Area Forecast Discussion

KEY MESSAGES

- Warm and dry weather is expected through mid-day.

- Scattered showers and isolated thunderstorms are expected during the late afternoon to evening hours. Strong, gusty winds can be expected with some of these storms possibly being severe and up to 60 mph.

- A strong cold front will bring much colder conditions beginning tonight. General rain Thursday will likely transition to snow Thursday night and linger into Saturday.

- High winds may be possible Thursday afternoon.

DISCUSSION

WEATHER PATTERN OVERVIEW: The forecast for NE Montana over the next several days will be highly variable with strong swings in temperatures, precipiation amounts, and precipitation types. The 500-mb height field is characterized by a strong ridge of high pressure through the eastern Rockies and High Plains regions through today. This is expected to bring near record high temperatures to many locations.

late this afternoon and evening, an approaching strong low pressure system from the Great Basin and the Northern and Central Rocky Mountain Regions will provide enough of an unstable atmosphere to allow rain showers and isolated thunderstorms to develop. Convective outlook from SPC continues with just general thunderstorms, however the large temperature/dewpoint spread could support strong wind gusts which are evident in HREF Max wind gusts during this time span. The limiting factor may actually be too limited moisture which could limit convection in some locations in the south.

Fire weather concerns are also increased with the dry and warm conditions especially on Wednesday. Greenup is underway but not sufficient enough and Fire Weather Watches have been issued. Meanwhile downsloping from the warm front will likely drop RH lower than NBM ensembles initially suggest. Had to adjust for this.

As the system winds up and matures over our region, a strong cold front will sweep down from Saskatchewan generating rain Thursday and a rain/snow mix Thursday night. Gusty winds behind the front will easily be sustained in excess of 30 mph with gusts much higher mph.

By Friday morning and through most of the upcoming weekend, behind this strong cold front, temperatures will be cold enough to allow for a complete change over to all snow, especially near and north of the Hi-Line. Wind chills through this time range from 10 to 20 degrees above zero which is more of a shock compared to previous days.

Overall, total precipitation is expected to be anywhere between a few hundredths and a quarter inch, a drop from previous model runs. Snowfall could be 1 to 3 inches near the Canadian border and Little Rockies.

FORECAST CONFIDENCE & DEVIATIONS: Deviations from NBM include...

1. A re-work of today's late afternoon and evening PoPs to more evenly spread low chances for thunderstorms and rain showers over hourly data.

2. A lowering of today's MinRH and hourly RH to account for downsloping in the early afternoon hours.

3. and a blend of 50/50 NBM/NBM90 for wind and wind gust Thursday afternoon to account for CAA behind the cold frontal passage.

Confidence in the forecast is mostly MODERATE through roughly Monday.

AVIATION

UPDATED: 0345Z

FLIGHT CONDITION: VFR.

DISCUSSION: High clouds will stream into the region overnight with gradually decedning ceilings after about 18Z. scattered rain showers adn isolated thunderstorms will be possible in the late afternoon and evening hours today. Light Rain will become more steady after midnight with MVFR ceilings by mid-morning Thursday.

There is a chance that thundertorms could produce erratic severe gusty winds in the late afternoon and early evening hours near ther terminals. But, currently chances are too low to include int he TAFs directly.

LLWS: low level windd shear could have a impact of the terminals from 10 - 16Z this morning.

WIND: E to SE at 15 kts or less through the morning. Veering to the S and SW in the afternoon with gusts up to 25 kts. Veering farther to the W and NW after midnight and increasin to 15 to 25 kts gust 35 kts early Thursday morning.

GAH

GGW WATCHES / WARNINGS / ADVISORIES

Red Flag Warning from 9 AM to 9 PM MDT Wednesday for Dawson/McCone/Prairie/Richland/Wibaux Counties-Fort Peck Reservation and Daniels/Roosevelt/Sheridan Counties-Northern Valley and Northern Phillips Counties-Southern Petroleum and Southern Garfield Counties-The Little Rockies-The Lower Missouri River Breaks including the Charles M Russell National Wildlife Refuge.

High Wind Watch from late Wednesday night through Thursday afternoon for Central and Southeast Phillips-Central and Southern Valley-Garfield-Northern Phillips-Northern Valley- Petroleum-Southwest Phillips.

High Wind Watch from Thursday morning through Thursday evening for Daniels-Dawson-Eastern Roosevelt-McCone-Prairie-Richland- Sheridan-Western Roosevelt-Wibaux.