Area Forecast Discussion
Issued by NWS Mobile, AL

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FXUS64 KMOB 260446 AAC

Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
1146 PM CDT Wed Apr 25 2018

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


06Z issuance...VFR conditions will prevail this evening followed
by increasing clouds late tonight. A weakening line of showers
and thunderstorms moves across the area between 12Z-18Z Thursday
morning, followed by clearing skies. /13


.PREV DISCUSSION... /issued 1020 PM CDT Wed Apr 25 2018/

DISCUSSION...See updated information for land areas below.

UPDATE...A minor update was issued to slow the progression of the
rain into the area after midnight tonight. Otherwise, no
additional updates are needed at this time. /13

PREV DISCUSSION... /issued 402 PM CDT Wed Apr 25 2018/

NEAR TERM /Now Through Thursday/...Expect increasing clouds along
with better rain chances beginning late tonight continuing through
about midday Thu mainly in response to a deepening short wave trof
moving southeast across the central plains states tonight, then
eastward across the northern gulf states during the day on Thu.
This system looks to be rather progressive through Thu afternoon
leading to mostly showers with embedded thunderstorms moving into
western sections of the forecast area about 3 to 4 hours after
midnight tonight then exiting to the east by early to mid
afternoon. With limited instability and vertical shear in the
boundary layer, though with decent forcing aloft and decent lapse
rates in the mid to upper levels, we will see a few embedded
thunderstorms with this pattern beginning early Thu with the best
coverage occurring over western and northern sections of the
forecast area generally after sunrise then exiting to the east by
early to mid afternoon. Latest guidance shows the better
instability and forcing over western and northern sections of the
forecast area reinforcing this thinking. Model soundings do show
some significant moisture in the boundary layer mostly over the
northern half of the forecast area generally between 12z and 18z
suggesting we could see some brief heavy rainfall where some
locations could see .5 to .75 inches locally by early afternoon.
For now the threat for severe weather remains low to nil including
the threat for flooding or flash flooding. As for temps tonights
lows will be close to seasonal norms ranging from the mid to upper
50s for most inland areas and the lower 60s near the immediate
coast. Highs Thu will 3 to 5 degrees below seasonal norms ranging
from the lower to middle 70s for the northern half of the
forecast area and the middle 70s to the south. 32/ee

SHORT TERM /Thursday night Through Saturday night/...The upper
level closed low pressure system over eastern Tennessee and
northern Georgia will continue to lift northeast Thursday night
and get absorbed along the eastern periphery of a large upper
trough over the eastern conus. The surface low pressure area
across the southeast states will continue to lift northeast as
well, while the associated cold front near I-10 pushes offshore
Thursday evening. It will be dry and cooler Thursday night and
Friday morning.

A fast moving shortwave on the heels of the first low will exit
the southern plains Friday morning, and swing east over the
northern gulf coast Friday afternoon and evening. Precipitable
water values will have lowered to between 0.75 and 1.00 inch
behind the first low prior to the arrival of the shortwave, so
have lowered precipitation chances to include only isolated light
rain showers Friday afternoon, with a thunderstorm or two possible,
across the inland portions of southeast Mississippi and southwest
Alabama. A dry period will resume Friday night through saturday
night. /22

LONG TERM /Sunday Through Wednesday/...The upper level trough
over the eastern conus will slowly move east over the western
Atlantic by the end of the weekend, followed by a medium amplified
upper level ridge building in from the west. The ridge will extend
from the northern gulf to southeast Canada on Monday, and move
over the western Atlantic by midweek. Strong surface high pressure
will build over the region through the weekend, and over the
western Atlantic by late Monday night, keeping the area rain-free
Sunday through Monday night. A southeasterly low level return
flow will set up across the region Tuesday as the center of the
surface high continues to move east over the western Atlantic.
Over- running on the backside of the departing high pressure and
moisture returning to the region is expected to bring mainly
isolated to scattered showers back into the western portions of
the forecast area Tuesday, with again a thunderstorm or two
possible mainly during the afternoon hours due to decreasing
stability. For now, dry conditions are expected Tuesday night
through Wednesday night. /22

MARINE...High pressure will continue over the north central gulf
through Thu then become reinforced in the wake of a cold front
late Thu and Thu night. Expect mostly a light to moderate west to
northwest wind flow through Sat becoming east late Sat into Sun as
high pressure shifts east. The highest winds will likely occur
along and in the wake of the front late Thu afternoon and Thu
evening, gradually diminishing through Fri morning. A moderate
westerly flow redevelops by Fri afternoon into Fri evening then
shifts northwest to north and diminishes through Sat morning.
Small Craft may have to exercise caution ahead and in the wake of
front mostly over the open gulf waters Thu afternoon and Thu
evening. 32/ee




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