Flash Flood Watch 12, NWS Mobile, AL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOBILE AL
400 AM CST SUN DEC 13 2009

.SHORT TERM...TODAY THROUGH TONIGHT...THE LATEST SURFACE ANALYSIS SHOWS
THE WARM FRONTAL BOUNDARY ACROSS THE MARINE AREA...JUST SOUTH OF
42012...WESTWARD TO EXTREME SOUTHEAST LOUISIANA TO WHERE A DIFFUSE
SURFACE LOW IS LOCATED.  THE WEAK SURFACE LOW MOVES EASTWARD ACROSS
ALABAMA INTO GEORGIA AND IS ABSORBED BY A STRONGER SYSTEM MOVING UP
THE EAST COAST.  THE WARM FRONT MEANWHILE MOVES NORTHWARD THROUGH
THE FORECAST AREA AND IS FOLLOWED BY A WEAK COLD FRONT WHICH MOVES
INTO THE AREA THIS AFTERNOON AND STALLS.  UPSTREAM RADARS SHOW
PRECIP GRADUALLY SHIFTING EASTWARD WITH THE DIFFUSE SURFACE
LOW/APPROACHING WEAK COLD FRONT BUT DEEP LAYER MOISTURE TENDS TO
REMAIN OVER THE AREA WITH PRECIPITABLE WATER VALUES AROUND 1.5
INCHES THROUGH TONIGHT.  WITH THE WEAK SURFACE LOW MOVING OFF TO THE
EAST...WILL HAVE CHANCE POPS OVER THE WESTERNMOST MISSISSIPPI
COUNTIES THIS MORNING WITH LIKELY OVER MUCH OF THE REMAINING AREA
EXCEPT FOR CATEGORICAL POPS OVER THE NORTHEASTERN-MOST
COUNTIES...TAPERING OFF TO SLIGHT CHANCE FOR MUCH OF THE AREA AND
CHANCE OVER THE NORTHEASTERN PORTION.  RAINFALL RATES HAVE BEEN
TAPERING OFF IN THE WEAKENING OVERRUNNING PATTERN BUT WILL KEEP THE
FLASH FLOOD WATCH IN EFFECT UNTIL EXPIRATION AT 9 AM FOR EXTREME
SOUTHWEST ALABAMA...SOUTH CENTRAL ALABAMA AND PART OF THE NORTHWEST
FLORIDA PANHANDLE DUE TO SATURATED GROUND CONDITIONS UNTIL RAINFALL
RATES WILL HAVE DECREASED SUFFICIENTLY.  HAVE ISSUED AN AREAL FLOOD
WARNING FOR A PORTION OF THIS AREA EARLIER...GENERALLY EXTREME
SOUTHWEST ALABAMA AND PART OF THE NORTHWEST FLORIDA PANHANDLE DUE TO
AREAL FLOODING IN EXCESS OF 6 HOURS WHICH WOULD NOT BE APPROPRIATE
FOR A FLASH FLOOD WARNING...AND THIS WILL BE ALLOWED TO EXPIRE AS
SCHEDULED AS BY THEN SWOLLEN STREAMS AND CREEKS WILL HAVE RECEDED
WITH THE DECREASING RAINFALL RATES.  SURFACE BASED CAPES INCREASE TO
AROUND 1000 J/KG THIS AFTERNOON GENERALLY OVER THE SOUTHERN THIRD OF
THE FORECAST AREA AS WARM MOIST AIR MOVES INTO THE REGION IN THE
WAKE OF THE WARM FRONT BUT SHEAR WILL BE GENERALLY LOW...80 TO 100
M2/S2.  DESPITE THIS MORE FAVORABLE CONVECTIVE ENVIRONMENT...DEEP
LAYER LIFT WILL BE MINIMAL AT BEST WITH THE DEPARTURE OF THE SURFACE
LOW AND NO SIGNIFICANT SHORTWAVES AFFECTING THE AREA SO WILL JUST
HAVE ISOLATED TO SCATTERED THUNDERSTORMS MATCHING THE AFOREMENTIONED
POPS.  WITH DEEP MOISTURE REMAINING OVER THE AREA AND THE STALLED
FRONTAL BOUNDARY MOVING NORTHWARD OUT OF THE FORECAST AREA LATE
TONIGHT...WILL KEEP IN SLIGHT CHANCE POPS FOR MUCH OF THE AREA.
MILDER TEMPERATURES FOLLOW TODAY FOR THE AREA TODAY AND TONIGHT. /29

