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000
FXUS64 KMOB 181935
AFDMOB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOBILE AL
235 PM CDT SAT MAY 18 2013

.SHORT TERM (TONIGHT AND SUNDAY)...BIGGEST QUESTION FOR THE FIRST
TWO PERIODS OF THE FORECAST IS POPS/WX. AS A SHORTWAVE CONTINUES TO
MOVE SE OVER THE SOUTHEASTERN CONUS...ALONG THE EAST SIDE OF AN
UPPER RIDGE STRETCHING NORTH ALONG THE MISS RIVER VALLEY...MORE
CURRENTLY OVER THE SOUTHERN PLAINS MOVES NE INTO THE RIDGE. MODEL
TIMING IS PRETTY CONSISTENT IN THIS ENERGY MOVING OVER THE LOWER
MISS RIVER VALLEY SUNDAY AFTERNOON/EVENING. JUST LOOKING AT
THIS...AM TEMPTED TO PUT IN POPS HIGHER THAN GUIDANCE IS
ADVERTISING. ON THE OTHER HAND...LOOKING AT MODEL SOUNDINGS OVER THE
WESTERN HALF OF THE FA...THERE IS A NOSE OF WARM AIR EVENT AT AROUND
5K`/850MB. CONSENSUS IS THAT THIS NOSE IS TOO MUCH FOR DAYTIME
HEATING TO OVERCOME (THOUGH NAM IS MORE BORDERLINE)...SO AM LIMITING
POPS FOR SUNDAY. FEEL THERE WILL BE A SHRA/TSRA OR TWO OVER WESTERN
SECTIONS OF THE FA...BUT NOT ENOUGH COVERAGE TO WARRANT A POP. MORE
LIKE THE CURRENT LOTTERY ODDS...THE VERY GREAT MAJORITY OF THE ARE
WILL BE RAIN-FREE.

FOR TONIGHT...WITH THE CONTINUED SOUTHERLY FLOW OFF OF THE
GULF...GUIDANCE IS ADVERTISING A HIGH CHANCE OF A STRATUS/DENSE FOG
EVENT TONIGHT. NOT QUITE HIGH ENOUGH TO GO WITH A DENSE FOG
ADVISORY...BUT PUT IN PATCHY DENSE FOG INTO THE FORECAST AFTER
MIDNIGHT TONIGHT. /16

FOR SUNDAY NIGHT THROUGH TUESDAY NIGHT...A SMALL SHORTWAVE TROF OVER
THE COASTAL WATERS AT 00Z MONDAY MOVES SLOWLY OFF TO THE EAST SUNDAY
EVENING EVENTUALLY LEADING TO AN UPPER TROF OVER THE FLORIDA
PENINSULA BY MONDAY NIGHT.  THE FORECAST AREA OTHERWISE REMAINS
UNDER THE INFLUENCE OF UPPER RIDGING OVER THE REGION THROUGH TUESDAY
WHILE A LONGWAVE TROF MOVES SLOWLY ACROSS THE PLAINS...THEN THE
RIDGING WEAKENS TUESDAY NIGHT AS THE PLAINS TROF BEGINS TO TAKE ON A
NEGATIVE TILT.

WITH A SURFACE RIDGE REMAINING NEAR THE COAST...AN ONSHORE FLOW
CONTINUES THROUGH TUESDAY NIGHT.  SEASONABLE DAYTIME HIGHS OVER THE
COASTAL COUNTIES AND ABOUT FIVE DEGREES ABOVE NORMAL FURTHER INLAND
WILL LEAD TO SEA BREEZE DEVELOPMENT EACH AFTERNOON.  DESPITE THE
PASSAGE OF THE SMALL COASTAL SHORTWAVE SUNDAY EVENING...MODEL
SOUNDINGS INDICATE THAT RIDGING OVER THE AREA IS DOMINANT RESULTING
IN A DRY FORECAST SUNDAY NIGHT.  DRY CONDITIONS CONTINUE THROUGH
TUESDAY AS MODEL SOUNDINGS CONTINUE TO INDICATE CONDITIONS NOT
CONDUCIVE TO CONVECTION DUE TO RIDGING DESPITE THE AFTERNOON SEA
BREEZE.  AS NOTED BY THE PREVIOUS SHIFT...CANNOT RULE OUT AN
ISOLATED AFTERNOON THUNDERSTORM BUT COVERAGE WILL BE TOO LOW TO
SUPPORT MENTION OF PRECIP AT THIS TIME.

