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000
FXUS64 KBMX 161459
AFDBMX

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

.UPDATE...
MORNING UPDATE.

&&

.DISCUSSION...

MESO-ANALYSIS OF SURFACE DATA THIS MORNING SHOWS A WEAK PRESSURE
GRADIENT ACROSS THE AREA WITH NO DISCERNIBLE BOUNDARIES. THERE IS A
POCKET OF DRIER LOW LEVEL AIR OVER NORTHEAST ALABAMA...BUT THIS
AREA WILL LIKELY MOISTEN UP QUICKLY UNDER SOUTHEAST SURFACE FLOW.
AN UPPER RIDGE OVER THE NORTHERN GULF OF MEXICO SHOULD HINDER
CONVECTIVE DEVELOPMENT ACROSS THE SOUTHERN COUNTIES TODAY. A WEAK
SHORT WAVE TROF MOVING EASTWARD ACROSS THE OHIO VALLEY STATES WILL
PROVIDE JUST ENOUGH LIFT FOR BETTER RAIN CHANCES ACROSS NORTH AND
WEST ALABAMA. MAIN CHANGE TO FORECAST WAS TO KNOCK DOWN RAIN
CHANCES ACROSS THE SOUTHEAST COUNTIES TO 2O PERCENT.

58/ROSE


&&

.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


&&

.PREV DISCUSSION...
/ISSUED 641 AM CDT SUN JUN 16 2013/
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

&&

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

&&

$$