From Mike Powell@618:250/1 to All on Thursday, August 29, 2024 10:00:00
AWUS01 KWNH 291202
FFGMPD
MNZ000-NDZ000-291700-
Mesoscale Precipitation Discussion 0943
NWS Weather Prediction Center College Park MD
800 AM EDT Thu Aug 29 2024
Areas affected...Eastern ND...Northwest MN
Concerning...Heavy rainfall...Flash flooding possible
Valid 291200Z - 291700Z
SUMMARY...Additional areas of heavy showers and thunderstorms can
be expected going through the morning hours across portions of
eastern ND and northwest MN. Localized training of these storms
may still pose some additional isolated flash flooding concerns.
DISCUSSION...The early morning GOES-E IR satellite imagery shows a well-organized axis of convection with locally very heavy rainfall
impacting portions of eastern ND and northwest MN. The convection
is embedded within a highly divergent flow pattern aloft downwind
of a deep upper trough/closed low over the far northern High
Plains and adjacent areas of south-central Canada.
This coupled with strong warm air advection ahead of a frontal
occlusion and with a well-defined axis/pool of moderate to strong
elevated instability focusing along and north of a warm front
lifting through the Upper Midwest has been helping to drive a
persistence of the convection over the last few hours.
A southwest low-level jet of 40 to 50 kts is still in place nosing
up across the Red River Valley of the North which is yielding
strong moisture transport/convergence and there is a corridor of
MUCAPE values of 2000 to 3000 J/kg still noted over eastern ND and
far western MN. These ingredients are likely to persist going
through the morning hours, with perhaps some subtle decrease in
the low-level jet. However, given the current orientation of the
convection being parallel to the low-level jet and with enhanced moisture/instability transport, there will be concerns lingering
this morning for persistent bands of convection that will be
capable of locally training over the same area.
A large number of the 00Z/06Z HREF members tend to suggest a rapid
weakening of the activity by mid to late morning, but this is not
the case with recent HRRR guidance which suggests a persistence,
especially across northwest MN, of convection that may result in
an additional 3 to 4 inches of rain locally. Satellite trends over
the last 1 to 2 hours would support the HRRR guidance, and
especially with the array of deep cold convective tops seen over
the region.
There may be some additional isolated flash flooding concerns this
morning as this ongoing axis of convection over eastern ND through
northwest MN persists.