Area forecast discussion
National Weather Service Portland or
320 am PDT Wednesday may 22 2013
Synopsis...a cold upper low will remain anchored over the
Pacific northwest for the remainder of the week...keeping a cool showery
weather pattern in place for the next few days. The low will weaken
over the weekend...reducing the chances for showers...and allowing
temperatures to warm back closer to normal.
&&
Short term...an upper level low with a couple of shortwaves
pin-Wheeling around it will drive the weather through Friday. The
weather pattern will be fairly persistent with showers and unseasonal
cool temperatures being the dominant features. The showers will
become enhanced this afternoon...especially over the mountains and
may have periodic short bursts of locally heavy rain. Models hint of
weak instability across the region each day but think the best chance
for thunderstorms remains outside of the Portland forecast area.
Snow levels will remain around 3 kft today..then gradually rise
Thursday and Friday. Snow levels should rise above pass level on
Friday. Expect an additional 1 to 3 inches of snow above 3000 feet
today.
Long term...the low will weaken on Friday but linger around over the
area through the weekend. Models are trying to bring a shortwave
ridge over the area briefly on Monday...but moist onshore flow will
prevent total drying. Another storm is expected early next week...Monday
night or Tuesday.
&&
Aviation...mostly VFR conditions currently with scattered shower
activity across the region this morning. Expect shower activity to
increase after 12z...with periods of MVFR ceilings at times during
heavier showers. A disturbance embedded in the large scale upper
level low will bring steadier rain during the late morning and
afternoon hours. Expect more widespread MVFR conditions from
roughly 18z through 00z. Then the trend will be toward VFR this
evening as shower activity diminishes.
Kpdx and approaches...mainly VFR in scattered showers. A brief
period of MVFR ceilings possibly later this morning in any heavier
showers...mainly after 12z. Predominant MVFR conditions more
likely from 18z to 00z as showers become steadier. Trend will be
toward VFR during the late afternoon/evening as showers diminish.
Pyle
&&
Marine...west to northwest winds of 15 to 20 knots with periods of gusts to 25
knots to continue through Wednesday. The forecast models indicate the strongest
gradient will be confined to the outer waters...with less wind
near shore. Decided to drop the Small Craft Advisory for the
inner waters. Winds will decrease late Wednesday and the trend will be
toward more benign weather late this week into next weekend as the
upper low weakens and higher surface pressure builds into the
waters.
Increased the forecast seas by a couple feet this morning as the forecast
models have been running a bit too low compared to observations
overnight. Expect seas should generally hover in the 11 to 14 feet
range through Wednesday. Seas will begin to gradually subside
Thursday...dropping below 10 feet by midday Thursday. Seas will continue to
gradually subside...reaching 5 feet or lower over the weekend. Pyle
&&
Pqr watches/warnings/advisories...
or...none.
Washington...none.
Pz...Small Craft Advisory for winds until 5 PM PDT this afternoon for
Waters from Cape Shoalwater Washington to Cascade Head or from 10
to 60 nm-waters from Cascade Head to Florence or from 10 to
60 nm.
Small Craft Advisory for hazardous seas until 5 PM PDT this
afternoon for coastal waters from Cape Shoalwater Washington to Florence
or out 60 nm.
Small Craft Advisory for rough Columbia River bar until 5 PM PDT
this afternoon.
&&
$$
More weather information online at...
http://weather.Gov/Portland
This discussion is for northwest Oregon and southwest Washington from
the Cascade crest to 60 nautical miles offshore. The area is commonly
referred to as the forecast area.
