Wednesday, January 28, 2015

What Will Thursday And Friday Bring?

First - the showers that developed after 5 am MST yesterday morning ended up producing 0.04" or more at 31 ALERT stations (~ 30% areal coverage). The max amount measured fell at Mt. Lemmon with 0.59". Here at house we had 0.08", making total for the event 0.10".


It remains very moist over the eastern Pacific, and model forecasts continue to advect this moisture from low-latitudes into the Southwest, setting up a significant weather event for Thursday and Friday. The water vapor image above (13 UTC this morning, January 28th) shows this moisture strung out south-to-north along 120 degrees W. The blended PW analysis from CIRA for the same time (below) shows a broad plume of high PW (values of 2+ to over an inch west of San Diego) extending from the tropics to north of 30 degrees N.



I am just going to show some forecasts from the 06 UTC run of the WRF-NAM at Atmo. The northeast blizzard of past two days illustrated full-well that too many models can lead to overload in the system, with erratic forecast outcomes. The no-show blizzard at Philadelphia and New York City are getting much media attention, while record snow amounts fell in parts of Massachusetts.

The forecast above is on the 5.4 km grid and is for total precipitation through 11 pm MST Friday night, the 30th. The model maximizes the coming storm over eastern Arizona and western New Mexico, producing some very large amounts. Forecast below shows amounts for the same period, but on the high-resolution grid (1.8 km grid spacing), with a large portion of eastern Arizona forecast by the model to receive over an inch - with some high elevation spots going over 5 inches. I don't immediately recall such a heavy precipitation forecast from the model. But, if such an event does occur, it would certainly be a significant storm to end the month.

The WRF-NAM keeps temperatures aloft fairly warm during the event, with very heavy snowfall totals confined to the White Mountains. But all this is two days out, so we'll have to watch carefully as this situation evolves.

Finally, the forecast soundings for TWC (bottom at 1 am on the 30th) gets PW up to amounts over an inch during Thursday night and then indicates some CAPE and possible thunderstorms on Friday afternoon.



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