####018008284#### FXUS65 KSLC 032201 AFDSLC Area Forecast Discussion National Weather Service Salt Lake City UT 401 PM MDT Fri May 3 2024 .SYNOPSIS...An approaching storm system will bring much warmer conditions Saturday with strong afternoon winds for portions of Utah. A cold front will track into Utah Sunday. Lighter winds, cooler conditions, valley rain, and mountain snow are likely once the front pushes through. && .SHORT TERM (Through 12z/6AM Monday)...Satellite imagery shows a shortwave ridge continuing to shift eastward through the Great Basin and into Utah. Thus, skies will continue to clear heading into the late evening and overnight hours. Also seen is a strong closed low off the coast of British Columbia that will eventually produce winter-like conditions across much of our area later in the weekend. The shortwave ridge axis will pass quickly to our east by mid Saturday morning, with increasing southerly flow as the aforementioned closed low pushes inland. In this pre-frontal environment, strong warm-air advection will produce Saturday high temperatures that are 10-20 degrees above Friday highs across all but far southern Utah. The main concern for Saturday, however, is gusty southerly winds across western valleys picking up in the afternoon and peaking overnight. Many western valleys will reach high-end Wind Advisory criteria (45-58 mph), with the highest gusts likely across western Juab and Millard counties, reaching upwards of 60 mph (70% chance in most areas). H7 winds around 50kts will likely mix well to the surface given steep lapse rates and a dry air mass, however increasing mid-level clouds could act to limit this mixing...therefore there is still some uncertainty in peak gusts at this time. This main core of winds will shift eastward by Sunday, with winds picking up Sunday morning across southeastern valleys, peaking Sunday afternoon. A High Wind Watch has been issued for these areas to highlight the highest risk areas. A potent cold front will bring quite the contrasting weather to the area on Sunday, with a stark transition to much cooler temperatures, plentiful valley rain, snow down to 5000 feet, and weaker northwesterly flow. This cold front will be quite strong, also featuring the potential for thunderstorms along and behind the front on Sunday. This front will likely enter northwest Utah Sunday morning, reaching the Wasatch Front by mid day and southern Utah by evening. Widespread precipitation will mainly begin along the frontal passage, with a few rogue showers possible just ahead of the front. Periods of heavy precipitation are possible, including heavy mountain snow. In terms of QPF through Monday, the Wasatch Front could see 0.8-1.4" of rain, with the northern mountains receiving upwards of 2" or more of liquid equivalent. These amounts could be even higher with any lake-enhancement late Sunday night. Snow levels, initially around 9000-9500 feet, will plummet with the frontal passage down to 5000 feet. The highest snow amounts up to 2 feet are expected in the Upper Cottonwoods and Ogden area mountains, given an extended period of unstable west to northwesterly flow and orographic enhancement behind the front. Thus, Winter Storm Warnings have been issued for the northern mountains, especially given the potential for surface transportation impacts and unseasonable nature of the system. In summary, expect strong warming and southerly winds ahead of the storm system late Saturday into Sunday, with an abrupt transition to winter-like conditions on Sunday. .LONG TERM (After 12Z/6AM Monday)...Northwest flow will be our dominant flow pattern early next week behind the passage of a low pressure system and strong cold front. A series of shortwave troughs are forecast to track through the Intermountain West early in the week as the low tries to track to our northeast, which will bring valley rain showers, thunderstorms and mountain snow across northern Utah and southwest Wyoming. The exception here will be Monday morning; wherein snow levels are forecast to be low enough to bring snow to area benches in the Wasatch Front. Accumulating snow is quite possible though most likely to be an inch or less. There's a less than 40% chance for more than that at this point. Otherwise, across most of northern Utah and southwest Wyoming, from Monday morning through Tuesday evening, on and off rain showers are forecast. What is a bit more favorable, unsurprisingly, is the persistent mountain snow. Snow amounts Monday alone across the northern Utah mountains are forecast to range between 5 to 12 inches (3 to 8 inches in the western Uintas) while amounts Tuesday will range from 4 to 10 inches (2 to 4 inches in the western Uintas). The confidence in snowfall amounts is lowest by the end of this event, on Tuesday evening. Additionally, there remains potential for lake effect driven showers every morning from Monday through Wednesday which would bring additional QPF amounts to favored areas downstream. The latest guidance is favoring Wednesday morning, interestingly. While strongest winds are