250  
FXUS64 KMOB 210505  
AFDMOB  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MOBILE AL  
1105 PM CST MON FEB 20 2017  
   
DISCUSSION
 
UPDATED FOR LATEST AVIATION DISCUSSION BELOW.  
 

 
   
AVIATION
 
 
06Z ISSUANCE...CLOUD COVERAGE IS GRADUALLY INCREASING AND  
CEILINGS LOWERING AS ONGOING SHOWER ACTIVITY ENTERS THE LOCAL  
AREA FROM THE WEST. LOWEST CIGS DOWN TO LIFR CATEGORIES ARE  
POSSIBLE. STRONGEST BAND OF PRECIP PROGGED TO ENTER SW AL AFTER  
21.09Z AND WESTERN FL PANHANDLE BY 21.16Z, WITH A FEW  
THUNDERSTORMS ALSO POSSIBLE MAINLY DURING DAYTIME HOURS. EXPECT  
IFR CEILINGS, SOUTHWESTERLY TO WESTERLY WINDS, AND PERHAPS A FEW  
SHOWERS TO LINGER INTO TUESDAY NIGHT, ESPECIALLY ACROSS WESTERN  
PORTIONS OF THE LOCAL AREA. LOWER CIGS/VIS AND GUSTY WINDS WILL BE  
POSSIBLE IN THE HEAVIEST SHOWERS AND THUNDERSTORMS. /49  
 

 
   
PREV DISCUSSION
 
/ISSUED 1007 PM CST MON FEB 20 2017/  
 
DISCUSSION...SEE UPDATED INFORMATION FOR LAND AREAS BELOW.  
 
UPDATE...BASED ON LATEST MODEL GUIDANCE AND OBS TRENDS, HAVE  
UPDATED POPS TO MORE ACCURATELY REFLECT THE TIMING OF SHOWERS AND  
THUNDERSTORMS TONIGHT THROUGH TUESDAY NIGHT. AT THIS TIME, THE  
MAIN SQUALL LINE AND ITS ATTENDANT TRAILING STRATIFORM REGION ARE  
VISIBLE ON NEIGHBORING RADARS ADVANCING EASTWARD ACROSS SOUTHERN  
MS AND EASTERN LA, WITH A FEW ISOLATED SHOWERS ALSO FORMING AHEAD  
OF THIS LINE ACROSS COASTAL SOUTHEAST MS. THIS SQUALL LINE IS  
CURRENTLY EXPECTED TO REACH THE AL BORDER BY ROUGHLY 6 AM CST AND  
THE NORTHWESTERN FL PANHANDLE AROUND 9 AM CST.  
 
SHOWERS WITH BRIEF, HEAVY DOWNPOURS WILL BE THE PRIMARY THREAT,  
THOUGH A FEW RUMBLES OF THUNDER COULD POTENTIALLY MIX IN TUESDAY  
AFTERNOON AS MODEST INSTABILITY DEVELOPS ACROSS THE LOCAL AREA.  
STILL LOOKING AT RAINFALL AMOUNTS OF 1 TO 3 INCHES FOR MOST AREAS,  
THOUGH A FEW LOCALLY HIGHER AMOUNTS WILL BE POSSIBLE. THE  
HEAVIEST PRECIP IS THEN PROGGED TO EXIT THE LOCAL AREA TO THE  
SOUTH AND EAST LATE TUESDAY NIGHT. /49  
 
PREV DISCUSSION... /ISSUED 359 PM CST MON FEB 20 2017/  
 
NEAR TERM /NOW THROUGH TUESDAY/...WEATHER MAPS CONTINUE TO  
REFLECT A HIGHLY AMPLIFIED REPRESENTATION IN THE UPPER LEVEL  
HEIGHT FIELDS WITH A SHARP RIDGE AXIS EXTENDING NORTHWARD FROM THE  
WESTERN CARIBBEAN TO THE OHIO RIVER VALLEY. WEST OF THIS FEATURE,  
TROF AXIS WAS MOVING EASTWARD OVER THE PLAINS STATES. AT THE  
SURFACE, A NARROW NORTH TO SOUTH HIGH PRESSURE RIDGE EXTENDS FROM  
THE EASTERN GREAT LAKES, SOUTH TO FLORIDA. AN ASSESSMENT OF DEEP  
LAYER MOISTURE FROM 20.12Z WEATHER BALLOON RELEASES SHOW GULF  
MOISTURE OPENING UP FROM THE WESTERN GULF, NORTHWARD INTO THE  
EASTERN PLAINS AHEAD OF FRONTAL ZONE. FROM A CLIMATOLOGICAL  
PERSPECTIVE, MOISTURE VALUES IN THESE AREAS RANGE FROM 150% OF  
NORMAL OVER THE WESTERN GULF TO 300-400% OF NORMAL FROM KANSAS TO  
MINNESOTA.  
 
