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AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE MOBILE AL
1202 AM CDT SUN APR 19 2015

.AVIATION...
19.06Z KMOB/KBFM AND KPNS TAF CYCLE...
WITH A DRIER AIR MASS MOVING IN FROM THE SOUTHWEST...THERE WILL BE A
PERIOD OF RAIN-FREE CONDITIONS ALONG THE NORTHERN GULF COAST THROUGH
ABOUT 19.09Z FOR THE KMOB AND KBFM TAF SITES...AND THROUGH ABOUT
19.11Z FOR THE KPNS TAF SITE. STILL EXPECTING A LINE OF SHOWERS AND
THUNDERSTORMS TO DEVELOP ACROSS SOUTHEAST LOUISIANA AND SOUTHERN
MISSISSIPPI THAT WILL MOVE THROUGH THE AREA AFTER THOSE TIME FRAMES
AND MOVE THROUGH THE AREA DURING A FOUR HOUR TIME SPAN WITH MVFR
CEILINGS AND VISIBILITIES. SO ADDED A TEMPO GROUP FOR THIS LINE OF
PRECIPITATION...FOLLOWED BY MVFR CEILINGS AFTER THE RAIN THROUGH
ABOUT NOON. VFR CONDITIONS WILL OCCUR THROUGH THE REMAINDER OF THE
FORECAST. /22

.PREV DISCUSSION... /ISSUED 411 PM CDT SAT APR 18 2015/ 

SHORT TERM...(TONIGHT THROUGH MONDAY NIGHT)...FOR TONIGHT THROUGH
SUNDAY...AN UPPER LOW OVER THE CENTRAL PLAINS BEGINS TO BE ABSORBED
BY A LONGWAVE TROF WHICH EVOLVES OVER THE CENTRAL STATES. A SERIES OF
STRONG SHORTWAVES WILL MOVE ACROSS THE REGION IN THE SOUTHWEST FLOW
ALOFT AND BRING HIGH RAIN CHANCES TO THE AREA DUE TO BOTH AN
MCS...MESOSCALE CONVECTIVE SYSTEM...EXPECTED TO TRAVERSE THE MARINE
AREA...AND ASSOCIATED WITH A SURFACE LOW WHICH DEVELOPS OVER THE
LOWER MISSISSIPPI RIVER VALLEY AND MOVES WELL NORTH OF THE AREA.
STORM SCALE INTERACTIONS AND SUB-SYNOPTIC FEATURES HAVE IMPACTED THE
FORECAST SUCH AS THE LINGERING AREA OF CONVECTION OVER THE MARINE
AREA...A REMNANT OF AN OVERNIGHT MCS...AND ANOTHER MCS WHICH APPEARS
TO BE CURRENTLY DEVELOPING SOUTH OF LOUISIANA. THE LATTER MCS HAS
DEVELOPED ON A 850 MB THETA-E RIDGE IN A REGION OF DIFFLUENT
850-300MB THICKNESS...AND BASED ON THE PLACEMENT OF THESE
FEATURES...EXPECT THE MCS TO TRANSLATE GENERALLY EASTWARD OVERNIGHT
AND EVENTUALLY INTO THE NORTHEASTERN GULF.

WITH ABUNDANT CONVECTION EXPECTED OVER THE MARINE AREA THROUGH MUCH 
OF THE PERIOD...THIS WILL SIGNIFICANTLY LIMIT SURFACE BASED 
INSTABILITY OVER THE LAND PORTION OF THE AREA AND DO NOT SEE MUCH OF 
A SEVERE STORM POTENTIAL AT LEAST THROUGH SUNDAY MORNING.  BETTER 
INSTABILITY DOES DEVELOP LATER IN THE DAY ON SUNDAY...BUT FORCING IS 
WEAKER OR NEGATIVE WHICH WILL LIMIT CONVECTIVE DEVELOPMENT 
SUFFICIENTLY THAT AM NOT EXPECTING MUCH OF A SEVERE STORM RISK ON 
SUNDAY EITHER AS THE 850 MB FLOW WILL BE SOUTHWESTERLY ALONG WITH 
THE SURFACE FLOW AND NOT PARTICULARLY STRONG.  THE EXCEPTIONS TO 
THIS ARE POSSIBLY OVER THE NORTHWEST FLORIDA PANHANDLE LATE TONIGHT 
INTO EARLY SUNDAY MORNING SHOULD THE MCS TRANSLATE FURTHER NORTHWARD 
ALLOWING FOR BETTER SURFACE BASED INSTABILITY...AND WILL NEED TO 
MONITOR.

