424
FXUS64 KMOB 261146 AAA
AFDMOB
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE MOBILE AL
646 AM CDT WED SEP 26 2018
DISCUSSION
UPDATED FOR LATEST AVIATION DISCUSSION BELOW.
AVIATION
12Z ISSUANCE...THERE IS QUITE A VARIANCE IN CEILINGS ACROSS THE
REGION EARLY THIS MORNING. WHILE MOST LOCATIONS ARE SHOWING
PREDOMINATE VFR CONDITIONS, THERE HAVE BEEN PERIODS OF MVFR OR
EVEN IFR CIGS AT SEVERAL LOCATIONS. AS HEATING COMMENCES THIS
MORNING, EXPECT VFR CONDITIONS TO PREVAIL, HOWEVER PERIODS OF
MVFR CIGS ARE POSSIBLE CLOSER TO THE COAST, PARTICULARLY IN THE
VICINITY OF WHERE SCATTERED SHOWERS AND THUNDERSTORMS DEVELOP.
EXPECT STORMS TO BECOME MORE NUMEROUS THIS AFTERNOON AND PERSIST
INTO THIS EVENING, ESPECIALLY ALONG AND WEST OF I-65. DIFFICULT TO
REFLECT A FIRM BEGIN/END TIME FOR THUNDER GIVEN THE FAVORABLE
CONDITIONS FOR CONVECTIVE DEVELOPMENT. BRIEF IFR CONDITIONS
POSSIBLE IN THE STRONGER STORMS. A CHANCE FOR STORMS WILL CARRY
INTO THE OVERNIGHT HOURS. 34/JFB
PREV DISCUSSION
/ISSUED 504 AM CDT WED SEP 26 2018/
NEAR TERM /NOW THROUGH WEDNESDAY NIGHT/...A LONGWAVE TROUGH MOVING INTO
THE GREAT LAKES TODAY ALONG WITH ANOTHER SHORTWAVE DIVING SOUTHEAST
OUT OF THE INTERMOUNTAIN WEST WILL SERVE TO PUSH A COLD FRONT INTO
THE DEEP SOUTH THROUGH TONIGHT. THE BOUNDARY WILL STALL TO THE NORTH
OF THE AREA, HOWEVER, AS STRONG RIDGING OVER THE SOUTHWEST ATLANTIC
PERSISTS AND SHOWS NO SIGNS OF RETREATING. THIS KEEPS OUR REGION IN
A VERY HUMID AND UNSTABLE AIRMASS. THE GOES-EAST PRECIPITABLE WATER
PRODUCT SHOWS A LARGE AREA OF 2 PLUS INCH VALUES EXTENDING FROM THE
BAY OF CAMPECHE INTO THE SOUTHEAST STATES. THE 00Z LIX SOUNDING
OBSERVED A PWAT OF 2.26" WHICH IS NEAR THE DAILY RECORD. THE BEST
RAIN CHANCES WILL EXIST ACROSS COASTAL AREAS THIS MORNING DUE TO
WEAK ISENTROPIC LIFT AND MARINE INSTABILITY. AS WE HEAD INTO LATE
MORNING INTO THE AFTERNOON, THE FOCUS WILL SHIFT TO NORTH AND WEST
OF I-65 WHERE LOW LEVEL CONVERGENCE WILL BECOME ENHANCED. NUMEROUS
TO WIDESPREAD SHOWERS AND STORMS ARE EXPECTED ACROSS THIS AREA IN
THE AFTERNOON HOURS WHERE MLCAPES WILL CLIMB TO 1500-2500 J/KG.
SCATTERED TO NUMEROUS STORMS ARE STILL LIKELY TO DEVELOP FURTHER
SOUTH AND EAST THROUGH THE AFTERNOON GIVEN THE UNSTABLE AND UNCAPPED
AIRMASS IN PLACE.
SCATTERED TO NUMEROUS SHOWERS/STORMS ARE LIKELY TO PERSIST ACROSS
THE FORECAST AREA INTO THE EVENING, ESPECIALLY ALONG AND WEST OF I-
65. WHILE COVERAGE MAY DIMINISH OVERNIGHT, A CHANCE OF STORMS WILL
PERSIST GIVEN PERSISTENT WEAK LOW LEVEL CONVERGENCE AND THE APPROACH
OF A SHORTWAVE FROM THE WEST (MOVING INTO THE ARKLATEX BY SUNRISE
FRIDAY MORNING.)