FOR MONDAY INTO MONDAY NIGHT...THE BEGINNING OF THE NEXT ROUND OF
PRECIP IS A BIT SKETCHY AMONGST THE GUIDANCE. ALL AGREE THAT A STRONG
SHORTWAVE IS PUSHING A FRONT SOUTHEAST OVER THE PLAINS/MID MISS RIVER
VALLEY MONDAY...BUT DIFFER ON THE STRENGTH OF SOME SHORTWAVE ENERGY
MOVING NORTHEAST THROUGH THE ZONAL FLOW OVER THE SOUTHERN PLAINS TO
SOUTHEASTERN CONUS. GFS IS STRONGER WITH THIS ENERGY...WHEN COMBINED
WITH A WEAK FRONTAL PUSH IN THE GFS TODAY THROUGH TONIGHT...HAS RESULTED IN
MUCH HIGHER POPS FOR MONDAY...ALMOST 50 PERCENT IN SOME CASES. HAVE
WENT IN THE MIDDLE AS THE SLOSHING AROUND IN THE FIRST TWO PERIODS
WILL DICTATE THE REST OF THE SHORT TERM. MODEL SOUNDINGS SHOW LIMITED
INSTABILITY...BUT ENOUGH FOR THE POSSIBILITY OF THUNDERSTORMS...SO
HAVE LIMITED ANY RUMBLING TO THE AFTERNOON INTO MONDAY NIGHT.

AS MONDAY NIGHT PROGRESSES...AND THE FRONT OVER THE PLAINS MOVES OVER
THE LOWER MISS RIVER VALLEY TOWARDS THE FA...THE CHANCE FOR RAIN WILL
BE ON THE INCREASE. NAM IS STILL ADVERTISING LOWER POPS THAN THE
GFS...CONCENTRATING THE BEST CHANCE FOR RAIN CLOSER TO THE FRONT AND
ITS LOW LEVEL CONVERGENCE. STILL ENOUGH INSTABILITY FOR RUMBLES...BUT
WITH THE DECREASE IN THE OVERNIGHT HOURS...HAVE BACKED OFF IN THE
THUNDER COVERAGE WITH RESPECT TO RAIN COVERAGE.

FOR TUESDAY...GUIDANCE IS ADVERTISING THE FRONT BEING PUSHED ACROSS THE
FA TO THE SOUTHERN REACHES OF THE MARINE PORTION OF THE FA BY TUESDAY EVENING.
NAM STILL UNDER THE GFS WITH RESPECT TO POPS...ESPECIALLY ALONG THE
COAST. MODEL SOUNDINGS SHOW A DECENT AMOUNT OF INSTABILITY...JUST NOT
SURFACE BASED...SO AM LEANING TOWARDS THE GFS SOLUTION FOR TUESDAY.
LOOKING AT ANY CHANCE FOR SEVERE WEATHER...LARGE SCALE DYNAMICS ON THE
WEAK SIDE...THOUGH BOTH MODELS ARE ADVERTISING A SMALL LOW LEVEL JET
DEVELOPING TUESDAY AFTERNOON...COINCIDENT WITH THE SURFACE FRONT.
SHEAR IS UNIDIRECTIONAL IN THE MODEL SOUNDINGS...SO IF ANY CHANCE FOR
SEVERE WEATHER IS TO BE ANTICIPATED...IT MOST LIKELY WILL BE DURING
THE DAY TUESDAY.

.LONG TERM...(TUESDAY NIGHT ON)FOR TUESDAY NIGHT INTO FRIDAY...AS THE
UPPER DYNAMICS PUSHING TUESDAYS FRONT CONTINUES SOUTH...PUSHING THE
FRONT WITH...IT STALLS OVER THE SOUTHERN GULF(ECMWF) OR NORTHERN LATIN
AMERICA(GFS). THE MORE NORTHWARD POSITION OF THE ECMWF...WHEN
COMBINED WITH A SHORTWAVE SYSTEM DIVING SOUTH OVER THE ROCKIES LATE
THURSDAY INTO FRIDAY...RESULTS IN A BETTER CHANCE FOR RAIN LATER
FRIDAY INTO THE COMING WEEKEND. GFS ENSEMBLES ARE EVEN DRIER THAN THE
GFS...SO HAVE STUCK WITH THE MODEL IN THE MIDDLE(GFS FOR NOW).
THIS MEANS DAYTIME TEMPS A BIT BELOW SEASONAL...OVERNIGHT LOWS WELL
BELOW SEASONAL FOR MID WEEK...SETTLING INTO TEMPS A BIT BELOW
SEASONAL...BOTH DAYTIME AND OVERNIGHT FOR THE WEEKEND.

