National Weather Service (2024)

Area Forecast Discussion
Issued by NWS Medford, OR

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-- Discussion containing changed information from previous version are highlighted. --721FXUS66 KMFR 202205AFDMFRArea Forecast DiscussionNational Weather Service Medford OR305 PM PDT Mon May 20 2024.SHORT TERM...
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A lot of fair weather cumulus remains over eastern Oregon thisafternoon with some lingering moisture across the region. As forlater tonight, high pressure will build as a subsidence inversiondevelops. There is a low potential for fog along the CentralOregon coast and into the Umpqua Valley tonight. One can seedewpoints dropping as we mix out, so there isn`t a whole lot ofmoisture in the boundary layer.In addition, temperatures will be on the cool side yet againas lows fall into the lower 40`s and even upper 30`s in somevalleys. There are indeed some cooler spots in the forecast areathat will be in the lower 30s. Those areas will probably see somepatchy frost tonight, but regions west of the Cascades on average shouldsteer clear of widespread frost or damaging freeze.Heading into Tuesday, temperatures will continue to trend warmerwith high pressure in control. Highs will trend about 5 degreeshigher farther inland with smaller trends along the coast. Otherthan some breezy northwest winds, The weather on Tuesday willremain fairly quiet before deeper northwest flow develops ahead ofthe next upper level wave. High and mid level clouds will be onthe increase by Tuesday evening. The NBM also brings increasingPoP chances to Coos, Douglas, and northern Lake and KlamathCounties as this next wave approaches other locations farther tothe south should remain relatively drier into Wednesday.Another thing that stood out was the strength of winds Wednesdayafternoon east of the Cascades. Forecast soundings show deepmixing all the way up top 700 mb as this low approaches with dryadiabatic lapse rates, which should really aid in momentumtransfer. Soundings suggests that there is a 50% chance for windgusts up to 45 mph over certain high terrain locations. Windyspots like Summer Lake and highway 31 could see wind gusts impactthose locations Wednesday afternoon.-Smith.LONG TERM...The longer term starts out with a cold front moving throughTuesday night as an upper level wave departs the region. The bestchances for rain remain outside of the forecast area or in theextreme northern portions of Douglas County. There aren`t manyweather impacts that we see on Wednesday before high pressurebegins to build on Thursday.Another wave arriving Friday appears to hitting northern Oregonand washington instead of southern Oregon. The result appears tobe a higher probability of drier weather in addition totemperatures. There are still likely some ensemble memberschoosing a more southern track with a very low chance ofprecipitation within southern Oregon and northern California onFriday. However, that seems like the least likely scenario at thispoint in time.The last topic worth noting is temperatures trending warmertowards the start of next week. Ensembles show 850 mb temperaturestaking a notable path higher and this can be seen in next Monday`sand Tuesday`s high temperature forecast. The region should seehighs in the lower 80`s with more late Spring like weather.
-- End Changed Discussion --&&.AVIATION...20/12Z TAFs...VFR conditions will continue through theTAF period, with north to northwest breezes in the afternoon andearly evening hours. Satellite indicates a deep push of marinemoisture inland tonight, but few clouds associated with this, mostof which are banked up again the terrain in the Umpqua and Roguevalleys. Another marine push tonight will result in slightly morecloudiness, though still VFR, in Coos and Douglas counties. -CSP&&.MARINE...
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Updated 200 PM Monday, May 20, 2024...North gales andvery steep, wind-driven seas south of Cape Blanco will continuethrough this evening. Model guidance continues to suggest periods ofoff-and-on gales south of Cape Blanco, and a Gale Warning remains inplace for the areas where these gales are expected to surface.Conditions will be relatively less severe north of Cape Blanco, butstill hazardous to small craft with breezy north winds and steepseas.Winds will diminish beginning tonight, then an area of low pressureapproaching from the north will disrupt the thermal trough onTuesday with winds and waves diminishing. Moderate winds will likelycontinue into Wednesday with northwest swell gradually increasingWednesday afternoon. -Schaaf/CSP
-- End Changed Discussion --&&.MFR WATCHES/WARNINGS/ADVISORIES...OR...CA...None.PACIFIC COASTAL WATERS...Small Craft Advisory until 11 AM PDT Tuesday for PZZ356-376.Small Craft Advisory until 11 PM PDT this evening for PZZ350- 370. Gale Warning until 11 PM PDT this evening for PZZ356-376.&&$$