Sunday, December 13, 2015

Heavy Frost here This Morning

A touch of snow visible this morning from the house at top and at Kitt Peak looking south just above. However, there is quite a bit of accumulation at the General Store up in Summerhaven, as per view below.

Yesterday proved to be more active than the models had forecast with showers continuing off and on into the afternoon. Across the ALERT network precipitation (of 0.04" or more) during the day (5:00 am to 5:00 pm) occurred at 71 of the 93 sites (~75% areal coverage). Here at the house we had an additional 0.07", making total for event 0.41".  There was a bit of graupel mixed in during a shower just before noon. Plot above shows daytime precipitation for the southeast sector of the ALERT network, where amounts were around a quarter of an inch or more - the Empire site is on the peak near the NWS radar and most precipitation there may have been snow.

There is heavy frost here this morning and low appears to have been 28 F - the 8th hard freeze in this part of town this season (coldest at house has been 23 F on December 2nd). It seems like the Winterhaven Festival of Lights (which began this weekend) acts as a storm magnet, pulling in cold and damp weather around Christmas almost every year.

The GFS ensemble plumes are now focused on the next event, forecast to occur during the day tomorrow, as another 500 mb short wave digs into the Southwest. The model forecast is again 100% of the members and again amounts are light ranging from less than a tenth to around a quarter of an inch at the airport (TUS). At this time there is a nice atmospheric river moving south with this system ( MIMIC PW below from CIMMS at Univ. of Wisconsin is for 10 UTC this morning).

The 06 UTC forecast from the WRF-GFS run at Atmo is currently forecasting tomorrow's event to be mostly over the mountains, with only some very light amounts at low elevations.

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