Area Forecast Discussion
Issued by NWS Great Falls, MT
Issued by NWS Great Falls, MT
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186 FXUS65 KTFX 120232 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 832 PM MDT Thu Jul 11 2024 .SYNOPSIS... Hot and dry weather prevails across the region into next week beneath a strong upper level ridge of high pressure in place across the inter-mountain Western United States. Isolate shower and thunderstorm development is possible each afternoon with little to no measurable precipitation expected. && .UPDATE... Thunderstorms will continue across Judith Basin County and move into Fergus County within the next couple of hours. Frequent lightning, erratic wind gusts, and small hail are possible with these storms. For the rest of the night it will be dry across the area. Tomorrow it will be not as hot as today. For this evening`s update the hourly temperatures were adjusted. Dewpoints and RHs were tweaked to better reflect current observations and trends. Pops were increased in Judith Basin and Fergus Counties to better match current radar trends and Hi-res model guidance. Minor adjustments were made to wind, windgust, and sky grids. The rest of the forecast is on track. -IG && .AVIATION... 12/00Z TAF Period VFR conditions will prevail across all terminals during this TAF period. Due to being under an upper-level ridge mostly few to scattered hi-level clouds will be around all terminals with hot temperatures Thursday evening and Friday late morning through the end of the TAF period. Due to the hot-temperatures there will be density altitude concerns primarily Thursday evening and Friday afternoon through the end of the TAF period. Wildfire smoke will be around all terminals. This smoke has a low chance of local visibility reductions. There is a 10 - 20% chance for a shower or thunderstorms to impact the KLWT and KHLN terminals from now through 02Z. The greatest threat from a thunderstorm would be gusty, erratic winds. -IG Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .FIRE WEATHER... Near record heat and low humidity will continue to rapidly dry fuels and increase fire danger across the area with several fire weather concerns over the next several days. In addition to the heat and dryness today, localized gusty and erratic winds are possible this afternoon near any high-based showers and isolated thunderstorms along with the potential for isolated lightning. Hoenisch The next concern for fire weather will be on Saturday. Well above normal temperatures in combination with strong westerly flow aloft will create critical fire weather conditions across portions of central and southwestern Montana. Sustained winds over 15 mph are expected for much of fire weather zone 118 with a widespread 15 to 25% chance of sustained winds over 20 mph. Wind gusts over 25 mph are generally expected for most of the zone with a 15 to 25% chance of wind gusts over 35 mph, particularly for the southern portion of the zone. Minimum RH values are expected to range from 10 to 15% for most of the zone. It is worth mentioning that there are some concerning fire weather signatures for zone 117 on Saturday. However, from discussing fuel conditions and recent precipitation with fire weather partners, it sounds like most of the zone is about a week away from reaching critical conditions. Some parts of Meagher county in zone 117 will be of concern for potential fire growth and spread. But given the locality of these concerns in relation to the size of the zone, the decision was made to hold off on issuing a fire weather watch for zone 117. Looking further out in time, Sunday is expected to be much more marginal in terms of the fire weather setup. Low RH and warm temperatures will continue. However, winds are expected to be a little lighter and will pose less of a threat to fire suppression. The next time period to watch will be Monday and Tuesday afternoon for dry thunderstorms across central and southwestern Montana. There is still some model disagreement on the specifics with the dry thunderstorm potential but it will be something to watch in the coming days. -thor && .PREV DISCUSSION... /ISSUED 536 PM MDT Thu Jul 11 2024/ Isolated showers and thunderstorms will continue to pop up over the rest of the afternoon into the evening hours. Very little to no measurable precipitation is expected with these showers, however, there is a risk for gusty winds and cloud to ground lightning which will increase fire weather concerns heading into the weekend. For a more in-depth outlook at upcoming fire weather concerns, see the FIRE WEATHER section. -thor The weak disturbance moving over the ridge today results in some very minor cooling on Friday, mostly focused across north-central MT as weak surface high pressure temporarily moves across southern AB/SK, shifting winds to more northerly across the Plains. Heat will re-intensify across the area on Saturday as the upper level ridge strengthens a bit and becomes centered across the eastern Great Basin and central Rockies. A belt of stronger winds aloft also moves over the ridge Saturday, which will lead to at least breezy conditions, while an associated disturbance potentially supports some isolated high-based showers/thunderstorms across the central/SW MT mountains late Saturday and Saturday night. -Hoenisch Next week hot and dry conditions will continue from the strong ridge moving in from the west. High temperatures will be above average in the mid 90s, and overnight lows will remain in the 60s providing some relief from the high temperatures during the day. Opportunities for showers and thunderstorms will continue in Southwest Montana. Fire weather concerns will increase as fuels continue to dry out, and drier thunderstorms are also a risk because of the lightning and winds. -Kiffle && .PRELIMINARY POINT TEMPS/POPS... GTF 59 90 59 95 / 0 0 0 0 CTB 57 85 56 90 / 0 0 0 0 HLN 62 98 62 100 / 0 0 0 0 BZN 57 96 56 97 / 10 0 0 10 WYS 46 86 44 87 / 10 10 0 10 DLN 54 93 54 94 / 0 10 0 10 HVR 61 91 60 93 / 0 0 0 10 LWT 59 87 58 91 / 20 0 10 10 && .TFX WATCHES/WARNINGS/ADVISORIES... Fire Weather Watch from Saturday afternoon through Saturday evening for Helena and Townsend Ranger Districts of the Helena National Forest. && $$ http://www.weather.gov/greatfalls