Oregon Climate Service, April 2003

Overview

For the second month in a row, Oregon "enjoyed" a very wet month, with an unusually large number of rainy days. In many locations, the March-April period set records for most wet days (see report later in this Summary).

Table 1 is a summary of monthly averages and totals at selected stations throughout the state. Table 2 lists daily temperatures and precipitation for most of the locations listed in Table 1. In Table 3, monthly and seasonal precipitation totals throughout the state are listed. Figure 1 shows the percentage of normal precipitation for the Water Year.

Basin Summary

Here is a summary of precipitation, water supply, and snow pack as of the end of the month, by river basin:

Precipitation

Snow

Stream Flow

 SWSI
BASIN

(1)

(2)

(3)

(4)

 (5)

(6)

(7)
OWYHEE 163 87 85 55 15 20 -1.2
MALHEUR 141 87 94 82 1 13 -1.5
GRAND RONDE, POWDER, BURNT 207 120 95 83 102 101 -0.6
UMATILLA, WALLA WALLA, WILLOW 125 107 95 71 107 108 -0.3
UPPER JOHN DAY 157 105 90 54 86 70 +0.5
UPPER DESCHUTES, CROOKED 136 88 85 72 74 66 -0.2
LOWER DESCHUTES, HOOD RIVER 141 103 85 73 84 75 +0.2
WILLAMETTE 159 104 85 69 153 87 +1.6
ROGUE, UMPQUA 191 112 96 95 137 91 +1.0
KLAMATH 193 96 89 98 72 71 -0.7
LAKE COUNTY, GOOSE LAKE 140 100 109 92 73 63 +0.2
HARNEY 177 92 88 62 65 53 -0.5
NORTH COAST 128 96 n.a. n.a. 110 93 +0.6
SOUTH COAST 198 102 n.a. n.a. 166 108 +1.6

n.a. Not available

(1) Percent of normal April precipitation, from NOAA Cooperative sites
(2) Percent of normal seasonal precipitation (since Oct. 1), from NOAA Cooperative sites
(3) Percent of normal seasonal precipitation, from Natural Resources Conservation Service (NRCS) SNOTEL sites
(4) Percent of normal snow water equivalent, from NRCS SNOTEL sites
(5) Percent of normal April stream flow, from U.S. Geological Survey (USGS)
(6) Percent of normal seasonal stream flow (since Oct. 1), from USGS
(7) Surface Water Supply Index, from NRCS (-4 = very dry, 0 = normal, +4 = very wet)

Forecast

The Climate Prediction Center (CPC) predicts above-average temperatures and above-average precipitation for May; for the three-month period ending in July, there is a likelihood of above-average precipitation and average temperatures. Oregon Climate Service predicts average temperatures and above-average precipitation for May as well as for the three months.

La Niña conditions appear to be developing in the Pacific. Stay tuned for news in the next several months.

Wettest Spring Ever?

George Taylor and Kelly Jenson
Oregon Climate Service
May, 2003

Sometimes at this time of year it seems like spring will never end. Climatically speaking, spring in Oregon is "long and drawn out." It begins, according to our definition, in late February, when the probability of precipitation begins to fall. In many years, the first dry, sunny weather occurs at that time. Spring continues through March, with average rainfall dropping significantly between March and April (an average April is only about 60% as wet as an average March), although the number of wet days stays about the same. May and June are progressively drier, with fewer wet days.

Here are 30-year averages (1971-2000) for monthly precipitation and number of wet days (.01 inch or more) for the spring for various Oregon stations:

Station February March April May June
Portland 4.18 3.71 2.64 2.38 1.59
Astoria 7.87 7.37 4.93 3.28 2.57
Salem 5.09 4.17 2.76 2.13 1.45
Corvallis 5.71 4.59 2.98 2.3 1.46
Medford 2.1 1.85 1.31 1.21 0.68
Pendleton 1.22 1.26 1.13 1.22 0.78
Bend 1.13 0.92 0.7 0.9 0.75
Crater Lake 8.47 7.79 5.34 3.5 2.03
North Bend 8.12 7.94 5.19 3.4 1.72
La Grande 1.32 1.5 1.58 1.9 1.53
Hood River 4.36 2.88 1.81 1.08 0.79
Lakeview 1.69 1.7 1.3 1.46 0.99

Average number of wet days (.01 inch or more)

Station February March April May June
Portland 16 17 15 13 9
Astoria 19 21 18 16 13
Salem 16 17 14 11 8
Corvallis 18 19 16 13 8
Medford 12 12 10 8 5
Pendleton 11 11 9 8 6
Bend 9 7 7 6 5
Crater Lake 17 19 15 11 7
North Bend 18 20 17 13 10
La Grande 9 12 10 10 9
Hood River 16 15 13 9 6
Lakeview 11 11 10 9 6

 

Total precipitation, averages, and records for March and April appear below.

Total March-April Precipitation (inches)
Station 2003 Record Year
Portland 9.48 10.87 1997
Astoria 18.69 21.93 1997
Salem 9.59 13.21 1928
Corvallis 13.65 12.72 1916
Medford 5.56 6.36 1989
Pendleton 2.7 4.21 1995
Bend 1.23 3.52 1989
Crater Lake 16.74 20.82 1989
North Bend 20.07 25 1995
La Grande 4.99 5.68 1995
Hood River 8.57 12.34 1916
Lakeview 3.54 5.75 1995

Days with Measurable Precipitation

Station 2003 Record Year
Portland 46 41 1955, 1997
Astoria 48 47 1955
Salem 47 48 1937
Corvallis 52 46 1993
Medford 33 37 1995
Pendleton 21 30 1961, 1993
Bend 20 25 1957
Crater Lake 40 46 1967
North Bend 53 49 1984
La Grande 27 31 1974
Hood River 28 45 1993
Lakeview 27 35 1983




Oregon Climate Service

George H. Taylor, Oregon State Climatologist

Wayne P. Gibson, Programmer/GIS mngr.

Mandy Matzke, Research Assistant/Manager of Data Services

Kelly Jenson, Undergraduate Assistant

Melanie Mitchell, Student Assistant

Sandra Terra, Undergraduate Assistant



Oregon Climate Service, Strand 316,                                 Phone: (541) 737-5705  
Oregon State University                                                      Fax: (541) 737-5710   
Corvallis, Oregon  97331                                                     E-mail: oregon@oce.orst.edu   
                                                                             Web: http://www.ocs.oregonstate.edu