MOVING INTO THE NEAR TERM FORECAST, CLOUDS ARE FORECAST TO BEGIN  
SPREADING IN FROM THE WEST AND MAY BEGIN TO SEE A SMALL CHANCE OF  
SHOWERS BREAKING OUT OVER THE WESTERN ZONES BY MIDNIGHT. PATCHY  
FOG WILL ALSO BE MENTIONED AS WELL. ANOMALOUSLY HIGH LEVELS OF  
DEEP LAYER MOISTURE SHIFTS EASTWARD OVER THE CENTRAL GULF COAST  
WHERE PWAT VALUES RANGE BETWEEN 1.5 TO 1.7 INCHES BY DAYBREAK  
TUESDAY AND CONTINUING THRU THE COURSE OF THE DAY. AS DEEP LAYER  
ASCENT, ASSOCIATED WITH THE SLOW EASTWARD MOVEMENT OF A LARGE AND  
COMPLEX LOW PRESSURE SYSTEM OVER THE DEEP SOUTH OPERATES ON THIS  
MOISTURE, CATEGORICAL CHANCES OF SHOWERS WILL BE IN PLACE. A FEW  
STORMS POSSIBLY MIXED IN AS WELL. LOCALLY HEAVY RAINS POSSIBLE.  
AREA RAIN GAUGES COULD SEE RAIN AMOUNTS TOTALING 1 TO 3 INCHES. A  
FEW AREAS COULD SEE LOCALLY HIGHER AMOUNTS. THERE IS A MARGINAL  
RISK OF EXCESSIVE RAIN ALONG THE GULF COAST, WHICH EQUATES TO A  
2-5% PROBABILITY OF RAINFALL EXCEEDING FLASH FLOOD GUIDANCE. RISK  
OF SEVERE WEATHER IS LOW.  
 
OVERNIGHT LOWS REMAIN WELL ABOVE SEASONAL, RANGING FROM THE UPPER  
50S INTERIOR TO MID 60S COAST. WITH CLOUDS AND RAINS, DAYTIME  
HIGHS TUESDAY MORE TEMPERED AS SEEN PAST COUPLE DAYS, RANGING  
FROM 69 TO 73. /10  
 
SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...THE ECMWF,  
GFS, AND NAM MODELS ARE IN EXCELLENT AGREEMENT IN THE PLACEMENT OF  
THE UPPER LOW PRESSURE AREA OVER SOUTHERN MISSISSIPPI/SOUTHEAST  
LOUISIANA BY EARLY TUESDAY EVENING. ALL THE MODELS THEN MOVE THE  
SYSTEM SOUTHEAST THROUGH MIDWEEK, REACHING THE EAST CENTRAL GULF  
OF MEXICO BY LATE WEDNESDAY EVENING. THE LOW THEN TAKES A JOG TO  
THE EAST ACROSS THE FLORIDA PENISULA, REACHING THE CARIBBEAN  
ISLANDS BY THE END OF THE SHORT TERM. A LINE OF MODERATE TO HEAVY  
RAIN SHOWERS WITH EMBEDDED THUNDERSTORMS (60 TO 90 PERCENT CHANCE)  
WILL BE ONGOING TUESDAY EVENING ACROSS SOUTH CENTRAL ALABAMA AND  
THE WESTERN FLORIDA PANHANDLE, WITH SCATTERED LINGERING SHOWERS  
FURTHER TO THE WEST. THIS LINE OF HEAVY RAIN WILL MOVE EAST OF  
THE FORECAST AREA BEFORE MIDNIGHT, HOWEVER ISOLATED TO SCATTERED  
WARP-AROUND RAIN SHOWERS WILL PERSIST ACROSS THE ENTIRE FORECAST  
AREA THROUGH WEDNESDAY AFTERNOON AS THE UPPER LOW TRACKS FURTHER  
SOUTHEAST OVER THE NORTH CENTRAL GULF, AND AN ASSOCIATED SURFACE  
LOW FORMS OVER THE NORTHEAST GULF. DRIER AIR WILL FOLLOW IN THE  
WAKE OF THE SYSTEM WEDNESDAY NIGHT THROUGH THURSDAY NIGHT, WITH  
NO PRECIPITATION IN THE FORECAST.  
 
