National Weather Service Weather Forecast Office

Area Forecast Discussion

546
FXUS64 KBMX 212001
AFDBMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BIRMINGHAM AL
301 PM CDT TUE MAY 21 2013

.DISCUSSION...

TRICKY FORECAST FOR THE 24 TO 48 HOURS AS A SLOWLY MOVING COLD FRONT
WILL SLIDE THROUGH THE AREA BY THURSDAY EVENING. TAKING A LOOK AT
ALL THE OPERATIONAL MODELS...IT APPEARS THAT MOST OF THE
PRECIPITATION SHOULD HOLD OFF UNTIL AFTER 7 AM WEDNESDAY MORNING AS
THE RIDGE REMAINS IN PLACE. NOW THE RIDGE WILL BE SLIDING EAST
THROUGH THE NIGHT. RIGHT NOW BASED ON SAT...THE RIDGE IS OVER MOST
OF MS AND MOST OF ALABAMA. ON THE OUTER EDGE OF THE RIDGE...YOU CAN
SEE THE RING OF FIRE WITH ISOLATED THUNDERSTORMS DEVELOPING. GIVEN
THE PROXIMITY OF THE SHOWERS AND STORMS...WENT AHEAD AND ADDED IN
ISOLATED THUNDERSTORMS ACROSS THE NORTH AND FAR EAST.

NOW AS WE PROGRESS THROUGH THE EVENING...WE WILL LIKELY SEE THE BULK
OF THE THUNDERSTORM ACTIVITY CURRENTLY ONGOING IN MS CONTINUE TO
SLIDE NE AND NOT IMPACT THE AREA. AS THE FRONT SLIDES FURTHER EAST
AND THE RIDGE SLIDES EAST...THERE IS ONE MODEL...THE HRRR...THAT
DEVELOPS A MCS IN ARKANSAS AND THEN SLIDES IT EAST THROUGH CENTRAL
MS AND WORKS INTO THE WEST BY 2 OR 3 AM. HAVE ENOUGH CONFIDENCE TO
INCREASE POPS IN THE WEST TO AT LEAST CHANCE WITH THE FRONT SLIDING
EAST. NOW THE QUESTION IS TO WHAT EXTENT IS THE SEVERITY THREAT
TONIGHT. AS STATED EARLIER THE MAJORITY OF THE MODELS ARE KEEPING
THE PRECIPITATION WEST OF THE AREA...WITH THE EXCEPTION TO THE RULE
BEING THE HRRR. WITH THE 16Z RUN...THE HRRR STILL BRINGS THE MCS
INTO THE AREA BUT WEAKENS IT QUICKLY AS IT WORKS INTO THE AREA RIGHT
AT 6Z. NAM AND GFS CORFIDI VECTORS SUPPORT THE EASTWARD MOTION
THROUGH MS AND THEN A SHIFT TO THE SOUTHEAST. THIS WOULD TAKE THE
COLD POOL TO THE SOUTH AS THE MOISTURE WORKS INTO THE RIDGE.
CONCEPTUAL MODELS AGREE THAT IT SHOULD BEGIN TO WEAKEN AND TAKE THE
PATH OF LEAST RESISTANCE.

AS WE MOVE INTO WEDNESDAY THE FRONT WILL CONTINUE TO SLIDE THROUGH.
CLOUD COVER AND RAIN SHOULD KEEP THE WEST MORE STABLE AND KEEP
TEMPERATURES IN THE 70S FOR THE DAY. THE MAIN DYNAMICS WILL LIFT
NORTHEASTWARD AND THE LARGER THREAT FOR SEVERE WEATHER WILL BE THE
TENNESSEE VALLEY AND PARTS NORTH. WE WILL HAVE THE POTENTIAL FOR
STRONG STORMS ACROSS THE EAST AND NORTHEAST...ESPECIALLY IF WE DO
REALIZE THE UPPER 80S TO LOW 90S BEING FORECAST. WOULD EXPECT
ANYTHING SEVERE IN THE EAST TO BE EXTREMELY ISOLATED AND WILL
CONTINUE TO LEAVE OUT OF THE HWO AS WELL. THE MAIN FRONT WILL CLEAR
OVERNIGHT WITH A SECONDARY PUSH ON THURSDAY. MODELS ARE DIFFERENT ON
WHERE THE BEST CHANCES FOR THURSDAY WILL BE...SO JUST WENT LOW
CHANCE POPS FOR THE FORECAST. BY THURSDAY NIGHT THIS SECONDARY FRONT
WILL BE SOUTH AND EAST OF THE AREA...GIVING US A DRY FORECAST FOR
THE WEEKEND AND INTO THE FIRST OF NEXT WEEK.

16

&&

.AVIATION...
18Z TAF DISCUSSION.

VFR CONDITIONS THROUGH THE EVENING WITH SOME PATCHY MVFR VIS
POSSIBLE. SOME BKN VFR CEILINGS ALSO EXPECTED TO MOVE INTO THE
AREA TOMORROW AHEAD OF THE NEXT SYSTEM WHICH ARRIVES AFTER 18Z
WEDNESDAY.

88


&&

.PRELIMINARY POINT TEMPS/POPS...
GADSDEN     66  82  63  84  59 /  10  60  40  30  20
ANNISTON    67  85  64  85  60 /  10  50  40  30  20
BIRMINGHAM  68  84  64  85  60 /  10  60  30  30  20
TUSCALOOSA  67  81  63  86  61 /  20  60  30  30  20
CALERA      66  85  65  85  60 /  10  50  40  30  20
AUBURN      67  90  66  85  63 /  10  30  40  30  20
MONTGOMERY  67  90  67  87  65 /  10  30  40  30  20
TROY        67  89  67  86  65 /  10  30  40  30  20

&&

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

&&

$$