Alert archive / Alabama / Special Weather Statements in 2017

Special Weather Statement, NWS Birmingham, AL

September 19, 2017Shelby County, Alabama

NWS Birmingham, AL issued this special weather statement at Sep 19, 2017, 3:00 PM CDT for Shelby County, Alabama. It was in force for 45 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued: Sep 19, 2017, 3:00 PM CDT (20:00 UTC)
Expired: Sep 19, 2017, 3:45 PM CDT
In force: 45 min
Issued by: NWS Birmingham, AL

County Shelby County, AL

The radar

The Birmingham radar (KBMX), 15 km from the middle of the area, began a volume at 20:00 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Birmingham, AL (KBMX), launched 12:00Z, 8.0 hours before the alert went out and 14 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 950 J/kg
Mixed-layer CIN: -34 J/kg
Mixed-layer LCL: 956 m above ground
0-6 km bulk shear: 22 kt
0-1 km storm-relative helicity: 23 m²/s²
0-3 km storm-relative helicity: 41 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.3

Open this sounding in Storm Lab

The text

As transmitted.

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What forecasters said that day

The local office's own words before this special weather statement went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Birmingham, AL wrote its last area forecast discussion before this special weather statement went out at Sep 19, 2:30 PM CDT, 30 minutes earlier.

Area forecast discussion, Sep 19, 2:30 PM CDT, 30 minutes before

Area Forecast Discussion
National Weather Service Birmingham AL
230 PM CDT Tue Sep 19 2017

.SHORT TERM...
Through Tonight.

Scattered to numerous showers and storms have developed this
afternoon across much of Central Alabama. Initial development this
morning was aided by a weak upper level shortwave moving eastward
in the nearly zonal flow aloft at 500mb. CAPE of 2500 to 3000 J/KG
and PWATs of 1.6 to 1.8 inches have aided in convective
development, especially across the northern half of Central
Alabama. Storms have been absent across eastern Alabama and
western Georgia, as a pocket of dry air is currently in place
based on GOES-16 Total PWAT product, and also the lack of cumulus
development on visible satellite. That dry air will eventually
erode as we go into the late afternoon and overnight, with rain
chances expected to be at least scattered in nature. Elsewhere,
likely rain chances will last through the rest of the afternoon
for locations roughly along and north of the I-59 corridor.

A large outflow boundary from previous strong storms in north
Alabama is currently moving southward through Winston, Walker,
Cullman, and Blount Counties. This boundary will help trigger
additional widespread storms as we go into the afternoon with
some of those being on the strong side. Gusty winds up to 40mph,
frequent cloud to ground lightning, and torrential rains can be
expected as these storms move southeastward. As is the case with
any summertime convection, we'll expect storms to decrease in
coverage and intensity fairly quickly with the loss of daytime
heating. Still, if the current cluster of storms in our northern
counties holds together there could still be decent coverage
between 6pm and 9pm tonight before diminishing.

56/GDG

.LONG TERM...
Wednesday through Tuesday.

The upper-level pattern as depicted by the GFS and ECMWF for
midweek and into the weekend has remained fairly consistent for
the past few days. A ridge forming over the Ohio Valley and Great
Lakes is still expected to trap a portion of an upper-level
trough over the Appalachians and cause this feature to move
westward across the Deep South. However, both models are
indicating a reduction in moisture quality when compared to
previous runs. Rain chances on Wednesday and Thursday have been
reduced from 40-50% to 30% mainly for the northern half of the
forecast area with northerly mid-level flow expected to cause the
advection of relatively drier air. The higher POPs will remain in
place across our southern half with models depicting PWAT values
greater than 1.5 inches.

Scattered showers and storms should continue on Friday and
Saturday as the upper-level low becomes centered over Alabama.
Sunday through Tuesday appear drier as the upper-low moves to our
west with drier air in its wake.

87/Grantham

&&

.AVIATION...
18Z TAF Discussion.

Convective coverage has increased rapidly over the past hr or so,
with scattered to numerous showers and a few storms across the
western two-thirds of Central AL. Additional development is
expected in this area this afternoon, with less coverage in the
far east where precipitable water is lower. Winds will generally
be out of the WSW around 5-7 kts.

Convection will gradually decrease with loss of daytime heating,
and dry conditions are expected area wide by later this evening.
With low-level moisture in place, mostly clear skies and calm
winds, patchy fog will be possible overnight. For now, will
maintain MVFR vis at most sites after 06-08Z, but some IFR is
possible in isolated spots. Scattered showers/storms are expected
again Wednesday afternoon.

19

&&

.FIRE WEATHER...

Scattered showers and storms and storms are expected today across
much of the area. A similar pattern will continue for the next
several days. There are no fire weather concerns.

