339
FXUS64 KBMX 201121
AFDBMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BIRMINGHAM AL
621 AM CDT THU JUN 20 2013

.UPDATE...
FOR 12Z AVIATION.

&&

.DISCUSSION...

CURRENT WATER VAPOR IMAGERY INDICATES A CLOSED UPPER LOW ACROSS THE
PACIFIC NORTHWEST WITH A RIDGE ACROSS THE CENTRAL CONUS. CLOSER TO
HOME...ACROSS THE SOUTHEAST...A FEW SHORTWAVE TROUGHS CAN BE NOTED
IN THE NORTHWESTERLY FLOW ON THE EASTERN SIDE OF THE RIDGE. THESE
SUBTLE FEATURES WILL BE KEY FOR SHOWER AND THUNDERSTORM DEVELOPMENT
OVER THE COMING DAYS. AT THE SURFACE...A WEAK FRONTAL BOUNDARY IS
LOCATED JUST TO THE SOUTH OF THE CWA AND STRETCHES BACK TO THE WEST
INTO EASTERN TEXAS. LAST NIGHTS 00Z SOUNDING INDICATED A SHARP
DECREASE IN PW DOWN TO 1.17 INCHES. MOST OF THE YEAR THIS WOULD BE A
RESPECTABLE PW VALUE BUT FOR LATE JUNE THIS AROUND THE 25TH
PERCENTILE. FOR TODAY...THE HIGHEST POPS WILL BE ACROSS THE
SOUTHEAST WHERE THE LINGERING SURFACE FRONT COULD PROVIDE ADDITIONAL
LIFT TO PARCELS. AREAS SOUTH OF I-85 WILL ALSO HAVE THE HIGHEST PW
VALUES RUNNING IN THE NEIGHBORHOOD OF 1.5 INCHES. FURTHER TO THE
NORTH...COVERAGE SHOULD BE FAIRLY ISOLATED AT BEST WITH PW VALUES IN
THE 1.25 AREA. WILL HOLD ON TO THE SLIGHT CHANCE FOR AFTERNOON
SHOWERS AND THUNDERSTORMS FURTHER NORTH AS A SHORTWAVE TROUGH MOVES
THROUGH THE NORTHWESTERLY FLOW. MODEL SOUNDINGS INDICATE THAT CAPE
WILL BE RATHER SKINNY WITH WEAK FLOW ALOFT SO NO STRONG OR SEVERE
STORMS ARE ANTICIPATED. CONVECTION SHOULD BE DIURNALLY DRIVEN WITH
SOME ISOLATED SHOWER AND THUNDERSTORMS POSSIBLY LINGERING INTO THE
EVENING HOURS. WITH A FAIRLY DRY ATMOSPHERE FOR LATE JUNE AND NO REAL
SOURCE OF SURFACE LIFT REMOVED POPS DURING THE OVERNIGHT PERIOD.

MOISTURE WILL SLOWLY INCREASE LATE IN THE WEEK AND INTO THE WEEKEND.
RAIN CHANCES OF FRIDAY WILL CREEP NORTHWARD. BEST CHANCES AGAIN WILL
BE ACROSS THE SOUTHEAST DECREASING TO THE NORTHWEST. THE UPPER LEVEL
RIDGE WILL BECOME AMPLIFIED ACROSS THE EASTERN HALF OF THE CONUS. THE
MAIN CHALLENGE WITH THIS FORECAST IS ALL OF THE MODELS INDICATE A
WEAKNESS IN THE RIDGE ACROSS THE SOUTHEAST. SOME OF THE MODELS
INDICATE WHAT APPEARS TO BE A WEAK UPPER LEVEL LOW. LOW LEVEL WINDS
WILL BECOME MORE SOUTHERLY BY THE WEEKEND AS THE UPPER LEVEL RIDGE
AT LOW LEVEL AMPLIFIES ACROSS THE ATLANTIC. THESE SOUTHERLY WINDS
WILL PROVIDE A FRESH SUPPLY OF GULF MOISTURE WITH PW INCREASING TO
NEAR 2 INCHES BY THE END OF THE WEEKEND. WITH THE LACK OF ANY REAL
SURFACE FEATURE...CONVECTION SHOULD BE DIURNALLY DRIVEN WITH HIGHEST
CHANCES DURING THE AFTERNOON WITH ONLY SLIGHT CHANCE TO NO CHANCE
DURING THE OVERNIGHT HOURS. TEMPERATURES WILL RUN A COUPLE OF
DEGREES BELOW NORMAL DURING THIS PERIOD WITH INCREASED CLOUD COVER
AND PRECIPITATION. UPPER LEVEL HEIGHTS WILL INCREASE DURING THE
MIDDLE OF THE WORK WEEK BUT CONTINUED SOUTHERLY LOW LEVEL FLOW
SHOULD PROVIDE SUFFICIENT SUPPLY OF MOISTURE FOR RAIN CHANCES TO
CONTINUE. MODELS INDICATE A MORE POTENT UPPER LEVEL TROUGH WILL
ROTATE THROUGH THE RIDGE MID TO LATE NEXT WEEK BUT DIFFER SLIGHTLY
ON STRENGTH AND TIMING.

05/MA

&&

.AVIATION...
12Z TAF DISCUSSION.

LOWER VIS AND CIGS WILL LIFT BY 14Z. FRONT SHOULD BE SHIFTING
SOUTH OF THE AREA DURING THE MORNING HOURS. THIS WILL LOWER ANY
RAIN CHANCES ACROSS THE SOUTH...WITH ONLY PEAK HEATING OF THE DAY
THUNDERSTORMS FOR TOI AND MGM AFTER 20Z. CLEARING AFTER 1 TO 4Z.

16

&&

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

&&

$$