MOUNTAIN WEATHER FORECAST

Time and Day:  0700 Monday

The Snapshot:  Happy MLK Day.  The approaching warm/rain event has postponed its arrival by 24hrs or so.  Therefore, today will continue to be dry with increasing clouds, light snow changing to rain tomorrow with the main rain event now expected Tuesday night/Wednesday.

The Science: The high pressure and the cold temperatures in the eastern basin are sure being suborned, which is good for Stevens Pass.  Another cold and clear morning with single digits at Pass level and warm air aloft.

Temperatures hit 36⁰ f on top of Tye Mill yesterday but have cooled off to the low 20’s this morning.  The temperature inversion will continue with a thin low-level cloud deck east of the crest with increasing high cirrus clouds moving in. 

The advertised strong southwest zonal frontal system has delayed its arrival by a day or so but is still on track to bring rising freezing levels and heavy precipitation to the mountains.

The models now have the system playing out like this:  Freezing levels reach 4000’ tonight with east flow holding Pass level temperatures below freezing until early tomorrow morning. Temperatures continue their ascent, with freezing levels peaking around 6500’ sometime tomorrow afternoon/night.  Cold air to the east will certainly have an effect on the snow levels vs freezing levels. So a mixture of snow and rain between 4000’ and 6000’ will be possible throughout this storm event.   

Light snow begins after 4 am tomorrow and slowly shifts to rain through the day.  Moderate to heavy rain isn’t expected to really start cranking until late tomorrow night into Wednesday morning.  An update on timing and intensity will be posted later today with fresh data.  

 The Long Range:  The warm/rain event ends on Thursday with cooler air and snow showers filling in.  Snow showers are likely to continue into the weekend.

Precipitation Ending at 4am: Today 24hr water = .10 Snow = 0-1 Tomorrow’s 24hr water =  1 snow =  2-5 Trend and Timing: Light snow starts after 2am tomorrow changing to rain through the day.

24hr temperature ending at 4 am tomorrow:  Low:  10    High:  30 Freezing level: +-4000 Trend and Timing:    Freezing levels west of the crest will peak near 4000’ today, east flow will likely hold pass level temperature at or below freezing through the night.

24hr Winds (mph) ending at 4 am tomorrow: Base:  0-5 E Ridge Top: 5-10 ESE shifting SW Trend and Timing: Pass level east flow should hold until early tomorrow morning.  SW flow aloft shifts to SW with the passing of the front early tomorrow morning.

jM