Marine Weather and Tide Forecast for Heron, MT

SYNOPSIS
Isolated thunderstorms will bring a threat for small hail and gusty winds across north central Washington through the evening.
Breezy and dry conditions will be in place through Friday with a subtle decrease in wind speeds Friday afternoon. Lighter winds and mild temperatures for the upcoming weekend. Warmer next week with an increasing risk for elevated fire weather conditions from gusty winds.

DISCUSSION
Tonight - Friday: There are two main weather impacts for the rest of today and tomorrow. Breezy winds leading to elevated fire weather conditions and isolated thunderstorms. The region is undergoing a pattern change from our hot upper-level ridge to a cooler trough though the parent trough will never truly come onshore and more or less sling a few shortwaves through. This will allow the marine layer to deepen over coastal OR/WA while moderated warmth remains over the Inland NW. The pressure gradient between these two air masses will result in breezy to locally gusty conditions this evening and again on Friday. For this evening, humidities will remain dry enough such that new fire starts in the dry grasses could become problematic. The winds will remain elevated overnight keeping the low level air mass mixed and temperatures warmer than Thursday morning, especially from Wenatchee to Palouse. On Friday, the winds will continue to blow but speeds will be decreasing relative to Thursday as the air mass cools some and high temperatures cool another 5 degrees reducing the thermal gradient across the Cascades. Needless to say, gusts of 20-25 mph will be common across the open wheat country. Humidity levels will be roughly 5% higher but still dry enough such that dry grasses will be vulnerable to fire spread, but conditions will not be strong enough to warrant any fire weather highlights.

As for showers and thunderstorms. We are getting surface based convection this afternoon over the mountains along the Canadian border and just south of the Camas Prairie. Thinking cells will continue to develop over the northern mountains through this evening and potentially expand southward into the North Cascades and Okanogan Highlands as far south as Hwy 20 as a shortwave currently crossing into the Olympics works eastward. A few cells could be strong with small hail, heavy downpours, and wind gusts to 35 mph. This will be monitored closely between Conconully, Omak, Oroville, and Republic. Around midnight, cam models are in good agreement of a band of elevated showers developing in NE Oregon and tracking through SE WA and the Idaho Panhandle. Not seeing a lot of elevated instability with this feature for lightning but wouldn't give it a zero chance.
Probabilities for lightning are closer to 10% or less at this time. This activity should be lifting into Montana by the Friday morning commute. On Friday afternoon, surface based convection will once again develop over the northern mountains and along a ribbon of instability stretch from NE OR to Mullan, ID. There are lower probabilities for CAPES supportive of lightning and forecast mainly comes with a 15% chance for lightning strikes over far NE WA near the international border.

Saturday-Sunday: The region will remain under southwest flow aloft sandwiched between a coastal trough and high pressure over the Central Rockies. Smaller ripples of energy have the potential to come through sparking a few light showers at times but generally low threat for thunderstorms or impactful weather as there looks to be a decent amount of midlevel drying.
Temperatures will warm 1-3 degrees each day each Saturday and Sunday reaching the 70s to 80s, still 5+ degrees above 30 year averages for this time of year. Winds will be lighter with more typical afternoon breezes of 15-20 mph. Nights will be cool with sheltered northern valleys dipping into the 40s and lower 50s in the Basin.

Monday-Thursday: A mini warm-up will arrive Monday and Tuesday as another low digs into the Gulf of AK and higher heights buckle northward. Temperatures will poke back into the 80s to lower 90s with 90s more common in the lower Basin and Snake River Valley.
There will not be much in the way of warming west of the Cascades which implies another period of winds will be on the horizon and likelihood for elevated fire weather conditions. As timing stands now, the winds will start off through the Cascade Gaps starting Monday afternoon and evening then fan out across the remainder of E WA and N ID Tuesday as the heat breaks down.
There is a 30% chance for wind gusts of 30 mph or stronger on the Waterville Plateau, Wenatchee Area, and into the foothills of the Blue Mountains Monday evening which increases to 40-50% by Tuesday afternoon. Wind gusts 20-30 mph look to be more common for the remainder of the Palouse, Basin, and foothills on the northern rim of the Basin as well as the Okanogan Valley.
Tuesday's winds will also be ushered by a stronger jet and cold front vs just a thermal gradient and would anticipate the forecast winds to increase further as confidence increases over the next few days. Outside some mountain shower and few thunderstorms, the precipitation outlook through Wednesday looks meager with the setup very similar to today and most convection on the outskirts of my forecast area. By Thursday into Friday, a deep low will reside in the vicinity of the Northwest. Some models have the feature drift into the PacNW, others keep it offshore. The positioning of this feature will be key to where bands of precipitation setup and how cool/warm temperatures trend. The NBM currently has 20-40% chance for wetting rains from N Idaho into Northern WA and over the Cascades for the 48 hour period ending Sunday morning. The lower Basin and Wenatchee Area only come with a 10% chance or less for a region that can really use some moisture. /sb

AVIATION
06Z TAFS: Light showers will develop ahead of a shortwave disturbance across southeast Washington into the southern to central Idaho Panhandle between 12-18Z. Showers will be high based with ceilings above 8 kft agl. and will contain weak convective updrafts. Showers passing by KPUW and KLWS may just be in the form of virga or as brief light rain. Showers will clear the region by the late morning. Smoke from fires burning in northern Oregon may result in hazy skies particularly around KPUW and KLWS and generally south of the Spokane-Coeur d'Alene corridor (KGEG-KSFF-KCOE). Visibility may decrease slightly but remain above 6SM with VFR conditions prevailing.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: High confidence for VFR conditions. /SVH

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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 54 77 48 78 52 80 / 0 10 0 0 0 10 Coeur d'Alene 53 77 48 78 51 79 / 10 20 10 0 0 10 Pullman 50 73 44 74 49 77 / 0 20 10 0 0 10 Lewiston 56 82 54 84 57 84 / 10 20 10 0 0 10 Colville 52 76 42 78 44 80 / 20 20 20 20 0 10 Sandpoint 54 76 48 77 47 79 / 10 10 10 10 0 10 Kellogg 54 73 52 75 55 78 / 0 20 20 0 0 10 Moses Lake 56 82 48 82 52 86 / 0 0 0 0 0 0 Wenatchee 57 79 52 82 56 85 / 0 0 0 0 0 0 Omak 52 79 49 82 52 84 / 20 10 10 10 0 10

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