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000
FXUS64 KBMX 142135
AFDBMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BIRMINGHAM AL
435 PM CDT TUE MAY 14 2013

.UPDATE...

FOR AMENDED NOTE IN AVIATION FOR KEET.

&&

.DISCUSSION...

THIS AFTERNOON THE SENSIBLE WEATHER ACROSS THE SOUTHEAST WAS BEING
DOMINATED BY AN EXPANSIVE AREA OF HIGH PRESSURE AT THE SURFACE
CENTERED OVER LOUISIANA... SOUTHERN MISSISSIPPI AND ALABAMA...  AND
GEORGIA. ALOFT AN AREA OF SUBSIDENCE IN THE FORM AN APPROACHING
UPPER RIDGE WAS SUPPRESSING CLOUD DEVELOPMENT ACROSS MOST OF THE
REGION. OVER NORTHWESTERN MEXICO A CLOSED UPPER LOW WAS NEARLY
STATIONARY PER LATEST WATER VAPOR SATELLITE IMAGERY.

OVERALL... NOT MANY CHANGES NEEDED TO THE FORECAST PACKAGE. THE UPPER
RIDGE NOTED ABOVE WILL BECOME CENTERED OVER THE SOUTHEAST
TOMORROW... WHICH WILL HELP WARM TEMPERATURES A DEGREE OR TWO ABOVE
HIGH TEMPS FOR TODAY. BY THURSDAY THE CLOSED LOW MENTIONED ABOVE
WILL HAVE EJECTED FROM THE SOUTHWEST CONUS... AND WILL BE ADVANCING
AS A SHORTWAVE TROUGH OVER THE SOUTHEAST. WITH SOME LOW LEVEL
MOISTURE IN PLACE COMBINED WITH THE WEAK SHORTWAVE TROUGH...
ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS APPEAR POSSIBLE
THURSDAY AND FRIDAY. BUT WITH THE LACK OF AN OBVIOUS LOW LEVEL
FORCING MECHANISM... HAVE MAINTAINED ONLY 20-30 PERCENT POPS FOR
THIS TIME FRAME. FOR TEMPS THURSDAY AND FRIDAY HAVE KEPT THEM LOWER
THEN MOS GUIDANCE DUE TO THE EXPECTED CLOUD COVER AND PRECIP.

THIS WEEKEND THE 12Z GFS KEEPS CENTRAL ALABAMA PRETTY MUCH DRY
WITH ANOTHER SHORTWAVE RIDGE MOVING OVER THE REGION. BUT THE 12Z
ECMWF SHOWS SOME LIGHT PRECIP IN THE AREA FOR BOTH SATURDAY AND
SUNDAY. THIS APPEARS TO BE DUE A SLIGHT DIFFERENCE IN HOW EACH
MODEL HANDLES A SUBTLE WEAKNESS (SHORTWAVE TROUGH/VORTICITY
MAXIMUM) THAT IS FORECAST TO ROUND THE TOP OF THE RIDGE THAT WILL
BE OVER US. THE GFS KEEPS THIS FEATURE A BIT FURTHER NORTH THAN
THE ECMWF... AND DUE TO THE UNCERTAINTY WITH THE LOCATION OF THIS
FEATURE 4-5 DAYS OUT AND FOR THE SAKE OF CONTINUITY WITH THE
PREVIOUS FORECAST... WILL NOT MENTION ANY POPS FOR THIS WEEKEND.
BUT IF THE ECMWF IS CORRECT... THEN SOME SLIGHT CHANCE TO CHANCE
POPS MAY BE NEEDED BOTH SATURDAY AND SUNDAY AFTERNOON. REGARDLESS
OF WHICH SOLUTION VERIFIES... TEMPS FOR THIS WEEKEND LOOK WARM...
GENERALLY IN THE MID TO UPPER 80S.

NEAR THE END OF THE CURRENT FORECAST PERIOD... NEXT MONDAY AND
TUESDAY... A LONGWAVE TROUGH WILL BE ADVANCING OUT OF THE GREAT
PLAINS AND INTO THE OHIO VALLEY. THERE ARE SOME LARGE DISCREPANCIES
BETWEEN THE GFS AND ECMWF IN THE HANDLING OF THE SYNOPTIC SCALE
FEATURES FOR THIS SYSTEM THIS FAR OUT... BUT IT DOES APPEAR THAT A
COLD FRONT WILL BE APPROACHING THE REGION FROM THE NORTHWEST
SOMETIME AROUND NEXT TUESDAY AFTERNOON/EVENING.

77/GLEASON

&&

.AVIATION...
18Z TAF DISCUSSION.

SFC HIGH PRESSURE WILL KEEP CONDITIONS VFR THRU THE PERIOD. CLEAR
SKIES AND SW WINDS WILL BE THE NORM. WINDS OF AROUND 10 KTS WILL
BECOME LIGHT/CALM OVERNIGHT.

NOTE: THERE APPEARS TO BE A VISIBILITY ISSUE WITH KEET THIS
AFTERNOON. WILL INCLUDED AMD LTD TO CLD...WIND AND WX THROUGH
0515/18Z. SHOULD BE RESOLVED BY THAT TIME AS THE EQUIPMENT IS STILL
WORKING.

19

&&

.PRELIMINARY POINT TEMPS/POPS...
GADSDEN     51  83  57  80  57 /   0   0  10  30  20
ANNISTON    55  83  60  82  59 /   0   0  10  30  20
BIRMINGHAM  60  83  63  81  62 /   0   0  10  30  20
TUSCALOOSA  57  85  62  83  62 /   0   0  10  30  20
CALERA      57  83  61  81  61 /   0   0  10  30  20
AUBURN      58  84  65  81  63 /   0   0  10  20  20
MONTGOMERY  57  86  62  84  62 /   0   0  10  20  20
TROY        52  85  59  83  61 /   0   0  10  20  20

&&

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

&&

$$

77/19