Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 292341

Area Forecast Discussion
National Weather Service State College PA
741 PM EDT SUN MAY 29 2016

An upper level trough will push across the region tonight and
Monday. Tropical moisture lifting northward from the Mid Atlantic
region will feed an increasing chance of showers and thunderstorms
over southeast Pennsylvania overnight. A ridge of high pressure
will build east into Pennsylvania for midweek. A slow moving cold
front will likely push into the region from the Great Lakes by
late in the week.


HRR spot on tonight with drying and stabilization happening on
time. Much of the area will be dry/not-raining in less than an
hour or two. It is barely raining in the SE despite the look on
the radar/mosaics. Thunder looks like it is done. However, we will
hold onto just a slight chc down in the far SE where the enhanced
rainfall is expected overnight. So far, KDCA has received only
0.25 inches. Of course, the overnight rain will be formed by
mostly tiny tropical droplets. Still, the inch or so of rain in
Lancaster should not overflow any banks since everything is
growing and waterways are slightly below average flows for
Memorial Day weekend.

Near term is panning out as upper ridge continues
to slide east of the region as an upper trof swings towards the
western GLAKS from the upper midwest. Deep plume of subtropical
moisture off of the southeast Atlantic coast is being directed
northward between now T.D. Bonnie (downgraded at 8:00 AM this
morning) and aforementioned 5H ridge...which models pool from
northern Virginia to the Chesapeake Bay and southeast piedmont
region by late this afternoon.

Isolated to scattered slow moving convection fired along the
Allegheny plateau early this afternoon...with some local heavy
rainers producing 1-2"+ in spots. The spine of the Allegenies
and the Susq River Valley will the focii for locally heavy
rainfall...the latter waiting until deeper subtropical moisture
arrives this evening and late tonight.

By late this evening expect two main areas of rainfall...the first
associated with the upper trof approaching from the eastern GLAKS
and OH Valley and the 2nd over the southeast...where PW surges
over 2 inches along and south of the Mason Dixon line and slow
moving 5h shear axis maintains lift overnight into Monday morning.

Successive HRRR runs have shown a distinct back edge to the precip
reaching towards the Lower Susq River Valley by 09z...and
extrapolated further could mean that the balance of the day is
mostly dry after this activity exits. Still expected isolated to
sct coverage of diurnal activity in the heat of the day...but by
and large the bulk of the rain should come tonight...and some
areas will see well over an inch or rain along and east of I-81.


After morning activity slides east of the Susq River Valley...
most of Memorial Day is now appearing dry...although isold to sct
coverage of diurnally driven shra/tsra is still expected.
Guidance continues to indicate fair amount of mid/high cloudiness
streaming north from remnants of td bonnie circulation over
eastern PA...while increasing amounts of sun will be found rather
west over PA. Highs should range from the upper 70s to the mid


Looking at a nice break from the showers and storms from
later Monday into Wed. Temperatures still a little above

Expect some showers and storms later Thursday into Friday
with the next cold front. Some variation between the GFS and
EC at times on the large scale by the time I got
to Sunday...I adjusted the superblend pops a little...too
much detail for that far out. Regardless of detail...trend
is to a cooler and wetter pattern again. Other issue is hints
that some remains of Bonnie stay behind under the upper level
ridge until the next cold front moves in by Friday.

Main change to the package was some minor adjustments.


A trough of low pressure will push across the region late today
into Monday. VFR coonds will prevail this morning. Increasing
cirrus is expected central and western areas, as high-level
moisture is drawn northward from TD Bonnie. Daytime heating/
destabilization will be enough to lead to isolated/scattered
mainly afternoon convection confined mainly along the spine of
the Alleghenies.

Through much of the afternoon, reducing conditions should be
contained to the western and poss central TAF sites. As impacts
from approaching trough move eastward this evening and especially
tonight, the eastern TAF sites will likely see periods of MVFR
develop in a moderate rain with isolated TSRA as slight
connection to tropical system develops.

A chance of showers and isolated TSRA continues into Monday mainly
in eastern third, followed by high pressure and more settled
weather building into the region through midweek.


Mon...Sct tsra impacts poss east.

Tue-Thu...No sig wx.

Fri...Chc of showers and thunderstorms with cold front.




NEAR TERM...Dangelo/DeVoir
LONG TERM...Martin
AVIATION...DeVoir/Martin/RXR is the U.S. government's official web portal to all federal, state and local government web resources and services.