Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus66 kotx 262330 
afdotx

Area forecast discussion
National Weather Service Spokane Washington
430 PM PDT Fri may 26 2017

Synopsis...
high pressure builds over the region this weekend. A few showers
and isolated thunderstorms are possible around the Idaho Panhandle
this afternoon and evening. Limited thunderstorm chances develop
around the Cascades, and perhaps the Canadian border, each
afternoon between Sunday and Tuesday. Otherwise expect dry, warm
weather into early next week, with afternoon highs in the 80s.
This mild weather will contribute to rises on rivers in central
and north central Washington. A threat of unsettled weather
returns in the middle to late next week, with slightly cooler
temperatures.

&&

Discussion...

Tonight and tomorrow: the northerly flow allowing weak disturbances
to fire off very light and spotty convection over portions of north
Idaho this afternoon and early evening gets shunted to the east
tonight as an upper level ridge of high pressure amplifies over
eastern Washington and north Idaho while the ridge axis migrates
from near the coast today to over the Cascades tomorrow. This will
result in a warming and drying trend with forecast temperatures
above normal for this time of year, especially daytime highs
tomorrow. Surface winds are expected to remain fairly diurnal
upslope to upvalley during the day transitioning to downslope and
downvalley winds overnight. /Pelatti

Sunday through tuesday: the Two Points of interest in the extended
period are the unseasonably warm temperatures and the eventual
return of shower and thunderstorm chances to the region. On Sunday
we're squarely under a stabilizing ridge of high pressure that
will hang around through at least the Memorial Day weekend. This
is great news to those that are used to our typically cooler
holidays in years past. We will be clear and dry with temperatures
on the increase each day through Tuesday as the ridge axis
approaches and 850 mb temps reach near 19c. High temperatures will
be 10-15 degrees above average for late may, with highs in the
mid 80s and even the 90s in parts of the deep Columbia Basin. This
warming will lead to increased mountain snow melt and rises on
area river and streams over the next few days. Keep in mind that
water temperatures are still quite cold given this snowmelt.

While the ridge will be the dominating player, some scattered mountain
showers will be possible rounding the ridge each afternoon/evening
beginning on Sunday and increasing in coverage each afternoon.
Flow becomes southwest on Sunday, advecting more moisture over
central Washington at the mid levels. This, together with orographic lift
will be able to initiate some mountain showers. Warm temps and
increasing lapse rates will give enough instability over the
mountains for some weak thunderstorm potential as well. Coverage
increases over the mountains on Monday afternoon and even more so
late Tuesday.

Tuesday night through friday: models begin to diverge on exactly
when the ridge will break down. While the GFS has been the most
bullish in bringing a trough in late Tuesday/Wednesday, the ec and
Canadian models are beginning to come into agreement with this
earlier timing. This means we'll see a bit of a cool down and a
good chance for showers and thunderstorms on Wednesday and
Thursday as the negatively tilted trough moves through. Behind the
trough flow becomes more zonal with a few ripples in the flow
capable of bringing hit and miss showers on Friday. /Bw

&&

Aviation...
00z tafs: showers and isolated thunderstorms over the southern to
central Idaho Panhandle will dissipate quickly this evening. A
strong ridge of high pressure will build further into the region
on Saturday. Flat cumulus will be possible over the higher terrain
Saturday afternoon; otherwise, VFR conditions and weak winds will
continue across the region through 00z Sunday. /Svh

&&

Preliminary point temps/pops...
Spokane 51 79 54 82 56 85 / 0 0 0 0 0 0
Coeur D'Alene 47 78 49 82 51 84 / 0 0 0 0 0 0
Pullman 47 76 47 80 50 82 / 0 0 0 0 0 0
Lewiston 51 84 53 87 57 89 / 0 0 0 0 0 0
Colville 49 82 52 84 52 87 / 0 0 0 0 0 10
Sandpoint 44 77 46 79 48 81 / 0 0 0 10 10 10
Kellogg 44 77 47 79 48 81 / 10 0 10 10 10 10
Moses Lake 51 86 52 89 55 91 / 0 0 0 0 0 0
Wenatchee 55 86 57 88 59 89 / 0 0 0 0 0 0
Omak 52 85 52 87 54 87 / 0 0 0 0 0 10

&&

Otx watches/warnings/advisories...

National Weather Service Glossary of Abbreviations