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461
FXUS66 KMFR 240350
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
850 PM PDT Fri Jun 23 2017

.DISCUSSION...Evening update. The thermal trough has begun to shift
inland with Brookings already seeing a very quick 20 degree cool
down as the Chetco winds ceased. This will make tomorrow the hotted
day of the stretch as the thermal trough shifts over the Cascades
and the current forecast high at Medford still looks on track.
Current forecast looks on track and will not update this evening.
Sven

PREVIOUS DISCUSSION...Very hot and dry conditions today through
Sunday will be followed by a chance for thunderstorms late Sunday
into Monday. This magnitude and duration of hot weather in June has
not been observed in the Rogue Valley since the 1960s and will pose
a threat to public safety. Additionally, the thunderstorms that
follow the heat could result in new wildfires in the forecast area.

The Southern Oregon coast near Brookings, which has experienced
temperatures in the 80s the past few days, is now seeing more normal
temperatures in the 60s as a coastal surge of cooler air and clouds
moves south to north. It will take until Sunday to really cool down
in the North Bend area as the surge slowly moves up the coast. We
have increased temperatures for North Bend for Saturday based on
the latest guidance and the understanding that guidance can
underforecast high temperatures in these highly anomalous
situations. For most inland areas, the heat will peak on Saturday.
Daily Record high temperatures are possible for several locations
on Saturday and Sunday. Substantial cooling won`t occur until
Monday when readings dip to only 10 degrees above normal, compared
to the 25 degrees above normal that are expected over the
weekend. Heat Advisories and Excessive Heat Warnings have been
issued for most inland areas west of the Cascades for the weekend.
We want to emphasize some safety tips because over the past 30
years, more weather-related fatalities have occurred due to heat
compared to any other weather. Here they are:

* Beat the heat, check the backseat. Never leave people or pets in
  vehicles.
* Rivers are dangerously cold and have strong currents. Wear a
  life jacket if swimming.
* Monitor older adults, young children and those who are sick.
* Take plenty of rest breaks in shade or air conditioning.
* Drink water before, during and after activities.

As is typical with any waning of a heat wave, the upper ridge of
high pressure pushes east, moisture and instability move into the
forecast area, and thunderstorms are possible as the area
transitions to cooler conditions. This happens on Sunday and
Monday as moisture and energy are introduced into the forecast
area from the south and west. Of particular interest is upper
level instability present on Sunday night from the Cascades
westward, bringing the potential for nighttime thunderstorms.
Often storms at night have less rainfall than afternoon storms,
and this can result in a better chance for new fire starts. Fire
Weather Watches have been issued to account for the chance of new
fire starts due to lightning.

Monday will feature gusty west winds, especially east of the
Cascades, as the cooler air mass enters the forecast area.
Temperatures will actually reach near normal readings by Tuesday and
this should continue for most of the week.

&&

.AVIATION...23/18Z TAF CYCLE...VFR conditions will continue at all
inland terminals through the TAF period. There appears to be a good
chance for MVFR visibility in light fog to redevelop at OTH after 04z
this evening and worsen some toward 12z. MTS/Wright

&&

.MARINE...Updated 200 PM Friday, 23 June 2017...The thermal trough
will slide inland, allowing southerly winds and fog to surge up the
coast through tonight. The south winds should reach Cape Blanco by
Saturday afternoon, then spread north to Florence by Saturday
evening. Until then, residual steep seas will continue to produce
small craft advisory conditions for almost all areas, with very
steep and hazardous seas expected south of Cape Blanco through this
evening. Relatively calm conditions are forecast for early next
week, then the thermal trough is expected to return by midweek.
-BPN

&&

.FIRE WEATHER...Extremely hot, dry weather conditions today through
the weekend will help to dry fuels and set the stage for possible
fire starts as thunderstorms develop later Sunday into Monday. While
heavier fuels are still wet and do not necessarily support fire
spread or growth, finer fuels are approaching seasonal dryness
levels. Furthermore, there is the potential for considerable
lightning in the mountains and northern east side Sunday afternoon
through Monday afternoon as well as some chance for nocturnal storms
even over the west side Sunday night. In addition, breezy winds are
expected Monday afternoon and Tuesday. As a result, we will be
issuing a fire weather watch for parts of our area primarily for the
potential of increased initial attack activity. -Wright

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...     Fire Weather Watch from Monday morning through Monday
evening      for ORZ625.      Heat Advisory from 11 AM Saturday to 8
PM PDT Sunday for      ORZ023>028.      Excessive Heat Warning from
11 AM Saturday to 8 PM PDT Sunday      for ORZ023>028.      Fire
Weather Watch from Sunday afternoon through Monday      afternoon
for ORZ621-623.      Fire Weather Watch from Sunday afternoon
through Monday morning      for ORZ620-622.      Fire Weather Watch
from Sunday afternoon through Monday evening      for ORZ624.

CA...Heat Advisory from 11 AM Saturday to 8 PM PDT Sunday for
     CAZ080-081.
     Excessive Heat Warning from 11 AM Saturday to 8 PM PDT Sunday
     for CAZ080-081.
     Fire Weather Watch from Sunday afternoon through Monday
     afternoon for CAZ280.

Pacific Coastal Waters...Small Craft Advisory until 11 PM PDT this
evening for      PZZ350-356-370-376.      Small Craft Advisory for
hazardous seas from 11 PM this evening      to 5 PM PDT Saturday for
PZZ350-356-370-376.      Hazardous Seas Warning until 11 PM PDT this
evening for PZZ376.

$$

NSK/NSK/TRW