Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 281120
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
420 AM PDT Sun May 28 2017

.SYNOPSIS...
High pressure continues building over the Inland Northwest early
this week. There is a small chance of thunderstorms in the higher
elevations between Sunday and Tuesday. Otherwise expect dry and
warm weather, with afternoon highs in the 80s. This mild weather
will contribute to rises on rivers in the Cascades to north Idaho.
A cold front pushes in Tuesday night into Wednesday, with
additional disturbances behind it through the end of the week.
This will bring more seasonal temperatures, with the return of
rain and thunderstorm chances.


&&

.DISCUSSION...
Today through Monday: Mostly dry, warm conditions will dominate
the weather. A 500mb ridge will continue to build in over the next
day and a half. Its modest subsidence will dampen any "significant"
threat of precipitation and most clouds. However a few high
clouds may spill through from time to time. Also each afternoon
brings increased convective instability. Subtle impulses rounding
the top of the ridge and weak orographic lift will allow for some
cumulus development, particularly around the mountains. A few
showers or embedded thunderstorms will also be possible each
afternoon around the Cascade crest and northern mountains,
particularly northern ID. Winds will generally be light and
diurnally drive, though there may be some brief breezy drainage
winds early Monday near the Purcell Trench (KSZT to KCOE) and near
the higher Palouse. Temperatures will continue to trend warmer,
with highs in the 80s to low 90s today and few degrees milder
tomorrow. /J. Cote`

Tuesday and Tuesday night: One more day of relatively quiet and
warm conditions will grace the region on Tuesday with a slightly
increased chance of afternoon and evening thunderstorms on the
Cascades as an upstream trough approaches the area. High
temperatures will be about the same as Monday`s highs as the upper
ridge axis slides eastward and morning lows on Wednesday will be
mild as the surface thermal trough remains anchored over the
basin.

Wednesday and Wednesday evening: Models are coming into good
agreement that Wednesday will be the day the ridge breaks down.
As is usually the case after multiple days of warm temperatures,
this process will be accompanied by a heightened risk of thunderstorms
over the entire region...probably in the west during the morning
hours and spreading eastward across the basin and into the Idaho
Panhandle during the afternoon and evening hours. Models clearly
depict a strong short wave passage dragging along a surface cold
front which will assist dynamic support for thunderstorm
initiation and sustainment. This will also create breezy
conditions especially near the Cascades during the afternoon and
evening. It is too far out to get a good handle on how strong any
thunderstorms will be yet...but Wednesday appears to present the
best chance this week of an active regime of organized convection
over the region.

Thursday through Saturday: Model agreement deteriorates during
this return to a more progressive and seasonably cooler regime.
The ECMWF model is preferred owing to better run-to-run consistency
and depicts a series of weaker short wave disturbances through
the weekend. This augers for cooler and more seasonable temperatures
with a chance of showers and garden variety thunderstorms each
afternoon and evening...concentrated on the mountains ringing the
basin with persistent west/southwest winds and occasionally
breezy. /Fugazzi

&&

.AVIATION...
12Z TAFS: A building ridge will bring VFR conditions at TAF sites.
Look for some flat cu between about 19Z-02Z and a few high clouds.
Winds will remain light. Isold -shra and maybe a lightning strike
is possible in the afternoon near the Cascade crest, extreme NE
WA and north ID. No threat of any of this moving over TAF locations.


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        83  57  86  59  87  59 /   0   0   0   0   0   0
Coeur d`Alene  82  54  85  56  86  55 /   0   0  10   0   0  10
Pullman        81  52  83  53  85  56 /   0   0   0   0   0   0
Lewiston       87  57  89  59  90  60 /   0   0   0   0   0  10
Colville       84  55  87  56  88  56 /   0   0  10  10   0   0
Sandpoint      80  51  81  52  82  53 /  10  10  10  10   0  10
Kellogg        82  50  82  54  84  54 /  10  10  10   0  10   0
Moses Lake     89  55  92  57  93  61 /   0   0   0   0   0  10
Wenatchee      87  60  89  62  90  63 /   0   0   0  10  10  30
Omak           87  56  88  58  89  58 /   0   0  10   0   0  20

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...None.
&&

$$



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