Alert archive / Alabama / Mesoscale Discussions in 2017
Mesoscale Discussion 705
The Storm Prediction Center issued this mesoscale discussion at May 12, 2017, 10:56 AM CDT for 22 counties in Alabama. It was in force for 3 hr.
The area
The outline as issued.
The facts
- Issued
- May 12, 2017, 10:56 AM CDT (15:56 UTC)
- Expired
- May 12, 2017, 1:30 PM CDT
- In force
- 3 hr
- Issued by
- the Storm Prediction Center
- Chance of a watch
- 20%
All 22 counties
Bibb County, AL, Blount County, AL, Calhoun County, AL, Cherokee County, AL, Chilton County, AL, Clay County, AL, Cleburne County, AL, Coosa County, AL, Cullman County, AL, DeKalb County, AL, Etowah County, AL, Jackson County, AL, Jefferson County, AL, Madison County, AL, Marshall County, AL, Morgan County, AL, Randolph County, AL, Shelby County, AL, St. Clair County, AL, Talladega County, AL, Tallapoosa County, AL, Tuscaloosa County, AL
The radar
The Birmingham radar (KBMX), 65 km from the middle of the area, began a volume at 15:57 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, 3.9 hours before the alert went out and 64 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.
- Mixed-layer CAPE
- 53 J/kg
- Mixed-layer CIN
- -36 J/kg
- Mixed-layer LCL
- 835 m above ground
- 0-6 km bulk shear
- 51 kt
- 0-1 km storm-relative helicity
- -23 m²/s²
- 0-3 km storm-relative helicity
- 110 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.1
The text
As transmitted.
776
ACUS11 KWNS 121556
SWOMCD
SPC MCD 121556
GAZ000-ALZ000-121830-
Mesoscale Discussion 0705
NWS Storm Prediction Center Norman OK
1056 AM CDT Fri May 12 2017
Areas affected...Central and Northern Alabama
Concerning...Severe potential...Watch unlikely
Valid 121556Z - 121830Z
Probability of Watch Issuance...20 percent
SUMMARY...A threat for hail and marginally severe wind gusts will be
possible across parts of central and northern Alabama late this
morning into early this afternoon. Weather watch issuance appears
unlikely across central and northern Alabama this afternoon.
DISCUSSION...The latest surface analysis shows a moist airmass in
place across much of central and northern Alabama where surface
dewpoints are in the mid to upper 60s F and the RAP is estimating
MLCAPE in the 500 to 1000 J/kg range. A small cluster of
thunderstorms is ongoing in northwest Alabama just ahead of a
vorticity max moving through eastern Mississippi evident on water
vapor imagery. Large-scale ascent associated with the vort max will
help to support continued thunderstorm development in north-central
Alabama over the next few hours. In addition, the WSR-88D VWP in
northern Alabama shows 0-6 km shear of 45 kt along with some
directional shear in the lowest 2 km AGL. This could support a
marginal severe threat with the stronger multicells or weak
supercells. Hail could occur with updrafts that rotate and
marginally severe wind gusts could occur along the leading edge of
the stronger downdrafts.
..Broyles.. 05/12/2017
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...FFC...BMX...HUN...
LAT...LON 32758684 32778568 33218521 33718535 34428548 34858596
34848649 34538684 33928715 33438764 32868748 32758684SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 12, 9:56 AM CDT | Mesoscale Discussion | SPC | Washington | 3 hr |
| May 12, 10:35 AM CDT | Severe Thunderstorm Watch | SPC | Baldwin, Escambia, Mobile | 5 hr |
| May 12, 1:06 PM CDT | Mesoscale Discussion | SPC | Blount, Calhoun, Cherokee, Clay, Cleburne, Cullman and 7 more | 2 hr |
| May 12, 1:42 PM CDT | Mesoscale Discussion | SPC | Baldwin, Barbour, Butler, Coffee, Conecuh, Covington and 8 more | 108 min |
Nearby
Mesoscale Discussions in Alabama, 2017Every mesoscale discussion 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.