Area Forecast Discussion
Issued by NWS Birmingham, AL

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FXUS64 KBMX 021202
AFDBMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BIRMINGHAM AL
702 AM CDT THU OCT 2 2014

.UPDATE...
FOR 12Z AVIATION.

&&

.DISCUSSION...

ANOTHER WARM DAY IS ON TAP TODAY AS AN UPPER-LEVEL RIDGE MOVES
EASTWARD ACROSS THE REGION AHEAD OF AN APPROACHING STORM SYSTEM.
HIGHS THIS AFTERNOON COULD PUSH THE 90 DEGREE MARK IN SOME
LOCATIONS. SOUTHERLY FLOW WILL CONTRIBUTE TO AN INCREASE IN
MOISTURE...MAKING FOR RATHER MUGGY CONDITIONS FOR OCTOBER
ESPECIALLY ACROSS THE WEST. THIS IS ALSO WHERE PWAT VALUES ARE
EXPECTED TO APPROACH 2 INCHES BY LATE AFTERNOON AS DEWPOINTS RISE
INTO THE LOWER 70S...WHICH COULD SPARK DIURNAL ACTIVITY IN THE
FORM OF SCATTERED SHOWERS AND STORMS. AFTER AN EVENING LULL IN
ACTIVITY...RAIN CHANCES WILL INCREASE FROM WEST TO EAST EARLY
FRIDAY MORNING IN ASSOCIATION WITH A STRONG COLD FRONT.

SEVERE THUNDERSTORMS ARE EXPECTED TO DEVELOP TO OUR WEST ACROSS
ARKANSAS AND THE LOWER MISSISSIPPI VALLEY REGION THIS AFTERNOON
AND EVENING AS A STRONG SHORTWAVE KICKS EASTWARD ACROSS THE
SOUTHERN PLAINS. THIS PRE-FRONTAL CONVECTION WILL BE KNOCKING ON
THE DOOR OF OUR NORTHWESTERN COUNTIES AROUND 4 AM. THERE IS REASON
TO BELIEVE SOME OF THESE STORMS COULD BE SEVERE...PARTICULARLY
NORTH OF I-20 AND WEST OF I-65...WHERE DECENT UPPER-LEVEL SUPPORT
IS EXPECTED. THOUGH MID-LEVEL LAPSE RATES ARE FORECAST TO BE IN
THE 5.7-6 C/KM RANGE...DEWPOINTS IN THE LOWER 70S SHOULD LEAD TO
MLCAPE OF 700-1100 J/KG AND DEEP CONVECTION. 0-6 KM SHEAR AND
UNIDIRECTIONAL 850-500 MB FLOW OF 40-50 KT MAY BE SUFFICIENT FOR
ISOLATED SEVERE WIND GUSTS ALONG A BROKEN LINE OF STORMS.
ADDITIONALLY...THE ECMWF AND GEM HAVE TRENDED MORE IMPRESSIVE
WITH A WELL-DEVELOPED LOW-LEVEL JET OF 45-50 KT EXTENDING ALONG AN
AXIS FROM THE OHIO VALLEY SOUTHWARD INTO WEST CENTRAL ALABAMA.
THOUGH WINDS IN THE 850-500 MB LAYER ARE EXPECTED TO BE
UNIDIRECTIONAL...I AM ANTICIPATING A RESPECTABLE AMOUNT OF SPEED
AND DIRECTIONAL SHEAR IN THE 0-1 KM LAYER AS SURFACE WINDS SHOULD
REMAIN BACKED AHEAD OF THE FRONT. WILL CONTINUE WITH ONLY A
MENTION OF DAMAGING WINDS IN HWO...BUT A NON-ZERO TORNADO THREAT
CANNOT BE RULED OUT...AND THIS WILL NEED TO BE RE-EVALUATED.

