Area Forecast Discussion
Issued by NWS Mobile, AL

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FXUS64 KMOB 290524 AAB

Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
1124 PM CST Tue Jan 28 2020

.DISCUSSION...See updated information for land areas and aviation
discussion below.


.NEAR TERM /Now Through Wednesday Night/...An upper trof which has
been advancing across the south central states continues eastward
across the central Gulf coast states on Wednesday then exits to
the east Wednesday night. An associated surface low moves from
near the Sabine River valley to southeast Louisiana by early
Wednesday morning, then continues eastward over the near shore
Alabama and western Florida coastal waters through Wednesday
afternoon. The surface low continues quickly eastward and emerges
in the western Atlantic late Wednesday night. As the surface low
approaches and moves into the near shore waters, isentropic lift
in the 290-300K layer becomes strong and will support categorical
pops over the entire area on Wednesday. Instability will remain
rather low given the trajectory of the surface low, but elevated
instability aloft should allow for some embedded thunderstorms
generally over the southern portion of the area during the day.
Mainly dry conditions follow for Wednesday night as the surface
low exits off to the east. Highs on Wednesday range from the lower
50s well inland to around 60 near the coast. Lows Wednesday night
range from the upper 30s well inland to the mid 40s at the coast.
A moderate risk of rip currents is expected during the period.


06Z issuance...VFR conditions will be followed by ceilings
lowering to MVFR over the western portion of the area Wednesday
morning, then the remainder of the area during Wednesday
afternoon. Showers will advance eastward into the western portion
of the area overnight, with widespread showers expected over the
entire area on Wednesday which shift mostly east of the area by
Wednesday evening. Light and variable winds at the beginning of
the period become east 5 to 10 knots by 12Z Wednesday, slightly
stronger near the coast, then become northerly around 10 knots by
Wednesday afternoon. /29


.PREV DISCUSSION... /issued 521 PM CST Tue Jan 28 2020/

DISCUSSION...Updated for latest aviation discussion below.

00Z issuance...Scattered to numerous showers advancing from the
west will shift eastward across the area late tonight into
Wednesday. VFR conditions trend gradually lower to IFR/MVFR
ceilings during the day on Wednesday. Light and variable winds
this evening become easterly 5 to 10 knots overnight, slightly
stronger near the coast, then become northeasterly by Wednesday
afternoon. /29

PREV DISCUSSION... /issued 322 PM CST Tue Jan 28 2020/

NEAR TERM /Now Through Wednesday night/...High pressure ridge over
the forecast area today will be shifting off to the east tonight as
an area of surface low pressure currently over the southern Plains
states slides east over southern LA. Models generally consistent in
indicating that the low will be over south central or southeastern
LA by around 6 AM Wednesday, and then move east-southeast along the
MS/AL/FL panhandle coast (or just offshore) during the course of the

With this, most of the forecast area will be on the cooler and more
stable side of the system as the low and associated warm front will
be mainly offshore. The mid/upper level trough associated with this
system is expected to be oriented just to the west of the MS River
by 6 AM Wednesday, and then moving east across our area during the
day on Wednesday. A couple of shortwave disturbances are expected to
round the base of the trough, providing some additional dynamics
along with the isentropic lifting that will be in place across the
region. As the frontal wave of low pressure tracks east over
southern Louisiana tonight, PWATS increase to around 1.00" across
most of the area by daybreak Wednesday. Rain chances will be low
this evening through late tonight, then the increasing isentropic
lift (seen in the 290-300K layer) associated with the approaching
trough will result in scattered to likely PoPs moving in from the
west during the pre-dawn hours Wednesday.

By Wednesday morning, warm front extending out from the weak
surface low near the LA coast southeast to near the FL Keys moves
slowly north during the day, but is expected to remain mostly
offshore. Mid-level lapse rates are expected to range from 6.6 to
7.1C/KM over the Gulf coast region on Wednesday, which may
support isolated rumbles of thunder, but convection looks to be
elevated with the warm front remaining positioned to the south.
MUCAPE values will remain rather low (generally well below 500
J/KG with SBCAPE values even lower). Therefore only general
thunderstorms expected, with no strong to severe storms. Some
lingering showers early Wednesday evening, but precipitation is
expected to be ending across our area by midnight.

Lows tonight expected to range from the low to mid 40s over inland
locations, but closer to 50 degrees along the coast. A little cooler
once again on Wednesday with all the clouds and rain expected, with
highs mainly in the low to mid 50s over inland areas and upper 50s to
lower 60s near and along the coast. /12

SHORT TERM /Thursday Through Friday night/...Axis of mid-level
ridge of high pressure moves over the central Gulf coast Thursday
leading to rain-free weather. Upstream, long-wave upper trof sets
up over the Plains to close out the week. A lead impulse ejects
eastward out of TX Thursday night with enhanced ascent operating
on deeper Gulf moisture also spreading east over the Gulf coast
bringing an upward trend in PoPs Thursday night into Friday. PoPs
to categorical (>80%) Friday. Wave of frontal low pressure over
the central Gulf is progged to track eastward with rains tapering
off into Friday night. Instability is expected to remain weak
with any convection primarily over the open Gulf waters, in closer
proximity to the low track.

Daily highs in the upper 50s to lower 60s would be very close to
seasonal normals. Overnight lows will be cool but well above what we
normally see to close out the month of January. /10

LONG TERM /Saturday Through Tuesday/...Drier pattern over the
weekend with upper trof axis moving eastward over the southeast to
off into the west Atlantic. An upper ridge advances east over the
area Sunday. Long range global models show next southern stream
storm system lifting northeast up across TX and into the Lower MS
River Valley Monday. Although energy deamplifies as it lifts up
across the OH River Valley Monday night, a potentially active high
level southwest flow aloft atop the area suggests a period of
unsettled weather early next week.

Surface high pressure over TX Saturday builds east over the Gulf
coast Sunday making steady eastward progress off into the
southwest Atlantic early next week. As this occurs, an evolving
southerly flow early next week causes highs and lows to trend
warmer and well above climatology. /10

MARINE...A very progressive pattern continues over the coastal
waters this week as a series of low pressure areas move east across
or near the marine area. Light east to southeast winds over
the marine area late this afternoon through tonight, increasing
and shifting from southeast through southwest as an area of low
pressure approaches from the west and moves east across the marine
area during the day on Wednesday. For now it appears winds and seas
will be high end SCEC (winds 15 to 20 knots and gusty with seas
offshore up to around 6 feet) with the passage of this system, but
we will have to see if future model runs indicate a need for a
short duration SCA. Winds and seas will of course be locally
higher in and near scattered to numerous showers and thunderstorms
over the marine area on Wednesday. /12


GM...Small Craft Advisory from 3 AM Wednesday to 6 AM CST Thursday
     for GMZ631-632-650-655-670-675.



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