601 FXUS66 KOTX 291038 AFDOTX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SPOKANE WA 238 AM PST Tue Jan 29 2013 .SYNOPSIS... The weather pattern will remain active and wintry through Thursday as a number of storm systems will result in periodic heavy snow accumulations. There will be a break in the weather today...however another extended snow event looks likely for the region with the focus of the heavier snow again for the higher terrain of the Central Idaho Panhandle...the Blue mountains and the Camas Prairie. High pressure will build into the region at the end of the work week and linger into the weekend with fog and low stratus expected across much of the basin and in the valleys. && .DISCUSSION... Today through Wednesday...After a break today the weather pattern will quickly go back to an extended period of rain and snow through a majority of the week. North-northwest flow and ample low to mid level moisture will result in a continuation of snow across my southeast zones. Local radar and traffic cameras are showing snow beginning to back off somewhat in the Coeur D'Alene area and in Shoshone county towards the Idaho/Montana border. Highlights in those areas are in effect until 700AM and for now I will let them ride...but it looks like these may come down ahead of schedule. Further south across the Palouse it may be a little more dicey. All the models save the NAM have precipitation coming to and end very near 15z and for now that is the way we will play it. The Blues and Camas Prairie will not see precipitation slowing until between 18-20z. Lastly northwest flow will keep snow near the Cascade crest for what seems like an eternity...but at least until the ridge moves in land. Snow will be heavy near the crest but will decrease dramatically within a short distance of the crest. One last thing we need to keep an eye on today is winds across the southern Palouse and the Camas Prairie. Winds in some of the exposed area are gusting in the 20s to lower 30s. The models are having a tough time with these and I went ahead an bumped the winds up for this morning. This will make for localized areas blowing and drifting snow at times through this morning for hazardous driving conditions. Tonight and Wednesday... the break will last until this evening when the next surge of moisture comes streaming through the region...resulting in another round of extended precipitation. Satellite loopers indicate a rich plume of sub-tropical moisture moving up from near Hawaii and currently topping the ridge this morning. PW's will increase after 00z to over 120 percent of normal. There are no strong forcing mechanisms with this weather system. Precipitation will be provided by the combination of moderate isentropic lift and a saturated atmosphere. Precipitation will begin after 00z from the northwest and move south-southeast through the forecast area overnight. This upper level flow pattern puts the focus of the heaviest precipitation across my southeast from southern Shoshone county south to the Camas Prairie and the Blue mountains..and possibly the southern Palouse. With the exception of the deep basin and the L-C valley snow levels will begin near the surface. As south to southwest surface winds increase warm air will move into the region from the south. Snow levels will struggle to increase through the night...but by Wednesday afternoon snow levels will have increase above 4000 feet across the south and above 2500 feet as far north as the highway 2 corridor. The higher terrain of the Blues...Camas Prairie and southern Shoshone county may see between 6-10 inches by Thursday morning...with 2-3 inches for the Palouse and up to a foot near the cascade crest. Otherwise only light amounts are expected. Highlights may be needed...however at this time we have numerous highlights and until these come down through the day we will hold off on issuing anything new. /Tobin Wednesday night through Monday: The large scale ridge of high pressure over the Pacific will gradually inch its way over the region. The strong northwest-orientated upper level jet will weaken and slide off to the south and east, meanwhile the mid and upper levels of the atmosphere will continue to stabilize and warm aloft. Due to the west to northwest flow at the low and mid levels, orographic lift will enhanced especially across the ID panhandle, Blue mountains and southeast Washington, and near the Cascade crest, although the coverage and intensity of the precipitation will be decreasing. Dry downslope conditions will be found from the lower Cascade valleys, and across the western Columbia Basin. Both the GFS and the ECMWF show a weak disturbance moving through the flow aloft Thursday into Thursday night which looks to enhance cloud cover and precipitation over the region. Then by Friday, there is good model agreement that the large scale ridge axis will shift across WA state, drying out the region and bringing an end to the snow showers. But the area of high pressure will strengthen the low level inversions and bring a better chance of low clouds and fog to the low lands which will persist through Saturday night. By Sunday, there is the potential that the high pressure ridge to break down by a weak upper level disturbance from the Pacific with some mountain snow showers possible. The high pressure ridge will return but not as strong with more Pacific energy breaking through the flow and keeping a more active regime to the Inland Northwest. Temperatures will be close to normal through the period./rfox. && .AVIATION... 06Z TAFS: Snow in southeast WA and the southern Panhandle will continue through the night before ending on Tuesday morning. The KGEG/KSFF/KCOE TAFs should see an end to the snow late tonight but IFR conditions will persist there into Tue morning. Expect to see VFR weather there in the afternoon. Exception to this will be at KPUW where IFR cigs will persist through much of the day. To the west, KEAT and KMWH will have VFR weather for the next 24 hours. Snow will redevelop after 00Z east of KMWH. RJ && .PRELIMINARY POINT TEMPS/POPS... Spokane 32 26 36 30 36 27 / 10 70 40 30 40 30 Coeur d'Alene 33 26 35 31 36 28 / 10 70 50 50 70 40 Pullman 33 27 39 33 39 30 / 70 70 70 70 60 50 Lewiston 41 32 44 37 46 32 / 80 70 70 70 60 40 Colville 33 25 35 30 41 26 / 10 60 20 20 30 30 Sandpoint 33 26 34 28 36 28 / 10 70 60 60 70 60 Kellogg 31 25 35 30 39 29 / 80 80 80 80 80 70 Moses Lake 37 28 41 29 41 27 / 10 10 10 10 10 10 Wenatchee 36 28 38 29 39 27 / 10 20 10 10 10 10 Omak 29 24 31 24 36 25 / 10 40 10 10 10 10 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...Winter Storm Warning until 7 AM PST this morning for Central Panhandle Mountains-Coeur d'Alene Area-Idaho Palouse. Winter Storm Warning until 4 PM PST this afternoon for Lewis and Southern Nez Perce Counties. Winter Weather Advisory until 7 AM PST this morning for Lewiston Area. WA...Winter Storm Warning until 7 AM PST this morning for Washington Palouse. Winter Storm Warning until 4 PM PST this afternoon for Northeast Blue Mountains. Winter Weather Advisory until 7 AM PST this morning for Lower Garfield and Asotin Counties. Winter Weather Advisory until 4 AM PST Wednesday for East Slopes Northern Cascades. && $$