BBS: TELESC.NET.BR
Assunto: MESO: Nws Weather Prediction Center College Park Md
De: COD Weather Processor
Data: Thu, 28 May 2026 21:10:06 +0000
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AWUS01 KWNH 282110
FFGMPD
ORZ000-290230-
Mesoscale Precipitation Discussion 0268
NWS Weather Prediction Center College Park MD
508 PM EDT Thu May 28 2026
Areas affected...central OR
Concerning...Heavy rainfall...Flash flooding possible
Valid 282107Z - 290230Z
Summary...Increasing thunderstorms coverage through the remainder
of the afternoon into the evening may lead to areas of flash
flooding across portions of central OR. Hourly rainfall over 1
inch is expected in a few locations along with 15-minutes rates of
0.25 to 0.75 inches. Total rainfall in a few locations may reach 2
inches.
Discussion...GOES West visible imagery showed the early stages of
convective development across southwestern ID into southeastern
OR, located north of an anomalous closed low centered over CA/NV.
Surface heating to the north of cloud cover over the southern
third of OR was contributing to decreasing convective inhibition
with MLCAPE of 500-1500 J/kg via 20Z SPC mesoanalysis data. Shear
parameters were sufficient for storm organization with individual
cell motions forecast from the E to NE, while clusters should have
more of a SE to NW movement. Any supercell structures would have
the slowest motions at ~15 kt (with other cell types faster), but
the combination of potential mesocyclones and the anomalous
moisture (PWs of 0.8 to 1.1 in the pre-convective environment)
will support precipitation efficiency and locally higher rainfall
rates.
Water vapor imagery identified a northward advancing shortwave
spoke over northeastern NV, on the eastern side of the closed low,
advancing toward southeastern OR. As this feature approaches
through 00Z, increasing DPVA and diffluence aloft should increase
convective coverage over central OR with an organized region of
showers/thunderstorms likely developing through 03Z. Embedded
hourly rainfall prior to and within the forecast convective
cluster are expected to surpass 1 inch but with 15-minute rates of
stronger cells in the 0.25 to 0.75 inch range. Given FFG across
much of OR, east of the Cascades, is only 1 to 1.5 inches in 1
hour (slightly lower/higher in various locations), some areas of
flash flooding will be possible as cell coverage and merger
potential increases through the evening. Due to fairly dry
antecedent conditions, flash flood potential will be most likely
across any urban areas or sensitive burn scar locations.
Otto
...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!88BI5Xzob7MxRvS0a25idYdXqE-cOwuq7lB0LOgElIXBl2sGfABzBF71XNlxVXetnUyq=
PXGl_Rj_QaMCghUnUOQiV5o$ for graphic product...
ATTN...WFO...BOI...MFR...PDT...PQR...
ATTN...RFC...PTR...RSA...NWC...
LAT...LON 45561958 45491897 45301828 44891795 44201824=20
43431888 42752000 42392114 42322202 42432242=20
42682253 43092260 43512258 43962249 44472229=20
45092188 45212141 45472053=20
=3D =3D =3D
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