Special Weather Statement, NWS Birmingham, AL

Area Forecast Discussion
National Weather Service Birmingham AL
1151 PM CDT Sat Apr 6 2019

.UPDATE...
For 06Z Aviation.

&&

.SHORT TERM...
Through Tonight.

This afternoon, we have a stationary boundary stretched across
the far southern portions of Central Alabama. In the upper levels,
there is a trough dipping from the Central Plains and back into
North and West Texas. Southwest flow is present across Central
Alabama generally with a shifting to zonal flow as it progresses
into Georgia. Shortwave ripples are moving through this flow this
afternoon with shower and thunderstorm activity developing along
and south of the stationary boundary. Dew points are elevated with
a moist atmosphere in place. The northern counties have been
relatively quiet today, but that is expected to change overnight.
The upper trough will nudge to the east through tonight and allow
for the stationary boundary to push northward some as a warm
front. A more significant shortwave is expected to move through
the upper flow across the North Mississippi, North Alabama, and
into Tennessee. So, the axis of higher convection chances will
shift from the southern half to the northern half of Central
Alabama as we progress through tonight in response. With the
boundary expected to push northward, along with elevated rain
chances and considerable cloud cover, temperatures should be a
touch milder for lows tonight. Strong storms remain possible
across the area through tonight as mentioned in mesoscale
discussion below.

08

Previous Mesoscale Discussion from 914 AM CDT Sat Apr 6 2019

(1) Potential for thunderstorms that may produce strong winds and
hail across our south-central counties late this morning through
this evening.

(2) Potential for thunderstorms that may produce damaging winds
and hail across our north-central counties this evening through
very early Sunday morning.

(1) Late this morning through early this evening (south-central):

A warm front is currently positioned roughly along the U.S.
Highway 80 corridor from near Demopolis east to near Auburn. This
feature is forecast to continue to lift northward across our
forecast area today and tonight. With the passage of the warm
front, low-level temperatures and humidity values will increase
and this will result in increasing instability values through the
afternoon and into the early evening hours.

Impacts midday through this evening generally south of the
Interstate 59 corridor will be with strong convection capable of
producing hail and strong winds.

Most model forecast soundings indicating surface-based convective
available potential instability (CAPE) values in the 2000-3000
J/kg range with ample instability within the hail growth zone.

As depicted in this morning's 06/12Z BMX sounding a significant
dry layer exists just above a subsidence inversion near 850 mb.
The dry layer aloft is contributing to downdraft CAPE values over
700 J/kg which is quite indicative for downburst/microburst
potential with the stronger convection.

Convection is already developing across far interior southwest
Alabama and convection-allowing models (CAMs) are indicating
further development and intensification from the 10 am to noon
time frame most likely across our southwest counties and expanding
east/northeast with time. Convection will gradually build
northward behind the advancing warm front that will continue to
lift northward this afternoon and evening.

(2) This evening through early Sunday morning (north-central):

A sharp upper-level trough is over west Texas at this hour and is
supporting deepening convection that will continue to move east
into Louisiana/Arkansas generally after 19z. This activity is
forecast to grow upscale into a mesoscale convective system (MCS)
as it continues to advance east-northeast, likely entering north-
central Mississippi generally after 23z.

Ongoing convection across our southern counties is expected to
persist near and behind the northward advancing warm front posting
a risk for hail/strong winds. The MCS will advance east across the
northern half of Mississippi and is forecast to enter northwest
Alabama generally after 01z. The MCS will ride eastward across the
northern half of the state roughly along the warm front tonight
into very early Sunday morning. Damaging winds will be the primary
risk from this activity with potential for some hail in the
stronger convection.

We will monitor convective trends over the next several hours
along with evaluating newer model data coming in later this
morning. Keep close to a good source of weather information for
updates to the forecast through the afternoon and evening hours.

05

.LONG TERM...
Sunday April 7 through Sunday April 14.

The southern stream trough will only slowly move eastward across
Texas on Sunday, as it will be cut off from the stronger
westerlies of the northern stream. Dry air will be present at
mid-levels, with 850-700mb mean RH values falling below 50%. This
combined with the influence of ridging over Florida suggests that
diurnal convection will be largely suppressed during the day on
Sunday, so PoPs have been lowered. But will need to monitor for
any outflow boundaries from a potential convective complex
developing near the Delta region of Mississippi. Highs will be in
the low to perhaps middle 80s. Rain chances will begin to return
Sunday night as height falls develop ahead of the trough and a
surface low begins to develop over the ArkLaTex. An MCS is likely
to form over Louisiana. Models seem to be trending towards this
MCS being more north-south oriented rather than oriented along the
coast. It appears that this MCS will move into our western
counties after midnight Sunday night, and more likely after 3 AM.
Severe potential with this MCS is unclear, but appears to be very
limited with weaker instability during that time of the day, and
it will be displaced eastward of the better forcing. Therefore,
confidence is too low to mention any severe storms for late Sunday
night at this time.

