Area Forecast Discussion
Issued by NWS Huntsville, AL

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000
FXUS64 KHUN 042333 AAA
AFDHUN

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE HUNTSVILLE AL
633 PM CDT SAT JUL 4 2015

.UPDATE...
FOR 00Z TAFS

&&

.DISCUSSION...
/ISSUED 145 PM CDT SAT JUL 4 2015/
A RATHER DIFFICULT FORECAST IN THE SHORT TERM TO SAY THE LEAST.
EARLY AFTERNOON SURFACE ANALYSIS SHOWED A CHAOTIC AND ILL DEFINED
PATTERN. ONE WEAK BOUNDARY WAS SITUATED TO OUR NORTH FROM SOUTHERN
KENTUCKY THROUGH WEST CENTRAL TENNESSEE INTO CENTRAL ARKANSAS. AN
OUTFLOW BOUNDARY WAS ORIENTED FROM NEAR ATLANTA WESTWARD THROUGH THE
I-20 CORRIDOR INTO NORTHERN LOUISIANA. THIS LATTER FEATURE HAS BEEN A
FOCUS FOR CONVECTIVE DEVELOPMENT SO FAR TODAY. IN
BETWEEN...PRECIPITATION HAS BEEN RATHER SPARSE AND LIGHT OVER THE
LAST SEVERAL HOURS WITH ANOTHER BAND OF SHOWERS LOCATED ACROSS
NORTHERN MS AND SOUTHWEST TENNESSEE ON THE CYCLONIC SIDE OF THE UPPER
TROUGH. ADDITIONAL VERY LIGHT SHRA AND ISOLD TSRA WERE ALSO
DEVELOPING ACROSS MIDDLE TENNESSEE.

MAIN QUESTION MARK FOR THIS EVENING AND OVERNIGHT REMAINS
REDEVELOPMENT ACROSS THE TENNESSEE VALLEY. TEMPERATURES HAVE WARMED
RATHER NICELY TODAY COMPARED TO YESTERDAY WITH MANY AREAS REACHING
INTO THE LOWER 80S. VIS IMAGERY SHOWS BREAKS IN THE OVERCAST FROM
SOUTHERN TN THROUGH NORTH CENTRAL/NORTHEAST ALABAMA. THE SHORT RANGE
HIGH RES MODELS HAVE REALLY STRUGGLED WITH THE MESOSCALE
FEATURES/BOUNDARIES OVER THE PAST COUPLE OF DAYS AND THEIR IMPACTS ON
THE SENSIBLE WEATHER. AS SUCH...IT HAS BECOME A NOWCASTING AND
DIAGNOSTIC TYPE OF FORECASTING CHALLENGE.

CURRENT THINKING IS THAT WE SHOULD SEE AN INCREASE IN AT LEAST
SCATTERED SHOWERS BY MID/LATE AFTN WITH SBCAPE INCREASING TO NEAR 2
KJ/KG AND SOME INCREASING ASCENT ASSOCIATED WITH THE H7-H5 LOW. THE
LOW LEVEL JET BECOMES A BIT MORE PRONOUNCED EAST OF I-65 BY THIS
EVENING AND PAINTED THE HIGHEST POPS AND QPF (RELATIVELY SPEAKING IN
THAT AREA). AFTER COORDINATION WITH SURROUNDING OFFICES WILL KEEP THE
EXISTING FLASH FLOOD WATCH GOING. WITH FFG VALUES SO LOW AND THE
POTENTIAL FOR CONVECTIVE TYPE PRECIP...SEE NO REASON TO NOT KEEP IT
GOING. IN ADDITION...PRECIPITATION MAY FILL IN SOME IN THE VICINITY
OF THE LOW OVERNIGHT.

FOR SUNDAY...KEPT RATHER HIGH POPS GOING (ESPECIALLY MIDDLE AND EAST)
AS THE LAPSE RATES SHOULD BE FAVORABLE FOR CONVECTIVE DEVELOPMENT IN
THE VICINITY OF THE UPPER TROUGH SIMILAR TO WHAT WE ARE SEEING TODAY
IN SOUTHERN ARKANSAS AND SOUTHWEST TENNESSEE. THERE ARE SOME
INDICATIONS THAT THE ACTIVITY MAY BE ON THE WANE BY AFTERNOON AS THE
UPPER LOW PULLS EASTWARD BUT GIVEN SOME MODEL DISCREPANCY I DIDN`T
GET TOO CUTE WITH THE POPS.

RATHER UNSETTLED PATTERN WILL CONTINUE WELL INTO THE EXTENDED PERIOD.
ALTHOUGH THE GUIDANCE VARIES IN SOME OF THE SYNOPTIC SCALE
DETAILS...THE GENERAL TREND OF A BROAD EASTERN CONUS TROUGH/GREAT
PLAINS RIDGE WILL BRING THE EVER PESKY NWRLY FLOW TO THE TN VLY. IN
THIS PARTICULAR PATTERN ONE CAN USUALLY BANK ON WIDELY SCATTERED TO
SCATTERED AFTN CONVECTION AND THE OCCASIONAL NOCTURNAL CONVECTIVE
COMPLEX THROWN IN FOR GOOD MEASURE. NOW GOOD LUCK TRYING TO TIME THE
LATTER WITH MUCH SUCCESS...ESPECIALLY BEYOND ABOUT 24 HOURS.
OTHERWISE...MAX TEMPS WOULD LIKELY RUN AT OR JUST A TAD BELOW CLIMO
LEVELS. ALL IN ALL...NOT MANY SIGNIFICANT CHANGES WERE MADE TO THE
PREVIOUS FORECAST AS THE AFTN BLEND OF THE GUIDANCE WAS RATHER
CONSISTENT FROM THE OVERNIGHT FLAVOR.

15

&&

.AVIATION...
FOR 00Z TAFS...BAND OF SHRA MOVING ACROSS NW AL COULD SWIPE KMSL
00-02Z...BUT IS MORE LIKELY TO AFFECT KHSV FOR A LONGER PERIOD
00-04Z. HALEYVILLE/1M4 HAS SEEN VIS DROP TO 1 3/4SM IN HVY RAIN SO
OCCASIONAL DROPS TO IFR ARE PSBL THIS EVENING...ESPECIALLY AT KHSV.
ONCE THE SHRA BAND HAS PASSED...CEILINGS WILL LOWER TO NEAR-IFR /SOME
CHANCE THEY COULD LOWER FURTHER/ AND FOG/MIST MAY DEVELOP. CONDITIONS
WILL IMPROVE AFTER DAYBREAK BUT SHOULD STAY MVFR THRU 18Z/05.

BCC

&&

.HUN WATCHES/WARNINGS/ADVISORIES...
AL...FLASH FLOOD WATCH THROUGH SUNDAY MORNING FOR ALZ001>010-016.

TN...FLASH FLOOD WATCH THROUGH SUNDAY MORNING FOR TNZ076-096-097.

&&

$$

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


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