Areas affected…Eastern CO…Western NE…Southern Eastern WY
Concerning…Heavy rainfall…Flash flooding possible
Valid 081930Z – 090130Z
Summary…Expect showers and thunderstorms to continue to blossom
through the afternoon along the high terrain eventually moving out
into the Plains through the afternoon into the evening hours. Rain
rates exceeding 1.5 inches could lead to flash flooding,
especially over residual burn scars.
Discussion…Based on latest radar, showers and thunderstorms have
already developed along the upslope regions of the high terrain in
CO. With upper level support, noted by the right entrance region
of the 250mb jet and mid-level impulses, expect plenty of lift
across this region. At the surface, a boundary remains draped
across southern portions of WY into western NE which also
continues to be the focus for shower and isolated thunderstorm
activity at this hour. However, the main area of concern is
aligned with the thunderstorms developing across the higher
terrain moving east thanks to the mean flow in a region more
favorable for thunderstorm/heavy rainfall.
An outflow boundary from this mornings convection across the
Central Plains moved west and has become adjacent to the central
Rockies (over the Front Range). This combined with monsoonal
moisture will result in heavy rainmakers if adequate instability
is present. According to the mesoanalysis, MUCAPE values are
around 1000-2000 J/kg (surface based CAPE >2000 J/kg) across
eastern CO. With southeasterly 850mb flow helping to enhance lift
across the higher terrain, it is also advecting in higher
precipitable water values of 1.5 inches and better instability
just to the east.
While there is a multi-model signal for high rain rates in excess
of 1.5 inches per hour, as the storms grow upscale in the next few
hours, the mean flow will be greater than 30 knots to the
southeast. This should limit flash flood potential across this
region into the evening. Though, it appears the storm motion just
south of the surface boundary is a bit more ambiguous with more
surface based convection. In reviewing the flash flood guidance
(which shows pockets of 0.5-1.5 inches/3 hours) and the potential
for cell mergers across the northern domain, expect flash flooding
to be a concern over the more vulnerable soils/burn scars. The
flash flood potential looks to increase in time, especially
between 21Z-04Z.
Pagano
…Please see www.wpc.ncep.noaa.gov for graphic product…
ATTN…WFO…BOU…CYS…GID…GLD…LBF…PUB…
ATTN…RFC…ABRFC…CBRFC…MBRFC…WGRFC…
LAT…LON 41840575 41460314 41380081 40709916 40089982
39680211 37280226 37090490 38420598 39900574