Mesoscale Precipitation Discussion 0724
NWS Weather Prediction Center College Park MD
1225 PM EDT Thu Jul 25 2024
Areas affected...Central to Northeast TX...Northern LA...Southern
AR...Northwest MS
Concerning...Heavy rainfall...Flash flooding likely
Valid 251625Z - 252225Z
SUMMARY...Areas of heavy showers and thunderstorms are expected to
increase somewhat in coverage over the next several hours heading
through late afternoon. Rather slow cell-motions and intense
rainfall rates will support concerns for areas of flash flooding.
DISCUSSION...The latest GOES-E IR satellite imagery shows an
expansive cloud-top canopy over much of southeast TX, western LA
and up through southern AR and northwest MS in connection with a
deep layer tropical moisture plume with embedded shortwave energy.
Closer inspection of this satellite imagery along with surface
data reveals a weak low center and related mid-level vort over
southwest to south-central AR in particular. This energy is
focusing an axis of relatively stronger moisture convergence
across areas of northeast TX through northwest LA and into
southern AR which then tails off somewhat farther off the
northeast into northwest MS. Meanwhile, MLCAPE values locally
across this region have increased to 1000 to 1500 J/kg. Moisture
is plentiful with PWs deeply tropical in nature with magnitudes of
1.75 to 2.25 inches based on the latest NESDIS Blended TPW data.
Given expectations of additional boundary layer destabilization
with the diurnal heating cycle, the combination of deep moisture
and instability along with at least modest low to mid-level
forcing near the aforementioned low center/vort energy should
favor a gradual increase in heavy shower and thunderstorm activity
going through the mid to late afternoon hours. Radar imagery
already shows scattered to locally broken areas of convection
impacting portions of the region.
The 12Z HREF guidance shows elevated probabilities (40 to 70
percent) of seeing 3"+ rainfall totals within a 6-hour period in a
southwest to northeast axis across far northeast TX, northwest LA
and southwest to south-central AR going through the late afternoon
hours. These probabilities then tail off a bit farther off to the
northeast into northwest MS, and likewise to the southwest going
closer to areas of central TX. Key drivers though overall to the
heavy rainfall potential will be impressive rainfall rates capable
of reaching 2.0" to 2.5"/hour rainfall rates and slow convective
cell-motions.
Some localized storm total amounts of 3 to 5 inches are expected.
As a result, some areas of flash flooding are generally likely to
materialize at least in a scattered fashion, and the more
urbanized areas will be most vulnerable to this threat.
Orrison
ATTN...WFO...EWX...FWD...HGX...JAN...LZK...MEG...SHV...
ATTN...RFC...ABRFC...LMRFC...SERFC...WGRFC...NWC...
LAT...LON 34938901 34458843 33818869 32899062 32349215
31489455 30389661 30459761 31159788 32049712
32889561 33929290 34549156 34909030
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