Weather Service Report


151 
FXUS66 KMFR 151001
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
301 AM PDT Mon Oct 15 2018

.DISCUSSION...It will remain dry through at least next weekend with 
mild to warm afternoons and cool nights will continue through with 
clear skies for inland locations. A strong upper ridge will persist 
just west of the forecast area today, then shift east over the area 
Tuesday and remain over our forecast area through next weekend. 

Not much has changed in the last 24 hours. The thermal trough 
remains along the coast with breezy east to northeast winds along 
the coastal mountains in southwest Oregon and mid slopes and ridges 
in western Siskiyou county. Along the coast it's a bit more tricky. 
The latest fog image shows marine stratus along or just barely off 
the the coast from about Bandon south. Brookings is currently clear 
with light offshore flow and a temperature of 66 degrees. Meanwhile 
just up the coast at Gold Beach it's 50 degrees with a 100% 
humidity.   

Wind sheltered areas in the westside valleys early this morning are 
cool due to a shallow inversion. However not far above the inversion 
layer, temperatures are milder and its windy. For example, Ashland 
is in the mid 50s with breezy east to southeast winds while the 
Medford Airport is cooler with a light north wind. The high res 
models show 925 winds between 25-30 kts and given what happened 
yesterday, would not be surprised if some of those stronger winds 
surface in the Rogue Valley by mid morning. The thermal trough will 
shift inland over the westside valleys this afternoon, therefore any 
increase in winds this morning should decrease this afternoon. This 
will also lead to a milder afternoon.  

The thermal trough will shift west of the valleys tonight, as is 
typical in this type of pattern. Generally, it will be cool to 
chilly in the valleys west of the Cascades due to a combination of 
light winds, clear skies, longer nights and a dry air mass in place. 
So we could see temperatures drop near or just below freezing in 
portions of the Rogue, Applegate and Illinois Valley late tonight 
into Tuesday morning, especially in wind sheltered areas. The models 
suggest overnight temperatures for some of the westside valleys 
could end up even lower than this morning which could include some 
of the valleys in Siskiyou County and portions of the Umpqua Basin. 
Note: Some of the high res models show 925 winds between 25-30 kts 
from the southeast, therefore Ashland could end up milder with 
breezy southeast winds again tonight. 

A freeze warning and frost advisory remains in effect until 9 am pdt 
this morning and a freeze watch has been issued for tonight into 
Tuesday morning for portions of the Illinois and valleys in Siskiyou 
County. Please see NPWMFR for more details.  

The thermal trough will remain along or just west of the Cascades 
through the end of the week during the afternoons, then shift west 
near the coast at night. 

The operational models are hinting at a pattern change by the start 
of next week as an upper trough digs down in the eastern Pacific and 
shifting the ridge east of our area. Taking the models at face value 
would bring first chance of rain by Monday evening along the coast. 
-Petrucelli


&&

.AVIATION...For the 15/06Z TAFs...VFR will prevail through Monday 
afternoon with the exception of a band of LIFR now near shore from 
Brookings to Gold Beach that is expected to push north overnight to 
Cape Blanco but also push offshore from Brookings. Otherwise, gusty 
east to southeast low level winds from the Cascades eastward are now 
at a peak with gusts up to 35 knots, but will remain breezy through 
Monday morning. These winds will surface locally and persist at 
Ashland into Monday afternoon. -DW


&&

.MARINE...Updated 200 AM PDT Monday 15 October 2018...Winds have
weakened and will generally remain below 15 kts through the week. 
Residual fresh swell will continue through early this morning and 
seas will subside to around 5 feet later this morning. Meanwhile, 
persistent long period southerly swell of around 3 feet may produce 
rough bar conditions at Brookings and elevated surf at Port Orford. 
Aside from this persistent southerly swell, conditions will remain 
relatively calm today and Tuesday. 

Wednesday into Thursday, a longer period west to northwest swell at 
16 to 18 seconds will build into the coastal waters. This will 
combine with the aforementioned smaller long period southerly swell 
and could make for hazardous bar conditions Wednesday into Thursday. 
Overall, wave heights will remain below 10 feet as this is only a 7-
8 foot swell, but given the longer period swell, surf conditions 
could be a concern as well. Breaker heights of 10 to 12 feet are 
possible Wednesday into Thursday and this could catch some beach-
goers off guard as this is a bit higher than what has been typical 
for the past few weeks. Swell will diminish Thursday night as the 
period shortens, and seas will subside again by the weekend. /BR-y

&&

.FIRE WEATHER...Updated 300 AM PDT Monday, 15 October 2018... 
Dry to very dry air continues to spread and dry further today as 
easterly winds continue. Wind gusts in the 25 to 40 mph range have 
been observed in the Curry County coastal mountains, across the 
higher terrain of western Siskiyou County, in the Cascades and 
Siskiyous, and in the Ashland area of the Rogue Valley. The latest 
fog image shows the a hot spot on the infamous Klondike Fire out of 
the northwestern portion of the perimeter.  

Later this morning we'll see the pressure gradient and resultant 
winds lessen substantially across the coastal mountains as the 
thermal trough shifts inland. For all areas, except for elevations 
below 500 feet along and near the the immediate coast, RHs will 
remain low today. 

We'll need to keep an eye on at least a couple more items: 

The first is that wind and RH could go back into RFW criteria for 
portions of FWZ 280 and 621 tonight into Tuesday morning. High 
resolution guidance and some MOS guidance are indicating wind and RH 
hovering close to the lower end of criteria. However, conditions are 
not going to be as widespread or critical as they will be through 
Monday morning, so plan to cover this with a headline once the RFW 
expires later this morning. If guidance trends up or obs are slower 
than expected in moving out of criteria, then we would need to 
extend the current warning out in time.

The second item of concern is the drying that has occurred this 
weekend and it's resultant effect on the 'real deal' fire danger. 
WFAS.net indicates that some areas have moved beyond moderate fire 
danger, so we're going to send out predicted #s today to get better 
forecast fire danger #s for tomorrow. Additionally, the Haines Index 
across much of the interior west side Tuesday through Thursday (a 
mix between the mid and high calculation) is forecast to 5-6.

While winds do fade this week and RHs come up some, the trend will 
be very slow and may hit a drier bump again next weekend per the 
latest operational GFS. The general east flow at night/into the 
morning hours does not go away until Sunday night, so the pattern is 
not changing much, rather the winds are becoming lighter. As far as 
moisture goes, the ECMWF and GFS hint at the first chance of rain by 
Monday evening at the coast. -Lutz/Petrucelli


&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Frost Advisory until 9 AM PDT this morning for ORZ023-024-026. 
     Red Flag Warning until 11 AM PDT this morning for ORZ621. 
     Freeze Warning until 9 AM PDT this morning for ORZ024-026. 
     Freeze Watch from late tonight through Tuesday morning for 
     ORZ024-026. 

CA...Frost Advisory until 9 AM PDT this morning for CAZ080. 
     Red Flag Warning until 11 AM PDT this morning for CAZ280. 
     Freeze Warning until 9 AM PDT this morning for CAZ080>082. 
     Freeze Watch from late tonight through Tuesday morning for 
     CAZ080>082. 

Pacific Coastal Waters...Small Craft Advisory until 5 AM PDT early this morning for 
     PZZ370-376. 

$$

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Western Regional Climate Center, wrcc@dri.edu