955 
FXUS64 KMOB 131144
AFDMOB

Area Forecast Discussion
National Weather Service Mobile AL
644 AM CDT Wed Apr 13 2022

.AVIATION...
12Z issuance...Mainly VFR cigs should prevail at all TAF sites
through the day. Some MVFR cigs/vsbys are possible later this 
afternoon across southeast Mississippi into interior southwest
Alabama as a round of showers and thunderstorms move across the
area. Cigs/vsbys lower to MVFR this evening as strong low level
moisture advection continues in advance of an approaching front.
Further deterioration to IFR is expected at the TAF sites after
approximately 5-8z, as widespread showers and thunderstorms ahead
of the front move through the region. The front should move across
the coast with a switch to northerly winds just beyond this
forecast period. Brisk southeast to south winds are expected
prefrontal sustained between 12 and 15 knots, with occasional
gusts in excess of 25 knots through the period. /JLH

&&

.PREV DISCUSSION... /issued 442 AM CDT Wed Apr 13 2022/ 

.NEAR TERM UPDATE /Now Through Thursday/...Broad upper level 
ridging remains in place this morning across the central Gulf 
Coast and extends eastward across the Florida Peninsula. An 
amplifying upper level trough continues to dig across the Central 
and Southern Plains this morning and will be the next weather 
maker across our area later today and tonight. 

A lead shortwave embedded within southwest flow aloft is 
currently lifting northeast across the Mid South. This shortwave 
was responsible for initiating and maintaining a QLCS as it moved 
across Arkansas into northern Louisiana and western Mississippi. 
This shortwave is beginning to lift out to the north with the 
residual squall-line moving into a more stable airmass across 
eastern Mississippi. This has resulted in a notable weakening and 
this should continue to weaken and eventually dissipate by 
sunrise. There may be a few lingering showers across interior 
portions of southeast Mississippi and southwest Alabama prior to 
the line completely falling apart. Have maintained a small pop 
across these locations for early this morning. 

Another concern early this morning is an area of enhanced winds 
across locations along and west of I-65. These winds are in 
association with a weakening wake low that developed behind a 
dying convective line from Tuesday evening. Winds gusting between 
25 and 35 mph have been common across southeast Mississippi and 
southwest Alabama this morning. This should continue for the next 
few hours before gradually diminishing around sunrise. 

Dry conditions will briefly return to the entire area later this 
morning as mid level ridging briefly builds back in over the 
forecast area this morning behind the departing early morning 
shortwave to our northwest. This should allow for appreciable 
heating by later this morning through the afternoon. In addition, 
southeasterly low level flow will continue to advect low level 
moisture northward across our area with dewpoints remaining in the
mid to upper 60s across the western half of the forecast area.

The amplified upper trough to our west will lift northeast from 
the Southern Plains through the Lower and Middle Mississippi 
Valley by this evening as it takes on an increasingly negative 
tilt. As this occurs, a strengthening upper level subtropical jet 
streak on the order of 130kts is progged to spread in from the 
west along the western Gulf Coast. At the same time, a phased 
polar jet streak to the north in the upper levels will lift north 
through the Mid South and Middle Mississippi Valley. An area of 
enhanced differential divergence is noted with the left exit 
region of the subtropical jet by this afternoon. This should help 
to enhance large scale ascent across portions of southeast 
Mississippi by late this afternoon. In addition, the wind fields 
aloft become quite diffluent across southeast Louisiana into 
southeast Mississippi by late afternoon also helping to enhance 
ascent. The atmosphere is likely to remain capped to convection by
a warm nose around 850mb through much of the day. Sufficient 
diurnal heating, low level moistening, and the noted large scale 
ascent should work to erode and lift out the capping inversion by 
late afternoon (21-23z). This is supported by much of the latest 
global model and CAM guidance. As the capping erodes, the 
atmosphere should become more supportive of deep convective 
development during this time period. The latest global spectral 
and CAM model guidance is supportive of storm development across 
southeast Mississippi by late afternoon, spreading into southwest 
Alabama by evening. Atmospheric conditions should become 
increasingly favorable for some severe weather threat, although 
shear especially in the lowest 1-2km will be somewhat marginal. 
Thermodynamic instability by late afternoon should increase with 
MLCAPES between 1000-1500j/kg. This instability combined with 
30-40 kts of deep layer shear should support multicell clusters of
storms capable of marginally severe wind gusts and potential for 
large hail. There will be good veering in the lowest few 
kilometers of the atmosphere, but weaker winds on the order of 
25-35kts in the 0-1km layer could limit the overall tornado 
threat. A Slight Risk for Severe Thunderstorms exists for areas 
along and west of I-65 beginning late this afternoon and 
persisting through the overnight hours.

