Area Forecast Discussion

KEY MESSAGES

- A Flood Watch is in effect through tomorrow evening for Petroleum, Garfield, Prairie, Dawson and Wibaux Counties. There is a decent chance of moderate rain south of MT 200 from Winnett to Glendive as well as south of I-94 through Wibaux. Embedded thunderstorms are possible and can cause local heavier rainfall. Light rain is possible north of the Missouri River tonight into tomorrow morning.

- A moderately strong ridge is expected to move in on Monday, which will bring above average temperatures from Tuesday through Friday.

DISCUSSION

SYNOPTIC SETUP:

A low pressure system over Idaho this morning is tracking east across southern Montana and northern Wyoming for the rest of today and tomorrow. This system is cutoff by a northern stream shallow ridge in the Canadian Prairies which is leading to dry air cutting off areas north of a line from Malta to Medicine Lake. There has already been over an inch of rain in southern Garfield County. This will in our awareness through tomorrow. There may even be an extension to the Flood Advisory that is in effect there. Up to an additional half inch of rain is expected for southern Garfield County. This includes Prairie, Dawson, Wibaux, and the southern half of Richland county through noon Sunday before the system moves east.

A moderately strong ridge is expected to move in on Monday, and temperatures are expected to rebound above average from Tuesday through Friday. There may be a shortwave trough across the southeast to bring a slight chance of precipitation on Wednesday evening though.

FORECAST CONFIDENCE & DEVIATIONS: The only deviation was to increase winds at high elevation locations through tomorrow.

There is moderate to high confidence in rainfall amounts through tomorrow evening.

There is high confidence of an upper ridge moving in on Monday, and low confidence on accumulating precipitation moving in on Wednesday evening.

AVIATION

LAST UPDATED: 1830Z

FLIGHT CAT RANGE: For KOLF and KGGW, VFR becoming IFR after 07Z, becoming LIFR after 12Z (near airport shutdown for ceilings), becoming IFR after 21Z Sunday.

For KSDY and KGDV, MVFR/IFR becoming IFR/LIFR after 07Z (near airport shutdown from 12Z to 18Z for ceilings).

DISCUSSION:

Scattered showers are occurring around KSDY and KGDV with mostly low clouds in the area currently. The rain showers are expected to progress northward over KGGW and KOLF by 06Z. There is moderate to high (50 to 70 percent) confidence of IFR conditions occurring (please refer to the timing above the DISCUSSION section). There is low to moderate (30 to 50 percent) confidence of LIFR occurring for all sites from 12Z to 18Z. There is low to moderate confidence of moderate to heavy rain occurring from 06Z to 15Z for KSDY and KGDV as well.

SFC Wind: Ranging from northeast at 7 to 17 knots with gusts to 22 knots becoming southeast after 18Z for all sites.

GGW WATCHES / WARNINGS / ADVISORIES

Flood Watch through Sunday afternoon for Dawson-Garfield- Petroleum-Prairie-Wibaux.