FXUS64 KMOB 061158
AFDMOB
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOBILE AL
558 AM CST SUN DEC 6 2009
.SHORT TERM...(TODAY AND TONIGHT)...A HIGH CLOUD DECK HAS MOVED IN
UNEXPECTEDLY WHICH CAUSED THE TEMPERATURES ACROSS THE AREA TO BE
NEARLY STEADY THIS MORNING. WITH TEMPERATURES WELL ABOVE THE UPPER
20S AT MOST LOCATIONS IN THE INTERIOR...NOT EXPECTING THEM TO REACH
HARD FREEZE CRITERIA FOR TEMPERATURE NOR DURATION. THEREFORE...HAVE
DECIDED TO CANCEL THE HARD FREEZE WARNING FOR THE INTERIOR ZONES.
THE FREEZE WARNING REMAINS IN EFFECT UNTIL 8 AM FOR THE COASTAL
AREAS SINCE MANY LOCATIONS ARE AROUND FREEZING.
TEMPERATURE AND MOISTURE BEGIN TO INCREASE TODAY AHEAD OF THE NEXT
SYSTEM. HAVE GONE A FEW DEGREES ABOVE GUIDANCE FOR HIGHS TODAY AND
FOR THE OVERNIGHT LOWS TONIGHT. MOISTURE WILL BE ON THE INCREASE
TODAY AND TONIGHT, SO INCREASED POPS OVER THE WESTERN AREAS LATE
TONIGHT MAINLY AFTER MIDNIGHT.
/04
.SHORT TERM [MONDAY THROUGH WEDNESDAY]....A HIGH OVER THE SOUTHEAST
STATES MIGRATES EAST AND A DEEP LOW OVER THE PLAINS WILL MOVE EAST
BRINGING A COLD FRONT TO NEAR THE LOWER MISSISSIPPI VALLEY WITHIN 60
TO 72 HOURS. AN OPEN SURFACE WAVE WILL DEVELOP ALONG THE FRONT WHERE
IT INTERSECTS THE COAST. AS THE PARENT CYCLONE MOVES EAST ACROSS THE
GREAT LAKES MONDAY...THE FRONT WILL STALL ALONG THE GULF COAST AS THE
SURFACE AVE DEVELOP S A CLOSED CIRCULATION AND MOVES ALONG THE COAST.
RAIN CHANCES WILL ELEVATE AS THE SURFACE WAVE APPROACHES AND MOVES
THROUGH THE AREA. POPS WILL INCREASE FIRST IN THE WESTERN PART OF THE
FORECAST AREA TO LIKELY OVER THE WESTERN PORTION AND CHANCE
ELSEWHERE. ANOTHER OPEN WAVE WILL DEVELOP AND DEEPEN MONDAY NIGHT
OVER THE NORTHWESTERN GULF COAST IN RESPONSE TO MORE SHORTWAVE ENERGY
EJECTING FROM AN ACTIVE POSITIVELY TILTED UPPER TROUGH NEAR THE WEST
COAST FIRING VIGOROUS VORTICITY MAXIMA AT THE NORTHWEST GULF. TIMING
DIFFICULT AS THE FEATURE MOVES ALONG THE OLD FRONT ON THE GULF COAST
BUT IT DOES SUPPORTS CHANCE POPS ACROSS THE WESTERN HALF OF THE
REGION LATE MONDAY AND SLIGHT CHANCE ELSEWHERE. MEANWHILE THE A
DEEPENING SYSTEM OVER THE CENTRAL PLAINS WILL HAVE MOVED TO THE MID
MISSISSIPPI VALLEY OVERNIGHT TUESDAY AND BRINGING A STRONG COLD FRONT
THROUGH THE AREA.
WE WILL SEE A DEEPENING DISTURBANCE IN THE SUBTROPICAL JET STREAM OVER
THE FORECAST AREA TUESDAY AFTERNOON INTO TUESDAY NIGHT AHEAD OF THE
APPROACHING FRONT. TRANSPORT OF WATER VAPOR AHEAD OF SURFACE LOW AND
COLD FRONT MITIGATED BY WEAK LAPSE RATES. AFTERNOON WARM SECTOR
MARGINALLY UNSTABLE. DYNAMIC FORCING FOR CONVECTION TO REMAIN N OF
REGION IN CONJUNCTION WITH MIDLEVEL TROUGH, BUT LOW-LEVEL ADVECTION
OF MOIST STATIC ENERGY COULD CONTRIBUTE TO AN INCREASE IN
SURFACE-BASED CONVECTION TUESDAY WITHIN AN EXPANDING, WEAKLY CAPPED
WARM SECTOR. FORECAST HODOGRAPHS VEERING WITH HEIGHT AND SHOWING A
NAUTILUS SHAPE INDICATE A WIND PROFILE SUPPORTIVE OF SUPERCELLS AND
BOWING STRUCTURES. THERE IS A MEASURABLE RISK OF SEVERE STORMS LATE
TUESDAY BUT THERE ARE A FEW TIMING ISSUES WITH PHASING FEATURES NOT
INCLUDING THE SURFACE LOW POSITION AMONG THE MODELS. MOST MODEL
CALCULATIONS SUPPORT PRECIP ACROSS THE REGION DURING THAT PERIOD SO
LIKELY POPS RETAINED FOR TUESDAY AND TUESDAY NIGHT WITH INCREASED
CONFIDENCE IN THE NUMBERS. THERE IS ALSO LITTLE DIFFERENCE SHOWN
AMONG THE UK, ECMWF, NAM AND GFS THROUGH 72 HOURS ON 500 MB FEATURES
AND 48 HOURS ON SURFACE FEATURES.