forecast over the weekend, Monday afternoon looks to continue with that trend with some stronger winds for the Uinta Basin and southwest Wyoming, potentially impacting travel on I-80. Gusts in the 50+mph range are forecast and may warrant headlines in the future. Dry conditions are forecast across central and southern Utah early next week with the exception of the central mountains and the Tushar Mountains where a few inches of snow are forecast. Normally for early May, high temperatures for Salt Lake City will reach the upper 60s to 70 degrees. However, forecast high temperatures this Monday, Tuesday and Wednesday are forecast 15 to 20 degrees below average and will instead barely climb into the low 50s. A similar trend is noted for minimum temperatures. Temperatures are expected to be coldest Wednesday morning, so cold in fact that low temperatures are expected near or below the freezing for several valley locations. The EFI and Shift of Tails guidance support these anomalously cold temperatures for this time frame. If these trends persist, certainly freeze headlines would be warranted. If you need to plan ahead for agricultural reasons now is your time to plan for frost and freeze. A fairly dry forecast remains in the forecast for the remainder of the week however toward the end of the week Utah may see some wrap around moisture associated with the same area of low pressure from earlier in the week. Deterministic models are showing this low tracking back through Utah Friday and bringing modest amounts of moisture with it. Positioning of the low and how much moisture it would bring are of course, pretty uncertain at this point. Right now eastern Utah and southwest Wyoming are the favored locations for any additional precipitation impacts. && .AVIATION...KSLC..VFR conditions will remain in place through the valid TAF period. Northwesterly winds will prevail through the mid- evening, transitioning to a southerly flow around 04Z. South winds remain in place through the day tomorrow, with gusts up to 30kts expected by the early afternoon. .REST OF UTAH AND SOUTHWEST WYOMING...VFR conditions are expected across the area through the valid TAF period. Isolated showers across northern Utah will diminish through the early evening hours, giving way to mostly clear skies overnight. Tomorrow, winds will increase out of the south, with peak gusts across the West Desert expected to exceed 50 kts. Along the I-15 corridor, peak gusts will vary between 30 and 35 kts. && .SLC WATCHES/WARNINGS/ADVISORIES... UT...High Wind Watch from Saturday afternoon through Sunday morning for UTZ115-122. WY...None. && $$ Cunningham/NDeSmet/Webber For more information from NOAA's National Weather Service visit... http://weather.gov/saltlakecity ####018006922#### FXUS66 KOTX 032204 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 304 PM PDT Fri May 3 2024 .SYNOPSIS... Temperatures on Saturday will be mild with highs in the 60s and low 70s. Bands of rain will spread into central Washington on Saturday. Widespread rain is expected on Sunday as a slow moving low moves through the Pacific Northwest. As the low pulls out of the region, look for cool, showery, and windy conditions Monday and Tuesday. Warmer and drier weather will likely arrive late next week. && .DISCUSSION... Tonight and Saturday: Clouds will be on the increase tonight into Saturday as a slow moving low off the coast of Washington this afternoon pushes into Oregon and northern California on Saturday. Rain will be slow to spread east of the Cascades. Chances for measurable rain will be less than 50 percent east of Omak, Waterville and Moses Lake until late Saturday evening. Even though Saturday will be mostly cloudy, temperatures will be mild. Morning lows will range from the 40s in north Idaho and northeast Washington to the low 50s in Moses Lake and Wenatchee. Highs are expected to be in the 60s Saturday for the majority of the Inland Northwest. Sunday: There is decent model agreement that the most significant precipitation with this slow moving low will occur south of Washington and Idaho Saturday and Sunday with a foot or more of snow for the high elevations of the Oregon Cascades and mountains of northern California. However, this storm should deliver some much needed rainfall to eastern Washington and north Idaho. Models often struggle with wrap around precipitation, and we have seen some variability in the ensembles the last few days with the timing and location of the deformation band wrapping into the Inland Northwest. The latest National Blend of Models (NBM) generates the most significant band of rain Sunday and Sunday night across the eastern third of Washington and over the north Idaho Panhandle. The NBM deterministic output (most likely scenario) has a swath of a quarter to half inch centered along the WA/ID state line Sunday and Sunday night. The NBM 75th percentile increases these amounts to localized amounts of two-thirds of an inch while the 25th percentile knocks amounts in the rain band down to a tenth to quarter of an inch. Rains across the Palouse