Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 160147 AFDCTP Area Forecast Discussion National Weather Service State College PA 847 PM EST Mon Jan 15 2018 .SYNOPSIS... A weakening Alberta Clipper will track north of Pa tonight, and a secondary low will form south of the region Tuesday and lift northeast off the Mid Atlantic coast Tuesday night. Light snow will fall over much of central Pennsylvania through Tuesday night, ending over the southeast early Wednesday morning. A deep upper level trough will swing through the area later Wednesday, then be replaced by a building east coast ridge next weekend. && .NEAR TERM /UNTIL 7 AM TUESDAY MORNING/...
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Snow has started but is very intermittent - and light - over the west. All is on time, and no change to amounts for now. New 00z runs may have some helpful info in a bit, but consensus fcst appch still the best solution at this point.Temps doing OK, but some tweaks were made as the clouds are keeping things a tiny bit warmer. Prev... Low clouds remain banked over eastern third of PA, while a deck of mid and high clouds stream over central and northern sections. A break in the mid-high cloud deck has arrived over the west but will fill in this evening. Some light snow currently over the Ohio/PA border will swing towards my northwest zones by evening. Latest short range guidance continues to track the weakening clipper system north of the region tonight, producing a swath of light snow across western and central PA overnight into Tuesday morning with light amounts for most. Some upslope enhancement near the Maryland border may produce local Advisory amounts there from late tonight through late Monday morning, and a Winter Weather Advisory has been posted for Somerset to Franklin Counties for this in collaboration with WFO LWX. Fairly high snow to water ratios favor Advisory criteria snowfall in this area. Elsewhere, expect a little over an inch across the north central mountains by dawn, with little by morning across the southeast. However, some light snow may begin by 10z or shortly thereafter over the Lower susq River Valley, complicating the morning commute.
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&& .SHORT TERM /7 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/... Clipper will continue to fill while a weak secondary low tracking from the southern Appalachians to the Mid Atlantic coast, combined with frontogenetic forcing resulting from jet streak entrance circulation, could potentially produce several inches of additional accumulation across the southeast portion of the forecast area Tuesday/Tuesday night. Latest models and collaboration with WPC and surrounding offices gives us a long duration Advisory event, with 3 to 5 inches in a 24 to 30 hour period from 12z Tuesday through 18z Wednesday. Issued Winter Weather Advisory in collaboration with LWX, PHI and BGM. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
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Did up pops a little Tuesday night into the first part of Wed, as the upper lvl trough takes longer to lift out. Not really a big event, but a longer duration event. Still looking dry Thursday into Friday. Winds shift more to the west across the northwest on Thursday, thus more of a warm advection set up there. The coldest push of air is down the TN Vly on Wed. Temperatures by the weekend will be well above normal, as the upper lvl ridge builds. Took out rain and snow for Saturday. 00Z EC has next system so strong over the plains that the cold front gets push well east of the upper lvl system by late Monday. Went with a dry fcst aft this. This warm up not fcst to have dewpoints much above the lower 40s, thus not expecting a lot of heavy rain. More information in hydro section below.
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&& .AVIATION /00Z TUESDAY THROUGH SATURDAY/...
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An Alberta Clipper will swing southeast across the lower Great Lakes this evening into tomorrow. A thickening mid- deck across the state. IFR has spread through BFD and JST and will continue to spread eastward tonight into tomorrow. Expect cigs and vsbys to continue to drop as the night continues. A weak secondary low Tuesday through Tuesday night will shift MVFR to IFR restrictions to eastern areas in light snow, with more scattered snow showers (and thus more scattered restrictions) for western areas. As deep upper trough swings through the region Wednesday, ceiling restrictions again shift back to the western higher terrain along with scattered snow showers. Otherwise, primarily VFR conditions will prevail. Thursday looks to be breezy with gusts to 15-25 mph. Outlook... Tue...Restrictions in light snow mainly SE half. Lingering snow showers with intermittent restrictions over the NW half. Wed...VFR SE half, but ceiling reductions and intermittent vsby restrictions across the Northern and Western mtns as a result of isolated snow showers. Thu-Sat..Mainly VFR.
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&& .HYDROLOGY... The threat of ice jamming is diminishing. Several cold days into mid week to form additional ice. Another warm up by the weekend. Dewpoints for this warm up much less than the event last Friday. && .CTP WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from 5 AM Tuesday to 1 PM EST Wednesday for PAZ051>053-056>059-063>066. Winter Weather Advisory from 2 AM to 8 PM EST Tuesday for PAZ033>036. && $$ SYNOPSIS...DeVoir NEAR TERM...Dangelo/DeVoir SHORT TERM...DeVoir LONG TERM...Martin AVIATION...DeVoir/Ceru/RXR HYDROLOGY...

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