Severe Thunderstorm Warning 108, NWS Birmingham, AL

Area Forecast Discussion
National Weather Service Birmingham AL
633 AM CDT Sun Jul 22 2018

.UPDATE...
For 12Z Aviation.

&&

.SHORT TERM...

Today and tonight.

Looking at the overall synoptic pattern across the area, a front is
draped across Central Alabama. Convection is limited to an outflow
boundary that moved through the area earlier Saturday evening.
Meanwhile, a large upper low is centered over the Ohio Valley and
beginning to slip down toward Tennessee. To emphasize the extent of
the upper lows impact, feeder bands into this low can be observed on
IR satellite stretching across the Atlantic and down to near Cuba.

So for today, the main upper low will begin to drift toward the
south and begin to impact northern Alabama this afternoon. The cold
front will slowly slide south at the same time. As it slides south,
it will also pivot to more of a southwest to northeast orientation,
in conjunction with the upper low. Rain chances for today will be
highest in the south ahead of the front, as well as in the northeast
as the upper low moves in. Activity will likely be more rain showers
than thunderstorms in the northeast, while activity in the south
will be mainly thunderstorms. There could be a stronger storm late
morning and into the afternoon in the southeast in advance of the
front, but severe potential remains too low to mention at this time.
Temperatures today will generally be in the 80s north of the front
and 90s south of the front.

As we move into tonight, the rain chances in the south will diminish
by Midnight, at the latest, as the front clears. Activity in the
northeast will likely continue through the night, with generally a
scattered nature. Again activity will likely be more showers with a
rumble or two of thunder. Temperatures overnight will be in the 60s
north and central, with some lower 70s in the south.

16

.LONG TERM...
Monday through Sunday.

The overall synoptic pattern doesn't change much through the first
half of this week. The strong ridging over the Southwest US persists
as the deep longwave trough is over the Eastern US. The upper low
tries to become cut-off over the Gulf States on Monday, but
eventually does get phased back in with the upper trough Tuesday
into Wednesday. Expect synoptic scale lift associated with the upper
low to provide increased rain and thunderstorm chances for Central
AL, especially the eastern two-thirds of the area. We normally don't
have this type of large-scale forcing in the summer months, so
thunderstorm coverage will be a little more widespread. Therefore, I
have gone with generally 60-70% PoPs each afternoon through
Wednesday.

Around mid-week, another strong low pressure system moves through
Manitoba and into Ontario, which acts to lift the troughing over the
Gulf States northeastward into New England. A remnant frontal
boundary will likely remain stretched southwestward along the
East Coast through the second half of the week, but models
disagree on exactly where this will become stationary. The current
GFS has the stationary boundary setting up through the
Appalachians and into Central AL, which would lead to continued
rain chances through at least Saturday or Sunday. However, the
ECMWF keeps more along the East Coast, so the best convergence is
south and east of us, allowing us to have more of a typical
summertime diurnal pattern. For now, have split the difference in
PoPs for Thursday through Sunday until we know more about where
the boundary will set up.

Temperature-wise, we should have more of a moderated daily range
considering the increased cloud cover, rain chances, and overall
cold core nature of the upper low. Towards the end of the week, I've
started a warming trend, but that will again be dependent on how the
remnant frontal boundary behaves.

25/Owen

&&

.AVIATION...
12Z TAF Discussion.

While a good portion of the area is VFR right now, two features
will provide weather to portions of the area over the next 24
hours. First a cold front will continue to slide south and east.
Until it clears, there will be a chance at seeing some
showers/storms south of the front. Added in prob30 after 21Z
through 1-2Z for MGM/TOI for this reason. Second a large upper low
will swing down and provide an increasing chance of showers/storms
for ANB/ASN after 21Z and could last as long as 3Z and possibly
longer.

16

&&

.FIRE WEATHER...

Scattered showers and thunderstorms possible this afternoon and
evening. Localized fog will be possible each morning over the next
couple of days where rainfall occurs during the previous
afternoon and evening. There are no fire weather concerns.

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     86  68  85  68  87 /  50  50  60  30  70
Anniston    87  67  85  68  87 /  40  50  60  30  70
Birmingham  89  69  87  70  88 /  10  20  50  30  70
Tuscaloosa  91  69  89  71  90 /  10  10  40  20  50
Calera      88  68  87  69  88 /  10  10  50  30  70
Auburn      87  69  86  70  87 /  40  20  60  30  70
Montgomery  92  71  90  71  91 /  40  20  60  30  70
Troy        91  70  89  70  90 /  50  30  60  30  70

&&

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

&&

Hazardous Weather Outlook
National Weather Service Birmingham AL
323 AM CDT Sun Jul 22 2018

ALZ011>015-017>050-231130-
Marion-Lamar-Fayette-Winston-Walker-Blount-Etowah-Calhoun-Cherokee-
Cleburne-Pickens-Tuscaloosa-Jefferson-Shelby-St. Clair-Talladega-
Clay-Randolph-Sumter-Greene-Hale-Perry-Bibb-Chilton-Coosa-Tallapoosa-
Chambers-Marengo-Dallas-Autauga-Lowndes-Elmore-Montgomery-Macon-
Bullock-Lee-Russell-Pike-Barbour-
323 AM CDT Sun Jul 22 2018

This Hazardous Weather Outlook is for the counties served by the
National Weather Service office in Birmingham.

.DAY ONE...Outlook through Tonight.

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Activation of storm spotters and emergency management is not
expected at this time.