Area Forecast Discussion
Issued by NWS Birmingham, AL

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FXUS64 KBMX 222034

Area Forecast Discussion
National Weather Service Birmingham AL
334 PM CDT Sun Oct 22 2017

This afternoon through Tonight.

The MCV moving eastward along the Al/MS coast has stabilized the
air mass across central Alabama. The northern portion of the rain
shield has decreased considerably early this afternoon as the main
energy and lift stays near the coast. Do bot foresee any northward
transport of the more unstable air mass through this evening, and
expect little if any thunderstorm activity across central Alabama.
There could still be some isolated storms later this evening and
overnight as the main forcing associated with the upstream trof
approaches the area. Radar imagery to the west of Alabama shows
mainly scattered shower activity. This activity will likely fill
in as the short wave trof tracks eastward, so will continue with
high rain chances overnight. The cold front or wind shift should
reach the AL/MS state line near midnight and the I-65 corridor
around 3 am. The back edge of the rain should be near the surface
front. Rainfall amounts have been trimmed back considerably based
on affects from the MCV and lack of upstream convective activity.


Monday through Sunday.

Models are in better agreement with faster progression of the
upper trough on Monday. Rain should come to an end before noon,
and a mild afternoon is expected with some breaks in the clouds.
An upstream shortwave will reinforce the cold advection regime on
Tuesday into Wednesday with afternoon temperatures in the upper
50s to lower 60s in the North on Wednesday.

A transition to warmer conditions is expected on Thursday and
Friday as southerly flow develops in response to a large trough
forming in the western CONUS. Model spread is quite large on the
timing of the next front sometime in the Friday night through
Sunday timeframe. Our forecast leans more toward the slower and
more consistent ECMWF with the highest rain chances centered on
Saturday night.



18Z TAF Discussion.

Early morning MVFR cigs have become scattered as the air mass
warmed and mixing ensued. A large area of mostly light rain has
pushed into southwest Alabama ahead of a MCV over southeast
Mississippi. This rain shield will continue to track north and
eastward this afternoon, with rain likely reaching the I-65
corridor by 21z. TSRA has been confined to areas near the coast,
and for now do not anticipate any tstms at any TAF site until
after 03z. By 03z, strong forcing associated with an approaching
upper level trof will bring heavier rain and embedded tstms to all
areas, starting in the west and pushing eastward overnight. Even
though the forecast will call for prevailing 3 miles with TSRA,
vsbys will likely fall below 3 miles at times in the heavier rain
bands. The back edge of the rain will likely reach the I-65
corridor arnd 09z with near the AL/GA state line by 12z.

Cigs will be mostly above 3k feet agl thru 00z, with lcl cigs
near 2k feet agl, especially west of I-65. Cigs will transition to
IFR category by 03z across areas along and west of I-65, with IFR
cigs at all sites by 08z. Southeast sfc winds could gusts up to
20 knots until the rain shield arrives, then likely weaken as the
air mass stabilizes. The winds will gradually veer overnight and
become westerly between 09z and 12z as a cold front pushes




A cold front will move through the area tonight, providing a
widespread soaking rainfall through Monday morning. Dry through the
rest of the week. Relative humidity values should remain above
critical thresholds. There are no fire weather concerns.


Gadsden     64  67  46  66  39 / 100  70  10   0  10
Anniston    65  69  47  67  39 / 100  70  10  10  10
Birmingham  63  68  49  68  41 /  90  30  10   0  10
Tuscaloosa  61  69  49  69  41 /  80  20  10   0  10
Calera      63  68  48  67  41 /  90  30  10   0  10
Auburn      67  70  50  68  42 / 100  80  10  10  10
Montgomery  67  72  51  71  43 / 100  40  10   0  10
Troy        68  72  51  70  42 / 100  60  10   0  10




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