Area Forecast Discussion
Issued by NWS Mobile, AL

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FXUS64 KMOB 241124 AAA

Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
624 AM CDT Mon Apr 24 2017

.DISCUSSION...Updated for latest aviation discussion below.


12Z issuance...Once the low clouds clear this morning, VFR
conditions will prevail through the remainder of the period. /13


.PREV DISCUSSION... /issued 400 AM CDT Mon Apr 24 2017/

NEAR TERM /Now Through Monday night/...An upper low over the Tennessee
Valley will move southeast today. This motion will likely keep the
low clouds in place across the northeast zones through the late
morning with clearing to the south and west. Shortwave upper level
ridging will build in behind the upper low through tonight. This
will maintain conditions continue today with highs in the mid and
upper 70s inland to mid 50s along the coast. Clear skies and light
winds tonight will allow temps to fall into the low 50s inland to
upper 50s and low 60s along the coast. /13

SHORT TERM /Tuesday Through Wednesday night/...Tuesday through
Wednesday, as the upper system currently over the Southeast
meanders off to the east, another round of shortwave energy dives
southeast over the western Conus to over the Southern Plains by
Wednesday evening. The slow moving off of the first upper system
and relative quick movement of the second, western system will
build an upper ridge over the Southeast, bringing increased
subsidence to the area. The result for the forecast area is temps
above seasonal. A surface ridge that has pushed to just west of
the forecast area by Tuesday morning moves over and east of the
forecast area Tuesday into Tuesday night. This brings back light
southerly flow for Wednesday. Moisture influx does not appear to
be very strong Wednesday and mainly confined to near coastal and
southwestern portions of the forecast area. With all this being
said, temps Tuesday are expected to top out in the low to mid 80s,
mid 80s Wednesday with some areas seeing upper 80s. Lows Tuesday
night are expected to range from mid 50s well inland to around 60
over our coastal counties.

Wednesday night, the next round of shortwave energy swings through
an upper trough it dug over the western Plains and begins to head
northeast on the west side of the building upper ridge (now off
the East Coast). The current 00Z guidance swings the system
father south than yesterday`s 00z guidance. This results in
increased upper support along with an earlier passage of the
system`s cold front (smack dab over the area at 12z Thursday,
about 6 hours quicker than yesterday). Instability is still good
for strong to severe storms (~1500j/kg). With increased wind shear
(0-3km shear of 200-300m^s/2^s) and upper support from a jet max
passing just north of the forecast area, there is a good chance of
severe storms later Wednesday night through Thursday morning (with
this solution). The problems lies in timing/path of the upper
system. At this point, feel it wise to keep an eye on this system
until better timing/path consistency occurs. What has been
consistent is increasing coverage of shra/tsra through the night
Wednesday night. Current forecast is based on earlier/stronger low
level flow, limiting overnight lows to mid 60s northeast to low
70s along the coast and southwestern portions of the forecast


LONG TERM /Thursday Through Sunday/...Thursday into Friday,
current guidance swings the system though the area by the end of
the day Thursday. Guidance is still advertising more shortwave
energy diving into the Plains upper trough, pushing a surface
ridge quickly east over the Lower Mississippi River Valley and
Southeast, This restores onshore flow to the forecast area by
Friday morning. With limited airmass chance behind the front,
temps in the mid 80s are expected Thursday after skies clear with
overnight lows in the 60s Thursday night. Current guidance moves
the rain east of the area by Thursday night, and see little to
deviate from this at this point.

Friday through Sunday, the third wave of shortwave energy
organizes into a closed low, meanders around over the Desert
Southwest then begins to swing east. With increasing southerly
flow, rain chances increase through the weekend, with Sunday
though Sunday night being the wettest. With the upper ridge off
the East coast retreating westward and building over the Eastern
Seaboard, temps well above seasonal expected. Temps in the mid to
upper 80s expected Friday through Sunday, with overnight lows in
the 60s to around 70.


MARINE...A moderate offshore flow will continue through this
morning with high pressure from Arkansas to the western Gulf. A
light to moderate onshore flow develops on Tuesday then builds later
in the week with high pressure along the eastern seaboard combined
with a cold front approaching from the west. /13




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