&&

.AVIATION...(12Z ISSUANCE)LOW CEILINGS AND OCCASIONAL LIGHT FOG
PERSIST FOR THE NEXT 24 HOURS WITH THE PERIODS OF RAIN TAPERING OFF
DURING THE DAY. /29

&&

.MARINE...THE WARM FRONT CURRENTLY LOCATED OVER THE COASTAL WATERS
WILL MOVE INLAND EARLY TODAY AS THE WEAK SURFACE LOW OVER SOUTHERN
MISSISSIPPI CONTINUES EASTWARD ACROSS THE SOUTHEAST STATES.
EASTERLY WINDS AT 15-25 KNOTS VEER TO THE SOUTH AND DECREASE IN THE
WAKE OF THE WARM FRONT.  PLAN TO ALLOW THE SMALL CRAFT ADVISORY
CURRENTLY IN EFFECT TO EXPIRE AT 6 AM AS WINDS SHOULD HAVE DROPPED
BELOW 20 KNOTS BY THEN WITH SEAS 6 FEET OR LESS.  LIGHT ONSHORE FLOW
FOLLOWS THROUGH MONDAY NIGHT WHILE A COLD FRONT ADVANCES ACROSS THE
PLAINS.  THE COLD FRONT MOVES THROUGH TUESDAY AFTERNOON WITH A
STRONG NORTHERLY FLOW FOLLOWING IN THE WAKE OF THE FRONT.  THE
STRONG OFFSHORE FLOW GRADUALLY VEERS AROUND TO THE NORTHEAST THROUGH
THURSDAY AND DECREASES SOMEWHAT AS A STRONG SURFACE HIGH BUILDS INTO
THE EASTERN STATES. /29

&&

.FIRE WEATHER...RAIN WILL CONTINUE OVER THE AREA INTO TODAY...THEN
TAPER OFF FOR A SHORT TIME BEFORE THE NEXT ROUND OF PRECIP STARTS
LATER MONDAY...LASTING INTO TUESDAY...ENDING SHORTLY AFTER A FRONT
MOVES ACROSS THE AREA. THIS FRONT WILL BRING IN A DRIER...COOLER
AIRMASS TO THE AREA FOR MID WEEK.

&&

.PRELIMINARY POINT TEMPS/POPS...
MOBILE      72  63  71  62  70 /  60  20  50  70  70
PENSACOLA   73  63  72  62  72 /  60  20  50  70  70
DESTIN      73  65  70  61  71 /  60  20  40  70  60
EVERGREEN   70  56  72  60  71 /  70  20  50  70  70
WAYNESBORO  68  54  70  57  65 /  60  20  50  70  70
CAMDEN      69  55  71  58  68 /  70  20  50  70  70
CRESTVIEW   73  58  73  60  72 /  70  20  50  70  70

&&

.MOB WATCHES/WARNINGS/ADVISORIES...
AL...FLASH FLOOD WATCH UNTIL 9 AM SUNDAY FOR THE FOLLOWING ZONES:
     BUTLER...CONECUH...COVINGTON...CRENSHAW...ESCAMBIA...LOWER
     BALDWIN...LOWER MOBILE...UPPER BALDWIN...AND UPPER MOBILE.

FL...FLASH FLOOD WATCH UNTIL 9 AM SUNDAY FOR THE FOLLOWING ZONES:
     COASTAL ESCAMBIA...INLAND ESCAMBIA...INLAND OKALOOSA...AND
     INLAND SANTA ROSA.

