FXUS64 KMOB 052129
AFDMOB
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOBILE AL
328 PM CST SAT DEC 5 2009
.SHORT TERM (TONIGHT THROUGH TUESDAY NIGHT)...A COLD DOME OF HIGH
PRESSURE SETTLES INTO THE SOUTHEAST STATES OVERNIGHT WITH WINDS
BECOMING LIGHT OVER MUCH OF THE AREA. VERY DRY AIR ALOFT PROMOTES
EXCELLENT RADIATIONAL COOLING PROMOTING A COLD NIGHT TONIGHT. OUR
LOCAL HARD FREEZE WARNING CRITERIA IS LESS THAN 26F FOR MORE THAN 5
HOURS. THE DURATION IS CLOSE FOR INLAND MOBILE AND BALDWIN
COUNTIES...INLAND ESCAMBIA COUNTY FLORIDA...AND STONE AND GEORGE
COUNTIES...THREE TO FOUR HOURS...BUT THE CURRENT FREEZE WARNING WILL
HAVE TO SUFFICE THERE. THE DURATION CRITERIA IS MET FOR INLAND
SANTA ROSA AND OKALOOSA COUNTIES AND HAVE EXPANDED THE CURRENT HARD
FREEZE WARNING FOR THESE TWO AREAS WITH A FREEZE WARNING CONTINUING
FOR THE REMAINDER OF THE FORECAST AREA. A VERY ACTIVE PATTERN
FOLLOWS IN THE WAKE OF THE COLD AIR AS SEVERAL VIGOROUS SHORTWAVES
EJECT FROM A POSITIVELY TILTED UPPER TROF OVER THE WESTERN STATES.
THE DOME OF HIGH PRESSURE GRADUALLY MOVES OFF TO THE EAST AWAY FROM
THE AREA THROUGH SUNDAY NIGHT WHILE A SYSTEM ADVANCES ACROSS THE
PLAINS AND BRINGS A COLD FRONT TO NEAR THE LOWER MISSISSIPPI RIVER
VALLEY WITH A SURFACE WAVE MEANWHILE DEVELOPING ALONG THE FRONTAL
INTERSECTION WITH THE GULF COAST. AS THE PLAINS SYSTEM CONTINUES
EASTWARD ACROSS THE GREAT LAKES ON MONDAY...THE FRONT TENDS TO STALL
NEAR THE GULF COAST WITH THE SURFACE LOW/WAVE CONTINUING EASTWARD
ALONG THE COAST AND ENHANCING RAINFALL AS THE SURFACE WAVE NEARS AND
MOVES THROUGH THE AREA. HAVE KEPT SLIGHT CHANCE TO CHANCE POPS
CURRENTLY IN PLACE FOR THE WESTERN HALF OF THE FORECAST AREA SUNDAY
NIGHT INCREASING TO LIKELY OVER THE WESTERN THIRD OF THE AREA WITH
CHANCE ELSEWHERE FOR MONDAY. ANOTHER SURFACE LOW/WAVE DEVELOPS
MONDAY NIGHT OVER THE NORTHWESTERN GULF COAST IN RESPONSE TO MORE
SHORTWAVE ENERGY EJECTING FROM THE WESTERN STATES TROF. THIS
DIFFICULT TO TIME FEATURE MOVES ALONG THE OLD FRONTAL BOUNDARY ON
THE GULF COAST AND SUPPORTS CHANCE POPS ACROSS THE WESTERN HALF OF
THE FORECAST AREA MONDAY NIGHT WITH SLIGHT CHANCE ELSEWHERE. THE
ACTIVE PATTERN WILL HAVE MEANWHILE GENERATED A DEEP SYSTEM OVER THE
CENTRAL PLAINS WHICH MOVES TO THE MID MISSISSIPPI RIVER VALLEY BY
TUESDAY NIGHT AND BRINGS A STRONG COLD FRONT TO NEAR THE AREA.
THERE IS EXCELLENT AGREEMENT AMONG THE ECMWF AND THE GFS ON THIS
SYSTEM AND FAIRLY GOOD AGREEMENT AMONG THE TWO MODELS ON MOVING A
VIGOROUS SOUTHERN STREAM SHORTWAVE ACROSS THE FORECAST AREA DURING
TUESDAY AFTERNOON INTO TUESDAY NIGHT AHEAD OF THE APPROACHING
FRONT. SPC HAS THE FORECAST AREA OUTLOOKED FOR POSSIBLE SEVERE
STORMS DUE TO STRONG LOW LEVEL SHEAR FROM A 50-55 KNOT 850 MB JET
AND DESTABILIZATION DUE TO STRONG MOISTURE RETURN. THERE ARE TIMING
CONCERNS WITH THE LEADING SHORTWAVE SYSTEM BUT WITH THE ECMWF...GFS
AND 00Z GEM SUPPORTING PRECIP ACROSS THE AREA DURING THE PERIOD HAVE
GONE WITH LIKELY POPS TUESDAY INTO TUESDAY NIGHT WITH THE INCREASED
CONFIDENCE. /29
&&
.LONG TERM (WEDNESDAY THROUGH SATURDAY)...CONVECTION ASSOCIATED WITH
THE LEADING SHORTWAVE SYSTEM EXITS THE FORECAST AREA AND THE COLD
FRONT MOVES THROUGH THE AREA ON WEDNESDAY WITH DRY CONDITIONS
FOLLOWING IN THE WAKE OF THE FRONT. THE POSITIVELY TILTED WESTERN
