Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 200716 AFDCTP Area Forecast Discussion National Weather Service State College PA 316 AM EDT Thu Oct 20 2016 .SYNOPSIS... A weak cold front will stall south of the region allowing unsettled conditions will develop for the end of the week as a series of low pressure areas ripple up along the stalled front. Brisk and much colder weather will move in for the weekend. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... It will continue mild overnight as low level flow quickly turns southerly ahead of a wave of low pressure that will be approaching from the midwest. Increasing warm advection will help bring about an increasing chance for rain the deeper into the overnight we get, with the best chances for rain by morning being over my western and northern zones. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM FRIDAY/... The first in a series of surface waves will enter Pa by Thursday afternoon. The surface pattern will be rather complex by that time with a low and cold front moving into the western part of the state, and a warm front extending east before dog-legging down through the Central Mountains and east to the coastal plain. The forecast surface based LI`s depict this cool air damming scenario lasting at least through mid afternoon before we mix out and see the warm front become established to the NE of the region. This also complicates the rain forecast with the best chance of rain for the first half of the day looking to be over NWRN Pa associated with the increasing frontogenetic forcing under the strengthening right upper jet entrance region. To the east we should see a more misty/showery rain overrunning the wedge of cooler air over most of central and eastern Pa. As we see the warm air progress north we could actually end up with another very warm and rain free afternoon over much of the central and eastern part of the forecast area as the rain concentrates closer to the low and cold front over western areas. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... The models have converged significantly with the timing/strength of an amplifying upper trough moving into the Eastern U.S. over the next couple of days. Initial surface low development along a frontal zone over the OH Valley on Thursday will give way to a deepening low center that will elongate as it crosses the Central Appalachians and Mid-Atlantic States on Friday and interacts with another area of low pressure tracking northeast in the western Atlantic from the Turks and Caicos Islands. The full range of guidance shows strong low pressure consolidating and lifting toward New England as its trailing cold front pushes off the coast by Saturday morning. The amplifying upper trough will start to take shape on Thursday as it digs through Mid MS/TN Valley and eventually closes off, taking on a negative tilt moving through the Mid-Atlantic/Northeast States Fri-Sat. The right entrance region of 100+kt upper level jet should be in a favorable position to provide dynamical support and enhanced synoptic scale lift. Low level 850mb winds accelerate ahead of the surface low which helps to draw in precipitable water values +2SD above normal over Central PA into western NY. The deep layer upward vertical motion afforded by the upper level divergence and the sustained moisture flux convergence along the pivoting frontal boundary should result in 24-36 hour rainfall totals of 2-3 inches across northwest into north- central PA by Friday night. A colder and brisk/gusty northwest flow pattern will set up Friday night into early Saturday with wrap around/deformation precipitation on the backside of the low giving way to a cold advection lake effect/upslope shower regime focused downwind of Lake Erie and over the higher terrain of the Alleghenies/Laurel Highlands. Surface- 850mb temps will be marginally cold enough to support rain/snow showers Saturday (and especially Saturday night) over the NW mtns and Laurel Highlands with a low probability for a light coating of snow at the highest elevations. Some wet snow flakes or pellets may even be possible in the lee of the Alleghenies over the central ridges and valleys especially in heavier bands/pcpn rates. 25-35 mph wind gusts will add an additional blustery chill to below normal temps on Saturday. GFS/EC still show a fast-moving low diving through the Great Lakes into early next week. This system has low predictability given it weak state embedded within a progressive WNW flow aloft. Temperatures will trend noticeably colder/below normal by the weekend with highs easily 20-25 degrees colder than today. The roller-coaster up and down swing in temperatures is not uncommon for this time of year and will only continue as the calendar turns towards winter. Overall the pattern looks to stabilize into early next week with temperatures returning to normal for late October. && .AVIATION /07Z THURSDAY THROUGH MONDAY/...
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VFR conditions will continue over the next few hours. However a developing storm/frontal system over the Ohio Valley will spread low clouds and rain into the western mountains overnight...with more showery precipitation reaching the central mountains near dawn. Expect the conditions to deteriorate after 09Z with MVFR cigs and vsbys and IFR possible at UNV and MDT. Thursday will feature morning rain and showers, most widespread in the north and west, tapering to more showery activity before a larger scale rain event will bring widespread rain and flying reductions to much of the region Thursday Night and Friday. Once again, heaviest precipitation, and most significant reductions in conditions, will be across the west and north. Outlook... Thu-Fri...Rain and showers with widespread reductions in conditions, with lowest ceilings in the north and west. Fri...Widespread rain and restrictions in flying conditions. Sat...Scattered showers with restrictions NW. Brisk NW wind. Sun...No sig wx. Mon...Mainly VFR. MVFR with rain showers possible NW.
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&& .CLIMATE... Another new daily record maximum temperature was set at Harrisburg today. Here are the current records for 10/19: Harrisburg: 82 in 1945 (new record set 85) Williamsport: 82 in 1963 && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Gartner NEAR TERM...La Corte/Gartner SHORT TERM...La Corte LONG TERM...Steinbugl AVIATION...La Corte/Ceru CLIMATE... is the U.S. government's official web portal to all federal, state and local government web resources and services.