AFTER TAU 72, THE GFS AND ECMWF 500 MB GEOPOTENTIAL HEIGHTS SHOW A
SMALL DIFFERENCE WHEN THE EURO DEVELOPS A WAVE OVER THE ROCKIES
UNDERGOING UNSTABLE GROWTH FOR 12 HOURS AT TAU 134, THEN DAMPENING,
THEN GROWING AGAIN AT TAU 216. GFS STAYS ZONAL, MORE OR LESS.
/77
.LONG TERM [WEDNESDAY NIGHT THROUGH SATURDAY]...
MINOR CHANGES DONE TO THE EXTENDED FORECAST LIMITED TO MOS CHANGES
AT 00Z. CONVECTION ASSOCIATED WITH THE LEADING SHORTWAVE SYSTEM
EXITS THE FORECAST AREA AND THE COLD FRONT MOVES THROUGH THE AREA
LEAVING DRY CONDITIONS BEHIND IT. THE WEST COAST TROUGH WILL FILL
BUT WILL CONTINUE FIRING VORTICITY PACKETS DOWNSTREAM. ANOTHER
SURFACE LOW WILL DEEPEN OVER THE SOUTHERN PLAINS OR POSSIBLY ALONG
THE TEXAS COAST FRIDAY. THAT WILL MOVE EAST BRINGING RETURN FLOW AND
CHANCE POPS. THIS WILL CONTINUE THROUGH SATURDAY.
/77
&&
.MARINE...HIGH PRESSURE WILL MOVE EAST TODAY. A LIGHT TO MODERATE
NORTHEAST TO EASTERLY FLOW IS EXPECTED ACROSS THE MARINE AREA TODAY
AND TONIGHT. A SOUTHEAST TO SOUTHERLY FLOW WILL DEVELOP BY MONDAY AS
A SERIES OF SYSTEMS APPROACHES THE AREA. A STRONG COLD FRONT WILL
MOVE THROUGH THE COASTAL WATERS ON WEDNESDAY.
/04
&&
.AVIATION (12Z ISSUANCE)...VFR CONDITIONS EXPECTED FOR THE NEXT 24
HOURS. HIGH CIRRUS DECK WILL REMAIN OVER ALL TERMINALS TODAY.
CEILINGS SHOULD BEGIN TO LOWER LATER TODAY AS A MIDDLE DECK OF
CLOUDS MOVES IN AHEAD OF THE NEXT AREA OF LOW PRESSURE.
/04
&&
.FIRE WEATHER...HIGH MOVES OFF TO THE EAST TODAY AS A LOW MOVES IN
FROM THE SOUTHERN PLAINS. RETURN FLOW WILL BRING A REBOUND TO RH
THROUGH MONDAY WITH RAIN CHANCES INCREASING AS THAT LOW APPROACHES.
RELATIVE HUMIDITY WILL APPROACH RED FLAG CRITERIA OVER THE INTERIOR
PORTION OF THE NORTHWEST FLORIDA PANHANDLE TODAY BUT WILL NOT SATISFY
DURATION REQUIREMENTS. RH WILL STAY ABOVE THE 40S AND 50S THROUGH
FRIDAY.
&&
.PRELIMINARY POINT TEMPS/POPS...
MOBILE 55 44 65 56 / 10 20 30 40
PENSACOLA 54 45 67 57 / 10 10 20 30
DESTIN 55 46 67 57 / 10 10 10 20
EVERGREEN 54 40 61 47 / 10 10 30 30
WAYNESBORO 54 41 58 50 / 10 30 50 50
CAMDEN 53 38 58 46 / 10 10 50 40
CRESTVIEW 55 38 67 49 / 10 10 20 20
&&
.MOB WATCHES/WARNINGS/ADVISORIES...
AL...FREEZE WARNING UNTIL 8 AM SUNDAY FOR THE FOLLOWING ZONES: LOWER
BALDWIN...LOWER MOBILE...UPPER BALDWIN...AND UPPER MOBILE.
FL...FREEZE WARNING UNTIL 8 AM SUNDAY FOR THE FOLLOWING ZONES:
COASTAL ESCAMBIA...COASTAL OKALOOSA...COASTAL SANTA ROSA...
AND INLAND ESCAMBIA.
MS...FREEZE WARNING UNTIL 8 AM SUNDAY FOR THE FOLLOWING ZONES:
GEORGE...AND STONE.
GM...NONE.
&&
$$
