National Weather Service National Headquarters

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

-- Discussion containing changed information from previous version are highlighted. --
364
FXUS64 KMOB 202340
AFDMOB

Area Forecast Discussion
National Weather Service Mobile AL
640 PM CDT Tue Apr 20 2021

.AVIATION...
21/00Z Issuance...VFR conditions through the period with only a
few high clouds expected. Winds initially south to southwest 5 to
10 knots this evening, but shifting to the west and northwest
overnight as a dry cold front moves south across the area. By
Wednesday morning, the northwesterly winds will increase to around
10 to 15 knots with a few higher gusts possible. /12

&&

.PREV DISCUSSION... /issued 402 PM CDT Tue Apr 20 2021/

NEAR TERM UPDATE /Now Through Wednesday/...Aloft, mainly zonal
flow is expected over the northern Gulf coast through the near term
period. Surface high pressure will also persist into this evening. A
cold front will then approach the Deep South this evening, with
passage over the local area expected late tonight through early
Wednesday morning. PWATs between 0.6-0.8 inches are shown by model
guidance around midnight along and ahead of the cold front, which is
expected to extend from Louisiana up through middle Tennessee and
Kentucky by this time. However, this moisture will decrease as the
front moves southeast through the overnight hours. By early
Wednesday morning when the front moves through, PWATs will only be
around 0.6 inches over the local area, decreasing even further
through the morning as dry air is filtered in behind the front.

With cold FROPA late tonight into early Wednesday morning, lows
tonight will be a bit cooler. Expecting lows to range from the lower
40s to upper 40s and around 50 degrees along and northwest of I-65.
Areas southeast of I-65 will then be in the lower to mid 50s. In
fact, these low temperatures are just below the seasonal norms for
this time of year, with normal lows being 56 degrees and 58 degrees
for Mobile, AL and Pensacola, FL, respectively. A cooler day is also
on tap for Wednesday, as highs will struggle to get out of the 60s
along and northwest of I-65. Highs will then be in the upper 60s to
lower 70s for areas southeast of I-65.

Lastly, a LOW RISK of rip currents will continue through Wednesday
night. /26

SHORT TERM /Wednesday night Through Friday night/...A dry mainly
zonal flow pattern aloft will persist across the forecast area
Wednesday night and Thursday, while a cool surface ridge of high
pressure continues to build across the Mississippi and Tennessee
Valley regions and adjacent north central Gulf Coast region.
Mostly clear skies and a dry surface airmass along the building
surface ridge will allow for cold temperatures across our forecast
area early Thursday morning. Near record low temperatures remain a
good possibility over much of our region with lows forecast to
range in the upper 30s to lower 40s along and north of the
Interstate 10 corridor to the mid 40s to around 50 degrees along
the immediate coast. We continued to trend low temperatures toward
the warmer guidance numbers given that elevated northerly winds
could keep temperatures a little higher than would otherwise occur
in a calm wind pattern. Here is the list of record lows for April
22:

Mobile: 42 (1993)
Pensacola: 46 (1993)
Evergreen: 38 (1993)
Greenville: 38 (1993)
Andalusia: 35 (1993)
Crestview: 41 (1993/2000)
Niceville: 38 (1993)
Waynesboro: 36 (1993)
Wiggins: 40 (1993)

An upper level trough over the Desert Southwest Thursday night is
is forecast to move toward the southern Plains through Friday and
then will quickly translate toward the ArkLaTex region by late
Friday night. Clouds will gradually increase across our area
Thursday night into Friday as layer moisture trends upward within
the zonal mid level flow pattern. The lower levels will remain
quite dry Thursday night, so will keep a dry forecast going into
Thursday night. Deep layer moisture will increase considerably
Friday-Friday night along an approaching shortwave trough embedded
within the westerly flow aloft. Precipitable water values will
increase to 1.4 to 1.7 inches Friday and Friday night across our
area. Ascent will increase over northwestern portions of our area
Friday afternoon and across southeast MS and adjacent southwest AL
during the day Friday and over most of our CWA Friday night.
Showers and a few thunderstorms will spread over our region during
this time. We will have POPs increasing to 60-80% Friday night
over most locations away from the coast. The highest coverage
currently looks focused over interior southeast MS after midnight.
Deep layer and low level shear increases over the region after
midnight. 45-55 kt of southwesterly 850 mb flow is expected to
spread into locations west of I-65 after midnight, along with
500-1000 J/KG of MLCAPE, which could bring a low end threat of
severe storms over northwestern portions of our area overnight
Friday night. Locally heavy rainfall will also be possible. Still
some uncertainty on overall timing of any severe and heavy rain
threat, but will watch trends closely over the next several days.
/21

EXTENDED TERM /Saturday Through Tuesday/...The severe weather
threat may increase across much of our CWA during the day
Saturday. Surface dewpoints are forecast to rise into the mid to
upper 60s across much of the area through Saturday morning, which
could contribute to MLCAPE values between 1000-2000 J/KG. The
increased instability along with strong deep layer and low level
shear continuing to overspread the region will create a favorable
environment for damaging winds, large hail, and possibly a couple
of tornadoes embedded within the convective complex moving across
our region through Saturday afternoon. Locally heavy rainfall and
flooding concerns may also be possible on Saturday. We have POPs
very high (70-90%) across our forecast area through the day
Saturday. Drier conditions return Sunday through Tuesday as
northwest flow aloft returns late in the weekend in the wake of
the departing shortwave trough and as ridging aloft builds in
early next week. Temperatures may warm back into the upper 70s to
lower 80s by Monday and Tuesday underneath the building ridge
aloft.

Increasing southerly flow will bring an increasing risk of rip
currents and elevated surf to our local beaches late Friday and
Saturday. /21

MARINE...Light to moderate westerly flow this afternoon will become
moderate to occasionally strong and northerly late tonight into
early Wednesday morning as a cold front moves over area waters. A
Small Craft Advisory has been issued for Southern Mobile Bay,
Mississippi Sound, and the Alabama Gulf Waters during this time due
to increased winds. Another Small Craft Advisory may be needed once
again Wednesday night into Thursday morning due to elevated winds,
mainly over the Gulf waters. Winds are then expected to decrease and
transition to be easterly by Thursday afternoon. Winds will be
moderate and from the southeast on Friday, then shift to be
southerly and increase to be moderate to strong overnight ahead of
another cold front. Seas will also increase during this time. This
will be monitored for the potential of needing a Small Craft
Advisory. Moderate northerly flow is then anticipated in the wake of
the front Saturday night. /26

&&

.MOB WATCHES/WARNINGS/ADVISORIES...
AL...None.
FL...None.
MS...None.
GM...Small Craft Advisory from 5 AM to 1 PM CDT Wednesday for GMZ631-
     632-650-670.

&&

$$

This product is also available on the web at:
http://weather.gov/mob