FXUS66 KOTX 291822 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 1122 AM PDT Wed May 29 2024 .SYNOPSIS... A cool and showery day with afternoon thunderstorms will occur today, followed by areas of frost overnight into Thursday morning and again for Friday morning. Drier weather is expected Thursday and Friday. A chance of mountain showers returns on Saturday followed by the potential for more widespread rain early next week. There is increasing confidence for above normal temperatures for the latter half of next week. && .DISCUSSION... Today through Thursday night: Cold front swung through yesterday making way for the cold upper level trough to make its entrance today. A -28 Celsius cold pool at 500 mbs will move in right over the eastern Washington by this afternoon. This will result in steepening mid level lapse rates with a conditionally unstable atmosphere. All we need is the sun, and there will be plenty of that early in the day to erode the inversion and destabilize the lower levels of the atmosphere. Skinny CAPE in the neighborhood of 200-400 J/kg is expected by peak heating this afternoon. The northern mountains of eastern Washington will destabilize first by 11AM this morning, followed by the higher terrain in the Panhandle by noon, and then the Columbia Basin between 1-2PM. By 2-5PM, widely scattered showers can be expected regionwide. Chances will be less (10-20%) in the lee of the Cascades, to around 40-60% in the Spokane/Cd'A areas and Palouse, to 60-80% across the higher terrain of northeast Washington and the Idaho Panhandle. Thunderstorms will be more likely today compared to yesterday: the Columbia Basin will see a 15% chance for thunderstorms up to around 30% chances over the Northeast Mountains into the Idaho Panhandle. Thunderstorms will develop in a weak shear environment meaning that storms will collapse fairly quickly and spit out up to a handful of lightning strikes before decaying. Other hazards that can be expected are gusty outflow winds of up to 40 mph, pea sized hail, and brief heavy downpours. Have a plan to seek shelter if deciding to enjoy outdoor activities this afternoon or evening. Winds will continue to be breezy through this afternoon and evening with gusts of up to 30-35 mph with the synoptically forced winds. As previously mentioned, these winds may be enhanced with convection today. Showers and cloud cover will dissipate quickly with the loss of daytime heating this evening. The focus for tonight will turn to widespread frost development. Drier air will continue to funnel in with yesterday's frontal passage. Dew points are expected to dip down into the upper 20s. Winds will weaken overnight, but won't completely die off across the exposed areas of the Columbia Basin. Air flow across these areas from Wenatchee to Moses Lake, Ritzville, Davenport, Spokane, and the Palouse region will keep temperatures from bottoming out near freezing. Winds will die off however in the northern mountain valleys overnight and low temperatures have been lowered to between 30-34 degrees across much of the lower elevations there. This include Republic, Colville, Chewelah, Deer Park, Newport, Ione, and Metaline Falls to name a handful of communities. These areas are under a freeze watch that includes tonight and Thursday night. Winds will be even weaker Thursday night without much increase in temperatures aloft, which should result in a second night of strong radiational cooling and the potential for freezing temperatures again. There will be pockets in the Cascades and the Idaho Panhandle that may reach freezing, but not widespread enough to warrant a freeze watch. More areas may require a frost advisory tonight, and possibly for Thursday night as well. Take action now to protect crops or sensitive vegetation from frost or freeze damage. Ridging of higher pressure will be nosing in on Thursday resulting in a mush drier day. We are hanging on to isolated showers across the far northeast portion of the region, which mainly just includes the Northern Panhandle. Equilibrium levels don't look to be high enough to achieve the charge separation needed for thunderstorm development Thursday afternoon. /SVH Friday through Tuesday: Dry conditions and seasonably warm conditions are forecast for Friday under a brief period of ridging. And while some uncertainty does remain for the weekend into early next week, we are anticipating increasing chances for showers, especially by Sunday night and Monday. Occasionally breezy winds are also expected each day, though any gusts are currently looking to remain below 30 mph. Beyond the 7-day forecast, building high pressure is looking more likely for late next week with much warmer temperatures favored. /KD && .AVIATION... 18Z TAFS: Drier air behind a cold front will promote VFR conditions today. Winds will also be breezy due to cold air advection behind the cold front with west winds gusting to 20-25 kts with locally stronger gusts. Some of these enhanced gusts will occur this afternoon as showers increase across the region. Convective allowing models (CAMs) are in good agreement of locally enhanced gusts as high as 35-40 kts, but location and timing carry very low confidence. Isolated thunderstorms are expected as well, with the best chances over Northeast Washington into the Idaho Panhandle. There will be enough instability for thunderstorm chances down into the Spokane/Coeur d'Alene area and the Palouse after 21Z. Hazards with thunderstorms may include gusty outflow winds, pea sized hail, and brief heavy downpours with visibility down to around 4SM. /SVH FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: Convection is expand across much of the Inland Northwest after 18Z today. However, there is low confidence for thunderstorms to impact airport terminals: less than 10% chance for KEAT-KEPH-KMHW, a 15-25% chance for KLWS-KPUW-KGEG-KSFF, and a 30% chance at KCOE. /SVH ----------------------- 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 60 37 65 35 71 48 / 60 50 0 0 0 0 Coeur d'Alene 58 36 62 37 69 46 / 70 70 0 0 0 0 Pullman 57 35 60 37 68 47 / 40 60 0 0 0 0 Lewiston 67 42 70 44 77 53 / 40 50 0 0 0 0 Colville 59 32 65 34 71 43 / 80 60 0 0 0 0 Sandpoint 58 36 61 37 67 45 / 90 80 20 0 0 0 Kellogg 55 38 59 39 67 48 / 60 80 10 0 0 0 Moses Lake 66 36 72 38 76 53 / 30 10 0 0 0 0 Wenatchee 64 41 69 44 75 56 / 20 10 0 0 0 0 Omak 65 36 70 39 75 50 / 40 10 0 0 0 0 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...None. WA...Freeze Watch from late tonight through Friday morning for Northeast Mountains-Okanogan Highlands. && $$