Monday Morning Update on Tonight/Tuesday Snow

The storm system that will eventually bring measurable snow to the Valley later tonight and Tuesday remains on track. I have made slight adjustments in the timing for the changeover from rain to snow but the forecast for snowfall amounts has not changed.

I’ve also included a brief period where we likely see a mix of precipitation for an hour or two tonight as the temperature becomes more favorable for steady snowfall.

ODOT has been and continues to pre-treat the major highways. However, rain is expected this afternoon ahead of the cold air. This might be one of those instances where pre-treatment is less effective. The rain will mix with snow (and, perhaps even some graupel and/or freezing drizzle) for a while before changing over to all snow. Snowfall may be heavy at times especially before sunrise Tuesday.

FUTURECAST RADAR from the hi-res model

LOCAL ACCUMULATION
This is the tricky part. While it may snow at a fairly good clip for a time tonight and the ground is relatively warm yet, snowfall can be heavy enough to accumulate on the roads. This is especially true for bridges and overpasses as well as untreated surfaces. The wind will be gusty for a while tonight as well which can cause whiteouts. The Tuesday morning commute might be a bit of a challenge.

As for the total amount of snow expect an inch or two locally. I would lean toward two to three inches for locations in the northern half of the county. Everyone in the Valley will get in on snow tonight through Tuesday morning.

The steadiest snowfall will taper off to snow showers after 9:00/10:00 AM. Scattered snow showers will be possible until after lunchtime Tuesday before all snow exits early in the afternoon.

TEMPERATURES WILL TURN MUCH COLDER
Temperatures today in the upper-40s will seem almost balmy tomorrow. True arctic air will rush in with tonight’s snow and afternoon high temperatures tomorrow will not get much better than the upper-20s – a 20° drop on average. Temperatures will dip all the way to the mid-teens pre-dawn Wednesday. It might warm to around freezing Wednesday afternoon.

Short Range Ensemble Forecast (NWS) temperature trend over the next 48 hours at New Phila. The straight blue line across the graph represents 32°.
NAM3k (North American Model) snapshot of WIND CHILL temperatures early Wednesday morning.

REST OF THE WEEK
We should remain dry Wednesday through Saturday. Temperatures will moderate some during the period but will remain below average.

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