MS...NONE.
GM...SMALL CRAFT ADVISORY UNTIL 6 AM SUNDAY FOR THE FOLLOWING ZONES:
     COASTAL WATERS FROM DESTIN TO PENSACOLA FL OUT 20 NM...
     COASTAL WATERS FROM PENSACOLA FL TO PASCAGOULA MS OUT 20
     NM...MOBILE BAY...WATERS FROM DESTIN TO PENSACOLA FL FROM
     20 TO 60 NM...AND WATERS FROM PENSACOLA FL TO PASCAGOULA MS
     FROM 20 TO 60 NM.

&&

29/16

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE MOBILE AL
325 PM CST SUN DEC 13 2009

ALZ051>064-FLZ001>006-GMZ630-650-655-670-675-MSZ067-075-076-078-
079-141915-
CHOCTAW-WASHINGTON-CLARKE-WILCOX-MONROE-CONECUH-BUTLER-CRENSHAW-
ESCAMBIA-COVINGTON-UPPER MOBILE-UPPER BALDWIN-LOWER MOBILE-
LOWER BALDWIN-INLAND ESCAMBIA-COASTAL ESCAMBIA-INLAND SANTA ROSA-
COASTAL SANTA ROSA-INLAND OKALOOSA-COASTAL OKALOOSA-MOBILE BAY-
COASTAL WATERS FROM PENSACOLA FL TO PASCAGOULA MS OUT 20 NM-
COASTAL WATERS FROM DESTIN TO PENSACOLA FL OUT 20 NM-
WATERS FROM PENSACOLA FL TO PASCAGOULA MS FROM 20 TO 60 NM-
WATERS FROM DESTIN TO PENSACOLA FL FROM 20 TO 60 NM-WAYNE-PERRY-
GREENE-STONE-GEORGE-
325 PM CST SUN DEC 13 2009

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTH CENTRAL
ALABAMA...SOUTHWEST ALABAMA...NORTHWEST FLORIDA...SOUTHEAST
MISSISSIPPI AND THE COASTAL WATERS OF ALABAMA AND NORTHWEST FLORIDA

.DAY ONE...TODAY THROUGH TONIGHT

DENSE FOG WILL DEVELOP THIS EVENING AND CONTINUE THROUGH MONDAY
MORNING. A DENSE FOG ADVISORY HAS BEEN ISSUED FOR SOUTHEAST
MISSISSIPPI...SOUTHWEST ALABAMA AND NORTHWEST FLORIDA. DENSE FOG IS
ALSO EXPECTED ACROSS THE NEAR SHORE COASTAL WATERS INCLUDING MOBILE
BAY WHERE A DENSE FOG ADVISORY IS ALSO IN EFFECT.

SEVERAL RIVERS IN SOUTHEAST MISSISSIPPI AND WESTERN ALABAMA ARE
CURRENT IN FLOOD STAGE...WITH SEVERAL MORE ABOVE ACTION STAGE...AN
INDICATION OF NUISANCE FLOODING.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

SCATTERED SHOWERS AND THUNDERSTORMS WILL DEVELOP ON MONDAY AND
BECOME NUMEROUS MONDAY NIGHT THROUGH TUESDAY AHEAD OF A COLD FRONT
APPROACHING FROM THE WEST. WHILE SEVERE WEATHER DEVELOPMENT IS NOT
EXPECTED...THE ADDITIONAL HEAVY RAIN MAY CREATE ADDITIONAL FLOODING
PROBLEMS AND A FLASH FLOOD WATCH IS IN EFFECT FROM MONDAY AFTERNOON
THROUGH TUESDAY EVENING.

HAZARDOUS CONDITIONS FOR SMALL CRAFT OVER THE MARINE AREA CAN BE
EXPECTED IN THE WAKE OF THE COLD FRONT LATE TUESDAY THROUGH
WEDNESDAY.

WITH SOME AREAS RECEIVING THREE TO FOUR INCHES OR MORE OF
RAIN...SEVERAL RIVERS OVER THE AREA WILL RISE ABOVE ACTION
STAGE...CAUSING NUISANCE FLOODING ALONG THESE RIVERS. SOME RIVERS
WILL RISE ABOVE FLOOD STAGE...CREATING MORE PROBLEMATIC FLOODING
CONDITIONS ALONG THESE RIVERS. SOME AREA RIVERS ARE ALREADY IN FLOOD
AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

ACTIVATION OF STORM SPOTTERS AND EMERGENCY MANAGEMENT SHOULD NOT BE
REQUIRED THROUGH TONIGHT.