This potential MCS will likely play a large role in determining
any severe weather potential for Monday. The most likely scenario
appears to be that it would move through during the morning
hours, possibly posing a marginal threat of severe weather, and
contaminate the warm sector and decrease the mid-level lapse
rates, limiting the potential for air mass recovery and preventing
more than a marginal risk of severe weather with new storms
developing along the cold front further west within a mid-level
dry slot. However if it weakens or dissipates, or if enough
daytime heating occurs behind it then a greater risk for severe
storms could materialize. For now, the best course of action
appears to be to add an areawide marginal risk of damaging winds
to the HWO for Monday with a broad time window, and monitor for
any potential upgrades. The tornado potential for Monday is
unclear as models have varied from run to run and between each
other regarding the magnitude of both deep layer and low-level
shear. For example, yesterday's runs of the ECMWF had a stronger
surface low while tonight's run trended weaker. The low also
appears to be vertically stacked. So, will hold off on mentioning
a tornado threat in the HWO at this time. Ultimately there will
be several rounds of convection across the southern CONUS between
now and then which will determine what kind of environment is
present by then.

Rain chances will linger into Tuesday as the vertically stacked
low swirls overhead. A rumble or two of thunder will remain
possible given cool air aloft. The system finally moves eastward
with dry conditions expected for Tuesday night and Wednesday.

A potent shortwave trough will reach the central CONUS by
Thursday. A powerful 985mb surface low will bring the potential
for a significant late season winter storm for the Upper Midwest.
Closer to home, moisture return will be limited with dew points
barely reaching 60F. Warm air aloft will also result in some
capping. The strong wind fields will probably result in a
strongly forced squall line developing from the Great Lakes
southward Thursday night. This could result in a damaging wind
threat across our northern counties depending on the southern
extent of the squall line, but it remains unclear whether or not
it will reach this far south.

The GFS is more aggressive than the ECMWF with a frontal passage
into the Gulf behind this system. This will likely play a role in
moisture quality for a potential threat for severe storms with
another system next weekend as the pattern remains active, but
confidence in any details remains low at this time.

32/Davis

&&

.AVIATION...
06Z TAF Discussion.

Quasi-stationary front was located very close to MGM/TOI with
another boundary just north of our northern terminals. Several
areas of convection moved through Central Alabama the past 6 hours
or so. Much of the activity has lost its intensity and have only a
mention of VCTS at ASN/ANB for the next hour or so. Southerly flow
and increased moisture will make ceilings redevelop overnight.
Expect conditions close to what we experienced last night. Within
a few hours, MVFR ceilings and some light fog develop. Then
another drop to IFR ceilings. A few spots north were a bit lesser
confidence and got Tempo groups. The ceilings rise to MVFR 15-16z
and then VFR by afternoon. Thunderstorms should much lesser in
coverage on Sunday, but may increase toward the end of the period.
Winds will gain and east southeast component and then a southerly
shift Sunday afternoon south. Winds remain 7-8kts or less.

75

&&

.FIRE WEATHER...

Lesser thunderstorm coverage expected on Sunday but moisture
values do increase. Therefore, rh values remain high. Showers and
thunderstorm chances increase Sunday night and Monday as more
convective systems affect the area. Winds remain below 8kts
outside convection the next few days.

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     62  81  63  73  60 / 100  20  30  90  60
Anniston    63  82  64  75  61 / 100  20  30  80  60
Birmingham  63  81  65  74  61 / 100  20  40  90  60
Tuscaloosa  64  80  66  74  60 /  80  20  80  90  50
Calera      63  81  65  73  61 / 100  20  40  90  60
Auburn      62  81  64  75  62 /  90  30  30  80  60
Montgomery  65  83  65  77  63 /  20  30  30  80  50
Troy        65  82  65  76  63 /  20  30  30  80  50

&&

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

&&

Hazardous Weather Outlook
National Weather Service Birmingham AL
1203 AM CDT Sun Apr 7 2019

ALZ011>015-017>050-080815-
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-
1203 AM CDT Sun Apr 7 2019

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

.DAY ONE...Overnight.

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

There is a marginal risk of severe storms Monday and Monday night
across all of Central Alabama. At this time the main threat appears
to be damaging winds. This forecast may change so stay tuned for
future updates.

.SPOTTER INFORMATION STATEMENT...

Activation of storm spotters and emergency management may be needed
this evening, and again on Monday.

