Marine Weather and Tide Forecast for Bellevue, ID

SHORT TERM /THROUGH FRIDAY NIGHT/
Issued at 308 AM MDT Thu May 22 2025

Satellite and radar checks this morning shows plenty of cloud cover moving through the Central Mountains and some more clouds throughout Eastern Idaho and while more organized showers remain well to our west in eastern Oregon, this activity will move eastward today. We've got a shortwave and weak cold front passing through today which will bring the best rain and storm chances to areas north of a line from Sun Valley to Idaho Falls to Driggs. It really will be the northern portion of the Sawtooths/Central Mountains, upper Snake River Plain, and Island Park area with about a 30 to 50 percent chance of thunder today. Around Idaho Falls, that chance drops to closer to 10 to 20 percent. That said, the NAM 3 km is definitely the more aggressive of the CAMs as it shows one main storm popping up near Idaho Falls/Rexburg this afternoon. In contrast, the HRRR keeps the Snake River Plain almost completely dry this afternoon. Both models do agree on showers and storms from the Stanley area tracking northeast through Challis and out of our CWA today. For our severe weather parameters today, model soundings from RAP and NAM Nest both agree on ample 0-6 km shear of some 50 to 70 kts and 700-500 mb lapse rates ranging from 8.5 to nearly 10 deg C/km, but there are some discrepancies on how much CAPE we have to work with. The NAM Nest ranges from about 600 to 800 J/kg while the RAP ranges from 300 to 500 J/kg.
The RAP shows better DCAPE values of almost 900 J/kg near the Idaho Falls area, so based off all of this if we can get a storm in this environment, strong wind gusts would likely be the main threat. The latest HRRR shows max wind gusts up to about 50 mph, though there is a small area of up to 60 mph near Challis this afternoon. In general, it will be a bit breezy this afternoon even outside of thunderstorms, with gusts around 30 to 35 mph in the eastern Magic Valley, South Hills, and Snake River Plain. We are near Lake Wind Advisory criteria on American Falls reservoir, but look to stay just shy of it or only reach the 20 mph sustained winds for an hour or two. We do have a Frost Advisory in effect out across the Arco Desert/Mud Lake area until 9 AM, but once temperatures get to warming we will be heading into the 70s this afternoon. Highs will be nearly a repeat on Friday even behind the weak cold front passing through with the shortwave today.

LONG TERM /SATURDAY THROUGH WEDNESDAY/
Issued at 308 AM MDT Thu May 22 2025

As a 500 mb trough works east over the Continental Divide on Saturday, afternoon showers and thunderstorms will continue ahead of dry conditions returning for Sunday into Monday as a ridge of high pressure builds in out of the west. While we may see some isolated showers and storms across extreme eastern Idaho on Sunday, conditions will remain dry elsewhere into Memorial Day as warmer temperatures build in. We will start off the holiday weekend with highs in the 60s/70s as the 70s/80s return for Sunday and Monday associated with prevailing southwest flow and sunny skies.

Our latest model guidance for Memorial Day keeps any shower and thunderstorm chances in the afternoon and evening very isolated with best chances up in the Central Mountains and Eastern Highlands. This is a result of where models remain in good agreement on shifting the 500 mb ridge axis east of our area, allowing for moisture to build back in out of the west. This will support at least the mention of isolated showers and thunderstorms in our latest forecast each afternoon and evening through the work week next week. We will have to see if any more organized plumes of moisture push into eastern Idaho next week but at this time, PWATs look to remain in that 0.25- 0.75" range which will keep precipitation chances more isolated in nature.
Temperatures through the work week next week look to stay fairly consistent each day associated with this pattern as highs remain in the 70s/80s, about 10-15 degrees above normal for late May.

AVIATION /12Z TAFS THROUGH 12Z FRIDAY/
Issued at 542 AM MDT Thu May 22 2025

Early morning satellite imagery shows mid/upper-level clouds continuing to build into eastern Idaho as a shortwave trough works east over the northern Rockies. Isolated showers and thunderstorms will accompany this trough later today with a 10-20% chance at KIDA and KSUN and a 20-30% chance at KDIJ. Have held off on the inclusion of any shower or thunderstorm mention in the TAFs at this time given lower confidence on placement and very dry air at the surface, which will need to be evaluated further later today. Primary hazards with any showers, virga, or thunderstorms today will center around gusty outflow winds in excess of 30 kts. Synoptic winds today will be breezy this afternoon with gusts to around 15-30 kts at all terminals.
Lighter winds and clearer skies will build in after sunset tonight as this system works east over the Continental Divide.

FIRE WEATHER
Issued at 308 AM MDT Thu May 22 2025

Temperatures continue to warm today with highs into the 70s in the eastern Magic Valley and throughout the Snake River Plain and 60s elsewhere. A weak shortwave and cold front will be working through Eastern Idaho, too, bringing a chance for showers and storms mainly north of a line from Sun Valley to Idaho Falls to Driggs. Strong wind gusts up to 50 mph will be the main threat with any storms today, but it will also be breezy outside of storms with widespread gusts of 30 to 35 mph. Total QPF from any storms today is expected to remain around or below a tenth of an inch.

PIH WATCHES/WARNINGS/ADVISORIES
Frost Advisory until 9 AM MDT this morning for IDZ052.