FXUS64 KMOB 111106
AFDMOB
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOBILE AL
506 AM CST FRI DEC 11 2009
.SHORT TERM...(TODAY THROUGH TONIGHT) AS A WEAK UPPER SHORTWAVE
MOVES OVER THE NORTHERN GULF COAST LATER TODAY INTO TONIGHT...THERE
WILL BE AN INCREASE IN CLOUD COVER OVER THE FA AND FROM THE SOUTH
WEST...MOISTENING OF THE BOUNDARY LAYER. THEN AS ANOTHER SHORTWAVE
OVER THE PLAINS MOVES TOWARDS THE FA...THERE WILL BE AN INCREASE IN
THE CHANCES FOR RAIN TONIGHT. WITH A COLD AIRMASS OVER THE NORTHERN
GULF COAST...THE PRECIP LOOKS TO BE ISENTROPIC IN NATURE
AM HESITANT ATTM GOING CATEGORICAL WITH THE POPS...WITH THE PRECIP
YET TO SHOW WEST OF THE FA. WITH THE KMOB RADAR DOWN ATTM(SHOULD BE
BACK TODAY)...LIX IS SHOWING SOME RETURNS ON RADAR...BUT WITH 20
DEGREE PLUS TEMP/DEWPOINT SPREAD...MUCH OF THIS ISN'T HITTING THE
GROUND. MOST LIKELY SOME VIRGA WITH THE MID LEVEL CLOUD DECK OVER THE
GULF COAST.
WITH RESPECT TO THE DRY BOUNDARY LAYER...HAVE WENT TOWARDS THE
WETTER MAV/GFS SOLUTION WITH RESPECT TO DEWPOINTS AS FEEL THAT THE
INCOMING SHOWERS WILL HELP WITH TO MOISTEN THE BOUNDARY
LAYER...ESPECIALLY ALONG THE COAST. THE BIGGEST QUEST FOR DRY AIR
WILL BE THE NORTHWESTERN QUARTER OF THE FA...WITH THIS AREA EXPECTED
TO BE THE LAST TO SEE THE MOISTENING UP. /16
(SATURDAY THROUGH SUNDAY NIGHT) STRONG AND DEEP ISENTROPIC LIFT WILL
PERSIST THROUGH THE DAY SATURDAY AS THE WARM FRONT NEAR THE COAST
WILL HAVE A DIFFICULT TIME MOVING NORTH DUE TO THE COOL AIR WEDGE IN
PLACE. AS STRONG LOW LEVEL THETA-E ADVECTION CONTINUES...FORECAST
SOUNDINGS ARE SHOWING CLOSE TO 500 J/KG OF ELEVATED INSTABILITY
WHEN LIFTING A PARCEL FROM AROUND 900 MB. SO WE COULD SEE SOME
CONVECTIVE ELEMENTS AND THUNDER EMBEDDED IN THE STRATIFORM RAIN
SHIELD. THE CONVECTIVE POTENTIAL WILL LEAD TO THE POSSIBILITY OF SOME
LOCALLY HEAVY RAINFALL. HAVE INCLUDED BOTH THUNDER AND HEAVY RAINFALL
IN THE FORECAST FOR SATURDAY. THE TEMPERATURE FORECAST IS DIFFICULT
AS IT WILL DEPEND ON THE RATE OF EROSION OF THE COLD AIR WEDGE. OFTEN
TIMES MODELS DO NOT HANDLE THIS SITUATION WELL AT ALL. WITH THIS IN
MIND...HAVE STAYED ON THE COOLER SIDE OF GUIDANCE SHOWING HIGHS IN
THE MID 40S FAR INLAND TO MID 50S ALONG THE COAST.
MODEL GUIDANCE IS IN GOOD AGREEMENT ON SHIFTING THE COLD SFC HIGH
OVER THE CAROLINAS OFFSHORE SATURDAY NIGHT WHILE THE WEAK SFC LOW
OVER THE WESTERN GULF MOVES INLAND OVER LOUISIANA AND MISSISSIPPI. AS
THE HIGH LOSES ITS GRIP AND LOW LEVEL WARM AIR ADVECTION CONTINUES...
