Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 071118

Area Forecast Discussion
National Weather Service Spokane WA
418 AM PDT Wed Jun 7 2023

Temperatures will climb into the 90s through mid week with little
relief overnight. Chances for slow moving thunderstorms capable
of heavy rain and gusty outflow winds will increase Wednesday and
into next weekend. Temperatures will be cooler and closer to
season average Friday into Saturday.



...Very Heavy Rain with Thunderstorms Wednesday and Thursday...

Today through Thursday Night: Moisture will continue to stream in
from the southeast with values 200-250% of normal values by
Thursday afternoon/evening. This in combination of the low over
the Great Basin ejecting into southern Idaho and brining lots of
pieces of energy into the area and good instability will lead to
strong to isolated severe storms through this period.

Instability parameters off the GFS have decreased some, but the
NAM is still going strong. Even with GFS lowering cape values,
there is enough instability to work with to get showers and
thunderstorms to develop in the afternoon. Todays concern will be
across the central and southern ID Panhandle as well as the Blue
Mountains of SE WA. Impacts would be very heavy rainfall, gusty
outflow winds and of course lightning.

Tonight the HREF is showing several high resolution models keeping
showers or sprinkles moving to the west through the overnight
hours and Thursday morning. Have added a mention of slight chance
of showers everywhere, and keep the thunderstorm mention for the
central and southern ID Panhandle and portions of southeast WA.

Thursday and Thursday night could become quite active. Showers and
thunderstorms will develop late in the morning and continue
through the afternoon and overnight hours. These thunderstorms
have the potential to produce torrential downpours leading to
flooding and flash flooding concerns. The areal coverage will be
widespread...developing in the ID Panhandle and extreme eastern WA
in the late morning/early afternoon (30-50%) and then spreading
to the west into central WA through the late afternoon and
overnight hours (15-30%).

Temperatures today will top out in the 90s, which is 15 to 20
degrees above average for the beginning of June. Clouds will
spread into the region tonight as a result from the convection
across the southeast portion of our forecast area...and areas
further to the south and east. These clouds will keep our lows
quite warm for Thursday morning, with temps in the 60s. That
isn`t going to provide much relief or help those with no AC.
Temperatures have come down a few degrees for Thursday due to the
cloud cover expected. The clouds will be high cirrus, but enough
and thick enough to keep temps a few degrees lower. This also
raises concern for convection developing if we don`t get good
surface heating. The HREF does not seem to think it will be a
problem. Low temps again for Friday morning will be quite warm
given the cloud cover. /Nisbet

Friday through Wednesday: Ensembles continue to bring a sultry
pattern over the Pacific Northwest. A Low pressure system continues
to move through region bringing a decent fetch of moisture from the
South and East US. Model ensembles have come in better agreement.
The ECMWF and GEFS are predicting around an inch of precipitable
water(200% of normal) across the Inland Northwest. But ECMWF is
decreasing precip amounts. The Columbia Basin has a precip range of
0.2-0.4 inches. The northern mountains and Idaho Panhandle ranges
are 0.5-0.9 inches. These showers are expected to produce isolated
thunderstorms with a 5% of possibly reaching severe. Ensembles
continue to fluctuate between the runs on the instability for the
Friday and Saturday. The latest trend has weakened the CAPE
probabilities across the region. The best chance for thunderstorms
is the Lower Idaho Panhandle as probability of 1000 CAPE is around
50-60%. The rest of the Panhandle and Northeast WA is ranging 40-60%
probability of 500 CAPE. Outside of the typical thunderstorm
concerns of hail, wind, and lightning, the storms will have a weak
upper level steering flow leading to slow moving storms and possible
localized flash flooding concerns.

The pattern is expected through most of the weekend before a high
pressure system over the Pacific nudges the Low over the Montana
late Sunday through Monday. Afternoon convection could produce
thunderstorms over the Idaho Panhandle for Sunday and Monday. By
Tuesday, the high has pushed the moisture and instability out of the
area. Shower chances have diminished to isolated showers over
Northeast WA and the Idaho Panhandle through Wednesday.

For temperatures, the increased moisture and clouds will help cool
the highs, as the weekend is expecting 70s and low 80s. But the
clouds will also keep the nights from chilling. Overnight lows will
range from 50s to low 60s. By the start of the week, temperatures
rebound slightly. Highs will again be in the 80s to low 90s. Lows
will continue to be in the 50s and low 60s. By Wednesday, a
Northwest flow pattern will bring milder temperatures to the region
with highs dipping into the upper 70s to 80s. /JDC


12Z TAFs: VFR conditions will continue to prevail the next 24
hours. Convection will begin south and east of PUW and LWS aft
21Z. Storms will move to the northwest. Probability is low (about
15%) of storms actually impacting the air terminals, and thus do
not have it mentioned in the TAF. Unstable conditions will
continue overnight for portions of southeast WA and the central
and southern ID Panhandle. Storms will be more widespread and
potentially severe Thursday after 18Z.


Spokane        91  63  86  63  78  57 /   0  20  50  60  60  40
Coeur d`Alene  91  63  86  63  78  58 /   0  20  70  80  70  50
Pullman        87  60  81  59  76  54 /  10  20  70  60  60  30
Lewiston       94  68  88  67  84  63 /  10  20  60  60  60  40
Colville       91  58  89  59  76  55 /   0  20  40  70  80  60
Sandpoint      89  62  86  62  75  58 /   0  20  60  70  80  70
Kellogg        87  65  83  64  75  59 /  20  20  70  80  80  60
Moses Lake     95  61  89  62  81  55 /   0   0  20  40  40  30
Wenatchee      94  68  91  66  79  59 /   0   0  20  30  40  20
Omak           95  62  93  65  78  59 /   0   0  20  60  70  40



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