textproduct: Glasgow

KEY MESSAGES

- Scattered thunderstorms are expected to track southeast from Canada into Daniels, Sheridan, Eastern Roosevelt, Richland, and Wibaux Counties before pushing into North Dakota Sunday evening.

- A cooler and more unsettled weather pattern is expected to emerge each day this week with scattered showers and thunderstorms each day.

DISCUSSION

WEATHER PATTERN OVERVIEW:

The main forecast challenge for Sunday looks to be convective potential for the eastern zones along the MT/ND border this afternoon and evening as a shortwave flattens the ridge. HREF max ensemble wind gust and updraft helicity guidance as well as ensemble 40dbz reflectivity all show consensus on what is expected to unfold. Storms that develop will track southeast from Canada into Daniels, Sheridan, Eastern Roosevelt, Richland, and Wibaux Counties before pushing into North Dakota. Timing looks to be between about 3PM and 8PM on the Montana side. A few of these storms may be strong to severe with damaging wind gusts to 60 mph with hail as a secondary threat.

Of note, the SPC D1 outlook carries a Marginal Risk for severe thunderstorms in our eastern zones with a slight risk right up against the MT/ND border. Zonal flow with various shortwaves look to continue at times through the remainder of the week as a trough begins to set up over the Pacific Northwest. This will lead to cooler temperatures but more active chances for showers and thunderstorms each day. Ensemble guidance has trended higher for the QPF, notably for the second half of the week. Probabilities are increasing that much of NE Montana will see beneficial rainfall during this time. As this is further out in the forecast period, days 5 through 7, will await run to run continuity before having much confidence in the details, but this will be the next period worth focusing in on.

FORECAST CONFIDENCE & DEVIATIONS:

Pops were adjusted near term in collaboration with neighbors and to better reflect the expected convective evolution for Sunday afternoon and evening. Confidence is growing on an isolated severe threat this afternoon and evening across the eastern zones as suggested by excellent high resolution model consensus. Confidence also continues to emerge toward a wetter and more active pattern this week, especially for the second half.

AVIATION

LAST UPDATE: Sunday August 9 at 545Z.

FLIGHT CAT RANGE: VFR.

DISCUSSION: Sky will tend toward mostly clear this morning with a few or scattered mid level clouds by afternoon. Haze is expected to continue at times from wildfire smoke, but not enough of a surface impact to reduce visibilities.

WIND: Southeast winds will continue Sunday morning at 10 to 20 kts, becoming north to northwest between 00z and 06z. Winds will then become northeast again at a 5 to 15 kt range overnight.

GGW WATCHES/WARNINGS/ADVISORIES

None.