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FXUS64 KMOB 220513

Area Forecast Discussion
National Weather Service Mobile AL
1213 AM CDT Tue Oct 22 2019

.DISCUSSION...Updated for latest aviation discussion below.


06Z issuance...Expect a mix of MVFR and IFR ceilings to occur
overnight ahead of a cold front approaching from the northwest.
Skies are forecast to become clear around 22.12z across the 
Mobile metro area, and around 22.15z across the Pensacola metro
area in the wake of the cold front. Winds will continue from the 
south to southwest, or light and variable, ahead of the cold
front. Winds will then shift to the northwest and increase to 10 
to 15 knots in the wake of the cold front. /22


.PREV DISCUSSION... /issued 851 PM CDT Mon Oct 21 2019/ 

DISCUSSION...See updated information for land and marine areas below.

UPDATE...The convective line will move east out of the northwest
FL coastal waters shortly. With that, the severe weather threat
has ended. Given radar trends, PoPs will continue to be adjusted
downward. Highest rain chances for a bit longer reside southeast 
of I-65, but this activity will also begin decreasing in coverage
before midnight. Any late night activity will be over the eastern
zones in the form of light showers with any additional rainfall
amounts generally less than a tenth of an inch at best. Cold 
front was aligned along the Lower MS River Valley. The front 
advances eastward and makes passage during the pre-dawn hours, 
bringing drier and cooler weather in its wake. 

PREV DISCUSSION... /issued 701 PM CDT Mon Oct 21 2019/ 

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

UPDATE...7 PM: A steady and quick eastward motion to the rain
shield continues. The leading edge of the deep convection will be
moving eastward over the northwest FL coastal sections this 
evening out 60 nautical miles offshore. Instability is highest 
over the marine area where SBCAPES range from 1500 to 2500 J/KG, 
atop this instability effective bulk shear magnitudes range from 
45 to 55 knots east of the line. Considering degree of instability
and shear, appears the main threat remains over the coastal 
waters with strong to perhaps damaging wind gusts maintaining a 
threat to recreational and commercial boaters. Radar has shown a 
few weak transient rotational couplets on the leading edge of the 
marine convective line which could spawn occurrences of 
waterspouts in addition to winds in excess of 34 kts. /10

PREV DISCUSSION... /issued 616 PM CDT Mon Oct 21 2019/ 

DISCUSSION...See updated information for land areas below.

UPDATE...Back edge of rain shield is moving eastward at a fairly
fast clip around 35 kts, having moved out of interior southeast MS
zones and now crossing over southwest AL southward out of the AL
coastal waters. Forecasters will begin to taper back PoPs from
west to east given these trends. Meso-analysis shows the bulk of 
available instability (SBCAPES 1500 to 2500 J/KG being confined 
over the northwest FL Panhandle southward over the marine area. 
This is where radar shows the eastward motion of the leading edge 
of deepest convection. Given orientation of the better instability
and radar trends, the severe weather threat has been cut way back
in areal extent with slight risk lowered to a marginal risk from 
Okaloosa Co. FL westward to Baldwin Co. AL. The main impacts from 
potential of strong winds and dangerous to potentially deadly 
lightning remains over the coastal waters and perhaps closer to
the beaches. /10

PREV DISCUSSION... /issued 401 PM CDT Mon Oct 21 2019/ 

DISCUSSION...Updated for latest marine discussion below.

MARINE...A Small Craft advisory is now in effect for the open 
Gulf waters of AL and NWFL out to 60 nm including the lower end of
Mobile Bay and MS Sound east of Pascagoula beginning early 
Tue morning continuing through early Tue evening. Expect northerly
winds increasing to 18 to 23 knots in the areas with seas 
building to 4 to 6 feet offshore and around 2 feet in Mobile Bay 
and MS Sound. 32/ee 

PREV DISCUSSION... /issued 341 PM CDT Mon Oct 21 2019/ 

NEAR TERM /Now Through Tonight/...By early this evening most of
the heavier showers and thunderstorms will be over the eastern 
half of the forecast area or generally east of a line stretching 
from Thomasville to Gulf Shores in AL including all locations in 
the western FL Panhandle. Thunderstorms will continue to decrease 
in coverage and intensity mostly due to the lost of daytime 
heating and better forcing aloft that shifts off to the northeast,
though we still can't rule out a few strong storms below severe 
limits occurring mostly before midnight. By around midnight or 
shortly before a cold front begins to move into northern and 
western sections of the forecast area moving off the coast before 
sunrise. Expect a moderate northerly flow in the wake of the front
slowly diminishing after sunrise. Temperatures will range from 
the lower to middle 50s north of the front, or northern and 
western the sections of the forecast area, and the upper 50s to 
middle 60s south and east of the front which includes most areas 
generally along and east of the I-65 corridor inland and most 
locations along the immediate coast. 32/ee

