Area Forecast Discussion
Issued by NWS Mobile, AL

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FXUS64 KMOB 271130 AAA
AFDMOB

Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
630 AM CDT Mon Mar 27 2017

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

&&

.AVIATION...
12Z issuance...MVFR to IFR cigs and visibilities through about
27.14z followed by MVFR to VFR cigs through about 28.03z followed
by MVFR to IFR cigs through 28.12z. Lower cigs and visibilities
mainly in patchy fog and low status generally through mid morning
followed by isolated to scattered showers and thunderstorms
through mid to late afternoon...then more fog and low stratus by
late this evening and overnight. Winds will be southeast to south
at 8 to 14 knots with through early this evening diminishing to 4
to 6 knots by late this evening continuing through 28.12z. Higher
gusts up to around 20 knots will also be possible mainly during
the late morning and afternoon hours. 32/ee

&&

.PREV DISCUSSION... /issued 516 AM CDT Mon Mar 27 2017/

NEAR TERM /Now Through Monday night/...The main focus for today
continues to be a marginal risk for a few strong to severe
thunderstorms affecting mostly northern portions of the forecast
area of generally north of highway 84 and west of the I-65
corridor...beginning around midday then moving north and east of
the forecast area by late this afternoon or early this evening.
The main threats still look to be damaging straight-line winds
and large hail.

Latest model guidance continues to show next active shortwave trof
passing well to the north of the region or generally moving across
the mid Mississippi and Ohio River valleys later today and early
tonight limiting the better forcing aloft further south across the
north central gulf states. Most of the guidance continues to show H5
temps lowering to around -12 to -15 degrees across the region along
with wetbulb zero heights between 8 and 9 kft supporting the threat
for large hail of 1 inch or greater. These conditions have
shifted slightly south and east from previous thinking along with
surface based capes generally ranging from 800 to 1200 J/KG
combined with 0-6km bulk shear values still around 40. Similiar
to the last couple events moisture return out ahead this next
system continues to be limited leading to isolated to scattered
coverage at most through this afternoon or early this evening.
Later this evening and overnight skies generally clear from from
west to east with areas of fog likely for most areas. Some sun is
also possible during the day today generally over extreme eastern
parts of the forecast area.

As for temps will lean towards the warmer mav numbers for highs
today due mostly from persistence resulting in highs in the lower
80s for most inland areas and the mid to upper 70s along the
immediate coast. For tonight will lean above the warmer mos values
due to mostly cloudy skies continuing through early tue morning
resulting in lows in the lower to middle 60s inland and the middle
60s along the immediate coast. 32/ee

SHORT TERM /Tuesday Through Wednesday night/...Weak shortwave
ridging aloft is expected to build across the central Gulf Coast
region on Tuesday, while a surface ridge of high pressure
meanwhile continues to nose westward from the western Atlantic
Ocean through the northern Gulf of Mexico. A warm and moist
southerly low level flow pattern will persist across our forecast
area Tuesday, with highs once again expected to warm into the
lower to mid 80s over much of the interior, and in the mid 70s to
around 80 degrees closer to the coast. Despite shortwave ridging
aloft, very minor perturbations in the flow moving overhead in
conjunction with modest deep layer moisture (precipitable water
values around 1.25" to 1.33") and weak instability (MLCAPEs to
around 500 J/KG) will support the development of isolated
convection around the area again Tuesday, particularly over
interior areas, and will carry 20-30% convective coverage.
Convection should quickly diminish with loss of daytime heating
and will have a dry forecast Tuesday night. Conditions may once
again be favorable for patchy fog development late Tuesday night,
and have added mention to the forecast. Lows Tuesday night should
range from around 60 to the mid 60s.

Ridging aloft should slowly advance eastward across the
southeastern U.S. on Wednesday, as mid level flow transitions
southwesterly over the Mississippi Valley ahead of the next deep
upper level low that will be moving across the TX/OK Panhandles. A
drier and more subsident airmass will be in place across our
forecast area Wednesday, with precipitable water values averaging
less than 1", so expect mostly sunny skies and dry weather. Highs
Wednesday should range from the lower to mid 80s again inland,
with a few of the typically warmer spots approaching the upper
80s. Readings near the coast should average in the mid 70s to
around 80 degrees. Convection Wednesday night should stay well to
our west, so have a dry forecast continuing with overnight lows
once again ranging from around 60 to the mid 60s. /21

LONG TERM /Thursday Through Sunday/...We are still looking at
potentially active period of showers and thunderstorms arriving
during the Thursday and Thursday night time frame. The upper level
low over the Plains states is expected to lift northeastward
toward MO during the day Thursday, then toward IL/IN Thursday
night. Mid level diffluent flow will spread eastward from the
Mississippi Valley to the Gulf Coast states Thursday into Thursday
night. Associated large scale ascent should result in scattered to
numerous showers and thunderstorms spreading eastward across our
area during this time frame. The latest guidance indicates that
the best coverage of showers and thunderstorms during the day
Thursday will be roughly along and west of the I-65 corridor,
before numerous showers and storms spread east over the entire
area Thursday evening/night, with convection exiting our eastern
zones sometime late Thursday night or early Friday morning.
Although medium range guidance has backed off a little on
dynamics over our area with this system as compared to yesterday,
there is still potential for severe weather to impact our region
Thursday into Thursday night as we remain in the warm sector
ahead of the approaching system. MLCAPE values up to around 1000
J/KG, steep mid level lapse rates (up to 7-7.5 C/km in the 700-500
mb layer), 40-60 knots of 0-6 km shear, a respectable low level
jet (up to around 40 knots 850 mb flow), and 0-1km storm relative
helicity up to 150-250 m2/s2 all portend a threat of storms
capable of producing all severe modes, including isolated
tornadoes Thursday into Thursday night. SPC`s Day 4 outlook for
Thursday continues to place a good portion of our CWA in a 15%
severe risk, and will continue to highlight in the HWO and local
graphics. We may also have to monitor for heavy rainfall and
localized flooding. We will continue to watch this system closely
and will be refining the forecast over the next few days.

Drier mid level zonal flow will spread across our area Friday and
Saturday with no precipitation expected. Yet another upper level
storm system could bring the next round of showers and storms to
our forecast area by Sunday and Sunday night. /21

MARINE...A moderate onshore flow will continue through mid week
then build later in the week as a stronger short wave trof
approaches from the west...combined with surface high pressure
continuing along the eastern seaboard. Seas will continue to range
from 2 to 3 feet through midweek then build to 4 to 6 feet late
in the week and over the weekend. Isolated showers and
thunderstorms will be possible later today and early
tonight...followed by better coverage on thu. A few strong to
severe thunderstorms will be possible on thu when the stronger
system approaches from the west. 32/ee

&&

.MOB WATCHES/WARNINGS/ADVISORIES...
AL...High Rip Current Risk through this evening for ALZ265-266.

FL...High Rip Current Risk through this evening for FLZ202-204-206.

MS...None.
GM...None.
&&

$$

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