835  
FXUS64 KMOB 201727 AAA  
AFDMOB  
 
AREA FORECAST DISCUSSION...UPDATED  
NATIONAL WEATHER SERVICE MOBILE AL  
1227 PM CDT FRI APR 20 2018  
   
DISCUSSION
 
SEE UPDATED INFORMATION FOR LAND AREAS AND AVIATION  
DISCUSSION BELOW.  
 

 
   
UPDATE
 
THE CURRENT FORECAST IS ON TRACK AND NO CHANGES ARE  
NEEDED. /13  
 

 
   
AVIATION
 
 
18Z ISSUANCE...VFR CONDITIONS WILL PREVAIL THROUGH THE NEXT 24  
HOURS. /13  
 

 
   
PREV DISCUSSION
 
/ISSUED 653 AM CDT FRI APR 20 2018/  
 
DISCUSSION...SEE UPDATED INFORMATION FOR MARINE AREAS AND AVIATION  
DISCUSSION BELOW.  
 
MARINE...UPDATED THE COASTAL WATERS FORECAST THIS MORNING TO  
EXTEND THE SMALL CRAFT ADVISORY FOR A FEW MORE HOURS. ORIGINALLY  
SET TO EXPIRE AT 6 AM, EXTENDED UNTIL 9 AM AS WINDS AT MIDDLE BAY  
LIGHTHOUSE AND BUOY 12 STILL BOTH FREQUENTLY GUSTING TO 18-21  
KNOTS SHORTLY BEFORE 6 AM. DO EXPECT WINDS TO DIMINISH SLIGHTLY  
AFTER 9 AM THIS MORNING, BUT SMALL CRAFT SHOULD CONTINUE TO  
EXERCISE CAUTION THROUGH MOST OF TODAY AS WINDS WILL CONTINUE TO  
OCCASIONALLY GUST TO 15 TO 20 KNOTS. 12/DS  
 
AVIATION...  
20/12Z ISSUANCE...VFR CONDITIONS EXPECTED TO CONTINUE THROUGH THE  
FORECAST PERIOD WITH ONLY SCATTERED MID AND HIGH LEVEL CLOUDS.  
SURFACE WINDS INITIALLY NORTHEASTERLY THIS MORNING, BECOMING MORE  
EAST AND MAYBE EVEN SOUTHEASTERLY NEAR THE COAST LATE TODAY AND  
TONIGHT. 12/DS  
 
PREV DISCUSSION... /ISSUED 423 AM CDT FRI APR 20 2018/  
 
NEAR TERM /NOW THROUGH FRIDAY NIGHT/...THE REINFORCING COLD FRONT THAT  
PASSED THROUGH THE FORECAST AREA YESTERDAY IS NOW WELL TO THE SOUTH  
OVER THE GULF OF MEXICO, WITH COOL AND DRY SURFACE HIGH PRESSURE  
RIDGING INTO THE AREA FROM THE NORTH. THE SURFACE HIGH PRESSURE WILL  
DRIFT EAST THROUGH TONIGHT, WITH A LIGHT TO OCCASIONALLY MODERATE  
NORTHEAST TO EAST WINDFLOW EXPECTED WITH ONLY SLIGHT LOW LEVEL  
MOISTURE RETURN. RIDGING ALOFT IS EXPECTED TO INCREASE FROM THE WEST  
THROUGH TONIGHT, MAINTAINING THE STABLE CONDITIONS OVER THE AREA.  
ONLY SCATTERED AND MAINLY THIN MID TO HIGH LEVEL CLOUDS EXPECTED  
THROUGH THE PERIOD. SHOULD HAVE PLENTY OF SUNSHINE TODAY, BUT HIGH  
TEMPERATURES SHOULD BE SLIGHTLY BELOW NORMAL, GENERALLY IN THE LOW  
TO MID 70S. LOWS TONIGHT A LITTLE BELOW NORMAL AS WELL, ESPECIALLY  
OVER INLAND AREAS WHERE TEMPS SHOULD FALL INTO THE UPPER 40S AND  
LOWER 50S OVERNIGHT. NEAR NORMAL LOW TEMPS TONIGHT CLOSER TO  
THE COAST, WHERE UPPER 50S ARE EXPECTED. 12/DS  
 
SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...SHORT WAVE UPPER  
LEVEL RIDGE AXIS FROM THE GULF, NORTHWARD ACROSS THE TN VALLEY  
SATURDAY MORNING MOVES TO THE SOUTHEAST AS UPPER LEVEL STORM  
SYSTEM OVER THE PLAINS EJECTS EASTWARD. A SLIGHT MODERATION IN  
HIGHS ON SATURDAY. UPPER LEVEL HEIGHT FALLS ASSOCIATED WITH THE  
PLAINS STORM SYSTEM OVERSPREAD THE LOWER MS RIVER VALLEY SATURDAY  
NIGHT, THEN ACROSS THE TN RIVER VALLEY SOUTHWARD TO THE GULF COAST  
SUNDAY MORNING. AT SAME TIME, A WELL ESTABLISHED DIFFLUENT FLOW  
ALOFT MOVES ATOP THE AREA. THIS FAVORS AN INCREASE IN DEEP LAYER  
ASCENT AS A COLD FRONT/ASSOCIATED WAVE OF FRONTAL LOW PRESSURE  
APPROACH FROM THE WEST SUNDAY WITHIN A ZONE OF MUCH IMPROVED DEEP  
LAYER MOISTURE. WEATHER MODELS ARE IN FAIR ALIGNMENT ON THIS  
MORNING'S RUNS, SHOWING COMPLEX FRONTAL LOW POSITIONED FROM AR TO  
WESTERN MS SUNDAY MORNING, TRACKING ONLY VERY SLOWLY EASTWARD  
DURING THE DAY. AHEAD OF THIS FEATURE, DESPITE STRENGTHENING LOW  
LEVEL WIND SHEAR, THERE IS SUBSTANTIAL SPREAD IN THE MODELS ON  
AMOUNT OF BUOYANCY/DAYTIME INSTABILITY THAT WILL BE AVAILABLE  
SUNDAY. THE OPERATIONAL GFS/ECMWF SHOWS 0-1 KM CAPE GENERALLY FROM  
200 TO 400 J/KG WITH THE NAM OUTPUT ON MUCAPE BUILDING ITS VALUES  
FROM 700 TO 1100 J/KG BY LATE IN THE DAY SUNDAY. THE SHORT RANGE  
ENSEMBLES FOR CAPE GREATER THAN 500 J/KG SHOWS A GENERAL 30 TO 60%  
PROBABILITY OF OCCURRENCE OVER THE LOCAL AREA. CONSIDERING THE  
DIFFERENCES MENTIONED, THE RISK OF SEVERE WEATHER IS MARGINAL.  
HIGHEST RAIN CHANCES (CATEGORICAL POPS) MOVE FROM WEST TO EAST  
DURING THE DAY SUNDAY. BEST DEEP LAYER ASCENT BEGINS TO SHIFT EAST  
SUNDAY EVENING WITH SHOWERS LIKELY AND A FEW STORMS OVER THE  
EASTERN ZONES AND A MID RANGE CHANCE WEST. DAYTIME HIGHS ON  
SUNDAY TREND LOWER GIVEN THICKENED CLOUD COVER AND HIGH RAIN  
CHANCES. /10  
 
LONG TERM /MONDAY THROUGH THURSDAY/...FRONTAL PASSAGE OCCURS  
MONDAY MORNING AS SURFACE FRONTAL LOW EASES ACROSS SOUTHEAST AL  
AND SOUTHERN GA. A SMALL CHANCE OF SHOWERS NORTH OF THE COAST  
MONDAY MORNING IN THE WRAP-AROUND MOISTURE ON THE WEST SIDE OF THE  
LOW. THE LOW LIFTS NORTHEAST UP ACROSS THE CAROLINAS ON TUESDAY  
AND QUICKLY UP ACROSS THE DELMARVA ON WEDNESDAY. A SLIGHT CHANCE  
SHOWERS REMAIN IN THE FORECAST OVER THE FAR NORTHERN ZONES TUESDAY  
AS SECONDARY SHORT-WAVE ENERGY ALOFT AT THE BASE OF SOUTHERN  
STATES LONG-WAVE TROF PASSES THROUGH, COMBINED WITH LINGERING  
WRAP AROUND MOISTURE ON THE WEST SIDE OF DEPARTING LOW. NEXT FRONT  
LOOKS TO MAKE PASSAGE LATE WEDNESDAY INTO THURSDAY BRINGING  
ANOTHER SMALL CHANCE OF SHOWERS TO THE LOCAL AREA.  
 
DAILY HIGHS NOT FAR OFF SEASONAL NORMALS. OVERNIGHT LOWS TREND  
CLOSE TO SEASONAL BY THE MIDDLE OF NEXT WEEK. /10  
 
MARINE...A STRONG NORTHEASTERLY WIND FLOW OVER THE MARINE AREA  
EARLY THIS MORNING WILL WEAKEN SLIGHTLY TODAY. A SMALL CRAFT  
ADVISORY IS IN EFFECT UNTIL 6AM THIS MORNING FOR THE GULF MARINE  
ZONES AS WELL AS SOUTHERN MOBILE BAY AND THE MISSISSIPPI SOUND, AND  
MAY HAVE TO BE EXTENDED FOR AT LEAST A FEW MORE HOURS THIS MORNING.  
WILL MONITOR TRENDS AND MAKE THAT CHANGE A LITTLE LATER IN THE SHIFT  
IN NECESSARY. EVEN AFTER THE SCA CONDITIONS SUBSIDE SOMETIME THIS  
MORNING, STILL EXPECT EXERCISE CAUTION CONDITIONS TO PREVAIL OVER  
MOST OF THE MARINE AREA THROUGH MOST OF THE MORNING HOURS TODAY  
(WITH WINDS OF 15 TO 20 KNOTS) BEFORE GRADUALLY DECREASING LATE  
TODAY. A LIGHT TO MODERATE EASTERLY FLOW IS ANTICIPATED FOR TONIGHT,  
BUT GRADUALLY INCREASING SOMEWHAT AGAIN ON SATURDAY AS ANOTHER  
FRONTAL SYSTEM DEVELOPS TO THE WEST OF THE MARINE AREA. A MODERATE  
TO SOMETIMES STRONG SOUTHEAST TO SOUTH FLOW IS EXPECTED SATURDAY  
NIGHT INTO SUNDAY AS THE FRONT APPROACHES. WINDS BECOME WESTERLY IN  
THE WAKE OF THE FRONT BY MONDAY, WITH A LIGHT TO MODERATE WEST TO  
NORTHWEST FLOW THEN CONTINUING INTO THE MIDDLE PART OF MID NEXT  
WEEK. SHOWERS AND THUNDERSTORMS ARE EXPECTED AHEAD AND ALONG THE  
FRONT THIS WEEKEND, WITH THIS BEST COVERAGE OCCURRING SUNDAY AND  
SUNDAY NIGHT. 12/DS  
 

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

 
 

 
 
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