509  
FXUS64 KMOB 270141 AAA  
AFDMOB  
 
AREA FORECAST DISCUSSION...UPDATED  
NATIONAL WEATHER SERVICE MOBILE AL  
841 PM CDT SUN MAR 26 2017  
   
DISCUSSION
 
SEE UPDATED INFORMATION FOR LAND AREAS BELOW.  
 

 
   
UPDATE
 
EARLY THIS EVENING OUR REGION IS BEING AFFECTED BY A  
DEEP SOUTHERLY SURFACE FETCH THAT IS THE RETURN FLOW AROUND AN  
APPROXIMATE 1026 HPA SURFACE ANTICYCLONE LOCATED JUST EAST OF THE  
NC OUTER BANKS. GOES-R FOG PRODUCT WONDERFULLY SHOWING DEVELOPING  
LOW STRATUS ALREADY FORMING MAINLY ALONG AND SOUTH OF THE I-10.  
CURRENT FORECAST HAS IT CLOUDING OVER OVERNIGHT - SO THAT IS ONE  
TRACK WITH PATCH FOG BECOMING AREAS OF FOG LATER TONIGHT. FORECAST  
LOWS IN THE LOW TO MID 60S ALSO LOOKS ON TRACK.  
 
NEXT MAIN FOCUS FOR OUR REGION WILL BE ON TOMORROW AFTERNOON'S  
THUNDERSTORMS, SOME POSSIBLE CONTAINING LARGE HAIL AND DAMAGING  
STRAIGHT LINE WINDS, MAINLY NORTH OF THE HIGHWAY 84 CORRIDOR (AND  
WEST OF I-65). THE MAIN MID- AND UPPER WAVE (CURRENTLY ASSOCIATED  
WITH THE SEVERE THUNDERSTORMS OVER THE SOUTHERN PLAINS) WILL PASS  
FAIRLY FAR TO OUR NORTH AND ALSO FILL SOMEWHAT ON ITS TRACK FROM  
THE PLAINS, ACROSS MO AND INTO THE WESTERN OH VLY. AS IT CURRENTLY  
STANDS WE ARE ONLY FORECASTING ISOLATED TO SCATTERED THUNDERSTORM  
COVERAGE GIVEN THE MORE NORTHERLY TRACK OF THE AFOREMENTIONED  
FEATURE. WAYNE, CHOCTAW, CLARKE AND WILCOX COUNTIES ARE EXPECTED  
TO RECEIVE THE GREATEST COVERAGE. THERE IS A SIGNIFICANT THERMAL  
COLD POOL ADVECTING BY AS THE WAVE PASSES TO OUR N (-14 TO  
-16 DEG(C) FORECAST AT 500 HPA) AND LOW WET BULB ZERO HGTS (CLOSE  
TO 8-9 KFT). THUS ANY STORMS THAT FORM WOULD LIKELY STAND A GOOD  
CHANCE OF LOCALLY DAMAGING WINDS AND SEVERE HAIL (>1" THAN  
DIAMETER) FOR A BRIEF PERIOD TOMORROW AFTERNOON. MITIGATING  
FACTORS FOR THIS EVENT WOULD BE RELATIVELY LOWER VALUES OF  
ABSOLUTE MOISTURE THAN WHAT WE NORMALLY SEE. THIS WOULD LIMIT THE  
AMOUNT OF THERMODYNAMIC INSTABILITY AND THUS FURTHER LIMIT  
THUNDERSTORM COVERAGE AND INTENSITY (SO, CONSIDERING THE  
PROS/CONS, WE ARE LOOKING FOR ABOUT 800-1100 J/KG OF MLCAPE -  
WHICH WOULD STILL CAUSE CONCERN). 40 KT OF BULK 0-6 KM VWS WILL  
ALSO EXIST TOMORROW AFTERNOON (USING CHOCTAW CO, AL AS A PROXY)  
WHICH WILL HELP TO ORGANIZE NEWLY DEVELOPING UPDRAFTS BUT THIS  
WILL BE OFFSET SOMEWHAT BY RELATIVELY WEAKER LOW-LEVEL SR INFLOW  
WHICH WOULD STIFLE THE INTENSITY OF NEWER AND SUBSEQUENT UPDRAFT  
GROWTH.  
 
