Sunrise 5:42 AM   Sunset 8:13 PM Moonrise 1:39 AM   Moonset 9:36 AM

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FXUS66 KOTX 301118 AFDOTX

Area Forecast Discussion National Weather Service Spokane WA 418 AM PDT Tue Apr 30 2024

SYNOPSIS
Scattered showers will continue through the week, along with a warming trend through the weekend. Conditions will remain unsettled with a weather system moving in from the west Thursday, and another one over the weekend into next Monday.

DISCUSSION

Today through Wednesday Night...For today, another shortwave is expected to traverse the region, bringing back showers and possibly graupel by the afternoon. There's also a slight chance of thunderstorms in southeast and northeast WA during the later part of the day, accompanied by moderately breezy winds but not near what the region has seen the last couple days. After sunset, the threat of showers diminishes. Expect highs hovering around 50 today, with lows dropping into the 30s yet again tonight. Those with sensitive plants should take precaution.

By Wednesday, the trough will move eastward, resulting in slightly warmer temperatures but still remaining around 5 degrees cooler than normal. Temperatures will warm into the upper 50s to mid 60s. Showers will also return but will mainly impact the Idaho Panhandle and far northeastern WA. With the increase in temperatures, precipitation is expected to fall as rain rather than a rain/graupel mix. Lows Wednesday will be slightly warmer than tonight, but still remain in the mid to upper 30s. /KM

Thursday to Monday: The Inland NW remains in an active pattern, with periodic chances of precipitation and a warming trend into at least Saturday. Model agreement toward the weekend continues to be much less than ideal to have high confidence in the forecast by then. Ensembles are at least in slightly better agreement than the deterministic.

First on Thursday another shortwave drops into the region, but its track takes its center over the southwest half of WA into Oregon, then into the southern half of ID. This will hold the primary precipitation potential over the Cascades and southern third of WA and the lower ID Panhandle in the morning. Then the afternoon comes with steepening lapse rates and little bit of instability, increasing the threat of showers over a larger portion of the CWA The higher potential will remain the mountain zones and southeast WA/lower ID. While not in great abundance, there is some convective instability and some isolated t-storms are possible primarily closer to the mountains in the afternoon too. The showers wane going into Thursday night with the loss of daytime heating.

By Friday a weak ridge builds in. Some instability and orographic lift will keep shower chances alive around northeast WA and ID mountains in the afternoon, with a slight chance of t-storms.
Otherwise look for more sun.

Heading into the weekend: through Friday, low pressure (that is now just coming into the Aleutians) approaches the Pacific coast.
How far south it tracks before moving onshore is where models continue to disagree. Yesterday more solutions were holding the low further south, with the EC the primary model that brought it into our region. Today the EC track is slightly further south and the other solutions are slightly further north. About 60% of the ensembles track the low inland over Oregon and the other 40% take it toward northern or central CA. While there is still some chance of a drier weekend, the forecast leans on the ensembles with favor toward the Oregon track with slightly higher than average confidence in precipitation in the region this weekend. Snow levels average at 5500 feet or higher, so mainly rain and higher mountain snow are in the forecast. There is a little bit of instability so a slight risk for t-storms will be in the forecast for Sunday afternoon. Winds will a bit breezy with increased mixing with the system, but with gusts near 15-20 mph mostly.

Going into Monday another low drops in and helps to carve out a broader trough over the West, including our region. This will mean overall higher confidence in precipitation. The higher risk will be away from the lee of the Cascades and deeper Columbia Basin and there could be some t-storms mixed in the afternoon, but nothing too strong. Snow levels drop to around 4500-5500 feet by this time, lowest near the Cascades. Thus some light snow may come back toward places like Stevens Pass, but it is too early to have confidence in precise amounts other than to say it is marginal for snow and so the impacts may be limited. Winds still look marginally breezy with gusts near 15-20 mph.

Temperatures will be trending warmer through at least Saturday, then start to trend downward by at latest Monday. There remains a modest spread in solutions in precise numbers by the transition day, Sunday, when models show highs could be anywhere from near 50 to the lower 70s. Overall look for near to slightly above normal temperatures into Saturday, then temperatures close to or slightly below normal by Monday. Morning lows still remain in the 30s to near 40 on Thursday and Friday, meaning potential frost lingering in some spots. /Solveig

AVIATION
12Z TAFS: MVFR stratus will increase through 15Z with the light upslope winds in Eastern WA and ID Panhandle. Another round of showers will develop this afternoon but less in coverage compared to yesterday. Isolated thunderstorms may also develop, but the main threat will be over the higher terrain of SE Washington, and up over NE Washington.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: There is high confidence in continued VFR conditions in Central Washington. There is a 20% chance of thunderstorms. Confidence is any of the TAF sites being impacted is too low to include in the TAF forecast.

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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 51 35 58 36 62 37 / 20 20 20 10 20 10 Coeur d'Alene 47 34 54 36 60 37 / 40 20 30 20 20 10 Pullman 46 31 53 34 59 36 / 50 30 30 20 30 10 Lewiston 54 37 60 38 65 42 / 50 30 20 20 30 10 Colville 52 29 60 33 64 34 / 30 20 20 10 30 10 Sandpoint 46 34 51 36 58 37 / 40 30 60 20 40 20 Kellogg 43 34 48 36 56 37 / 70 40 70 30 40 20 Moses Lake 56 34 65 35 67 39 / 10 0 0 10 20 0 Wenatchee 54 39 62 40 65 44 / 20 10 0 10 10 0 Omak 56 35 65 39 67 41 / 20 20 0 10 20 10

OTX WATCHES/WARNINGS/ADVISORIES
ID...None.
WA...None.

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