Colorado Mesoscale Discussion

Areas affected…High Plains of SE Colorado into the OK Panhandle

Concerning…Heavy rainfall…Flash flooding possible

Valid 090200Z – 090800Z

Summary…Thunderstorms developing in the residual instability
from afternoon heating will try to organize through the evening.
Rainfall rates may reach 2″/hr at times, and isolated flash
flooding is possible.

Discussion…GOES-16 IR imagery this evening shows an expanding
area of cooling cloud tops across eastern CO atop increasing
thunderstorm coverage east of the Front Range. This convection is
developing in response to broad large scale ascent ahead of a weak
shortwave lifting into southern CO, and modest diffluence in the
RRQ of a departing upper jet streak. Additionally, a weak lee
surface trough was analyzed helping to focus low-level convergence.

This ascent is occurring in an environment favorable for heavy
rainfall. 00Z RAP MUCape was analyzed to be 1000-2000 J/kg, while
PWATs on the 00Z U/A soundings from KDNR, KDDC, and KAMA were all
at or above the 90th percentile for the date. This moist column
was being reinforced by low-level easterly flow from a moisture
pool with PWATs over 2″ in Oklahoma, with the upslope component of
this flow further aiding in ascent. As this setup persists,
convection is likely to continue to blossom as shown by recent
runs of the HRRR, and with bulk shear values reaching 35kts,
expect organization of thunderstorms into clusters, or potentially
a larger scale MCS during the next few hours.

This MCS is likely to dive southeast into the low-level flow, and
this is shown by a multi-model CAM consensus which depicts a
narrow region of 1-3″ of rainfall, with isolated higher amounts.
Although 0-6km mean winds should remain 10-15 kts, with even
faster Corfidi vectors, these are likely to be parallel to the
storm motion along the 850-300mb thickness gradient, suggesting
the potential for training thunderstorms. HREF probabilities for
1″/hr and 2″/hr rain rates remain moderate for the next several
hours, and this is reflected by HREF v2 3-hr exceedance
probabilities peaking at over 50%.

While the risk for flash flooding is primarily dependent on this
MCS development and training, portions of southeast CO have
received more than 200% of rainfall in the past week, leading to
lowered FFG. This suggests that even heavy rain makers with less
organization may pose a flash flood threat into the early
overnight period.


…Please see for graphic product…



LAT…LON 39140325 38890252 38710209 38460169 38130138
37750123 37450125 37230142 36900162 36650189
36540224 36480304 36590352 36800398 37080433
37790488 38230470 38690436 38930402 39080362

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