####018006275#### FXUS65 KBYZ 091621 AFDBYZ Area Forecast Discussion National Weather Service Billings MT 1021 AM MDT Thu May 9 2024 .UPDATE... Upslope snow showers have recently become much more scattered along the northeast slopes of the Beartooth-Absaroka and Crazy Mountains, so have canceled the Winter Storm Warning for these areas. However, occasional snow showers (some heavy w/ a little accumulation) will continue in upslope areas this afternoon and into the evening. Otherwise, there remains enough low-mid level moisture and instability for more rain showers across our lower elevations today. Scattered activity exists now (including at Billings) but this will become more numerous in the afternoon with just a little surface heating. Convective temps are quite low. Temps today should warm to the mid 50s to mid 60s (warmest NE per driest air). High res models not suggesting fog tonight, and the light downslope winds work against fog potential, but boundary layer moisture seems to be too high to avoid at least localized fog late tonight. Something to watch. JKL && .DISCUSSION... Today through Friday Night... Satellite imagery showed deep northeasterly flow over our region rotating around a large upper low over the NE/SD border extending SW into Utah. Currently some drier air had infiltrated over our eastern zones and fog was developing due to the rich moisture in the lower boundary layer. Scattered to numerous showers continued over our western zones flowing into our mountains. Our current precipitation is being driven by warm air advection circulating around the weather system, and aided by associated jet dynamics and of course deep upslope flow. This is all creating strong moisture convergence from Yellowstone County southwestward into the Beartooths. Models indicate a continued stream of moisture and lift into our western zones today...and as instability picks up this afternoon we will see shower coverage increase again over our eastern zones as well. PoPs generally range from 100% over our north facing slopes to 20% in Fallon County. The main focus of precip will almost certainly be in areas from Billings south and southwest. Cross sections do indicate omega weakens and moisture becomes more shallow this afternoon. Thus, intensity of snowfall and other precip should continue, but be decreasing later today (high Pop and lower QPF scenario). Tonight...upper support for ascent will continue to weaken from north to south with precip coverage decreasing in similar fashion...and lingering over just our mountains by late tonight. Clouds will be decreasing as well and with plenty of low level moisture in the boundary layer, we expect to see areas of fog develop by Friday morning. After any fog burns off Friday...high pressure aloft will prevail leading to a pleasant spring day with highs warming into the 60s for most locations. Snowfall...Our winter storm warnings are valid through noon today. There is still several more inches possible through the rest of tonight and this morning. (prob of >6 additional inches up to 65%), but the snowfal rates and intensity should be notably lower by afternoon. Hydro Issues...Despite the relatively prolific widespread precipitation we have received...rivers are behaving themselves. The rise on the Tongue at Miles City is now down to 5 ft after peaking at 7.35 ft (flood stage 10 ft) and others are trending down as well. BT Saturday through Thursday... High pressure building into the region will bring warmer and mainly dry conditions for the weekend, with highs in the 70s through Monday. Confidence is high for above normal temperatures, with a greater than 70% chance of exceeding 70 degrees Saturday through Monday. Weak energy causing the ridge to flatten some on Sunday will bring low chances (15-30%) for afternoon showers. A shortwave dropping into the area from the northwest is progged for the second half of Monday, continuing through Tuesday. Showers and thunderstorms are possible (currently 30-50% chance), greatest near the foothills. Cyclonic flow will keep the potential for showers/thunderstorms through the middle of the week, along with cooler temperatures. The upcoming warmer temps will melt much of the wet snow that is currently falling at elevations between 6000-8000 feet. At this time we do not see a flood risk, but rivers/streams emerging from the foothills will likely see some rises this weekend. STP && .AVIATION... Occasional showers and mountain snowfall will continue to affect the area today, w/ the greatest shower coverage west of KMLS and near the mountains and foothills. Showers will decrease this evening. MVFR to IFR can be expected with the showers (poorest flying conditions along the foothills). Mountains will remain obscured due to snow, especially the northeast aspects. Drying will finally arrive late tonight into Friday, but localized visibility reductions due to fog are possible. JKL && .PRELIMINARY POINT TEMP/POPS... Tdy Fri Sat Sun Mon Tue Wed ------------------------------------------------------- BIL 059 041/066 044/075 048/077 051/078 050/069 046/069 6/W 40/U 00/U 12/T 12/T 35/T 34/T LVM 053 036/064 038/071 044/074 046/074 045/069 042/067 6/W 20/U 00/U 01/U 12/W 25/T 33/T HDN 061 040/067 039/076 045/078 048/078 048/070 044/069 6/W 50/U 00/U 12/T 13/T 45/T 34/T MLS 064 042/068 042/075 047/076 050/078 050/069 043/069 3/W 20/U 00/U 12/T 12/T 34/W 22/T 4BQ 061 043/066 041/075 047/076 049/077 048/069 043/068 5/W 30/U 00/U 01/U 12/T 44/T 22/T BHK 064 038/067 041/074 045/076 047/077 046/067 040/066 2/W 10/U 00/U 02/T 13/T 34/W 22/W SHR 056 039/065 036/072 042/074 045/075 045/067 042/066 6/W 61/B 00/U 02/T 13/T 56/T 44/T && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...None. WY...None. && $$ weather.gov/billings ####018002543#### FXUS66 KSGX 091624 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 925 AM PDT Thu May 9 2024 .SYNOPSIS... Marine layer clouds west of the mountains will clear back to near the coast each afternoon through Sunday. High temperatures west of the mountains will be similar each day through Sunday, while the mountains and deserts will see a few degrees of warming over the weekend. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... The marine layer depth on the 12Z NKX sounding this morning was 3,000 ft, 600 feet deeper than Wednesday morning, and the low clouds had spread several miles farther into the valleys at sunrise. Clouds with this deeper marine layer will be slower to clear back to the coast than yesterday, and may linger at some of the beaches this afternoon. The coastal eddy responsible for the deeper marine layer will weaken tonight and then dissipate entirely on Friday. As a result, the marine layer will not be as deep over weekend and the low clouds will not spread as far into the valleys. High temperatures west of the mountains will be fairly consistent with coastal highs from 65-75 and valley highs from 75-85. Mountains highs in the 60s today will warm into the 70s by Sunday. High desert highs in the mid 70s today will warm into the mid 80s by Sunday, and in the lower deserts, highs near 90 today will heat up to near 100 on Sunday. This temperature regime continues Monday through Wednesday when a weak Pacific trough moves inland across Southern California. && .AVIATION... 091605Z...Coast/Valleys...Low clouds beginning to clear inland at this hour. Bases are 2000-2500 ft MSL with tops near 4000 ft MSL. Higher terrain obscured with VIS 1-3SM where clouds and terrain intersect. The valleys should clear by 18Z then partial clearing at the coast 18Z-20Z. Local BKN conditions at the beaches into the afternoon. Low clouds will move ashore after 02Z, spreading inland tonight with very similar bases/vis and overall coverage by Friday morning. Mountains/Deserts...Clear skies with unrestricted VIS through tonight. && .MARINE... No hazardous marine conditions are expected through Monday. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...None. && $$ PUBLIC...Moede AVIATION/MARINE...PG