000
FXUS64 KBMX 161141
AFDBMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BIRMINGHAM AL
641 AM CDT SUN JUN 16 2013

.UPDATE...
FOR 12Z AVIATION.

&&

.SYNOPSIS...
A WEAK WARM FRONT MOVES NORTHWARD TODAY AND GRADUALLY DISSIPATES.
BOUNDARY LAYER WINDS WILL SHIFT FROM SOUTHEAST TOWARD A SOUTH
SOUTHWEST DIRECTION ALLOWING SURFACE DEW POINTS TO INCREASE. AN
OUTFLOW BOUNDARY FROM PREVIOUS CONVECTION WILL APPROACH FROM THE
NORTHWEST TODAY BUT THE MAIN FRONT WILL REMAIN NORTH OF THE AREA.
MOISTURE AHEAD OF THE OUTFLOW WILL INCREASE THE MEAN MOISTURE FOR
NORTHERN COUNTIES. A SHORT WAVE TROUGH ALSO TRAVERSES THE AREA
THIS AFTERNOON. THEREFORE...THERE IS A CHANCE OF CONVECTION TODAY
MAINLY DURING THE MAXIMUM HEATING OF THE DAY.

IT APPEARS THAT THE ADVERTISED UNSETTLED WEATHER WILL REMAIN A
GOOD BET MONDAY THROUGH WEDNESDAY. A FEW BOUTS OF SHOWERS AND
THUNDERSTORMS WILL OCCUR ASSOCIATED WITH SEVERAL UPPER LEVEL WAVES
AND AN APPROACHING COLD FRONT. THE FRONT SHOULD SLOWLY SAG
SOUTHWARD BY WEDNESDAY AFTERNOON...LIMITING CONVECTION SOUTHWARD
BY THEN.

A SHIFT TO MORE CLIMATOLOGICAL AND DIURNAL CONVECTION THURSDAY
THROUGH SUNDAY.

&&

.SHORT TERM...
TODAY THROUGH WEDNESDAY...

INCREASED SHOWER AND THUNDERSTORM PROBABILITIES TODAY INTO THE
CHANCE RANGE (25-30). SHORT WAVE ENERGY DEPICTED NEAR EASTERN
TEXAS THIS MORNING WILL MOVE EASTWARD AND PROVIDE SOME INCREASE
IN WINDS ALOFT AND UPWARD MOTION/LIFT. BULK SHEAR VALUES CLIMB BUT
ONLY INTO THE 25-35 KT RANGE. THIS WILL COMBINE WITH INCREASING
MEAN MOISTURE LEVELS AS WARM FRONT/SOUTHERLY FLOW INCREASES. EVEN
WITH PRECIP WATER VALUES JUMPING BACK TO 1.70+...K INDICES DO NOT
JUMP OVER 30. THEREFORE...THINK THE COVERAGE WILL BE LIMITED. CAN
NOT RULE OUT A STRONG STORM OR TWO DUE TO THE INSTABILITY...SLIGHT
INCREASE IN WINDS ALOFT...MDPI/WINDEX VALUES...AND DRY AIR IN THE
MID LEVELS... WITH GUSTY WINDS THE THREAT. OF NOTE HERE...THE NAM
IS A BIT MORE AMBITIOUS WITH INSTABILITY AND MOISTURE THIS
AFTERNOON.

A FEW MORE SHORT WAVE TROUGHS EMBEDDED WITHIN THE UPPER LEVEL FLOW
WILL TRAVERSE THE REGION AS A TROUGH APPROACHES. THIS SETS THE
STAGE FOR A FEW ROUNDS OF SHOWERS AND THUNDERSTORMS MONDAY INTO
EARLY WEDNESDAY. THE MODELS HAVE BEEN IN FAIR AGREEMENT WITH THE
THERMODYNAMIC ENVIRONMENT BUT HAVE HAD SOME TIMING ISSUES. THE GFS
IS THE FASTEST WITH BRINGING A TEMPORARY DRYING INTO CENTRAL
ALABAMA...FOLLOWED BY THE NAM AND CMC...WITH THE SLOWEST BEING THE
ECMWF/HPC. WILL LEAN TOWARD THE MIDDLE GROUND OF THE NAM/CMC WHICH
IS CLOSER TO THE GFS THAN THE ECMWF. THE ECMWF KEEPS THE FRONT AS
A CONVECTIVE FOCUS THROUGH THURSDAY BEFORE A SHORT BREAK. THE GFS
HAS BEEN TOO FAST WITH SYSTEMS LATELY WHILE THE NAM HAS BEEN
SLOW...SO THE ECMWF SEEMS WAY TOO SLOW IN THIS FORECAST PERIOD.
THERE WILL ALSO BE MESOSCALE EFFECTS THAT WILL PLAY A ROLE IN THE
OVERALL EVOLUTION OF THE EFFECTIVE FOCUSING MECHANISMS.

.LONG TERM...
THURSDAY THROUGH SUNDAY...

IT APPEARS THAT THE VARIOUS MODEL OUTPUT IS IN A BIT MORE
AGREEMENT TODAY WITH THE OVERALL SYNOPTIC PATTERN...BUT
DIFFERENCES STILL APPEAR IN THE SENSIBLE WEATHER DEPARTMENT. MEAN
RELATIVE HUMIDITY VALUES VARY BETWEEN MODEL AND DAY TO DAY.
ADDITIONALLY...THE POSITION OF ANY LEFTOVER SURFACE BOUNDARIES
WILL PLAY A ROLE IN FOCUSING CONVECTION. IT ALSO APPEARS WE WILL
BE IN THE PATH OF ANY MCS THAT CAN DEVELOP UPSTREAM AS WE WILL
REMAIN UNDER A WEAKNESS IN THE UPPER RIDGE THROUGH THE PERIOD.

WITH ALL THIS BEING SAID...WILL LEAN TOWARD A MORE
CLIMATOLOGICAL/DIURNALLY ENHANCED POP FORECAST AT THIS TIME. IF
AND WHEN ANY PARTICULAR FEATURE CAN BE PIN POINTED WITH ANY
ACCURACY... SOME ADJUSTMENTS IN THE POP TIMING MAY BECOME
NECESSARY.

75

&&

.AVIATION...
12Z TAF DISCUSSION.

BRIEF OR INTERMITTENT MVFR CIGS ARE POSSIBLE THIS MORNING AT KMGM
AND KTOI. OTHERWISE PREVAILING VFR CONDITIONS ARE EXPECTED AT ALL
SITES WITH LIGHT SOUTHERLY WINDS. A FEW SHOWERS AND THUNDERSTORMS
COULD IMPACT THE TAF SITES DURING THE AFTERNOON BUT CONFIDENCE IS
LOW IN TIMING AND PLACEMENT OF SUCH ACTIVITY.

87/GRANTHAM

&&

.PRELIMINARY POINT TEMPS/POPS...
GADSDEN     89  68  86  71  84 /  30  40  60  70  70
ANNISTON    88  71  87  72  85 /  30  30  60  50  70
BIRMINGHAM  88  73  88  74  85 /  30  30  60  50  70
TUSCALOOSA  92  73  90  74  86 /  30  30  60  50  70
CALERA      89  72  87  73  85 /  30  30  60  50  70
AUBURN      88  71  86  72  84 /  30  20  50  40  50
MONTGOMERY  92  74  90  74  88 /  30  20  50  40  50
TROY        91  70  90  74  90 /  30  20  40  30  50

&&

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

&&

$$

75/87