Alert archive / Alabama / Mesoscale Discussions in 2017

Mesoscale Discussion 417

April 3, 201712 counties in Alabama

The Storm Prediction Center issued this mesoscale discussion at Apr 3, 2017, 7:45 AM CDT for 12 counties in Alabama. It was in force for 90 min.

The area

The outline as issued.

The facts

Issued: Apr 3, 2017, 7:45 AM CDT (12:45 UTC)
Expired: Apr 3, 2017, 9:15 AM CDT
In force: 90 min
Issued by: the Storm Prediction Center

Counties Barbour County, AL, Bullock County, AL, Chambers County, AL, Coosa County, AL, Elmore County, AL, Lee County, AL, Lowndes County, AL, Macon County, AL, Montgomery County, AL, Pike County, AL, Russell County, AL, Tallapoosa County, AL

The radar

The Maxwell AFB radar (KMXX), 45 km from the middle of the area, began a volume at 12:49 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

Peachtre/Fal Fld, GA (KFFC), launched 12:00Z, 0.8 hours before the alert went out and 195 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: 26 J/kg
Mixed-layer CIN: -350 J/kg
Mixed-layer LCL: 987 m above ground
0-6 km bulk shear: 59 kt
0-1 km storm-relative helicity: 317 m²/s²
0-3 km storm-relative helicity: 392 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.1

Open this sounding in Storm Lab

The text

As transmitted.

212 
ACUS11 KWNS 031246
SWOMCD
SPC MCD 031245 
GAZ000-ALZ000-031415-

Mesoscale Discussion 0417
NWS Storm Prediction Center Norman OK
0745 AM CDT Mon Apr 03 2017

Areas affected...part of central and east-central AL

Concerning...Severe Thunderstorm Watch 115...

Valid 031245Z - 031415Z

The severe weather threat for Severe Thunderstorm Watch 115
continues.

SUMMARY...Locally strong wind gusts cannot be ruled out this morning
across part of central and east-central AL within the valid portion
of WW 115.

DISCUSSION...Despite extensive cloudiness located across much of AL,
further destabilization should occur this morning into the afternoon
as mid 60s surface dew points spread into the eastern part of WW 115
by later this morning.  Lightning trends have been generally
diminishing along this portion of the MCS where the environment is
currently marginally unstable.  However, the aforementioned
moistening beneath the northern extent of steep midlevel lapse rates
suggests instability should increase this morning.  This would
likely allow storms to become surface based and stronger winds in
the low levels (50-60 kt at 850 mb) to reach the surface within
downdrafts, enhancing the threat for damaging winds later this
morning.

..Peters.. 04/03/2017

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...FFC...TAE...BMX...MOB...

LAT...LON   32018699 32388668 33058642 33108526 32288491 31788509
            31628545 31668615 31908631 32018699

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 3, 1:48 AM CDT	Tornado Watch	SPC	Baldwin, Choctaw, Clarke, Mobile, Washington	10 hr
Apr 3, 1:51 AM CDT	Mesoscale Discussion	SPC	Bibb, Blount, Calhoun, Cherokee, Clay, Cleburne and 6 more	114 min
Apr 3, 3:59 AM CDT	Mesoscale Discussion	SPC	Autauga, Baldwin, Bibb, Butler, Chilton, Choctaw and 17 more	2 hr
Apr 3, 4:25 AM CDT	Severe Thunderstorm Watch	SPC	Autauga, Barbour, Bibb, Bullock, Chambers, Chilton and 14 more	7 hr
Apr 3, 6:43 AM CDT	Mesoscale Discussion	SPC	Baldwin, Butler, Clarke, Coffee, Conecuh, Covington and 9 more	2 hr
Apr 3, 7:06 AM CDT	Tornado Watch	SPC	Butler, Coffee, Conecuh, Covington, Crenshaw, Dale and 6 more	6 hr
Apr 3, 9:25 AM CDT	Mesoscale Discussion	SPC	Barbour, Dale, Geneva, Henry, Houston, Lee and 1 more	65 min

Nearby

Mesoscale Discussions in Alabama, 2017 Every 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.