Hazardous Seas Warning 45, NWS Medford, OR

Area Forecast Discussion
National Weather Service Medford OR
1030 PM PDT SAT JUN 4 2016

.Updated aviation and marine discussions.

.DISCUSSION...Daily record high temperatures were tied or broken
at 5 observation sites in our forecast area. Roseburg and Klamath
Falls broke previous records of 92 and 89 respectively with
today's readings of 97 and 94. Medford, Mount Shasta City, and
Montague tied records of 100, 92, and 98 degrees. The air mass
featured record warmth today based on the afternoon balloon
sounding's 850mb temperature, but mixing and overall surface
temperatures were limited some by the high clouds today. The heat
wave continues through Monday, and a heat advisory at NPW
highlights this weather hazard.

Hot surface temperatures can be an important ingredient for
thunderstorms, but moisture is important too. Surface moisture has
increased sharply over the past 24 hours with dew point
temperatures in the 50s and 60s now. Midlevel moisture will be
increasing as well over the next 24-48 hours. The heat and
moisture, along with upper level disturbances rotating through the
area, will help generate thunderstorms from tonight through Monday
at least. The latest few runs of high resolution model (HRRR) data
flirt with the idea of nighttime thunderstorms moving from the
Cascades into the West Side valleys. Sunday and Monday afternoon
look more favorable for thunderstorms, and with high precipitable
water values and slow storm motion expected, heavy rain is
possible.

Please see the previous discussion below for details on the
heat and thunderstorm potential.

&&

.AVIATION...For the 05/06Z TAF cycle...VFR conditions will continue
at all inland terminals through tonight. At the coast, stratus and
fog with IFR to LIFR CIGS/VIS will develop along the north coast
(including KOTH) later tonight before clearing Sunday morning.  The
first of what are expected to be isolated thunderstorms will likely
develop over the Cascades or east side after midnight and increase
in coverage Sunday afternoon. A storm may drift out over portions of
the west side mainly east of I-5 early Sunday morning. Any
thunderstorms will be slow movers and may produce heavy rain and IFR
CIGS/VIS, especially tomorrow. SK/JL

&&

.MARINE...Updated 1030 PM PDT Sat 4 June 2016...Seas are lagging
behind weakening north winds so they remain barely in the hazardous
area in the outer waters.  Winds will then trend stronger into
Monday evening with gales possible south of Cape Blanco and beyond
10 nm as offshore high pressure approaches and a thermal trough
returns to the coast. Winds and seas will then diminish towards the
middle of the week. Confidence in the model solutions is lower
beyond Monday but there is the possibility of a frontal passage on
Tuesday and the pattern will likely remain active through the week.
JL/SK

&&

.PREV DISCUSSION... /Issued 240 PM PDT SAT JUN 4 2016/

SHORT TERM...A short wave continues to move into northern
California. As a result, clouds will continue to build this
afternoon and we're still expecting thunderstorms later tonight
into tomorrow. The primary focus of this forecast was on the
thunderstorms with the flash flooding potential on burn scars in
addition to high temperatures Sunday and Monday.

As this shortwave continues to move north, upper and mid level
moisture will increase Saturday night through Sunday with
precipitable water around 1 to 1.5 inches, which is very abnormal
for this area. The latest HRRR run is showing convection firing
this evening and continuing into Sunday morning. Then we should
see more storms Sunday afternoon along the Cascades and northern
California. When storms do form Sunday, their motion will be
around 10 knots, so heavy precipitation is possible. Because of
this, we issued a flash flood watch for burn scars along the
Cascades and in Modoc county.

As for high temperatures, we'll see temperatures aloft cool slightly
into Sunday, yet warm up again Monday. So another day around 100
degrees in the valleys is possible. Since we're still in early
June and this is abnormally warm, we extended the heat advisory
for one more day, but kept it within the Rogue Valley and the
valleys in Siskiyou county.

LONG TERM...Wednesday (June 8th) through Saturday (June 11th)...The
models have come into reasonable agreement for the extended period
and show a much cooler pattern than in the short term. The whole
pattern in the extended doesn't look particularly wet as the
trajectory of the upper system is from the northwest, but it
definitely looks much cooler. A cold front will move onshore
Wednesday and knock high temperatures across the west side down
about 10-15 degrees with some showers possible. It will be a little
cooler over the east side, as well, but not as dramatically so as
the front itself looks to get hung up over the Cascades. There will
also be a chance for a thunderstorm on the east side Wednesday along
with breezy southwest winds. By Thursday, the front moves to the
east side with thunderstorms still possible over there. It will be
even cooler (at or below normal) on the west side with showery,
cool, onshore flow. Friday, the upper trough moves through with
cooler weather yet - around 5 degrees below normal. Temperatures may
rebound a little Saturday, but not much. Wright

FIRE WEATHER...Updated 210 PM PDT Sat 4 June 2016....Hot weather
continues through Tuesday. Thunderstorm chances increase tonight,
especially from the Cascades/Siskiyous eastward. Steering flow is
weak (E-SE 5-10 mph) so any storms that form will be slow moving and
capable of producing heavy rain. That steering flow may also allow a
thunderstorm out onto the west side later tonight and tomorrow
morning. Thunderstorms with heavy rain become a greater threat
tomorrow afternoon as moisture and dynamics aloft increase. Storms
are a pretty good bet in the Cascades and Siskiyous and a flash
flood watch is being issued for burn scar areas in both ranges for
Sunday afternoon and evening. A similar threat continues Monday and
Tuesday but steering flow will gradually increase lessening the
threat for flooding. -Wright

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Heat Advisory until 11 PM PDT Sunday for ORZ023-025.
     Flash Flood Watch from Sunday afternoon through Sunday evening
     for ORZ027>029.
     Heat Advisory until 8 PM PDT Monday for ORZ024-026>028.

CA...Flash Flood Watch from Sunday afternoon through Sunday evening
     for CAZ083>085.
     Heat Advisory until 8 PM PDT Monday for CAZ080-081.

Pacific Coastal Waters...Gale Watch from Monday morning through Monday evening for
     PZZ356-376.
     Small Craft Advisory from 11 AM Sunday to 11 PM PDT Monday for
     PZZ356-376.
     Small Craft Advisory for hazardous seas from 11 AM Sunday to 11
     PM PDT Monday for PZZ356.
     Small Craft Advisory from 11 AM to 11 PM PDT Monday for
     PZZ350-370.
     Small Craft Advisory for hazardous seas from 11 AM to 11 PM PDT
     Monday for PZZ350.
     Small Craft Advisory for hazardous seas until 11 AM PDT Monday
     for PZZ370-376.

NSK/TRW/JBL