SUMMARIZING, THERE IS RELATIVELY HIGH FORECAST CONFIDENCE THE  
MID- AND UPPER WAVE WILL TRACK MORE TO OUR N AND THIS WOULD ACT TO  
LIMIT THE AMOUNT OF THUNDERSTORM ACTIVITY (SO WE CONCUR WITH  
WHERE SPC HAS PLACED THE SOUTHERNMOST LIMIT OF THE MRGNL RISK ON  
THEIR LATEST DAY 2 OUTLOOK). THE THUNDERSTORMS ARE FORECAST TO  
END DURING THE 6-9 PM TIME FRAME ALTOGETHER AND WE WILL BE DEALING  
WITH PATCHY DENSE FOG AGAIN TOMORROW NIGHT REGIONWIDE.  
 
REGARDING RIP CURRENTS, WE CLOSELY ANALYZED EVERYTHING THIS  
AFTERNOON AND HAVE DECIDED, ONCE AGAIN LIKE YESTERDAY, TO EXTEND  
THE 'HIGH' RISK OF RIP CURRENTS THROUGH LATE MONDAY (DESPITE  
COMING INTO A NEAP CYCLE). AREA BEACHES WERE ALSO CONTINUING TO  
FLY RED FLAGS THIS AFTERNOON. THE WAVE PERIOD IS STILL RELATIVELY  
HIGH (7 SEC) WITH HIGHER VALUES TO THE SOUTH AND THE WIND FETCH  
IS STILL CAUSING WAVE ENERGY TO DISPERSE NORTHWARD FROM THE  
CENTRAL AND SOUTHERN GLFMEX. IT IS JUST GOING TO TAKE A WHILE FOR  
THE SWELL TO SUBSIDE. SYNOPTICALLY THE PATTERN IS NON-CHANGING, SO  
THIS IS WHAT YOU WOULD EXPECT UNTIL SOMETHING DOES INDEED CHANGE.  
HAVE ALL IDEAS THAT BY TOMORROW AFTERNOON WE WILL BE IN A BETTER  
PLACE. /23 JMM  
 

 
   
PREV DISCUSSION
 
/ISSUED 643 PM CDT SUN MAR 26 2017/  
 
DISCUSSION...UPDATED FOR LATEST AVIATION DISCUSSION BELOW.  
 
AVIATION...  
00Z ISSUANCE...PATCHY DENSE FOG AND LOW CLOUDS DEVELOP LATE  
TONIGHT INTO EARLY SUNDAY MORNING, PARTICULARLY DURING THE PRE-  
DAWN HOURS, WITH CIGS/VIS DIPPING TO IFR/LIFR LEVELS. SCATTERED  
TO BROKEN CU FIELD WITH VFR (TO POTENTIALLY MVFR NEAR THE COAST)  
CIGS DEVELOPS MONDAY AFTERNOON AND EVENING, WITH SCATTERED SHRA  
NEAR THE COAST AND TSRA ACROSS THE INTERIOR. GUSTY WINDS, HEAVY  
DOWNPOURS, AND LARGE HAIL POSSIBLE IN THE STRONGEST STORMS. /49  
 
PREV DISCUSSION... /ISSUED 348 PM CDT SUN MAR 26 2017/  
 
NEAR TERM /NOW THROUGH MONDAY/...PERSISTENT LIGHT SOUTHERLY FLOW  
ON THE WESTERN PERIPHERY OF A SURFACE HIGH POSITIONED OFF THE  
MID- ATLANTIC COAST MAINTAINS A FAIRLY STEADY STATE SURFACE  
DEWPOINT PROFILE IN THE LOWER TO MID 60S OVERNIGHT. SURFACE BASED  
MOISTURE AND WIND DIRECTION FAVORS THE DEVELOPMENT OF LATE NIGHT  
FOG. THIS IS SUPPORTED BY THE LATEST RAP/HRRR AND SHORT RANGE  
ENSEMBLES. FOG COULD BECOME LOCALLY DENSE IN SPOTS. OVERNIGHT LOWS  
MILD, RANGING IN THE LOWER TO MID 60S.  
 
