000
FXUS64 KHUN 132040
AFDHUN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HUNTSVILLE AL
340 PM CDT THU JUN 13 2013

.SYNOPSIS...

SEVERE THUNDERSTORM WATCH NUMBER 307 IS CURRENTLY IN EFFECT FOR THE
ENTIRE HUNTSVILLE FORECAST AREA THROUGH 7PM CDT. A COLD FRONT
CURRENTLY STRETCHES FROM NORTHEASTERN TENNESSEE SOUTHWEST THROUGH
NASHVILLE AND INTO THE MEMPHIS AREA. VERY HOT AND HUMID CONDITIONS
ARE IN PLACE ALONG AND AHEAD OF THIS BOUNDARY /ESPECIALLY IN
NORTHERN ALABAMA/ WHERE TEMPS ARE BETWEEN 90 AND 94 DEGREES WITH
DEWPOINTS BETWEEN 72 AND 75 DEGREES. THIS IS PUSHING HEAT INDEX
VALUES THIS AFTERNOON INTO THE UPPER 90S TO AROUND 100 DEGREES. THIS
IS DUE TO LOW LEVEL MOISTURE CONVERGENCE MAXIMIZING AHEAD OF THE
FRONT OVER THIS AREA. THE DECATUR AIRPORT CURRENTLY IS EXPERIENCING
A HEAT INDEX OF 102 DEGREES.

THIS LOW LEVEL MOISTURE COMBINED WITH INTENSE DAYTIME HEATING HAS
LEAD TO A VERY UNSTABLE ATMOSPHERE THIS AFTERNOON. LOW LEVEL LAPSE
RATES BETWEEN 7 AND 8.0 DEGREES CELSIUS...SURFACE CAPE VALUES BETWEEN
3000 AND 4000 J/KG...AND SURFACE BASED LI`S BETWEEN -5 AND -8 ARE
DEPICTED BY SPC MESOANALYSIS. BASED ON 16Z REDSTONE ARSENAL SOUNDING
DATA RECEIVED...THIS LINES UP PRETTY WELL...WITH DCAPE VALUES IN THE
SOUNDING OF 1360 J/KG. THE FREEZING LEVEL FROM THE REDSTONE SOUNDING
IS BETWEEN 12,000 AND 14,000 FEET. MODELS DO PROG THIS TO GO DOWN TO
AROUND 11,000 FEET ALONG AND JUST AHEAD OF THE ACTUAL FRONTAL
BOUNDARY.

SCATTERED STRONG STORMS HAVE ALREADY DEVELOPED ALONG AND SOUTH OF
THIS FRONTAL BOUNDARY IN NORTHERN ALABAMA AND SOUTHERN MIDDLE
TENNESSEE. THIS ACTIVITY WILL CONTINUED AND IS EXPECTED TO INTENSIFY
THROUGH THE REMAINDER OF THE AFTERNOON. SOME OF THESE STORMS COULD BE
SEVERE AS THIS FRONT PUSHES SOUTHEAST INTO CENTRAL ALABAMA TOWARDS
THE EARLY EVENING HOURS. THE MAIN THREATS WITH ANY SEVERE STORMS WILL
BE DAMAGING WINDS AND TO A LESSER EXTENT /SINCE FREEZING IS NOT
OPTIMAL...DESPITE ROBUST INSTABILITY/ LARGE HAIL.

&&

.SHORT TERM...(TONIGHT THROUGH SATURDAY)
BASED ON CURRENT RADAR TRENDS...THE FRONTAL BOUNDARY SHOULD PUSH
INTO NORTHERN CULLMAN COUNTY JUST AFTER 6 PM CDT. MODELS PROG THE
FRONT TO THEN BE SOUTH OF THE AREA IN THE EARLY EVENING HOURS. SO
LEFT A SLIGHT CHANCE OF SHOWERS AND STORMS IN THE FORECAST THROUGH
THE EVENING HOURS. THOUGH WE EXPECT THE FRONT TO BE SOUTH OF CULLMAN
COUNTY BY AROUND 8 OR 9 PM CDT...AND THE STORM ACTIVITY WITH IT.

DRIER AND COOLER AIR WILL PUSH INTO THE REGION BEHIND THE COLD FRONT
STARTING TONIGHT. COLD AIR ADVECTION AND DRIER AIR SHOULD ALLOW
OVERNIGHT LOWS TO DROP TO BETWEEN 60 AND 65 DEGREES...A NICE CHANGE
FROM THE RECENT STRING OF 69 TO 78 DEGREES LOW TEMPERATURES SINCE
TUESDAY. 850 MB TEMPERATURES REALLY DROP ON FRIDAY TO BETWEEN 13 AND
15 DEGREES CELSIUS. THIS SHOULD TRANSLATE INTO A MUCH MORE ENJOYABLE
DAY...WITH TEMPERATURES IN THE MID 80S IN MOST LOCATIONS. EVEN COOLER
MORE PLEASANT CONDITIONS WILL BE POSSIBLE IN SOUTHERN MIDDLE
TENNESSEE...WHICH COULD ONLY SEE HIGH TEMPERATURES TOP OUT IN THE
LOWER 80S.

