Area Forecast Discussion
Issued by NWS Mobile, AL

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FXUS64 KMOB 202324
AFDMOB

Area Forecast Discussion
National Weather Service Mobile AL
524 PM CST Wed Feb 20 2019

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

&&

.AVIATION...
00Z issuance...Showers and thunderstorms continue this evening west
of I-65 as a cold front stalls over the local area. West of this
front, expect cigs/vis at MVFR levels and light northwest winds.
East of this front (roughly along and east of I-65), southerly
winds prevail and conditions remain at IFR/LIFR levels this
evening, then drop to VLIFR overnight tonight as dense fog
settles in. Conditions improve somewhat during the day Thursday as
cigs/vis return to IFR levels. Scattered showers are expected
across the area Thursday. /49

&&

.PREV DISCUSSION... /issued 413 PM CST Wed Feb 20 2019/

NEAR TERM /Now Through Thursday/...The window for any severe
weather is closing quickly late this afternoon as upper dynamics,
support begins to lift away from our forecast area. Could still see
an isolated strong to severe storm over our far northwestern zones,
but that threat is diminishing rapidly. Plenty of low level shear
and instability, but soundings show a very moist profile and also
some capping over most of our area (especially down near the coast
where marine layer influences exist), both of which have limited
the severe threat over our area today.

For tonight, both global and short term Hi-Res models indicate that
the frontal boundary just to the west of our forecast area late this
afternoon will drift east into our area, but becoming stationary
near or just north and west of the I-65 corridor late tonight. This
boundary will remain nearly stationary, or more likely begin to lift
back to the north as a warm front on Thursday. Forcing aloft along
this frontal boundary will be weakening as weak mid/upper level
ridging develops. As a result, no continuing severe threat expected
tonight, and the chances for heavy rainfall has also decreased
slightly. There will still be some persistent rainfall along and
north of the frontal boundary overnight, and some locally heavy
rainfall could occur, especially along and north of Camden, Grove
Hill, Leakesville line. Rainfall totals of 1 to 1.5 inches are
generally expected, with the highest amounts up toward Choctaw and
Wilcox counties. But, some localized amounts up to around 2 inches
will be possible. We will maintain a LIMITED THREAT of Flash
Flooding for that area through very early Thursday morning.

On Thursday, rain chances will decrease slightly as the front lifts
back to the north and nearly all of the forecast area will be in the
warm sector south of the boundary. Still expect scattered showers
and isolated thunderstorms and warm, muggy conditions for most
locations. Maybe a tad cooler up toward Wayne and Choctaw counties
as they may still be just to the north of the frontal boundary
through about midday. Cloudy skies will continue through Thursday.
South to southeasterly flow will maintain high dewpoints across the
region, mainly in the upper 60s and lower 70s.

Went above MOS guidance for lows tonight, ranging from the mid 50s
north to the mid 60s south. Highs Thursday in the mid and upper 70s
over much of the forecast area, but mid 60s far northwest.

With the warm and moist southerly flow over near shore water
temperatures still in the upper 50s in some cases, dense fog will
continue to be likely tonight into early Thursday. Dense Fog
Advisories are already in place for near shore coastal waters and
bays, as well as southern half of interior forecast area through
tonight. 12/DS

SHORT TERM /Thursday night Through Saturday night/...An upper ridge
stretches north along the Eastern Seaboard through the period. A
series of passing upper shortwave systems get directed northeast as
they move over the Southern Plains by this ridge, remaining
northwest of the forecast area. The first shortwave system passes
Thursday night into Friday night, and in combination with a surface
ridge building west over the northern Gulf coast, shifts a stalled
surface front over the forecast area north of the area, restoring
moist southerly flow over the area. Rainshowers along and north of
the retreating boundary will shift north with the northward shifting
surface boundary, and the highest PoPs remaining along and north of
the boundary. Temperatures rise to well above seasonal levels, with
the East Coast upper ridge maintaining its control. Daytime highs in
the upper 70s to around 80 are expected Friday, with overnight lows
in the 60s Thursday and Friday nights.

Fog development is expected Thursday and Friday nights. With warm
moist Gulf air flowing over cooler near shore Gulf and bay waters
having temperatures in the upper 50s to low 60s, fog development is
likely, with a chance of dense fog being possible, especially closer
to the coast. Have put areas of fog in these areas for now.

Saturday into Saturday night, a stronger shortwave trough moves over
the Plains and passes well northwest of the area. A trailing cold
front from this system moves across the area Saturday night.
Guidance varies on the amount of instability ahead of the front
Saturday. Enough wind shear for a few strong to marginally severe
storms is possible Saturday into Saturday evening, but the
instability is expected to be limited, limiting the chance of severe
weather. At this point, a few strong to marginally severe storms
will be possible, but do not feel an organized severe event is
likely. Temperatures Saturday remain above seasonal ahead of the
approaching front, rising to around 80. Saturday night, temperatures
begin to fall as cooler air moves over the area, but with the
relatively weak nature of the coming cold front, lows Saturday night
(generally in the 50s) are again expected to be above seasonal
norms.
/16

LONG TERM /Sunday Through Wednesday/...The upper flow becomes zonal
over the Southeast Sunday into the weekend, with cooler drier air
overspreading the forecast area. Temperatures around seasonal norms
are expected Sunday through Monday.

Monday night through Wednesday, surface high pressure passes north
of the area and moves off the Eastern seaboard, bringing southerly
flow back to the region by Tuesday. An increasing coverage of
isentropic upglide rainshowers and few elevated thunderstorms
Wednesday is expected. Temperature rise back to above seasonal
norms, but the increasing rain and cloud cover will help to temper
the rise. Highs in the mid to upper 60s expected with lows rising
back into the 50s by Tuesday night.
/16

MARINE...A moderate onshore flow will continue this evening with
Exercise Caution conditions, but become light Thursday through
Friday night. Expect increasing onshore flow again by late Saturday
and Saturday night as a front approaches from the west, with
Exercise Caution conditions redeveloping. This next cold front is
expected to push east across the marine area by Sunday with a
moderate to strong offshore flow developing in its wake. winds and
seas will likely be approaching Small Craft Advisory conditions,
especially offshore, by late Sunday into Monday. Areas of fog, dense
at times, will likely continue over the near shore coastal waters
and areas bays through the remainder of the week before the front
arrives. 12/DS

&&

.MOB WATCHES/WARNINGS/ADVISORIES...
AL...Dense Fog Advisory until 9 AM CST Thursday for ALZ055>060-
     261>266.

     High Rip Current Risk through Thursday afternoon for ALZ265-266.

FL...Dense Fog Advisory until 9 AM CST Thursday for FLZ201>206.

     High Rip Current Risk through Thursday afternoon for FLZ202-204-
     206.

MS...Dense Fog Advisory until 9 AM CST Thursday for MSZ078-079.

GM...Dense Fog Advisory until 9 AM CST Thursday for GMZ630>636-650-
     655.

&&

$$

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