FXUS66 KMFR 262058

AFDMFR



Area Forecast Discussion

National Weather Service Medford OR

158 PM PDT Thu Jun 26 2025



.DISCUSSION...The overhead trough has once again provided support

for a strong marine push along the coast this morning, where 

stratus and fog pushed into all the coastal valleys and into the 

Umpqua Basin all the way to Roseburg. A very similar push is 

expected again tonight into Friday morning, although this one

may be a bit weaker and make less headway inland. 



Temperatures will remain around or just above normal for this 

time of year through Friday. Daily marine layer pushes will 

continue at the coast and coastal valleys as well. Ridging will 

build into the area beginning Saturday, along with the 

redevelopment of the thermal trough over California and the 

southern Oregon coast, and as a result, we will see temperatures 

rise by about 5 to 10 degrees Saturday, and again on Sunday. 

Sunday will be the warmest day of this warm spell for areas west 

of the Cascades, then Monday could be the warmest for the East 

Side (although cloudiness from thunderstorms and monsoonal 

moisture inflow could limit high temperatures Monday, more on 

that below). The West Side valleys on Sunday will see highs in the

upper 90s to low 100s, while the highs on Monday for the East 

Side will peak out around 90 to 95. Temperatures will then cool 

slightly heading further into next week, but will remain above 

normal. 



As is typical with periods of heat in the region, it will come to

an end with the threat of thunderstorms. With the ridge passing 

just to our east and strengthening as it moves over the Rockies, a

trough develops off the coast of California, which then attempts 

to move onshore around Monday or Tuesday, taking on a negative 

tilt as it does so. This is a classic pattern for convection here,

with the trough tapping into monsoonal moisture from the south, 

and taking advantage of the warm surface temperatures and cooler 

temperatures aloft to produce instability across the inland 

portions of the forecast area. 



Convection may begin as early as Sunday afternoon over far 

southern portions of Siskiyou and Modoc counties, depending on 

how far north the moisture will get by the peak heating hours of 

the afternoon. Confidence on thunder Sunday afternoon is low, and 

wording has been left out of the forecast, but the chance is 

there. Most likely, Sunday will be the "priming-of-the-pump" day, 

with little convection but definite signs of increasing moisture. 

As moisture continues to push north into our area, and with some 

support from weak energy aloft, more widespread convection could 

then begin as soon as early Monday morning (very low probability),

although the most likely scenario has convective initiation 

beginning Monday afternoon. I suspect that the area will be 

greeted by altocumulus clouds and a feeling of "high" humidity 

Monday morning, showing the arrival of the moisture and potential 

instability of that afternoon. 



Given the pattern, thunderstorms could form up anywhere east of 

the coastal ranges Monday, with the marine layer limiting

development along the coast and perhaps into the Umpqua Basin as

well. Most convection should be concentrated along the Klamath, 

Siskiyou, and Cascade mountains, as well as the East Side, with

cells then drifting off the terrain and into the valleys. 

Steering flow appears weak, so storms may be slow moving, leading

to more hit-or-miss "popcorn" style convection. 



Some models then continue shower and perhaps thunderstorm

activity overnight, although confidence on that is low. There is 

much more confidence on thunderstorms reforming Tuesday afternoon,

although with the eastward progression of the trough, the best 

dynamics and support would then be over northern California and 

along and east of the Cascades. Other than location, storm 

behavior and character should be very similar to Monday. Storms 

could then continue on the East Side into Tuesday night, with 

some models even keeping some form of convective showers over Lake

County into Wednesday afternoon. 



In short, it is nearly a certain thing that there will be 

lighting across the majority of the forecast area both Monday and

Tuesday afternoons. Based on current guidance, we do not expect 

very strong or severe thunderstorms, but small hail and gusty 

winds are possible. Also, given the high moisture content in the 

atmosphere that the models are depicting, these storms will be 

wet, and could produce periods of moderate to heavy rainfall. As 

always with thunderstorms, lightning will be a threat, not only in

regards to new wildfire starts, but also to anyone attempting to 

enjoy outdoor recreation in the area. 



One caveat to this scenario will be cloud cover. With this much 

moisture entering the area, and with the widespread convection 

expected Monday, there may be extensive cloud cover over the area

Tuesday limiting incoming solar energy, keeping temperatures

lower, and limiting instability. This has occured with events 

like this in the past, and has significantly reduced thunderstorm 

development and blown the forecast on the second or third day, 

and this may be another example. Keep up to date with the latest 

forecasts as the details regarding this thunderstorm threat become

more clear over the next few days.



