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000
FXUS64 KHUN 110756
AFDHUN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HUNTSVILLE AL
256 AM CDT TUE MAR 11 2014

.DISCUSSION...
THE FORECAST FOR THE NEXT SEVERAL DAYS WILL BE THE RESULT OF A SPLIT
FLOW REGIME SHIFTING TO ZONAL, AND A SERIES OF MID-LEVEL SHORTWAVE
TROUGHS MERGING (OR NOT MERGING) TOGETHER ACROSS THE PLAINS AND GULF
COAST. THE FIRST COUPLE OF MID-LEVEL SHORTWAVES ARE LOCATED NORTH
AND SOUTH OF THE TN VALLEY. THE NORTHERN STREAM MID-LEVEL SHORTWAVE
IS MOVING ACROSS THE CENTRAL/SOUTHERN PLAINS, AND IS PUSHING A
CONTINENTAL POLAR AIR MASS AHEAD OF IT. THE SOUTHERN STREAM MID-LEVEL
SHORTWAVE IS CURRENTLY JUST OFF THE COAST OF TX MOVING NORTHEASTWARD
TOWARDS THE NORTH CENTRAL GULF COAST.

THE WARM, PLEASANT WEATHER WILL COME TO AN ABRUPT TEMPORARY HALT
TONIGHT AS THESE TWO MID-LEVEL SHORTWAVE TROUGHS MOVE ACROSS THE
SOUTHEAST. MEANWHILE, SOUTHERLY MOIST FLOW WILL PREVAIL TODAY WITH
DAYTIME HIGHS RISING INTO THE MID TO UPPER 70S UNDERNEATH INCREASING
CLOUD COVER. THE INCREASING CLOUD COVER WILL BE INITIALLY THE RESULT
OF THE SOUTHERN STREAM SHORTWAVE TROUGH MOVING NORTHWARD FROM THE
GULF COAST. AS A RESULT OF ITS TRAJECTORY, WAA AND A WEAK OMEGA
FIELD, ENOUGH LIFT IS PRESENT (ALONG WITH WEAK INSTABILITY: MUCAPE
200-400 J/KG) TO SUPPORT ISOLATED THUNDERSTORMS THIS AFTERNOON.

LATEST MODEL TRENDS INDICATE THAT THE GREATEST PROPENSITY FOR STORMS
IS OVER NE AL/S MIDDLE TN BUT WILL RETAIN ISOLATED T-STORMS FOR THE
WHOLE AREA TO ACCOUNT FOR SOME WOBBLING WITH THE APPROACHING
SHORTWAVE. ONCE THAT WAVE PASSES THE REGION THIS EVENING, THE
NORTHERN STREAM MID-LEVEL SHORTWAVE WILL CROSS THE AREA LATER TONIGHT
BRINGING MORE SHOWER ACTIVITY WITH EMBEDDED THUNDERSTORMS BETWEEN
00-09Z. THEN, THE COLD FRONT WILL PASS OVER THE AREA BTWN 12-16Z WITH
HIGHS FOR THE DAY LIKELY OCCURRING JUST BEFORE THE FRONT PASSES OVER
THE AREA. LINGERING RAIN SHOWERS AND LOW CLOUDS WILL PERSIST POST-
FROPA ALONG WITH A BREEZY (15-20 MPH) NORTHWEST WIND. DID ADJUST THE
POPS SOMEWHAT HIGHER FOR THIS EVENING, AND INTRODUCED A GRADIENT IN
POPS THROUGHOUT THE OVERNIGHT AND ON WEDNESDAY. FORECAST SOUNDINGS
ALSO INDICATE THE TEMPS ALOFT AND AT THE SFC MAY DROP BELOW FREEZING
BY WEDNESDAY AFTERNOON WITH THE POSSIBILITY OF FLURRIES. HOWEVER, AM
NOT CONFIDENT ENOUGH MOISTURE WILL BE PRESENT TO SUPPORT IT. SO, HAVE
NOT INCLUDED IN THE FORECAST YET. IN SHORT, WEDNESDAY SHOULD PRETTY
MUCH BE CHARACTERIZED AS A COLD & `RAW` DAY.

