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Office: BMX

FXUS64 KBMX 202129
AFDBMX

Area Forecast Discussion
National Weather Service Birmingham AL
329 PM CST Tue Nov 20 2018

.SHORT TERM...
Through Tonight.

Only a few low clouds linger across northeast portions of Central
Alabama this afternoon, and those remaining clouds should be gone
by sunset. Much colder temperatures on tap tonight as north winds
usher in a colder air mass. Lows will likely fall to or just below
freezing along and north of I-20, with lower to middle 30s elsewhere.
Would not be surprised to see fog developing along the rivers and
other low lying areas.

58/rose


.LONG TERM...

Wednesday and Thursday.

High pressure will be centered near the lower Mississippi River
Valley Wednesday morning. Light northerly winds and clear skies are
forecast throughout the day as the Canadian airmass brings stable
weather across the region. The center position of anticyclonic flow
should continue an eastward progression on Thursday and begin to
effectively merge with a stronger high pressure entering into the
Great Lakes Region. This cold airmass & high are due to an
anomalous trough affecting the Northeast during this time and will
head towards the East Coast overnight Thursday. We'll also have a
transient shortwave moving across our area by then during a shift
to easterly surface winds extending from the high pressure to our
northeast. This sets the stage for cold air damming all along the
eastern edge of the Appalachians in VA/NC/SC, with some possible
effects of this moving as far southwest as GA and our northeastern
counties, though not as cold/significant. This colder and drier
air will have more of an impact on temperatures/dewpoints across
the northeast on Friday. Overall forecast outlook for Wed/Thu is
looking good with 50s/60s for afternoon highs, though some
increase in cloud cover is likely with the passing shortwave on
Thanksgiving. Still expect rain chances to be limited to the Gulf
Coast with the dry/stable airmass sticking around for the holiday.

Friday through Tuesday.

The next system will enter the picture around Friday evening as a
neutral to negatively tilted trough moves into the Great Plains by
Friday morning. Areas of rain are expected to develop in response to
synoptic scale lift from upper-level diffluent flow and positive
vorticity advection moving into our area. Rain will likely struggle
to get to the ground initially as dry air will still be in place,
especially in areas of cooler/drier air from the aforementioned cold
air damming across the northeast. Given the interaction of the
trough with the sub-tropical jet and the baroclinic zone across the
Gulf Coast, an area of low pressure should develop and pass to our
south overnight Friday and into Saturday. This feature, along with
the elongated surface trough to the north, will be the focal points
for rain activity as an axis of better moisture availability sets up
along a southerly low-level jet. Have placed increasing
coverage/intensity of rain from 12Z Friday through 12Z Saturday
before tapering off west to east overnight Saturday. Have left
out mention of thunderstorms from the grids as there are no
expectations of sufficient thermodynamic recovery ahead of this
system as the preceding easterly flow and passing shortwave on
Thursday essentially block off theta-e advection from the Gulf.

After a brief lull in activity late Saturday/early Sunday, another
more dynamic/anomalous trough is forecast to dig into the
Intermountain West. This would later eject into southern portions of
the Plains and into the lower Mississippi Valley by Sunday
afternoon. Downstream and across our forecast area, a full suite of
quasi-geostrophic lift will be available as the trough interacts
with the sub-tropical jet and develops a strong low/mid-level jet.
Resultantly, another round of rainy weather is expected Sunday
evening and into Monday. Given the synoptic setup and stronger
dynamics, low pressure will likely develop farther north near the
left exit region of the mid/upper-level jet streak and drape a
frontal boundary southward across our area. There would also be
more of an opportunity for return flow ahead of this system given
the possibility of strong cyclogenesis to the north, but that
window is narrow temporally. Nonetheless, any buoyancy provides
the possibility of thunderstorms but have left out of the forecast
as specific details as such are too uncertain this far out.
Overall, forecast expectations indicate more active weather across
our area as we head towards the weekend and early next week.

40/Sizemore

&&

.AVIATION...
18Z TAF Discussion.

A cold front has pushed southward into Northwest Florida and the
rain has moved out of Central Alabama. Two bands of cold air
strato-cumulus have developed over Central Alabama this morning.
The southern band covers areas along and south of I-85 and is
pushing southward as drier low level air moves in behind the
front. The northern band covers areas along and north of I-20.
This band has been eroding on the southern end as subsidence
increases. The northern band will likely erode by 21z with sct
conds at the northern TAF sites. The clouds will become scattered
at KMGM by 20z and a little later at KTOI. VFR conds beyond 21z at
all sites as skies become clear.

58/rose


&&

.FIRE WEATHER...

A cold front is moving southeastward across central Alabama along
with scattered light rain. The front will continue this
progression throughout the day and precede a colder and drier
airmass. No rain is forecast for Wednesday and Thursday, though
relative humidity values will remain above critical thresholds.
There are no fire weather concerns at this time.

