Mesoscale Precipitation Discussion 0924...Corrected
NWS Weather Prediction Center College Park MD
1227 AM EDT Thu Oct 04 2018
Corrected for model section reasoning
Areas affected...Far eastern CA...Northwest AZ...Southeast
NV...Southwest UT
Concerning...Heavy rainfall...Flash flooding possible
Valid 040425Z - 041025Z
Summary...Showers and thunderstorms may become a bit more numerous
over the next few hours. Heavy rainfall rates will be conducive to
some flash flood potential.
Discussion...A well-defined upper low over the San Joaquin Valley
will advance gradually east overnight as an associated trough axis
pivots northeast around the base of it. The trough axis should
lift through eastern CA, southeast NV, western AZ and southwest UT
going through 12Z. Despite the loss of daytime heating, there will
be sufficient instability owing to steep mid-level lapse rates,
and also dynamical ascent courtesy of a 90+kt 250mb jet-max for
scattered and loosely organized areas of convection overnight.
The more organized convective threat will tend to be over western
AZ, southeast NV and southwest UT where there is somewhat better
instability already present as per the latest RAP analysis, and
stronger upper level divergence given placement of the
aforementioned jet-max. The better moisture anomalies are focused
over southeast NV and southwest UT where PWATs are as much as 2 to
3 standard deviations above normal.
The 00Z HREF suite of guidance supports as much as 1 to 2 inches
of rain through 12Z with some locally heavier totals possible. The
activity is expected to have an orographic component to it across
especially northwest AZ and southwest UT and this could lead to
some locally enhanced totals, and especially with the guidance
supporting some repeating of convective cells for these areas.
Some flash flooding will be possible given the relatively heavy
short-term rainfall rates and overall potential over the next
several hours.
Orrison
ATTN...WFO...FGZ...PSR...SLC...VEF...
ATTN...RFC...CBRFC...CNRFC...
LAT...LON 38251315 37831188 36281184 34841241 33831333
33451408 33451453 33591491 34381527 35271515
36311483 37571415
Last Updated: 337 AM EDT Thu Oct 04 2018