Area Forecast Discussion
Issued by NWS Boise, ID
Issued by NWS Boise, ID
812 FXUS65 KBOI 050232 AFDBOI Area Forecast Discussion National Weather Service Boise ID 832 PM MDT Thu Jul 4 2024 .DISCUSSION...This evening will continue to be warm with light winds and clear skies. Winds will continue to diminish as the sun sets, generally blowing from the west-northwest at 5-10 mph in the Western Snake River Plain. On Friday, an upper-level ridge will build along the coast, tightening the pressure gradient across the forecast area as low pressure remains over the northern plains. This will increase surface winds Friday afternoon, especially from Mountain Home through the Western Magic Valley. Temperatures will rise by another 5 degrees, reaching the mid-90s in the valley. Surface winds will further increase on Saturday as a shortwave and jet max move through the northwesterly flow. Expect dry conditions with wind gusts up to 35 mph and temperatures close to 100 degrees in the lower valleys. A heat wave is expected to begin on Sunday across the Intermountain West, with temperatures likely to exceed 100 degrees and continue through at least next Thursday. The NBM and GFS models remain on the higher end of all temperature guidance, with the deterministic GFS being the highest, sometimes by over 5 degrees. There is about a 25% chance that temperatures could exceed 109 degrees on Wednesday and Thursday.Most guidance shows monsoonal moisture from the southwestern U.S. reaching the region by Wednesday, which is typical with this synoptic pattern. The increased cloud cover could keep temperatures from reaching their full potential. The Excessive Heat Watch has been updated to include the West Central and Boise Mountain valleys and Camas Prairie from Tuesday through Thursday. Winds for Friday and Saturday have also been updated as the latest guidance indicates higher winds. Sent the forecast update out 8 PM MDT. && .AVIATION...VFR. Haze from fireworks is likely near populated areas. Surface winds: W to NW 5-15 kt becoming variable 10 kt or less overnight. Winds aloft at 10kft MSL: NW 10-20 kt. KBOI...VFR. Haze from fireworks is likely. W to NW 5-15 kt, becoming variable or southeast 3-6 kt after 05/05Z. Then W to NW 5-15 kt Friday afternoon. Weekend Outlook...VFR and mostly clear. High density altitude due to hot temperatures. Variable winds less than 10 kt during the late evenings through mornings, and generally NW 5-15 kt with gusts of 15- 25 kt during the afternoons and early evenings. && .PREV DISCUSSION... SHORT TERM...Tonight through Saturday night...Dry and getting hot. The Excessive Heat Watch will be maintained this afternoon with no changes. The models are consistent with their depiction of an extreme heat event beginning Saturday and extending deep into next week. Temps Friday will be around 5 degrees above normal, but will be closer to 10 above normal Saturday. There`s roughly a 60% chance of getting to 100 in Ontario Saturday, and around a 30% chance in Caldwell/Nampa/Meridian/Boise/Mountain Home. Breezy conditions will develop mainly south and east of Mountain Home tomorrow afternoon/evening, and again and even stronger Saturday afternoon. This, along with low RH values, has resulted in the issuance of a Fire Weather Watch (see the fire weather watch for details). So please be careful with fireworks - any fires that get started tonight will have an above-normal chance to really get going tomorrow and into the weekend. LONG TERM...Sunday through Thursday...Temps will remain hot and get hotter through the long term period. The latest forecast calls for readings above 100 in lower elevations Monday through Thursday, with Wed and Thu expected top be the hottest days. Records will be set through this period in many locations, and all-time records may be reached. The all-time record for Boise, for example, is 111. The latest forecast for Wed is 108, but there`s a 40% chance of above 110 according to the NBM. Moisture will eventually work its way around the west side of the ridge and into our area next week, but uncertainty in timing is high. Cloud cover associated with this moisture is the main factor bringing uncertainty to the temperature forecast, as the models are very consistent with the overall pattern. && .BOI WATCHES/WARNINGS/ADVISORIES... ID...Excessive Heat Watch from Tuesday morning through Thursday evening IDZ011-013-028. Excessive Heat Watch from Saturday afternoon through Thursday evening IDZ012-029. Fire Weather Watch Friday evening IDZ424-426. Excessive Heat Watch from Monday afternoon through Thursday evening IDZ014>016-030-033. OR...Excessive Heat Watch from Saturday afternoon through Thursday evening ORZ061>064. && $$ www.weather.gov/Boise Interact with us via social media: www.facebook.com/NWSBoise www.twitter.com/NWSBoise DISCUSSION...JDS AVIATION.....SH SHORT TERM...SP LONG TERM....SP