MOB issues Area Forecast Discussion (AFD) at Dec 9, 3:43 PM CST ...New NEAR TERM, SHORT TERM, LONG TERM, MARINE...
422
FXUS64 KMOB 092143
AFDMOB
Area Forecast Discussion
National Weather Service Mobile AL
343 PM CST Mon Dec 9 2024
...New NEAR TERM, SHORT TERM, LONG TERM, MARINE...
.NEAR TERM...
(Now through Tuesday)
Issued at 343 PM CST Mon Dec 9 2024
09.12Z upper analysis shows the deep south under a west/southwest
flow at high levels in the geopotential height fields with short-
wave energy passing out of LA and expected to deamplify the
remainder of the day as it lifts across central MS/AL. At the
surface, we are warm sectored south of a better defined, but
quasi-stationary front draped from the Red River Valley of TX/OK
to the Mid MS River Valley. A weak surface trough was oriented
from southern MS, southwest to across southeast to south-central
LA. Along this surface trough, a zone of precipitable water values
from 1.4 to 1.8 inches was aligned and considering the
intersecting surface boundary and the mid level impulse passage
riding east northeast in the flow aloft provides enough ascent to
keep the local area unsettled. Radar shows a fairly solid area of
rains streaming east northeast mainly along and west of I-65.
Little in the way of thunder at present time within the rain band
as radar returns are stratiform/low topped considering little to
no instability as mid level lapse rates are around 5.5 C/KM and
little to no convective available potential energy (CAPE). There
is however a bit of instability (Surface Based Cape at 500-1000
J/KG) poking up into the western FL Panhandle which is lending
credence of thunder support so will be watching this area. Some of
the rains moderate to locally heavy, but with higher intensity
drought and elevated flash flood guidance, forecasters will hold
off on issuance of a larger areal flash flood watch. Feel any
flooding issues coming from higher rainfall rates => runoff will
be isolated and confined to areas subject to poor drainage. Since
midnight, several observations primarily over southeast MS and
interior southwest AL already have received 1 to 2 inches.
Flow aloft changes little tonight with moisture axis aligned
northeast to southwest from the southern Carolinas to off the LA
coast. There is a signal in the latest short range ensembles of
patchy fog development overnight and have included this in the
gridded forecast. There is also indications in the guidance that
coverage of precipitation lowers a bit by late evening before
trending back up by daybreak and into the day Tuesday as upper
trough begins to sharpen over the Plains down into TX causing
upper level support/ascent to increase along a southeastward
moving cold front. The front approaches the western zones by late
in the day Tuesday and will make passage across the I-65 corridor
Tuesday night. The better coverage of showers and storms will
shift east of I-65 by late Tuesday night/early Wed AM with the
frontal passage. May see a mix of thunder within the larger
coverage of warm sector showers Tuesday and Tuesday night as a
narrow low level H85 jet strengthens combined with 0-6km bulk
shear magnitudes increasing to 40 to 60 kts. Instability is mostly
weak considering degree of cloud cover/rain. Parameters appear to
be a bit out of phase amongst solutions but enough will be
present for a Marginal Risk of a sub-severe storm or very
isolated, brief severe storm here and there with a strong to
isolated damaging wind gust threat being the main impact in any of
those. Still could also see some moderate to locally heavy
downpours and potential isolated water issues in areas subject to
poor drainage.
Temperatures will be mild and well above normal by December
standards with highs Tuesday in the lower to mid 70s interior to
mid 70s coast. Lows will also be mild and well above normal
tonight in the lower to mid 60s interior to mid 60s coast. Lows
trend colder Tuesday night as cold air advection arrives in the
wake of the frontal passage, 37 to 42 northwest of I-65 to mid
40s east of the Interstate, southward to the coast. /10
&&
.LONG TERM...
(Wednesday through Monday)
Issued at 343 PM CST Mon Dec 9 2024
A large upper trough continues to push across the eastern CONUS to
start the period with a surface cold front marching its way
through the forecast area early Wednesday morning. Any lingering
showers and storms will quickly shift east of the area mid to late
morning with dry, cold air working its way into the area. Surface
high pressure slides into the region keeping things dry through
Friday in the cold fronts wake. Heading into the weekend, another
upper trough approaches the region and high pressure shifts east
putting us back into a warm air advection regime. Rain chances
will be on the increase again as we head into the weekend with
isolated to scattered coverage each day, best chances on Saturday.
The next upper trough approaches by the beginning of next week
which will likely bring another increase in rain chances.
Temperatures follow a similar roller coaster with highs in the
50's and lows in the upper 20's and lower 30's through Thursday
night. Temperatures warm back to near seasonable norms in the
lower to middle 60's over the weekend and lows in the 40's over
the interior and 50's nearer the coast. A Low risk of rip currents
will exist Wednesday through Friday. MM/25
&&
.MARINE...
Issued at 343 PM CST Mon Dec 9 2024
Short range ensembles indicate elevated probabilities of advective
type fog over Mobile Bay where warmer, moist southerly flow
characterized by dewpoints 65-70 degrees is over-riding cooler
bay temperatures 54-59 degrees. Have noticed some mixing
out/improved visibilities at time of writing but expect
restrictions to lower after dark again. Dense fog advisory remains
in effect until 6 AM Tue and could be expanded for the remainder
of Mobile Bay. Considering high confidence of increasing
northwesterly flow to small craft advisory criteria in the wake of
a strong frontal passage Tue night, small craft advisories have
been posted and will continue into Wed for Mobile Bay, out across
the open Gulf. Seas markedly higher Tuesday night into Wednesday
with highest seas 6, to perhaps 9 feet in the 20 to 60 NM zones
considering the northwesterly fetch. We may see a brief window
where wind gusts could increase to gale force and will continue to
monitor over the next couple shifts for a possible upgrade to the
advisory. /10
&&
.PRELIMINARY POINT TEMPS/POPS...
Mobile 63 74 43 55 33 56 38 61 / 80 90 90 20 0 0 0 10
Pensacola 66 75 47 57 38 56 43 62 / 90 80 100 40 0 0 0 10
Destin 67 76 50 60 40 57 45 63 / 90 80 100 60 0 0 0 0
Evergreen 61 74 42 53 31 55 33 60 / 80 90 100 20 0 0 0 0
Waynesboro 62 72 38 54 30 54 34 60 / 60 90 60 0 0 0 0 0
Camden 61 70 39 52 30 53 33 59 / 60 90 90 20 0 0 0 0
Crestview 62 77 44 55 30 56 34 62 / 90 80 100 40 0 0 0 0
&&
.MOB WATCHES/WARNINGS/ADVISORIES...
AL...None.
FL...None.
MS...None.
GM...Dense Fog Advisory until 6 AM CST Tuesday for GMZ630.
Small Craft Advisory from midnight Tuesday night to 3 PM CST
Wednesday for GMZ630>632.
Small Craft Advisory from midnight Tuesday night to midnight CST
Wednesday night for GMZ650-655-670-675.
&&
$$
This product is also available on the web at:
www.weather.gov/mob
Source: MOB issues Area Forecast Discussion (AFD) at Dec 9, 3:43 PM CST ...New NEAR TERM, SHORT TERM, LONG TERM, MARINE... (https://mesonet.agron.iastate.edu/p.php?pid=202412092143-KMOB-FXUS64-AFDMOB)
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