Area Forecast Discussion
Issued by NWS State College, PA

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260 FXUS61 KCTP 300310 AFDCTP Area Forecast Discussion National Weather Service State College PA 1110 PM EDT SUN MAY 29 2016 .SYNOPSIS... 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. Previous: 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. Previous: 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. && .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 80s. && .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 normal. 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. && .AVIATION /03Z MONDAY THROUGH FRIDAY/...
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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 vsbys. 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 13Z. 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. OUTLOOK... Mon...Sct tsra impacts poss east. Tue-Thu...No sig wx. Fri...Chc of showers and thunderstorms with cold front.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...DeVoir NEAR TERM...Dangelo/DeVoir SHORT TERM...DeVoir LONG TERM...Martin AVIATION...DeVoir/Ceru is the U.S. government's official web portal to all federal, state and local government web resources and services.