Area Forecast Discussion
Issued by NWS State College, PA

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148 FXUS61 KCTP 180156 AFDCTP Area Forecast Discussion National Weather Service State College PA 956 PM EDT Mon Jul 17 2017 .SYNOPSIS... A weak front will push into the central mountains and hang up over eastern and southern parts of the state tonight and for Tuesday. High pressure slides into the Ohio Valley on Tuesday, but another front will move down from the north and stall over the region for the latter half of the week. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
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Baroclinic zone laying down across central PA late this evening and still maintaining for the time being isolated to scattered coverage of showers and storms from the Laurels through the ridge and valley region of central PA. Some heavy downpours are still occurring over Somerset and Bedford Counties, but recent radar trends show cells weakening substantially elsewhere. Updated pops to focus highest POPs within the stalling frontal zone. Expect most activity to dwindle by or shortly past midnight. Areas of fog a good bet in the SE and perhaps the valleys of the north. Cooler mins expected northwest mountains where drier air seeps in...with mid 50s expected there. Mins across the remainder of central PA will range through the 60s...with lower 70s over portions of the lower Susq...and still uncomfortable humidity away from the NW mountains.
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&& .SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/... Additional storm will flare up again during the day heating. But, severe is not expected, with both shear and PWATs lower than today. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/... Weak surface ridging and partial clearing should result in areas of fog Tuesday night into Wednesday morning. Wednesday into Wednesday night still looks like the driest 12-24hr stretch during the long term period. 17/12z medium range models depict a general east-southeast shift of the upper level ridge initially centered over the Central U.S. Fast west-northwest flow aloft on the northern periphery of the upper ridge will reside over the area into the weekend. The evolution of convection-producing waves within this belt of westerlies is depicted differently within various models and specifics such as timing and location will depend on details not well resolved until the very short term time frame. That said, the later periods will show a broadbrushed, redundant 30-50 percent POP with refinements expected at closer ranges. The other concern is for a period of hot/humid conditions across the Lower Susquehanna Valley with blended guidance showing at least 2 days of 90+F max temps with max heat index potential approaching 100F. The heat risk was added to the HWO. The hot temperatures should be eroded from the NW with time as the frontal boundary gradually sinks to the south in response to mean troughing developing late in the period. && .AVIATION /02Z TUESDAY THROUGH SATURDAY/... Early threats for IFR will be from TSRA in IPT and MDT/LNS. Then the diurnal heating will be lost and just a few TSRA/SHRA will linger into the late evening. Fog may become a problem where the rain has fallen, but also in the northern valleys. Have mentioned fog just about everywhere, but confidence is low away from MDT and LNS. Additional storms will fire up during the day on Tues, and restrictions are possible. .OUTLOOK... Wed...No sig wx. Thu-Fri...Sct tsra impacts, esp NW. Sat...no sig wx && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Dangelo NEAR TERM...DeVoir SHORT TERM...Lambert LONG TERM...Steinbugl AVIATION...Dangelo

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