Area Forecast Discussion
Issued by NWS Spokane, WA

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000 FXUS66 KOTX 031757 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 1057 AM PDT Mon Aug 3 2020 .SYNOPSIS... Temperatures will cool a bit today in the wake of a Pacific front, but the weather will quickly warm back up on Tuesday and Wednesday. A much stronger cold front will blast through the area on Thursday. This will bring strong winds along with a threat of showers and thunderstorms. Friday will be rather cool with many locations staying below 80 degrees. The weekend looks mild and breezy. && .DISCUSSION... Today: A cold front racing through the state this morning is bringing a few clouds to our area and is clearly seen on GOES satellite imagery. As this cold front moves through, an isolated sprinkle or two is possible but that will be the extent of precipitation as the atmosphere is still very dry. Cooler air moving in behind this front will drop daytime temperatures today with highs 3 to 5 degrees cooler than what was observed on Sunday. It will still be a bit breezy in the lee of the Cascades today while minimum RH values bottom out between 20 and 25 percent. This will translate to elevated fire weather conditions but the threat will quickly diminish after sunset. Tuesday and Wednesday: Upper level ridging will gradually build over the Pacific Northwest pushing up 850 mb temperatures and subsequently surface daytime temperatures. Each day, locations will warm a few degrees with highs topping out in the 90s for many lower elevations by Wednesday. The lowest elevations in the Columbia Basin will be approaching the century mark which may cause issues for individuals sensitive to heat. Other than that, clear skies and light winds will prevail as there will be little in terms of synoptic forcing. Wilson Wednesday night and Thursday: There is good agreement amongst the models that a strong cold front will pass through the region Thursday. The main concern with this front will be windy conditions and potential for rapid fire spread. A secondary concern will be potential for high based showers and isolated thunderstorms Thursday morning ahead of the front then showers and storms in the afternoon. Winds: This will be one of the strongest cold fronts we have seen this summer. The combination of a 13mb cross-CWA pressure gradient and cold advection will support winds in the lee of the Cascades and across the Columbia Basin on the order of 15 to 25 mph sustained with potential for some areas to be close to 30 mph. Accompanying gusts of 30-45 mph will be possible, especially within the Wenatchee River Valley and Waterville Plateau. In our non-windy locations such as the mountain valleys, gusts will be more infrequent but still on the order of 15-25 mph. Humidity levels will not be extremely low but should dip into the 20-25% range so any new fire starts could grow rapidly. Temperatures on Thursday will be cooling back into the 80s. Showers and Thunderstorms: There has been an upward trend with the potential for high based showers Thursday morning ahead of the cold front on the NAM/GFS/EC. My confidence is low for lightning strikes but something we will be watching closely in the coming days. This morning activity will be associated with high cloud bases near 10K feet so I would not expect much in the way of precipitation outside a few spotty hundredths. This activity is expected to track south to north across the the Eastern third of WA and possibly across the border into North Idaho Thursday morning. In the afternoon, a stronger wave will swing into the region with a slight negative tilt. As a result, additional showers and thunderstorms will be possible across the Northern mountains and possibly some areas of the Okanogan and Methow Valleys. These will have the potential to be a bit more intense with gusty winds, small hail, and brief downpours. Lightning strikes will also be a concern for potential new fire starts. Thursday night through Monday: Much cooler weather is expected for Friday into the start of the weekend as we hold on to a baggy trough over the Northwestern US. Many ensemble suites support afternoon highs in the 70s to lower 80s during this time and this is now reflected in the latest National Blend of Models. High temperatures on Friday will be roughly 10 degrees below average. Overnight lows will provide natural air conditioning with readings expected to dip into the 40s to 50s. Dry air moving into the region Thursday night will promote dry conditions for Friday then a small threat for showers will return to the northern mountains for Saturday. There is a lot of spread in the models for Saturday night through Monday with the evolution of the upper-levels. Some models hang on to deeper troughing over the region and cooler, showery weather; otherwise start to build in flat ridging suggesting a subtle warming and drying trend. Forecast leans toward the latter of these solutions but would not rule out some changes as we continue to iron this out. Big picture would suggest no big warm-ups, potentially locally breezy winds, and high uncertainty with any precipitation chances. /sb && .AVIATION... 06Z TAFS: VFR conditions expected for the TAF sites through the period. Southwest winds will be breezy with occasional gusts into the mid teens through the afternoon for GEG-SFF-COE-PUW-LWS before decreasing by early evening. Late afternoon/evening gustiness is again likely at EAT. /JDC && .PRELIMINARY POINT TEMPS/POPS... Spokane 87 56 89 57 94 60 / 0 0 0 0 0 20 Coeur d`Alene 84 55 87 56 91 60 / 0 0 0 0 0 10 Pullman 82 52 86 53 91 57 / 0 0 0 0 0 20 Lewiston 89 62 92 62 97 67 / 0 0 0 0 0 10 Colville 89 51 91 52 94 55 / 0 0 0 0 0 10 Sandpoint 83 54 86 54 89 57 / 0 0 0 0 0 0 Kellogg 80 59 84 59 89 63 / 0 0 0 0 0 0 Moses Lake 91 56 92 58 97 61 / 0 0 0 0 0 10 Wenatchee 88 62 92 66 96 65 / 0 0 0 0 0 10 Omak 89 60 93 63 96 63 / 0 0 0 0 0 10 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...None. WA...None. && $$

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