SPC MD 2172


MD 2172 Image

Mesoscale Discussion 2172
NWS Storm Prediction Center Norman OK
0206 AM CST Fri Nov 29 2019

Areas affected...Portions of northern and central AZ

Concerning...Heavy snow 

Valid 290806Z - 291400Z

SUMMARY...Heavy snow, with rates in excess of 2" per hour, will
likely occur for at least a few hours above 4000' this morning.

DISCUSSION...A large upper low over CA will continue moving slowly
eastward early this morning. Strong large-scale forcing will
overspread AZ as a 60-70+ kt mid-level southwesterly jet moves
across the Southwest. Plentiful moisture at low/mid levels
originating from the sub-tropical Pacific will be lifted through
both isentropic and orographic processes across northern/central AZ,
focused generally along/near the Mogollon Rim. Cooling of
mid/upper-level temperatures will occur from west to east over this
region as the upper low moves eastward, and a transition from rain
to snow will occur above the wetbulb zero height, which should be
around 4000-4500 feet per model forecast soundings. Given a deep,
saturated profile through the entire dendritic growth zone and the
very strong lift expected, enhanced snowfall rates of 2-3 inches per
hour appear likely, with locally higher rates possible. These higher
rates should be focused in a relatively narrow band of precipitation
that appears to be organizing over western AZ at 08Z, and they
should persist for at least a few hours as the band develops
eastward. Strong/gusty surface winds will also reduce visibilities
to near or below 1/4 mile, with near-blizzard conditions possible.

..Gleason.. 11/29/2019

...Please see www.spc.noaa.gov for graphic product...


LAT...LON   34671345 35181380 36001381 36401342 36611268 36491193
            35891169 34931115 34481017 34170931 34010908 33540908
            33250941 33511026 33961156 34351271 34671345 

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