TEMPERATURES SHOULD THEN DROP PRECIPITOUSLY BELOW FREEZING WEDNESDAY
NIGHT WITH CLOUD COVER SLOWLY RECEDING AS THE TROUGH MOVES OFF TO
THE NORTHEAST. WITH THE COLD START TO THURSDAY MORNING AND LIGHT
NORTHERLY SFC FLOW, TEMPERATURES WILL LIKELY STRUGGLE TO REACH INTO
THE LOW 50S FOR DAYTIME HIGHS AS THE SFC HIGH PRESSURE SYSTEM
GRADUALLY BUILDS OVER THE SOUTHEAST. BY THURSDAY EVENING, THE SFC
HIGH IS EXPECTED TO MOVE OFF TO THE EAST WHICH WILL RESULT IN A MORE
SOUTHERLY FLOW ACROSS THE SOUTHEAST. THIS WILL TRANSLATE TO DAYTIME
HIGHS ON FRIDAY REACHING INTO THE 60S.

THE EXTENDED PART OF THE FORECAST IS WHERE THE HIGHEST UNCERTAINTY
LIES. CURRENTLY, THE GFS, ECMWF, AND CANADIAN ALL HAVE DIFFERING
SOLUTIONS ON THE MERGING (OR NOT) OF A MID-LEVEL SHORTWAVE MOVING
SOUTHEAST FROM THE PACIFIC NORTHWEST AND A CUTOFF LOW OVER THE
DESERT SOUTHWEST. AS THESE TWO (OR ONE) FEATURES MOVE ACROSS THE
PLAINS INTO THE SOUTHEAST ON FRIDAY NIGHT INTO SATURDAY, THERE IS THE
POSSIBILITY FOR STRATIFORM RAINFALL TO DEVELOP DURING THAT TIME
PERIOD. WHETHER IT IS A SHEAR ZONE/DEFORMATION AXIS THAT DROPS
ACROSS THE REGION OR THE COMBINATION OF THE TWO SHORTWAVE TROUGHS IS
THE MAIN ISSUE.

ONE CURIOUS MODEL OUTPUT SCENARIO FROM THE ECMWF (SHOWN OVER PAST
COUPLE OF RUNS) HAS THE LAST SHORTWAVE TROUGH MERGING WITH THE SHEAR
AXIS AND FORMING A CUTOFF LOW OVER THE SOUTHEAST FROM SUNDAY INTO
MONDAY. GIVEN THE BETTER PERFORMANCE WITH THE ECMWF WITH THESE CUTOFF
SCENARIOS, WILL TREND TOWARDS THAT SOLUTION. NEVERTHELESS, DUE TO
HIGH AMOUNT OF UNCERTAINTY, HAVE LEFT A 20 POP IN THE FORECAST FROM
FRIDAY NIGHT THROUGH SATURDAY WITH CHC POPS IN THE FORECAST FOR
SUNDAY AND MONDAY. DID TREND TEMPERATURES CLOSE TO SEASONAL AVERAGES
FOR THIS TIME OF YEAR, DURING THIS PART OF THE EXTENDED FORECAST WITH
SOME MINOR ADJUSTMENTS TO SKY COVER.

SL.77

&&

.AVIATION...
/ISSUED 1150 PM CDT MON MAR 10 2014/
FOR 06Z TAFS...NO CHANGES TO PREVIOUS AVIATION FORECAST REASONING.
VFR WILL BE THE PREVAILING COND AT HSV/MSL OVERNIGHT. THE LACK OF
CLOUD COVER COUPLED WITH A LGT SW FLOW MAY ALLOW FOR TEMP VSBY
REDUCTIONS IN LGT BR...MAINLY BTWN 11/09-12Z. MID/HIGH-LEVEL CLOUDS
WILL BE ON THE INCREASE BY 12Z AS AN UPPER-AIR DISTURBANCE BEGINS TO
TRACK EWD ALONG THE NW GULF COAST. AS SSWLY FLOW OF 10-15 KTS AHEAD
OF THIS APPROACHING SYSTEM TRANSPORTS MOISTURE INTO THE REGION...
EXPECT CLOUDS TO INCREASE BY LATE MORNING...WITH BKN DECK OF STRATUS
BCMG ESTABLISHED ARND 3500 FT. THREAT FOR PCPN WILL REMAIN HIGHEST TO
THE SOUTH OF BOTH TERMINALS THRU 12/00Z...BUT CHANCES FOR SHRA AND A
FEW TSRA WILL INCREASE BY 02Z.

70/DD

&&

.PRELIMINARY POINT TEMPS/POPS...
HUNTSVILLE    76  57  57  29 /  20  60  50  10
SHOALS        76  59  59  27 /  20  60  50  10
VINEMONT      73  57  57  28 /  20  70  60  10
FAYETTEVILLE  72  54  54  25 /  20  60  50  10
ALBERTVILLE   73  58  58  28 /  20  70  60  10
FORT PAYNE    73  55  55  28 /  20  70  60  10

&&

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

$$

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AT WEATHER.GOV/HUNTSVILLE.