WPC Met Watch |
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Mesoscale Precipitation Discussion: #0156 (2019) |
(Issued at 409 AM EDT Wed Apr 24 2019
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MPD Selection |
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Mesoscale Precipitation Discussion 0156
NWS Weather Prediction Center College Park MD
409 AM EDT Wed Apr 24 2019
Areas affected...South-Central Texas and Hill Country
Concerning...Heavy rainfall...Flash flooding possible
Valid 240809Z - 241245Z
Summary...Thunderstorms may persist early this morning in Texas
Hill Country and produce locally heavy rainfall in excess of 3
inches. This could lead to localized flash flooding.
Discussion...Between 05Z and 08Z, convective intensity across much
of Texas has generally waned. An area where colder cloud tops have
generally maintained brightness temperatures and spatial extent on
GOES-16 imagery has been in South-Central Texas. This is on the
tail end of an extensive convective outflow boundary, and
coincides with the portion of the boundary that is generally still
intercepting a moderately unstable low-level air mass (MLCAPE
1000-1500 j/kg, MLCINH <25 j/kg). It was also the portion of the
line on the northern periphery of a band of enhanced low-level
flow. Radar VWP from KEWX and KDFX generally show SSE flow around
25 knots in the 925-850mb layer. These factors may sustain a
concentrated area of organized convection for another several
hours. Negative factors for heavy rain-producing convection
include a trend toward less organization in the radar reflectivity
appearance, continued southward drift to the convection owing to
steady progression of convective outflow, and PW values generally
below 1.4 inches in the outlined area (GPS-PW observations; CIRA
blended TPW). The result should be somewhat limited rainfall rates
and duration of heavy rain. Nevertheless, hi-res models do suggest
that the southward progression may begin to stall in the next six
hours, and given the continued access to an unstable air mass,
this may support increased training and heavy rain potential with
time. If a period of training convection were to occur, localized
rainfall totals could exceed 3 inches, which would approach flash
flood guidance if it occurred in approximately 3-4 hours in
portions of Texas Hill Country.
Lamers
ATTN...WFO...EWX...MAF...SJT...
ATTN...RFC...WGRFC...
LAT...LON 31129983 30939890 30249855 29699924 29540047
29990169 30390174 30810125 31050047
Last Updated: 409 AM EDT Wed Apr 24 2019
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