216 FXUS65 KGGW 252102 AFDGGW Area Forecast Discussion National Weather Service Glasgow MT 302 PM MDT Thu Apr 25 2024 .DISCUSSION... KEY MESSAGES: 1) An increase in instability for areas mainly south of I-94 maintains chances for thunderstorms with gusty winds through this evening. 2) For Friday, elevated to critical fire weather conditions due to low humidity and gusty winds prompt a Red Flag Warning for northeastern portions of the area. 3) Look for a gradual temperature increase expected in the upcoming week with isolated chances for precipitation. WEATHER PATTERN OVERVIEW: Surface low pressure strengthens along a north-to-south boundary extending from eastern Montana down into the eastern plains of Colorado. A shortwave trough aloft, moisture transport in the low and mid-levels, and temperatures 10-20 degrees above normal will increase instability for locations east of this boundary. For northeast Montana, this is area is focused south of I-94. Convection initiation is occurring this afternoon off the higher terrain in southeast Montana and south Dakota, though a few of these storms may develop closer to the Yellowstone River Valley. Any storms that do develop will pulse up and down, with the greatest threat in the strongest of storms being hail. Any storms that continue beyond the end of daytime heating this evening will quickly diminish as they move to the northeast. Further discussion regarding a Red Flag Warning issued for Friday can be found in the fire weather section below. From Sunday, the southwest flow aloft will bring bouts of isolated to scattered showers from Monday into Thursday and an increasing temperature trend through the end of the week. CONFIDENCE AND POTENTIAL DEVIATIONS FROM BASE FORECAST: Given that actual RH values have tended to fall below NBM guidance particularly for far NE Montana, a reduction of around 3% in RH values was made accordingly on Friday. Otherwise, there is high confidence for temperatures into early next week and medium confidence for the wind forecast on Friday. -Enriquez/Zanker && .AVIATION... LAST UPDATED: 2100Z FLIGHT CAT RANGE: VFR (MVFR in shower/thunderstorm) DISCUSSION: Primarily mid level clouds are moving through the region. Late this afternoon and evening, convective showers and a few thunderstorms have a medium (30-40%) chance to briefly impact KSDY and KGDV. Any outflow boundaries may lead to a sudden erratic wind shift and higher gusts. && .FIRE WEATHER... An upgrade to a Red Flag Warning from noon through 8pm Friday has been made for zones 120 and 122, along with zone 134 added in. An increase in shower and thunderstorm activity with their associated outflow boundaries may at times bring gusty and erratic winds mainly south of I-94 through the early evening hours today. On Friday, winds gusting as high as 35 mph with humidity as low as 17 percent increases fire risk for far northeast Montana in particular, thus prompting an upgrade to a Red Flag Warning from noon through 8 PM. There is high confidence for critical conditions from the low RH and wind combo across zone 120 and more moderate confidence for zones 122 and 134. Precipitation over the last two weeks has been much below normal along with fuel moisture deficits. Fire weather concerns decrease over the weekend as winds back off. && .GGW WATCHES/WARNINGS/ADVISORIES... Red Flag Warning from noon to 8 PM MDT Friday for Dawson/McCone/Prairie/Richland/Wibaux Counties-Fort Peck Reservation and Daniels/Roosevelt/Sheridan Counties-Northern Valley and Northern Phillips Counties. && $$ weather.gov/glasgow |