THE WARM FRONT SHOULD BEGIN TO MOVE FURTHER INLAND. IN THIS
SCENARIO...TEMPERATURES WILL ACTUALLY RISE THROUGH THE NIGHT WITH LOW
TEMPS OCCURRING AT THE VERY BEGINNING OF THE EVENING. HAVE INTRODUCED
A NON DIURNAL CURVE TO THE GRIDDED FORECAST AND INTRODUCED
TEMPERATURES RISING INTO THE TEXT PRODUCT. DYNAMICS STILL LOOK TO BE
GOOD SATURDAY NIGHT AS WE STAY IN THE RIGHT ENTRANCE REGION OF A
STRONG JET LOCATED OVER THE TN VALLEY. ISENTROPIC LIFT WILL KEEP
GOING ALONG AND TO THE NORTH OF THE BOUNDARY WITH AREAS SOUTH OF THE
FRONT BECOMING UNSTABLE...WITH THE POTENTIAL FOR SOME SFC BASED
CONVECTION CLOSER TO THE COAST. NOT LOOKING AT MUCH OF A SEVERE
THREAT GIVEN THAT 0-6KM SHEAR WILL ONLY BE ABOUT 25-30 KT AND MID
LEVEL LAPSE RATES REMAIN POOR. HOWEVER...WITH PRECIP WATERS OVER 1.75
INCHES...THE THREAT FOR HEAVY RAINFALL WILL CONTINUE. WE THINK AT
THIS POINT ANY FLASH FLOODING THREAT WILL REMAIN LOCALIZED TO
STRONGER CONVECTION. OTHERWISE...THE DURATION OF THE PRECIP EVENT
WILL BE LONG ENOUGH TO NEGATE THE THREAT AS 6 HR FLASH FLOOD GUIDANCE
IS STILL 4-6 INCHES ACROSS THE AREA. HOWEVER...THE GROUND IS RATHER
SATURATED AND WE WILL HAVE TO MONITOR THINGS VERY CAREFULLY. RIGHT
NOW WE ARE LOOKING AT 2-4 INCH STORM TOTALS ACROSS THE REGION WITH
THE POTENTIAL FROM SOME ISOLATED HIGHER TOTALS. WILL REASSESS THE
POTENTIAL FOR ANY TYPE OF FLOOD WATCH WITH THIS AFTERNOONS PACKAGE.
BEST CHANCE OF CONVECTION SUNDAY WILL BE IN THE SOUTH AND EAST WHERE
THE AIRMASS WILL REMAIN SOMEWHAT UNSTABLE DUE TO THE LINGERING SFC
BOUNDARY. START TO SEE SOME BROAD SHORTWAVE RIDGING BUILDING BY
SUNDAY AFTERNOON WITH DYNAMICS BEGINNING TO WEAKEN...SO EXPECT TO SEE
DECREASING CHANCES FOR PRECIP AS THE DAY PROGRESSES. IT WILL TURN
RATHER WARM ACROSS THE REGION AS 1000-850MB THICKNESSES RISE FROM
1375M IN THE NORTH TO NEAR 1390M IN THE SOUTH. THIS SUPPORTS HIGHS IN
THE LOW TO MID 70S. THE SFC BOUNDARY IS STILL EXPECTED TO BE DRAPED
ACROSS THE AREA SUNDAY NIGHT WITH THE PRESSURE GRADIENT WEAKENING.
ANY OSCILLATIONS IN THE FRONT WILL PLAY HAVOC WITH LOW TEMPS. COULD
BE A BIG CONTRAST ACROSS THE CWA WITH LOW 50S NORTH TO LOW 60S CLOSE
TO THE COAST. WILL HAVE TO MONITOR FOR THE POTENTIAL OF DENSE
FOG...ESPECIALLY OVER MOBILE BAY AND THE NEAR SHORE WATERS. 34/JFB
.LONG TERM...(MONDAY THROUGH THURSDAY) THE RESPITE FROM THE RAIN WILL
BE SHORT LIVED AS THE NEXT COLD FRONT BEGINS TO APPROACH LATE MONDAY.
A STRENGTHENING SOUTHERLY FLOW AHEAD OF THIS SYSTEM WILL SPREAD THE
WARM AND MOIST AIRMASS FURTHER INLAND...ALLOWING AT LEAST SOME
INSTABILITY TO MATERIALIZE. WILL KEEP A HOLD OF CHANCE POPS AS
SCATTERED SHOWER AND THUNDERSTORMS ARE POSSIBLE NEAR THE RETREATING
WARM FRONT.