NEXT UPPER LEVEL STORM SYSTEM, EJECTING OUT OF THE PLAINS STATES  
ACROSS THE LOWER MS RIVER VALLEY MONDAY MORNING, MAKES STEADY  
EASTWARD PROGRESSION ACROSS THE TN RIVER VALLEY THRU THE DAY. THIS  
FEATURE ALLOWS A FRONTAL BOUNDARY TO APPROACH THE MID-SOUTH BY  
MONDAY AFTERNOON. EAST OF THE LARGER SCALE DYNAMICS AND SURFACE  
FRONT, PRECIPITABLE WATER VALUES HOLD NEAR AN INCH. CONSIDERING  
PASSAGE OF MODEST DEEP LAYER ASCENT AND SUFFICIENT DAILY  
INSTABILITY, A RETURN CHANCE OF SHOWERS AND STORMS REMAINS IN THE  
FORECAST MONDAY. THE STORM PREDICTION CENTER PLACES A BETTER  
CHANCE (SLIGHT RISK OF SEVERE WEATHER) TO OUR NORTH FROM THE TN  
RIVER VALLEY, SOUTHWARD TO NORTHERN MS/NORTHERN AL ON MONDAY.  
HOWEVER, WITH AMOUNT OF INSTABILITY AND WET-BULB ZERO HEIGHTS DOWN  
TO 8 TO 9 KFT, CANNOT RULE OUT SOME STRONG TO A FEW SEVERE STORMS  
CONTAINING MARGINALLY SEVERE HAIL (QUARTER SIZE OR SO) AND  
LOCALIZED DAMAGING WIND GUSTS, MAINLY OVER THE NORTHWEST HALF OF  
ZONES. IT IS THESE ZONES THAT ARE WITHIN A MARGINAL RISK OF SEVERE  
WEATHER THAT EXTENDS SOUTH OF THE SLIGHT RISK AREA, WITH AN AREA  
DEFINED ALONG AND WEST OF A LINE FROM THOMASVILLE AL TO RICHTON  
MS. DAYTIME HIGHS MONDAY LOWER TO MID 80S INTERIOR TO MID TO UPPER  
70S BEACHES. /10  
 
SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...THE UPPER  
LEVEL TROUGH OVER THE SOUTHEAST CONUS WILL SHIFT EASTWARD AND  
WEAKEN BEFORE MOVING OVER THE WESTERN ATLANTIC BY LATE TUESDAY  
AFTERNOON. MEANWHILE AN UPPER LEVEL RIDGE OVER THE SOUTHERN  
PLAINS WILL MOVE EAST AND BUILD NORTHWARD, WITH THE CENTRAL AXIS  
MOVING OVER THE REGION. THIS UPPER LEVEL RIDGE WILL EXTEND FROM  
THE SOUTHEASTERN GULF OF MEXICO TO SOUTH CENTRAL CANADA BY TUESDAY  
EVENING AND SHIFT EASTWARD THROUGH MIDWEEK, WHILE A LARGE UPPER  
LEVEL TROUGH EXITING THE ROCKY MOUNTAINS MOVES OVER THE GREAT  
PLAINS. THE SURFACE HIGH PRESSURE RIDGE ACROSS THE SOUTHEASTERN  
STATES AND EASTERN GULF WILL REMAIN LARGELY INTACT AS A SURFACE  
LOW ACROSS THE OHIO RIVER VALLEY REGION MOVES EAST AND WEAKENS.  
A WEAK COLD FRONT ASSOCIATED WITH THE SURFACE LOW WILL APPROACH  
THE REGION FROM THE NORTHWEST JUST REACHING THE NORTHERN PORTION  
OF THE FORECAST AREA AND STALL. OTHER THEN A FEW ISOLATED SHOWERS  
ACROSS OUR FAR NORTHERN ZONES MONDAY NIGHT NEAR THE FRONT AND  
ISOLATED DEVELOPMENT ON TUESDAY NORTH OF I-10, IT WILL BE DRY  
THROUGH MIDWEEK.  
 
