Area Forecast Discussion
Issued by NWS Birmingham, AL

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303
FXUS64 KBMX 170547
AFDBMX

Area Forecast Discussion
National Weather Service Birmingham AL
1147 PM CST Mon Jan 16 2017

.UPDATE...
Aviation Discussion.

&&


...ACTIVE WEATHER INCLUDING SEVERE FOR THE END OF THE WEEK...

.SHORT TERM...

This afternoon through Tuesday Night. A smattering of cumulus,
altocumulus, and cirrus over the skies of Central Alabama this
afternoon. But there have been plenty peaks of sunshine and
southerly breezes that temperatures have jumped into the 70s in
most places. A few spots will even be in the 80s and a few records
are in jeopardy. The warm front that was parked near Central
Alabama the past few days has drifted well north and was into the
Ohio Valley. A backdoor cold front was located over Georgia and
this front will inch toward far northeastern areas. The main
effects of this front were back to the east, so do not see much
impacts here. Another cold front stretched from near Kansas City
to near Brownsville. This front will enter Central Alabama by
Tuesday afternoon and eventually stall right over the area Tuesday
night.

The model suite is in good agreement that there will be enough
moisture and lift to produce showers along and in the vicinity of
the front. Instability appears along and ahead of the front, so
did mention a chance of thunder with these showers. Pops will be
limited to far northwestern areas tonight and then eventually
cover the northern half of Central Alabama Tuesday into Tuesday
night. The best forcing and moisture do not make it into southern
areas, but a few showers are possible.

There will also a chance of fog tonight. Slightly lesser cloud
cover east and southeast will allow temperatures to drop a bit
cooler than other spots, and fog may develop. If the forecasted
low temperatures verify, so localized spots may see visibility
near 1 mile east and southeast.

Both high and low temperatures remain some 20 degrees above normal
through this period.

75

.LONG TERM...

The time frame between Thursday and Sunday will be today`s focus.
It has become prudent to introduce a severe thunderstorm
potential with the model solutions this run. Threat 1 exists Thursday
afternoon into Thursday night and Threat 2 comes Saturday night
into Sunday. All modes of severe weather are possible each period
including damaging winds, large hail, tornadoes and locally heavy
rain. At this time, the weekend system appears to be the highest
threat.

Model guidance has come a bit closer with the chaotic pattern that
we will be under Thursday through Sunday. Two rather significant
negative tilt troughs move from the southern plains into the Ohio
Valley this period. Threat 1 on Thursday, a surface low develops
in southeast Texas, deepens, and moves into the Ohio Valley by
Thursday night. Central Alabama will be see a warm surge northward
and sets us in the warm sector. Both the GFS/ECMWF develop a
decent low level jet over the top of 60 dew point/unstable air near
surface. 500mb height falls are on the order of 4-6 dam with
heights around 570dam. Sufficient shear and instability exist, but
the best lapse rates and forcing are a bit north. This warrants a
lower confidence threat at this time.

Threat 2 could potentially be a high impact event, but there still
remains some model trend issues and timing. Models are trending a
bit farther north, which puts us in the warm sector again. This
system is quite a bit stronger, with a deepening surface low into
the 990mb range. Once again, shear/instability/cold air
aloft/lapse rates all point to a severe potential.

Changes will certainly be made between now and late this week, but
be aware that there is a threat of severe storms. Analogue
guidance is about split, indicating good severe chances to low
severe chances. As with any storm system, some important mesoscale
factors remain unclear at this time and will play a role in the
storm development. Stay tuned.

75

&&

.AVIATION...
06Z TAF Discussion.

Not many changes with this aviation package. Seeing a break in cloud
cover currently, with cirrus quickly spreading back across the area
from the west. Low cigs (MVFR) starting to develop and spread
northeastward from southern MS. Seeing an occasional wind gust at
BHM and EET, and will carry prevailing gusts to 15-18kts at those
terminals.

Guidance continues to show moistening at the lowest levels across
Central Alabama around sunrise, and will show cigs progressively
falling from MVFR to IFR. Expect reductions in vis as well due to
patchy fog, but low cigs will be the primary aviation concern this
forecast period. MVFR cigs will persist through much of Tuesday
morning. Southerly winds will turn to the southwest by mid day,
increasing to 9-10kts.

A few light showers are possible overnight, but confidence in
coverage is not great enough to include at any terminal. Better
chance of showers tomorrow, ahead of an approaching front. Best rain
chances will be to the northwest of all terminals, and will hold off
on mentioning SHRA for now.

14

&&

.FIRE WEATHER...

Unseasonably mild temperatures will continue through the entire
week. Rain chances return Tuesday with a wet and chaotic pattern
setting up Wednesday through Sunday. Afternoon relative humidity
values will likely stay above 40 percent due to the southerly
winds bringing gulf moisture northward and rain.

75

&&

.CLIMATE...
Record High Temperatures (Record year)

Monday, January 16:

Anniston    75 (1949)
Birmingham  77 (1943)
Tuscaloosa  77 (1949)
Montgomery  79 (1952)
Calera 67 (2000)
Troy 68 (2013)

Tuesday, January 17:

Anniston    74 (1953)
Birmingham  79 (1943)
Tuscaloosa  75 (1990)
Montgomery  78 (1990)
Calera 70 (1999)
Troy 70 (2012)

05

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     55  70  55  65  48 /  20  50  60  40  30
Anniston    54  73  57  69  50 /  10  40  50  40  20
Birmingham  58  73  56  68  53 /  10  40  60  40  30
Tuscaloosa  58  76  57  71  54 /  20  40  50  40  30
Calera      57  74  58  70  53 /  10  30  50  40  30
Auburn      54  74  58  72  53 /  10  20  30  30  20
Montgomery  55  78  59  75  55 /  10  20  20  30  20
Troy        54  77  59  76  55 /  10  20  20  30  20

&&

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

&&

$$



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