Broad cyclonic flow and lower heights then continue over the

area for the remainder of the forecast term (midweek next week).

This should keep temperatures at or just above normal, with 

mostly dry conditions. -BPN





&&



.AVIATION...26/18Z TAFs...Marine MVFR ceilings are retreating to the 

coast, and most areas should be VFR for at least a few hours this 

afternoon, although lower conditions may linger longest along the 

coast. The marine layer will return again this evening through 

tonight, with ceilings and visibilities expected to be very similar to 

those of last night into the morning. 



Elsewhere, VFR will prevail through this evening, though scattered 

afternoon cumulus buildups are expected again this afternoon and 

evening, mainly from the Cascades eastward and in Siskiyou County. 

Expect the typical increase in afternoon/evening winds, though 

should be slightly weaker than they were on Wednesday and closer to 

seasonable values of 15 to 25 kt. -BPN 



&&



.MARINE...Updated 200 PM PDT Thursday, June 26, 2025...Relatively 

calm conditions will continue into this evening with light winds and 

low seas. The exception will be south of Gold Beach where a 

developing thermal trough will result in winds increasing mainly 

south of Gold Beach late this afternoon and tonight. However, winds 

will remain below advisory levels. The thermal trough strengthens on 

Friday and even more so over the weekend. Conditions hazardous to 

small craft will develop Friday afternoon from Cape Blanco south as 

north winds increase and seas steepen. Winds will be strongest south 

of Gold Beach. 



Winds will increase further Saturday as advisory level winds and 

seas likely spread north of Cape Blanco, with gales and very steep 

seas possible south of Cape Blanco. The outlook for next week is for 

the thermal trough to remain strong and maintain hazardous 

conditions, especially south of Cape Blanco. -Petrucelli



&&



.FIRE WEATHER...Updated 200 PM PDT Thursday, June 26, 2025...Mostly 

low impact fire weather conditions are expected the rest of this 

week with fairly typical diurnal (afternoon/evening) breezes, 

seasonable humidity and near to above normal warmth. 



A strengthening upper ridge will bring hotter weather to all but the 

immediate coast this weekend with continued drying. Even the south 

coast could have highs in the 70sto near 80F Saturday (maybe Sunday 

too?). A brief period of enhanced E-NE winds at the mid slope/ridge 

level is expected Friday night and again Saturday night. However 

overnight recoveries Friday not don't look all that bad. Saturday 

overnight recoveries will be moderate, but probably not enough to be 

concerned about any watches/warnings. Temperatures increase across 

the interior Saturday with widespread highs in the 90s on Sunday.

Monday will be the hottest day, with afternoon temperatures near or 

at triple digit values for the interior westside valleys.



At the same time, an upper low will consolidate off the California 

coast Sunday. The upper ridge shifts to the Four Corners region and 

this pattern sets up south to southeast flow aloft from California 

into southern Oregon. This will begin to tap into some monsoonal 

moisture that will slide up into northern California Sunday 

afternoon and evening. The most likely scenario Sunday afternoon 

into Sunday night will be building cumulus over the mountains in 

northern California, because there is little or no trigger, mid 

level moisture is lacking and instability is marginal at best. Worst 

case scenario will be a couple of isolated storms near the Trinity 

Horn and points northeastward towards the Shasta Valley late in the 

afternoon and early evening hours Sunday. In summary, Sunday will be 

the day in which the pump is primed for whats expected for Monday.



Monsoonal moisture will increase late Sunday night through Monday 

and at the same time mid level moisture and trigger will increase. 

This will set the table for resulting in thunderstorms over most of 

the area inland away from the coast, with storms developing as early 

as Monday morning. Right now, the expectation is for thunderstorms 

to be isolated Monday morning, then the shear number and areas 

affected increasing Monday afternoon into Monday evening. 



It's worth noting the risk for nocturnal storms are next to, but not 

zero Sunday night, with an elevated risk for lightning Monday and 

Tuesday night. The main storm threat shifts to the Cascades and 

points south and east Tuesday into Wednesday. As fuels continue to 

dry out and the calendar shifts from June to July, fire danger will 

increase. So, be on the lookout for potential Fire Weather 

Watches/Red Flag Warnings as we head into next week. -Petrucelli



&&



.MFR WATCHES/WARNINGS/ADVISORIES...

OR...CA...None.



PACIFIC COASTAL WATERS...Small Craft Advisory from 2 PM Friday to 11 

     AM PDT Saturday for PZZ356-376. 



&&



$$