and West Plains will be welcomely received by dryland farmers after a dry April. However, outdoor activities on Sunday will be dampened by the rain and much below average temperatures. Places that experience an all-day rain may struggle to get out of the 40s Sunday afternoon including Spokane, Pullman, and the Idaho Panhandle. Places like Omak and the Methow Valley may remain north of the main rain band and have a good chance of topping out in the 60s. Monday and Tuesday: The beginning of the work week will be cooler than average, showery, and locally windy. As our deep weekend low migrates eastward, a tight westerly pressure gradient will set up across the Cascades on Monday. Then on Tuesday, a fast moving shortwave descending from the Gulf of Alaska will dig into the Pacific Northwest delivering another round of gusty west winds. Guidance form the ECMWF ensembles suggest that wind gusts of 30 to 35 mph will be a good bet Monday with 70 percent of members generating gusts of 35 mph or higher across the open country of southeast and east central Washington on Monday and 50 percent of members on Tuesday. Showers will be more widespread Monday with a 60 to 80 percent chance of measurable precipitation over the Idaho Panhandle and the eastern third of Washington. Shower chances should decrease on Tuesday as drier air accompanies the Gulf of Alaska system, however snow levels will drop unseasonably low Tuesday...as low as 3000 feet in the morning and again overnight into Wednesday morning. If you haven't gotten your fill of graupel this spring, Tuesday will give you another shot at seeing our "corn snow", "snow pellets", or (insert your favorite graupel name). Wednesday and Thursday: The medium range models are trending toward a more amplified ridge/trough pattern over North America by mid to late week. While there are some differences in where the ridge axis will set up by Thursday and Friday of next week, the majority of the ensemble members are forecasting above average temperatures and dry weather Thursday and Friday. The NBM advertises highs in the mid 60s to mid 70s Thursday and widespread 70s for Friday. /GKoch && .AVIATION... 18Z TAFS: Cumulus build ups and isolated showers over the mountains of northeast Washington and in the Idaho Panhandle this afternoon. A low pressure system will move slowly onshore off of the eastern Pacific tonight. This will spread mid to high level clouds across the region. Light rain is expect across the Cascades by the morning hours on Saturday with rain at KEAT by 14-16Z. Ceilings down to 3-4 kft agl. with MVFR conditions possible. South and easterly winds will pick up with the front approaching through the day today into Saturday as well. KPUW and KCOE will see the potential for gusts of 15-25 kts overnight into Saturday morning with the easterly pressure gradient tightening up. FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: High confidence for VFR conditions through Saturday afternoon except for at KEAT where confidence is moderate. The HREF/NBM model guidance for KEAT indicates a 30% chance ceilings lower down to between 2-3 kft agl. and visibility down to 4-6 miles with rain by 15Z. /SVH ----------------------- 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 45 69 42 49 40 56 / 0 10 40 90 80 40 Coeur d'Alene 42 68 42 49 39 52 / 0 10 30 90 90 60 Pullman 46 65 39 45 38 52 / 0 10 80 100 80 60 Lewiston 47 73 46 54 44 59 / 0 10 90 100 80 60 Colville 40 68 42 57 38 60 / 10 20 20 90 80 70 Sandpoint 42 66 44 51 39 52 / 0 10 30 90 90 80 Kellogg 43 65 44 48 40 47 / 0 10 40 100 90 80 Moses Lake 53 71 44 58 42 63 / 10 40 60 80 30 10 Wenatchee 52 62 49 60 44 60 / 10 70 40 30 20 20 Omak 49 69 49 64 42 65 / 10 40 30 40 40 20 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...None. WA...None. && $$ ####018006781#### FXUS66 KMFR 032204 AFDMFR Area Forecast Discussion National Weather Service Medford OR 304 PM PDT Fri May 3 2024 .SHORT TERM...Through Monday morning...An approaching low pressure system is already bringing rainfall to the Oregon coast. Rainfall will continue through the night over Coos, Curry, and western Douglas counties. Precipitation will steadily move eastward across the area through Saturday. Coastal areas will see about 2 to 3 inches of rainfall while west side valleys will get between half an inch and an inch of rain. Klamath and Modoc counties will get similar amounts of rainfall while Lake County will generally get half an inch of rain or less. The heaviest amounts will be late tonight through early Saturday morning. This system is bringing unseasonably cold air aloft, which will bring snow levels down from their current 8000 feet to 3000 feet by Saturday morning. While most snowfall will remain over higher terrain, the amount of moisture and the fast drop in snow levels will bring periods of heavy snow to the Cascades and to western Siskiyou County. Currently, 4 to 6 inches of snow are expected at elevations above 4000 feet for the Cascades and Siskiyou ranges, with a 20-30% chance of more than 6 inches over the Cascades by Sunday