LOW TEMPERATURES EACH NIGHT WILL RANGE FROM 58 TO 62 DEGREES  
INLAND AREAS, WITH MID 60S ALONG THE BEACHES. WARM TEMPERATURES  
WILL CONTINUE ON TUESDAY AND WEDNESDAY WITH HIGHS RANGING FROM 80  
TO 85 DEGREES INLAND AREAS, WITH MID TO UPPER 70S ALONG THE  
COASTAL SECTIONS. /22  
 
LONG TERM /THURSDAY THROUGH SUNDAY/...THE LARGE UPPER LEVEL  
TROUGH OVER THE GREAT PLAINS WILL SHIFT EASTWARD, WITH AN  
EMBEDDED UPPER LOW PRESSURE AREA WITHIN THE TROUGH OVER THE  
EASTERN PORTIONS OF KANSAS AND OKLAHOMA LIFTING NORTHEAST. THE  
SOUTHERN EXTENT OF THE UPPER TROUGH WILL SWING EASTWARD ACROSS  
THE DEEP SOUTH. THE SURFACE HIGH PRESSURE RIDGE ACROSS THE  
SOUTHEASTERN STATES AND EASTERN GULF WILL MOVE EASTWARD AS A  
SURFACE LOW FORMING ACROSS THE SOUTHERN PLAINS LIFTS NORTHEAST TO  
THE GREAT LAKES REGION. A WEAK COLD FRONT ASSOCIATED WITH THE  
SURFACE LOW WILL APPROACH THE FORECAST AREA FROM THE WEST THURSDAY  
NIGHT. SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS WILL  
ACCOMPANY THIS NEXT SYSTEM ON THURSDAY AND THURSDAY NIGHT, WITH  
THE POTENTIAL OF STRONG TO SEVERE THUNDERSTORMS. THE PRECIPITATION  
WILL THEN TAPER OFF FROM WEST TO EAST ON FRIDAY IN THE WAKE OF  
THE FRONT FOLLOWED BY HIGH PRESSURE BUILDING IN FROM THE WEST.  
ABOVE NORMAL TEMPERATURES WILL CONTINUE THROUGH THE LONG TERM. /22  
 
MARINE...HIGH PRESSURE OFF THE MID-ATLANTIC COAST MONDAY AND  
TUESDAY SINKS SOUTHWARD TO THE NORTHERN BAHAMAS ON WEDNESDAY. A  
GENERAL LIGHT ONSHORE FLOW PERSISTS FOR THE NEXT SEVERAL DAYS.  
ONSHORE FLOW STRENGTHENS AND SEAS BUILD ON THURSDAY IN RESPONSE  
TO A STRONG LOW PRESSURE SYSTEM LIFTING UP ACROSS THE MID MS RIVER  
VALLEY AND ASSOCIATED FRONTAL BOUNDARY APPROACHING FROM THE WEST.  
CHANCES OF STORMS INCREASE THURSDAY AND THURSDAY NIGHT, SOME OF  
WHICH COULD BECOME STRONG. /10  
 

 
   
MOB WATCHES/WARNINGS/ADVISORIES
 
 
AL...HIGH RIP CURRENT RISK THROUGH MONDAY EVENING FOR ALZ265-266.  
 
FL...HIGH RIP CURRENT RISK THROUGH MONDAY EVENING FOR FLZ202-204-206.  
 
MS...NONE.  
GM...NONE.  

 
 

 
 
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