An upper level closed low near Baja and a backdoor front combined to bring considerable precipitation to New Mexico during the day and overnight period of March 19, 2015. Ample moisture surged northward over New Mexico ahead of the closed low, and precipitable water as measured by the soundings at Albuquerque, NM and El Paso, TX tied for the fourth highest value for March since 1950 (at both locations). Additional support for this event came in the form of a back door cold front which raced through the eastern plains of New Mexico during the day on March 19. Because of warm temperatures, Winter Storm Warnings (blue) and Advisories (yellow) were limited to the New Mexico northern high terrain including the Jemez Mountains, San Juan Mountains and Sangre de Cristo mountains, as shown in the figure below.
Two NESDIS Snowfall Rate (SFR) products were available for review the morning following the event. The first is from 0353Z on 20 March 2015, or about 10pm MDT on the evening of March 19, and is shown in the figure below with the 04Z surface observations. The east to northeast flow in the eastern half of the state indicates the progress of the back door front. Most locations in central and eastern New Mexico are reporting rain, including Raton (KRTN) just to the east of the active snow area in the SFR product. Angel Fire (KAXX) just to the south of the area is reporting snow. At this time, the SFR product appears to do a good job in distinguishing between rain and snow despite the fact the Angel Fire is just outside the SFR active area.
The 0.5 reflectivity mosaic at the same time illustrates beam blockage that impacts the area east of Albuquerque, but also the limited radar coverage in northern New Mexico, though there are weak echos associated with the snow report at KAXX as well as the rain at KRTN. Also note convection in western Texas – earlier in the evening one-inch hail was reported in eastern New Mexico. This is an example of the interesting regimes that can impact our CWA in that we can have winter weather warnings and severe weather at concurrent times.
Similar graphics are shown for 0855Z, or 3am MDT, on the morning March 20th. Activity has weakened considerably and the WSW is about to be cancelled. Still, light snowfall rates are depicted by the SFR over the northern high terrain. The metar observation at Angel Fire, KAXX, is still reporting snow.
The 0.5 reflectivity mosaic illustrates that the only isolated precipitation continues over western and central New Mexico, with no returns over the northern high terrain.
In the image below, the 0855Z SFR product is combined with the awips hi-res topography map to illustrate the agreement with the SFR and the highest terrain of the southern San Juan and northern Sangre de Cristo Mountains in northern New Mexico.
One of the frustrations with evaluating the NESDIS SFR product is that consecutive products can be separated by long periods of time, in this case by 5 hours. However, substantial snow accumulations were reported in the Sangre de Cristo mountains – from 6 to 19 inches. Thus the area depicted by the SFR product seems to be fairly accurate, but the evaluation is rates is more difficult.
In addition to snow, widespread rainfall reports ranged from one quarter of an inch to one inch. Early this morning, the following DOT report was posted – the combination of rain and snow resulted in rock slides on at least two roads in northern New Mexico.