textproduct: Spokane

KEY MESSAGES

- Isolated thunderstorms in far North Idaho Wednesday afternoon and evening.

- Gusty winds Wednesday afternoon and evening in Central Washington.

- Minor to locally moderate HeatRisk through Thursday. This level of heat primarily affects those who are sensitive to heat.

- Dangerously cold water temperatures pose a high risk for cold water shock and hypothermia for anyone who unexpectedly falls in. Wear a life jacket if recreating on or near the water.

SYNOPSIS

A prolonged period of above normal temperatures will continue into the middle of May. Conditions will be dry outside small chances for mountain showers and thunderstorms in the North Idaho Panhandle Wednesday. Winds will be gusty Wednesday and Friday, especially in Central Washington.

DISCUSSION

Wednesday through Tuesday: The message for the next week is to be prepared for above normal temperatures and generally dry conditions. An upper-level ridge will be dominant over the Northwest through the next seven days. Weak shortwaves will ripple over the the top of the ridge at times, each dragging a mostly dry cold front through. Each front will increase onshore flow, pile marine clouds west of the Cascade Crest and result in breezy to locally windy conditions. The two main cold fronts will be Wednesday and Friday. Each of these days will have winds peak in the late afternoon and early evening resulting in elevated fire weather conditions. As for precipitation, there isn't much to discuss. The main precipitation threat will come with Wednesday's cold front with a chance for showers and thunderstorms focused over far North Idaho; all other days are expected to be dry at this time.

Wednesday Showers and thunderstorms: HREF mean CAPE for North Idaho and areas of Eastern WA vary from 200-450 J/kg. Closer examination of soundings suggest a stable layer will prevent convection from developing over much of Eastern WA and the lower Idaho Panhandle. The target area for a few cells will be extreme NE WA and far North Idaho largely north of a line from Sandpoint to Colville. Percentages for showers or storms in NE WA are 10-15% and increase 15-30% around Bonners Ferry, Porthill, and Moyie Springs. The strength of the showers and outlook for lightning will depend on how quickly a surge of higher dewpoint air can punch northward into this area, originating from the Columbia Gorge . If dewpoints can increase into the mid to upper 40s prior to sunset, then there could be a few cells capable of a 0.25"or more rainfall and few storms that may need to be closely monitored. Any storms that do develop will pose a threat for downpours of rain and small hail, wind gusts of 30-35 mph, and lightning. If you have outdoor plans in North Idaho Wednesday between 4-7PM, keep an eye to the sky.

Wednesday and Friday Winds: As mentioned above, there will be two main bouts of gusty winds. For each Wednesday and Friday, the strongest winds will impact the East Slopes and Western Columbia Basin. There is a 20-40% chance for wind gusts 30 mph or stronger Wednesday which then increases to 30-60% for Friday. The peak of the winds both days will be late afternoon and early evening. Locations like Vantage, Waterville, Entiat, and Ephrata will carry the highest probabilities (10-20%) for brief wind gusts of 40 mph. Wind gusts in the eastern Columbia Basin, Palouse, and Spokane Area will be in the 20-30 mph range with locally stronger speeds in the foothills of the Blue Mountains around Pomeroy and Hwy 12.

With the mild temperatures in place through the week (70-80s), minor heatrisk will be present which primarily effects those who are extremely sensitive to heat and not acclimated to the warmer temperatures this early in the season. Folks heading to rivers and lakes should be cautious that water temperatures remain cold with elevated risks for hypothermia without proper gear. /sb

AVIATION

06Z TAFS: VFR conditions will prevail under mostly clear skies through the forecast period. Mid and high clouds will increase in the afternoon Wednesday with the arrival of a cold front. Isolated to scattered convection will impact far north Idaho around Bonners Ferry, ID with a 15% chance to expand as far south as Sandpoint, ID and 10% chance to develop over extreme Northeastern WA around Ione, WA. Lightning, downpours, and gusty winds will be possible with this activity between 22-03z. Winds will become gusty after 20z over the Palouse, Spokane Area, Columbia Basin, and East Slopes of the Cascades. Wind gusts will remain below 30 mph for Spokane, Pullman, and Lewiston and 30-35 mph around Waterville, Wenatchee, Ephrata, Moses Lake, and Chelan airports between 23-05z.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: Moderate to high confidence for convection to remain in far North Idaho, lower confidence for cells to develop in extreme NE WA. Otherwise, VFR conditions prevail. There is a 20-40% chance for wind gusts to exceed 30 mph at Chelan, Wenatchee, Ephrata, and Moses Lake.

----------------------- 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 80 52 78 52 74 47 / 0 0 0 0 0 0 Coeur d'Alene 77 50 74 50 70 46 / 0 10 0 0 0 0 Pullman 75 51 71 46 69 44 / 0 0 0 0 0 0 Lewiston 81 54 76 49 76 48 / 0 0 0 0 0 0 Colville 82 48 83 50 77 45 / 0 0 0 0 0 0 Sandpoint 75 48 74 48 69 45 / 0 10 0 0 0 0 Kellogg 76 48 72 47 70 44 / 0 10 0 0 0 0 Moses Lake 86 52 81 51 79 46 / 0 0 0 0 0 0 Wenatchee 85 55 82 55 76 50 / 0 0 0 0 0 0 Omak 88 52 85 55 81 47 / 0 0 0 0 0 0

OTX WATCHES/WARNINGS/ADVISORIES

WA...None. ID...None.