Area Forecast Discussion
Issued by NWS State College, PA

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039 FXUS61 KCTP 181741 AFDCTP Area Forecast Discussion National Weather Service State College PA 141 PM EDT Sun Mar 18 2018 .SYNOPSIS... Fair and dry conditions will finish off the weekend and start the new workweek with a slow moderation in temperatures anticipated. A storm system is expected to move south of the region Monday night and Tuesday. High pressure will return for the end of the week. && .NEAR TERM /THROUGH TONIGHT/...
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Clear skies dominate the weather this afternoon over central PA. West winds have picked up a bit in deep layer mixing, but overall speeds in that layer are light resulting in surface speeds around 10 mph with occasional gusts to 15-20 mph. It is also quite dry out there today with RH values between 20-30%. Though RTMA not doing too bad overall, near term model forecasts (esp HRRR) have really been struggling with dewpoint forecast all day long requiring forecaster-based adjustments in the grids. Highs do look like they will top out near both this morning`s MaxT forecast numbers and seasonal averages - peaking in the 40s to lower 50s. Clear skies will continue overnight with lows dropping back into the teens and 20s, with dewpoints slowly rising through the teens to around 20F in all but the NE.
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&& .SHORT TERM /MONDAY/... Monday will remain fair and dry, but with a gradual increase in clouds late in the day. Highs will range from the mid 30s north to around 50 south. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... The main weather maker of concern is a low that will slide across the TN Valley and central Appalachians Monday night and moves off the VA coast on Tuesday. After trending south over the last couple of days, guidance has crept north with the precip shield. Last night`s ECENS painted an almost total miss from the storm, then tonight it changed course and now shows anywhere from about .25-.50" QPF from around I-80 southward. Still doesn`t look like a big threat for significant snow with several factors expected to play a role. This time of year with marginal temps, we generally need good precipitation rates to keep the atmospheric column cold enough to be all snow, and so far the indications are that on the northern periphery of the precip shield, rates will not be impressive. Also with the bulk of whatever falls expected to be during the daylight hours of Tuesday, the high sun angles usually limit accums this time of year. So we stuck pretty close to HPC guidance for little more than a coating over the Mason-Dixon counties. After a period of dry weather in the wake of the Tuesday storm, the upcoming weekend poses another potential threat for rain or snow. The scenario is far from clear. The 00Z GFS takes a robust surface low pretty much straight east and tracks it through southern Pa during the day. The ECMWF is slower but shows a very similar scenario with the low passage favoring Saturday night. The interesting thing is each model`s ensemble partner almost completely washes the surface lows as they approach, losing them along some sort of frontal boundary off to our south. With the forecast upper pattern showing the lows moving into a broad ridge, the lows washing out looks like a reasonable scenario. Below normal temps will persist though mid week with a moderating trend for the end of the week into next weekend. The Vernal Equinox will be Tuesday at 1215 pm EDT. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/... VFR conditions across the area as of 7 am. No clouds...haze or fog outside. No big changes for the 12Z TAFS. Model data continues to support a high confidence of widespread VFR conditions today. However...there is a chance of MVFR stratocu spreading into northern Pa late this evening associated with the passage of a weak cold front from the northeast. However...the airmass is quite dry over our area and to the northeast over eastern New York state. Outlook... Mon...No sig wx expected. Tue...Snow likely southern Pa...mainly early AM. Wed...AM light snow possible Laurel Highlands. Thu...No sig wx expected. && .CLIMATE... The Spring (Vernal) Equinox will be at 12:15 PM on Tuesday, March 20. Sunrise in State College, PA will be 7:14 AM and sunset at 7:23 PM, for a total daylength of just over 12 hours. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...La Corte/RXR NEAR TERM...La Corte/RXR SHORT TERM...La Corte LONG TERM...La Corte AVIATION...Martin CLIMATE... is the U.S. government's official web portal to all federal, state and local government web resources and services.