[willamette-fcst] Forecast - Friday, November 13th, 2009

[Willamette Valley Ag/Burning Forecast]

Daily Smoke Management Forecast




Oregon Department of Agriculture
Smoke Management Program
Weather Outlook and Field Burning Advisory for Willamette Valley Growers and Fire Districts.

Issued: 
     Friday, November 13th, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from now until 3:00pm.
     Straw stack burning is allowed, for dry stacks, from now until 3:00pm.

Weather Discussion:
     A strong cold front, moving southeastward from the Gulf of
     Alaska, extended from near Seattle, to just east of Astoria
     and Newport, at mid-morning.  Ahead of the front, steady
     rain and blustery southerly winds had pushed inland across
     the western Washington and northwestern Oregon.  Between
     one-half and three-quarters of an inch of rain fell this
     morning along the Washington and northern Oregon coastlines,
     with between one-tenth and one-quarter of an inch falling in
     the interior of western Washington and north of about Salem
     in the Willamette Valley.  Rain was just moving into the
     south valley at mid-morning.

     The ODA surface analysis showed southerly pressure-gradients,
     ahead of the cold front, across the Willamette Valley, with a
     shift to more westerly gradients, in the wake of the front, along
     the Washington and northern Oregon coastlines.  South winds were
     gusting to about 25 mph throughout the Willamette Valley, at
     mid-morning.  Southerly winds gusted to around 40 mph along the
     northern and central coast earlier this morning but had since
     turned westerly and were beginning to decrease.

     This is a quick-hitting system, with the steady precipitation
     shutting off with the cold frontal passage. Satellite and radar
     imagery both showed a well-defined back edge to the steady
     precipitation making its way over the northern Oregon coast
     range at mid-morning.  The post-frontal break in rainfall will
     be brief, however, with cold instability showers, associated
     with an upper-level trough, already making their way onshore.

     ODOT road cameras showed snow had moved into the Cascades
     with snow-packed passes and temperatures in the 20s.  The
     steady rain and mountain snow will end over the next couple
     of hours, front northwest to southeast, across western
     Oregon.  Gusty southerly winds will turn westerly and back
     off just a bit by midday.  Showers will mix with snow in the
     higher foothills of the Cascades, with cold air aloft
     dropping the snow level from about 2500 feet to around 1500
     feet.  Valley highs will struggle into the upper 40s, even
     with a few sunbreaks.

Surface Winds:
     S 10-20 G25 this morning, WNW 10-20 G25 this afternoon.
Transport Winds:
     S 25 this morning, WNW 25 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 4000 feet.  Ventilation index 100.
High Temperature:
     Salem\'s high temperature today will be near 49.
Humidities:
     Minimum relative humidity will be near 56%.
Sunrise/Sunset:
     Salem sunset tonight: 4:45pm; sunrise tomorrow: 7:09am.

Extended Outlook:
     Showers will taper off this evening, as the upper-level
     trough slides east of the Cascades.  Cooling surface
     temperatures will also help to stabilize the air mass.  Partial
     clearing and cold air aloft may allow valley temperatures to
     locally drop below the freezing mark, with areas of fog
     forming.  That will make for tricky travel overnight, with
     wet road surfaces possibly becoming icy, in places.  Use caution,
     if you plan to be out driving tonight or early Saturday morning. 

     Some sunbreaks are possible Saturday, with a warm front
     forecast to increase clouds across northwestern Oregon by
     Saturday evening.  Rain is likely across western Washington
     and northwestern Oregon by Sunday morning, with not much
     rain south of about Eugene.  The snow level will rise
     sharply Sunday, to 6-7000 feet, in the Oregon Cascades.  The
     warm front is forecast to push north of the region by Sunday
     night with rain tapering off. Temperatures should be quite
     mild Monday and Tuesday, ahead of a cold front forecast to
     come onshore Tuesday evening.  More valley rain and mountain
     snow is forecast for the second half of next week.

Sat (14 Nov):  Areas of AM Fog. Increasing Clouds.  Snow Level Rising to 5000 Feet.  32/48

Sun (15 Nov):  Light Rain...Mainly North.  Snow Level Rising to 6-7000 Feet.  37/53

Mon (16 Nov):  Mostly Cloudy and Mild.  43/57

Tue (17 Nov):  Increasing Clouds.  Rain Developing by Evening.  44/54

Wed (18 Nov):  Rain Turning to Showers.  Snow Level Dropping to 3000 Feet.  42/49

Thu (19 Nov):  Rain and Windy.  Mountain Snow.  Snow Level 3-4000 Feet.  39/49

Fri (20 Nov):  Showers.  Snow Level 3000 Feet.  39/49

ODA Meteorologist
weather at oda.state.or.us