Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Pittsburgh PA
922 PM EDT Monday Jun 1 2015
an upper level low will nearly stall over the Ohio and Tennessee
valleys through midweek...with rainfall chances mainly south of
Pittsburgh. Temperatures will show a slow warming trend.
Near term /until 6 am Tuesday morning/...
at the moment...largest coverage of showers is actually across the
central portions of the forecast area. Showers across eastern Ohio
have been diminishing in coverage...although scattered showers are
now moving into southwestern Pennsylvania. Still expect that the
coverage that will manage to continue into the overnight hours
will be that associated with the low across Virginia that is
moving very slowly. Showers will continue to ride along the
Appalachians...and have kept likely probability of precipitation across
Garrett/Preston/Tucker counties tonight. Have gone with gfslamp
guidance for temperatures overnight...and considering the blanket
of clouds across the region...these values should not be much more
than 5 degrees below current readings.
Short term /6 am Tuesday morning through Thursday night/...
cutoff upper low will slowly drift across the Ohio and Tennessee
valleys during this period...and will slowly fill as it approaches
the Appalachians by Thursday. Models are in good agreement with
this thinking. At the surface...high pressure will be making an
eastward track to our north...before exiting the New England coast
on Thursday. This will help to keep the bulk of moisture suppressed
to our south.
Rain showers coverage will be decreasing during the morning as frontal wave
exits...with only the southeast ridges hanging on to isolated rain showers
into the afternoon. Another spoke of vorticity will rotate around
the upper low Tuesday night and bring an increase in coverage with
time..confined to areas southeast of pit through Tuesday night.
Scattered rain showers will then expand to an area south of a phd-lbe line
on Wednesday. All of this activity will be light. Despite moisture
content/precipitable waters increasing on Wednesday...southeast flow will add a
downsloping component which will help to suppress precipitation totals.
By Thursday...low level flow west of the ridges turns more southerly
as the upper low tracks to our south and a return feed sets up
behind the New England high center. This will allow better
instability to return...and shower chances are in the forecast County Warning Area-
wide. Also reintroduced thunder chances on this day with some
deeper cape profiles starting to show up on soundings. Activity
will diurnally decrease towards Thursday evening.
A slow warming trend will be seen in temperatures...with readings
getting back above normal by Thursday. Generally kept numbers in
line with model consensus.
Long term /Friday through Monday/...
another round of diurnal rain showers/thunderstorms and rain is pictured for Friday as the
upper low continues to degrade and lift out. A cold front will
approach later Friday night or Saturday. This may lead to a brief
break in the unsettled pattern but this is still uncertain...and
precipitation chances remain in the forecast for Sunday and
Aviation /01z Tuesday through Saturday/...
degraded conditions...including IFR ceilings...are expected to
continue through the night as boundary layer moistures remains
trapped in the wake of last nights cold front. A weak shortwave in
southwest flow aloft will also support light...but fairly
widespread showers with passage over the region tonight.
Shortwave ridging aloft may offer some improvement on Tuesday...but
MVFR ceilings are still expected to dominate the day and a
pessimistic overall outlook was retained.
Outlook.../Tuesday through Saturday/...
conditional restrictions are expected into late week as upper
trough remains entrenched over the eastern U.S.