[willamette-fcst] Willamette Valley Ag Weather Forecast

[Willamette Valley Ag/Burning Forecast]

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

Issued:
      Wednesday, May 20th, 2009 at 9:00am.

Burn Advisory:
      Agricultural burning is allowed.  Suggested burn 
times are from now until 6:30pm.
      Stack burning is not allowed.

Weather Discussion:
      A sharp cold front swept across Oregon Monday night 
and
      Tuesday, followed by a cold upper-level trough.  The
      combination of the cold front and subsequent 
upper-level
      trough dropped up to one-half inch of rain along the 
extreme
      north coast and from about Salem north in the 
Willamette
      Valley.  Rainfall amounts rapidly tapered off to the 
south
      with the southern Willamette Valley only picking up 
about
      one-tenth of an inch.  Much of southwestern Oregon 
only
      received trace amounts of rain. Precipitation was 
scattered
      and light east of the Cascades.  However, Meacham, 
in the Blue Mountains
      of northeastern Oregon, picked up about one-quarter 
of an inch of rain.

      The cold front ushered much cooler marine air into 
the state
      Tuesday.  Willamette Valley high temperatures only 
managed
      to climb into the upper 50s and low 60s, after 
peaking in
      the upper 70s and low 80s Monday.  In southwestern 
Oregon,
      Medford only hit 70 Tuesday, after a high Monday of 
91
      degrees.  The cooling was accompanied by brisk 
onshore
      winds...especially east of the Cascades.  Rome, in
      southeastern Oregon, had wind gusts to 49 mph 
Tuesday
      afternoon, as the cold front pushed towards the 
Idaho
      border.  Pendleton had gusts to 38 mph Tuesday. 
 Burns and
      Baker City had gusts to 35 mph.  Redmond recorded a 
gust of
      32 mph.  Westerly winds gusted to between 20 and 25 
mph
      Tuesday in the Willamette Valley.

      The ODA surface analysis this morning showed the 
cold front
      had moved east of Oregon and into the Rockies.  With 
high
      pressure centers over the northern Willamette Valley 
and
      northeastern Oregon, onshore pressure gradients were 
turning
      northerly across the state.  Winds were still 
blustery east
      of the Cascades with gusts between 15 and 25 mph 
common.
      Winds were light in the Willamette Valley early this 
morning
      and were becoming increasingly northerly at 
mid-morning.

      Satellite imagery showed mostly clear skies over 
Oregon this
      morning, except for some residual low clouds over 
mainly
      northwestern Oregon.  Doppler radar showed a few 
dying
      sprinkles over the extrme northwest corner of the
      state...extending inland to around Portland. 
 Clearing skies
      overnight allowed some Willamette Valley locations 
to drop
      well into the 30s.  Eugene dipped to 33 degrees 
early this
      morning, just missing the record low of 32 degrees, 
set way
      back in 1913.  Corvallis dropped to 36 degrees and
      McMinnville hit 35.  Redmond was the cool spot in 
the state
      this mornig with a minimum of 25 degrees. 
 Mid-morning
      temperatures were mostly in the 40s and low 50s 
across the state.

      A weak upper-level ridge is forecast to move onshore 
today
      with a drier northwesterly flow aloft spreading from 
west to
      east across the state.  Surface winds will turn 
northerly
      and could become rather blustery this afternoon, 
especially
      in the southern Willamette Valley and along the 
central and
      southern coast.  Mostly sunny skies and warming 
aloft will
      help temperatures recover to near-normal this 
afternoon.

Surface Winds:
      N 5-12 this morning, N 10-15 G20 from Salem south 
this afternoon.
Transport Winds:
      NNE 8 this morning, NNE 14 this afternoon.
Atmospheric Ventilation Conditions:
      Maximum mixing height today will be near 4500 feet. 
 Ventilation index 63.
High Temperature:
      Salem's high temperature today will be near 67.
Humidities:
      Minimum relative humidity will be near 38%.
Sunrise/Sunset:
      Salem sunset tonight: 8:40pm; sunrise tomorrow: 
5:37am.

Extended Outlook:
      The transitory flat ridge of high pressure that is 
moving onshore
      today is forecast to shift east of the Cascades by 
Thursday afternoon,
      with the flow aloft turning more westerly.  That 
will induce a weak
      surge of cooler ocean air into the Willamette Valley 
Thursday night
      and Friday.  A very weak upper-level trough is 
forecast to move over
      Oregon Friday, with continued onshore flow but 
little to no rainfall.

      The flow aloft is forecast to turn northwesterly and 
dry out
      again Satruday.  An upper-level ridge is forecast to 
build
      over the Rockies early next week, with increasing 
southerly flow aloft
      over Oregon.  That will warm temperatures and also 
bring some moisture
      northward into the state for a chance of mainly 
mountain thunderstorms.
      The upper-level flow is forecast to turn more 
southwesterly by midweek,
      with increasing onshore flow at the surface.

Tomorrow (21 May):  Mostly Sunny.  39/74

Fri (22 May):  Partly Cloudy.  Slightly Cooler.  43/72

Sat (23 May):  Morning Clouds...Becoming Mostly Sunny. 
 46/74

Sun (24 May):  Mostly Sunny and Warmer.  46/78

Mon (25 May):  Mostly Sunny and Warmer.  47/82

Tue (26 May):  Partly Cloudy and Warm.  Slight Chance of 
T-Storms.  50/80

Wed (27 May):  Partly Cloudy and Slightly Cooler.  49/75

ODA Meteorologist
weather at oda.state.or.us