Friday, September 12, 2014

Strong Cold Front Over Plains And Northern Rockies

An unusually strong, early season cold front is pushing southward along the Front Range and into the Southern Plains. This front brought the first snow of the season to some locations in Wyoming and along the Colorado Front Range. The NAM analysis at 12 UTC for 850 mb (above) shows the strong temperature gradient along the front, which extends into northeastern New Mexico. Visible satellite imagery from 7:15 am MST (below) shows the extensive cloud mass along and behind the front. The 850 mb analysis also indicates that there is a tropical disturbance over the western GoM and that a band of strong easterly winds along the northern periphery of this disturbance reaches westward to the New Mexico Boot Heel. A broad and amorphous inverted trough stretches along the west coast from southern Mexico north to Washington state - certainly a very complex large-scale pattern.

Graphic above shows detected CG flashes for 12-hours ending at 7 am MST this morning. Of note is intense storm activity over the southern GoC; widespread thunderstorms with the GoM disturbance; and thunderstorms along the Plains cold front. The early run of the WRF-NAM at Atmo continues to forecast an extended period of strong easterly winds in southeast Arizona, as the Plains cold front backdoors westward across the Continental Divide. The WRF forecast of 10-m winds below is valid at 9 pm this evening.

The NAM model from this morning forecasts the frontal zone to be nearly to the Colorado River by tomorrow morning (above); and the WRF-NAM forecasts strong winds to continue through the day tomorrow and to affect all of southern Arizona.  The WRF also forecasts isolated thunderstorms for parts of Pima County today, with more extensive coverage across Cochise County - forecast below is for total precipitation through 5 am MST tomorrow morning.

To the south, Tropical Storm Odile has remained nearly stationary during the past 24-hours. The NHC forecast for Odile, once she decides to begin moving northward, is similar to yesterday's forecast. So, many interesting weather features over and near Arizona for the coming few days.

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