Flash Flood Warning 1, NWS Spokane, WA

918 
WGUS76 KOTX 092335
FFSOTX

Flash Flood Statement
National Weather Service Spokane WA
435 PM PDT Fri Aug 9 2024

WAC047-092345-
/O.CAN.KOTX.FF.W.0001.000000T0000Z-240810T0000Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Okanogan WA-
435 PM PDT Fri Aug 9 2024

...FLASH FLOOD WARNING FOR THE CEDAR CREEK BURN SCAR IS CANCELLED 
FOR WESTERN OKANOGAN COUNTY...

Heavy rain has ended over the Cedar Creek Burn Scar. 

&&

LAT...LON 4856 12036 4854 12034 4852 12031 4850 12034
      4851 12039 4855 12045 4858 12046 4859 12044
      4859 12041 4858 12039

$$

OTX

Area Forecast Discussion
National Weather Service Spokane WA
1121 AM PDT Fri Aug 9 2024

.SYNOPSIS...
Expect a chance for showers and thunderstorms today into
Saturday, with mountain shower chances lingering into early next
week. Lightning from thunderstorms will be capable of starting
new fires. Thunderstorms will also come with brief heavy rain,
small hail and gusty outflow winds. Otherwise, look for periodic
breezy conditions and daytime temperatures dropping to near normal
for Monday through much of next week.

&&

.DISCUSSION...

Today through Saturday night: An upper level low pressure area
spinning over southern BC will divert shortwave disturbances across
the region. The atmosphere is primed for convection with mid level
lapse rates in the 700-500 mb layer greater than 7 C/km. Any spindle
of shortwave energy that moves across the forecast area will be
capable of sparking off convection (both elevated and surface
based), and this is evident by persistent nocturnal convection that
is currently being observed in the northern Washington Cascades
early this morning. Water vapor satellite imagery shows a more
robust shortwave on the synoptic scale rounding counter-clockwise
across Vancouver Island and out over the eastern Pacific. This
shortwave looks to deepen slightly this morning as it moves into
western Washington. Positive vorticity advection associated with
this disturbance will be the impetus for synoptic scale lift,
especially over the Cascade Mountains. The HREF model indicates
surface based CAPEs of 500 J/kg around Omak, Chelan, Wenatchee to
near 1000 J/kg closer to the Cascade crest. Convective allowing
models (CAMs) all are in agreement with scattered to widespread
thunderstorm development up and down the northern Washington Cascade
Mountain Range that includes up into Canada. Steering flow will be
weak at around 5-10 kts from the west and northwest. Convection is
expected to expand in coverage through the afternoon favoring the
Cascade crest earlier in the afternoon and then drifting further
east off of the higher terrain later in the afternoon and into the
evening hours. Bulk shear is weak with pulse type convective cells.
There's enough CAPE though that some thunderstorms are expected to
pulse up quickly and with an updraft that may support small hail
development up to around a half of an inch. More concerning will be
the potential for heavy rain underneath the cores of the storms.
Modest Pwat values of 0.8-0.9 inches support the potential for heavy
rain that could lead to runoff issues in steep terrain, and
specifically on burn scars. CAMs also indicate an outflow boundary
developing ahead of the convection along the leading edge of the
convection. The HRRR and UW-WRF models show gusty northwest winds
spilling down Methow Valley, Okanogan Valley, and out across the
Waterville Plateau into the western basin and Moses Lake Area. Some
gusts cold be in excess of 40+ mph. A red flag warning will be
issued starting from noon today and extending out through midnight
tonight. Lightning density looks to be high enough to overcome rain
that occurs and potentially extinguishes any new fires.

Potential for thunderstorms will continue into the overnight hours
with up to 200-300 J/kg of MUCAPE spreading out across eastern
Washington and into the Idaho Panhandle. Convective parameters are
modest at best, and I only expect the potential for isolated
thunderstorms. Tough to pin point exactly where these cells will
develop, but generally across the northern to northwestern half of
the forecast area. Much of the region will continue to see the
potential for thunderstorms on Saturday. The mountains will be
favored with around a 25 percent chance and in the basin closer to a
15 percent chance. Similar hazards are expected as today with
thunderstorms moving slowly featuring brief heavy rain, small hail,
gusty outflow winds, and isolated to scattered lightning strikes.
Will see how convection plays out today if a red flag warning is
needed for Saturday due to abundant lightning. /SVH

Sunday through Thursday: Weak troughing will be the main synoptic
feature through the period. Unsettled conditions with occasional
chances for showers are forecast, but there remains enough
inconsistency in the models that it's difficult to pinpoint any
time when those chances will be greatest. Periods of breezy winds
should also be anticipated. Daytime temps to remain a bit hotter
than normal Sunday, but will drop to near daily normals for the
remainder of the 7-day forecast. /KD

&&

.AVIATION...
18Z TAFS: Scattered to widespread thunderstorms are expected over
the Cascades this afternoon. Storms will be slow moving and
feature frequently cloud lightning, gusty outflow winds of up to
around 40 mph, small hail and brief heavy rain. Storms will move
slowly to the east and begin to off of the Cascades into the
western portion of the basin in the evening. Impacts from
thunderstorms can be expected at the Omak (KOMK) and Wenatchee
(KEAT) airports after 21Z. Nocturnal convection is expected to
spread across the rest of eastern Washington overnight, but is
expected to be isolated in coverage and decrease in strength with
less potential for impacts. Northeast winds will continue through
the day with gusts of up to 20 kts particularly down the Purcell
Trench (KSZT-KCOE) and out over the Columbia Basin. Smoke and haze
will continue due to regional fires burning, but unlikely to
reduce visibility below 6SM.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: Confidence remains
high for VFR conditions. There is a 30 percent chance that
thunderstorms will impact KEAT and KOMK between 21-06Z today.
High resolution models also suggests a 30-40 kt outflow wind gust
down the Okanogan/Methow Valleys from convection between 22-03Z
that may impact the Methow Valley State Airport and Omak Airport.
/SVH

-----------------------

Confidence descriptors:
Low - Less than a 30 percent chance
Moderate - 30 to 70
percent chance
High - Greater than a 70 percent chance

For additional probabilistic information for NWS Spokane airports,
please refer to the Aviation Dashboard on our webpage:
https:/www.weather.gov/otx/avndashboard

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        89  60  91  60  89  59 /   0  20  20  20   0  10
Coeur d'Alene  86  58  87  57  86  58 /   0  10  20  30   0  10
Pullman        87  58  88  56  86  56 /   0  10  20  20   0   0
Lewiston       96  68  97  67  96  66 /   0  10  20  20   0  10
Colville       88  49  89  49  88  49 /  10  20  30  30  10  10
Sandpoint      83  55  83  53  84  54 /   0  10  20  30  10  10
Kellogg        85  61  84  60  84  61 /   0  10  30  30  10  10
Moses Lake     93  63  94  60  91  59 /   0  20  20  20   0   0
Wenatchee      93  70  93  67  91  66 /  10  20  30  20   0   0
Omak           96  62  95  63  94  63 /  20  30  30  20   0  20

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Red Flag Warning from noon today to midnight PDT tonight for
     East Portion of North Cascades National Park/Lake Chelan
     National Recreation Area (Zone 697)-East Washington Central
     Cascades (Zone 696)-East Washington North Cascades (Zone
     698)-Foothills of Central Washington Cascades (Zone 705)-
     Methow Valley (Zone 704)-Okanogan Valley (Zone 703).

&&