517  
FXUS64 KMOB 261130 AAA  
AFDMOB  
 
AREA FORECAST DISCUSSION...UPDATED  
NATIONAL WEATHER SERVICE MOBILE AL  
630 AM CDT WED APR 26 2017  
   
DISCUSSION
 
UPDATED FOR LATEST AVIATION DISCUSSION BELOW.  
 

 
   
AVIATION
 
 
12Z ISSUANCE...VFR CONDITIONS WILL PREVAIL THROUGH MUCH OF THE  
PERIOD, WITH MVFR CIGS EXPECTED TO DEVELOP DURING THE LATE  
AFTERNOON. SOUTHERLY WINDS WILL INCREASE WITH GUSTS TO AROUND 20  
KNOTS BY THIS AFTERNOON. RAIN CHANCES INCREASE LATE IN THE PERIOD  
AS A COLD FRONT APPROACHES FROM THE WEST. /13  
 

 
   
PREV DISCUSSION
 
/ISSUED 445 AM CDT WED APR 26 2017/  
 
NEAR TERM /NOW THROUGH THURSDAY/...A DRY AND STABLE AIRMASS WILL  
REMAIN OVER THE AREA TODAY AS UPPER AND SFC RIDGING REMAIN  
INTACT. MEANWHILE, AN UPPER TROUGH WILL DIG ACROSS THE CENTRAL  
PLAINS AND BECOME NEGATIVELY TILTED AS IT EJECTS NORTHEAST THROUGH  
THE AFTERNOON AND EVENING HOURS. AHEAD OF THE TROUGH, A SFC LOW  
WILL MOVE FROM THE ARKLATEX TO THE OHIO VALLEY BY THIS EVENING  
WITH A TRAILING COLD FRONT APPROACHING THE MISSISSIPPI RIVER BY  
00Z THIS EVENING. A LINE OF SHOWERS AND THUNDERSTORMS IS EXPECTED  
TO BE ONGOING ALONG THE FRONT AS IT MOVES EASTWARD OVERNIGHT AND  
INTO THE THE WESTERN PORTIONS OF OUR AREA AROUND MIDNIGHT. THE  
FRONT WILL MOVE EAST OF THE AREA BY LATE MORNING ON THURSDAY AS IT  
BEGINS TO STALL OUT. PARAMETERS ARE MOST FAVORABLE FOR A FEW  
STRONG TO SEVERE STORMS BETWEEN 06-09Z ACROSS PRIMARILY  
NORTHWESTERN AREAS.  
 
THE UPPER DYNAMICS WILL RAPIDLY PULL NORTHEAST AWAY FROM THE AREA  
OVERNIGHT. THIS WILL LEAD TO A WEAKENING TREND IN CONVECTION AS IT  
MOVES ACROSS. DAMAGING WINDS WILL BE THE PRIMARY THREAT AS THE  
PRIMARY CONVECTIVE MODE IS EXPECTED TO REMAIN LINEAR. THE STRONGER  
CORES MAY ALSO PRODUCE SOME LARGE HAIL. SHOWERS AND THUNDERSTORMS  
WILL CONTINUE EAST THROUGH THE DAY ON THURSDAY AND LIKELY LINGER  
ACROSS EASTERN ZONES THURSDAY AFTERNOON AS THE FRONT BEGINS TO  
STALL. THE SEVERE THREAT IS EXPECTED TO CONTINUE TO DECREASE AS  
THE DYNAMICS PULL AWAY WITH JUST A MARGINAL RISK CONTINUING. HIGHS  
ARE EXPECTED TO BE IN THE LOW TO MID 80S AWAY FROM THE COAST WITH  
UPPER 70S ALONG THE COAST. LOWS TONIGHT WILL FALL INTO THE LOW  
60S ACROSS NORTHWEST AREAS TO LOW 70S ALONG THE COAST. /13  
 
SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...A SOUTHWESTERLY  
FLOW PATTERN ALOFT WILL PREVAIL ACROSS OUR FORECAST AREA DURING  
THE THURSDAY NIGHT THROUGH FRIDAY NIGHT TIME FRAME BETWEEN AN  
UPPER LEVEL RIDGE OF HIGH PRESSURE BUILDING OVER THE FL PENINSULA  
AND ADJACENT WESTERN ATLANTIC OCEAN AND THE NEXT BROAD UPPER  
LEVEL TROUGH THAT WILL BE DEEPENING OVER THE WESTERN CONUS.  
SOUTHERLY LOW LEVEL FLOW WILL RETURN TO THE REGION THURSDAY NIGHT  
AND CONTINUE THROUGH FRIDAY NIGHT BETWEEN THE SURFACE RIDGE OVER  
THE WESTERN ATLANTIC AND THE NEXT DEEPENING LOW PRESSURE SYSTEM  
OVER THE PLAINS STATES. LOW LEVEL WARM ADVECTION SHOULD ALLOW  
SURFACE DEWPOINTS TO RISE INTO THE UPPER 60S TO LOWER 70S THROUGH  
FRIDAY NIGHT. THERE ALSO COULD BE ISOLATED SHOWERS AND  
THUNDERSTORMS DEVELOP IN THE WARM ADVECTION REGIME THURSDAY NIGHT  
INTO FRIDAY, BUT CONFIDENCE IN MEASURABLE PRECIPITATION AND  
EXPECTANCE OF LOW COVERAGE WAS ENOUGH TO KEEP POPS BELOW 20% WITH  
THIS FORECAST. LATER SHIFTS MAY NEED TO REVISIT AND ADD AT LEAST  
SOME ISOLATED CONVECTIVE MENTION EITHER THURSDAY NIGHT INTO  
FRIDAY IF LATER MODEL TRENDS LEND GREATER CONFIDENCE. LOWS  
THURSDAY NIGHT WILL RANGE FROM THE MID 60S TO AROUND 70 INLAND TO  
THE LOWER 70S NEAR THE COAST. HIGHS FRIDAY SHOULD WARM INTO THE  
MID TO UPPER 80S INLAND, AND POTENTIALLY AROUND 90 OVER A FEW  
SPOTS. READINGS NEAR THE COAST SHOULD RANGE IN THE UPPER 70S TO  
LOWER 80S. LOWS FRIDAY NIGHT WILL TREND A LITTLE WARMER WITH  
READINGS AROUND 70 TO THE LOWER 70S ACROSS THE REGION. /21  
 
