Mesoscale Precipitation Discussion 0001
NWS Weather Prediction Center College Park MD
519 AM EST Fri Jan 05 2024

Areas affected...portions of the Middle & Upper TX Coast

Concerning...Heavy rainfall...Flash flooding possible

Valid 051018Z - 051618Z

Summary...Showers and thunderstorms have been developing within a
saturating air mass and showing increasing hourly rain totals
where cells train.  Hourly totals to 1.5" with local amounts to 3"
are anticipated, which could lead to isolated flash flooding
issues.

Discussion...Showers and thunderstorms have been developing over
the past few hours across portions of the Middle and Upper TX
coast along an inverted trough of pure wind convergence extending
north-northeast of a pair of surface lows near the TX coast and
near a front that connects the two.  Hourly rain total estimates
are exceeding 1.2" in southern Jackson County in an area along a
stationary front between two discrete surface lows.  Precipitable
water values have risen quickly towards 1.5" per GPS data. 
Effective bulk shear of 30-40 kts is leading to some cell
organization and short bouts of cell training, which have yielded
~2" of rain so far southwest of Austwell, per radar estimates.  MU
CAPE is minimal but increasing as the lows slowly deepen.

The expectation in recent RAP runs is for the two lows to
consolidate between now and 15z, which when it occurs, could end
the training convective threat.  Possible mesocyclones and cell
mergers would also aid heavy rain production.  In the meantime,
the signal in the 06z HREF is for a strong signal for 2" and a
non-zero chance for 3", which is extremely close to area flash
flood guidance values.  The 06z HREF has been too far east with
its rainfall signal so far, placing it at the coast or offshore
rather than inland.  Patches of this region have seen 300%+ of
their average weekly rainfall, so some degree of soil saturation
has occurred.  With the expectation of hourly rain totals peaking
in the 1.5" neighborhood and local amounts of 3" expected, flash
flooding is expected to be isolated within the MPD area.

Roth

ATTN...WFO...CRP...HGX...LCH...

ATTN...RFC...WGRFC...NWC...

LAT...LON   30249478 29539431 28989516 28239645 27639728
            28769698 29969593