Area Forecast Discussion
Issued by NWS Mobile, AL

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FXUS64 KMOB 221236

Area Forecast Discussion
National Weather Service Mobile AL
736 AM CDT Mon Jul 22 2019

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


22/12Z issuance...General VFR conditions expected this morning but
a few northward moving rainshowers bringing local MVFR CIGs to
coastal AL/MS areas. Greater coverage is expected to develop over
inland areas later this morning into the early afternoon hours,
with scattered to occasionally numerous showers and thunderstorm
expected with brief, localized areas of IFR conditions. Late
afternoon and evening will see showers and storms becoming more
isolated, but late tonight will again see development near the
coast and north of highway 84 as a frontal boundary approaches
from the north. South to southwest winds, generally 10 knots or
less, will prevail, except briefly becoming stronger and more
variable in and near showers and thunderstorms. 12/DS


.PREV DISCUSSION... /issued 423 AM CDT Mon Jul 22 2019/

NEAR TERM /Now Through Monday night/...Expect the beginnings of
a changing weather pattern during the near term period. A mid to
upper level trof will be digging south across the eastern portions
of the country today and tonight. As a result, the surface high
pressure ridge that has been in place across the region for the
past several days will begin to weaken by late today and tonight
as a cold front gets pushed to the south and approaches the
northern periphery of the forecast area by late tonight. For
today, the Hi-Res CAM`s are in pretty good agreement with
convection initially developing near the coast, first from Mobile
Bay westward and then developing eastward and becoming more
numerous after sunrise this morning. This is verifying at this
time, as we have had some showers developing over Mobile Bay and
coastal Mississippi over the past couple of hours. Expect this
activity to spread inland across much of the forecast area from
late morning into the early afternoon, where we will carry likely
PoPs over portions of our interior zones. By late afternoon into
early evening, model trends indicate most of the convective
activity will be ending before picking back up late in the night,
especially near the coast where marine showers and storms will
again be developing and also over our far northern zones where the
approaching front will produce enough lift for initiation of some
scattered convection as well. While the potential for severe
weather continues to be very low across the area, some of the
stronger storms may be capable of producing brief strong gusty
winds. In addition, as has been the case for the past few days,
the storms that do develop will be slow movers so localized heavy
rainfall and minor flooding or ponding of water on roads and poor
drainage areas will again be a possibility. Highs today similar to
yesterday, ranging from the upper 80s to lower 90s across the
area. Lows tonight should range from the lower 70s over inland
areas to mid and upper 70s near and along the coast. 12/DS

SHORT TERM /Tuesday Through Wednesday night/...A highly amplified
atypical upper air pattern evolves this period with respect to
climatology. An anomalously deep eastern US trof with H50 mass
fields along its axis some 1 to 3 standard deviations below the
mean sets up while a deep ridge will be anchored over the Four-
Corners of the Desert Southwest. Considering we are moving into
the latter end of July, the upper trof allows an unusual, well
defined surface front to surge southward to the central Gulf coast
by late in the day Tuesday. The front serves as a focus for
enhanced lift as it pools a zone of deep moisture along and south
of southward advancing frontal circulation. Thus, categorical
PoPs at or above 80% for Tuesday. Will also be watching for the
potential of a few strong storms Tuesday. The front makes steady
southward progress into the coastal waters Tuesday night and
begins to slow/stall from off the southeast US coast to the lower
TX coast Wednesday and Wednesday night. Rain chances to reflect a
lowering trend from north to south Wednesday with little to no
rain expected along and northwest of I-65 and probabilities
lowering to a range of 20-40% southeast of the interstate. By
Wednesday night, chances look to become more confined out over
the coastal waters.

With increase in rain chances and thickening clouds Tuesday,
highs only range from 83 to 87. With the front south of the area
by Wednesday, similar highs expected. Overnight lows to trend
coolest over the northwest zones with numbers expected to be
closer to 65. Elsewhere, lows range in the mid to upper 60s along
the I-65 corridor to mid 70s along the immediate coast. /10

LONG TERM /Thursday Through Sunday/...Mid-level trof axis
extends from the Appalachians to southeast LA, while surface front
out over the Gulf becomes quasi-stationary/weakens to close out
the week. Deepest moisture streams along the frontal zone over
Gulf with rain chances remaining on the low side Thursday. Gulf
moisture may creep northward into Friday bringing a return to a
chance of showers and perhaps a few storms for at least the
southern half of the local area. Into the weekend, a flat mid-
level ridge sets up over the central/southern Gulf while trof
axis, although not as well pronounced, remains in place over the
deep south. Mid-level impulses riding eastward on the northern
periphery of the Gulf ridge/base of deep south trof axis favors a
modest PoP Saturday and Sunday. Daytime highs gradually modify
into the upper 80s to lower 90s. Overnight lows gradually moderate
as well. /10

MARINE...A high pressure ridge over the eastern and northern Gulf
of Mexico today will be weakening tonight as a cold front moves into
the southeast states and approaches the marine area from the north.
This cold front is then expected to move south into the marine area
late Tuesday and Tuesday night then gradually dissipates over the
central Gulf mid to late week. Winds and seas will increase
slightly late Monday night through Wednesday in association with
the front being in the vicinity, but not significantly. Scattered
to numerous showers and thunderstorms will be in the forecast for
most of the period with the front remaining in the vicinity. 12/DS




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