Mesoscale Discussion 0854
NWS Storm Prediction Center Norman OK
0347 PM CDT Mon May 20 2024
Areas affected...Northeast Colorado...southeast Wyoming...southwest
Nebraska
Concerning...Severe potential...Watch possible
Valid 202047Z - 202315Z
Probability of Watch Issuance...60 percent
SUMMARY...Initially high-based convection within the Front Range
into southeast Wyoming will eventually spread east and intensify.
Primary hazards will be severe wind gusts and large/very-large hail.
A mesoscale corridor with greater tornado risk will in northeast
Colorado and vicinity within the moisture axis. A watch will
eventually be needed this afternoon.
DISCUSSION...Convection continues to develop along the Front Range
as upslope flow continues this afternoon. A weak thunderstorm has
formed recently south of Denver in drier air. The exact timing of
storm greater initiation/intensification is a bit unclear, but the
approach of the mid-level ascent from the Four Corners region should
foster additional development within the next 2-3 hours or so.
Further, the lee trough to the east should also deepen and pull
richer surface moisture (upper 50s to low 60s F, as observed in
upstream in Kansas) into northeast Colorado and southwest Nebraska.
The current thinking is that storms will initiate within the Front
Range as well as southeast Wyoming. Storms will initially be
high-based and primarily capable of severe wind gusts and large
hail. Storm intensification can be expected as they encounter richer
moisture to the east. A greater tornado threat will exist with
supercells moving within the moisture axis in northeast Colorado and
nearby vicinity. Here, backed surface winds will combine with an
eventual modest increase in easterly 850 mb winds to increase
low-level hodograph curvature. Very-large hail will also become more
probable as supercell storms intensify farther east.
Mesoscale Discussion 1503
NWS Storm Prediction Center Norman OK
0216 PM CDT Mon Jul 01 2024
Areas affected...Far Southeastern WY...NE
Panhandle...Western/Central SD...Central ND
Concerning...Severe potential...Watch likely
Valid 011916Z - 012115Z
Probability of Watch Issuance...80 percent
SUMMARY...Thunderstorm intensity and coverage is expected to
increase over the next few hours from the central Dakotas into the
Nebraska Panhandle and far southeast Wyoming. Some severe
thunderstorms capable of 1 to 1.75" hail and gusts from 60 to 70 mph
are possible.
DISCUSSION...Satellite imagery shows a broad shortwave trough
progressing eastward across the northern Rockies/northern High
Plains. The airmass downstream from the NE Panhandle into the
central Dakotas continues to destabilize amid filtered daytime
heating and ample low-level moisture. Recent surface observations
show upper 60s dewpoints extending northward in the vicinity of a
pre-frontal trough from far southeast WY into central ND.
Expectation is for scattered to numerous thunderstorm development to
occur over the next few hours ahead of the approaching shortwave,
both along the cold front and pre-frontal trough. A predominately
linear mode is anticipated along the front, but a few supercells are
possible farther east along the lee trough where the buoyancy is
greater and the vertical shear vector is a bit more
southwesterly/westerly. Large hail around 1.75" is the primary
threat with any more cellular development. Gusts from 60 to 70 mph
will be the primary threat with the more linear storms. A Severe
Thunderstorm Watch will likely be needed to address this severe
potential.