Area Forecast Discussion
Issued by NWS Pendleton, OR
Issued by NWS Pendleton, OR
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960 FXUS66 KPDT 131730 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 1030 AM PDT Mon May 13 2024 .AVIATION...18z TAFs...Widespread VFR with dry conditions through the TAF period. Gusty winds will be present through the afternoon and remain the forecast challenge. Guidance indicates a high chance (70-100%) for gusts of at least 22 kts for today across most terminals. The focus for the strongest wind lies between KDLS and KYKM where a high chance (75-95%) for gusts of 34 kts today. Winds are anticipated to lessen through the later portion of the forecast period, especially after around 10z Tuesday. Branham/76 && .PREV DISCUSSION... /issued 935 AM PDT Mon May 13 2024/ UPDATE...Current radar and visible satellite imagery showing dry conditions as some high level clouds stream in from the northwest, pushing into the Yakima Valley. This is in response to an upper level shortwave that is passing across the area later this morning and through the afternoon, elevating winds and slightly increasing cloud cover. A pressure gradient is expected to develop along the Cascades, increasing winds through the Kittitas Valley, Simcoe Highlands, Eastern Gorge, and the northern Blue Mountain foothills. The GFS and the NAM both suggest a pressure gradient between Portland and Spokane of 10-11 mb, peaking between 2 PM and 11 PM this afternoon/evening. Thus, a Wind Advisory has been issued through 11 PM Monday night for the Kittitas Valley as gusts of up to 50 mph will be possible. Confidence is high (70-80%) of advisory-level winds occurring across the Kittitas Valley as the NBM highlights an 86% chance of wind gusts of 47 mph or greater, and a 52% chance of wind gusts of 55 mph or greater for Ellensburg. The other weather concern resides with elevated river levels on the Naches River as the station near Cliffdell is forecast to reach action stage later this morning. The current river level is 28.85 feet and is forecast to reach action stage (29 feet) by 11 AM before slowly peaking Friday morning at 29.46 feet. At this time, there is high confidence (>95%) of reaching action stage and a low chance (<5%) of reaching minor flood stage (31 feet). The Naches River near Naches is also currently forecast to reach action stage (16 feet) Thursday morning before peaking at 16.14 feet early Friday morning. However, confidence in reaching action stage is moderate (46%), with a low chance (<5%) of reaching minor flood stage. 75 PREV DISCUSSION... /issued 230 AM PDT Mon May 13 2024/ SHORT TERM...Today through Wednesday...An upper level shortwave trough will pass over the region today producing breezy to windy conditions but very little if any precipitation. Sustained winds of 15 to 30 mph with gusts around 40 mph will be common throughout the lower elevations. The Kittitas Valley is expected to see a little stronger winds with gusts 45 to 50 mph so a wind advisory is in effect through this evening. The winds will usher in some cooler air with high temperatures running 5 to 15 degrees cooler today compared to Sunday. The trough will exit to the east overnight with a ridge of high pressure in its wake building over the eastern Pacific Ocean. This will keep the forecast area under a dry northwest flow Tuesday through Wednesday with lighter winds. Temperatures will remain steady to slightly warmer on Tuesday and then rise another 5 degrees or so on Wednesday. LONG TERM...Thursday through Monday...Not much of a change to the forecast through the long term. Temperatures remain steady with dry conditions continuing through the lower elevations. There continues to be below 15% probabilities of rain along the far northern Cascades and increasing to 22-36% probabilities Sunday into Monday. Models are in firm agreement with the upper level high shifting slightly southwest away from shore and broadening the upper level flow as an upper level shortwave moves down the coast of B.C.. Clusters shows there is a timing and positioning variance between the models however. Both Thursday and Friday have signaled an increase in the cross Cascade pressure gradient which will increase the chances of westerly flow and windy conditions beginning in the Kittitas Valley and progressing southward through the day. Latest raw ensembles shows there is 20-30% chance of the Gorge and lower Columbia Basin seeing sustained winds of 25 mph, 40-60% along the Simcoe Highlands and through Kittitas Valley. These chances increase to 30-40% through the Gorge and lower Columbia Basin and Kittitas Valley and 40-60% along the Simcoe Highlands. Confidence in the winds in moderate with the timing being the largest variance. EFI is showing a slight increase in above normal temperatures mainly through the Basin with the NBM putting temperatures in the upper 80s. Over 70% of the raw ensembles put the entirety of the Columbia Basin, Gorge, foothills of the Blues and John-Day Basin above 80 degrees dropping to the upper 70s to low 80s by Friday. The shortwave passage also brings a less than 15% probability of rain to the higher elevations of the far northern Cascades near Snoqualmie Pass. Saturday and Sunday confidence between the models lessens a bit more with the timing and the strength of the upper level low. EURO shows the shortwave to broaden bringing increased chances of rain while the GFS tightens into an upper level low with precipitation locked against the Cascades. Models also show a surface embedded cold front ahead of the upper level system which will bring a decrease in the temperatures Saturday. EFI shows the temperatures Saturday and Sunday to moderate to near normal with 70-80% of the raw ensembles showing the aforementioned areas dropping nearly 10 degrees Saturday steadily increasing Sunday. Guidance shows the winds to shift to a more northwesterly component allowing diurnally breezy conditions with 70% probabilities for the more wind prone regions to see near 20 mph winds. Lastly, models fall out of phase by Monday with the Euro bringing in a brief transient ridge ahead of another upper level low while the GFS keeps the original low overhead and deepening across the region. With that, let the NBM take the reins which has 22-36% probabilities of rain along the northern Cascades , light westerly winds and temperatures in the upper 70s for the lower elevations. Bennese/90 AVIATION...12Z TAFs...VFR conditions through the forecast period. Li and there will be more cumulus with similar bases on Monday. Lingering high level cirrus around 18+ kft will fluctuate across eastern WA and northeast OR during the day. It has been breezy for DLS overnight while under 10kts elsewhere. However, westerly winds of 10-15 kt gusting to 20-35kt will ramp up across the remaining TAF sites between 17Z & 21Z. Bennese/90 && .PRELIMINARY POINT TEMPS/POPS... PDT 76 46 74 49 / 0 0 0 0 ALW 79 50 76 53 / 0 0 0 0 PSC 83 53 81 54 / 0 10 0 0 YKM 79 46 81 49 / 0 0 0 0 HRI 81 50 80 51 / 0 0 0 0 ELN 71 47 76 51 / 0 0 0 0 RDM 73 41 73 44 / 0 0 0 0 LGD 73 44 72 45 / 0 0 0 0 GCD 74 42 73 44 / 0 0 0 0 DLS 75 50 81 54 / 0 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...Wind Advisory until 11 PM PDT this evening for WAZ026. && $$ SHORT TERM...91 LONG TERM....90 AVIATION...76