STATES TROF FINALLY WEAKENS BUT SENDS YET ANOTHER SERIES OF
SHORTWAVES DOWNSTREAM WITH ANOTHER SURFACE LOW DEVELOPING IN THE
SOUTHERN PLAINS OR NEAR THE TEXAS COAST ON FRIDAY AND ADVANCING
EASTWARD. CHANCE POPS RETURN TO THE FORECAST FOR FRIDAY AND
CONTINUE THROUGH SATURDAY FOR THIS FEATURE. MILD TEMPERATURES ON
WEDNESDAY ARE FOLLOWED BY GENERALLY SEASONABLE TEMPERATURES IN THE
WAKE OF THE FRONT. /29
&&
.AVIATION (18Z ISSUANCE)...SKIES HAVE MOSTLY CLEARED OUT OVER LAND
AREAS OF THE FA...WITH ANY LOW CU CONFINED TO THE EASTERN BORDER OF
THE FA. THIS SHALL ERODE RAPIDLY. THE NORTHERLY SURGE IS RATER
LIMITED...WITH LIMITED MIXING DOWN OF ANY STRONGER WINDS ABOVE THE
SURFACE...SO GUST HAVE BEEN LIMITED. /16
&&
.MARINE...SURFACE HIGH PRESSURE OVER THE LOWER MISS RIVER VALLEY
WILL SHIFT NORTHEAST...TO OVER THE DELMARVA PENINSULA BY SUNDAY
NIGHT. THIS WILL ALLOW MODERATE NORTHERLY FLOW TO EASE SOMEWHAT
THROUGH TONIGHT...WHILE SHIFTING AND BECOMING EASTERLY BY SUNDAY
NIGHT. A RELATIVELY TIGHT GRADIENT OVER THE NORTHERN GULF WILL KEEP
WILL KEEP WINDS GENERALLY AT THE MODERATE LEVEL...ESPECIALLY ALONG
AND SOUTH OF THE BARRIER ISLANDS.
ONSHORE FLOW WILL RETURN BY MONDAY AS ANOTHER SYSTEM APPROACHES THE
AREA FROM THE WEST. ...PUSHING A FRONT OVER THE AREA...THEN STALLING
IT ALONG THE NORTHERN COAST MONDAY NIGHT. ANOTHER SYSTEM WILL PASS
WELL NORTH OF THE AREA TUESDAY INTO TUESDAY NIGHT...PUSHING THE
FRONT A BIT FARTHER SOUTH...ALBEIT SLOWLY LATER TUESDAY NIGHT INTO
WEDNESDAY NIGHT...THEN SOUTH OF THE AREA BY THURSDAY MORNING. /16
&&
.FIRE WEATHER...COLD HIGH PRESSURE WILL BRING FREEZING TEMPERATURES
TO THE AREA TONIGHT THEN THE HIGH PRESSURE SYSTEM MOVES OFF TO THE
EAST ON SUNDAY AS A LOW PRESSURE SYSTEM ADVANCES FROM THE SOUTHERN
PLAINS. GULF MOISTURE GRADUALLY RETURNS TO THE REGION SUNDAY
THROUGH MONDAY WITH RAIN CHANCES INCREASING AS THE LOW PRESSURE
SYSTEM NEARS THE AREA. RELATIVE HUMIDITIES WILL DROP BRIEFLY BELOW
CRITICAL LEVELS OVER THE INTERIOR PORTION OF THE NORTHWEST FLORIDA
PANHANDLE ON SUNDAY BUT WILL NOT SATISFY DURATION
REQUIREMENTS...OTHERWISE RELATIVE HUMIDITIES WILL REMAIN ABOVE
CRITICAL LEVELS THROUGH TUESDAY. /29
&&
.PRELIMINARY POINT TEMPS/POPS...
MOBILE 27 57 46 65 / 05 10 20 60
PENSACOLA 31 55 47 65 / 05 10 10 40
DESTIN 36 52 47 66 / 05 10 10 30
EVERGREEN 22 55 38 59 / 05 10 10 50
WAYNESBORO 21 53 39 59 / 05 10 30 60
CAMDEN 23 53 37 56 / 05 10 20 50
CRESTVIEW 23 55 38 64 / 05 10 10 40
&&
.MOB WATCHES/WARNINGS/ADVISORIES...
AL...HARD FREEZE WARNING FROM MIDNIGHT SUNDAY TO 8 AM SUNDAY FOR THE
FOLLOWING ZONES: BUTLER...CHOCTAW...CLARKE...CONECUH...
COVINGTON...CRENSHAW...ESCAMBIA...MONROE...WASHINGTON...AND
WILCOX.
FREEZE WARNING FROM MIDNIGHT SUNDAY TO 8 AM SUNDAY FOR THE
FOLLOWING ZONES: LOWER BALDWIN...LOWER MOBILE...UPPER
BALDWIN...AND UPPER MOBILE.
FL...FREEZE WARNING FROM MIDNIGHT SUNDAY TO 8 AM SUNDAY FOR THE
FOLLOWING ZONES: COASTAL ESCAMBIA...COASTAL OKALOOSA...
COASTAL SANTA ROSA...AND INLAND ESCAMBIA.
HARD FREEZE WARNING FROM MIDNIGHT SUNDAY TO 8 AM SUNDAY FOR THE
FOLLOWING ZONES: INLAND OKALOOSA...AND INLAND SANTA ROSA.
MS...HARD FREEZE WARNING FROM MIDNIGHT SUNDAY TO 8 AM SUNDAY FOR THE
FOLLOWING ZONES: GREENE...PERRY...AND WAYNE.
FREEZE WARNING FROM MIDNIGHT SUNDAY TO 8 AM SUNDAY FOR THE
FOLLOWING ZONES: GEORGE...AND STONE.
&&
$$
