Fcst Discussion 2017 02 02 Richard Grotjahn

SPC advisories: Winter storm warning (pink) or advisory (purple) over most of NW (2-14 in E WA, higher in mts) and Sierras (1-3ft) (tan & brown) high wind gusts to 65mph (45 in Sac Valley), now until 4am Sat. Lake effect snows and gale warnings over Great Lakes. Freezing drizzle/fog CO; frz rain WA & N. OR

24 vs 48hr, FrzRn Columbia/E Wa/Or?

Freeze Rain Meteogram

S. TX – right jet entrance region?

Compare recent model simulations

3-day precip totals

Local Meteogram

The End

Notes Major storm in NW and Sierras: PVA, WAA Heavy snows in mtns Possible frz rn Second storm affecting region by Sunday morning Lake effect (stationary P Great lakes) Upslope WY/MT (stationary, stops as the SLP high moves east) PVA for upper level system (sfc hi) moving across cntrl US Front in the SE: Onshore flow in S. TX, possible rt entrance regn of jet, models disagree on placement and magnitude: nothing in GFS, more in NAM GFS more widespread P, low off W coast similar (slightly NW of NAMB position) Nor Cal: Wet for awhile… 3 day totals in peaks of 3-8 inches of liquid water equivalent!

NCEP text guidance Valid 00Z Fri Feb 03 2017 - 00Z Sun Feb 05 2017 ...Heavy snow possible for portions of the Sierras, Absarokas, Bitterroots, Blue and Salmon River Ranges... ...Heavy rain possible for Northern California Coast... ...Lake effect snow downwind from the Lakes Superior, Huron and Ontario... High pressure drifting southeast from the northern High Plains to the Mississippi/Tennessee valleys will push a cold front slowly through Deep South and Southeast this weekend. Gulf moisture will pool along this boundary and help generate rain along the Gulf Coast an up to the Southern Appalachians and Mid-Atlantic. The rain will slowly move to the Western/Central Gulf Coast by Friday into Saturday. To the north, upper-level energy moving over the Great Lakes will aid in producing lake effect snow downwind primarily from the Lakes Superior, Huron and Ontario through Saturday. An upper-level low over the Eastern Pacific will slowly weaken and move onshore over the Pacific Northwest by Friday evening. The system will bring a plume of moisture into the Central California Coast and into parts of the Northwest into the weekend. Coastal areas will have rain, possibly heavy at times, while areas of higher terrain will have snow. Snow will spread eastward into the Northern Rockies by Friday evening and into the adjacent Northern Plains by Saturday. A secondary low pressure system from the Pacific will advance inland this weekend; which, will bring warmer air into portions of the Northwest. This will allow for the development of rain/freezing rain mix for portions of the Columbia River Gorge and other parts of the Pacific Northwest throughout the day on Friday and into early Saturday. The Sierra Nevadas and ranges from eastern Oregon to northwest Wyoming will likely have heavy snow over the next few days.