WPC Met Watch |
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Mesoscale Precipitation Discussion: #1061 (2022) |
(Issued at 801 PM EDT Fri Sep 30 2022
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MPD Selection |
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Mesoscale Precipitation Discussion 1061
NWS Weather Prediction Center College Park MD
801 PM EDT Fri Sep 30 2022
Areas affected...Southeast UT...Western CO
Concerning...Heavy rainfall...Flash flooding possible
Valid 010000Z - 010300Z
SUMMARY...Thunderstorms capable of producing excessive rainfall
rates look to continue for a couple more hours, potentially
resulting in additional areas of flash flooding.
DISCUSSION...The upper low over Idaho continues to foster
favorable diffluent flow atop the atmosphere while a residual
influx of 700mb moisture also remains in place. RAP guidance
around ~00Z still shows 500-1,000 J/kg of MLCAPE available in
northwest AZ and southwest UT, with lesser values in the 250-500
J/kg range in east-central UT. There also remains convergent 700mb
flow over the region, denoted by NW flow coming out of the
northern Great Basin and SW flow from the Lower Colorado River
Basin. This coincides with a fairly uniform SW flow pattern within
the 700-500mb layer, suitable for potential training cells and
orographic enhancement along favorably oriented terrain. Daytime
heating is coming to an end, so the window will soon close for the
current pockets of convection. However, given the available
instability, moisture content (PWs hovering around 0.75" on
average) and supportive synoptic-scale forcing, heavy
thunderstorms should stick around for a few more hours.
Soil moisture percentiles remain around the 90th percentile for
parts of southern and east-central Utah, with some storms having
prompted FLASH CREST maximum unit stream flow responses >200
cfs/smi at times. MRMS instantaneous rates have gotten as high as
2"/hr at times, and given the terrain and sensitive soils, these
kind of instantaneous rainfall rates in brief periods of time can
cause rapid runoff. It will be in these areas with saturated
soils, as well as in slot canyons, dry washes, burn scars, and
along complex terrain that continue to feature the best odds of
contending with flash flooding for the remainder of the evening.
Mullinax
ATTN...WFO...GJT...SLC...
ATTN...RFC...CBRFC...NWC...
LAT...LON 40000814 39560721 38530752 37610832 37210929
37071055 37161180 37561288 37821325 38181295
38831129 39640982
Last Updated: 801 PM EDT Fri Sep 30 2022
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