MD 0832 CONCERNING SEVERE POTENTIAL…WATCH POSSIBLE FOR NORTHEAST WA INTO THE ID PANHANDLE
Mesoscale Discussion 0832
NWS Storm Prediction Center Norman OK
0227 PM CDT Sun May 21 2023
Areas affected...Northeast WA into the ID Panhandle
Concerning...Severe potential...Watch possible
Valid 211927Z - 212130Z
Probability of Watch Issuance...40 percent
SUMMARY...Scattered thunderstorm development is expected later this
afternoon, with a threat for isolated severe hail and wind gusts.
The need for watch issuance is uncertain at this time.
DISCUSSION...Relatively strong diurnal heating is underway early
this afternoon across parts of eastern WA into northern ID. With dew
points in the low/mid 50s F amid warming temperatures, MLCAPE has
already increased into the 500-1000 J/kg range, and some further
destabilization is possible through the afternoon. Weak high-based
convection is ongoing across east-central WA, which may be
associated with a low-amplitude shortwave trough moving
northeastward in advance of a stronger mid/upper-level shortwave
approaching the Pacific Northwest coast. This area of ascent
combined with decreasing MLCINH is expected to result in stronger
thunderstorm development later this afternoon, with an east-west
oriented surface boundary across northeast WA expected to be a
primary focus for initiation.
Increasing midlevel flow will support sufficient vertical shear for
organized convection, especially near/north of the surface boundary,
where backed low-level flow will result in larger effective shear
magnitudes. A couple of supercells may evolve with time, posing a
threat of large hail and localized severe gusts. Storm coverage
south of the surface boundary is more uncertain, due to weaker
low-level convergence and a tendency for low-level moisture to mix
out with time.
With northeasterly storm motions expected across the area, storms
developing along the surface boundary and moving through the most
favorable environment may quickly move across the international
border into British Columbia. Due to the potentially limited
spatiotemporal extent of the threat, the need for watch issuance is
uncertain at this time.
..Dean/Grams.. 05/21/2023
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...OTX...
LAT...LON 47721784 48081938 49051953 49301878 49241744 49131655
48311641 47821701 47721784
