Area Forecast Discussion
Issued by NWS Birmingham, AL

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FXUS64 KBMX 290833
AFDBMX

Area Forecast Discussion
National Weather Service Birmingham AL
333 AM CDT Sat Apr 29 2017

.DISCUSSION...
The main stories today will be the gusty winds and high temperatures
across Central AL. A 593 decameter 500mb high is centered just off
the Carolina coast as a 552 decameter low moves into the Texas
Panhandle through the day. This will help set up a fairly tight
surface gradient with south-southeasterly winds gusting to 20-30 mph
with locally higher gusts possible. Have issued a wind advisory
valid through the afternoon hours during peak heating when the
greatest mixing will occur. Winds will weaken during the overnight
hours and could increase again tomorrow back to advisory conditions.
Will mention this in the HWO for Sunday afternoon.

With the strong gradient and southerly winds, expect continued warm
air advection and temperatures rising to the upper 80s today with
some areas breaking the 90 degree mark by late afternoon. It`s
worth noting that the strong southerly flow will also be bringing
quite a bit of moisture with it, making those 90 degree
temperatures feel every bit of 90s degrees or higher with the heat
index. A few pop-up showers are possible across the area, with
the best chances being in the eastern half of the area. So, in
summary, today will be warm and windy, with low chance of some
isolated pop-up thunderstorms.

Taking a closer look at the system coming in on Sunday, a surface
low moves northeastward through the Central Plains and becomes
occluded as we go into Sunday afternoon. A cold front stretches down
through the Mississippi River Valley and progresses eastward into
Central AL by later in the evening and through the overnight hours
into Monday morning. Much of the convection should remain along the
frontal boundary as the 0-6km bulk shear values are roughly at 10-15
degrees relative to the orientation of the front. A strong low level
jet enhances the 0-6km bulk shear to over 40kts, while the upper
level jet remains off to the north and west. Forecast soundings show
a thin, deep layer of instability and a largely saturated profile.
The hodographs are quite impressive due to the combination of the
backed surface winds and the strong 850mb jet that becomes
southwesterly as the storms move through. This setup supports a
convective line of storms moving through that could possibly have
some breaks or bowing segments. The main threat will be damaging
winds, but brief tornadoes can`t be ruled out given the wind
profiles. Will highlight a slight risk across our entire area for
Sunday night into Monday morning. SPC has the slight risk generally
for the western two-thirds of the area with the eastern counties
under a marginal risk. Can`t argue with this either, as the exact
timing of the storms is still uncertain. However, with forecast
soundings showing the wind profiles and instability remaining
favorable into Monday morning, and a narrow corridor of higher
dewpoints building in just along and ahead of the cold front, will
carry the slight risk for the eastern counties as well. The big
question will be the timing and whether or not the front moves
out of the area before sunrise. Along with any severe potential,
heavy rain can be expected with these storms, as PWATs are
forecast to be above the maximum climatologically.

The cold front passes and surface ridging builds in Monday evening
through Wednesday. Temperatures are moderated slightly and shouldn`t
reach as warm as the past few days. Rain chances increase late
Wednesday ahead of the next system moving in. An elongated
positively- tilted trough slides south and models hint at a
surface low developing over eastern Texas and moving through the
Ozarks and into Northern Mississippi Wednesday night into
Thursday. There is still quite a bit of uncertainty with this
system as models disagree on the track of the surface low and the
orientation of the upper trough. Will continue to monitor this
system for any changes in the severe threat. Rain chances decrease
by Friday afternoon as the upper-level low moves east of the area
and cold air advection moves in on the back side of the low
bringing daytime highs Friday and Saturday down into the upper 60s
to low 70s.

25/Owen

&&

.AVIATION...
06Z TAF Discussion.

Somewhat similar conditions to last night expected overnight.
Some high clouds will be around, but expected the MVFR ceilings
developing rather quickly around 8-10z. A few spots could once
again experience IFR for a hour or so and have added some mention.
Do not think fog will be an issue anywhere tonight as the winds
will stay above 6kts at most terminals. The pressure gradient
between a high to the east and a developing low to the west will
produce gusty winds for an hour or so this evening and again on
Saturday. Winds will generally be southeast to south throughout.

75


&&

.FIRE WEATHER...

Strong gusty winds possible today and tomorrow ahead of an
approaching cold front. Rain chances remain low through Sunday
night as the cold front moves through. There are no major fire
weather concerns aside from the gusty winds. RHs will remain high.

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     88  69  86  61  74 /  20  10  10  90  40
Anniston    88  69  86  63  74 /  20  10  10  90  50
Birmingham  89  70  87  60  75 /  10  10  20  90  20
Tuscaloosa  90  70  86  58  76 /  10  10  50  90  10
Calera      88  69  86  60  76 /  10  10  20  90  30
Auburn      87  69  85  66  75 /  20  10  10  90  70
Montgomery  90  69  88  65  78 /  20  10  10  90  50
Troy        89  70  86  67  78 /  20  10  10  90  70

&&

.BMX WATCHES/WARNINGS/ADVISORIES/...
Wind Advisory from 9 AM this morning to 7 PM CDT this evening
for the following counties: Autauga...Barbour...Bibb...Blount...
Bullock...Calhoun...Chambers...Cherokee...Chilton...Clay...
Cleburne...Coosa...Dallas...Elmore...Etowah...Fayette...Greene...
Hale...Jefferson...Lamar...Lee...Lowndes...Macon...Marengo...
Marion...Montgomery...Perry...Pickens...Pike...Randolph...
Russell...Shelby...St. Clair...Sumter...Talladega...Tallapoosa...
Tuscaloosa...Walker...Winston.

&&

$$


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