Area Forecast Discussion
Issued by NWS Spokane, WA

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717
FXUS66 KOTX 261214
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
514 AM PDT Mon Jun 26 2017

.SYNOPSIS...
Afternoon temperatures will climb into the 90s once again today.
Warm temperatures will fuel scattered thunderstorms late this
afternoon and this evening. Some storms may produce strong winds
and frequent lightning. Temperatures Tuesday, Wednesday and
Thursday will be close to average before warmer conditions return
Friday and Saturday.


&&

.DISCUSSION...

Morning update to add isolated thunder to the cluster of very
light showers tracking into the lower Basin. Got a few strikes in
southern Grant County and could have a few more isolated strikes
as this activity drifts NE through the morning. Most strikes look
to be inner cloud.


...Thunderstorms producing damaging winds possible Monday afternoon
and evening...

Monday and Monday night: Today will be another hot one with
temperatures warming back into 90s. Unlike the last few days,
look for an influx of moisture and clouds which will help prime
the atmosphere for a potentially active afternoon and evening of
thunderstorms. With hot and dry conditions in the lower levels of
the atmosphere creating what we call an "inverted V"
profile...damaging wind gusts are a big concern. Some storms will
also be capable of hail.

2AM satellite reveals one shortwave lifting north through Oregon at
this hour. This feature will be tracking into Ern WA this morning
and gradually ejecting into BC by the afternoon. Expect brief
sprinkles or perhaps a shower with this feature and potential for
wind gusts up to 30 mph. This is not the feature we are focusing
on for damaging winds this afternoon. Cannot rule out an isolated
lightning strike as we saw one earlier in the night south of
Yakima but the overall threat is very low.

By late afternoon (after 3PM) the focus will turn toward the next
shortwave ejecting from the coast and lifting into Northeastern
Oregon. Nearly all models support clusters of thunderstorms
developing along this wave and moving into far SE WA and NC ID
between 4PM and 8PM. Hi-res models such as the HRRR and 1KM WRF
run locally at the office are producing a robust outflow boundary
from this cluster of rain/hail cooled air with the potential for
damaging wind speeds in excess of 50 mph. It is tough to forecast
what type of wind speeds will surface from this but with DCAPE
values on the order of 1200 J/kg...this is a good setup for strong
outflow winds and confidence is increasing.

Meanwhile...another shortwave will be sagging in from the north
ushering a cold front into the region.  This boundary looks to
cross east of the Cascades between 00-03UTC (5-8PM) and will
provide lift into an unstable environment with CAPES in excess of
1000 J/kg. How quickly this boundary comes east will dictate how
the weather will pan out for areas further west into Central WA
but general trends in the models continue to support an increasing
threat for a brief window of thunderstorms from Moses Lake to
Republic before spreading to all areas east. Outflow boundaries
from storms in the south or any new cells will also complicate
matters and likely lead to new development away from these
synoptic features. For storms that develop in these areas of
Central & Eastern WA / N Idaho...some could also be strong with
the potential to produce strong outflow winds and hail.

The cold front will slide east through the Idaho Panhandle Monday
night with showers and t-storms continuing into the evening and
overnight periods. The boundary and precipitation threat will be
over by sunrise on Tuesday and drier westerly flow will settle
into the region. Tuesday will be breezy but not as windy as
previously thought. Humidity levels will still be dropping into
the teens so even with a 10 mph wind and locally higher
gusts...still could be problematic for any new fire starts in the
Columbia Basin but the potential for rapidly spreading fires is
not as much as a concern. /sb

Wednesday: A weak shortwave is expected to pivot into far north
Idaho and western Montana on Wednesday. The main upper trough is
forecast to be over central Alberta during the day Wed, but the
models vary on depth of the wave diving into the Panhandle. Even
the most aggressive solution provided by the ECMWF won`t give our
region widespread showers. Given the NW trajectory of the wave,
it won`t have much moisture associated with it, so convective
coverage doesn`t look impressive at this time. Precipitation
chances have been limited to 20-30 percent Wed afternoon/evening
to the Panhandle and far northern counties of northeast and north
central Washington.

Thursday: A high pressure ridge will begin to build into western
Washington on Thursday. There should be enough residual troughing
over the Panhandle to keep afternoon temperatures in the upper 70s
and low 80s for places like Bonners Ferry, Sandpoint, and Kellogg.
However, central Washington will likely experience upper 80s or
lower 90s Thursday afternoon as our next round of warmer
temperatures begins.

Friday through Sunday: Temperatures have been raised for Friday
and Saturday. The evening model runs have slowed the arrival of
onshore flow associated with the trough in the Gulf of Alaska.
If the evening runs of the ECWMF and GFS pan out, much of the
region will have the potential for upper 80s to mid 90s Friday and
Saturday. The GFS and ECMWF suggest enough instability over the
Panhandle for a mention of a slight chance for thunderstorms
Saturday afternoon/evening. For Sunday into Monday, there is
loose agreement between the medium range models that the upper
trough will make landfall over British Columbia. If this scenario
pans out, we should see increasing onshore flow leading to a push
of cooler marine air Sunday into Monday. This period has the
potential to be breezy as well. /GKoch

&&

.AVIATION...
12Z TAFS: Active weather expected during the next 24 hours.
One disturbance tracking NE through the forecast area this morning
with sprinkles and isolated lightning strikes. This will clear out
aft 18z and should have a relatively quiet afternoon. After
23Z...thunderstorms will approach from NE Oregon with a moderate
threat for strong outflow winds impacting Lewiston, Pullman, and
potentially expanding into Spokane-Cd`A. Speeds expected to decr
upon reaching the Spokane-Cd`A corridor but any new convection
could complicate matters. A cold front interacting with the
cluster of convection arriving from the south will keep
showers and storms possible through much of the night with a
gradual clearing from west to east early Tue morning. Overall,
Wenatchee looks to be west of the main thunder threat this aftn
but will see an incr in NW winds. Moses Lake will also be close
to the western fringes of the thunder threat yet models continue
to bring some activity in vcnty btwn 01-04Z. /sb

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        93  61  83  56  80  56 /  20  40   0   0  10  10
Coeur d`Alene  91  58  81  53  77  53 /  20  40   0   0  20  10
Pullman        90  60  79  52  77  52 /  20  50  10   0  10   0
Lewiston       97  64  87  58  85  57 /  30  60  10   0  10   0
Colville       93  55  85  51  82  51 /  20  20   0   0  20  10
Sandpoint      88  55  80  48  78  47 /  20  30   0   0  20  20
Kellogg        90  57  77  51  75  50 /  20  60  10   0  20  10
Moses Lake     97  60  88  54  86  55 /  10  20   0   0   0   0
Wenatchee      94  62  86  59  85  58 /  10  10   0   0   0   0
Omak           95  56  87  53  85  53 /  10  10   0   0  10  10

&&

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

$$



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