Tip:
Highlight text to annotate it
X
This is the weekly weather briefing for September 3rd, 2013. My name is Andy Brown.
I am the Warning Coordination Meteorologist for the National Weather Service Forecast Office
in Spokane, Washington. As always, forecasts are subject to change so please check our
website periodically this week for the most updated forecast.
This week’s weather is going to feature the chance of thunderstorms today through
Wednesday afternoon. Beginning Wednesday night, the area will see a widespread rain and
thunderstorm event with the potential for flash flooding and even severe weather. By
Friday, we’ll see cool and wet conditions before the weekend brings us a warming and drying
trend.
The overall pattern today through Wednesday is being driven by a large area of low
pressure off of the Washington coast. Scattered thunderstorms will be the main threat with a
slight chance of small hail and gusty winds with any thunderstorms that develop.
Here are a few more specifics on the expected weather today through Wednesday afternoon.
Scattered thunderstorms will continue to develop this afternoon with the greatest
threat being over the mountains. Thunderstorms could re-develop overnight toward the
Cascades and move north toward the Okanogan valley. With these thunderstorms we expect a slight
chance of small hail, localized gusty winds, and brief heavy rain. Because of the isolated
to scattered nature of these storms as well as the quick movement, the threat of flash
flooding is minimal through Wednesday afternoon.
Wednesday night, the low pressure that was off the coast begins to move inland. This
will bring widespread thunderstorms and the potential for heavy rain to the Inland
Northwest. With this round of thunderstorms, we will have an increased risk of hail, strong
winds, and a greater potential of flash flooding. It’s important to note that the
threat of flash flooding will not just be for the burn scar areas that we frequently are
talking about. Instead, most areas across the inland northwest should see at least
half an inch of rain so urban flooding is certainly a possibility Wed night through
Thursday afternoon.
Here are the specifics for this time frame that I just mentioned. Most areas will see
the impacts Wednesday night but showers and thunderstorms will continue through the day
Thursday. Again, the potential for severe weather includes hail and strong/gusty winds but
the threat of flash flooding is also a concern.
The Weather Prediction Center which is a part of the National Weather Service put this
graphic out this morning illustrating where there is the potential for the heaviest rain
over the next 48 hours with most of that coming Wednesday night through Thursday. As you
can see, most areas will receive at least half an inch with a 48 hour total of 2
inches a distinct possibility.
Friday, the focus turns from high impact weather to cool and cloudy conditions. The low
that was crossing the Washington coast earlier in the week will now be centered over
the Inland Northwest on Friday. This will bring widespread clouds and cool temperatures;
in most places at least 10 degrees below normal for this time of year. With the low
centered over us, we can’t rule out lingering showers during the day but the greatest risk
will be over the mountains.
By the weekend, the Inland Northwest will begin to dry out and warm up. Temperatures will
begin to rebound to normal to above normal by the end of the weekend. Only a few showers are
possible and those will be mainly over the mountains.
I picked a few spots to highlight the expected weather this week. This is the forecast
summary for Spokane. You can see warm temperatures and a very high likelihood of rain
through mid week with temperatures dropping well below normal by Friday. Then
the chance of precipitation is minimal over the weekend as temperatures rebound to near
normal.
Likewise here is the week long summary for Wenatchee. It shows a similar picture with
high chances of precipitation through Thursday…then temperatures slowly rebounding
over the weekend.
Taking a look at the extended forecast from the Climate Prediction Center shows that
warming trend continuing beyond the weekend. This is the outlook for September
10th-16th. The image on the left indicates that most of the Inland Northwest will remain
below normal precipitation (or dry) while the image on the right shows a high likelihood
of temperatures above average for this time of year.
Here is the summary of impacts we are expecting through this weekend. The greatest threat
for significant weather is Wednesday night through Thursday with the potential for
widespread thunderstorms including hail, gusty winds, heavy rain, and localized
flooding. Cool and cloudy on Friday and then a return to warm and dry weather late in
the weekend.
Here is how you can stay informed and get the latest information from the National
Weather Service. Go to our website weather.gov/spokane or follow us on Facebook, twitter,
and youtube. As always, our forecasts are available 24 hours a day on NOAA Weather
Radio. Thank you for tuning in to this Weekly Weather Briefing.