Monday 8/20 Weather

Monday through Tuesday: A trough somewhat detached from the large-
scale flow will drift eastward across the central Great Plains on
Sunday before phasing with long-wave troughing over central Canada
Monday through Tuesday. This will support the development of an
anomalously strong low pressure for mid-August, with ensemble
guidance already showing an anomaly of two standard deviations for a
1010 mb low. However, most deterministic models and individual GEFS
solutions show a low more on the order of 1005-1007mb passing over
the CWA early Tuesday morning. Fairly strong low-level moisture
transport of 2" PWAT values northeastward into the region will
support a large shield of rain with pockets of heavy rain.
Conditions will deteriorate from SW to NE Monday afternoon, with the
greatest focus for widespread showers Monday evening. Showers should
diminish in coverage as the low shifts NE on Tuesday, but a
lingering area of deformation stretching west to east just north of
the CWA may shift far enough south to continue more persistent
showers well into Tuesday across northern portions of the CWA.

With this set-up, the potential exists for localized flooding,
particularly for locations that have had several rounds of heavy
precip over the past week or so. Any individual showers/storms
should have enough movement to minimize high rainfall potential at
any particular location over a short period of time. In addition to
the localized flooding threat, a highly conditional threat for
strong to severe storms exists Monday afternoon and evening. Poor
mid-level lapse rates will limit instability, but if enough
instability is generated ahead of the shower activity, deep layer
shear surpassing 30 knots, including 0-3km shear of 25 knots, will
support gusty winds with any showers/storms. The main focus would be
across southeastern portions of the CWA.