Area Forecast Discussion
Issued by NWS Birmingham, AL

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FXUS64 KBMX 252337
AFDBMX

Area Forecast Discussion
National Weather Service Birmingham AL
637 PM CDT Tue Apr 25 2017

.UPDATE...
For 00Z Aviation.

&&

.SHORT TERM...
Through Wednesday night.

The departing surface low along the east coast, and resultant
surface ridging along the Gulf coast, will help keep conditions
dry in the short term. A small bump up in upper level heights will
also allow the warming trend to continue through Wednesday as
well.

Our next good chance of rain still appears to be on track for
Wednesday night into early Thursday. A rather strong shortwave
trough is forecast to round the base of the longwave trough, and
12z models have this feature swinging across the Ohio and TN
valleys in the 00z to 12z Thursday time frame. Looks like the
associated surface cold front should get to the western counties
of central Alabama around midnight Wednesday night, and reach the
I-65 corridor by 12z.

Based on latest model output, will maintain the low confidence
mention of severe storms in the HWO for both late Wednesday into
Thursday, associated with this system. Time of day factors a lot
into the lower confidence in this case, as the predawn to early
daylight hours are typically not the most conducive times for
severe weather (from a climo standpoint). As one would expect,
instability levels are forecast to wane from the higher values the
lower MS valley will likely get Saturday afternoon, by the time
the line of showers/storms gets here. Regardless of severity,
high POPs certainly seem justified as this system quickly pushes
through.

NOTE: based on 12z model runs, we also added a low confidence (1)
mention of a tornado threat for Sunday.

/61/

.LONG TERM...
Thursday through Tuesday.

The cold front stalls across Central AL towards the end of the day
Thursday and into Friday before being lifted northward as a warm
front in the afternoon on Friday. This could produce some scattered
thunderstorms during peak heating on Friday in our northern
counties. Another longwave trough digs into the Central US Friday
as a surface low develops over the Southern Plains and tracks
northeastward into the Upper Midwest over the weekend. Models have
been going back and forth on the timing as a cold front stretches
down through the Mississippi River Valley and pushes eastward
across Central AL. Current runs have front pushing through Sunday
afternoon into Sunday night. The GFS has a shortwave pulse coming
out of the base of the trough, resulting in more shear. However,
the ECMWF doesn`t have as much shear across Central AL.

Low level ridging builds in behind the frontal passage Monday night
into Tuesday, resulting in clearing skies, dry weather, and near-
normal temperatures.

25/Owen

&&

.AVIATION...
00Z TAF Discussion.

Light/calm winds expected overnight under clear skies. With drier
low levels, do not anticipate any fog development. Southerly winds
will increase to 10+ kts on Thursday with gusts up to 20 kts. This
is due to a tightening pressure gradient as a frontal system
approaches from the west.

19

&&

.FIRE WEATHER...

High pressure will keep conditions dry through Wednesday. An
approaching cold front will bring a round of showers and
thunderstorms to central Alabama Wednesday night into Thursday.

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     53  84  62  81  60 /   0   0  50  60  10
Anniston    55  83  62  81  63 /   0   0  30  60  10
Birmingham  59  85  65  81  65 /   0   0  50  60  10
Tuscaloosa  57  85  63  82  63 /   0   0  60  50  10
Calera      57  84  64  82  65 /   0   0  50  60  10
Auburn      58  82  63  80  67 /   0   0  20  60  10
Montgomery  58  86  66  85  68 /   0   0  30  60  10
Troy        57  84  65  82  68 /   0   0  20  60  10

&&

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

&&

$$


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