Area Forecast Discussion
Issued by NWS Spokane, WA
Issued by NWS Spokane, WA
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
103 FXUS66 KOTX 120947 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 247 AM PDT Sun May 12 2024 .SYNOPSIS... Today will once again be warm, with highs reaching the 80s and a few areas in the lower 90s. An approaching system will increase the breeziness this afternoon and Monday, especially closer to the Cascades and western Columbia Basin. A chance for showers will come to the Cascade crest, northeast Washington and the northern Idaho Monday, lingering over Idaho Tuesday. Temperatures will cool for Monday and Tuesday, rebound around midweek, then decrease again later in the week as the next shower and breezy winds chances come in. && .DISCUSSION... Today through Tuesday: The Inland NW will experience once more warm day, before a system moves in and cools thing at little bit, with localized shower chances and gusty winds. Today the axis of the ridge of high pressure will shift east, while the first shortwave moves in from the west. The ridge will continue to provide mostly dry conditions and temperatures reaching the upper 70s and 80s, along with a few areas approaching 90 in the deeper Columbia Basin. The approaching shortwave will enhance the onshore flow, leading to slightly cooler readings in the Cascades and some afternoon breeziness. Then tonight into Monday morning the first shortwave moves through the region, followed by a second shortwave trough on its heels Monday afternoon and evening. The first wave will lead to more clouds and very limited shower chances near the immediate Cascade crest and Canadian border. Winds will also increase more noticeably near the Cascades into the Waterville Plateau early this evening, with speeds near 15-25 mph, with gusts near 30-40 mph. Areas just downwind of the Blue Mountains will see some winds near 15 mph and gusts of 20-30 mph. Speeds abate a little overnight into early Monday. The second wave moving in will keep shower chances alive near the Cascade crest through afternoon and bring broader shower chances across northeast WA and the north and central ID Panhandle, including skimming by the northeast Spokane county area into the CdA area. As that wave sags through in Monday evening it will draw more clouds south and east and, per some guidance, expand shower chances over more of the Spokane/CdA area and possibly as far south as far northern Whitman county. No all guidance is in agree with this precipitation scenario but the risk seems enough to warrant at least a slight chance in these ares. Either way precipitation amounts mostly look light. The exception could be in the northeast WA mountains and north ID where some embedded t-storms are possible Monday afternoon and evening. Winds will pick up across the region Monday afternoon and evening. The strongest speeds will continue near the Cascades and Waterville Plateau at 15-30 mph and gusts of 35-40 mph. Elsewhere speeds of 10-20 mph and gusts 15-25 mph will be possible, especially unsheltered areas. Heading into Monday overnight into Tuesday the shortwave moves east, leaving the area in a northeast flow and shifting the primary shower chances to the northern and central ID Panhandle. Winds remain breezy overnight with some decline toward day break, before the pick up again in the afternoon over some the area. The breezier conditions by Tuesday afternoon will be down the Okanogan Valley into the Waterville Plateau, with winds changing from westerly to more northerly with speeds of 10-20 mph and gusts of 25-30 mph. Temperatures will be cooling to the upper 60s and 70s, with a few low 80s in the deeper Columbia Basin and L-C Valley for Monday and Tuesday, with overnight lows in the 40s to low 50s. /Solveig Tuesday night through Saturday: Models are in good agreement for the upper level ridge to at least temporary rebound over the Inland Northwest on Wednesday. This will allow temperatures will warm back into the upper 70s to mid 80s by Wednesday afternoon. By Thursday, there still exists a lot of uncertainty in the evolution of the ridge. While models do agree on the initial rebound of the ridge on Wednesday, there are many opposing solutions on the impact an upper level trough will have on it as it passes through British Columbia on Thursday. 55% of ensembles out of a 100 ensemble suite show a deeper trough to move into the northwest. However, among these ensembles, there are varying possibilities on the overall strength of this trough. In general, this would deflect the ridge to our south, bringing temperatures down into the 50s and 60s on Thursday, breezy winds, and chances for precipitation. A weaker trough would be a slightly "warmer" solution, with breezier winds and less precipitation. A faster moving, stronger trough solution would result in much cooler temperatures, better chances for widespread preciptiation, and an earlier onset of breezy winds. Meanwhile, the other 45% of ensembles show a ridge remaining in place, with less of an influence from the trough as it passes to our north. Again, among these ensembles, there are varying degrees on the strength of this ridge. A stronger ridge would would keep temperatures in the 70s and 80s with clear skies and dry weather. However, a weaker ridge would still allow there to be some influence from the trough to our north, with these solutions showing breezy winds and slightly "cooler" temperatures compared to the strong ridge. Because of this, the forecast for Thursday and beyond will change several times over the next couple of days as models begin to trend toward a consensus. Uncertainty in the forecast continues Friday through the weekend with the potential for additional systems to pass through the Inland Northwest. Models show a gradual decline in temperatures through the weekend continuing into early next week, but the exact numbers carry very low confidence at this time. /vmt && .AVIATION... 12Z TAFS: High pressure starts to weaken and a shortwave system starts to move int tonight. However VFR conditions expected at TAF sites. A few more clouds are possible over the northern mountains, with some fair cumulus build-ups in the afternoon, with isolated shower chances near the Canadian border for this evening and overnight. Winds increase this afternoon with gusts near 15-20 mph in the 1300-1900 PDT time frame for most place. The exception will be near the Cascade, including EAT where winds will remain breezy through the night with gusts near 20-30kts possible. There will be risk for LLWS as a low level jet strengthens in advance of the shortwave, with the potential near PUW, MWH and, if the mixing decouples, near EAT. FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: There is high confidence in VFR conditions. Low confidence in showers and precise timing of winds near the Cascades and EAT, as well as low to moderate confidence in LLWS overnight/early Monday near PUW, MWH and EAT. ----------------------- 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 82 51 75 47 75 49 / 0 0 10 20 10 0 Coeur d`Alene 80 51 73 47 71 47 / 0 0 20 20 10 0 Pullman 77 51 70 46 69 47 / 0 0 0 10 10 0 Lewiston 85 54 79 52 77 52 / 0 0 0 10 10 0 Colville 83 48 76 45 77 45 / 0 10 20 20 10 0 Sandpoint 78 50 70 48 69 46 / 0 0 30 30 20 0 Kellogg 76 53 68 49 68 49 / 0 0 20 20 20 0 Moses Lake 88 53 79 48 80 51 / 0 0 0 0 0 0 Wenatchee 86 56 74 50 80 54 / 0 0 0 0 0 0 Omak 89 53 79 48 81 51 / 0 0 10 10 0 0 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...None. WA...None. && $$