Mesoscale Discussion 649

Issued

May 17, 2021, 12:47 PM CDT (17:47 UTC)

Expired

May 17, 2021, 2:15 PM CDT

In force

88 min

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch unlikely

Chance of a watch

20%

The Ft Hood radar (KGRK), 89 km from the middle of the area, began a volume at 17:47 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.

309 
ACUS11 KWNS 171748
SWOMCD
SPC MCD 171747 
TXZ000-171915-

Mesoscale Discussion 0649
NWS Storm Prediction Center Norman OK
1247 PM CDT Mon May 17 2021

Areas affected...southeast Texas

Concerning...Severe potential...Watch unlikely 

Valid 171747Z - 171915Z

Probability of Watch Issuance...20 percent

SUMMARY...A localized hail and wind threat will persist in the
near-term associated with a southeast moving cluster of
thunderstorms. Elsewhere, a localized severe hail or wind threat
will be possible as additional thunderstorms develop through the
afternoon.

DISCUSSION...A long-lived cluster of thunderstorms, currently
approaching Round Rock, continues to move southeast across central
Texas this afternoon. The most intense portion of this elongated
cluster is occurring along and north of a residual southward moving
outflow boundary from overnight convection. The airmass ahead of
this thunderstorm complex remains extremely moist (precipitable
water values approaching 2") and is increasingly unstable
(mixed-layer CAPE between 2000-3000 J/kg) and uncapped (mixed-layer
CINH less than 25 J/kg).

Despite an increasingly favorable thermodynamic environment ahead of
the complex, kinematically the environment is less favorable for
severe potential as effective-layer shear and low-level shear weaken
with eastward extent. Given the existing thunderstorm cluster
organization, a continued threat for hail and wind will persist in
the near-term. Additionally, given the extremely moist environment
and the presence of an outflow boundary, a brief tornado or two
cannot be ruled out. However, longer-term prospects for severe
potential remain relatively low.

Elsewhere, as mentioned, an increasingly unstable and uncapped
environment across southeast Texas will allow for thunderstorm
development through the afternoon. Localized potential for severe
hail or a wet-microburst will exist, but coverage should remain too
isolated to warrant a watch.

..Marsh/Guyer.. 05/17/2021

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

ATTN...WFO...LCH...HGX...FWD...EWX...

LAT...LON   30499879 31249812 31309756 31089605 31109514 30819459
            30189437 29479446 29069502 29049588 29389705 29629828
            30189876 30499879

Mesoscale Discussions in Texas, 2021Every mesoscale discussion in 2021

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.