textproduct: Glasgow

KEY MESSAGES

- Accumulating rain showers and embedded thunderstorms at times going through 9 PM this evening beside low amounts in Petroleum and southwest Phillips counties.

- Winds will reach Lake Wind Advisory Criteria today. Wave heights will have the potential to reach 4 to 5 ft with localized areas to 6 feet on the widest parts of Fort Peck Lake.

- Slight chances for rain showers are possible Tuesday night and again Thursday night into the weekend.

DISCUSSION

A low pressure system is on its way into the area, and rain showers with weak thunderstorms have started moving into the west and southeast parts of the area. This activity is expected to increase and persist through 16Z, and moderate to heavy rain is expected at times. As the system pivots northeastward, a break in the rain is expected briefly before scattered showers and weak storms move back in after 12 PM. This activity is expected to leave the area after 8 PM. Winds will also come up after 8 AM this morning. These west to northwest winds have potential to gust to around 45 to 55 mph through about 8 PM before they gradually decrease in the late evening.

The best chance for rain is through noon today, and the highest amounts are expected on a line from Malta to Jordan. Up to 9 tenths of an inch is possible in the northeast, and two tenths to a half inch in the southeast part of the area. The wind will make the rain do some sideways action, so an extremely sturdy umbrella will be needed. Maybe an umbrella made out of titanium or something.

This system will move out late tomorrow evening, but a splitting upper trough over the western CONUS will remain. This will contribute to a chance of showers moving into the northwest and southeast parts of the area. There is indication that any rain amounts will remain below a wetting rain (one tenth of an inch of accumulation).

Weak ridging is expected to move in on Wednesday and last through Thursday afternoon before the next trough tries to move in from the south on Thursday evening. There is moderate to high uncertainty on the strength of the trough, so rainfall amounts are not reliable enough to talk about in this forecast update.

FORECAST CONFIDENCE & DEVIATIONS:

The main deviation was to increase PoPs at various times through 9 PM this evening.

There is high confidence in winds across the area, and moderate confidence in rainfall amounts through 9 PM today.

There is high confidence in timing of the next ridge, and low to moderate confidence on the next trough.

AVIATION

LAST UPDATED: 0630Z

FLIGHT CAT RANGE: VFR through 09Z, then a mix of MVFR and IFR.

DISCUSSION: A low pressure system is moving in and is already bringing scattered showers and weak thunderstorms to KSDY and KGDV. There is moderate to high (50 to 70 percent) confidence of visibility dropping to 2 miles in heavy showers between 10Z and 15Z. There is low to moderate confidence of visibility lingering around 6 miles for KOLF and KGGW after 15Z, and for showers to linger for all sites between 19Z and 02Z.

SFC WIND: Southeast at 8 to 16 knots becoming west at 10 to 20 knots with gusts to 30 knots after 14Z, increasing to 20 to 30 knots with gusts to 45 knots after 18Z.

LLWS: There is low confidence of southerly low level wind shear with gusts to 40 knots through 09Z for KSDY and KGDV.

GGW WATCHES/WARNINGS/ADVISORIES

Lake Wind Advisory until midnight MDT tonight for Central and Southeast Phillips-Central and Southern Valley-Garfield-McCone- Petroleum.