000
FXUS64 KBMX 151120
AFDBMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BIRMINGHAM AL
620 AM CDT SAT JUN 15 2013

.UPDATE...
FOR 12Z AVIATION.

&&

.SYNOPSIS...

A SURFACE COLD FRONT HAS PUSHED WELL SOUTH OF THE AREA AS DRY AIR
HAS SETTLED IN. PRECIPITABLE WATER VALUES HAVE DROPPED DOWN INTO
THE 50-60 PERCENT OF NORMAL RANGE FOR MID JUNE. MEAN RELATIVE
HUMIDITY VALUES START INCREASING RATHER QUICKLY AND RAIN CHANCES
ARE RE-INTRODUCED INTO THE FORECAST SUNDAY THROUGH TUESDAY. A
COLD FRONT APPROACHES THE REGION ON MONDAY AND TUESDAY WITH
SEVERAL UPPER LEVEL DISTURBANCES MOVING OVERHEAD. THIS PERIOD WILL
REMAIN THE MOST ACTIVE AND WILL KEEP THE HIGHEST RAIN CHANCES
HERE. WE ARE ENTERING THE TIME OF YEAR WHERE FRONTS HAVE AN
INCREASINGLY TOUGH TIME PUSHING ENTIRELY THROUGH THE STATE. THIS
NEXT FRONT WILL MOST LIKELY HANG UP NEAR THE SOUTHERN CWA...AND
MAY ONLY PROVIDE A BRIEF REPRIEVE FROM RAIN CHANCES. BUT POPS WILL
NOT BE COMPLETELY REMOVED FROM THE FORECAST BEYOND TUESDAY DUE TO
MODEL DIFFERENCES IN HANDLING THE MEAN MOISTURE. THE BEST BET IS
THAT THERE REMAINS ENOUGH MOISTURE FOR AT LEAST DIURNALLY ENHANCED
ACTIVITY THE REMAINDER OF THE PERIOD.

OVERALL FORECAST REASONING AND MAIN FEATURES/SENSIBLE WEATHER
REMAIN VERY CLOSE TO THE PREVIOUS FORECAST.

75

&&

.DISCUSSION...

AN UPPER RIDGE AND NORTHWEST FLOW ALOFT START OFF THE PERIOD BUT
THE SYNOPTIC PATTERN FLATTENS OUT SIGNIFICANTLY THROUGH MONDAY.
THIS ALLOWS SEVERAL RIPPLES IN THE WESTERLY FLOW TO PENETRATE
SOUTHWARD. MOISTURE WILL INCREASE AND A COLD FRONT WILL APPROACH
THE AREA BY MONDAY AND TUESDAY. THIS PERIOD APPEARS TO BE THE MOST
UNSETTLED DURING THE FORECAST TIME FRAME AND WILL CONTINUE THIS
ADVERTISED TREND. THE VARIOUS MODEL SOLUTIONS ARE IN RELATIVELY
GOOD AGREEMENT THROUGH TUESDAY AND THEN SOME DIFFERENCES START
SHOWING UP. THE GFS APPEARS TO BE THE OUTLIER IN MOVING A SLIGHTLY
DEEPER TROUGH EASTWARD FASTER AND THEREFORE ALLOWING A COLD FRONT
TO PUSH THROUGH ALL OF CENTRAL ALABAMA. THE OTHER MODELS ARE NOT
NEARLY AS AMBITIOUS...INCLUDING THE ENSEMBLES. THE CONSENSUS KEEPS
THE STALLED BOUNDARY ACROSS CENTRAL ALABAMA IN A WEAKENED STATE.
BY SATURDAY...THE MODELS ARE COMPLETELY OUT OF PHASE.

WARM AND SOMEWHAT DRY CONDITIONS ON TAP FOR YOUR SATURDAY. MEAN
MOISTURE VALUES INCREASE ENOUGH TO MENTION POPS ON SUNDAY AND
SUNDAY NIGHT. UPWARD MOTION AND FORCING INCREASE AS THE MAIN UPPER
TROUGH AND COLD FRONT APPROACH MONDAY AND TUESDAY. WILL KEEP POPS
FAIRLY HIGH THIS ENTIRE PERIOD. SLIGHTLY LOWER POPS WEDNESDAY AND
MORE FOCUSED NEAR THE WEAKENING FRONT SOUTH. THEREAFTER...WILL
SWITCH TO A MORE DIURNALLY ENHANCED RAIN CHANCE. IF THE LEFTOVER
BOUNDARY ACTS AS MORE OF A FOCUS THAN ANTICIPATED...POPS MAY BE A
BIT HIGHER THURSDAY AND FRIDAY. CONFIDENCE WAINS BY SATURDAY AND
SUNDAY AS THE MODELS GO OUT OF PHASE AND WILL KEEP NEAR
CLIMATOLOGICAL POPS.

MODERATE INSTABILITY WILL DEVELOP BOTH MONDAY AND TUESDAY. BULK
SHEAR VALUES ARE NOT IMPRESSIVE AND UPPER LEVEL TEMPERATURES ARE
RATHER WARM. BUT THERE WILL BE AN UPPER LEVEL DISTURBANCE AND
A COLD FRONT TO AIDE IN LIFT AND FORCING. ALSO...SB CAPE VALUES
FORECAST IN THE 2000-2500 RANGE WITH DOWNDRAFT CAPE 800-1000 AT
TIMES. AT THIS TIME...BELIEVE A FEW STRONG STORMS WILL BE
POSSIBLE MONDAY AND TUESDAY WITH SOME GUSTY WINDS AND BRIEF HEAVY
RAIN.

75

&&

.AVIATION...
12Z TAF DISCUSSION.

VFR CONDITIONS EXPECTED AT ALL SITES FOR THE NEXT 24 HOURS WITH
LIGHT EAST TO SOUTHEAST WINDS. SCATTERED CLOUDS ARE POSSIBLE
AROUND 5000 FEET MAINLY DURING THE AFTERNOON.

87/GRANTHAM

&&

.PRELIMINARY POINT TEMPS/POPS...
GADSDEN     87  65  88  69  86 /   0   0  20  20  70
ANNISTON    88  67  88  71  86 /   0   0  20  20  60
BIRMINGHAM  90  71  90  74  88 /   0   0  20  20  70
TUSCALOOSA  91  72  92  73  90 /   0   0  20  20  70
CALERA      89  69  90  73  87 /   0   0  20  20  60
AUBURN      87  68  87  72  87 /   0   0  20  20  50
MONTGOMERY  93  71  93  73  91 /   0   0  20  20  40
TROY        92  70  92  72  91 /   0   0  20  20  30

&&

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

&&

$$

75/87