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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Tuesday
• 
• High: 77 °
• Low: 39 °
• Chance of T-Storms

• Wednesday
• 
• High: 52 °
• Low: 32 °
• Rain Showers

• Thursday
• 
• High: 59 °
• Low: 39 °
• Chance Rain

• Friday
• 
• High: 63 °
• Low: 43 °
• Mostly Cloudy

• Saturday
• 
• High: 64 °
• Low: 43 °
• Chance of Rain

Area forecast discussion 
National Weather Service Spokane Washington 
443 am PDT Tue may 21 2013 


Synopsis... 
the mild Spring weather will come to an end. A strong cold 
front will sweep through the region Tuesday through early 
Wednesday with showers likely, a chance of thunderstorms, breezy 
winds and cooler temperatures. Cool and showery conditions will 
prevail through much of the week, but will improvement a bit for 
the Holiday weekend. 






&& 


Discussion... 
today and tonight: a strong cold front moves into the region, 
with increasing rain and the potential for thunderstorms, with the 
added threat of snow coming to some of the low lands late tonight 
into Wednesday morning. This morning satellite imagery showed the 
cold front advancing onto the Pacific northwest coast and radar 
showed a swath of rain extending about 100-150 miles east of it. 
Deep layer lift with the cold front and supporting jet stream 
coming around the upper low is expected to sustain the precipitation. 
So precipitation that is just coming into the Cascades is expected 
to expand across central Washington through the morning and early 
afternoon. More widely scattered showers are expected to develop 
across eastern Washington and north Idaho this afternoon, before 
the steadier band of precipitation comes here late this afternoon 
and evening with the cold front. The center of the upper low and 
linked strong vorticity Max comes onshore near northwest or this 
evening, before swinging toward the central Washington/or border 
overnight. This will sustain the deep layer lift and keep 
precipitation chances high tonight across the eastern third of 
Washington, northern Idaho and west to southwest across the 
Okanogan through Cascades. 


As for the thunderstorm potential, convective parameters indicate 
increasing cape and unstable Li value through this morning and 
afternoon. The highest cape and most unstable Li values and so 
highest thunderstorm threat is projected to be from the Okanogan 
Highlands into the northeast mountains and Idaho Panhandle. 
However some low-grade cape and the high level total totals 
instability parameter indicating values between 30-36 c back into 
the Okanogan Valley through Waterville Plateau and Cascades, some 
thunder cannot be ruled out here either. Lastly models indicate 
some modest 0-6km shear across the region. Where instability is 
best values are between 35-50kts. This support the potential for a 
few organized and stronger thunderstorms, with a threat of hail 
and strong winds. However is the cold front passes quicker this 
potential will be limited. 


Temperatures will vary greatly from the Idaho Panhandle to the 
Cascades today. The incoming cold front and precipitation is 
expected to keep temperatures across the western basin through 
Cascades relatively cool and below normal. The eastern third of 
Washington and northern Idaho, however, will see more sun and less 
precipitation ahead of the cold front until later in the day. This 
will hold temperatures closer to or slightly above normal. 
Overnight into Wednesday morning colder air begins to punch in 
with the center of the upper low. Across the Cascades through the 
Palouse and Camas Prairie, models show 850 mb temperatures 
dropping to between 0 and -2 c. This suggests snow levels dropping 
to near 3000 feet across this region. So some snow remains in the 
forecast, even around Pullman. Accumulations should be limited by 
surface temperatures generally remaining above freezing. The 
exception will be in the higher Cascades and potentially around 
the Blue Mountains and higher Camas Prairie, including near 
Winchester. /J. Cote' 


Wednesday and Wednesday night: as we progress into the overnight 
hours we will continue to see widespread rain for the inland northwest 
and potentially moderate precipitation for parts of NE Washington 
and the northern Idaho Panhandle especially in the higher 
elevations. A major swing in temperatures will also be accompanied 
by the strong cold front. 