A QLCS should form to the west of any late afternoon/early 
evening convection by later this evening in response to the 
greater mid level height falls associated with the upper trough. 
As the QLCS pushes southeast ahead of a surface cold front later 
tonight, it should gradually weaken with southeastward extent as 
the better large scale forcing lifts out to the north and deep 
layer shear weakens further. There may be an initial severe threat
across interior southeast Mississippi into southwest Alabama 
during the late evening with the squall-line, but this threat 
should diminish further south and east later in the night. The 
line should gradually slow and stretch out from southwest to 
northeast with time late tonight. This may allow for localized 
flooding to occur in areas where storms train across the same 
locations. 

The front will slowly push out over our coastal waters by later 
on Thursday with shower and thunderstorm chances diminishing from 
northwest to southeast through the day. Convection should linger 
longest across coastal counties of Alabama into the western 
Florida Panhandle where a flood threat may continue through much 
of the day. The front should eventually stall out just offshore by
Thursday evening as the mid and upper flow becomes zonal along 
the extent of the surface front. 

Moderate onshore flow will keep the threat for rip currents high 
along our area beaches through the near term forecast period. In 
addition, waves will range between 3 and 5 feet at the coast and 
result in hazardous swimming conditions for inexperienced 
swimmers. /JLH

&&

.SHORT TERM /Thursday Night Through Friday Night/...Aloft, mainly
zonal flow is expected through the short term, but several subtle
shortwaves will move along the flow during that time. At the 
surface, a stalled cold front will be draped along or just east of
the I-65 corridor by Thursday evening. This front will likely 
push offshore overnight and into early Friday morning; however, 
guidance indicates that this front will advance back north over 
our marine zones and coastal counties as a warm front Friday night
into early Saturday morning.

In terms of sensible weather, some isolated showers and a few 
storms will be possible east of I-65 as the main storm system 
discussed in the near term moves east of the local area; however, 
for the most part, a lull in shower and storm activity is expected
for many areas Thursday night. As PWATs increase once again 
through Friday afternoon (1.5-1.8 inches over southeast 
Mississippi and far southwest Alabama), anticipating rain chances 
to return. Although, coverage will remain isolated. As for any 
thunderstorms that may develop, not expecting these to be severe; 
however, they will be possible as model MUCAPE values range 
between 500-1000 J/kg and bulk shear ranges between 30-40 knots. 

With the increase in moisture on Friday, an increasing trend in 
low temperatures will take place through late week. Lows Thursday 
night will drop into the 50s over inland areas and into the lower 
60s at the coast. By Friday night, lows will merely drop into the 
60s for most areas. Meanwhile, highs Friday afternoon will warm 
into the lower 80s inland and be in the mid to upper 70s at the 
coast. Lastly, the HIGH RISK of rip currents will persist through 
Friday night. /26

&&

.EXTENDED TERM /Saturday Through Tuesday/...Another upper level 
shortwave will progress over the Southeast Saturday afternoon, 
followed by a stronger shortwave that will mover over the region 
Monday morning (although slight timing differences still exist in 
the global models). This, along with PWATs between 1.4-1.7 inches,
the aforementioned warm front (anticipated to move north over the
Gulf coast on Saturday), and another cold front that will move 
over the region from Sunday into Monday, will lead to a continued 
unsettled pattern through Easter weekend and into the first part 
of the work week. With elevated deep moisture combined with 
already saturated soils from previous rainfall, we will need to 
monitor for potential flooding concerns - especially where showers
and storms move repeatably over the same locations. Although, we 
do have good news! The second upper shortwave and surface high 
pressure building in behind the fronts on Monday will push the 
rainy and stormy weather east, leaving dry weather for the local 
area by Tuesday and into midweek next week.

High temperatures on Saturday will reach the upper 70s to lower 
80s, with a slight downward trend by Tuesday as temperatures will 
likely only top out in the 70s. Low temperatures through the 
period will follow a similar pattern, beginning in the 60s 
Saturday night and then dropping into the 50s by Monday night. /26

&&

.MARINE...Strong onshore flow in excess of 20 kts and seas 
between 5 and 7 feet will persist over our open Gulf coastal 
waters today, with 1-3 feet in the bays and sounds. A Small Craft 
Advisory remains in effect through this afternoon for all offshore
waters and including Mobile Bay and Mississippi Sound. Winds and 
seas should gradually subside later tonight as the pressure 
gradient relaxes. The flow should turn briefly offshore behind a 
stalling cold front Thursday night before returning back to 
onshore flow as the front lifts back to the north on Friday. Light
to moderate onshore flow will continue through the weekend. /JLH

&&

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

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

MS...None.
GM...Small Craft Advisory until 4 PM CDT this afternoon for 
     GMZ630>632-650-655-670-675.

&&

$$

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