ADDITIONAL WIDESPREAD RAINFALL AMOUNTS TUESDAY EVENING THROUGH  
WEDNESDAY AFTERNOON ARE EXPECTED TO RANGE FROM ONE-QUARTER TO  
THREE-QUARTERS OF AN INCH EAST OF THE LINE FROM CAMDEN, ALABAMA  
TO PENSACOLA, FLORIDA, WITH LESS THEN ONE-QUARTER OF AN INCH WEST  
OF THIS LINE.  
 
LOW TEMPERATURES TUESDAY, WEDNESDAY AND THURSDAY NIGHTS WILL RANGE  
FROM 53 TO 60 DEGREES. COOLER HIGH TEMPERATURES ARE FORECAST FOR  
WEDNESDAY DUE TO THE RAIN AND CLOUDS, BUT STILL AROUND 8 DEGREES  
ABOVE NORMAL, RANGING FROM 70 TO 75 DEGREES. VERY WARM HIGH  
TEMPERATURES WILL RETURN ON THURSDAY WITH HIGHS RANGING FROM 74  
TO 79 DEGREES, EXCEPT FOR LOWER 70S ALONG THE BEACHES. /22  
 
LONG TERM /FRIDAY THROUGH MONDAY/...THE DRY PERIOD WILL PERSIST  
THROUGH FRIDAY AFTERNOON AS WEAK UPPER AND SURFACE RIDGES REMAIN  
OVER THE REGION. A LARGE BROAD UPPER LEVEL TROUGH STRETCHING FROM  
THE PACIFIC NORTHWEST TO THE NORTHERN GREAT PLAINS WILL MOVES EAST  
AND CARVE OUT A LONGWAVE TROUGH OVER THE EASTERN CONUS BY LATE IN  
THE WEEK, AS A VERY STRONG SURFACE LOW PRESSURE AREA ACROSS  
NORTHERN MISSOURI LIFTS NORTHEAST INTO SOUTHEAST CANADA BY THE  
START OF THE WEEKEND. AN ASSOCIATED COLD FRONT QUICKLY APPROACHING  
THE REGION FROM THE NORTHWEST ON FRIDAY WILL PASS THROUGH THE  
AREA LATE FRIDAY NIGHT INTO EARLY SATURDAY MORNING. ONLY ISOLATED  
LIGHT RAIN SHOWERS ARE EXPECTED ACROSS THE FORECAST AREA FRIDAY  
NIGHT WITH THE PASSAGE OF THE FRONT, FOLLOWED BY ANOTHER DRY  
PERIOD OVER THE WEEKEND. TEMPERATURES WILL CONTINUE TO TREND MUCH  
ABOVE NORMAL ON FRIDAY PRIOR TO THE PASSAGE OF THE COLD FRONT,  
WITH HIGHS OVER THE WEEKEND IN THE MID 60S TO LOWER 70S. /22  
 
MARINE...A BROAD AREA OF SURFACE LOW PRESSURE MOVES INTO THE GULF  
COAST TUESDAY AND BRINGS A PERIOD OF UNSETTLED WEATHER. RAINS  
COULD BE HEAVY...LOWERING VISIBILITY TO A MILE OR LESS AT TIMES  
TUESDAY. THE LOW DROPS SOUTHEAST OVER THE EASTERN GULF AND THE  
FLORIDA PENINSULA WEDNESDAY. A LIGHT TO MODERATE ONSHORE FLOW  
EARLY IN THE PERIOD BECOMES NORTHEAST WEDNESDAY AND THURSDAY. SEAS  
GENERALLY 2 TO 4 FEET. OVER THE WEEKEND...THE PASSAGE OF A STRONG  
COLD FRONT BRINGS AN INCREASE IN NORTHERLY FLOW AND BUILDING SEAS  
IN ITS WAKE. /10  
 

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

 
 

 
 
THIS PRODUCT IS ALSO AVAILABLE ON THE WEB AT:  
HTTP://WEATHER.GOV/MOB  
 
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