Area Forecast Discussion
Issued by NWS Huntsville, AL

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS64 KHUN 301116
AFDHUN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HUNTSVILLE AL
616 AM CDT WED JUL 30 2014

.UPDATE...
FOR 12Z TAFS

&&

.DISCUSSION...
/ISSUED 543 AM CDT WED JUL 30 2014/
TRANQUIL WEATHER CONDITIONS PERSIST ACROSS THE CENTRAL TENNESSEE
VALLEY THIS MORNING...WITH CURRENT TEMPERATURES NEAR OR BELOW
RECORD LOWS FOR MOST OF THE REGION. IR SATELLITE DATA CONFIRMS THAT
HIGH- LEVEL CIRROFORM CLOUDS HAVE ALREADY BEGUN TO OVERSPREAD THE
AREA FROM THE WEST...WITH THIS TREND EXPECTED TO CONTINUE AND
INCREASE THROUGH THE DAY AND INTO TONIGHT AS WINDS ALOFT BACK IN
RESPONSE TO A 500-MB SHORTWAVE TROUGH DROPPING SOUTHEASTWARD ACROSS
EASTERN COLORADO AND WESTERN KANSAS. MODELS SUGGEST THAT A WEAKER
PRECEDING WAVE WILL EJECT EAST-NORTHEASTWARD OVER THE REGION
TONIGHT...RESULTING IN CONTINUED THICKENING/LOWERING OF CIRROSTRATUS
AND PERHAPS SOME VIRGA BY TOMORROW MORNING. AT THE SURFACE...LIGHT
NORTH TO NORTHEAST FLOW WILL PREVAIL AS A SURFACE RIDGE MIGRATES
NORTHEASTWARD INTO THE CENTRAL APPALACHIANS...WITH INCREASING CLOUD
COVER RESULTING IN ONLY A MODEST INCREASE IN HIGH TEMPERATURES TODAY.
WITH OVERCAST CONDITIONS EXPECTED TONIGHT...LOWS WILL BE
SUBSTANTIALLY WARMER AND SHOULD ONLY FALL INTO THE UPPER 50S AND
LOWER 60S.

THE SOUTHERN PLAINS SHORTWAVE TROUGH IS PROGGED TO TURN EASTWARD AND
CROSS THE LOWER MISSISSIPPI VALLEY TOMORROW AFTERNOON...AND AS THIS
OCCURS ELEVATED ISENTROPIC ASCENT WILL BEGIN TO INCREASE RATHER
QUICKLY ACROSS THE LOCAL AREA. UPWARD VERTICAL MOTIONS GENERATED BY
BOTH THE ISENTROPIC PROCESSES AS WELL AS THE APPROACH OF THE MID-
LEVEL WAVE ARE STILL EXPECTED TO BE SUFFICIENT TO GENERATE A SWATH
OF LIGHT RAIN BY LATE TOMORROW AFTERNOON -- WITH HIGHEST
PROBABILITIES OF MEASURABLE PRECIP OCCURRING ACROSS THE WEST. AS THE
WAVE TRACKS ACROSS THE REGION THURSDAY NIGHT...ISENTROPIC ASCENT WILL
BE MAXIMIZED AND THIS SHOULD COINCIDE WITH A FAVORABLE INCREASE IN
PWATS TO 1.5+ INCHES TO LEAD TO A FAIRLY WIDESPREAD COVERAGE OF
LIGHT/MODERATE RAIN...ESPECIALLY OVER THE SOUTHEASTERN HALF OF THE
REGION. ALL MODELS WITH THE EXCEPTION OF THE NAM INDICATE THAT THE
WAVE WILL BE EJECTING NORTHEASTWARD INTO THE MID-ATLANTIC REGION
RATHER QUICKLY ON FRIDAY...WITH AN INCREASINGLY SUBSIDENT AIRMASS
ALOFT EXPECTED TO OVERSPREAD THE REGION FROM THE WEST. HOWEVER...THE
REMNANTS OF A WEAK INVERTED SURFACE TROUGH -- FORECAST TO SHIFT
EASTWARD ACROSS TEXAS ON THURSDAY -- MAY PROVIDE SOME LOW-LEVEL
CONVERGENCE FOR A REGENERATION OF PRECIPITATION DURING THE AFTERNOON.
GIVEN EXPECTED ORIENTATION OF BOUNDARY AND SOUTHWESTERLY STEERING
FLOW ALOFT...HAVE PLACED HIGHEST POPS IN THE EAST. MID-LEVEL LAPSE
RATES WILL STEEPEN SUFFICIENTLY FOR THE DEVELOPMENT OF THUNDERSTORMS
AND THIS WAS ALSO INCLUDED IN THE FORECAST.

ALTHOUGH THE ANCHORING CYCLONE FOR THE EASTERN NORTH AMERICA LONGWAVE
TROUGH IS EXPECTED TO WEAKEN CONSIDERABLY ON FRIDAY/FRIDAY NIGHT...
A LINGERING LONGWAVE TROUGH AXIS WILL REMAIN IN PLACE FROM THE GREAT
LAKES TO THE LOWER MISSISSIPPI VALLEY. AT THE SURFACE...THE INVERTED
TROUGH AXIS WILL LIKELY CONTINUE TO INITIATE ISOLATED TO SCATTERED
CONVECTION FROM FRIDAY NIGHT INTO SATURDAY...WITH STEERING CURRENTS
ALOFT FAVORING THE EASTERN ZONES FOR THE HIGHEST COVERAGE. CONDITIONS
WILL BECOME LESS FAVORABLE FOR SHOWERS/STORMS BEGINNING AS EARLY AS
SATURDAY EVENING...AS THE INVERTED TROUGH LOOSES DEFINITION AND A
REINFORCING SURFACE HIGH BUILDS SOUTHWARD FROM THE GREAT LAKES
LEADING TO LIGHT NORTHEAST WINDS AND ADVECTION OF DRIER AIR INTO THE
REGION /PWATS FALLING BELOW 1 IN ACROSS THE NORTH BY MONDAY/. DUE TO
LINGERING PRESENCE OF A WEAKNESS IN THE SUBTROPICAL RIDGE ALOFT...
WILL MAINTAIN A VERY LOW CHANCE OF SHOWERS/STORMS THROUGH THE END OF
THE EXTENDED PERIOD...BUT CONDITIONS ARE NOW LOOKING WARMER AND DRIER
FOR THE SECOND HALF OF THE WEEKEND AND EARLY NEXT WEEK.

70/DD

&&

.AVIATION...
FOR 12Z TAFS...CLOUDS WILL BE INCREASING TODAY AND TONIGHT ASSOCIATED
WITH A WEAK UPPER DISTURBANCE NOW OVER THE CENTRAL/SRN PLAINS. ALSO
MODEL SOUNDINGS WERE SHOWING SOME MOISTURE ARND 8H...ALONG WITH MID
70S CONVECTIVE TEMPS...FOR A SCT CU FIELD BY THE AFTN. FOR TONIGHT
EXPECT MAINLY CI CLOUDS. OTHERWISE VFR CONDITIONS ARE EXPECTED THRU
THE FCST PERIOD.

07

&&

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

$$

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



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.