Area Forecast Discussion
Issued by NWS Mobile, AL

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FXUS64 KMOB 221341

Area Forecast Discussion
National Weather Service Mobile AL
841 AM CDT Thu Apr 22 2021

NEAR TERM UPDATE...Previous forecast discussion remains on track.
Clear skies across the region this morning with some chilly
temperatures recorded overnight. Some areas were able to reach
and beat their record lows, with others remaining just above.
Here are a few previous record lows that were close too, tied, or
broke their record are noted below:

Mobile Regional AP: 42 (1993) This morning reached a low of 43.
So close!
Greenville: 38 (1993) Tied their record reaching 38 this
Andalusia OPP AP: 48 (2019) - Beat their record with a low of 44.
Destin/Fort Walton Beach 53 (1998)- Beat their record with a low
of 50!
Mobile Downtown AP: 49 (2019) - Reached 50 this morning so
Evergreen Middleton Field 42 (2009) Tied their record of 42.

Enjoy this wonderful weather we have today while it lasts as the
we prepare for another weather event this weekend. JEH/88


.PREV DISCUSSION... /issued 731 AM CDT Thu Apr 22 2021/

12Z issuance...VFR conditions prevail through the TAF cycle. Winds
will generally be northeasterly today between 5-10kts, becoming
more easterly and light going into Friday. JEH/88

PREV DISCUSSION... /issued 458 AM CDT Thu Apr 22 2021/

NEAR TERM UPDATE /Now Through Friday/...Dry, clear, and cool
weather continues through the most of the near term. Flow aloft
begins to transition to northwesterly on through the morning as
ridging moves east into the area by late this afternoon. Through
Friday flow aloft gradually becomes southwest as a neutrally
tilted shortwave trough aloft tracks east and parks itself over
central TX by the end of the period. At the surface, high pressure
moves east across the southeast through tonight and into early
Friday, eventually making its way out over the Atlantic just off
the east coast by the end of the period. Northeasterly surface
flow through today transitions to more easterly tonight as the
high continues tracking east. By Friday, as the high drifts
further east, moisture slowly increases over the region as
southeasterly surface develops on the back side of the high
pressure. Additionally, a low pressure over TX panhandle
associated with the shortwave system aloft gradually shifts
southeast. A warm frontal boundary extending from this low from
the TX panhandle southeast into the Gulf will begin slowly lifting
off to the northeast towards the region going into the short
term. As a result, clouds begin increasing over the region from
the west with a slight chance of some isolated rain showers over
the far southwestern portion of the forecast area going by the end
of the day on Friday. Otherwise, dry conditions continue through
tonight and into early Friday.

As far as temps, highs on Thursday are expected to be in the upper
60s to low 70s across the region. Temps along the coast will feel
a bit cooler given winds remain somewhat elevated by the coastal
regions. Lows on Thursday night will be a bit warmer with
temperatures in the mid to upper 40s across most of the area, but
low to mid 50s near and along the coast. With return flow
developing on Friday, high temps increase slightly with mid 70s
over most of the region except for the far northwestern region of
the forecast area and areas right along the immediate coast where
low 70s is expected due to increasing cloud cover from the west,
and onshore flow keeping temps along the immediate coast slightly
modified. JEH/88

SHORT TERM /Friday night Through Saturday night/...A potent
mid/upper level trough moves east out of the southern Plains and
into the Lower MS Valley Friday night, and then over our region
on Saturday. An associated surface low pressure area over the
southern Plains will lift northeastward in the Tennessee/Kentucky
region. The best available thermodynamic instability and vertical
wind shear supportive of strong mesocyclones would approximately
be from about midnight through mid-morning Saturday. Some of the
mesoscylones that form overnight Friday could be quite intense and
will be capable of all THREE modes of severe weather impacts
[i.e., large diameter hail, damaging straight line wind gusts and
even tornadoes. A strong [EF2+ tornado (especially inland)]. I
also do not want to exclude the coast, as the models may shift
further south. The bulk of the severe deep convection moves off
to the east during the remainder of the day as a dry slot moves
over the region from the west, resulting in a capping inversion
that `should` suppress subsequent second generation severe deep
convection. Any flash flooding that occurs will mainly be Friday
night through noon Saturday, especially across the northern half
of the forecast area where 1 to 3 inches of rainfall is expected.
There will clearly be some lingering thermodynamic instability
Saturday afternoon region-wide, however, we feel any additional
showers and thunderstorms should be weaker, and relegated to the
strongest of boundaries where differential heating occurs (more
likely west than east where some clearing occurs, despite drying).
Highs Saturday will be in the upper 70s to lower 80s. Isolated to
scattered showers and few lingering thunderstorms east of the
Alabama River Saturday evening will move quickly off to the east
by midnight as a cold front advances southeast through the area,
followed by overnight lows in the 50s as winds turn northerly. /22

EXTENDED TERM /Sunday Through Wednesday/...Ridging aloft builds
into the eastern half of the CONUS through early next week. The
ridge amplifies as a shortwave pivots into the Pacific Northwest
on Sunday. The deepening trough aloft quickly encompasses much of
the western half of the CONUS by Tuesday and central portion of
the CONUS by Wednesday. Ensemble guidance supports the general
timing previously mentioned, although there remain some
timing/placement differences in the deterministic guidance
(especially by Wednesday).

Down in the lower levels, a surface high builds into the eastern
half of the CONUS from the Midwest late in the weekend through
early next week. As the high slides east on Monday, surface winds
swing from northerly to southeasterly through the day. As the
ridge aloft and surface high dominate the pattern during much of
the extended, the chances for rain stay zero and temperatures soar
into the mid and upper 80s through Tuesday. Meanwhile, a surface
low develops near the OK/TX panhandles on Tuesday and lifts
northeast through Wednesday as the trough slides into the central
portion of the CONUS. This surface low and the associated cold
front will bring our next chance for rain by late Wednesday.
Showers begin streaming into the area by Wednesday morning and
afternoon with the bulk of the showers and storms moving in late
Wednesday into Thursday. Some of the guidance is hinting that we
will have yet another chance for strong storms with this mid-week
system, but it`s too early to dive into the specifics at this time
given the uncertainty. 07/mb

MARINE...A Small Craft Advisory remains in effect for the Gulf
waters, MS Sound, and Northern/Southern Mobile Bay until 10AM this
morning. Exercise caution condition exist over remaining area
bays. Winds begin to decrease through today with only the far
offshore waters likely remaining under Exercise Caution
conditions. Northeasterly flow through today becomes light to
moderate easterly by tonight. Moderate southeasterly flow is
expected on Friday, before shifting southerly and increasing to
moderate to strong overnight ahead of another cold front. This
said, Small Craft Exercise Caution conditions will likely be
needed on Friday into Friday night, with the potential of needing
another Small Craft Advisory by late Friday night going into
Saturday. Moderate northerly flow is then expected in the wake of
the FROPA by early Sunday. JEH/88


GM...Small Craft Advisory until 10 AM CDT this morning for GMZ630>632-



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