Marine Weather and Tide Forecast for Lewiston, ID

SYNOPSIS
Isolated thunderstorm will taper off through the evening.
Overnight lows will be cold with near to below freezing temperatures. Warmer and drier conditions return Friday into Saturday. Next round of showers expected for the start of next week.

DISCUSSION
Tonight through Thursday: The region is on the backside of an exiting cold front. Drier air is moving into the region dropping precipitable water values to under a quarter of an inch or 50-60 percent of normal. The earlier afternoon, evening convection will decrease as the atmosphere stabilizes due to ridge pattern building in the region. Ensembles have shower activity continuing over the Northeast WA and North ID through Thursday. It is due to wrap around moisture from the exiting Low. Rain and rain/snow mix are possible with up to 30 percent chance of half an inch of snow. Impacts will be minimal as surface temperatures will limit to no accumulations. Winds will weaken overnight before increasing on Thursday. Wind gusts will be in the teens overnight and 20-30 mph Thursday afternoon. The lows will drop into the upper 20s and 30s into Thursday morning. Portions of the Columbia Basin have reached early growing season. Cold sensitive vegetation could be impacted. If winds remain breezy, it will lower the potential for frost/freeze impacts. Thursday highs will be in the upper 40s to low 60s.

Friday and Saturday: Ridging pattern will bring a dry, warming trend for the period. Highs will climb back into the 60s and low 70s. Any precip chances are limited to the higher terrain of the Idaho Panhandle along the Montana Border. Amounts are less than a hundredth of an inch. Morning temps will still be in the 30s.

Sunday through Wednesday: Weather pattern will change as a Gulf of Alaska Low is expected to move into the region. It is still tracking to move south along the Pacific Coast and into Northern California. The track keeps the regions warm, dry trend through Monday. Shower chances increase Tuesday into Wednesday as the Lows moisture finally moves into the Inland Northwest. A few ensemble members have the track moving the Low into Oregon and bringing the showers earlier. Highs will be in the upper 60s and 70s. Lows will be in the upper 30s and 40s. /JDC

AVIATION
18Z TAFS: Region is the on the backside of the exiting front.
Trailing showers and MVFR conditions are currently impacting KGEG- KSFF- KCOE- KPUW- KLWS. Drier air is filtering into the region bringing VFR conditions to KEAT-KMWH. Additional showers will develop from high based clouds in the afternoon falling as mix of rain/snow but little to no probabilities for conditions to lower below VFR. The main issue in the post frontal air mass will be gusty winds of 20-30kts. Overnight stratus will develop over Eastern WA and North ID possibly bringing another round of MVFR ceilings and increased precip chances for Thursday morning.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: There is low confidence for the post frontal rain/snow showers this afternoon given the higher cloud bases and dry air intrusion.
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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 29 51 30 54 32 61 / 20 30 0 0 0 0 Coeur d'Alene 29 47 29 52 30 59 / 30 50 10 0 0 0 Pullman 28 45 29 51 32 59 / 30 40 10 0 0 0 Lewiston 33 50 34 56 33 64 / 30 30 0 0 0 0 Colville 27 53 26 57 28 62 / 50 30 0 0 0 0 Sandpoint 29 45 28 50 29 57 / 60 70 20 20 0 0 Kellogg 27 41 28 47 29 56 / 50 80 30 30 0 0 Moses Lake 28 58 31 61 34 67 / 0 0 0 0 0 0 Wenatchee 32 55 35 59 40 63 / 10 0 0 0 0 0 Omak 31 58 32 61 35 64 / 10 0 0 0 0 0

OTX WATCHES/WARNINGS/ADVISORIES
WA...Freeze Warning from 2 AM to 8 AM PDT Thursday for Moses Lake Area-Upper Columbia Basin-Wenatchee Area.
ID...Winter Weather Advisory until 5 AM PDT Thursday for Central Panhandle Mountains.