Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 261737
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
1037 AM PDT Wed Jul 26 2017

.DISCUSSION...
Around 1,900 cloud to ground lightning strikes occurred across the
forecast area yesterday through this morning. Significant wetting
rainfall occurred at some locations, but not others. Modoc County
received the most rain in the last 24 hours, with a daily rainfall
record of 0.62" at Alturas (old record was 0.16" set in 1944), and
wetting rain at most locations.

This morning an area of showers with embedded thunderstorms has
been located from the southern Rogue Valley north to about Diamond
Lake, with most of the thunderstorm activity centered in the
Diamond Lake to Union Creek area. This activity is located on the
northeastern side of a mid-level low pressure feature that is
centered from the Cascades westward. A broader mid-level low is
located across northern California this morning, and is helping
the other low to increase convergence along and near the Cascade
crest.

This afternoon the low to the south will move eastward, while the
one on the West Side morphs into more of a trough. This is
expected to focus showers and thunderstorms activity along and
near the Cascades and Siskiyous, pushing eastward this evening.
Due to the lingering trough on the West Side, we have added
isolated thunderstorms back in for southeastern Josephine and
much of Jackson County through the afternoon. Due to developing
northwest flow this afternoon and evening, also added some
isolated thunder in the Weed and Mount Shasta areas for the early
evening. Again, fire starts and localized wetting rainfall are
expected, along with an isolated threat for severe hail and severe
gusty winds. Storm motion will still be slow, but not as slow as
yesterday, so the heavy rain threat is a bit less than it was
yesterday.

Tonight activity will kick east and out of Modoc and Lake
Counties, and then we will move into a thunderstorm free, hotter
and drier pattern for late this week through early next week. BTL


&&

.AVIATION...26/12Z TAF CYCLE...Along the coast and over the coastal
waters...a mix of IFR/LIFR conditions exist. Conditions should
improve to MVFR late morning...but near term guidance keeps these
cigs along the coast throughout the TAF period.

Away from the coast...VFR conditions will prevail throughout the TAF
period. There are some lingering showers along the Cascades this
morning that could produce some isolated lightning strikes within
the next few hours. By early afternoon...thunderstorm activity will
increase and is expected to continue into the evening hours. The
focus of activity will be similar to yesterday...from the Cascades
eastward and Siskiyous southward. West side valleys should stay
clear of thunderstorms...however, can not rule out a thunderstorm
affecting the southern end of the Rogue Valley late this afternoon.
Expect gusty outflow winds within the vicinity of any thunderstorms.
/BR-y

&&

.MARINE...Updated 230 AM PDT Wednesday 26 July 2017...Seas will
subside below small craft advisory levels north of Cape Blanco this
afternoon. However, the thermal trough will remain in place through
the remainder of the week into this weekend, and small craft
advisory conditions will likely persist south of Cape Blanco. The
thermal trough strengthens some this weekend, and gales will be
possible south of Cape Blanco with small craft advisory conditions
possibly reaching north of Cape Blanco.

&&

.FIRE WEATHER...Updated 600 AM Wednesday 26 July 2017...The upper
low over Northern California will bring one more day of scattered
thunderstorms to areas from the Siskiyous and Cascades eastward. Be
aware that gusty and erratic outflow winds can travel miles away
from storms and affect new fires that crews are attacking. Some
wetting rains are again possible today but fire starts are still
expected due to abundant lightning. Thunderstorms will continue over
the east side through this evening. The upper low will weaken some
this afternoon and push east of the area tonight, and the air mass
will stabilize tonight into Thursday. Little to no thunderstorm
activity is expected Thursday through Friday. However, attention
turns to the increasingly hot, dry, and breezy conditions following
this lightning event. These conditions will encourage sleeper fires
to show and possibly become active. East to northeast winds will
accompany poor to moderate overnight humidity recoveries Friday
night, and temperatures Saturday and Sunday will be about 10 degrees
above normal for this time of year. SK

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Red Flag Warning until 11 PM PDT this evening for ORZ624-625.
     Red Flag Warning until 11 PM PDT this evening for
     ORZ617-621-623.

CA...Red Flag Warning until 11 PM PDT this evening for
     CAZ280-281-284-285.

Pacific Coastal Waters...
- Small Craft Advisory until 11 PM PDT Friday for PZZ356-376.
- Small Craft Advisory for hazardous seas until 5 PM PDT this
  afternoon for PZZ350-356-370-376.

$$

BTL/Sven/NSK



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