Special Weather Statement, NWS Birmingham, AL

Area Forecast Discussion
National Weather Service Birmingham AL
1228 PM CDT Wed Jul 5 2017

.UPDATE...
Aviation Discussion.

&&

MESOSCALE UPDATE...

12Z KBMX sounding indicates a slightly drier vertical profile from
previous days. Precipitable water value of 1.60 inches is a bit
lower from the reading 24 hours ago. The sounding profile contains
a radiation inversion around 980 mb, a subsidence inversion around
830 mb and another subsidence inversion around 540 mb. Overall,
the sounding has a drier profile from yesterday at this time and
that trend has been noted over the past 2 days. Vertical wind
profiles are unidirectional out of the southwest from above the
surface to around 550 mb followed by a more southerly component to
460 mb then transitioning to a westerly flow above 460 mb. Speeds
are fairly uniform from 15 to 30 knots through the profile. Storm
organization will be hampered by bulk shear values less than 20
knots and storm relative helicities less than 50 m2/s2 through
the 0-1 km and 0-2 km depths.

Morning surface/radar/satellite analysis indicates a continued
trend as noted yesterday of rising surface pressures across our
southeastern counties with lowest pressures across the northwest
corner of the state. WPC analyses indicate a stationary front
extending from northwest Arkansas east across northern Tennessee
where the front becomes rather diffuse.

Locally, a low-level boundary was analyzed over southern Autauga
county and extended southeast into far northern Crenshaw County
and this was drifting northeast. Another boundary was analyzed
associated with ongoing convection in west Jefferson County and
was moving northeast. A lengthy boundary extended from near
Demopolis in Marengo County northeast into central Randolph County
and was slowly lifting north-northeast.

The vertical depth of drier air generally above 830 mb will
encourage more discrete convection but will also support
evaporative cooling processes that will encourage the formation of
wet microbursts with the stronger convection. Downdraft CAPE
value around 1020 J/kg further supports this potential. The wet
microburst risk today will still be in the low category... but
looks to be toward the upper end of that range. Model-derived
storm motion projections indicate storms should move between 10 to
20 knots. The combination of slower storm motions and
precipitable water values over an inch will continue to pose a
risk for localized ponding of water and some localized flooding.

Analysis supports the ongoing forecast of best rain and
thunderstorm chances across our northwest counties with lower
chances roughly along and north of the I-20 corridor.

05

&&

Previous short-term discussion:Today and Tonight.

The overall pattern has changed little across central Alabama the
past few days. An upper ridge was located over the northern Gulf of
Mexico and an upper trof across the Mid Mississippi Valley. The
upper ridge has suppressed convection for areas south of I-20, and
this trend will continue through tonight. Scattered showers and
thunderstorms will develop during the day today for areas along and
north of I-20.  Some of the storms could be locally strong due to
steep low level lapse rates and the presence of drier air at the mid
and upper levels of the atmosphere. Temperatures will climb into the
lower to middle 90s for most of the area, and heat indices will
reach 102-105 this afternoon for areas south of a line from
Tuscaloosa to Selma line.

58/rose

.LONG TERM...
Thursday through Wednesday.

A weak surface low slides eastward through the Ohio River Valley on
Thursday, stretching a cold front down through Northern MS and
Northwestern AL. As the front and associated trough axis slowly
slide southeastward through Central AL, expect increased chances of
rain and thunderstorms. Models disagree on when the front pushes
into the area, with the GFS and EC bringing better rain chances into
the northern portions of Central AL as early as Thursday afternoon.
However, the NAM and higher-resolution CAMs keep the front back
until the overnight hours Thursday night into Friday morning.
Therefore, it comes down to timing as far as rain and thunderstorm
coverage. If the line moves in Thursday afternoon or evening, expect
more coverage north of the I-20 corridor. If the NAM and CAMs
verify, we could see more scattered coverage. Given the high
PWATs Thursday, some of these storms will be capable of producing
very heavy rainfall in a short amount of time. If convection is
able to develop Thursday afternoon/evening, dry air aloft will
lead to DCAPE values over 1000 J/Kg, so cannot rule out isolated
winds gusts of 35-45 mph near any stronger storms.

The weak frontal boundary begins to stall over the Deep South Friday
through Monday , which will lead to chances for rain and storms each
day across much of the area during peak heating. For now, have
roughly 50% coverage south of I-20 corridor Friday where the best
lift will be located. Saturday, models hint at a shortwave in the
larger scale trough moving through, which would provide enough
lift north of the stalled front, so I have included 45-50%
coverage for most of the area on Saturday. By Sunday and Monday,
the best lift, and therefore rain chances, will be limited to the
southern one-third of Central AL closer to the stalled frontal
boundary.

For Tuesday and Wednesday, southerly flow returns as the upper
trough flattens causing the previously stalled frontal boundary to
lift northward as an effective warm front. Expect scattered
afternoon thunderstorms both days with Central AL with the moist
southerly flow.

25/Owen

&&

.AVIATION...
18Z TAF Discussion.

Scattered to numerous showers and storms have developed across north
Central Alabama, and expect this activity to continue through much
of the afternoon, occasionally impacting northern terminals. Any
storm has the potential for strong wind gusts and heavy rainfall
causing brief reductions in vis.

Coverage of storms should diminish with loss of daytime heating, but
will need to monitor for activity beyond 01-02Z.

14

&&

.FIRE WEATHER...

Isolated to scattered showers and storms will be possible across the
northern half of Central Alabama through tomorrow, with rain-free
conditions across the southern half. Somewhat better rain chances
will move in Thursday due to an upper-level disturbance. There
are no fire weather concerns due to summertime humidity.

