Area Forecast Discussion
Issued by NWS Spokane, WA

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44
000
FXUS66 KOTX 251143
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
443 AM PDT Sun Jun 25 2017

.SYNOPSIS...
Temperatures will be much above average today and tomorrow with
afternoon temperatures well into the 90s. The arrival of a cold
front Monday evening will bring the potential for widely scattered
showers and thunderstorms to the Idaho Panhandle and eastern third
of Washington. Some thunderstorms may produce gusty winds Monday
afternoon and evening. Winds will be breezy Tuesday and Wednesday
as temperatures fall back into the 80s.

&&

.DISCUSSION...

...T-storms with gusty winds possible late Monday afternoon and evening...

Today through Monday night: The upper-level ridge will traverse from
the coast to Northern Rockies today delivering another warm and
dry day across the Inland Northwest. Temperatures warm into the
90s for most locations while the southwestern Columbia Basin
climbs into the low 100s. Winds will be light from the
east/southeast. Skies will start off clear with a few midlevel
clouds arriving by the afternoon. This will keep the UV index near
10 and those with outdoor plans are urged to take precautions to
protect exposed skin from sunburn.

The weather will become more active Sunday night and Monday as the
ridge axis slides east opening the region to southwest flow. A
batch of moisture can be traced on this morning`s water vapor over
N California ahead of shortwave off the coast. This moisture will
begin to drift into the Northwest Sunday night and Monday
allowing the atmosphere to begin moistening. There is little to no
evidence of an accompanying shortwave through Monday morning and
forecast continues to lean toward an increase in cloud cover with
spotty sprinkles through midday with cloud decks remaining around
15,000 ft or higher.

Shortwave energy associated the low off the CA Coast and a second
wave dropping in from the north will come into play Monday
afternoon and evening delivering the best chance for showers and
thunderstorms. There will be plenty of instability setting up
across the eastern third of WA and N ID for thunderstorms but with
a moderate amount of CIN, the best chances will focus where the
forcing is. The shortwave off the CA Coast will track through NE
Oregon and into NC Idaho bringing a chance for t-storms into the
Blue Mtns, Camas Prairie, and possibly as far north as the LC-
Valley, Palouse, into southern Shoshone County. A probabilistic
forecast would favor locations south of Lewiston but uncertainty
does exist. These storms will have the potential to be strong or
locally severe with strong wind gusts and small hail as the main
threats.

Lift associated with the northern branch shortwave will bring a
secondary area of t-storm activity with this focusing over far NE
WA and N ID. This will also need to be monitored for gusty winds
given the inverted V boundary layer profiles. Overall, the
forecast is not a slam dunk in regards to where t-storms develop
Monday afternoon and evening with this evening`s models spreading
enough instability west into the Okanogan Highlands and Central
Columbia Basin to add more uncertainty and likelihood for
additional changes as this event unfolds. There are even NAM runs
that bring clusters of storms along the US395 corridor from
Ritzville to Deer Park so stay tuned.

Monday will be warm with afternoon highs similar to Sunday.  The
air mass will actually warm a degree or two but with some
cloudiness expected, opted to stick close to Sunday`s readings. It
may even feel muggy in comparison to the last few days dryness
levels. South/southeast winds through midday will switch to the
southwest...becoming gusty through the Cascade Gaps and into the
Columbia Basin late afternoon and evening. The combination of
gusty winds and dry conditions will lead to an elevated risk for
rapid fire spreads through the grasses and sage brush. /sb

Tuesday and Wednesday: Temperatures will fall back closer to
average Tue and Wed as a broad 500mb trough sets up over the
Canadian Prairies. Onshore flow will establish a west to east
surface pressure gradient across the Cascades. This gradient will
likely produce 10 to 20 mph winds in the lee of the Cascades into
the Columbia Basin, Palouse, and West Plains. At this time,
neither the GFS or NAM carry much momentum aloft Tue or Wed with
850mb winds generally in the 10 to 20kt range. Given the slow
moving nature of the upper trough in Canada and the less than
impressive 850mb wind speeds, it is tough to get overly excited
about the gusts. Early evening gusts to 25 mph through the Cascade
gaps will likely be our strongest winds Tue and Wed in places like
Wenatchee, Chelan, Vantage, and Waterville. A 20 percent chance of
showers has been retained for the mountains of the Idaho Panhandle
Wed with a weak shortwave pivoting southeastward out of BC.

Thursday and Friday: Temperatures have been raised into the mid to
upper 80s for Thu and Fri. There is good agreement between the
GFS, ECMWF, and Canadian models that a shortwave ridge will
migrate over the Pacific Northwest Thu and Fri. We may see
redevelopment of breezy west winds in the lee of the Cascades
Friday evening. The evening runs of the GFS and ECMWF push a
shortwave trough into western WA Fri evening suggesting a push of
cooler marine air. This pattern often produces gusts in the 20 to
30 mph range for Wenatchee, Waterville Plateau, and Vantage area.

Saturday and Sunday: A familiar pattern is forecast to return for
the weekend. The GFS, Canadian, and ECMWF once again prog a
robust upper low over the Gulf of Alaska with a vigorous west to
east jet across the eastern Pacific into our region. Look for
temperatures to slide back into the upper 70s and low 80s. The
relatively fast flow aloft will likely produce breezy conditions
and possibly some showers over the mountains next weekend. /GKoch

&&

.AVIATION...
12Z TAFS: High pressure will keep VFR conditions at TAF sites
through the next 24 hours. Thin cirrus will approach the area from
the west this afternoon. /sb


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        93  66  93  60  82  55 /   0   0  20  20   0   0
Coeur d`Alene  91  60  90  57  81  52 /   0   0  20  20  10   0
Pullman        90  63  90  58  79  52 /   0   0  20  30  10   0
Lewiston       97  66  97  63  87  57 /   0   0  20  40  10   0
Colville       93  58  92  54  86  51 /   0   0  20  10   0  10
Sandpoint      87  56  88  55  81  47 /   0   0  20  20  10   0
Kellogg        90  60  89  57  77  50 /   0   0  20  40  10   0
Moses Lake     99  64  97  59  89  54 /   0   0  20  10   0   0
Wenatchee      97  69  94  62  88  58 /   0  10  10   0   0   0
Omak           96  63  94  56  87  53 /   0  10  10  10   0   0

&&

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

$$



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.