LONG TERM /SATURDAY THROUGH TUESDAY/...THE NEXT DEEP UPPER LEVEL  
TROUGH WILL MOVE ACROSS THE CENTRAL AND SOUTHERN PLAINS STATES  
SATURDAY, BEFORE LIFTING TOWARD THE UPPER MIDWEST SUNDAY NIGHT  
INTO EARLY MONDAY. AN ASSOCIATED SURFACE COLD FRONT WILL ADVANCE  
EASTWARD TOWARD THE MISSISSIPPI RIVER VALLEY SUNDAY, THEN ACROSS  
OUR FORECAST AREA LATE SUNDAY NIGHT INTO MONDAY MORNING. ENHANCED  
DEEP LAYER MOISTURE AND SYNOPTIC SCALE LIFT ALONG THE FRONTAL ZONE  
WILL FAVOR AN ORGANIZED COMPLEX/LINE OF SHOWERS AND THUNDERSTORMS  
SPREADING EASTWARD FROM THE MISSISSIPPI VALLEY SUNDAY MORNING TO  
THE CENTRAL GULF COAST REGION LATE SUNDAY AFTERNOON INTO LATE  
SUNDAY NIGHT/EARLY MONDAY MORNING. THERE ARE STILL SOME TIMING  
DIFFERENCES NOTED, BUT TRENDS CURRENTLY FAVOR SHOWERS AND  
THUNDERSTORMS IMPACTING OUR SOUTHEAST MS AND INTERIOR SOUTHWEST AL  
COUNTIES EITHER LATE SUNDAY MORNING OR EARLY SUNDAY AFTERNOON,  
WITH CONVECTION SLOWLY SPREADING EASTWARD ACROSS THE FORECAST AREA  
THROUGH SUNDAY EVENING/NIGHT, BEFORE GRADUALLY CLEARING OUR  
EASTERN ZONES BY LATE MONDAY MORNING. THERE ARE INDICATIONS OF A  
RATHER STRONG LOW LEVEL JET DEVELOPING ACROSS OUR FORECAST AREA  
AHEAD OF THE LINE, POTENTIALLY AS STRONG AS AROUND 40-55 KNOTS  
(STRONGER TOWARD SOUTHEAST MS AND INTERIOR SOUTHWEST AL) SUNDAY  
MORNING INTO EARLY SUNDAY AFTERNOON. THE STRONG LLJ IN CONJUNCTION  
WITH FAVORABLE DEEP LAYER SHEAR, GOOD INSTABILITY WITH MLCAPE  
VALUES BETWEEN 1000-1500 J/KG, AND 0-1KM STORM RELATIVE HELICITY  
VALUES BETWEEN 150-250 M2/S2 ON AVERAGE WILL FAVOR POTENTIAL FOR  
EMBEDDED SEVERE STORMS MOVING ACROSS THE REGION SUNDAY INTO SUNDAY  
NIGHT, WITH ALL SEVERE MODES POSSIBLE. VERY HEAVY RAINFALL MAY  
ALSO ACCOMPANY THE LINE, WITH POTENTIAL OF AT LEAST 1-3 INCHES OF  
RAIN WITH LOCALLY HIGHER AMOUNTS. A DRIER ZONAL FLOW RETURNS  
MONDAY AFTERNOON INTO TUESDAY IN THE WAKE OF THE DEPARTING SYSTEM.  
/21  
 
MARINE...SOUTHERLY WINDS AND SEAS WILL BUILD LATE TODAY IN  
RESPONSE TO AN APPROACHING COLD FRONT. SHOWERS AND THUNDERSTORMS  
WILL MOVE ACROSS THE MARINE AREA TONIGHT INTO EARLY THURSDAY.  
WINDS AND SEAS WILL REBUILD LATE IN THE WEEK INTO THE WEEKEND AS A  
STRONGER COLD FRONT APPROACHES FROM THE WEST. /13  
 

 
   
MOB WATCHES/WARNINGS/ADVISORIES
 
 
AL...HIGH RIP CURRENT RISK THROUGH THURSDAY MORNING FOR ALZ265-266.  
 
FL...HIGH RIP CURRENT RISK THROUGH THURSDAY MORNING FOR FLZ202-204-  
206.  
 
MS...NONE.  
GM...SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 7 AM CDT  
THURSDAY FOR GMZ631-632-650-655-670-675.  
 

 
 

 
 
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