Synopsis: The forecast remains on track for a winter storm with snow in the Sierra and valley rain showers turning to snow by Friday morning.
The latest web cam (courtesy of Nevada Seismological Lab) shows the typical mountain wave associated with the ongoing high wind event this afternoon. As rain and snow load along the Sierra and Carson Range, then move into the area later this evening, winds may increase some with gusts to near 60 mph in the valleys.
Short Term: Looking at the big picture, a trough in the Gulf of Alaska can be seen at 300mb, with a 110-130 knot jet moving into the Pacific Northwest. This trough will gradually shift ESE into Northern California and Nevada tonight to bring snow to the Sierra and valley rain and snow showers tonight through Friday evening. The latest IR satellite image shows a well-defined cold front nearing the northern California coast at this time. A very cold air mass is seen behind the front with convective showers over the relatively warmer waters of the eastern Pacific.
The current forecast remain rather unchanged as the front moves in tonight, rain will increase over the Sierra with snow above 7,500 feet, with showers in the valleys. Snow levels rapidly lower in the early morning hours on Friday to bring a mix or rain and snow showers to the Carson City area. The latest IVT values suggest that a weak atmospheric river is accompanying the front, but much of that moisture is ahead of the dynamics associated with the front and upper level low, so it looks like it will likely not help to increase precipitation amounts much.
Looking at the updated MOS and SREF data, the forecast has slightly drier amounts from those last night for the valleys of Reno/Carson City, so any snow accumulations will still be likely an inch or less. Most areas will just see a dusting at best. The only caveat is for Friday afternoon, some snow bands may develop in the unstable conditions associated with low topped convection in the Sacramento Valley as it moves into the Sierra. Some of this may spill over into western Nevada to bring some localized heavy snow showers. At this time, it’s nearly impossible to determine where these snow showers may set up, but some localized accumulations may occur during the evening commute.
Long Term: Continuing to look ahead, a weak storm will move through the area Sunday night into Monday with most of the moisture missing the area except for a few rain or snow showers, followed by another potentially stronger storm by the middle of next week. Forecast confidence is very low as the pattern appears to be attempting to change back to the typical ridge in the west and trough in the east for more dry and mild weather for the Sierra and western Nevada. I’ll fine tune it as we get closer.