EXPECT CURRENTLY NEGLIGIBLE/ISOLATED PATCHES OF LIGHT RAIN TO BECOME
MORE WIDESPREAD OVERNIGHT AS THE LOUISIANA MARINE AREA MCS
STRENGTHENS...AND AS ADDITIONAL CONVECTION DEVELOPS FURTHER INLAND
OVER THE AREA. HAVE GONE WITH LIKELY POPS FOR MUCH OF THE AREA THIS
EVENING...EXCEPT FOR GOOD CHANCE POPS OVER SOUTH CENTRAL
ALABAMA...THEN CATEGORICAL POPS FOLLOW FOR ABOUT THE SOUTHERN HALF OF
THE AREA OVERNIGHT WITH LIKELY POPS ELSEWHERE AS THE EXPANDING MCS
ADVANCES FURTHER EASTWARD. QPF AMOUNTS LOOKS TO BE INCREASING
OVERNIGHT MAINLY OVER THE SOUTHERN PORTION OF THE AREA...THEN THE
HEAVIER AMOUNTS LOOK CONFINED TO ROUGHLY EAST OF I-65 SUNDAY MORNING
AS SUBSIDENCE BEGINS TO WORK INTO THE WESTERN PORTION OF THE AREA.
WILL HAVE LIKELY/CATEGORICAL POPS ROUGHLY EAST OF I-65 SUNDAY MORNING
THEN CHANCE POPS FOR THE REMAINING PORTION...WITH CHANCE POPS FOR THE
ENTIRE AREA SUNDAY AFTERNOON.

HAVE KEPT THE FLASH FLOOD WATCH IN AFFECT ACROSS THE AREA 
TONIGHT...THEN HAVE TRIMMED TO WATCH TO JUST BE IN EFFECT ROUGHLY 
ALONG AND EAST OF I-65 SUNDAY MORNING AS QPF AMOUNTS ARE TOO LOW TO 
SUPPORT THE WATCH ELSEWHERE. /29

SUNDAY NIGHT...A STRONG SHORTWAVE SWEEPS AROUND THE BASE OF THE
CLOSED LOW OVER THE US/CA BORDER...PUSHING A SURFACE FRONT TOWARDS
THE LOWER MISS RIVER. GUIDANCE IS ADVERTISING SIGNIFICANT DRY
SLOTTING AHEAD OF THE FRONT...WITH A DECREASE IN POPS OVER THE FA.
WITH DAYTIME HEATING SUNDAY ALLOWING FOR A FEW STORMS TO BECOME
STRONG TO SEVERE...AM EXPECTING THIS TO BLEED INTO EARLY SUNDAY
EVENING. AM EXPECTING THIS ACTIVITY TO DECREASE WITH THE SETTING SUN
AND PRETTY MUCH GONE BY MIDNIGHT.

MONDAY INTO MONDAY NIGHT...THE SHORTWAVE SWEEPS NORTHEAST AHEAD OF
THE BORDER UPPER LOW...PUSHING THE FRONT ACROSS THE FA LATE MONDAY
INTO MONDAY EVENING...THEN STALLING OVER THE CENTRAL GULF BY TUESDAY
MORNING. SURFACE HIGH PRESSURE MOVES QUICKLY EAST FROM OVER THE
SOUTHERN PLAINS TO OVER THE LOWER MISS RIVER VALLEY...EASING THE
POST-FRONTAL WINDS (WHICH AM NOT EXPECTING TO BE THAT STRONG WITH THE
DRIVING DYNAMICS WELL NORTH OF THE FA)...SO A PLEASANT TUESDAY
MORNING IS EXPECTED. ANOTHER SEASONABLE WARM DAY MONDAY IS
EXPECTED...WITH TEMPS DROPPING TO AROUND SEASONAL MONDAY NIGHT.

LONG TERM...(TUESDAY ON)...TUESDAY THROUGH WEDNESDAY...THE UPPER LOW
OVER THE US/CA PLAINS MENDERS EASTWARD TO OVER THE GREAT
LAKES...THEN STALLS. THE PIECES OF ENERGY SWINGING AROUND THE BAS OF
THIS SYSTEM PUSH THE SURFACE HIGH FROM OVER THE LOWER MISS RIVER
VALLEY TO OFF THE ATLANTIC COAST. A SURFACE RIDGE REMAINS OVER THE
NORTHER GULF COAST...WITH ONSHORE FLOW RETURNING TO THE FA BY
WEDNESDAY EVENING. TUESDAY AND TUESDAY NIGHT SEE TEMPS DROP TO A BIT
BELOW SEASONAL(70S TUESDAY...50S TUESDAY NIGHT)....BUT BEGIN TO
MODERATE BACK UP WEDNESDAY....WITH TEMPS IN THE 80S RETURNING FOR
WEDNESDAY.

WEDNESDAY NIGHT THROUGH THURSDAY...A LOBE UP ENERGY SWIRLS AROUND
THE BASE OF THE GREAT LAKES UPPER LOW...PUSHING A WEAK BOUNDARY
TOWARDS...THEN PARTIALLY OVER...WITH THE BOUNDARY STALLING OVER THE
NORTHERN HALF OF THE FA BY THURSDAY EVENING. CONTINUE TO REBOUND TO
SEASONABLY WARMS VALUES WITH MOST OF THE FA UNDER ONSHORE FLOW. AS
THE BOUNDARY WORKS ITS WAY NEAR AND OVER THE FA...RAIN AND
THUNDERSTORMS RETURN TO THE AREA...WITH THE BEST CHANCE BEING
THURSDAY.