SHORT TERM /Tuesday Through Thursday night/...A large upper trof,
the axis of which extends from the western Great Lakes to the 
lower Mississippi river valley, takes on a negative tilt through
Tuesday night while lifting into the northeast states.  A nearly 
zonal flow develops over the southeast states Tuesday night, then 
another upper trof amplifies over the central states through 
Thursday. A dome of cool and dry high pressure builds into the 
region through Tuesday night in the wake of a cold front which 
moved through in the NEAR TERM period. Another cold front develops
over the Plains on Wednesday in response to the central states 
upper trof, and an inverted surface trof also develops over the
far western Gulf by Thursday night. It is not clear how far
eastward the frontal boundary will be able to progress during this
evolution, though a consensus has the front making it into 
northwest Mississippi to western Louisiana by late Thursday 
night. Light northeasterly winds on Wednesday become easterly on
Thursday and continue into Thursday night as the surface high 
gradually retreats from the area ahead of the approaching front.
An overrunning southerly flow aloft sets up on Thursday and
continues into Thursday night with precipitable water values 
increasing to 1.5 to 1.75 inches. While dry conditions are 
expected through Wednesday night, this overrunning pattern and
increasing deep layer moisture will support a return of small pops
near the coast Thursday afternoon followed by likely pops for most
of the area Thursday night. Highs on Tuesday and Thursday range 
from around 70 well inland to the mid 70s over the southern 
portion of the area, and Wednesday will be a bit cooler with upper
60s well inland ranging to lower 70s elsewhere.  Lows Tuesday 
night range from the mid 40s well inland to the lower 50s at the 
coast then moderate slightly Wednesday night before milder 
temperatures follow for Thursday night with mid 50s to lower 60s 
inland ranging to mid 60s at the coast. A high risk of rip 
currents continues through Tuesday evening then a moderate risk of
rip currents follows through Thursday. /29

LONG TERM /Friday Through Monday/...There are two different potential
outcomes with the central states upper trof for Friday into 
Saturday. The first possibility is the upper trof slowly weakens 
while advancing across the eastern states, and the second is that 
a cut off upper low forms over Texas. If the cut off low 
materializes, then a surface low evolves from a western Gulf 
inverted trof and moves well north of the region, bringing a 
weakening cold front into the forecast area on Sunday which then 
stalls. Should the cut off low not develop, then the cold front 
will move through the area much earlier, on Friday. Fortunately, 
both solutions have some form of an overrunning pattern over the 
area on Friday which supports likely to categorical pops. By
Saturday, large differences develop between the potential outcomes as
dry conditions would be expected to develop if the cold front 
moves through on Friday, while otherwise some mention of pops will
be needed through the remainder of the period. Due to the
uncertainty, have gone for now with chance pops on Saturday with 
slight chance to chance pops on Sunday and Monday.  Highs on 
Friday and Saturday will be in the mid 60s to lower 70s along and 
west of I-65 and in the lower to mid 70s east of I-65. A warming 
trend ensues on Sunday, and by Monday highs will be in the mid to
upper 70s. Lows Friday night range from the lower to upper 50s 
west of I-65 to the upper 50s to lower 60s east of I-65, then 
trend gradually warmer with lows Sunday night mostly ranging from
around 60 inland to the mid 60s at the coast. /29

MARINE...A cold front will continue to approach from the northwest 
this afternoon. Ahead of the front scattered to numerous showers and 
thunderstorms can be expected with a few strong storms possible late 
this afternoon and this evening. In the wake of the front a moderate 
to strong northerly flow can be expected Tue through Wed. A moderate 
easterly flow will develop late Wed night and continue through Thu 
as a broad surface ridge of high pressure builds along the eastern 
seaboard combined with another cold front approaching from the west. 


AL...High Rip Current Risk through this evening for ALZ265-266.

FL...High Rip Current Risk through this evening for FLZ202-204-206.

GM...Small Craft Advisory from 7 AM this morning to 7 PM CDT this 
     evening for GMZ631-632-650-655-670-675.


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