AgWeatherNet Weekly Weather Outlook for September 28 to October 4, 2013

Wet and Windy This Weekend; Showery Early Next Week

Nic Loyd, Meteorologist, 509-786-9357
Gerrit Hoogenboom, Director, 509-786-9371

As an unusually strong late September jet stream focuses on Washington this weekend, several wet fronts will cross the region. The result will be a nearly continuous period of rainfall in western and mountainous areas that should persist through at least Monday morning. This storm will be much more typical of November than September. One major wildcard in this developing situation involves the interaction of the remnants of a western Pacific tropical typhoon with our mid-latitude weather. Moisture from the former tropical system is likely to be entrained into the storm track, which could further enhance rainfall rates. Several inches of rain is expected in the western lowlands, while the Olympics and Cascades will be inundated with around 5 to 8 inches. Freezing levels should remain high enough that snow will not be an issue in the mountains this weekend. It is likely that this will be one of largest rain events in recent memory to occur so early in the autumn.

Some river flooding and debris slides are possible later this weekend, and ponding of water on roadways in urban areas is very likely. Strong winds are also anticipated at most locations this weekend, including the areas that receive only light rainfall totals. There could be downed limbs as a result of the strong winds impacting the wet and still leaf-laden trees. Although some rainfall is expected everywhere this weekend, areas in the south central Washington rain shadow are unlikely to receive more than a few tenths of an inch thanks to a strong southwesterly air flow. Overall, the combination of clouds, moisture, and wind means that only small diurnal temperature swings are expected this weekend.

By early next week, the heavy rain will have ended, although rain or showers will remain likely in most areas except central Washington. While cool and unsettled conditions are expected, it is not clear if any additional organized storms will pass through Washington early next week. However, snow showers are likely in the higher elevations, as snow levels drop back down to around 6000 feet by Monday. Drier and calmer weather may return later next week, along with warmer days and cooler nights.

Temperatures
  • Mild nights this weekend, with cool days in rainy areas.
  • Cooler early next week.
  • Warmer days and cooler nights later next week.

Rainfall
  • Heavy rainfall in the west this weekend, especially in the mountains.
  • Rain likely in eastern areas this weekend, with a chance of rain in central areas.
  • Rain or showers at times early next week, especially in western areas.
  • Drier later next week.

Wind
  • Windy this weekend, with gusts to 50 mph at the coast.
  • Breezy at times next week.
  • Possibly calmer later next week.

8 to 14 Day Outlook - October 5 to October 11
  • Overall, above average temperatures and near average rainfall are expected during the 8 to 14 day time frame.

Important Points about Next Week's Weather

South Central Washington
  • Normal conditions for this time of the year would be highs in the mid to upper 70s and lows in the mid to upper 40s.
Weekend
  • A chance of rain and windy.
  • Highs in the mid 60s to mid 70s on Saturday, and mid to upper 60s on Sunday.
  • Lows in the mid 40s to 50s.
Next Week
  • Breezy. A slight chance of rain or showers at times early in the week.
  • Highs in the 60s to around 70, and then warmer by the end of the week.
  • Lows in the mid 40s to low 50s on Monday morning, and then cooler by mid week.

North Central Washington
  • Normal conditions for this time of the year would be highs in the mid 70s and lows in the upper 40s.
Weekend
  • Rain likely at times.
  • Highs in the 60s on Saturday, and upper 50s to mid 60s on Sunday.
  • Lows in the 40s to mid 50s.
Next Week
  • A chance of rain or showers at times early in the week.
  • Highs in the upper 50s to mid 60s, and then warmer by the end of the week.
  • Lows in the mid 40s to low 50s on Monday morning, and then cooler by mid week.

Eastern Washington
  • Normal conditions for this time of the year would be highs in the low 70s and lows in the low 40s.
Weekend
  • Rain at times and windy.
  • Highs in the upper 50s to 60s on Saturday, and mid 50s to mid 60s on Sunday.
  • Lows in the 40s on Saturday morning, and mid 40s to mid 50s on Sunday morning.
Next Week
  • Rain or showers likely at times through mid week.
  • Highs in the mid 50s to low 60s, and then warmer by the end of the week.
  • Lows in the mid to upper 40s on Monday morning, and then cooler by mid week.

Western Washington
  • Normal conditions for this time of the year would be highs in the upper 60s and lows in the upper 40s.
Weekend
  • Rain, heavy at times, except around Sequim, and windy.
  • Highs in the low to mid 60s on Saturday, and mid 50s to mid 60s on Sunday.
  • Lows in the 50s.
Next Week
  • Rain or showers at times through mid week.
  • Highs in the mid 50s to mid 60s early, and then warmer later in the week.
  • Lows in the low to mid 50s on Monday morning, and then cooler by mid week.

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