Winter Weather in Maryland, December 11 to 12, 2016

Area Forecast Discussion
National Weather Service Pittsburgh PA
909 PM EST Sat Dec 10 2016

.SYNOPSIS...
Low pressure will bring snow later tonight through Sunday,
followed by mixed precipitation Sunday night, changing to rain
Monday. Much colder air arrives late in the week.

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.NEAR TERM /THROUGH SUNDAY/...
With 9pm update, delayed snowfall by another hour or two
considering latest HRRR/RAP/NAM model runs, upstream observations
and dry air observed in the local 00Z sounding. Although snowfall
accumulations had some minor changes made, they were insignificant
to overall trends. Previous discussion follows.

Temperatures will remain in the 20s overnight as a warm front
approaches with snow developing west to east mainly after
midnight. Generally an inch or so by sunrise with lesser amounts
across the far south, with slightly higher amounts toward the I-80
corridor.

Deepening low pressure heading toward the Great Lakes will
provide warm advection and lift for snow to continue Sunday with
best amounts north of I-70, with higher amounts north of
Pittsburgh where a winter weather advisory has been issued. Snow
will diminish in the afternoon across the far south and mix with
rain, as the warm front shifts north taking best lift and
moisture with it.

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.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
Highest snow totals were placed across the northern counties
where best lift and moisture will reside into Sunday evening and
the winter weather advisory will continue. As surface low shifts
north expect enough warming aloft to change precip over to rain
across the south, with a period of freezing rain possible north of
Pittsburgh and in the ridges. With less snow expected across the
southern ridges, no headline was issued at this time, with any
freezing precip not expected until Sunday night.

Still expect all precip to mix with or change to plain rain before
sunrise Monday, as southwest flow ahead of an approaching cold
front warms the column. Temperatures will then level off Monday as
the front sweeps east with rain and or snow showers ending.

An arctic front will then be approaching Tuesday with low chance
POPs for snow showers ahead of the front.

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.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
Upper troughing and cold W-WSW flow should persist across the
eastern CONUS through Friday maintaining the chance for lake
enhanced and upslope snow showers. Some accumulation is likely with
a 13+ degree temperature difference between the lake and 850hpa.
With  uncertainty in band placement, have just upped PoPs for the
likely locations through Saturday morning. A less amplified
pattern sets up for the weekend through early next week, with
several crossing shortwaves progged. Differences in the evolution
of these systems prompted the use of the superblend for much of
this timeframe. Much below average temperatures are expected to
moderate by early next week.

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.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
VFR / high MVFR conditions will deteriorate early in the morning
as snow showers develop ahead of an approaching warm front.

Conditions will quickly fall to low MVFR and IFR in snow with some
improvement at the terminals from BVI/PIT/AGC southward by midday
as drier air works in in the lower levels. Sunday night
precipitation will start up again and IFR conditions will return as
the warm front begins to lift over the forecast area.

.OUTLOOK...
Restrictions are likely to continue through Monday, returning again
Wednesday, with crossing areas of low pressure.

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.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...None.
OH...None.
PA...Winter Weather Advisory until 4 AM EST Monday FOR PAZ007>009-
     013>016-022-023.
WV...None.

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