FXUS64 KBMX 060006
AFDBMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BIRMINGHAM AL
606 PM CST SAT DEC 5 2009

.UPDATE...AVIATION DISCUSSION.

&&

.DISCUSSION...

WITH THE EXIT TO THE EAST OF THE SNOWY WEATHER SYSTEM...WE NOW
CONCENTRATE ON (FIRST) THE COLD CONDITIONS TONIGHT AND (LATER) ON
THE POTENTIAL FOR SEVERE THUNDERSTORMS TUESDAY-WEDNESDAY.

WITH CLEAR SKIES...A COLD DRY AIR MASS...AND WINDS BECOMING
LIGHT...TEMPERATURES WILL HAVE AMPLE OPPORTUNITY TO DROP BELOW
FREEZING ACROSS THE ENTIRE FORECAST AREA. CONDITIONS WILL REMAIN
RELATIVELY BENIGN THROUGH SUNDAY AFTERNOON.

THE UPPER LEVEL FLOW BECOMES ZONAL AND RATHER ACTIVE EARLY NEXT
WEEK...AS SEVERAL SHORTWAVE TROUGHS MOVE THROUGH. THE MAIN
SHORTWAVE OF NOTE SCOOTS JUST TO OUR NORTH IN THE TUESDAY-
WEDNESDAY TIME FRAME...AND BRINGS OUR NEXT BOUT OF ACTIVE WEATHER.
A WEAKER WAVE PRECEDES THE MAIN ONE SUNDAY NIGHT AND MONDAY...AND
HELPS TO START OPENING UP THE GULF. CLOUDS SHOULD START TO SPREAD
BACK IN TOMORROW AFTERNOON...LEADING TO A CHANCE OF SHOWERS
OVERNIGHT TOMORROW NIGHT INTO MONDAY. THERE'S A BRIEF BREAK MONDAY
NIGHT...BUT THEN THE MOISTURE RETURN REALLY GETS INTO FULL GEAR AS
THE MAIN SHORTWAVE AND ASSOCIATED SURFACE SYSTEM APPROACHES AND
GATHERS STRENGTH ON TUESDAY. MODELS ARE INSISTENT ON LIKELY TO
CATEGORICAL POPS FOR TUESDAY AND TUESDAY NIGHT...AND IT IS HARD TO
GO AGAINST THAT.

LOOKING AT THE TIMING OF THE VARIOUS LOW LEVEL FEATURES AND OTHER
SEVERE WEATHER PARAMETERS...IT LOOKS LIKE RIGHT NOW THERE IS AT
LEAST A SMALL POSSIBILITY OF SEVERE STORMS TUESDAY NIGHT...AND WE
HAVE TWEAKED THE HAZARDOUS WEATHER OUTLOOK TO INDICATE SUCH. THIS
LOOKS LIKE A SOMEWHAT TYPICAL CASE OF HIGH SHEAR...LOW INSTABILITY...
AND A QUESTION OF WHETHER OR NOT LOW LEVEL MOISTURE WILL BE
SUFFICIENT FOR INTENSE CONVECTION. ONE DISCONCERTING FACTOR IS THE
NEWLY ARRIVED 18Z RUN OF THE NAM...WHICH HAS THE STRENGTHENING
SURFACE LOW AND COLD FRONT STILL PRETTY FAR BACK TO THE WEST AT
06Z WEDNESDAY. GIVEN THIS...IT WOULD NOT SURPRISE ME IF THE MODELS
ARE CURRENTLY TOO QUICK IN MOVING THINGS EASTWARD (AS IS OFTEN THE
CASE)...AND OUR DAY OF STRONG/SEVERE STORMS ENDS UP GETTING PUSHED
BACK TO WEDNESDAY. THIS WOULD...IN TURN...GIVE THE LOW LEVELS A
BIT MORE TIME TO MOISTEN UP AND ADD TO THE INSTABILITY. WE'LL
WATCH HOW LATER MODELS GO.

ONCE THAT SYSTEM GETS PAST US (LATE WEDNESDAY OR WEDNESDAY
NIGHT)...CONDITIONS SHOULD RETURN TO BEING DRY THROUGH AT LEAST
FRIDAY WHEN THE NEXT UPPER LEVEL SHORTWAVE TROUGH APPROACHES.

/61/

&&

.AVIATION...00Z TAF DISCUSSION.

NO AVIATION PROBLEMS ARE EXPECTED OVER THE NEXT 24 HOURS.

&&

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

&&

$$