Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 222334
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
434 PM PDT TUE JUL 22 2014

.SYNOPSIS...
A strong storm system will move through the region tonight and
Wednesday bringing the potential for thunderstorms and heavy rain.
Cool and windy weather is expected for Thursday. Temperatures
will rebound by the weekend and be accompanied by dry conditions.
Hot weather will return to the area on Sunday and early next week.

&&

.DISCUSSION...
Tonight through Wednesday night: A very active pattern is expected
over the Inland Northwest in the next 36 hours. Much of northeast
OR, into extreme southeast WA and into the Central Panhandle Mtns
has seen a good amount of sunshine through the first half of
today. This has destabilized the atmosphere with thunderstorms
popping up across much of northeast OR this afternoon. Further
north into southeast WA we still remain capped and less unstable.
I expect much of this thunderstorm activity will weaken as it
progresses northward through at least the early portions of the
afternoon. Mid level lapse rates will become more unstable through
the evening into tonight with Most Unstable CAPEs (or MUCAPEs) of
around 200-400 J/KG between the 700-300 mb layer. The best
instability closer to 400 J/KG in this layer will be across the
southeast portion of the forecast area this evening (generally
over the Palouse to the Central Panhandle Mtns and points
southward). We will also see some large scale forcing occurring
with a shortwave moving northward out of California into Oregon.
The southeast portion of the forecast area will also be in the
left exit region of a 100 kt jet streak. This forcing combined
with the increasing instability should result in some stronger
thunderstorms developing across the southeast portion of the
forecast area. Gusty outflow winds and small hail will be the
primary thunderstorm threat. I would not be surprised if some
thunderstorms approach severe levels.

The threat for thunderstorms will increase northward across the
region overnight. MUCAPEs away from the southeast portion of the
forecast area will not be as exciting closer to 200 J/KG in the
700-300 mb layer. This will be sufficient for the possibility of
isolated thunderstorms. The mid level front offshore associated
with the upper level low pressure system will begin to approach
the Cascades Wednesday morning. A band of moderate to heavy
rainfall is expected to form out ahead of the front. There will
also be the possibility for some thunderstorms embedded in this
ran band that may produce more intense rainfall rates.
Thunderstorms will continue to be possible over the Cascades
through the afternoon into the evening as the cold pool aloft
shifts over this area of the region. Rapid runoff from the heavy
rain is expected. Debris or mud flows will also be possible with
the highest concern for recent burn scared areas. A Flash Flood
Watch has been issued to cover this threat and is in effect for
Wednesday morning through Wednesday evening.

Severe weather will also be possible Wednesday afternoon/evening,
mainly across the eastern half of the forecast area. The upper
level low will push across the Cascades just after peak heating.
Very strong upper level dynamics will accompany this wave.
Instability is a little bit of a question mark as there will be a
substantial amount of cloud cover along the mid level front. The
best possibility for sun breaks and instability will be in the
Panhandle where the best severe threat will be. Main threats will
be for outflow winds and hail. P-wats will also be up around an
inch, so these thunderstorms will be very wet. The good news is
that storm motion will be quick will move at approximately 25-30
mph to the northeast.

Winds will become gusty behind the cold front on Wednesday. Expect
sustained winds of 20-25 mph across the basin with gusts up to
30-35 mph by the late afternoon hours. /SVH

Thursday through Saturday night: A deep closed low will be moving
over the forecast area on Thursday. This low is anomalously deep
for this time of year. And the result will be much cooler
temperatures. In fact, some locations north and east of Spokane
won`t even reach 70F for a high. The clouds and showers should be
confined across the northern locations (north of Highway 2). We
could also see a few thunderstorms near the Canadian border. The
cold air aloft will cause the atmosphere to be unstable, but the
low moves east of our area during the afternoon, so the timing is
not optimal. The other aspect of Thursday will be the wind, 20-30
mph. Combined with the cooler temperatures, this will make for a
decidedly non-summerlike day.

The low moves out of the area Thursday night as high pressure
builds into the area. This will bring dry weather with a gradual
warming trend.  RJ

Sunday thru Tuesday... EC and GFS in good agreement on overall
pattern thru this period. Strong ridging over the region on Sunday
moves slightly east as a short wave moves onshore over the central
BC coast and the AK panhandle. Flow shifts to weak southwesterly
but models keep most of the precipitation and moisture well south
and east of the area. Above average temperatures on Sunday will
bump up a few degrees on Monday and Tuesday with little or no
chance of precipitation. JL

&&

.AVIATION...
00Z TAFS: A low pressure system circulating off of southeast BC
will continue to push moisture across the Inland Northwest with
showers and thunderstorms affecting all TAF sites. The strongest
thunderstorms are expected to develop over northeast OR and track
into southeast WA and into the central portions of the ID
panhandle. Gusty outflow winds and small hail will be possible
with these thunderstorms through the evening. Scattered showers
and isolated thunderstorms will continue overnight but confidence
is low that they will affect any particular TAF site. -TSRA will
be more widespread Wednesday afternoon with thunderstorms capable
of producing heavy rain, small hail and gusty outflow winds. /EK


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        62  83  52  69  51  77 /  40  50  80  10  10   0
Coeur d`Alene  60  84  53  68  52  76 /  40  50  80  20  10   0
Pullman        62  84  49  68  46  76 /  50  40  70  10   0   0
Lewiston       65  90  58  77  57  85 /  50  40  60  10   0   0
Colville       58  81  51  71  51  78 /  20  60  80  40  10   0
Sandpoint      58  85  51  65  49  73 /  30  50  80  50  10   0
Kellogg        58  85  52  64  50  71 /  50  40  80  20  10   0
Moses Lake     66  83  56  77  57  85 /  30  50  40  10   0   0
Wenatchee      63  75  59  74  59  85 /  40  70  40  10   0   0
Omak           60  77  55  76  53  85 /  20  80  60  20  10   0

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Flash Flood Watch from Wednesday morning through Wednesday
     evening for East Slopes Northern Cascades-Okanogan Valley-
     Wenatchee Area.

&&

$$




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