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WPC Met Watch

Mesoscale Precipitation Discussion: #0774
(Issued at 135 PM EDT Wed Aug 17 2022 )

MPD Selection

Graphic for MPD #0774

Mesoscale Precipitation Discussion 0774
NWS Weather Prediction Center College Park MD
135 PM EDT Wed Aug 17 2022

Areas affected...Southern Colorado, Northern New Mexico

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

Valid 171734Z - 172300Z

Summary...Showers and thunderstorms will increase in coverage
through this aftn. Rainfall rates of 1-2"/hr are likely to become
common, which through slow storm motions could produce 1-3" of
rain. Flash flooding is possible.

Discussion...The GOES-E visible satellite imagery this aftn
indicates breaks have developed within the morning widespread
mid-level cloud cover, which is resulting in rapid instability
growth and building Cu. SPC RAP analyzed SBCAPE is as high as 1500
J/kg collocated with these breaks in sky cover, with GPS measured
PWs climbing to as high as 1.3" in eastern CO/NM, and 0.9" across
the higher terrain of western CO, around the 90th percentile for
the date. The overlap of these favorable thermodynamics is fueling
this developing convection, which has radar-estimated rain rates
of 0.5-1"/hr, while a shortwave dropping out of northern CO and a
potent mid-level deformation axis stretched west-east near the
CO/NM border will provide ascent to expand coverage through the

As the aftn progresses, the high-res models are in good agreement
that thunderstorms will become widespread across southern CO and
into northern NM as moisture begins to return around a high
pressure to the east, driving PWs to 1.25-1.5", coincident with
SBCAPE rising to 1000-2000 J/kg. Storms will likely initially form
on high terrain including the Sangre de Cristos and Raton Mesa,
but should expand along convective outflows and any storm mergers
as weak 0-6km bulk shear fosters primarily pulse-type storms. Mean
cloud layer winds in the vicinity of this deformation axis will be
weak at just 5-10 kts, and variable in direction, with storm
mergers/boundary collisions driving even more slow and choatic
motion. Later this evening, northerly flow developing across CO
may help better organize convection into clusters and drive the
heaviest rainfall into northern/northeast NM.

As thermodynamics become more robust into this evening, rainfall
rates will likely reach 1-2"/hr as shown by both the HREF
probabilities and UA WRF precipitation fields. This could produce
1-3" of rain in some places, with locally higher amounts possible
as storms organize this evening into northeast NM. These rainfall
rates falling atop burn scars or within sensitive terrain could
lead to rapid runoff and flash flooding. However, soils across
this region are already pre-saturated noted by NASA SPoRT 0-40cm
soil moisture above the 98th percentile due to well above normal
30-day rainfall. This suggests heavy rainfall could rapidly lead
to flash flooding anywhere across the region this aftn and evening.




LAT...LON   39240724 39040579 38420388 37780314 37090286
            36670284 36260302 35940331 35480440 35530550
            35820677 36280776 37000847 37700888 37820892
            38580902 39010877 39160829

Last Updated: 135 PM EDT Wed Aug 17 2022

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Page last modified: Saturday, 01-Jan-2022 07:08:48 GMT