609
FXUS66 KMFR 270953
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
253 AM PDT Sun Sep 27 2026

.KEY MESSAGES...

* Cooler than normal today with isolated showers and t-storms
  this afternoon/evening over NorCal and southern Oregon,
  especially mountains.

* Dry with similar temperatures Monday.

* Front dissipates to the north Tuesday with upper ridging
  resulting in a warming trend Wednesday and Thursday.

* Slight cooling is possible Friday, then warm again next
  weekend.

&&


.DISCUSSION...An upper trough will move across the area today
forming a closed low in NorCal by this evening. Temperatures
remain about 5 F or so below normal. Satellite imagery is showing
mid and high level cloudiness streaming in ahead of this system
currently with some radar returns already showing up in
Modoc/southern Lake counties early this morning. However, there
hasn`t been any indication yet that this is reaching the ground
(probably mostly virga).

Models continue to trend upward with their depictions of moisture/
instability this afternoon/evening. CAMs are showing 2 separate
areas, one from the mountains of western Siskiyou County up along
the Cascades (near Crater Lake) and another from Modoc County up
into portions of Lake County. CAPE values are mostly in the
100-200 J/KG range, but the highest CAPE exists in western
Siskiyou County (200-500 J/KG). These values support development
of isolated showers, and where CAPE is highest, a few lightning
strikes/flashes. Not a big event, but isolated showers/thunder
nonetheless. All in all, lightning probabilities are in the 5-15%
range. There is also a very low chance (5%) something pops up west
of the Cascades and east of the coast ranges, but most west side
locations stay dry.

Showers could linger into the late evening hours tonight, but
should diminish and end overnight as the closed low moves
southeastward through California and eventually into southern
Nevada/Arizona Monday/Tuesday. Short wave ridging over the area
Monday will result in dry weather here, though temperatures won`t
change all that much from where they are today.

Models continue to show a weakening front moving onshore into the
PacNW to our north on Tuesday. This front will get strung out in
zonal flow aloft and we`re not expecting precipitation to reach
this far south. In fact, upper ridging should take hold again
Wednesday/Thursday resulting in a warming trend with dry weather.

Another trough moves over the top of the ridge on Friday which
could bring slight cooling, but the ridge rebuilds next weekend,
so another warm period is likely. -Spilde

&&

.AVIATION...27/12Z TAFs...VFR conditions prevail through the TAF
period for most areas, with a few patches of coastal or Umpqua
Valley stratus possible early this morning as northeast low level
winds back to north. High clouds will continue to stream over the
area ahead of an incoming low pressure that will move inland
today. Conditions will remain VFR, but it could generate a few
showers, virga, or an isolated thunderstorm in the afternoon and
early evening, with the highest chances (10-20%) for western
Siskiyou County and the Cascades. Expect another round of gusty
north winds along the coast this afternoon into the early evening.
IFR stratus/fog stands the best chance of returning to the Coos
coast late tonight or Monday morning. -Spilde

&&

.MARINE...Updated 200 AM PDT Sunday, September 27, 2026...
A thermal trough pattern will keep gusty north winds and steep short
periods seas over all coastal waters through tonight, and then south
of Cape Blanco through Monday evening. West-northwest swell arrives
Monday with conditions improving a bit Tuesday, especially north of
Cape Blanco. The thermal trough could re-strengthen Wednesday.
-Spilde


&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...CA...None.

PACIFIC COASTAL WATERS...Small Craft Advisory until 11 PM PDT Monday
     for PZZ356-376.

Small Craft Advisory until 8 AM PDT Monday for PZZ350-370.

&&

$$

MAS