Area Forecast Discussion
Issued by NWS Huntsville, AL

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000
FXUS64 KHUN 162021
AFDHUN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HUNTSVILLE AL
321 PM CDT WED APR 16 2014

.DISCUSSION...
A BROAD CYCLONIC FLOW REGIME ALOFT PREVAILS ACROSS THE CONUS THIS
AFTERNOON...WITH THE AXIS OF LOWEST HEIGHTS GENERALLY ALIGNED FROM
THE NORTHERN PLAINS SOUTHWESTWARD INTO THE SOUTHERN ROCKIES. ACROSS
THE LOCAL FORECAST AREA...MID/UPPER-TROPOSPHERIC WINDS REMAIN FROM
THE SOUTHWEST AND THIS COMBINED WITH CLEAR SKIES AND A VERY DRY
AIRMASS HAVE ALLOWED TEMPERATURES TO REBOUND INTO THE UPPER 50S/LOWER
60S. INSPECTION OF IR SATELLITE DATA INDICATES THAT AN INCREASE IN
CIRROFORM CLOUD COVER CAN BE EXPECTED ACROSS THE REGION THIS
EVENING...AS A WEAK 500-MB SHEAR AXIS -- CURRENTLY APPROACHING THE
LOWER MISSISSIPPI VALLEY -- LIFTS NORTHEASTWARD. THIS WILL LIKELY
EASE ANY CONCERNS FOR FROST FORMATION...ESPECIALLY WITH STRENGTHENING
EAST-SOUTHEAST FLOW BETWEEN A SURFACE RIDGE WEDGED IN THE LEE OF THE
SOUTHERN APPALACHIANS AND WEAK CYCLONE MOVING ACROSS THE UPPER
MISSISSIPPI VALLEY EXPECTED TO MAINTAIN A WELL-MIXED BOUNDARY LAYER.

SHORT TERM MODELS ARE IN GOOD AGREEMENT REGARDING A STRONGER MID-
LEVEL VORTICITY MAXIMA WHICH IS PROGGED TO EMERGE ACROSS THE
OKLAHOMA/TEXAS PANHANDLE REGION BY 12Z THURSDAY AND SHIFT EASTWARD
ACROSS THE CENTRAL PLAINS THROUGH THE REMAINDER OF THE DAY. DRY
CONDITIONS ARE EXPECTED ACROSS THE CENTRAL TENNESSEE VALLEY IN THE
SUBSIDENT AIRMASS DOWNSTREAM FROM THIS FEATURE...WITH HIGH
TEMPERATURES REACHING INTO THE UPPER 60S. BY THURSDAY NIGHT...THE
CENTRAL PLAINS VORT MAX IS EXPECTED TO BECOME STRETCHED...WITH THE
SOUTHERN END OF THE TROUGH FORECAST TO GRADUALLY BECOME DETACHED AND
BEGIN PHASING WITH ANOTHER MID-LEVEL TROUGH OVER THE NORTHERN GULF OF
MEXICO. ANALYSIS OF ISENTROPIC PROGS FROM THE GFS/ECMWF/NAM/UKMET
SUGGEST THAT A WEAK WARM FRONTAL STRUCTURE WILL BEGIN TO LIFT
NORTHWARD ACROSS MISSISSIPPI/ALABAMA AS A PARTIALLY MODIFIED MARITIME
AIRMASS BEGINS TO ADVECT NORTHWARD IN ADVANCE OF THE APPROACHING
TROUGH. STRENGTHENING SOUTHERLY FLOW WILL LIKELY YIELD AN INCREASE IN
ISENTROPIC ASCENT ALONG THE 300-310K SURFACES -- ESPECIALLY BETWEEN
06-12Z FRIDAY -- WITH THE THREAT FOR LIGHT RAIN LIKEWISE INCREASING
FROM WEST-TO-EAST ACROSS THE FORECAST AREA. THE PRIMARY CONCERN
REGARDING THE COVERAGE OF SHOWER ACTIVITY AT THIS TIME IS THE
POTENTIAL FOR LINGERING IMPACTS FROM THE DRY ARCTIC AIRMASS CURRENTLY
IN PLACE ACROSS THE EASTERN SEABOARD. HOWEVER...SUFFICIENT CONFIDENCE
EXISTS TO INCLUDE A LOW CHANCE POP DURING THIS PERIOD. ALL MODEL
GUIDANCE IS IN AGREEMENT THAT UVM GENERATED BY ISENTROPIC ASCENT WILL
DIMINISH DURING THE MORNING HOURS AS A STRONGER MID-LEVEL CUTOFF LOW
EVOLVES ALONG THE CENTRAL GULF COAST AND LOW/MID-LEVEL FLOW FIELDS
BECOME LESS FAVORABLE FOR ASCENT. HOWEVER...WILL MAINTAIN A LOW
CHANCE POP FOR LIGHT RAIN DURING THE MORNING HOURS BEFORE
PRECIPITATION BECOMES MORE CONSOLIDATED TO THE SOUTHEAST OF THE AREA
DURING THE AFTERNOON. THE CUTOFF CYCLONE IS FORECAST TO DEEPEN AND
TRACK EASTWARD ACROSS THE FAR NORTHEAST GULF OF MEXICO/FLORIDA
PANHANDLE REGION FRIDAY NIGHT...WITH PERIPHERAL SUBSIDENCE ALOFT AND
INCREASING NORTHEAST FLOW/ADVECTION OF DRIER AIR AT THE SURFACE
MAINTAINING DRY BUT CLOUDY CONDITIONS.