LOCALIZED FLOODING WILL BE A POSSIBILITY ACROSS THE AREA TODAY AND
TONIGHT GIVEN THE ANOMALOUSLY MOIST AIRMASS AND PERSISTENT DEEP
LAYER SOUTHWESTERLY FLOW, ESPECIALLY THIS AFTERNOON AND EVENING WEST
OF I-65. WILL MAINTAIN A LIMITED RISK FOR FLOODING IN OUR LOCAL
THREAT GRAPHICS. 34/JFB
SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...AN UPPER RIDGE
STRETCHING SOUTHWEST OVER THE GULF OF MEXICO FROM OFF THE EASTERN
SEABOARD REMAINS STATIONARY THURSDAY THROUGH FRIDAY. THIS RIDGE
CONTINUES TO DEFLECT PIECES OF SHORTWAVE ENERGY MOVING THROUGH AN
UPPER TROUGH STRETCHING SOUTH OVER THE PLAINS. THIS ENERGY
COMBINES WITH A VERY MOIST AIRMASS (PRECIP H20 VALUES AROUND 2.0"
OR ABOVE) AND A STALLED SURFACE BOUNDARY STRETCHING NORTHWEST
ALONG THE NATCHEZ TRACE TO BRING NUMEROUS SHOWERS AND
THUNDERSTORMS INTO FRIDAY, WITH GREATEST COVERAGE BEING OVER
NORTHWESTERN PORTIONS OF THE FORECAST AREA. WITH THE HIGH
MOISTURE LEVELS ALLOWING FOR EFFICIENT RAIN PRODUCTION, WATER
ISSUES WILL CONTINUE TO BE A POSSIBILITY INTO FRIDAY, ESPECIALLY
OVER AREAS NORTHWEST OF THE I-65 CORRIDOR AND ALONG THE COAST. AT
THIS POINT, MAINLY PONDING AND NUISANCE FLOODING IN POOR DRAINAGE
AREAS ARE THE PRIMARY ISSUES, THOUGH WITH TRAINING CELLS POSSIBLE
AT TIMES THURSDAY, MORE SIGNIFICANT WATER ISSUES MAY BE POSSIBLE.
DO NOT FEEL COVERAGE OR EXTENT WILL BE GREAT ENOUGH TO WARRANT AN
FFW, BUT WILL CONTINUE TO MONITOR. LASTLY, WITH ALL THE RAIN AND
INCREASED CLOUD COVER, DAYTIME HIGHS AROUND SEASONAL (LOW TO MID
80S) ARE EXPECTED. OVERNIGHT LOWS (AROUND 70 INLAND TO MID 70S
ALONG THE COAST) A BIT ABOVE SEASONAL CONTINUE, WITH WARMING FLOW
OFF THE GULF AND RADIATIONAL COOLING INHIBITING CLOUD COVER
HANDING AROUND LONGER THAN USUAL.
LATER FRIDAY INTO SATURDAY, A SHIFTING OF THE PLAINS UPPER TROUGH
SHIFTS AND WEAKENS THE GULF/WESTERN ATLANTIC RIDGE TO THE
SOUTHWEST, BECOMING CENTERED OVER FLORIDA. EVEN WITH THE
WEAKENING, THE SHIFTING BRINGS AN INCREASE IN SUBSIDENCE TO THE
NORTHERN GULF COAST AND THE CHANCE OF RAIN DECREASES FRIDAY NIGHT
INTO SATURDAY. TEMPS REMAIN AT ABOVE SEASONAL LEVELS.
/16
LONG TERM /SATURDAY THROUGH TUESDAY/...IN THE LONG TERM, THERE
IS MORE CONSISTENCY IN THE SYNOPTICS IN THE GUIDANCE, WITH BOTH
GFS AND ECMWF SHIFTING THE UPPER RIDGE WEST A BIT MORE, THEN
MOVING IT NORTH TO BECOME CENTERED OVER EASTERN PARTS OF THE
SOUTHEAST BY SUNDAY. A SURFACE RIDGE DEVELOPS ALONG THE
APPALACHIANS TO OFF THE MID ATLANTIC COAST, BRINGING IN DRIER AIR
OVER THE SOUTHEAST AND EASING RAIN CHANCES THROUGH THE WEEKEND
INTO THE COMING WEEK. THE OPERATIONAL ECMWF IS DRIEST THIS
WEEKEND, BUT THE ECMWF ENSEMBLES ARE HINTING A MORE WETTER
FORECAST MORE IN LINE WITH THE GFS, SO HAVE BUMPED POPS CLOSER TO
THE GFS FORECAST. TEMPS ARE DECENTLY CONSISTENT BETWEEN EITHER
SOLUTION, REMAINING AT ABOVE SEASONAL LEVELS, SO HAVE NOT MADE ANY
SIGNIFICANT ADJUSTMENTS THERE.
/16
MARINE...A GENERAL LIGHT ONSHORE FLOW
IS EXPECTED THROUGH THURSDAY AS A FRONT REMAINS STALLED WELL NORTH
OF THE MARINE WATERS AND HIGH PRESSURE CONTINUES TO RIDGE INTO THE
GULF FROM THE SOUTHWEST ATLANTIC. WINDS BECOME EVEN LIGHTER AS THE
FRONT TRIES TO MOVE TO THE COAST BUT WEAKENS ON FRIDAY. AN EASTERLY
FLOW BECOME PREDOMINATE OVER THE WEEKEND INTO THE EARLY NEXT WEEK AS
HIGH PRESSURE BECOMES ESTABLISHED OVER THE EASTERN SEABOARD. THIS
EASTERLY FLOW IS LIKELY TO BE PERIODICALLY MODERATE IN STRENGTH BY
EARLY NEXT WEEK. SEAS WILL BE LESS THAN 2 FEET OUTSIDE OF STORMS
THROUGH THE WEEKEND, BUT WILL LIKELY BUILD TO 2-4 FEET OVER THE OPEN
GULF WATERS BY NEXT MONDAY/TUESDAY. 34/JFB
MOB WATCHES/WARNINGS/ADVISORIES
AL...NONE.
FL...NONE.
MS...NONE.
GM...NONE.
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