WPC Met Watch |
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Mesoscale Precipitation Discussion: #1056 (2022) |
(Issued at 205 PM EDT Fri Sep 30 2022
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MPD Selection |
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Mesoscale Precipitation Discussion 1056
NWS Weather Prediction Center College Park MD
205 PM EDT Fri Sep 30 2022
Areas affected...Eastern & Southern UT...Western CO...Southern
WY...Far Northern AZ
Concerning...Heavy rainfall...Flash flooding possible
Valid 301805Z - 010000Z
SUMMARY...Numerous thunderstorms containing excessive rainfall
rates may result in flash flooding, especially along complex
terrain, in dry washes, slot canyons, and areas with sensitive
soils.
DISCUSSION...An upper low barreling through southeast Idaho this
afternoon is introducing PVA into eastern Utah and the Central
Rockies while the nose of a 250mb jet streak over the Great Basin
results in diffluent flow aloft. At 700mb, a steady injection of
700mb moisture flux is oriented over the same highlighted region.
The upper low over Idaho is in no rush leaving the state and will
only make it as far as the ID/WY/UT border by 06Z. This is
resulting in a fairly uniform WSW streamline regime in the
700-500mb layer. At the surface, a cold front is slowly making its
way east and will act as a trigger at the surface. Daytime heating
within the warm sector fosters an increasingly unstable
environment, resulting in SBCAPE according to the RAP reaching
~1,000 J/kg. PWs >0.75" are set up in southern Utah and into
western Colorado and PWs throughout the highlighted region are
likely to hover around the 90th climatological percentile.
Soils remain quite sensitive with NASA SPORT-LIS identifying soil
moisture percentiles >90% in parts of southern and eastern Utah.
Soil moisture is not as elevated in Colorado and Wyoming, but
complex terrain and residual burn scars are susceptible areas to
flash flooding. With uniform WSW flow aloft, it is possible for
not only topographic enhancement of convection but for training
and back-building cells along orographically favored terrain. 12Z
HREF shows 6-hr QPF > 10 yr ARI probabilities as high as 50-60%
north of GJT and values of 30% in parts of southeast and eastern
Utah between 18-00Z. With anomalous PWs, sufficient instability,
and synoptic scale support aloft, thunderstorms this afternoon may
produce areas of flash flooding with dry washes, slot canyons, and
sensitive soils most at-risk.
Mullinax
ATTN...WFO...BOU...CYS...FGZ...GJT...RIW...SLC...VEF...
ATTN...RFC...CBRFC...MBRFC...NWC...
LAT...LON 41810768 41230620 39600671 38080826 37101012
36911358 37921370 38451242 39241109 40350943
Last Updated: 205 PM EDT Fri Sep 30 2022
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