DRY AND SEASONABLY WARM CONDITIONS ARE EXPECTED TO PERSIST ON
SATURDAY/SUNDAY...AS THE REGION WILL REMAIN BENEATH A MID-LEVEL
RIDGE LOCATED BETWEEN THE CUTOFF LOW TRACKING EASTWARD INTO THE
WESTERN ATLANTIC AND AN UPSTREAM TROUGH LIFTING EAST-NORTHEASTWARD
INTO THE CENTRAL PLAINS. SIMILAR TO THE PREVIOUS TROUGH...THIS
FEATURE IS ALSO EXPECTED TO SPLIT INTO TWO DISTINCT VORTICITY
LOBES...WITH SOUTHWEST FLOW ALOFT AND INCREASING DEEP-LAYER FORCING
FOR ASCENT EXPECTED BY SUNDAY AFTERNOON/EVENING AS THE INITIAL
DISTURBANCE APPROACHES. A MORE SUBSTANTIAL INCREASE IN LARGE SCALE
ASCENT IS ANTICIPATED ON MONDAY AFTERNOON/MONDAY NIGHT...AND --
DEPENDENT ON THE SPEED OF THE SYSTEM -- PERHAPS TUESDAY AS THE SECOND
WAVE DIGS SOUTHEASTWARD ACROSS THE LOWER MISSISSIPPI VALLEY
ACCOMPANIED BY A WEAK SURFACE CYCLONE. FORECAST SOUNDINGS INDICATE
SUFFICIENT INSTABILITY FOR THE DEVELOPMENT OF CONVECTION AND WILL
CONTINUE TO MENTION THUNDERSTORMS DURING THIS PERIOD. IN THE WAKE OF
THIS SYSTEM...ANOTHER MID-LEVEL SHORTWAVE RIDGE WILL BUILD IN ACROSS
THE SOUTHEASTERN U.S. WITH DRY CONDITIONS EXPECTED TUESDAY NIGHT AND
WEDNESDAY.

70/DD

&&

.AVIATION...
/ISSUED 1205 PM CDT WED APR 16 2014/
FOR 18Z TAFS...VFR CONDITIONS WILL PREVAIL AT KHSV AND KMSL THROUGH
THE TAF PERIOD. SOUTHEASTERLY WINDS WILL PERSIST THROUGH TONIGHT
AND INCREASE THURSDAY MORNING UP TO 12-14 KTS.

JMS

&&

.PRELIMINARY POINT TEMPS/POPS...
HUNTSVILLE    41  69  49  67 /   0  10  20  30
SHOALS        40  69  50  69 /   0  10  30  30
VINEMONT      40  68  48  66 /   0  10  20  30
FAYETTEVILLE  38  68  47  65 /   0  10  20  20
ALBERTVILLE   40  67  48  64 /   0  10  20  20
FORT PAYNE    37  67  46  65 /   0  10  20  20

&&

.HUN WATCHES/WARNINGS/ADVISORIES...

AL...NONE.

TN...NONE.

&&

$$

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



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