WITH THE UPPER RIDGE WEAKENING TUESDAY NIGHT...CONDITIONS BECOME
MORE FAVORABLE FOR CONVECTIVE DEVELOPMENT MAINLY OVER THE FAR
NORTHWESTERN PORTION OF THE AREA.  HOWEVER...WITH THE LACK OF
IDENTIFIED FORCING MECHANISMS...WILL CONTINUE WITH A DRY FORECAST.
WITH SURFACE DEWPOINTS NEAR THE UPPER SIXTIES CLOSE TO THE COAST AND
MID SIXTIES FURTHER INLAND...LIGHT WINDS AT NIGHT WILL BE CONDUCIVE
FOR LOW CLOUDS AND FOG TO FORM ALTHOUGH CIRRIFORM CLOUDINESS MAY
LIMIT DEVELOPMENT...ESPECIALLY TUESDAY NIGHT PER MODEL SOUNDINGS.
FOR NOW WILL ADD MENTION OF PATCHY DENSE FOG TO THE LATE NIGHT HOURS
OF SUNDAY NIGHT AND MONDAY NIGHT ALONG WITH INCREASED CLOUDINESS FOR
EXPECTED LOW CLOUD DEVELOPMENT. /29

&&

.LONG TERM (WEDNESDAY THROUGH SATURDAY)...THE UPPER RIDGING OVER THE
REGION BREAKS DOWN ON WEDNESDAY AS THE PLAINS LONGWAVE TROF FURTHER
TAKES ON A NEGATIVE TILT.  AFTER THIS POINT...THERE IS FAIRLY
SIGNIFICANT DIVERGENCE BETWEEN THE GFS AND ECMWF.  HPC HAS PREFERRED
A BLEND OF THE GFS/ECMWF ENSEMBLE MEANS WHICH APPEARS TO CONTINUE
THE PLAINS UPPER TROF SLOWLY EASTWARD EVENTUALLY REACHING THE EAST
COAST ON SATURDAY.  THE SURFACE FEATURES ARE LESS UNCERTAIN...BUT
EXPECT A SURFACE RIDGE TO REMAIN OVER THE NORTHERN GULF COAST UNTIL
A WEAK FRONT MOVES THROUGH THE AREA THURSDAY NIGHT.

CONDITIONS CONTINUE TO BECOME MORE FAVORABLE FOR CONVECTIVE
DEVELOPMENT ON WEDNESDAY...MAINLY WEST OF THE I-65 CORRIDOR WHERE
LINGERING EFFECTS OF RIDGING ARE LEAST.  FOLLOWING UPON THE BLENDED
APPROACH...A SHORTWAVE MOVING THROUGH THE BASE OF THE APPROACHING
LONGWAVE TROF WILL PRODUCE AT LEAST MODEST DEEP LAYER LIFT OVER THE
FORECAST AREA ON WEDNESDAY.  A SEA BREEZE IS ALSO EXPECTED TO
DEVELOP DURING THE AFTERNOON AND CONSIDERING THE ABOVE
FACTORS...WILL CONTINUE WITH CHANCE POPS WEST OF THE I-65 CORRIDOR
AND SLIGHT CHANCE POPS EAST OF THIS AREA.  SLIGHT CHANCE POPS FOLLOW
FOR WEDNESDAY NIGHT FOR LINGERING CONVECTION.

POPS FOR THURSDAY ARE MORE UNCERTAIN GIVEN THE OVERALL UNCERTAINTY
IN THE PATTERN.  ANOTHER SHORTWAVE MAY MOVE ACROSS THE AREA ALTHOUGH
STRENGTH OF THE FEATURE IS UNCERTAIN.  DAYTIME TEMPERATURES ARE
EXPECTED TO BE SLIGHTLY ABOVE SEASONABLE VALUES OVER THE COASTAL
COUNTIES AND SEVERAL DEGREES ABOVE NORMAL FURTHER INLAND...CONDUCIVE
FOR ANOTHER SEA BREEZE.  DEEP LAYER MOISTURE SHOULD HAVE INCREASED
FURTHER AS WELL AND THE SYNOPTIC PATTERN LOOKS MORE CONDUCIVE FOR
CONVECTION COMPARED TO WEDNESDAY.  SO...CONSIDERING THIS WILL
CONTINUE WITH CHANCE POPS FOR THURSDAY.

