SPC MD 65

MD 0065 CONCERNING HEAVY SNOW FOR SIERRA MOUNTAINS

MD 0065 Image


Mesoscale Discussion 0065
NWS Storm Prediction Center Norman OK
0318 PM CST Sun Feb 03 2019

Areas affected...Sierra Mountains

Concerning...Heavy snow 

Valid 032118Z - 040315Z

SUMMARY...Heavy snow, with rates of 1 inch per hour and locally
exceeding 3 inches per hour at times -- especially at higher
elevations, will develop into the evening.

DISCUSSION...Strong, moist flow into a cooling troposphere is
supporting efficient snow production across much of the Sierra
Mountains. This large-scale pattern is expected to remain in place
through the evening as strong deep-layer ascent increases in
response to the next cyclone moving southward along the California
coast. Increasing ascent is already evident on water-vapor and
infrared satellite imagery, as well as in radar imagery, across the
Sacramento Valley as cloud tops have cooled and banded/cellular
echos have developed. As the lower troposphere cools, snow levels
fall, and these cellular features move into the Sierras, snowfall
rates briefly approaching 3 inches per hour may occur at elevations
as low as 6000-7000 feet. Strong winds will accompany this heavy
snow resulting in blizzard conditions at times.

Although snow will continue well into the overnight snowfall rates
may relax a bit overnight before picking up in intensity again
tomorrow ahead of the next short-wave trough embedded within the
larger-scale trough.

..Marsh.. 02/03/2019

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

ATTN...WFO...REV...HNX...STO...

LAT...LON   37431950 38332036 39532113 39712048 38901987 37781883
            37431950 

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SPC MD 61

MD 0061 CONCERNING HEAVY SNOW FOR EASTERN PENNSYLVANIA INTO SOUTHEASTERN NEW YORK…NEW JERSEY AND ADJACENT PORTIONS OF THE NORTHERN MID ATLANTIC AND SOUTHERN NEW ENGLAND

MD 0061 Image


Mesoscale Discussion 0061
NWS Storm Prediction Center Norman OK
1010 AM CST Wed Jan 30 2019

Areas affected...Eastern Pennsylvania into southeastern New
York...New Jersey and adjacent portions of the northern Mid Atlantic
and southern New England

Concerning...Heavy snow 

Valid 301610Z - 302015Z

SUMMARY...A brief burst of heavy snow, strong wind gusts and reduced
visibilities may accompany the passage of a cold front this
afternoon, perhaps affecting much of the Greater New York City
metropolitan area during the 2-4 PM EST time frame.

DISCUSSION...The leading edge of stronger lower tropospheric cooling
(centered around 850 mb...where temps falling from roughly -15 to
-30C), now surging east of the Allegheny Mountains, is forecast to
continue eastward into western New England and the northern Mid
Atlantic region through 20-22Z.  Model forecast soundings suggest
that is being accompanied by increasing boundary layer
destabilization supportive of deepening convective development, with
tops likely to approach 10,000+ feet, particularly across parts of
eastern Pennsylvania and central/northern New Jersey into
southeastern New York late this afternoon.

Frontogenetic forcing appears to be supporting a narrow, but
sustained, evolving band of convection.  This is likely being aided
by lift within the exit region of a 110-130 kt cyclonic 500 mb jet
streak forecast to nose across the northern Mid Atlantic, lower
Hudson Valley, and southern New England by late this afternoon.

Given the cold thermodynamic profiles, including a layer supportive
of large dendritic ice crystal growth, guidance is suggestive that
the convection may be accompanied by a burst of heavy snow rates
around or in excess of 1 inch per hour.  It appears this may last
only 15 to 30 minutes at any one location, but it may be accompanied
by fairly strong surface wind gusts in excess of 30 kts, and sharply
reduced visibilities.

..Kerr.. 01/30/2019

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

ATTN...WFO...BOX...BTV...OKX...ALY...PHI...BGM...CTP...LWX...

LAT...LON   40187685 41577615 42637568 43557345 42817280 42297262
            41427249 40227382 39647578 39647711 40187685 

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