Special Marine Warning 116, NWS Mobile, AL

Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
1212 AM CDT Mon May 3 2021

.AVIATION...
06Z issuance...Predominately MVFR ceilings are expected over the
area through the period, with occasional lowering of bases into
the IFR levels tonight with some of the stronger storms. Scattered
showers and thunderstorms are expected to spread northeastward
across the area overnight and persists through Monday afternoon.
Southerly winds 10 to 15 knots with occasionally gusts 15 to 20
knots will occur through Monday morning will occur through the
period. /22

&&

.PREV DISCUSSION... /issued 1043 PM CDT Sun May 2 2021/

NEAR TERM /Now Through Tuesday/...The forecast area remains in
the warm sector through Monday as a surface low pressure area over
the Texas Panhandle moves east along the Red River Valley and
another surface low evolves further to the north and moves towards
the Great Lakes. A series of generally modest shortwaves move
across the area on Monday while MLCAPE values increase to
1500-2500 J/kg, potentially around 3000+ J/kg, with daytime
heating. This environment combined with the series of shortwaves,
and also some lingering subtle surface boundaries from past
convection, will be sufficient to support likely pops across
nearly the entire area. 0-6 km bulk shear on Monday will be only
around 25 knots with generally low helicity values, so considering
the instability values am expecting some strong pulse type storms
due to precipitation loading, and cannot rule out isolated severe
storm development. SPC has now included much of the area in a
Marginal Risk on Monday. Rainfall totals through Monday still look
to range from around 0.5 to 1.5 inches most areas, although there
could be corridor of higher totals across south central Alabama
with amounts from 2 to 3 inches. Storms will be slow-movers on
Monday given the weak shear environment, and this could lead to
some flooding concerns which will need to be monitored. Lows
tonight range from the mid to upper 60s inland to around 70 at the
coast. Highs on Monday range from the lower 80s near the coast to
the mid to upper 80s further inland.

An upper shortwave will be progress from the Plains eastward over
the eastern CONUS on Tuesday. At the surface, the low pressure
system will move from eastern Oklahoma toward the Ohio River
Valley. A cold front associated with this will also begin
traversing the ArkLaTex region by this time. The unsettled pattern
will continue through the short term period. Model guidance
indicates a line of showers with embedded storms moving over the
Deep South from Tuesday afternoon as the cold front approaches
from the northwest. Synoptic models show a 70-80 knot upper level
jet progressing southeast over the Deep South as a result of the
upper level shortwave. This looks to mainly impact our far
northwest zones by the end of the near term. There will be ample
instability during the day Tuesday, with 2000-3000 J/kg SBCAPE and
1700-2100 J/kg MLCAPE. Midlevel lapse rates are modest, ranging
from 6-6.6 C/km, but the low level lapse rates range from 6.5 C/km
to even 9.5 C/km in spots Tuesday. Shear will be meager on
Tuesday, as values shown by models are only around 20-25 knots in
the afternoon. In terms of moisture, model PWATs over the local
area increase to 1.6-2.0 inches by Tuesday afternoon. Ultimately,
some strong to severe storms are possible, mainly for the
northwestern portion of the local area Tuesday afternoon. The
Storm Prediction Center has outlooked areas generally along and
northwest of I-65 in a Slight Risk of severe thunderstorms, and
this may be upgraded in future updates. In addition, the Weather
Prediction Center has issued a Slight Risk of excessive rain for
the same areas. Additional rainfall amounts ranges from around 2
inches over southeast Mississippi and far southwest Alabama to
about 1.25 inches over south-central Alabama and portions of the
western Florida Panhandle. Locally higher amounts are possible.
Highs Tuesday afternoon will be in the lower to mid 80s. A high
risk of rip currents remains in effect through the period. /29 /26
/22

&&

.MOB WATCHES/WARNINGS/ADVISORIES...
AL...High Rip Current Risk through late Wednesday night for ALZ265-
     266.

FL...High Rip Current Risk through late Wednesday night for FLZ202-
     204-206.

MS...None.
GM...Small Craft Advisory until noon CDT Monday for GMZ630>632-650-
     655-670-675.

&&

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