POPS FOR THURSDAY NIGHT ARE PROBLEMATIC GIVEN THE POTENTIAL FOR THE
WEAK FRONTAL BOUNDARY MOVING THROUGH THE AREA.  THE ENSEMBLE MEAN
500 MB TROF WILL PASS ACROSS THE AREA THURSDAY NIGHT WITH A POTENTIAL FOR
DRIER DEEP LAYER AIR MOVING INTO THE AREA...SUGGESTING LESS
POTENTIAL FOR CONVECTION ALONG THE WEAK FRONTAL BOUNDARY WHICH MAY
MOVE THROUGH THE AREA.  CONSIDERING THIS AND THAT OPERATIONAL
GFS/ECMWF POPS ARE FAIRLY LOW AND ENSEMBLE ECMWF POPS ARE LOW AS
WELL...WILL CONTINUE WITH A DRY FORECAST THURSDAY NIGHT.

A NORTHERLY FLOW CONTINUES OVER THE AREA IN THE WAKE OF THE FRONT
THROUGH SATURDAY AS THE ENSEMBLE BLEND HAS A LARGE SURFACE RIDGE
BUILDING INTO THE PLAINS THEN BEGINNING TO BUILD INTO THE EASTERN
STATES.  CURRENT PACKAGE HAS SLIGHT CHANCE POPS FOR FRIDAY AND WITH
SUPPORT FROM OPERATIONAL GUIDANCE AND ECMWF ENSEMBLE GUIDANCE...MAY
SEE SOME CONVECTIVE DEVELOPMENT FROM A SHORTWAVE MOVING THROUGH THE
BACK SIDE OF THE UPPER TROF.  TEMPERATURES ON FRIDAY AND SATURDAY
WILL BE NEAR OR SLIGHTLY ABOVE SEASONABLE VALUES. /29

&&

.AVIATION (18Z ISSUANCE)...VFR CIGS/VISBYS ACROSS THE FA EXPECTED TO
CONTINUE INTO THE EVENING HOURS. GUIDANCE IS ADVERTISING A STRATUS
DECK MOVING INLAND OVERNIGHT TONIGHT...AFTER 06Z...WITH CIGS/VISBYS
DROPPING INTO IFR LEVELS. SOME LOCAL DROPS TO LIFR
LEVELS...ESPECIALLY NEAR KMOB...ARE LIKELY. WITH DAYTIME
HEATING...CIGS/VISBYS EXPECTED TO RISE QUICKLY. /16

&&

.MARINE...A SURFACE RIDGE STRETCHING WEST OVER THE NORTHERN GULF OF
MEX WILL KEEP A LIGHT TO AT TIMES MODERATE ONSHORE FLOW OVER THE
AREA THROUGH THE FORECAST. /16

&&

.FIRE...A MOIST SOUTHERLY FLOW WILL CONTINUE ACROSS THE REGION
THROUGH EARLY NEXT WEEK.  AFTERNOON RELATIVE HUMIDITIES WILL REMAIN
ABOVE CRITICAL LEVELS THROUGH AT LEAST TUESDAY.  ISOLATED TO
SCATTERED SHOWERS AND THUNDERSTORMS ARE POSSIBLE DURING THE
REMAINDER OF THE AFTERNOON WITH A FEW SHOWERS AND STORMS LINGERING
OVERNIGHT.  DRY CONDITIONS ARE OTHERWISE EXPECTED THROUGH TUESDAY.

FOG POTENTIAL AND OTHER REMARKS...PATCHY DENSE FOG IS EXPECTED TO
DEVELOP LATE EACH NIGHT THROUGH MONDAY NIGHT.  VISIBILITIES IN THE
FOG WILL BE AS LOW AS A QUARTER MILE. /29

&&

.PRELIMINARY POINT TEMPS/POPS...
MOBILE      67  84  68  86  68 /  05  10  05  05  05
PENSACOLA   70  83  70  85  70 /  05  10  05  05  05
DESTIN      70  81  71  83  70 /  05  10  05  05  05
EVERGREEN   64  88  66  91  65 /  20  10  05  05  05
WAYNESBORO  63  87  67  90  66 /  10  10  05  05  05
CAMDEN      61  89  66  91  65 /  20  10  05  05  05
CRESTVIEW   63  89  65  91  64 /  10  10  05  05  05

&&

.MOB WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
FL...NONE.
MS...NONE.
GM...NONE.
&&

$$