SOUNDINGS SUGGEST FAVORABLE
MUCAPE FOR A FEW EMBEDDED THUNDERSTORMS -- ALTHOUGH COVERAGE OF
STORMS MAY BE A BIT HIGHER THAN THIS ACROSS THE SOUTHEAST COUNTIES
WHERE WARM SECTOR WILL BECOME MORE ESTABLISHED. LOCALLY HEAVY
RAINFALL MAY LEAD TO A FEW INSTANCES OF FLOODING AS PWATS WILL BE IN
THE 1-1.25 INCH RANGE...BUT GIVEN BRIEF NATURE OF HEAVY RAIN A
HYDROLOGIC WATCH WILL NOT BE ISSUED AT THIS POINT. THE SURFACE LOW IS
PROGGED TO DEEPEN FURTHER AND ACCELERATE INTO THE MID-ATLANTIC REGION
MONDAY NIGHT AS THE MID-LEVEL TROUGH AXIS BECOMES NEGATIVELY-
TILTED...AND THUS WE ANTICIPATE A FAIRLY RAPID END TO PRECIPITATION
FROM WEST-TO-EAST EARLY MONDAY EVENING. HOWEVER...THIS WILL LIKELY
NOT OCCUR BEFORE 00Z TUESDAY -- AND WILL WARRANT A CONTINUATION OF
HIGH POPS FOR THE EAST BEFORE 06Z. ATTENTION ON TUESDAY WILL BE
FOCUSED ON ANOTHER MID-LEVEL VORT MAX DIGGING SOUTHEASTWARD ACROSS
THE NORTHERN PLAINS AND INTO THE WESTERN SIDE OF THE LONGWAVE TROUGH
ON MONDAY NIGHT. THIS FEATURE WILL REACH THE OHIO/TENNESSEE VALLEY
LATE TUESDAY AFTERNOON -- PERHAPS BRINGING ANOTHER ROUND OF SHOWERS.
THE STRONGEST FORCING FOR ASCENT STILL APPEARS TO BE NORTH OF THE
REGION...WITH POPS HIGHEST FOR LOCATIONS NORTH OF THE TN RIVER ONCE
AGAIN. BEYOND THIS POINT...A WEAK RIDGE OF HIGH PRESSURE WILL BUILD
INTO THE REGION BEGINNING TUESDAY NIGHT...WITH LIGHT/VARIABLE FLOW
BECOMING CONDUCIVE FOR FOG BOTH TUESDAY NIGHT AND WEDNESDAY NIGHT. A
STRONG WARMING TREND WILL BECOME ESTABLISHED BY THURSDAY AS
SUBTROPICAL RIDGE BUILDS NORTHWARD FROM CENTRAL MEXICO...WITH LOWS
WARMING INTO THE MID 50S BY NEXT WEEKEND AND HIGHS REACHING THE UPPER
60S/LOWER 70S FRIDAY AND SATURDAY. A WEAK COLD FRONT RELATED TO
NORTHERN STREAM TROUGH SPREADING OVER THE GREAT LAKES WILL APPEARS TO
STALL JUST NORTH OF THE REGION...BUT MAY ENHANCE WARM/MOIST ADVECTION
ENOUGH FOR A FEW SHOWERS/THUNDERSTORMS NEXT FRIDAY NIGHT/SATURDAY.

70/DD

&&

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

$$

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


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