ANY SEVERE WEATHER THREAT SHOULD DIMINISH WITH BY NOON FRIDAY
AS UPPER-LEVEL SUPPORT QUICKLY DEPARTS TO THE NORTH...BUT A BAND
OF SHOWERS AND STORMS WILL TRAVERSE THE CWA THROUGH THE AFTERNOON
WITH HIGH RAIN CHANCES AREA-WIDE. CONDITIONS SHOULD TURN COOLER
AND DRIER INTO FRIDAY EVENING BEHIND THE FRONT.

A MASSIVE TROUGH WILL DEVELOP OVER EASTERN NORTH AMERICA OVER THE
WEEKEND AS SEVERAL SHORTWAVES COMBINE. MODEL GUIDANCE CONTINUES
TO TREND COOLER FOR SATURDAY AND SUNDAY WITH HIGHS ON SATURDAY
RANGING FROM THE MID 60S NORTH TO LOWER 70S SOUTH. BRISK NORTHWEST
WINDS WILL USHER IN MUCH DRIER AIR WITH DEWPOINTS EXPECTED TO DROP
INTO THE 30S. WINDS SHOULD DIMINISH BY SUNDAY MORNING AS SURFACE
HIGH PRESSURE MOVES IN...LEADING TO MORNING LOWS IN THE LOW TO MID
40S AREA-WIDE. MODEL DISAGREEMENT IS QUITE SIGNIFICANT BY MONDAY
REGARDING THE NEXT SHORTWAVE ROTATING AROUND THE BASE OF THE
LONGWAVE TROUGH. THIS SYSTEM COULD LEAD TO SHOWERS FOR MONDAY
NIGHT INTO TUESDAY.

87/GRANTHAM


&&

.AVIATION...
12Z TAF DISCUSSION.

IFR CIGS HAVE FORMED OVER WEST ALABAMA EARLY THIS MORNING DUE TO
INCREASING SOUTHERLY FLOW. STRONG LOW LEVEL WARMING THIS MORNING
SHOULD CAUSE THE CIGS TO RISE TO MVFR OR SCATTER BY 15Z. CUMULUS
WILL DEVELOP AT MOST TAFS SITES BY 17Z...AND SOME LOCATIONS MAY
BECOME BKN...BUT PREVAILING SKY COND WILL BE SCATTERED. A FEW SHWRS
OR TSTMS WILL LIKELY DEVELOP OVER WEST ALABAMA AFTER 18Z...BUT NOT
ENOUGH CONFIDENCE TO INCLUDE IN KTCL. SHWRS AND TSTMS WILL
INCREASE IN COVERAGE AFTER 06Z FOR AREAS NORTH OF I-59 AS A SHORT
WAVE TROF APPROACHES NW ALABAMA...AND INCLUDED VCTS IN NORTHERN
TAF SITES. LOW CLOUDS WILL LIKELY FORM AFTER 08Z ACROSS MOST OF
CENTRAL ALABAMA IN MOIST SOUTHERLY FLOW.

58/ROSE



NOTE...THE NATIONAL WEATHER SERVICE WILL BEGIN ISSUING SEASONAL
TERMINAL FORECASTS FOR THE TALLADEGA MUNICIPAL AIRPORT (KASN) IN
TALLADEGA...ALABAMA. THE FORECAST WILL BEGIN OCTOBER 5TH AT 00Z
AND LAST THROUGH AT LEAST THE 23RD OF OCTOBER.

07

&&

.PRELIMINARY POINT TEMPS/POPS...
GADSDEN     88  69  79  47  67 /  10  60  90  10   0
ANNISTON    88  70  79  48  67 /  10  50  90  10   0
BIRMINGHAM  89  72  80  47  68 /  20  70  90  10   0
TUSCALOOSA  90  72  82  50  70 /  30  80  80  10   0
CALERA      88  73  80  49  68 /  20  60  90  10   0
AUBURN      87  69  79  52  70 /  10  30  90  10   0
MONTGOMERY  89  73  82  53  72 /  10  40  90  10   0
TROY        88  72  81  54  72 /  10  30  80  10   0

&&

.BMX WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$






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