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FXUS64 KBMX 250857
AFDBMX

Area Forecast Discussion
National Weather Service Birmingham AL
357 AM CDT Sat Mar 25 2017

.SHORT TERM...

Taking a peek at current radar this morning the prefrontal moistening
boundary is currently working into the area this morning. This are
may provide just a few isolated showers to the northwest. No real
impact from it at this time. Further west the main line that we will
be watching today is already fairly strong to isolated severe this
morning. Individual cells are moving northeast along the line while
the line itself is working eastward and will continue to do so
during the morning. Overall timing will put the edge of the line
into the far western counties by 9 to 10 AM and then move eastward
through the day. Showers and storms are a pretty much given for most
of the area through tonight with activity generally staying west of
an Auburn to Brundidge line during the day. Temperatures of course
will be a nightmare trying to stay on top of but the warmest will be
in the southeast where he rain holds off. If we get any more sun
than forecasted in the southeast then mid 80s can not not be ruled
out. As for temperatures in the west, look for readings to stay in
the 60s to low 70s with the clouds and rain. As the rain moves out
temperatures may warm into the low 70s in the northwest, where less
sky cover is expected. For areas in between these two areas. the
high will depend on the exact timing of the onset of the rain.
Temperatures in the forecast are based on the HRRR and then smoothed
so there could be some variability in the forecast versus the
observed temperatures.

So what about the severe potential. Most of the western half of the
area is under a slight risk, while most of the eastern half is under
a marginal threat. Main impacts will be damaging winds and possibly
some hail. Winds overall are uni-directional so not much in the way
of rotation to play with. We will also see some of the wind fields
begin to decrease during the afternoon. Lapse rates are also weak
across the area as well. So while there are some negatives to the
overall strength of the storms, there are some positives as well.
Just the pure dynamical forcing of the line itself, precipitation
loading and warm spring temperatures during the peak heating of the
day will help increase the potential of marginally severe winds with
the strongest storms, especially with any line segment bowing
observed on radar. Most of the activity will exit stage right by 7
to 8 PM tonight and the severe threat will decrease.

16

.LONG TERM...

Moist southwesterly low-level flow will remain in place on Sunday as
the upper trough takes a poleward turn toward the Ohio Valley,
causing the surface cold front to fizzle to our west. Daytime heating
will aid in the development of scattered showers and perhaps a few
thunderstorms.

The next system in the parade will move eastward from the Plains on
Monday with our next chance of storms. SBCAPE is still expected to
reach 1000-2000 J/kg with steep lapse rates spreading eastward
across MS into West AL. The compact nature of the trough should
allow a moderate amount of lift/forcing to overlap with appreciable
instability. 0-6km shear of 35-45 kt will support storm clusters and
supercells capable of producing hail possibly larger than quarter
size and damaging winds. The tornado threat continues to appear very
low due to marginal surface to 700mb shear. Convection could linger
into Tuesday morning across the North with a moist southwesterly
fetch remaining in place.

We should get a bit of a break for Wednesday as a 500 mb ridge
amplifies over the region ahead of yet another upper trough. This
system will probably carry another chance for severe storms on
Thursday and could end up being the most impressive in the series.
By this time, a large warm sector should be in place with the ECMWF
indicating the potential for CAPE in the 2000-3000 J/kg range.

87/Grantham

&&

.AVIATION...
06Z TAF Discussion.

--VFR cloudiness tonight into Saturday morning; increasing threat
of thunderstorms west-to-east through Saturday with sub-VFR impacts;
instances of breeziness--

Broken to overcast cloudiness continues overnight. Based on progged
low-level winds either side of 35-knots and RH values, ceilings are
expected to remain comfortably within VFR range.

A weather system will affect all terminals Saturday, tracking west-
to-east across the state. We should begin with spotty/VCSH showers
before a line of thunderstorms moves through. Sub-VFR conditions are
expected with the convection (visibility and/or ceilings). Given the
surface front hanging upstream, areas of lingering showers/storms
are possible beyond the end of the TAF period as well. Added an
addition line to show TSRA transitioning to SHRA. Latest model
trends have been slower with the eastward progression/development of
storm/shower activity. Adjusted timing slightly where needed.

Light to modest breezes continue tonight thanks to the pressure
gradient between upstream low pressure and ridging off the Carolina
coastline. Gusty winds are expected Saturday, with gusts to around
20kts outside of strong TS.

89/14


&&

.FIRE WEATHER...

Low level moisture will gradually increases today from west to east
as a line of strong to possibly severe storms moves across central
Alabama during the day. Rain chances will continue tonight and into
Sunday due to a moist southwest flow holding over the area. An
active weather pattern will continue into next week. Critical fire
weather conditions are not expected through the next 7 days.

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden 78 59 75 58 77 / 90 90 60 20 60
Anniston 78 59 76 59 78 / 80 90 50 20 60
Birmingham 78 60 78 60 79 / 90 80 50 20 60
Tuscaloosa 74 60 81 60 79 / 90 70 40 10 60
Calera 77 59 78 61 78 / 90 80 50 10 60
Auburn 79 58 77 59 78 / 60 70 40 10 40
Montgomery 79 60 83 61 81 / 90 90 40 10 40
Troy 79 60 81 61 82 / 60 80 40 10 30

&&

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

&&

$$
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