000
FXUS66 KOTX 191136
AFDOTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
436 AM PDT Sun May 19 2013

.SYNOPSIS...
Another day of seasonably mild conditions are expected today with a
few mountain showers and possible thunderstorms. Monday will be a
dry and mild break period before a strong storm system enters the
region on Tuesday with a chance of showers and thunderstorms.
Showery and unseasonably cool conditions will envelop the region
from mid-week onward.

&&

.DISCUSSION...
Today and tonight...As longwave trof axis moves east ridging
moving in from the west will get within closer proximity to
Eastern Washington and Northern Idaho thus some decrease in
instability should result. Since the extreme western edge of the
trof is still close enough to influence the forecast area and
many short term model runs such as the HRRR depict some rotation
associated with the weak convection generated the idea is that
majority of the convection is of the elevated forced variety
rather than surface based type...especially when one considers
how much cloud cover is remaining in place which makes it much
much more difficult for surface based convection to initiate.
However since there is riding approaching from the west and getting
closer the drop in pops and precipitation amounts to near zero
after midnight remain a valid course of action. Forecast temps
given this trof remain just a sliver on the cool side of what
would be considered normal for this time of year. /Pelatti

Monday and Monday night...A relatively benign and quiet period
will prevail on Monday and Monday night as a weak upper level
ridge pops up over the region in advance of a deep upper level low
scheduled to arrive on or about Tuesday/Wednesday. thus...Monday
will probably be the last reasonably pleasant and dry day for the
region. 

On Tuesday latest models are in good agreement and reasonably
consistent in digging a deep upper level low pressure out of the
Gulf of Alaska and placing it off the northwest coast by
afternoon. This will put the forecast area under a moist southerly
difluent flow on the east flank of this upper feature. This is a
showery and thundery pattern for the region...and while details
regarding actual frontal placement and deep instability are
uncertain at this time...confidence is growing that Tuesday will
be an increasingly active day of general deterioration from west
to east...with high temperatures over the east actually increasing
over Monday's highs in a warm advective southerly flow
scenario...while over the west an onset of showers during the day
will moderate temperatures. The main thunder threat on Tuesday
will likely be over the east near the exiting thermal trough and
concentrated in the afternoon and evening hours.

From Tuesday night through Friday there is uncommonly good model
agreement...repeated over numerous run now and thus inspiring high
confidence...that the aforementioned deep closed low will take up
residence over or very near the forecast area. This will promote a
return to a cooler and showery pattern more like early April than
late May. Wednesday appears at this time to be the wettest
day...with the main tough baroclinic zone and surface cold front
efficiently enhancing available moisture into widespread showers
over most of the region. There is high confidecne that Thursday
and Friday will also be showery and cool...but the nature of the
showers will be more hit-and-miss with smaller areal extent than
Wednesday. Snow levels will likely drop down to the 4000 to 5000
foot range on average...4kft at night and 5kft during the day. 

In summary...at this time there is high confidecne that Monday
will be dry and mild and Tuesday active and potentially
thundery. There is high confidence that Wednesday through Friday
will be cool and showery...with the best chance of very showery or
downright rainy conditions on Wednesday. /Fugazzi

Friday Night through Saturday Night: The unsettled weather pattern
looks to continue for the Inland NW. The low will remain almost
stationary given current model runs throughout the period which
will continue to pump Pacific moisture into the region. Given the
placement of the low and the increased cloud cover our daytime
high temperatures will not be able to reach potential maximums
keeping us a few degrees below normal and lows will follow the
same trend. Concerning the potential for rainfall in this pattern
I followed the same idea as the day shift with above climo POPs but
did increase a little for the NE Mtns of WA and the Mtns of the ID
Panhandle given the orientation of how the moisture will flow into
the region. Current models look to keep most of the heavier more
consistent rain north of the border in BC and lesser amounts in
the areas mentioned above. Given the location of the precip we
will have to continue to monitor the rivers and streams around the
region especially basins that receive contributions from the
areas of BC that will likely see more precip. Precip patterns and
amounts will continue to be refined as we push closer to this time
frame...but in general we can say the forecast will include below
normal temps with cloudy skies and an increased chance for precip.
/Fliehman

&&

.AVIATION...
12z TAFS: Weak low pressure gradualy moves east and allows for
an improvement as far as less clouds and drier conditions near
6Z Monday and beyond. Otherwise considerable mid level cloud cover
and some spotty shower activity remains but VFR conditions still 
prevail. /Pelatti

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        66  46  72  52  76  42 /  20  10   0   0  20  50 
Coeur d'Alene  65  44  71  47  77  42 /  30  20   0   0  20  60 
Pullman        63  42  71  47  77  40 /  20  10   0   0  10  60 
Lewiston       68  49  78  53  83  47 /  20  10   0   0  10  50 
Colville       72  43  77  45  80  43 /  20  20  10  10  40  60 
Sandpoint      65  42  72  44  77  41 /  50  30  10   0  30  70 
Kellogg        60  46  70  50  76  41 /  40  30  10   0  20  60 
Moses Lake     76  46  80  50  78  44 /  10   0   0   0  30  50 
Wenatchee      73  49  78  53  72  44 /   0   0   0   0  40  50 
Omak           74  43  78  46  76  44 /  10  10   0   0  50  50 

&&

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

$$