Area Forecast Discussion
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FXUS61 KPBZ 171730

Area Forecast Discussion
National Weather Service Pittsburgh PA
130 PM EDT Sat Mar 17 2018

Crossing low pressure will spread a light wintry mix of precipitation
along and south of Interstate 70 this morning.


light snow/sleet associated with the weak opening low pressure
system will pull quickly to the east this afternoon. With echoes
diminishing and reports of icing not materializing, will opt to
end the Winter Weather Advisory everywhere. A few pockets of
freezing rain may still occur in the highest elevations, but the
extensive icing threat has diminished.

What is left of the precipitation associated with the passing
shortwave trough will be gone by 3Z. Any snow or wintry mix will
be less very light and not cause any disruption. Cloud cover
will be the forecast challenge for the near term and how quickly
to the clouds depart overnight. Moisture profiles below H8
illustrate drying resulting from weak subsidence after 6Z from
north to south. Given boundary layer flow is around five knots,
slower departure from the mountains seems prudent.

A splendid day Sunday with wall to wall sunshine area wide. With
little mixing we won`t realize full sun temperatures.  Most
locations will make a run at 50 save for the higher elevations and
north of I80.


Its still winter on the calendar and in the forecast. Low
pressure which in the past few runs has continued to trend a
little farther south will bring accumulating snow to the
mountains of West Virginia and western Maryland. There are still
details to resolve with ptype. With inverted trough developing
on windward side of the Appalachians, look for warm air to surge
northward allowing column to climb above freezing for lower
elevation locations in northern West Virginia. The big question
with these setups is how far north will the warm air reach?
Typically, higher resolution NAM does a good job but trends
farther north with time. For this forecast package, brought rain
into far southwestern Pennsylvania by 6Z Tuesday. Would not be
surprised to see ptype to transition to all rain as far north as
I-70 during the overnight hours.

Farther to the east in the mountains, BUFR soundings point to a warm
layer aloft which yields a short period of a wintry mix in the
higher terrain.  With southeast winds ushering in reinforcing shots
of cooler air believe most of the time it will be snowing. Modest
isentropic upglide between 290-300K and a column that is nearly
saturated in the favored snow region support several inches of snow.

The hazardous weather outlook has been maintained for potential
winter weather advisories or winter storm watches. However since its
5th period the earliest a winter storm watch could be issued would
be Sunday.

Energy transfers to the coast rapidly Tuesday morning ending over
locations outside the mountains by 15Z.  With lingering
northeasterly flow light snow will continue as the column will cool
to support all snow.  H8 temps by 0Z Wednesday collapse to -5C. With
the trough continuing to dig clouds will hold through the day
Tuesday into Wednesday.  As winds switch around to the north-
northwest expect snow showers to continue across West Virginia and
Maryland most of Tuesday night into Wednesday.  Any accumulation
in this time frame will be a few inches at best.

Temperatures will be below normal the entire short term with clouds
and continued cold advection.  Normal highs this time of year run in
the upper 40s to lower 50s.  Most will be lucky to reach the mid 40s
with mid 30s well north of I-80 and in the mountains.


- Where`s spring?
- Below normal temperatures
- Active weather regime persists

Deep cyclonic flow aloft with full latitude trough in place across
the eastern CONUS dominates the long term.  Residual moisture in the
mountains of West Virginia and Maryland could yield snow showers,
but no significant accumulation expected Wednesday night.

A brief break in the action Thursday through Friday night with
surface high pressure in control.  Mid level heights remain two
standard deviations below normal and with a northerly low level
trajectory, H8 temps continue to be subzero across the region. A
transitory ridge crosses Friday before yielding to an approaching
warm front Friday night.  Would not be surprised if the timing holds
for temps to rise during the overnight hours, especially in eastern
Ohio due to increased cloud cover and pressure gradient.  For the
hollows of West Virginia and southwest Pennsylvania, a lower
probability exists of that occurring.

Precipitation type could be a concern at the onset Saturday morning
if timing holds.  Long range ensembles for the moment reside in good
agreement.  With the cyclone track well to our west, it won`t be a
heavy QPF event so impacts should be minimal.  Did not get to fancy
in the grids at this juncture with just a rain/snow mix. Saturday
will be the warmest day of the extended as southerly winds finally
return, however it will be at the expense of clouds and
precipitation thus it won`t be that much above normal.  Overall for
temps used the superblend with a little bit of the raw consensus


Light wintry mix will continue, mainly south of I-70 through the
early evening. Much drier air is ultimately winning, however,
and the lower ceilings just are not materializing. If any
terminal drops to MVFR this afternoon, it would likely be MGW
as the deeper moisture pools there. Otherwise VFR conditions
will be established through the duration of the forecast period.
The one slight exception to this would be in some light patchy
fog that could develop in FKL under clear skies.

Winds will generally remain light and variable through the

OUTLOOK... Restriction potential returns with low pressure Tue
and Wed.




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