Mesoscale Precipitation Discussion 0020
NWS Weather Prediction Center College Park MD
1135 AM EST Mon Jan 22 2024

Areas affected...upper TX coast into southeastern TX

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

Valid 221630Z - 222230Z

Summary...Heavy rain is expected to slowly advance through
portions of southeastern TX over the next few hours. Rainfall
rates of 1-2 in/hr and 2-4 inch totals (locally higher possible)
are expected which may lead to areas of flash and urban flooding.

Discussion...16Z regional radar imagery showed a broad area of
moderate to heavy rain slowly advancing eastward from the middle
TX coast into east-central TX. This area was located ahead of a
mid-level shortwave over east-central TX, within an axis of low
level moisture transport and convergence, centered within the
925-850 mb layer. 40-50 kt of flow was observed in the 925-850 mb
layer, overrunning a relatively shallow cool and stable layer
below ~925 mb. The latest GPS observations showed PWATs near 1.5
inches along the middle TX coast, helping to support MUCAPE values
of 250-750 J/kg from near Matagorda Bay and points inland down to
the Lower Laguna Madre.

As the shortwave over east-central TX advances toward the
northeast though the late afternoon, forcing ahead of this feature
will slowly shift east, translating the axis of low level
convergence and focus for heavy rainfall slowly up the TX coast
over the next 3-6 hours. Considering the low level convergence
axis is nearly aligned with steering flow from the SSW, areas of
training are expected. Instability is forecast to increase inland
from the Gulf Coast into the afternoon as low level moisture
increases which should support the ability for 1-2 in/hr rainfall
rates where training occurs. While the axis of convergence is
expected to progress fairly steadily toward the east, there will
be opportunities for training where axes of heavier rainfall align
with the steering flow. Overall, 2-4 inches of rain is expected
for portions of the upper TX coast into portions of southeastern
TX, but locally higher totals cannot be ruled out. Despite fairly
dry antecedent conditions, a threat for flash flooding will
result, perhaps focused best in urban areas (including the Houston
metro) and other low lying locations of poor drainage.

Otto

ATTN...WFO...CRP...EWX...FWD...HGX...LCH...SHV...

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

LAT...LON   31389525 31259460 30799418 29929424 29129455
            28409549 28209615 28429647 29339671 30629640
            31179585