053
FXUS64 KMOB 232327
AFDMOB
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOBILE AL
627 PM CDT SAT OCT 23 2021
AVIATION
00Z ISSUANCE...VFR CONDITIONS WILL PREVAIL THROUGH THE PERIOD.
WINDS WILL LIGHT AND VARIABLE THROUGH TONIGHT AT ALL TAF SITES.
GOING INTO SUNDAY MORNING, WINDS WILL THEN BECOME SOUTHEASTERLY
BETWEEN 5-10KTS. JEH/88
PREV DISCUSSION
/ISSUED 332 PM CDT SAT OCT 23 2021/
NEAR TERM UPDATE /NOW THROUGH SUNDAY/...A NEARLY ZONAL FLOW PATTERN
PREVAILS OVER THE REGION WITH THE EXCEPTION OF A MODEST SHORTWAVE
TROF OVER THE NORTHWESTERN GULF/SOUTHERN TEXAS WHICH ADVANCES
SLOWLY TO NEAR THE NORTH CENTRAL GULF COAST ON SUNDAY. THE AXIS OF
A SURFACE RIDGE OVER THE AREA SHIFTS EASTWARD ALLOWING FOR LIGHT
EAST TO NORTHEAST WINDS TO BECOME SOUTHEASTERLY OVER THE WESTERN
PORTION OF THE AREA THIS AFTERNOON, THEN THE REMAINDER OF THE AREA
ON SUNDAY. DRY CONDITIONS ARE EXPECTED THROUGH THE PERIOD WITH
MOSTLY CLEAR SKIES TODAY FOLLOWED BY INCREASING UPPER LEVEL CLOUDINESS
THROUGH SUNDAY IN RESPONSE TO THE MODEST SHORTWAVE TROF. HIGHS
TODAY RANGE FROM AROUND 80 WELL INLAND TO THE LOWER 80S ELSEWHERE,
THEN HIGHS ON SUNDAY WILL BE IN THE LOWER TO MID 80S. LOWS
TONIGHT RANGE FROM THE MID 50S WELL INLAND TO THE MID 60S AT THE
IMMEDIATE COAST. BASED ON BEACH REPORTS AND A MODEST ONSHORE
SWELL, HAVE GONE WITH A MODERATE RISK OF RIP CURRENTS THROUGH
SUNDAY. /29
SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...SUNDAY NIGHT
THROUGH TUESDAY FEATURES A TRANSITION TOWARDS A MORE ACTIVE
WEATHER PATTERN ACROSS THE AREA. A VIGOROUS SHORTWAVE TRAVERSES
THE CENTRAL PLAINS INTO THE OHIO/TENNESSEE VALLEYS SUNDAY NIGHT
INTO MONDAY BEFORE EVENTUALLY EXITING THE EASTERN U.S. COASTLINE
TUESDAY AFTERNOON. WE REMAIN IN RATHER NEBULOUS FLOW AHEAD OF THIS
SHORTWAVE, BUT QUICKLY TRANSITION TO UPPER LEVEL RIDGING BUILDING
IN ITS WAKE MONDAY INTO TUESDAY AS THE PATTERN AMPLIFIES IN
ADVANCE OF THE NEXT DEEPENING UPPER LEVEL TROUGH OVER THE WESTERN
CONUS. AT THE SURFACE, A SUB- 1000MB SURFACE LOW WILL MOVE ACROSS
THE SOUTHERN GREAT LAKES REGION, WITH A COLD FRONT DRAPED TO ITS
SOUTHWEST THROUGH EASTERN TEXAS. THIS WILL QUICKLY PUSH EAST
LIKELY PUSH THROUGH THE CWA OVERNIGHT MONDAY INTO TUESDAY MORNING
WITH TRANSIENT SURFACE HIGH PRESSURE IN ITS WAKE.