THURSDAY NIGHT THROUGH SATURDAY NIGHT...UPPER ENERGY THAT HAD
ORGANIZED INTO A CLOSED LOW OVER THE DESERT SOUTHWEST BREAKS DOWN AND
GETS DRAWN EAST BY MORE ENERGY SWEEPING AROUND THE GREAT LAKES
SYSTEM. GUIDANCE AGREES ON A SURFACE LOW FORMING AND MOVING EAST
FRIDAY THROUGH FRIDAY NIGHT. DISAGREEMENT IS WHERE. THE ECMWF IS
ADVERTISING THE LOW FORMING OVER THE OK/KS BORDER AND MOVING EAST-
SOUTHEAST TO OVER THE MS DELTA BY SATURDAY MORNING. THE GFS TAKES A
MORE SOUTHERLY/FASTER PATH...WITH DEVELOPMENT OVER TX AND MOVING EAST
NORTH OF THE NORTHERN GULF COAST BEFORE ENDING UP OVER THE FA BY
SATURDAY MORNING. UP TO THIS POINT...BOTH ARE ADVERTISING RAIN
CONTINUING...WITH THE GFS IS ADVERTISING A COOLER SCENARIO...THOUGH
THAN THE ECMWF. HAVE TRIED BEST TO BLEND...WITH EITHER SCENARIO
POSSIBLE.

SATURDAY AND SATURDAY NIGHT...BOTH ARE ADVERTISING THE SYSTEM'S POST-
SYSTEM FRONT MOVING ACROSS THE FA SATURDAY AND THE FA DRYING OUT. GFS
IS ADVERTISING A STRONGER POST SYSTEM PUSH OF NORTHERLY AIR THAN THE
ECMWF. HAVE WENT IN THE MIDDLE FORE THE FORECAST...WITH THE RESULT
BEING TEMPS AROUND TO A BIT BELOW SEASONAL THE LAST TWO PERIODS OF
THE FORECAST.

MARINE...A LIGHT TO OCCASIONALLY ONSHORE FLOW PREVAILS THROUGH
SUNDAY. A COLD FRONT APPROACHES THE AREA FROM THE WEST SUNDAY NIGHT
INTO MONDAY AND MOVES ACROSS THE MARINE AREA MONDAY NIGHT WITH A
LIGHT TO MODERATE OFFSHORE FLOW IN THE WAKE OF THE FRONT. AN ONSHORE
FLOW RETURNS BY WEDNESDAY AS HIGH PRESSURE MOVES ACROSS THE REGION IN
THE WAKE OF THE FRONT. WINDS AND WAVES WILL BE HIGHER IN AND AROUND
SHOWERS AND THUNDERSTORMS. /29

&&

.PRELIMINARY POINT TEMPS/POPS...
MOBILE      66  81  67  82  58 /  80  40  20  10  10 
PENSACOLA   68  80  71  80  60 /  90  60  20  20  10 
DESTIN      70  78  71  78  62 /  90  90  20  20  10 
EVERGREEN   67  82  68  82  55 /  80  60  20  20  05 
WAYNESBORO  65  83  65  79  54 /  70  30  30  10  10 
CAMDEN      66  82  67  81  54 /  60  50  30  20  10 
CRESTVIEW   67  80  68  82  58 /  90  80  20  20  10 

&&

.MOB WATCHES/WARNINGS/ADVISORIES...
AL...FLASH FLOOD WATCH UNTIL 7 AM CDT SUNDAY FOR CHOCTAW-CLARKE-
     MONROE-WASHINGTON-WILCOX.

     HIGH RIP CURRENT RISK THROUGH SUNDAY EVENING FOR LOWER BALDWIN-
     LOWER MOBILE.

     FLASH FLOOD WATCH THROUGH SUNDAY AFTERNOON FOR BUTLER-CONECUH-
     COVINGTON-CRENSHAW-ESCAMBIA-LOWER BALDWIN-LOWER MOBILE-
     UPPER BALDWIN-UPPER MOBILE.

FL...HIGH RIP CURRENT RISK THROUGH SUNDAY EVENING FOR COASTAL 
     ESCAMBIA-COASTAL OKALOOSA-COASTAL SANTA ROSA.

     FLASH FLOOD WATCH THROUGH SUNDAY AFTERNOON FOR COASTAL ESCAMBIA-
     COASTAL OKALOOSA-COASTAL SANTA ROSA-INLAND ESCAMBIA-INLAND 
     OKALOOSA-INLAND SANTA ROSA.

MS...FLASH FLOOD WATCH UNTIL 7 AM CDT SUNDAY FOR GEORGE-GREENE-PERRY-
     STONE-WAYNE.

GM...NONE.
&&

$$

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