000
FXUS64 KBMX 181149
AFDBMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BIRMINGHAM AL
649 AM CDT SAT MAY 18 2013

.UPDATE...
FOR 12Z AVIATION.

&&

.DISCUSSION...

MID LEVEL SHORT WAVE STRETCHING SOUTHEASTWARD ACROSS THE TENNESSEE
RIVER VALLEY CONTINUES TO SLOWLY MOVE EASTWARD THIS MORNING. THE
FORCING ASSOCIATED WITH THIS FEATURE COMBINED WITH CONTINUED
MOISTURE TRANSPORT FROM THE SOUTHWEST AND A LOW LEVEL CONVERGENT
ZONE HAS RESULTED IN CONTINUED REDEVELOPMENT OF SHOWERS AND
THUNDERSTORMS ACROSS NORTHERN PORTIONS OF THE AREA. TRAINING OF
HEAVIER CELLS AS THEY MOVE WEST TO EAST COULD LEAD TO LOCALIZED
FLOODING THROUGH THE REMAINDER OF THE OVERNIGHT PERIOD. ACTIVITY
WILL GRADUALLY SHIFT EASTWARD THROUGH THE MORNING...WITH THE EAST
BECOMING THE FOCUS FOR CONVECTION SATURDAY AFTERNOON. WITH PWS
OVER 1.5 INCHES...HEAVY RAINFALL OVER ALREADY SOAKED AREAS COULD
LEAD TO LOCALIZED FLASH FLOODING THROUGH THE DAY. WITH TEMPS
REACHING INTO THE LOW TO MID 80S AND DEWPOINTS IN THE 60S...CAPE
VALUES WILL REACH 2000+ J/KG. WIND SHEAR VALUES ARE NOT EXPECTED
TO BE AS HIGH AS FRIDAY...LIMITING STORMS SEVERE POTENTIAL.
HOWEVER...ACTIVITY WILL LIKELY REMAIN ORGANIZED ALONG THE LOW
LEVEL CONVERGENT ZONE AS IT SHIFTS EAST AND SOUTH TODAY. SMALL HAIL
AND GUSTY WINDS WILL BE POSSIBLE WITH STRONGER STORMS. WILL CARRY
LIKELY POPS ACROSS A SIGNIFICANT PORTION OF THE AREA TODAY...BUT
WILL MAKE ADJUSTMENTS BEFORE SUNRISE BASED ON UPSTREAM TRENDS.
EXPECT POPS TO INCREASE FOR SOME PORTION OF CENTRAL ALABAMA WITH
THAT UPDATE.

MID LEVEL RIDGE AXIS MOVES ACROSS THE LOWER MISSISSIPPI RIVER VALLEY
SATURDAY NIGHT...PUSHING THE SHORT WAVE SLIGHTLY FURTHER EASTWARD.
WITH LOSS OF DAYTIME HEATING...ACTIVITY SHOULD WANE OVERNIGHT...AND
WILL CARRY HIGHEST POPS ACROSS THE NORTHEAST. A STRONG IMPULSE WILL
ROTATE THROUGH THE MID LEVEL TROUGH AXIS JUST TO OUR EAST ON SUNDAY.
MODELS ARE SHOWING AN MCS DEVELOPING ACROSS SOUTHEASTERN TN AND
DIVING SOUTHEASTWARD ACROSS GEORGIA DURING THE AFTERNOON AND
EVENING. WILL MAINTAIN LIKELY POPS ACROSS THE EAST ON SUNDAY AS
HEIGHTS CONTINUE TO INCREASE ACROSS THE WEST. WILL HAVE TO WATCH
FUTURE MODEL RUNS FOR ANY CHANGES IN THE POTENTIAL MCS TRACK...A
SHIFT FURTHER WEST WOULD RESULT IN HIGHER POPS AND SEVERE WORDING
IN THE HWO.

THE RIDGE AXIS CONTINUES TO BUILD ACROSS THE SOUTHEAST MONDAY AND
TUESDAY...LIMITING CONVECTION DESPITE CONTINUED LOW LEVEL MOIST FLOW
FROM THE SOUTHWEST. THE NEXT SYSTEM WILL AFFECT CENTRAL ALABAMA BY
MIDWEEK AS A TROUGH MOVES OUT OF THE PLAINS AND DRAGS A WEAK FRONT
THROUGH THE AREA WEDNESDAY AND THURSDAY. MODELS CURRENTLY SHOW
CONSERVATIVE INSTABILITIES AND WIND SHEAR VALUES AS THE PARENT
SURFACE LOW IS WELL TO OUR NORTH. WILL CONTINUE TO EVALUATE
THAT SYSTEM OVER THE NEXT COUPLE DAYS. THROUGH NEXT WEEK...HIGHS
WILL BE IN THE 80S AND LOWS IN THE 60S.

14


&&

.AVIATION...
12Z TAF DISCUSSION.

TOUGH FORECAST CONTINUES DUE TO ONGOING CONVECTION. ADDITIONAL
DEVELOPMENT SHOULD CONTINUE THRU MUCH OF THE DAY AND HAVE INCLUDED
SHRA VCTS AT MOST SITES FOR NOW. DUE TO LOW PREDICTABILITY WILL
JUST HAVE TO AMEND THRU THE DAY TO ACCOUNT FOR MORE PERSISTENT
TSRA. HEAVY RAIN...GUSTY WINDS...AND LIGHTNING WILL ACCOMPANY MOST
STORMS. THEREFORE VIS COULD QUICKLY BE REDUCED TO IFR OR LOWER.

CIGS SHOULD SLOWLY RISE TO VFR BY THE AFTERNOON AT ALL TERMINALS.
WINDS WILL GENERALLY BE OUT OF THE S/SW AT LESS THAN 10 KTS
OUTSIDE OF THUNDERSTORMS.

19

&&


.PRELIMINARY POINT TEMPS/POPS...
GADSDEN     80  65  84  66  90 /  60  60  60  20  10
ANNISTON    81  65  84  65  89 /  60  60  60  30  10
BIRMINGHAM  80  66  86  66  89 /  60  50  30  10  10
TUSCALOOSA  84  67  88  66  89 /  60  20  10  10  10
CALERA      81  66  86  66  89 /  60  30  20  10  10
AUBURN      82  64  85  65  88 /  60  30  50  30  10
MONTGOMERY  88  66  88  66  91 /  50  20  20  10  10
TROY        83  65  88  66  91 /  40  20  20  10  10

&&

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

&&

$$