morning. Additionally, high resolution guidance shows a 40- 80% chance of snowfall rates of 1 inch per hour Saturday morning. Due to the dangerous travel conditions that these conditions are expected to make, a Winter Weather Advisory is in place for parts of western Siskiyou County from 2 AM to 11 AM on Saturday and for the Cascades from 2 AM to 11 PM on Saturday. This system will also bring elevated winds, especially across elevated terrain east of the Cascades. A Wind Advisory is in place for higher terrain in Lake County from Saturday at 5 AM through 5 PM. Gusty winds reaching over 40 mph are expected in this time, while wind gusts could still exceed 30 mph in other areas of Klamath, Lake, and Modoc counties. One final impact from this system will be a drop in nighttime temperatures from Saturday to Sunday. Temperatures will drop to the high teens to mid 20s for areas east of the Cascades. Below freezing temperatures are also possible west of the Cascades, although right now only the Shasta and Scott valleys look to be significantly below freezing. A Freeze Watch is in place for those valleys on Sunday morning, but below freezing temperatures are possible for the Rogue and Illinois valleys as well. Future guidance will help determine if additional products will be needed, bur right now that looks unlikely. The effects of the system continue through Sunday, but are most likely limited to post-frontal showers over the Oregon coast and the Cascades. Cool daytime temperatures will continue and nighttime temperatures look to warm from Saturday night's levels. -TAD .LONG TERM DISCUSSION...Models continue to show a front moving across the area on Monday with high chances (60 to 100 percent) across most the area. Precipitation amounts with this front on Monday will be mainly light with some moderate amounts (0.25 inches or more) over the Cascades, coastal mountains and along the coast. Snow levels will range from 4000 to 5500 feet. Additionally, models and ensembles support a slight chance (20%) for thunderstorms Monday afternoon across portions of southwest Oregon, including Coos, Douglas, Klamath and Lake Counties. Brief downpours and gusty winds may occur with any thunderstorms that develop. Then, moist, onshore flow will allow for lingering showers on Tuesday, especially across southwest Oregon zones with lesser chances across Northern California. High pressure builds into the area Wednesday and remains in place through the end of the wee. This will bring drier and much warmer weather. By Friday, high temperatures will likely be in the 80s for valleys west of the Cascades and in the 70s for valleys east of the Cascades. && .AVIATION...03/18Z TAFs...Prevailing VFR this morning will drop back to MVFR with local IFR cigs/vsbys as a potent cold front moves in, with periods of moderate to occasionally heavy precipitation this afternoon. VFR will prevail elsewhere inland through late this afternoon/early this evening. The front will spread moderate precipitation across the rest of the west side tonight, reaching east of the Cascades Saturday morning. Expect widespread MVFR conditions and local IFR in rain with higher terrain obscured in rain/snow. A rapid drop in freezing levels will occur overnight (~09-15Z) from west to east and especially around 12Z Saturday morning near the Cascades. Rain will change to snow down to as low as 2500 feet with brief heavy snow in the mountains, reducing visibility to LIFR at times. Breezy south winds are expected with the front too, with peak gusts in the 40-50 mph range. Despite the increasing winds, low level wind shear is not a concern at this time. Conditions should improve a bit behind the front with precipitation becoming more showery, but still with a good amount of MVFR ceilings/visibility through tomorrow morning. -Spilde/BPN && .MARINE...Updated 200 PM Friday, May 3, 2024...A cold front will move through today into this evening with moderate to heavy rain, gusty south winds and steep seas. Following the front, seas will remain steep, dominated by fresh short period west swell through tonight. Showers continue with a slight chance of thunderstorms (20%) on Saturday. West seas trend less steep Saturday afternoon through Sunday. Another front arrives Sunday night into Monday with the potential for gusty south to southwest winds followed by building west-northwest seas into Tuesday. After that, we expect high pressure to build in mid-late next week with a thermal trough strengthening along the coast. This will bring a return of stronger north winds and steep seas, highest south of Cape Blanco. -Spilde/BPN && .MFR WATCHES/WARNINGS/ADVISORIES... OR...Winter Weather Advisory from 2 AM to 11 PM PDT Saturday above 4000 feet for ORZ027-028. Wind Advisory from 5 AM to 5 PM PDT Saturday for ORZ030-031. CA...Winter Weather Advisory from 2 AM to 11 AM PDT Saturday above 4000 feet for CAZ080. Freeze Watch from late Saturday night through Sunday morning for CAZ080-081. PACIFIC COASTAL WATERS...Small Craft Advisory until 11 PM PDT this evening for PZZ350-356-370-376. && $$ TAD/CC/BPN