MODELS THEN BUILD THE UPPER RIDGE BACK TOWARD THE EAST A BIT FRIDAY
NIGHT INTO SATURDAY. THIS SHOULD START TO WARM THINGS UP AGAIN...BUT
NOT SURE HOW QUICKLY LOCATIONS EAST OF INTERSTATE 65 WILL WARM UP.
NAM12 IS MUCH COOLER IN THESE AREAS WITH 850 MB TEMPERATURES BETWEEN
15 AND 17 DEGREES CELSIUS...WHILE GFS40 850 MB TEMPERATURES ARE
BETWEEN 17 AND 18 DEGREES CELSIUS. LEANING TOWARD THE NAM12 AT THIS
POINT BASED ON COLD AIR ALOFT ANALYZED AT 850 MB IN 12Z ANALYSIS.
THEREFORE REFLECTED THIS IN GRIDS WITH COOLER TEMPERATURES THAN
GUIDANCE BOTH DAYS. THIS ALSO LINES UP WELL WITH THE ECMWF AS WELL.

.LONG TERM...(SATURDAY NIGHT THROUGH WEDNESDAY)
TEMPERATURES SHOULD GET BACK TO NORMAL JUST IN TIME FOR THE END OF
THE WEEKEND WITH HIGHS CLIMBING BACK INTO THE UPPER 80S TO LOWER 90S.

A MORE UNSETTLED PATTERN RETURNS TO THE TENNESSEE VALLEY SUNDAY NIGHT
INTO EARLY NEXT WEEK...AS THE RIDGE WEAKENS IN RESPONSE TO A FRONTAL
BOUNDARY PUSHING INTO THE OHIO VALLEY. KEPT ISOLATED TO SCATTERED
SHOWERS AND STORMS IN THE FORECAST SUNDAY THROUGH WEDNESDAY. MODELS
ARE IN BIT MORE DISAGREEMENT ON HOW QUICKLY THE FINAL FRONT PUSHES
SOUTHEAST OF THE FORECAST AREA TUESDAY THOUGH WEDNESDAY. FOR NOW
WENT WITH A BLEND OF THE GFS40 AND ECMWF...CLOSE TO PREVIOUS FORECAST
PACKAGE. MODEL SOUNDINGS DO INDICATE THAT SOME STORMS COULD BE
STRONG MONDAY NIGHT INTO TUESDAY...PRODUCING GUSTY WINDS AND HEAVY
DOWNPOURS...FAIRLY FAR INTO THE FORECAST AT THIS TIME.

KTW

&&

.AVIATION...
/ISSUED 1220 PM CDT THU JUN 13 2013/
FOR 18Z TAFS...VFR CONDS WILL BE PREDOMINANT THRU THE PERIOD. GUSTY
W WINDS (20-25KT GUSTS FROM 250-300 DEG) WILL PERSIST AHEAD OF THE
ARRIVAL OF A COLD FRONT LATER THIS AFTN. THE FRONT WILL BRING A SCT
ROUND OF TSRA TO THE REGION BTWN 18-00Z...AND A SHIFT TO NW WINDS
WILL FOLLOW BEHIND. ANY TSRA THAT DIRECTLY IMPACT THE TERMINALS COULD
DROP CIGS INTO MVFR/ALT REQ...BUT QUESTIONS ABOUT COVERAGE OF TSRA
AND THEREFORE TIMING OF THESE DROPS AT THE TERMINALS PRECLUDES
INCLUSION IN THE TAFS ATTM. GUSTS AND CLOUD COVER WILL LINGER FOR
SEVERAL HRS AFTER THE FRONT PASSES...WITH WINDS SLACKENING AND
SHIFTING MORE TO THE N OVERNIGHT AND THRU THE END OF THE TAF PERIOD.

CCC

&&

.PRELIMINARY POINT TEMPS/POPS...
HUNTSVILLE    65  87  62  86 /  10   0   0   0
SHOALS        64  88  61  90 /  10   0   0   0
VINEMONT      64  87  63  85 /  20   0   0   0
FAYETTEVILLE  62  84  61  84 /  10   0   0   0
ALBERTVILLE   63  85  58  82 /  20   0   0   0
FORT PAYNE    62  86  58  84 /  20   0   0   0

&&

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

$$

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AT WEATHER.GOV/HUNTSVILLE.