Area Forecast Discussion
Issued by NWS Pocatello, ID
Issued by NWS Pocatello, ID
191 FXUS65 KPIH 241002 AFDPIH Area Forecast Discussion National Weather Service Pocatello ID 402 AM MDT Fri May 24 2024 .SHORT TERM...TODAY THROUGH SATURDAY NIGHT... Expect a general break between storm systems today with a FROST ADVISORY continuing through 9 AM for the ern Magic Valley and Snake Plain corridor, but with warmer high temps reaching the upper 50s to upper 60s this afternoon. Our next low pressure system is still expected to drop across the forecast area Sat, with showers and at least a few afternoon t-storms. Models might be trending a bit drier overall with QPF and shower/storm coverage with this system, with perhaps an initial round of light morning showers followed by isolated to scattered convective development during the afternoon, mostly in the mntns across the ern half of our forecast area. The AM showers and cloud cover may take the edge off t-storm potential, but the NAM Nest (representing a "high end" scenario) still insists on decent CAPE (instability) as high as 1,000 J/kg (although with weak shear), plus the trough will be overhead and portions of the CWA may be in the vicinity of the left-exit region of a modest mid-level jet. We`ll continue to monitor trends in how high-res, model- simulated reflectivity handles this activity, and have continued to allow the NBM to paint in widespread PoPs and thunder for the forecast. With respect to winds, the NBM backed off quite a bit this time yesterday, but has trended back up this AM, suggesting we may be close to WIND ADVISORY criteria Sat afternoon over the Mud Lake region. 700mb flow looks modest at 30-35kts, although 850-700mb lapse rates may be enough to mix most of that down. HREF winds are also coming in a bit lower than NBM. All-in-all, expect breezy conditions, and we`ll continue to monitor trends in the guidance with respect to any needed alerts. 01 .LONG TERM...SUNDAY THROUGH NEXT FRIDAY... Remnants of Saturday low shifts east of the region, allowing for dry conditions as upper ridge begins to build. Ridge lasts through Monday, but some of the ensembles are starting to show some moisture incursion into East Idaho as early as Tuesday as next trough toward the PacNW coast. Interestingly, the 12Z ensemble clusters favor ridge axis over East Idaho or just slightly east, so the heavier moisture push and increased precipitation potential appears to be related to faster 00Z solutions. Moving into the remainder of the extended, and especially in line with this faster shift, the models are showing some differences in how (or even if) the trough shifts through East Idaho, with the ECMWF closing off the low over the PacNW while the GFS shifts the open trough east. NBM holds on to weak precip chances mainly over higher terrain regions for the remainder of the week. The good news is that even the low end probabilistic guidance supports temperatures remaining warm enough, that hopefully further Frost/Freeze headlines won`t be needed, fingers crossed. DMH && .AVIATION... In general, VFR conditions are forecast for all East Idaho terminals through today, though KDIJ may see MVFR CIGS early. The next system rolls in overnight through Saturday, with CIGS beginning to lower west to east across the region mainly around/after 06Z starting at KSUN. VCSH SHRA begins at KSUN around 09Z, increasing in confidence and spreading to the remainder of the terminals by around 15Z Saturday morning. Winds start to increase again after sunrise Saturday as well. DMH && .FIRE WEATHER... Dry conditions today give way to an increase in precipitation chances overnight into Saturday as the brief upper ridge breaks down once again. Higher elevations, particularly the Caribou- Targhee areas, see the best precipitation potential into Saturday and Saturday night as the shortwave features pushes through. Isolated thunderstorms will be possible. Snow levels rise to Winds are expected to increase once again across the Snake Plain Saturday, strongest across the middle of Zone 410. Shortwave feature shifts east into the Plains Saturday night into Sunday, allowing another ridge to build into East Idaho for Sunday into Monday. There is still some uncertainty as to timing of the ridge breaking down around mid week, but showers and thunderstorms are expected in the Tuesday/Wednesday time frame. DMH && .PIH WATCHES/WARNINGS/ADVISORIES... Frost Advisory until 9 AM MDT this morning for IDZ051>055. && $$