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     67  87  67  88  67 /  50  30  20  30  20
Anniston    68  87  69  87  67 /  40  30  20  30  20
Birmingham  70  88  70  88  69 /  50  30  20  30  20
Tuscaloosa  71  90  71  91  70 /  50  30  20  30  20
Calera      70  88  70  88  69 /  50  30  20  30  20
Auburn      70  87  69  88  69 /  30  40  20  30  20
Montgomery  72  90  71  91  71 /  40  40  20  40  20
Troy        70  89  69  89  69 /  40  40  20  40  20

&&

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

&&

Hazardous weather outlook, Sep 19, 4:18 AM CDT, 10 hours 42 minutes before

Hazardous Weather Outlook
National Weather Service Birmingham AL
418 AM CDT Tue Sep 19 2017

ALZ011>015-017>050-201230-
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-
418 AM CDT Tue Sep 19 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...Wednesday through Monday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

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

In the hours before

Special weather statement, Sep 19, 2:16 PM CDT, 44 minutes before

Special Weather Statement
National Weather Service Birmingham AL
216 PM CDT TUE SEP 19 2017

ALZ017-192015-
Blount AL-
216 PM CDT TUE SEP 19 2017

...SIGNIFICANT WEATHER ADVISORY FOR NORTHEASTERN BLOUNT COUNTY UNTIL
315 PM CDT...

At 215 PM CDT, Doppler radar was tracking a strong thunderstorm near
Holly Pond, or near Blountsville, moving east at 20 mph.

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

Locations impacted include...
Oneonta, Blountsville, Cleveland, Snead, Susan Moore, Walnut Grove,
Nectar, Rosa, McLarty, Strawberry, Brooksville, Chamblees Mill,
Fowler Spring and Hendrix.

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 3421 8641 3410 8630 3394 8641 3400 8675
      3403 8672 3403 8670 3406 8671 3405 8668
      3408 8670 3409 8669 3408 8669 3409 8666
      3411 8665 3412 8663 3412 8660 3415 8659
      3419 8655 3420 8655 3425 8651 3426 8645
TIME...MOT...LOC 1915Z 284DEG 17KT 3412 8667

89^GSatterwhite

Special weather statement, Sep 19, 2:22 PM CDT, 38 minutes before

Special Weather Statement
National Weather Service Birmingham AL
222 PM CDT TUE SEP 19 2017

ALZ014-015-192015-
Walker AL-Winston AL-
222 PM CDT TUE SEP 19 2017

...SIGNIFICANT WEATHER ADVISORY FOR NORTHEASTERN WALKER AND
SOUTHEASTERN WINSTON COUNTIES UNTIL 315 PM CDT...

At 222 PM CDT, Doppler radar was tracking a strong thunderstorm over
Falls City, or near Arley, moving east at 20 mph.

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

Locations impacted include...
Arley, Curry, Smith Dam, Smith Lake, Falls City, Mill Branch, Panther
Branch, Maple Branch, Wilson Bend, Devils Branch, Seymour Branch,
Duncan Bridge, Little Dismal Creek, Yellow Creek, Bear Branch, Little
Bear Branch, Coon Creek, Raccoon Branch, Powellville and Big Bear
Branch.

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 3399 8711 3399 8715 3397 8714 3396 8711
      3394 8710 3392 8708 3391 8708 3390 8710
      3389 8709 3392 8726 3399 8738 3411 8725
      3412 8711
TIME...MOT...LOC 1922Z 284DEG 17KT 3404 8721

89^GSatterwhite

Special weather statement, Sep 19, 3:00 PM CDT, 0 minutes before

Special Weather Statement
National Weather Service Birmingham AL
300 PM CDT TUE SEP 19 2017

ALZ025-192045-
Shelby AL-
300 PM CDT TUE SEP 19 2017

...SIGNIFICANT WEATHER ADVISORY FOR WEST CENTRAL SHELBY COUNTY UNTIL
345 PM CDT...

At 300 PM CDT, Doppler radar was tracking a strong thunderstorm over
Helena, moving east at 15 mph.

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

Locations impacted include...
Hoover, Alabaster, Pelham, Helena, Indian Springs Village,
Riverchase, Oak Mountain State Park, Maylene, Oak Mountain
Amphitheater, Joe Tucker Park, Ballantrae, Saddle Lake Farms, Siluria
and Saginaw.

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 3332 8668 3326 8667 3321 8676 3320 8686
      3324 8693 3327 8694 3328 8693 3330 8693
      3330 8692 3331 8690 3333 8687 3333 8683
      3335 8683 3336 8682 3337 8676
TIME...MOT...LOC 2000Z 256DEG 11KT 3329 8684

89^GSatterwhite

The office that day

Everything else NWS Birmingham, AL issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Sep 19, 2:16 PM CDT	Special Weather Statement	BMX	Blount	59 min
Sep 19, 2:22 PM CDT	Special Weather Statement	BMX	Winston	53 min
Sep 19, 3:10 PM CDT	Special Weather Statement	BMX	St. Clair	50 min
Sep 19, 4:05 PM CDT	Special Weather Statement	BMX	Calhoun	40 min
Sep 19, 4:51 PM CDT	Special Weather Statement	BMX	Cleburne	39 min
Sep 19, 4:57 PM CDT	Severe Thunderstorm Warning	BMX	Calhoun, Cleburne	19 min
Sep 19, 5:29 PM CDT	Areal Flood Advisory	BMX	Clay, Talladega	2 hr
Sep 19, 6:25 PM CDT	Special Weather Statement	BMX	Elmore	35 min
Sep 19, 6:32 PM CDT	Special Weather Statement	BMX	Bullock	43 min
Sep 19, 6:59 PM CDT	Severe Thunderstorm Warning	BMX	Elmore, Macon, Tallapoosa	46 min

Nearby

Special Weather Statements in Alabama, 2017 Every special weather statement in 2017

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.