Area Forecast Discussion
Issued by NWS Mobile, AL

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FXUS64 KMOB 201731

Area Forecast Discussion
National Weather Service Mobile AL
1231 PM CDT Sat Jul 20 2019

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


18Z issuance...Expect gusty winds and locally lower cigs/vis due
to heavy rain in and around scattered showers and thunderstorms
this afternoon and evening. Activity wanes after sunset before
redeveloping tonight along the coast and offshore. Outside of
convection, VFR/MVFR conditions and light southerly winds
prevail. /49


.PREV DISCUSSION... /issued 439 AM CDT Sat Jul 20 2019/

NEAR TERM /Now Through Saturday night/...Expect another fairly
active weather day across the area today as widespread showers and
thunderstorms should again develop. Similar to yesterday, expect
convective development to be beginning over the Gulf and near the
coast by sunrise this morning, with a few showers and storms over
interior areas before sunrise as well. Showers and storms will
then develop and become more widespread over interior areas late
in the morning and into the afternoon hours, especially for parts
of southeast Mississippi and southwest Alabama. A very moist
airmass, combined with daytime heating and left over outflow
boundaries from the convection of the past 24 hours should support
scattered to numerous showers and storms by late morning and
continuing into the afternoon hours. All of the High-Res
Convective Allowing Models are similar in showing the trend of
widespread showers and storms today, most likely near the coast
earlier in the morning and then over the interior western half of
our forecast area late in the morning and into the afternoon
hours. Went with categorical PoPs (around 80 percent) over the
western half of the area today, with likely Pops (60 to 70
percent) elsewhere. Rain cooled air and lower projected CAPE`s
over the eastern portions of the forecast area may tend to limit
convective coverage somewhat there, especially this afternoon.
Over the western half of the area, models suggest MUCAPE`s
possibly reaching 2500 to near 3000 j/kg by mid to late morning,
resulting in plenty of instability to support convection. Other
parameters for severe convection are rather limited however as
very little shear is noted, and no dry air aloft. However, due to
expected strong updrafts and sufficient water loading, some of the
storms could produce strong downdraft winds just as they did
yesterday afternoon. Most data suggests that convection will
diminish early in the evening, with only minimal coverages of
showers and storms from mid evening and overnight. Will see a
slight increase in coverage over Gulf waters late tonight. Due to
extensive cloud cover and precipitation, went a little below
guidance with today`s max temperatures, with highs expected to
range from the mid 80s west and coastal to around 90 degrees over
eastern portions of the forecast area. Lows tonight expected to be
in the lower 70s over all of the interior zones, mid 70s along
the coast. 12/DS

SHORT TERM /Sunday Through Monday night/...Inverted mid-level
trof axis aligned from the TN River Valley to off the southeast LA
coast Sunday morning moves little during the day. Forcing within
the trof feature operates on a deep layer moisture profile that
remains mostly unchanged (PWATs ranging from 1.8 to 2.0 inches).
The result is the formation of scattered to numerous showers and
storms Sunday as the environment destabilizes. Some of the storms
locally strong producing brief strong wind gusts, frequent
lightning and locally heavy rains. Although cannot discount a few
of the stronger storms possibly intensifying briefly to severe
levels, weak 0-6 km shear magnitudes suggest the risk of widespread
severe weather is low. Surface high pressure from the southwest
Atlantic noses west over the northern Gulf coast and maintains a
warm moist south to southwest flow to close out the weekend. To open
up the new week, lowering mid level heights associated with a long-
wave trof advance eastward across the upper Mid-West/Mid MS River
Valley Monday morning. The trof amplifies as it dives across the
Appalachians and Mid-South Monday night. Atypical for summer, the
progression of the upper trof brings a well defined surface front
into the deep south late in the short term. Chances of showers
and storms to continue.

Daily highs range from the upper 80s to lower 90s. Overnight lows in
the lower to mid 70s interior to 75 to 80 closer to the coast. /10

LONG TERM /Tuesday Through Friday/...Surface front sinks
southeast, draped from the east coast to the upper TX coast Tuesday.
With this orientation, the front will be aligned over the heart of
the forecast area serving as a focus for enhanced ascent as deep
moisture pools into the frontal circulation. Thus, showers and storm
chances are favored to be likely to categorical Tuesday. Frontal
boundary sinks a bit more to the southeast and becomes quasi-
stationary near or just off the coast by Wednesday. Showers and
storms look to be likely over the western FL panhandle to coastal
Alabama and points offshore Wednesday and Thursday. Lower chances
over the interior. Front potentially easing back northward to end
the week with showers/storms likely over a larger part of the area.
Considering the front, clouds and rain chances, daytime highs
through much of the medium range look to stay in the 80s. Overnight
lows may dip into the mid 60s over the northwest zones Wednesday
and Thursday mornings. /10

MARINE...A high pressure ridge over the eastern and northern Gulf
today will persist through Monday night with a light to occasionally
moderate south to southwest flow continuing into the early part of
next week. A weak trough of low pressure will continue over the
interior southeast states. A cold front will move south toward and
possibly into the marine area by Tuesday night or Wednesday, with a
light west to northwesterly flow developing. Little change in seas
early in the period, but perhaps a slight increase in winds in seas
later in the period as the front approaches. Scattered showers and
thunderstorms will remain a possibility through the period. 12/DS




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