Alert archive / Texas / Mesoscale Discussions in 2021

Mesoscale Discussion 2044

December 18, 202143 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at Dec 18, 2021, 1:17 AM CST for 43 counties in Texas. It was in force for 118 min.

The area

The outline as issued.

The facts

Issued
Dec 18, 2021, 1:17 AM CST (07:17 UTC)
Expired
Dec 18, 2021, 3:15 AM CST
In force
118 min
Issued by
the Storm Prediction Center
Concerning
Severe potential...watch unlikely
Chance of a watch
20%
All 43 counties

Anderson County, TX, Bastrop County, TX, Bell County, TX, Bexar County, TX, Blanco County, TX, Bosque County, TX, Brazos County, TX, Burleson County, TX, Burnet County, TX, Caldwell County, TX, Comal County, TX, Coryell County, TX, Ellis County, TX, Falls County, TX, Fayette County, TX, Freestone County, TX, Gillespie County, TX, Gonzales County, TX, Guadalupe County, TX, Hamilton County, TX, Hays County, TX, Henderson County, TX, Hill County, TX, Houston County, TX, Johnson County, TX, Kaufman County, TX, Kendall County, TX, Lampasas County, TX, Lee County, TX, Leon County, TX, Limestone County, TX, Llano County, TX, Madison County, TX, McLennan County, TX, Medina County, TX, Milam County, TX, Mills County, TX, Navarro County, TX, Robertson County, TX, Travis County, TX, Van Zandt County, TX, Williamson County, TX, Wilson County, TX

The radar

The Ft Hood radar (KGRK), 7 km from the middle of the area, began a volume at 07:17 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

Fort Worth, TX (KFWD), launched 00:00Z, 7.3 hours before the alert went out and 235 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-pSkew-T log-p diagram, Fort Worth, TX at 00:00Z on 2021-12-18Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 907 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Fort Worth, TX at 00:00Z on 2021-12-18The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 138 square meters per square second.19395878Sfc1 km3 km6 km9 kmRMLM
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
907 J/kg
Mixed-layer CIN
-61 J/kg
Mixed-layer LCL
1218 m above ground
0-6 km bulk shear
38 kt
0-1 km storm-relative helicity
138 m²/s²
0-3 km storm-relative helicity
205 m²/s²
Significant tornado parameter
0.5
Supercell composite
2.4

Open this sounding in Storm Lab

The text

As transmitted.

272 
ACUS11 KWNS 180717
SWOMCD
SPC MCD 180717 
TXZ000-180915-

Mesoscale Discussion 2044
NWS Storm Prediction Center Norman OK
0117 AM CST Sat Dec 18 2021

Areas affected...Central/East TX

Concerning...Severe potential...Watch unlikely 

Valid 180717Z - 180915Z

Probability of Watch Issuance...20 percent

SUMMARY...Increasing thunderstorm coverage is expected across
central TX over the next several hours. A few storms may become
strong enough to produce hail and/or damaging wind gusts.

DISCUSSION...Recent surface analysis places a cold front from
southeast OK southwestward back through north-central TX and then
more westward across the TX Big Country into the Permian Basin.
Northerly wind gusts behind this front are around 20-30 kt, and the
expectation is that the front will continue surging southeastward
throughout the night. Warm sector ahead of the front from central TX
through the Arklatex is characterized by temperatures in the upper
60s to low 70s and dewpoints in the low to mid 60s. These conditions
beneath relatively steep mid-level lapse rates (around 7-7.5 degrees
C per km from 700 to 500 mb) are resulting in a moderately buoyant
airmass with MLCAPE around 1000-1500 J/kg. In addition to this
buoyancy, persistent southwesterly flow aloft (mainly above 700 mb)
stretches across the warm sector and mesoanalysis estimates
effective bulk shear around 40-45 kt. 

Satellite imagery depicts a shortwave trough embedded within this
southwesterly flow moving through central Mexico, and the lift
associated with shortwave augmented by ascent attendant to the cold
front is forecast to result in increased thunderstorm coverage
across central TX tonight. Given the environmental conditions
described above, a few of these storms may become strong enough to
produce hail and/or damaging wind gusts. Weak low-level flow should
keep the tornado potential low and limited overall severe coverage
will likely preclude the need for a watch.

..Mosier/Grams.. 12/18/2021

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

ATTN...WFO...SHV...HGX...FWD...EWX...SJT...

LAT...LON   30419925 31499861 32489730 32749669 32709598 32419543
            31649516 30989549 29629715 29419746 29189790 29079828
            29099877 29279914 30419925

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Dec 17, 6:56 PM CSTMesoscale DiscussionSPCCooke2 hr
Dec 18, 9:02 AM CSTMesoscale DiscussionSPCAransas, Austin, Bee, Brazoria, Brazos, Caldwell and 32 more118 min
Dec 18, 12:50 PM CSTMesoscale DiscussionSPCJefferson, Newton, Orange115 min

Nearby

Mesoscale Discussions in Texas, 2021Every mesoscale discussion in 2021

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.