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     90  71  88  72  87 /  30  20  50  40  30
Anniston    91  72  88  72  87 /  20  10  40  40  40
Birmingham  91  73  88  74  87 /  50  20  40  40  40
Tuscaloosa  93  73  89  73  88 /  30  20  30  40  40
Calera      92  72  89  73  87 /  20  10  30  40  50
Auburn      91  72  89  72  87 /  10   0  10  30  40
Montgomery  94  73  92  75  90 /  10   0  10  30  50
Troy        92  72  90  72  88 /  10   0  10  30  50

&&

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

&&

Hazardous Weather Outlook
National Weather Service Birmingham AL
339 AM CDT Wed Jul 5 2017

ALZ011>015-017>050-061145-
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-
339 AM CDT Wed Jul 5 2017

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...Thursday through Tuesday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

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

Special Weather Statement
National Weather Service Birmingham AL
103 PM CDT WED JUL 5 2017

ALZ024-051845-
Jefferson AL-
103 PM CDT WED JUL 5 2017

...SIGNIFICANT WEATHER ADVISORY FOR NORTHEASTERN JEFFERSON COUNTY
UNTIL 145 PM CDT...

At 102 PM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from near Morris to McDonald Chapel. Movement was
northeast at 25 mph.

Winds in excess of 40 mph will be possible with these storms.

Locations impacted include...
Birmingham, Trussville, Gardendale, Irondale, Leeds, Moody,
Fairfield, Fultondale, Pinson-Clay-chalkv, Center Point, Pleasant
Grove, Clay, Pinson, Tarrant, Adamsville, Argo, Kimberly, Graysville,
Morris and Brookside.

LAT...LON 3378 8666 3377 8665 3376 8654 3374 8654
      3372 8653 3365 8653 3362 8654 3362 8655
      3356 8655 3355 8653 3354 8653 3348 8701
      3375 8684 3379 8668
TIME...MOT...LOC 1802Z 245DEG 24KT 3372 8681 3352 8694

89^GSatterwhite

Special Weather Statement
National Weather Service Birmingham AL
155 PM CDT WED JUL 5 2017

ALZ017-018-024-026-051930-
Etowah AL-Jefferson AL-St. Clair AL-Blount AL-
155 PM CDT WED JUL 5 2017

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN BLOUNT...ETOWAH...
NORTHEASTERN JEFFERSON AND ST. CLAIR COUNTIES UNTIL 230 PM CDT...

At 155 PM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from near Cleveland to Altoona to near Ashville.
Movement was northeast at 35 mph.

Winds in excess of 40 mph will be possible with these storms.

Locations impacted include...
Gadsden, Trussville, Leeds, Moody, Rainbow City, Oneonta,
Springville, Odenville, Blountsville, Cleveland, Clay, Pinson,
Attalla, Glencoe, Margaret, Argo, Ashville, Sardis City, Ragland and
Locust Fork.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Frequent cloud to ground lightning is occurring with these storms.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 3407 8594 3392 8595 3386 8600 3384 8607
      3377 8605 3368 8617 3370 8620 3367 8619
      3362 8626 3357 8645 3359 8664 3373 8666
      3383 8659 3402 8672 3408 8665 3413 8650
      3415 8636 3410 8630 3418 8619 3420 8597
TIME...MOT...LOC 1855Z 241DEG 31KT 3404 8657 3402 8631 3377 8631

89^GSatterwhite

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Special Weather Statement
National Weather Service Birmingham AL
243 PM CDT WED JUL 5 2017

ALZ015-052030-
Walker AL-
243 PM CDT WED JUL 5 2017

...SIGNIFICANT WEATHER ADVISORY FOR CENTRAL WALKER COUNTY UNTIL 330
PM CDT...

At 243 PM CDT, Doppler radar was tracking a strong thunderstorm over
Oakman, or 11 miles southwest of Jasper, moving east at 30 mph.

Winds in excess of 40 mph will be possible with this storm.

Locations impacted include...
Jasper, Cordova, Dora, Parrish, Oakman, Sipsey, Rocky Hollow,
Burnwell, Beloit, Lynns Park, Barney, West Corona, Cedrum Area, Holly
Grove, Powellville, Gamble, Corona, Townley and Boldo.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with this storm, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 3368 8706 3369 8753 3384 8753 3393 8710
TIME...MOT...LOC 1943Z 265DEG 26KT 3374 8742

89^GSatterwhite

Special Weather Statement
National Weather Service Birmingham AL
257 PM CDT WED JUL 5 2017

ALZ024-052045-
Jefferson AL-
257 PM CDT WED JUL 5 2017

...SIGNIFICANT WEATHER ADVISORY FOR NORTHEASTERN JEFFERSON COUNTY
UNTIL 345 PM CDT...

At 257 PM CDT, Doppler radar was tracking a strong thunderstorm over
Irondale, moving northeast at 15 mph.

Pea size hail and winds of 40 to 50 mph will be possible with this
storm.

Locations impacted include...
Birmingham, Mountain Brook, Trussville, Irondale, Pinson-Clay-chalkv,
Center Point, Clay, Pinson, Tarrant, Argo, Chalkville, Alton, Grayson
Valley, Birmingham Airport, Palmerdale, Village Springs, Birmingham
Race Course, Ruffner Mountain and Cloverdale.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with this storm, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 3378 8665 3377 8665 3377 8662 3373 8653
      3364 8653 3350 8668 3355 8678 3379 8667
TIME...MOT...LOC 1957Z 213DEG 14KT 3356 8670

89^GSatterwhite

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