THE MAIN FEATURE OF THE PERIOD WILL BE THE COLD FRONT THAT WILL
COME THROUGH MONDAY NIGHT INTO TUESDAY. AHEAD OF THIS SYSTEM
SURFACE SOUTHEASTERLIES BRING IN A MODESTLY MOIST AND UNSTABLE
AIRMASS BEGINNING MONDAY MORNING, WHICH AT LEAST WILL SERVE TO
BOOST ISOLATED TO PERHAPS SCATTERED SHOWER AND THUNDERSTORM
ACTIVITY MONDAY MORNING INTO EVENING. WITH LOSS OF DAYTIME
HEATING AND GIVEN THE LIMITED AIRMASS RETURN, EXPECT A CUTOFF IN
PRECIP CHANCES AFTER SUNSET. A MOSTLY DRY FRONTAL PASSAGE SHOULD
OCCUR MONDAY NIGHT INTO TUESDAY MORNING. IN ITS WAKE, A MUCH DRIER
AIRMASS MOVES IN BRINGING US MIDDLE TO UPPER 50'S DEWPOINTS ONCE
AGAIN. WITH THIS SAID, THE WARMEST NIGHT WILL BE SUNDAY NIGHT
WHERE TEMPERATURES WILL GENERALLY BOTTOM OUT IN THE MIDDLE TO
UPPER 60'S, WARMEST NEARER THE COAST. IN THE WAKE OF THE FRONT
MONDAY AND TUESDAY NIGHTS, MIDDLE TO UPPER 50'S CAN BE EXPECTED
OVER INTERIOR SOUTHEASTERN MS AND INTERIOR SOUTHWESTERN AL, WITH
LOWER TO MIDDLE 60'S ELSEWHERE. MM/25
EXTENDED TERM /WEDNESDAY THROUGH SATURDAY/...A COMPLEX SCENARIO
UNFOLDS THROUGHOUT THE EXTENDED PERIOD AS A HIGHLY AMPLIFIED
PATTERN EVOLVES. UPPER LEVEL RIDGING WEDNESDAY PUSHES RAPIDLY EAST
AS A POTENT UPPER LEVEL TROUGH DIGS AND GRADUALLY TAKES ON A
NEGATIVE TILT AS IT PUSHES ACROSS THE CENTRAL PLAINS STATES
WEDNESDAY INTO THURSDAY. THIS TROUGH SETS UP SHOP OVER THE EASTERN
CONUS THROUGH SATURDAY. AS THE TROUGH APPROACHES, ANOTHER RATHER
INTRIGUING FEATURE ENTERS THE STAGE WITH AN UPPER LEVEL SHORTWAVE
EMBEDDED WITHIN THE SOUTHERN STREAM JET THAT TRACKS NORTHEAST
ACROSS MEXICO INTO THE GULF COAST STATES TUESDAY NIGHT INTO
WEDNESDAY, WHICH JUST SO HAPPENS TO BE THE REMNANT UPPER LEVEL
FEATURE OF HURRICANE RICK FROM THE EASTERN PACIFIC. MODELS VARY ON
EXACT TIMING OF THE UPPER LEVEL TROUGH AND HOW AMPLIFIED IT IS,
AS WELL AS THE EXTENT OF RICKS REMNANTS AND HOW THEY EVOLVE ACROSS
THE AREA. THE TREND OVER THE PAST 24 HOURS OR SO HAS BEEN FOR
THESE FEATURES TO PROGRESS EASTWARD AT A SLIGHTLY SLOWER PACE,
AND THE FORECAST IN GENERAL WAS ADJUSTED TO REFLECT THAT.
AT THE SURFACE, TRANSIENT HIGH PRESSURE TUESDAY NIGHT BEGINS TO
GIVE WAY TO AN APPROACHING SURFACE COLD FRONT FROM THE WEST.
