322
FXUS66 KPQR 141737 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
1037 AM PDT Fri Jun 14 2024

Updated Aviation Discussion

.SYNOPSIS...A bit cooler today, as weakening front arrives. Unsettled
weather for the weekend, with onshore flow, clouds and even showers.
High pressure rebuilds offshore early next week, with dry and mild
weather returning towards middle of next week.

Key Messages...

-  Cooler, with increasing clouds today. Chance of showers
   along the coast (Tillamook northward) and west Washington.

-  Showers Saturday through Monday. A small chance (15-25%)
   of afternoon/evening thunderstorms on Sat and maybe Sun.

-  High pressure builds next week, bringing dry and warm
   conditions back to the region later next week.

&&

.SHORT TERM...Now through Sunday...Today is a transition day, with
increasing onshore flow. This will result in cooler temperatures
today, along with breezy westerly winds over the high terrain, as
well as through the Columbia Gorge. A weak front offshore push
onshore today, but not much in way of any precipitation, aside from a
few showers along the coast.

Broad upper trough offshore and over the Gulf of Alaska will push
into  the Pac NW Fri night and Sat. As such, will see bit cooler air
aloft, with showers increasing. But, overall, precipitation amounts
not all that impressive, with most areas getting 0.10 inch or less.
Given potential of breaks in the clouds on Sat, could see a few
`beefier` showers, with potential of bit more rain. Add to that, may
get enough instability to support a few thunderstorms. Will maintain
current forecasts, with little change.

More clouds around the region on Sat, than to continued moderate to
strong onshore flow. Still, will maintain high chance of showers as
upper level disturbance in the westerly flow shifts inland and over
the inland Pac NW. Will keep small (15-25%) chance of thunderstorms,
but bit question will be whether or not will get enough breaks in
the clouds to boost low level warming, and hence any steepening of
lapse rates. With more warming, better the chance of a few
thunderstorms, while less sun breaks and thus less warming, the
lower the potential for thunderstorms. Based on current trends, any
thunderstorms likely to remain rather isolated at best on Sat.
Showers decreasing Sat night.

Sunday remains to be challenging forecast. Some models still have
somewhat unstable air mass over the region, supporting showers. But,
more recent runs of GFS and NAM models indicate decent potential of
showers, given upper trough shifting overhead. But, does seem this
potential decreasing through the day, given main upper support is
swinging east of the Cascades. WIll make no big changes in forecasts,
but if trends continue, Sunday could be more dry than current
expected. But, still plenty of clouds and coolish.

.LONG TERM...(Monday through Thursday)...Still have upper trough over
the region on Monday, with continued showers. By Tuesday, most models
(GFS, UKMET and ECMWF) show upper trough shifting well east of the
Cascades. So, shower potential will end in the afternoon for most all
areas except the Cascades. High pressure offshore will build again
for middle of next week, bringing return of dry weather. Overall air
mass will gradually warm again, with return of bit warmer than normal
temperatures. Will trend to 60s along the coast, and 70s inland.

&&

.AVIATION...VFR conditions continue for most locations across the
airspace. However, a series of fronts are expected to impact the
region. The first front will be relatively weak and will slowly
move eastward across the airspace today. Expect MVFR conditions
for KAST starting around 18Z Friday and those MVFR conditions
slowly spreading southward and will likely reach KONP around 22Z
Friday. There will also be a 15%-25% probability for IFR
conditions to develop starting between 18Z-22Z Friday along the
coast. The coast is expected to maintain the MVFR/IFR conditions
through at least 18Z Saturday as the second stronger front will
start to move across the airspace around 06Z Saturday. These
fronts will bring showers and a slight chance of thunderstorms
(25% probability) for KAST starting around 06Z Saturday, then
spreading southward and reaching KONP around 14Z Saturday.

The first front reaches northern, inland locations around 20Z
Friday and will result in a mixture of low-end VFR/high-end MVFR
conditions with cigs likely oscillating between FL030 and FL040
for areas north of KMMV/KUAO along with light showers. Areas
south will likely maintain VFR conditions with FL040 or greater
with no precipitation expected. The second, stronger system will
impact inland locations starting around 06Z-09Z Saturday and will
likely maintain the low-end VFR/high-end MVFR mixture along with
widespread showers. This second front will also result in a slight
chance of thunderstorms (25% probability) for areas north of KCVO
starting around 15Z Saturday.

Any thunderstorms will have the potential to produce small hail
along with gusty and erratic winds.

Southerly winds across the airspace will become more westerly
after the first frontal passage.

PDX AND APPROACHES...VFR under clear skies will transition to  a
mixture of low-end VFR/high-end MVFR conditions with cigs likely
oscillating between FL030 and FL040 as a series of fronts move
eastward through 18Z Saturday. Look for this transition to start
around 00Z Saturday as the first, weaker front crosses the
terminal. This first front will also bring light showers. Second,
stronger front will maintain oscillating FLs and also result in a
slight chance of thunderstorms (25% probability) starting around
15Z Saturday. /42

&&

.MARINE...Small Craft Advisory has ended for all waters, and winds
are currently near zero. Seas are currently around 5-7 ft at 11
seconds, and swells should not change much over the next few days.
A weak front will bring some slightly stronger southerly winds
Friday morning, and will be followed by a stronger front around
midnight Friday night. This marks a return to relatively
stronger, westerly winds across all waters. Seas will be slightly
elevated Saturday due to this front, rising to 5 to 7 ft on
Sunday, before subsiding again towards 4 to 6 ft by the start of
the upcoming week. /42/JLiu

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...None.

&&

$$

www.weather.gov/portland

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