Scientific Forecaster Discussion
fxus61 kpbz 190033
Area forecast discussion
National Weather Service Pittsburgh PA
833 PM EDT Fri Oct 18 2019
high pressure should provide dry conditions through Saturday. Low
pressure may bring rain to areas southeast of Pittsburgh Saturday
night into Sunday.
Near term /through Saturday/...
Evening update: no major changes have been made to the forecast.
Previous discussion: an upper-level low is expected to track
northeast, out of New England, and a disruption to deep northwest flow
across our region will result. With a drier air mass moving into the
Ohio River valley, clouds will continue to dissipate. With light wind
and radiational cooling, frost is likely areawide. Frost will be
less likely near the warm major rivers, where steam fog may prevail.
Short term /Saturday night through Monday/...
Saturday will feature plenty of sunshine as the surface high moves
across New England. Some high clouds will show up during the
afternoon on the outer fringes of the extra-tropical low moving into
the southeast Continental U.S.. low-level warm advection will help to push
afternoon high temperatures.
The aforementioned low will lift through the Carolinas with an
associated shortwave Saturday night and Sunday, moving offshore by
00z Monday. Models still have some minor disagreement on the
westward extent of the precipitation shield, with the GFS the least
aggressive with its coverage as compared to the NAM/ECMWF. Will
continue to follow the general model consensus, keeping pops mainly
to the south and east of Pittsburgh.
A return to surface high pressure/flat ridging aloft is then
pictured for Sunday afternoon and night, with dry weather and a
general lack of cloud cover. Southwest flow will become
reestablished, and above-normal temperature will continue.
Long term /Monday night through Friday/...
a trough will lift across the upper Midwest on Monday, and into
Ontario on Tuesday. The front associated with this low will tap into
the tropical plume that Nestor will lend to the northeast. This will
result in warmer temperatures and higher dewpoints than we've seen as
The surface front is timed for a Tuesday morning passage, with
likely pops coincident due to sufficient moisture, frontogenetic
forcing, and ample vorticity advection.
Despite increased precipitable water values and saturated model soundings, the
forcing doesn't look to linger long enough to warrant any flooding
concern at this time.
Behind the frontal passage, an abrupt temperature and moisture
contrast with dry conditions Wednesday through early Friday.
Aviation /01z Saturday through Wednesday/...
building high pressure will lead to general VFR and light wind
through Saturday, marred only by shallow fog at terminals nearest the
restrictions are likely with a Monday night/Tuesday cold front
approach and passage.
Ohio...frost advisory from 2 am to 10 am EDT Saturday for ohz039>041-
PA...frost advisory from 2 am to 10 am EDT Saturday for paz020-021-029-
WV...frost advisory from 2 am to 10 am EDT Saturday for wvz001>004-012-