Area Forecast Discussion
Issued by NWS Spokane, WA
Issued by NWS Spokane, WA
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261 FXUS66 KOTX 300456 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 956 PM PDT Wed May 29 2024 .SYNOPSIS... Areas of near or below freezing temperatures are expected Thursday morning and again for Friday morning. Drier weather is expected Thursday and Friday. A chance of mountain showers returns on Saturday followed by widespread rain late Sunday and Monday next week. There is increasing confidence for above normal temperatures for the latter half of next week. && .DISCUSSION... Today through Friday: The main threat for today is widespread gusty showers with isolated wind gusts up to 50 mph. Thanks to a cold upper trough and surface heating from this morning, widespread shower activity has sparked in the entire Inland NW. As daytime heating wears off, the pressure gradient that is delivering gusty winds will also relax. MOS guidance is still hinting at sub- freezing temperatures in the northeast Washington valleys, so I upgraded the freeze watch to a freeze warning. I also issued a broader frost advisory for the Idaho Panhandle, parts of the Columbia Basin/Spokane area, Palouse, and Methow Valley but this carries lower confidence. There is a 30-50% chance of temperatures cooler than 35 degrees in the frost advisory and a 60-80% chance of temperatures cooler than 33 degrees in the freeze warning. Currently the freeze warning encompasses through Friday morning as there is moderate confidence for 2 nights of freeze potential while the frost advisory only covers tonight. The temperatures appear to be warmer tomorrow night in the frost advisory area, lowering the risk. This will be reevaluated based on how tonight goes and if the models change. Tomorrow appears much drier but models still have a few weak showers over northeastern Washington and north Idaho. High temperatures will reach into the 60s despite a cold start in the 30s and low 40s tonight. Friday also looks dry and mild with highs in the upper 60s to upper 70s. /Butler Saturday and Sunday: A weak trough will move across the region Saturday with a quick broad shortwave ridge for Sunday. Showers and thunderstorms will occur mainly in the afternoon and evening hours across the mountainous areas of eastern WA and most of the Idaho Panhandle. Temperatures Saturday will be in the 70s, which is near average. Sunday we cool several degrees as thick dense clouds move in during the afternoon preventing additional heating. ...Beneficial rains for the Inland Northwest Monday... Sunday night through Wednesday: A large tap of Pacific moisture moving along the base of a strong low pressure system will move into the region beginning Sunday and continue through Monday. 190-200% of normal precipitable water values will be widepsread across the region. Precipitation chances will begin to increase late Sunday afternoon and evening and continue through Monday. Widespread rains are expected. We are still several days out, but precipitation amounts are looking to be near a tenth of an inch to a quarter of an inch in the valleys and lower elevations of central WA; 0.40 to 0.80 for the valleys of eastern WA and north ID; and over an inch along the crest of the Cascades, and the mountains of extreme northeast WA and the ID Panhandle. These rains will be beneficial to the region, creating rises on local creeks, streams and rivers. Some ponding of water is possible for areas that do not have proper drainage. Temperatures will remain on the cool side with highs in the 60s to around 70 through Tuesday. Monday there will be some breezy to gusty southwest to west winds as a trough passes. There is a 50-60% chance of gusts over 30 mph across the Waterville Plateau and onto portions of the Columbia Basin. Showers remain in the forecast for Tuesday as 57% of the ensembles support the parent low remaining to the northwest providing west or southwest flow and potential additional waves moving into the region. Wednesday onward a ridge will build somewhere over the western US. There are some discrepancies of where the ridge sets up, which will directly impact how hot we will get. For now, plan on warming conditions. 60% of the ensembles support a ridge with temperatures around 90 in the Columbia Basin and 80s for the valleys. /Nisbet && .AVIATION... 06Z TAFS: Convection is winding down with the loss of daytime heating with just a few residual showers left in north Idaho and down around the Blue Mountains. The showers moistened the boundary layer over N Idaho Panhandle and around Spokane Felts Field with the relative humidity already at 85-100% at some locations. While the models are showing very little chances for fog, current RH, clearing skies, and light winds does support as least some patchy fog development. Given drier air above the boundary layer with NW winds, confidence in coverage is low, but did indicate a TEMPO group for IFR conditions at KSFF/KCOE. Thursday will not be as unstable, but afternoon heating will trigger scattered to broken flat cumulus over much of Eastern Washington and North Idaho especially over the higher terrain. Slightly greater instability over the North Idaho Panhandle will lead to a 20 percent chance of a shower or thunderstorm at Sandpoint between 21z Thu-02z Fri. FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: Convection is high for VFR conditions at KGEG/KLWS/KEAT/KMWH. Confidence is lowest for KSFF/KCOE where a moist boundary layer left over from recent showers could lead to fog development overnight. Fog has the potential to impact Bonners Ferry, Sandpoint, Coeur d`Alene, and Kellogg as well. JW ----------------------- Confidence descriptors: Low - Less than a 30 percent chance Moderate - 30 to 70 percent chance High - Greater than a 70 percent chance For additional probabilistic information for NWS Spokane airports, please refer to the Aviation Dashboard on our webpage: https:/www.weather.gov/otx/avndashboard && .PRELIMINARY POINT TEMPS/POPS... Spokane 37 65 35 71 49 73 / 50 0 0 0 0 10 Coeur d`Alene 36 62 37 69 46 70 / 70 0 0 0 0 10 Pullman 35 61 37 68 47 69 / 60 0 0 0 0 10 Lewiston 42 69 44 77 53 79 / 50 0 0 0 0 10 Colville 32 65 34 71 42 69 / 60 0 0 0 0 30 Sandpoint 36 61 37 67 44 68 / 80 20 0 0 0 20 Kellogg 38 59 39 66 49 67 / 80 10 0 0 0 20 Moses Lake 36 71 38 76 51 79 / 10 0 0 0 0 0 Wenatchee 41 69 44 75 57 74 / 10 0 0 0 0 0 Omak 36 71 39 75 51 75 / 10 0 0 0 0 10 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...Frost Advisory from 2 AM to 8 AM PDT Thursday for Central Panhandle Mountains-Idaho Palouse-Northern Panhandle. WA...Frost Advisory from 2 AM to 8 AM PDT Thursday for Spokane Area- Upper Columbia Basin-Washington Palouse-Western Okanogan County. Freeze Warning from 2 AM Thursday to 8 AM PDT Friday for Northeast Mountains-Okanogan Highlands. && $$