Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 241536
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
836 AM PDT Sat Jun 24 2017

.DISCUSSION...Today`s temperatures are expected to be the highest
June readings since 1992, and this stretch of extreme heat in June
hasn`t been observed in the Rogue Valley since the 1960s.
Excessive Heat Warnings and Heat Advisories continue through
Sunday for these high temperatures. Please heed these safety tips
through Sunday.

* Beat the heat, check the backseat. Never leave people or pets in
  vehicles.
* Rivers are dangerously cold and have strong currents. Wear a
  lift 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.

Temperatures will start to lower out of the dangerous category on
Monday.

The transition from very hot to cooler conditions will bring a
chance for thunderstorms Sunday and Monday as moisture is ushered
in from the south and energy moves in from the south and west.
This poses significant fire weather concerns, and we`ll be focused
on forecast challenges surrounding that today.

Please see the previous forecast discussion below for more details
on the heat and expected thunderstorms late Sunday into
Monday.

&&

.AVIATION...24/12Z TAF CYCLE...VFR conditions will continue at all
inland terminals through the TAF period. Along the coast...a surge
of fog and low stratus is working its way north along the coastline
today. This will bring areas of MVFR cigs/vis to the southern Oregon
coast this morning, mainly from south of Cape Blanco. The southerly
fog/stratus surge with a mix of IFR/MVFR cigs and vis is likely to
spread north and become widespread along the coast Saturday evening
and Saturday night, including at KOTH. -CC

&&

.MARINE...Updated 300 AM Saturday, 24 June 2017...The thermal
trough has expanded northward and will move inland today. This will
allow southerly winds and fog to surge up the coast today The south
winds should reach Cape Blanco by early this afternoon, then spread
north to Florence by this evening. Until then, residual steep seas
will continue to produce small craft advisory conditions for coastal
waters. Relatively calm conditions are forecast Sunday into Monday,
then the thermal trough is expected to return by midweek. This will
bring a return of gusty north winds and steep to very steep seas.
-CC

&&

.FIRE WEATHER...Extremely hot, dry weather conditions through
the weekend will help to dry fuels and set the stage for possible
fire starts as thunderstorms develop late Sunday afternoon through
Monday evening. While heavier fuels are still wet and do not
necessarily support fire spread or growth, finer fuels are
approaching seasonal dryness levels.  The best chance for scattered
thunderstorms with abundant lightning will be in the mountains in
northwest California and southwest Oregon on Sunday and from the
Siskiyous and western slopes of the Cascades eastward on Monday.
Western valleys will also see a chance for storms, mainly Sunday
evening through Sunday night and again Monday afternoon. In
addition, breezy winds are expected Monday afternoon and Tuesday. As
a result, we have issued g a fire weather watch for parts of our
area primarily for the potential of increased initial attack
activity. -CC


&&

.PREV DISCUSSION... /Issued 705 AM PDT Sat Jun 24 2017/

DISCUSSION...Strong high pressure and hot weather is the main
story for today. The upper ridge is shifting inland over the
Pacific Northwest today with the coastal thermal trough following.
This transition brings an end to the offshore flow that has
brought hot temperatures and windy weather to portions of the
south coast over the past few days, and will increase the heat
over the inland areas.

Record highs will be tied or broken in many inland areas with
highs ranging from mid 90s to near 110. An Excessive Heat Warning
and Advisory remains in effect the hottest locations today
through Sunday afternoon. Please heed the safety information
regarding hydration, limited outdoor activity, car safety, and
cold water safety.

The upper ridge axis shifts eastward into Idaho on Sunday with a
robust upper low approaching the region from the southwest. With a
slightly cooler airmass in place and increased cloudiness,
temperatures will cool off several degrees, but it will remain
HOT.

Thunderstorms are possible as the upper low ushers in moist and
unstable southerly flow Sunday afternoon and evening, with a
continuing chance during the overnight hours. The center of the
upper low is progged to move across the county warning area during
the day Monday with the main threat for storms over the Cascades
and east but uncertainty keeps much of the west side in slight to
chance probabilities mainly east of a line from Roseburg to Grants
Pass to Happy Camp. The timing of the low moving east suggests
better confidence that activity will shift primarily east of the
Cascades through Monday evening.

Considering a fair degree of instability advertised both days and
well above precipitable water values, severe thunderstorms could
occur either day, however Monday looks like the better day as the
upper jet moves in ahead of the main shortwave providing ample
wind shear.

Low pressure and cooler weather prevail over the area Tuesday and
Wednesday with high pressure rebuilding later in the week. Stavish

&&

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

CA...Heat Advisory until 8 PM PDT Sunday for CAZ080-081.
     Excessive Heat Warning until 8 PM PDT Sunday for CAZ080-081.
     Fire Weather Watch from Sunday afternoon through Monday
     afternoon for CAZ280.
     Fire Weather Watch from Monday morning through Monday afternoon
     for CAZ281.

Pacific Coastal Waters...Small Craft Advisory for hazardous seas until 11 AM PDT this
     morning for PZZ350-356-370-376.

$$

NSK/MTS/CC



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