SIMILAR TO THE TIMING ISSUES WITH THE UPPER LEVELS, THE SURFACE
EVOLUTION HAS SIMILAR CAVEATS. HAVE OPTED TO GO WITH A SLIGHTLY
SLOWER SOLUTION GIVEN MODEL TRENDS, AND EXPECT THE COLD FRONT TO
PASS THROUGH THE AREA LATE WEDNESDAY INTO WEDNESDAY NIGHT. IT IS
POSSIBLE THAT THIS TREND CONTINUES, BUT THAT WILL HAVE TO BE
MONITORED THE NEXT FEW DAYS AND FORECASTS ADJUSTED AS NEEDED. IN
ADVANCE OF THE COLD FRONT, THERE IS THE POSSIBILITY OF SEVERE
WEATHER STARTING AS EARLY AS WEDNESDAY MORNING. THERE ARE TWO
DISTINCT FEATURES SUPPORTING POTENTIAL SEVERE WEATHER. THE FIRST
WHICH IS OF LOW CONFIDENCE COINCIDES WITH THE LEAD SHORTWAVE
MENTIONED ABOVE FROM THE SOUTHERN STREAM. A FAVORABLE DYNAMIC
ENVIRONMENT MAY EXIST WITH THIS FEATURE. DEPENDING ON QUALITY OF
LOW LEVEL MOISTURE RETURN AND DEGREE OF INSTABILITY, A SEVERE
THREAT COULD EVOLVE. WITH THAT SAID, MODELS ARE RATHER DIVERSE IN
THIS EVOLUTION, WITH THE GFS AND ITS ENSEMBLES MORE KEEN ON A
STRONGER SHORTWAVE FURTHER EAST VERSUS THE EURO WHICH IS A BIT
MORE TRANSIENT AND FURTHER WEST. FOR NOW, IT'S WORTH MENTIONING AS
A POSSIBLE SCENARIO GIVEN THE GFS/GEFS PERSISTENCE ON IT. THE
NEXT FEATURE OF MODERATE CONFIDENCE FOR SEVERE WEATHER WILL BE
THE UPPER LEVEL TROUGH AND ASSOCIATED SURFACE LOW AND COLD FRONT.
A FAVORABLE DYNAMIC ENVIRONMENT WILL EXIST, BUT DIFFERENCES IN THE
EVOLUTION OF THE TROUGH AND LIKEWISE SURFACE LOW/COLD FRONT WILL
DETERMINE MAGNITUDE OF THE SEVERE THREAT. QUESTIONS ON QUALITY OF
LOW LEVEL MOISTURE RETURN AND RESULTING THERMODYNAMIC PROFILES
ALSO EXIST AND WILL HOPEFULLY BECOME CLEARER AS WE MOVE FORWARD
THE NEXT 24 TO 48 HOURS. FOR NOW, A THREAT FOR SEVERE WEATHER
EXISTS WEDNESDAY INTO WEDNESDAY NIGHT, AND IS HIGHLIGHTED BY THE
STORM PREDICTION CENTER. FOR THE WEDNESDAY INTO THURSDAY PERIOD,
EXPECT SCATTERED TO AT TIMES NUMEROUS SHOWERS AND THUNDERSTORMS,
SOME OF WHICH MAY BE STRONG TO SEVERE WEDNESDAY INTO WEDNESDAY
NIGHT. DRY WEATHER PREVAILS IN THE WAKE OF THE FRONT THURSDAY
AFTERNOON/EVENING THROUGH SATURDAY.
IN THE WAKE OF THE FRONT, STRONG SURFACE WINDS WILL EXIST OVER THE
LAND AND MARINE ZONES. A TIGHT PRESSURE GRADIENT SOUTH OF THE
OCCLUDING SURFACE LOW WITH HIGH PRESSURE BUILDING IN ITS WAKE WILL
SUPPORT SURFACE WINDS OF 10 TO 20MPH OVER LAND GUSTING UPWARDS OF
30MPH. OFFSHORE, THESE WINDS WILL BE MUCH HIGHER WITH 20 TO 30MPH
GUSTING TO NEAR GALE FORCE POSSIBLE. EXPECT AN OVERALL DRY
FORECAST THROUGH SATURDAY WITH MUCH COOLER TEMPERATURES. WE WILL
GO FROM SEEING HIGHS IN THE UPPER 70'S WEDNESDAY TO LOWER TO
MIDDLE 60'S BY FRIDAY AND SATURDAY. SIMILARLY, LOWS WILL GO FROM
LOWER TO MIDDLE 60'S WEDNESDAY NIGHT TO UPPER 40'S AND LOWER 50'S
BY FRIDAY NIGHT. MM/25
MARINE...A SMALL CRAFT ADVISORY WILL LIKELY BE REQUIRED BEGINNING
WEDNESDAY AND CONTINUING THROUGH AT LEAST THURSDAY NIGHT AS A STRONG
COLD FRONT MOVES THROUGH THE AREA. GUSTS TO GALE FORCE ARE
POSSIBLE. NO OTHER HAZARDS ARE SEEN THROUGH THURSDAY NIGHT EXCEPT
FOR WINDS AND SEAS HIGHER NEAR STORMS. /29
MOB WATCHES/WARNINGS/ADVISORIES
AL...NONE.
FL...NONE.
MS...NONE.
GM...NONE.
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