Graphic for MPD #0086
Mesoscale Precipitation Discussion 0086
NWS Weather Prediction Center College Park MD
140 AM EST Fri Mar 08 2024

Areas affected...Northeast TX....Northern LA...Southern
AR...Central Western MS...

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

Valid 080645Z - 081245Z

SUMMARY...Increasing breadth of isentropic ascent across the area
of concern within fairly unidirectional cell motions suggest
prolonged duration of moderate to occasionally heavy elevated
thunderstorms capable of 1-1.5"/hr rates and possible localized
2-3.5" totals and isolated possible incidents of flash flooding.

DISCUSSION...06z surface analysis denotes a weak boundary defined
mainly as a convergence axis extending from NW AL across central
MS, northern LA into northeast TX.  Here, the boundary is
reinforced by strengthening low level ridging behind older outflow
boundary from dying convective clusters/linear that crossed
northern Texas and S Oklahoma.  GOES-E and RAP analysis suggest
the catalyst for the earlier convection continues across
along/north of the Red River as a weak inflection/shortwave along
the 500-300 mb jet streak.  Weak diffluence and DPVA has increased
LLJ off the northwest Gulf of Mexico with southeasterly return
flow across E TX/W LA.  Surface obs and Sfc-850mb CIRA LPW denote
the eastern edge of enhanced moisture through the Sabine River
Valley generally intersecting across northeast TX.  CIRA LPW in
the 850-700 layer also notes an enhanced slug of moisture along
solid veering through the layer intersecting across the area of
best DPVA/vertical ascent in proximity to the surface boundary.

As such a recent uptick in convective activity has started to
occur in across NE TX into northern LA and far southern AR,
ascending to elevated LFC.  VWP in the region has been steadily
increasing to over 40 to 45kts through the layer further
supporting moisture flux for efficient rainfall production. Lapse
rate and profiles are very weak and so instability has been
limited for updraft vigor, but the sheer magnitude of convergence
will likely continue given the strength of the LLJ and convergence
along the veering profile.  Currently, this is supporting .75"/hr
rates that will steadily increase to over 1-1.5"/hr.  Combine this
with the length of the ascent across the boundary and
unidirectional flow for steering generally parallel to the
boundary should support training profiles through the early
morning.  As such, spots of 2-3.5" totals can be expected.  While
the area has remained dry recently (with 14-day anomalies less
than 25% of normal; with exception of far NE LA into central
Western MS); NASA SPoRT LIS suggests relative soil moisture values
are near 50% and at or just above normal (70th percentile)
suggesting perhaps an isolated incident or two of flash flooding
will be possible through early morning.

Later in the time period (10-12z), there is some model
uncertainty...but appears to becoming into focus that enhanced
theta-E air will emerge from the western Gulf and reach the
boundary toward this time period increasing overall moisture depth
to 1.5-1.7 still within a highly confluent 850mb isentropic ascent
channel across northeast LA into west-central MS increasing
rainfall efficiency from 1.5" to 2"/hr. 

Gallina

ATTN...WFO...JAN...LZK...SHV...

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

LAT...LON   33449141 33249053 32689004 32079031 31909164
            31899251 31839495 32529539 32979493 33269389
            33399256
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Last Updated: 140 AM EST Fri Mar 08 2024