Mentioning the higher amounts of quantitative precipitation forecast we can base this off of not 
only the front slowing its progression in the mentioned 
areas...but also a strong jet will be supportive of higher 
precip. Intensity. The key to all of this relating to potential 
impacts of flooding will be the snow levels. For this forecast the 
snow levels were only slightly adjusted but with current forecast 
levels much of the precip that falls in the higher elevations will 
fall as wet snow rather than rain and this will help minimize 
the flooding impacts. If all precip were to fall as rain the 
flooding potential for rivers and streams would be elevated due 
to higher amounts of direct runoff...but given the current 
scenario the snowfall will act as a storage mechanism for much of 
the liquid and let it slowly melt and contribute to streams as 
temperatures warm back up. 


Other changes that were made to the forecast would be even further 
increasing the pops for the NE part of Washington and the Idaho 
Panhandle for Wednesday. Although pops were increased the over quantitative precipitation forecast 
amounts were trimmed back a little especially for the east slopes 
of the northern Cascades as new model runs show slightly lower 
amounts. Quantitative precipitation forecast was also trimmed for NE part of the forecast 
area...but remain high for the time frame which will still lead 
to rises in the streams and rivers. All rivers minus the Okanogan 
river near Tonasket is currently forecast to remain below flood 
stage and the Okanogan will only reach minor flood stage. In 
general this period will see temps drop significantly from the 
previous day (nearly 30f in some areas) and some breezy conditions 
as the front pushes through the area. /Fliehman 


Thursday through Monday...unsettled and cool conditions will 
continue through the extended period. Models are in very good 
agreement in holding a deep upper level low right over or very 
close to the forecast area through Friday...which is a high 
confidence recipe for showery conditions just about everywhere in 
the forecast area. The latest GFS and ec models both sense a 
secondary deformation area transiting the region from south to 
north on Friday which may enhance the density of showers on this 
day especially across the northern tier zones. 


For the upcoming Holiday weekend model consensus begins to break 
down but both models depict a weakening of the coherence of this 
upper low...an opening up and broadening trend into a general 
trough over the region (gfs) or a migration of the upper low 
center into southern Canada (ecmwf). Both solutions suggest a 
continued unsettled and showery regime...but showers may not be as 
prevalent as when the upper low was directly over the region. At 
this time the weekend does not look like a wash-out...but none the 
less iffy for outdoor activities...with guarded optimism that the 
densest shower activity will occur over the mountains north and 
east of the basin. Temperatures through the upcoming week will 
start out well below normal but slowly add a degree or two each 
day and top out around normal by next Sunday and Monday. /Fugazzi 


&& 


Aviation... 
12z tafs: a cold front moves from the Cascades to Idaho trough 
the next 12-18 hours, while the center of an upper low swings in 
from the west/southwest tonight into Wednesday morning. The front 
will bring an increasing area of rain near the western taf sites 
this morning and early afternoon. Scattered showers will develop 
further east this afternoon, while a steadier band of 
precipitation is expected to come by late afternoon and evening 
with the cold front. A chance of thunderstorms also exists 
throughout much of the region, with the best chance for organized 
activity north and east of kgeg. Storms may be locally strong with 
gusty winds/small hail. Tonight the incoming upper low is expected 
to keep precipitation chances high across eastern taf sites. Local 
MVFR cigs are possible in the more persistent precipitation. Colder 
air accompanying the upper low will allow some snow to mix in 
toward Wednesday morning but surface temperatures are expected to 
limit the accumulation threat below 3000 feet. /J. Cote' 




&& 


Preliminary point temps/pops... 
Spokane 73 41 51 36 61 42 / 30 90 90 40 30 30 
Coeur D'Alene 75 41 48 36 59 41 / 30 90 90 50 40 40 
Pullman 72 38 51 35 60 41 / 10 80 80 30 40 40 
Lewiston 80 44 59 41 66 46 / 30 60 70 30 30 40 
Colville 76 45 55 37 66 41 / 50 90 90 60 50 40 
Sandpoint 76 43 50 36 59 39 / 30 90 90 80 40 50 
Kellogg 75 40 44 34 55 40 / 30 90 90 70 50 50 
Moses Lake 71 43 62 40 68 44 / 70 50 30 30 30 30 
Wenatchee 63 43 58 42 65 45 / 60 60 40 40 50 30 
Omak 69 43 59 38 66 41 / 80 80 70 50 50 30 


&& 


Otx watches/warnings/advisories... 
Idaho...none. 
Washington...none. 
&& 


$$