Scientific Forecaster Discussion
fxus61 kpbz 241048
Area forecast discussion
National Weather Service Pittsburgh PA
548 am EST Sat Feb 24 2018
periodic rain chances will continue through Sunday. Conditions
should be dry for the beginning of the work week, with rain
returning to the forecast by Wednesday night.
Near term /through tonight/...
steady light to moderate rain showers are beginning to move into
our southern zones, ahead of a shortwave trough poised to move
through later today. This wave will ride along a surface frontal
boundary that has tried to clear the forecast area, but has
thusfar been denied. A surge of warm and moist air through West
Virginia will stall the boundary near the Mason-Dixon line
through much of the day. As the wave moves west to east over the
area, rain showers will spread areawide, but the primary focus
of the rain will be south of Pittsburgh. Hi-res models in
considerable agreement with the evolution of this wave through
the afternoon, and were relied on heavily.
Given the surge of pwats above 1", a strengthening low-level
jet, and deep warm cloud layer, rain production should be
efficient. These locations will need to be monitored for any
localized flooding problems. The wave will pass east this
evening, and a another brief lull in rain is expected. Pops were
constructed to be a bit more deterministic with this trend in
mind. Showers and the cold front just south of the area will
keep our highs a little lower than the last few days, but still
The aforementioned front will lift north tonight as a warm
front. Strong moist and warm advection will fuel moderate to
heavy showers lifting north through our forecast area. The axis
of this rain will set up north of the axis of today's rain,
giving more spatial dispersion of qpf over the entire area. The
result is a slightly lower concern of areal flooding over
any one specific area. Still, soils are plenty saturated and an
additional 1-1.5" of rain through tonight may be enough to
cause some flooding problems. The areal Flood Watch will
Short term /Sunday through Tuesday/...
the period of wet weather comes to an end Sunday as the cold
front finally sweeps through the forecast area. This will usher
in much drier air that will lead to clearing and increased
sunshine through Sunday. Dry weather will carry into Monday and
Tuesday as high pressure builds in under nearly zonal flow
aloft. The increased sun Monday and Tuesday will keep
Long term /Tuesday night through Friday/...
dry weather established early next week will give way to another
disturbance near the end of next week. Models continue to show
great difficulty in handling the evolution of this next
precipitation maker. With much uncertainty, superblend was
utilized heavily in the construction of the extended and, in
general, pops were kept in the high chance or low likely range.
The trend in the forecast that has been a little more consistent
is a downward movement in temperatures over next weekend.
Aviation /12z Saturday through Wednesday/...
band of moderate to heavy rain will lift across this morning
across mainly northern WV and southwest PA, with IFR ceilings
and visibilities in the heavier rain. Otherwise, IFR/low MVFR
ceilings will be the rule in more scattered activity. Waves of
rain through tonight will keep occasional, hard-to-time IFR
restrictions in the forecast, with MVFR ceilings expected
outside the heavier rain. Low level wind shear will become a
concern overnight as a low level jet continues to transport
moisture into the area, maximizing the heavy rain threat.
restrictions are expected to continue into Sunday as a cold
numerous forecast points are already at action stages across the
2 successive disturbances over the next 36 hours will drop
rainfall amounts ranging from 1.00 to 2.00 inches across the
River flood watches may need to be converted to warnings.
Maryland...Flood Watch through Sunday evening for mdz001.
Ohio...Flood Watch through Sunday evening for ohz039>041-048>050-
PA...Flood Watch through Sunday evening for paz007>009-013>016-
WV...Flood Watch through Sunday evening for wvz001>004-012-021-