BBS:      TELESC.NET.BR
Assunto:  MESO: Nws Weather Prediction Center College Park Md
De:       COD Weather Processor
Data:     Sun, 31 May 2026 03:44:16 +0000
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AWUS01 KWNH 310344
FFGMPD
SDZ000-310800-

Mesoscale Precipitation Discussion 0282
NWS Weather Prediction Center College Park MD
1142 PM EDT Sat May 30 2026

Areas affected...Northwestern South Dakota

Concerning...Heavy rainfall...Flash flooding possible

Valid 310342Z - 310800Z

SUMMARY... A drifting line of storms with a history of up to 4
inch/hour rain rates will continue to pose a diminishing flash
flooding threat as eastward motion slowly increases. Flash
flooding possible.

DISCUSSION...A very slow moving nearly north-south aligned line of
storms across western South Dakota has a history of 4 inch/hour
rainfall rates. An impressive 40+ kt low level jet is advecting a
moist air mass with PWATs to 1.4 inches towards the northwest
ahead of the line, with instability values between 1,000 and 2,000
J/kg. This line formed along a nearly stationary trough. An area
of low pressure over Wyoming is causing westerly winds behind the
line, resulting in an area of enhanced convergence near the line,
allowing the storms to persist. MRMS data show that where the
heaviest amounts of fallen southeast of Rapid City, rainfall
amounts have doubled FFGs. Since the line is still moving slowly,
and the outflow continues to produce lighter, but still
significant rainfall west of the line back to the Wyoming/Montana
border, the flash flooding threat will persist in these areas for
the next several hours.

Hi-res CAMs guidance and radar imagery shows a second line of
storms moving northward at the southern end of the main line. This
second line of storms should work to gradually disrupt the main
line as it pushes north and cuts off the moisture inflow to the
downstream main line. This will promote a faster eastward
progression of the entire MCS, which should occur over the next 3
hours or so. That faster movement should allow for the overall
flash flooding threat to reduce much more rapidly, especially with
a lack of diurnal heating leading to a natural diminishing of the
instability east of the MCS, despite the impressive advection.

Wegman

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!-wfWTOIlnUE-qcvcnZUI6xxozrQLwiED6ZRY9No1-Srqdg3K3aOfIsfrpNrvMZi5-T9T=
DRyNleiOED3--X2SFZrrNp4$  for graphic product...

ATTN...WFO...ABR...UNR...

ATTN...RFC...KRF...NWC...

LAT...LON   45710201 45680186 45660133 45550084 45200016=20
            44679998 44100002 43930024 43670089 43500180=20
            43450207 43560269 43750311 44080339 44470365=20
            44930371 45550369 45670281=20

=3D =3D =3D
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