An upper level low moving to the south along the Montana-Wyoming border, generated heavy rainfall across southern parts of northeast Montana, with some flash flooding impacts recorded in Petroleum County.
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Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS GGW wrote it up.
An upper level low moving to the south along the Montana-Wyoming border, generated heavy rainfall across southern parts of northeast Montana, with some flash flooding impacts recorded in Petroleum County.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Glasgow, MT wrote its last area forecast discussion before the first event at Jun 23, 7:10 PM MST, 2 hours earlier.
Area Forecast Discussion National Weather Service Glasgow MT 810 PM MDT Fri Jun 23 2023 .DISCUSSION... EVENING UPDATE: Have attempted to forecast into the next 9 hours based on radar, satellite trends and surface observations. Rain currently looks like it will make its way up to about the Missouri River before pausing and then making its way east. Center of the Low's vorticity looks to be over KBYZ and slowly beginning an eastward trek. THis will drag the rainshowers along the northern side of it across Petroleum, Garfield, and the lower Yellowstone Valley with it. Wind and wind gusts were also a little bit less than predicted by the NBM this evening and the hourlies were adjusted down 2 to 4 kts accordingly. Consequently, the Lake Wind Advisory will be cancelled about an hour early because of this. GAH AFTERNOON DISCUSSION: With the upper-level low pressure system now moving from Idaho into Wyoming, afternoon thunderstorms have already become widespread through northern Wyoming and southern Montana. The excessive rainfall outlook update from this afternoon has upgraded most of southern/southeastern Montana into a moderate risk. Given that this is usually our region's wet season, such an outlook is rare. We participated in an additional web briefing with NWS Billings and our combined partners. Several model analysis tools show this event today through tomorrow will be very unusually wet. The Flood Watch currently in effect remains well in place. For our CWA, our southern zones will be impacted with about 1 to 2 inches of rain and greater amounts south of there. Saturday through Saturday night, accumulating precipitation will persist, but will begin making an eastward exit into the Dakotas. With the Flood Watch in place, we will need to watch over our FFMP guidance and be prepared to issue any flood advisories or warnings, should they become necessary. Sunday through Monday morning, a weak, short-wave ridge of high pressure moves over our region, bringing mostly sunny skies and only isolated thunderstorms possible. Monday night and beyond, some semblance of a stalled weather pattern sets up again over our region which may bring a return to hot and muggy conditions, although the overall weather pattern seems confused and disorganized, thus low confidence. -----BMickelson && .AVIATION... UPDATED: 0200Z FLIGHT CAT: VFR - MVFR DISCUSSION: Approaching storm system from the southwest will bring deteriorating conditions to area TAF sites. KGDV will be more impacted with MVFR ceilings amid moderate thunderstorms and rain. Conditions will be less impactful for KSDY and and probably minimal for KGGW and KOLF. WINDS: East to northeast at 10 to 15 kts tonight through Saturday morning. becoming light and variable from west to east in the late afternoon Saturday. GAH && .GLASGOW WATCHES/WARNINGS/ADVISORIES... Flood Watch through late Saturday night for Dawson...Garfield... McCone...Petroleum...Prairie...Richland...Wibaux. && weather.gov/glasgow
Special Weather Statement
National Weather Service Glasgow MT
653 PM MDT Fri Jun 23 2023
MTZ021-240145-
Petroleum MT-
653 PM MDT Fri Jun 23 2023
...A strong thunderstorm will impact portions of southwestern
Petroleum County through 745 PM MDT...
At 651 PM MDT, Doppler radar was tracking a line of strong
thunderstorms near Winnett, moving southwest at 15 mph.
HAZARD...Winds in excess of 40 mph and pea size hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor damage to outdoor objects is
possible.
Locations impacted include...
Winnett, Flatwillow and Tiegen.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.
&&
LAT...LON 4718 10874 4719 10872 4723 10872 4730 10835
4675 10836 4675 10863 4684 10863 4684 10861
4710 10861 4710 10874
TIME...MOT...LOC 0051Z 064DEG 12KT 4704 10847
MAX HAIL SIZE...0.25 IN
MAX WIND GUST...40 MPH
BernhartThe Billings radar (KBLX), 101 km away, was scanning. The volume nearest the first event began at 04:11 UTC.
1 flash flood. Local standard time, as filed.
Law enforcement reported water flowing over the roadway on U.S. Highway 87 at mile marker 22.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2023Every state in 2023This day in weather historyWarnings in Montana, June 2023
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 1099877.