Raging East Winds.... And Another Wintery Event?

Hey everyone... Well it's the early morning hours of the second day of 2013 and our weather (at least on the east side of town) is and has been active. My snow forecast was on point for some areas (even underdone!) and in others it busted a bit. SW Washington, particularly parts of Vancouver and points North were the winners with this, 2 inches was about the max but road conditions were affected, so I feel like the forecast did pretty well as the low pressure system pivoted and allowed for steady precip over a small area. It was a well modeled event!

Onto our current situation... The east wind is howling with a pressure gradient of -10mb from Troutdale to The Dalles. Here's what the NWS said about gradients that high in their AFD..

IN ANY EVENT...A KTTD-KDLS GRADIENT OF -10 MB IS A TRIGGER POINT FOR

HIGH WIND WARNING CONCERNS. ANOTHER RULE-OF-THUMB IS THE 7-8 MPH PER
MB FOR MAXIMUM GUSTS. THUS...70-80 MPH GUSTS SEEM REASONABLE IN
THE EXIT REGION OF THE GORGE AND THE NOTORIOUS WIND-PRONE SPOTS JUST
ABOVE THE GORGE. FOR INSTANCE...EXPECT GUSTS OF 90 TO 100 MPH AT THE
VISTA HOUSE DURING THE PEAK PERIOD...

Both a high wind warning for the Western Gorge and a Wind Advisory for the East Metro are currently in affect.. In reference to the previously mentioned gradient, here's what it's currently looking like.

Latest models put the gradient at its peak this morning around -11 to -12, so it will intensify. Crown point has seen multiple 80mph gusts, and several Troutdale locations are approaching 60. Also seeing close to 50 around here (NW Gresham) and wind has become much more sustained in the last hour or so. I fully expect a gradient around -12mb, which should yield the following gusts...

Crown Point 90-100mph (100+ on the stairs)

West Gorge (Areas under High Wind Warning) 65-80mph

East metro (Gresham, Wood Village, Troutdale, Fairview, East Portland) 55-70mph

All in all, if you live east of 205, good luck sleeping... 

Now onto our other point of interest with this forecast... When we have east winds of this strength, the first weather system following it is a tricky forecast, and this is no different. We have a very small area of low level cold air with a steep temperature inversion currently. As this system moves in Thursday morning, there should be a melting layer (column of above freezing temps) followed by a freezing layer (column of sub freezing temps) below it. This is why I believe Freezing Rain, rather than Snow will be an issue. Here's a 4km sounding (Dew Point in Green, Temp in Red) for my location on Thursday morning...

Notice the large disparity in Temp/Dewpoint around the 700mb level on down? This should allow for very nice evaporative cooling with such dry air, and normally would aid snow... But with the inversion visible on this sounding (warmer at 850-900mb than surface) the precip will likely thaw in the atmosphere , and if it hits as modeled in the morning, will refreeze on the ground icing everything over. I expect the NWS to issue either a ZR advisory or a Winter Weather Advisory or both... I will post more about that tomorrow as data becomes available.

An active start to 2012 !
Josh