Area Forecast Discussion
Issued by NWS State College, PA-- Remove Highlighting --
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FXUS61 KCTP 300310
Area Forecast Discussion
National Weather Service State College PA
1110 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.
.NEAR TERM /UNTIL 8 AM MONDAY MORNING/...
Precip is gone over the western 2/3rds of the area and only light
rain currently over the east. heavier cells sans thunder are
rolling up through MD and eastern VA and should get into Lancaster
Co by the middle of the night. Thus, all looks on track with QPF
of around an inch of basin average changed very little in that
area and timing really good. Some point amounts will likely be a
bit higher. Tropical Z/R QPE from the Legacy 88D algorithms is
about 2x as high as the Dual-Pol QPE. It is tough to tell which is
better at this point with just isolated points of heavier precip
not hitting any automated rain buckets. However, the precip over
the rest of the area should be light through the rest of the
night and spotty/scattered during the daytime on Monday. Good
news for those that want to get that parade or picnic in. Again,
almost no worry for flooding and if any they would only to the SE
of KMDT where some tropical enhancement to convection is possible.
But, those cells are moving 12-15kts NNE and training cells would
be the only thing that could make minor/isolated trouble. Temps
will be rather stable/steady overnight in the west and central
Co.s and just dip 5-6F in the east.
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 expected...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.
.SHORT TERM /8 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
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
.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
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 flow...so 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.
.AVIATION /03Z MONDAY THROUGH FRIDAY/...
-- Changed Discussion --The two biggest aviation concerns overnight is the weak
precipitation moving through the southeast, which has at LNS
caused IFR and lower CIGS, and the clearing over the western TAF
sites that has already brought BFD and JST at times down to IFR
Expect light rain with periods of MVFR vsbys and IFR CIGS possible
at MDT through 09z and LNS through 12Z. These areas will clear
slowly toward morning with light precipitation overnight. For the
other TAF sites another round of overnight reducing cigs/vsbys is
in store. BFD, JST and AOO all received varying amounts of
precipitation. Given clearing skies, light winds and overnight
lows that will bring low dewpoint depressions MVFR to IFR vsbys
with periods of IFR CIGS are possible especially between 09Z and
By 15Z, most reducing conditions should lift out. However tomorrow
will bring another chance of showers and isolated TSRA, 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.
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