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     31  53  33  59  38 /   0   0   0   0   0
Anniston    32  54  34  59  39 /   0   0   0   0   0
Birmingham  32  54  36  59  42 /   0   0   0   0   0
Tuscaloosa  33  56  35  60  41 /   0   0   0   0   0
Calera      33  55  34  59  40 /   0   0   0   0   0
Auburn      35  56  36  58  40 /   0   0   0   0   0
Montgomery  35  58  37  60  42 /   0   0   0   0   0
Troy        35  58  37  60  43 /   0   0   0   0   0

&&

.BMX WATCHES/WARNINGS/ADVISORIES/...
None.

&&

$$



Office: MOB FXUS64 KMOB 202202 AFDMOB Area Forecast Discussion National Weather Service Mobile AL 402 PM CST Tue Nov 20 2018 .NEAR TERM /Now Through Wednesday/...The back edge of a large area of low status in the wake of a weak cold front that moved across the region earlier today continues to shift southward towards the coast and will likely reach the coast and move offshore around sunset this evening. A weak short wave on the base of a broad upper trof over much of the eastern conus will shift east of the region and forecast area by late this afternoon leading to clearing skies combined with a light northerly wind flow near the surface this evening and overnight. For Wed a weak upper ridge builds in from the west mainly during the day on Wed proceeded by another shortwave approaching from the west overnight. With this pattern expect cool temps tonight and during the day on Wed with mostly clear skies overnight followed by mostly sunny conditions during the day on Wed. Through Wed afternoon temperatures will be generally 5 to 8 degrees below seasonal norms with lows ranging from the mid to upper 30s for most inland areas and the lower to middle 40s near the immediate coast. Highs Wed will range from the mid to upper 50s generally along and north of highway 84 and the lower 60s further south stretching to the immediate coast. 32/ee .SHORT TERM /Wednesday night Through Friday night/...A broad area of high pressure at the surface ridging southward from the Great Lakes region will keep a cool, generally dry weather pattern entrenched over the region through Thursday night. A short wave trof aloft moving though the westerly flow Wednesday night- Thursday morning time frame will increase cloud cover over the area, but aside from a few possible sprinkles along the coast any shower activity should remain south over the Gulf waters. Mostly sunny skies are expected by mid morning Thanksgiving Day with afternoon high temperatures only climbing into the low to mid 60s. A deepening low pressure system approaching from the west with strong surface high pressure ridging into the Deep South will produce a southeasterly low level flow. As a result, layer precipitable water amounts climb from around a half inch to a little over 1.5 inches during the day Friday. Precipitation is expected to spread from west to east across the forecast area Friday afternoon with categorical PoPs anticipated Friday night. A surface low looks to move eastward near the South Alabama and Western Florida Panhandle coast line Friday night. The heaviest rainfall amounts are expected near the coast with 2 to 4 inches possible by Saturday morning. The brunt of the rainfall activity will come from overrunning and embedded showers but as mentioned in previous discussions some thunderstorm activity is still possible especially near the coast. Still concerned the surface low could track a little further north than currently anticipated allowing the Western Florida Panhandle to become warm sectored, thus creating the potential for possible severe weather Friday night. The strengthening onshore flow will likely lead to a high risk of Rip currents Friday through Saturday. .LONG TERM /Saturday Through Tuesday/...Rapid clearing is expected behind the exiting front mid to late Saturday morning as the system rapidly moves eastward. A brief period of dry conditions through Saturday night into early Sunday before another low pressure system brings scattered showers and isolated thunderstorms to the area. Surface high pressure then builds in on the surface Monday with a longwave trough aloft providing for dry and cooler temperatures than normal for this time of year. /08 && .MARINE...A broad surface ridge of high pressure over the south central plains states will shift east and become reinforced from the north central gulf states to the mid Atlantic region through the Thu. A moderate to occasional strong northerly wind flow will persist over the marine area through early Thu then shift east to southeast and build later in the week in response to a vigorous upper upper level disturbance and developing surface low tracking eastward along the northern gulf coast late Fri into Sat. Showers and thunderstorms are expected with this pattern with the best coverage occurring late Fri night through late Sat morning. A few strong thunderstorms will be possible with this pattern especially from midnight Fri night through mid morning Sat. A moderate to strong west to northwest flow will follow in the wake of the low center Sat and Sat evening followed by a light to moderate northerly flow on Sun, rebuilding late Sun night into early Mon in response to a stronger cold front moving off the coast early Mon. Seas offshore will range from 2 to 4 ft through early Fri building to 4 to 6 ft late Fri into Sat. 32/ee && .PRELIMINARY POINT TEMPS/POPS... Mobile 39 60 38 61 45 65 56 69 / 0 0 0 10 0 60 90 10 Pensacola 43 61 41 61 50 65 59 70 / 0 0 0 10 10 50 90 10 Destin 46 62 45 61 52 65 62 71 / 0 0 0 10 10 30 90 20 Evergreen 37 60 35 62 43 61 53 68 / 0 0 0 0 0 40 90 20 Waynesboro 35 58 35 61 40 60 49 67 / 0 0 0 0 0 60 90 10 Camden 36 57 35 61 42 59 50 66 / 0 0 0 0 0 40 90 10 Crestview 38 62 35 61 43 63 54 71 / 0 0 0 10 0 30 90 20 && .MOB WATCHES/WARNINGS/ADVISORIES... AL...None. FL...None. MS...None. GM...None. && $$ This product is also available on the web at: http://weather.gov/mob