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BIRMINGHAM AL
943 PM CDT SAT APR 6 2019

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0800 PM     HAIL             3 WNW NATURAL BRIDGE    34.10N 87.65W
04/06/2019  E1.75 INCH       MARION             AL   PUBLIC

&&

MAL

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BIRMINGHAM AL
956 PM CDT SAT APR 6 2019

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0948 PM     HAIL             LINCOLN                 33.61N 86.12W
04/06/2019  E0.70 INCH       TALLADEGA          AL   PUBLIC

&&

MAL

Special Weather Statement
National Weather Service Birmingham AL
1004 PM CDT SAT APR 6 2019

ALZ018>021-027>029-070400-
Calhoun AL-Etowah AL-Clay AL-Talladega AL-Randolph AL-Cleburne AL-
Cherokee AL-
1004 PM CDT SAT APR 6 2019

...SIGNIFICANT WEATHER ADVISORY FOR CENTRAL TALLADEGA...RANDOLPH...
CALHOUN...ETOWAH...CLEBURNE...CHEROKEE AND CLAY COUNTIES UNTIL 1100
PM CDT...

At 1004 PM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from near Aurora to Bynum to near Sycamore. Movement
was east at 50 mph.

Half inch hail and winds in excess of 40 mph will be possible with
these storms.

Locations impacted include...
Gadsden, Anniston, Oxford, Talladega, Sylacauga, Jacksonville,
Rainbow City, Roanoke, Attalla, Piedmont, Hokes Bluff, Centre,
Heflin, Lineville, Ashland, Cedar Bluff, Wedowee, Cobb Town, Fort
McClellan and Saks.

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.

To report severe weather, contact your nearest law enforcement
agency. They will relay your report to the National Weather Service
office in Birmingham.

&&

LAT...LON 3337 8528 3311 8543 3310 8633 3359 8599
      3376 8606 3377 8604 3385 8605 3390 8613
      3415 8624 3420 8610 3420 8584 3424 8584
      3429 8546
TIME...MOT...LOC 0304Z 267DEG 44KT 3406 8619 3358 8594 3320 8614

40/Sizemore

Special Weather Statement
National Weather Service Birmingham AL
1116 PM CDT SAT APR 6 2019

ALZ036-043-070500-
Coosa AL-Elmore AL-
1116 PM CDT SAT APR 6 2019

...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN ELMORE AND
SOUTHEASTERN COOSA COUNTIES UNTIL MIDNIGHT CDT...

At 1116 PM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from Rockford to near Titus. Movement was east at 30
mph.

Pea size hail and winds in excess of 40 mph will be possible with
these storms.

Locations impacted include...
Rockford, Kellyton, Equality, Eclectic, Lyle, Pentonville, Santuck,
Cottage Grove, Titus, Bentleyville, Welona, Moriah, Ten Cedar
Estates, Nixburg, Dexter, Speed, Weoka Mills, Jordan Lake, Highway 9
and Highway 22 and Crewsville.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

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 3279 8601 3276 8601 3261 8605 3263 8641
      3275 8641 3275 8638 3277 8640 3299 8638
      3299 8601 3282 8601 3280 8600
TIME...MOT...LOC 0416Z 270DEG 25KT 3289 8621 3269 8639

32/Davis

Special Weather Statement
National Weather Service Birmingham AL
105 AM CDT SUN APR 7 2019

ALZ038-070645-
Chambers AL-
105 AM CDT SUN APR 7 2019

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHWESTERN CHAMBERS COUNTY
UNTIL 145 AM CDT...

At 105 AM CDT, Doppler radar was tracking a strong thunderstorm over
Waverly, or 8 miles southeast of Camp Hill, moving northeast at 15
mph.

Half inch hail and winds in excess of 40 mph will be possible with
this storm.

Locations impacted include...
Waverly, Cusseta, Oak Bowery, Sturkie and West Chambers.

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 3273 8540 3274 8541 3274 8543 3273 8543
      3273 8548 3274 8549 3273 8549 3273 8557
      3274 8557 3273 8558 3273 8559 3278 8559
      3290 8548 3278 8529
TIME...MOT...LOC 0605Z 231DEG 15KT 3274 8553

32/Davis

Special Weather Statement
National Weather Service Birmingham AL
121 AM CDT SUN APR 7 2019

ALZ047-070700-
Lee AL-
121 AM CDT SUN APR 7 2019

...SIGNIFICANT WEATHER ADVISORY FOR NORTHERN LEE COUNTY UNTIL 200 AM
CDT...

At 121 AM CDT, Doppler radar was tracking a strong thunderstorm over
Auburn University, or over Auburn, moving northeast at 25 mph.

Half inch hail will be possible with this storm.

Locations impacted include...
Auburn, Opelika, Beulah, Beauregard, Beans Mill, Auburn University,
Bleecker, Robert G. Pitts Airport, Mount Jefferson and Bartletts
Ferry Dam.

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 3249 8544 3250 8544 3272 8557 3274 8549
      3273 8543 3274 8543 3274 8541 3273 8540
      3273 8529 3275 8528 3275 8514 3274 8511
      3270 8512 3267 8509 3265 8509 3265 8511
      3263 8508 3262 8509 3261 8508
TIME...MOT...LOC 0621Z 242DEG 24KT 3261 8548

32/Davis