RAIN CHANCES INCREASE IN EARNEST MONDAY NIGHT INTO TUESDAY AS THE COLD
FRONT ENTERS THE REGION. SHOULD SEE PRECIP END LATE TUESDAY
AFTN/TUESDAY EVENING BASED ON THE LATEST GUIDANCE. STILL
DISAGREEMENT BETWEEN THE GFS AND ECMWF ON JUST HOW MUCH COLD AIR WILL
FILTER IN BEHIND THE FRONT. THE GFS IS PHASED WITH ITS NORTHERN AND
SOUTHERN STREAMS...ALLOWING AN ARCTIC AIRMASS TO DIVE ALL THE WAY
SOUTH TO THE COAST. THE ECMWF HOLDS BACK ENERGY IN THE SOUTHERN
STREAM...ALSO HOLDING BACK MUCH OF THE ARCTIC AIR. WILL TREND THE
FORECAST ABOUT A CATEGORY BELOW NORMAL FOR WED AND THU FOR NOW UNTIL A
BETTER CONSENSUS IS REACHED. IF THE GFS SOLUTION WERE CORRECT...IT
WOULD LIKELY BRING ONE OF THE COLDEST AIRMASSES OF THE SEASON TO THE
AREA. 34/JFB
&&
.AVIATION...(12Z ISSUANCE) ISENTROPIC UPGLIDE INDUCED SHOWERS OVER
THE AREA WILL BE ON THE INCREASE...WITH COASTAL AREAS SEEING THE
SHOWERS FIRST THEN SPREAD NORTH AS THE UPGLIDE ENHANCEMENT SPREADS
NORTH. GUIDANCE IS NOT ADVERTISING ANY DRASTIC DROP IN VIS UNTIL
LATER TONIGHT INTO SATURDAY...AND SEE NO REASON TO DISAGREE. /16
&&
.MARINE...AS A WEAK UPPER SHORTWAVE MOVES TOWARDS THE AREA TODAY
INTO TONIGHT...A DEVELOPING SURFACE LOW OVER THE WESTERN GULF WILL
MOVE A WARM FRONT TOWARDS THE MARINE FA...MAINTAINING A STRONG
EASTERLY FLOW INTO SATURDAY. A WEAK FRONT WILL MOVE OVER THE AREA
SUNDAY...BUT WILL QUICKLY STALL...THEN WASH OUT AS A STRONGER SYSTEM
MOVES OVER THE PLAINS. THIS SYSTEM WILL PUSH A STRONG FRONT OVER THE
AREA TUESDAY. MEDIUM RANGE GUIDANCE IS HINTING AT GALES AFTER THE
FROPA. AM HOLDING OFF ON GOING GALES AS THIS JUMP IS IN THE COURSER
EXTENDED SECTION OF THE GFS. /16
&&
.FIRE WEATHER...HIGH PRESSURE OVER THE TENNESSEE VALLEY CONTINUES TO
SUPPORT A DRY AND CHILLY AIRMASS ACROSS THE REGION. AFTERNOON RH
VALUES ARE EXPECTED TO DROP INTO THE UPPER 20 TO LOWER 30 PERCENT
RANGE ACROSS INLAND SOUTHWEST AND SOUTH CENTRAL ALABAMA AS WELL AS
THE FLORIDA PANHANDLE. CURRENTLY...DURATIONS OF CRITICALLY LOW
HUMIDITY VALUES LOOK TO FALL SHORT OF RED FLAG WARNING CRITERIA. A
STALLED FRONT OVER THE GULF WILL BEGIN TO MOVE TO THE NORTH
TONIGHT...EVENTUALLY MOVING INLAND BY LATE SATURDAY. WIDESPREAD RAIN
IS FORECAST TO DEVELOP ACROSS THE REGION BY SATURDAY...WITH MOST
EVERY LOCATION SEEING A SOAKING RAIN. 34/JFB
&&
.PRELIMINARY POINT TEMPS/POPS...
MOBILE 46 40 53 53 / 30 70 90 80
PENSACOLA 48 41 55 54 / 30 60 90 80
DESTIN 50 43 55 54 / 30 60 90 80
EVERGREEN 47 38 48 48 / 20 50 90 80
WAYNESBORO 48 35 47 47 / 20 60 90 80
CAMDEN 47 36 46 46 / 20 50 90 80
CRESTVIEW 47 39 50 50 / 20 50 90 80
&&
.MOB WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
FL...NONE.
MS...NONE.
GM...SMALL CRAFT ADVISORY UNTIL NOON SATURDAY 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.
&&
$$
