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 45 46 47 48 49 50
000
FXUS66 KOTX 151203
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
503 AM PDT Sun Sep 15 2019

.SYNOPSIS...
A cool, wet frontal system will stall over western Washington on
Sunday and bring soaking rains to the Cascade mountains. The front
eventually pushes across the region by Monday morning. Showery,
breezy and cool weather will persist across the Inland Northwest
into the middle of next week. Drier and more seasonal weather is
possible late next week.

&&

.DISCUSSION...
Today through Monday night: A deep upper low is dropping southeast
along the British Columbia coastline near Vancouver Island early
this morning. A cold front associated with this large feature is
bringing widespread rain to western WA and the Cascades. As the
main energy with this low dives southward, it will undercut the
Inland Northwest. The front will lose its punch as flow aloft
becomes parallel to the boundary. The result will be rain slowly
spreading east but then breaking up into light rain showers. It`s
not until later Sunday night and early Monday morning that the
front gets a kick from another vort max rotating around the base
of the low. This will push the frontal boundary through eastern
Washington and northern Idaho resulting in a period of light rain
Monday morning. Showers will finally diminish in coverage before
the next round invades Tuesday.

A few details that are worth pointing out over the next 24 hours
include an impressive temperature gradient from southeast to
northwest today. While Lewiston will remain dry and in the sun,
their temperatures will reach the low 80s. Meanwhile under the
thick clouds and periods of rain, Omak will be lucky to get into
the lower 60s. This sharp thermal and pressure gradient will yield
increasing winds along and ahead of the frontal boundary. Winds
from the LC Valley to the Palouse and over to the lower Columbia
Basin will be warm and gusty.

With rainfall totals not overly impressive and winds well below
advisory threshold, the expectation is that this frontal boundary
is a very low impact event. /AB

Tuesday through Thursday: A secondary upper level low will drop
out of the Gulf of Alaska on Tuesday, and very slowly tracking
through the region into Wednesday and possibly Thursday. Periods
of showers are a good bet across most of the region Tuesday
through Wednesday. Breezy southwest winds also appear likely on
Tuesday as the initial front passes through. The upper low drops
south toward CA/NV on Thursday, but with cyclonic flow remaining
over the region, a few showers will continue to be possible. Look
for high temperatures in the 60s across the region during this
timeframe, which is on the order of 5 to 15 degrees cooler than
normal for this time of year.

Friday through Sunday: Northwest flow aloft will dominate over
the region on Friday as high pressure amplifies over the eastern
Pacific. A few showers will continue to be possible, particularly
across the eastern half of the CWA. The ridge of high pressure
will eventually build into across the western US late next week
and bring warmer and drier weather, but the timing remains
uncertain.
Dang

&&

.AVIATION...
12Z TAFS: A frontal boundary is stalling over central WA early
this morning bringing rain and increased clouds to the region. The
best chance for MVFR conditions are along the Cascades including
KEAT. Conditions ahead of this front are VFR and will continue to
be fair throughout the day. Only minor tweaks to the TAFs were
needed to dial in on gusty southwest winds ahead of the front and
lowering ceilings during the evening. A narrow band of
precipitation associated with the cold front will march across the
Columbia Basin Sunday night through early Monday morning. /AB

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        74  49  62  44  63  47 /   0  10  40  20  30  70
Coeur d`Alene  76  48  62  44  62  46 /   0  10  40  30  30  50
Pullman        77  45  61  41  64  44 /   0  10  40  30  30  50
Lewiston       83  54  68  50  71  53 /   0  10  40  40  20  50
Colville       73  42  67  37  65  40 /  40  40  50  30  40  70
Sandpoint      74  47  62  43  60  45 /  10  10  30  40  30  60
Kellogg        76  50  64  47  61  49 /   0  10  20  40  30  50
Moses Lake     72  49  69  43  66  45 /  20  40  10   0  50  70
Wenatchee      65  53  68  50  63  51 /  70  40  10   0  70  80
Omak           64  50  67  45  63  49 /  80  40  30  10  60  60

&&

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

&&

$$


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