Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 231507 AFDCTP Area Forecast Discussion National Weather Service State College PA 1007 AM EST Fri Feb 23 2018 .SYNOPSIS... A nearly stationary frontal boundary will remain just south of out Pennsylvania through Saturday, before lifting north across the commonwealth as a warm front Saturday night. A cold front will ultimately usher in cooler and drier air Sunday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Areas of drizzle and pockets of freezing drizzle will remain a concern over the higher terrain of northeast PA this morning. Mesonet continues to show temperatures between 31-32F over the higher elevations of north central Pa and HRRR and SREF temp plumes indicate steady or even slowly falling readings through 12z. Ribbon of higher deep layer moisture extends from the Lower Mississippi Valley into the Ohio Valley...eastward along and south of the Mason Dixon line to the offshore mid Atlantic waters, where PW is between 1.0" and 1.25". Shortwave cresting the upper ridge is maintaining showers along the PA/MD border eastward to the southeast Piedmont this morning. HRRR tracks these offshore by mid morning, as the next slug of moisture arrives from the Ohio Valley. The next wave/batch of rain should is still timed into the Alleghenies by 13z this morning, and into the Central Mountains by 15z-16z. All but the Lower Susq will see showers by late morning, but even the Lower Susq. should see likely POPs by early afternoon as robust PW approaching 1.25" surges ENE. Meanwhile, over the high terrain of northeast Pa, temperatures are expected to remain around the freezing mark through at least midday, so will maintain the winter weather advisory up there through noon. Latest NBM indicates a change to rain in most areas Friday afternoon. However, the normally colder HREFV2 keeps some of the northeast ridgetops below freezing into this evening. Plain rain to fall everywhere else as temperatures hold steady in the mid 30s to low- mid 40s. Expect a very small diurnal variation east of the Alleghenies due to CAD, while milder air surges into far SW PA. Steadiest and heaviest rainfall diminishes late this afternoon/early this evening. It will be a cool and damp overnight with areas of fog and drizzle. && .SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY NIGHT/... After a lull in the precip tonight in between waves, the focus this weekend will shift to potential flooding, with additional waves of moderate to locally heavy rain moving over the area through Sunday. PW again surges to between 1.0" and 1.33" late Saturday through Sunday morning as an energetic upper wave and frontal system slice across the region. Flood watch remains in effect for western and central sections through Sunday evening, as we expect significant rises on streams, creeks and river tribs with streamflows already above normal. The ground/soil is nearly saturated so the risk for widespread minor river flooding, along with poor drainage/low- lying flooding is certainly in play. Temperatures will slowly rise but should eventually reach the 50s and low 60s by Sunday based on multi model consensus blend. && .LONG TERM /MONDAY THROUGH THURSDAY/... The wet pattern looks like it will take a break during the first part of next week before precip risk increases Wed-Fri. Temperatures should continue to run above average for late February. && .AVIATION /15Z FRIDAY THROUGH TUESDAY/...
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A stationary boundary just south of the MD border will provide the focus for periods of rain and drizzle into Sunday. Expect widespread IFR conditions to continue at least into Friday. A strong SW LLJ will provide the potential for some LLWS this afternoon into the overnight. Outlook... Fri...Widespread restrictions in periods of rain. Some improvement poss SW late. Sat...Widespread restrictions with rain. Sun...Widespread restrictions likely in periods of rain. Mon-Tue...No sig wx.
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&& .HYDROLOGY... Active hydrologic pattern through Sunday. Recent snow melt and rainfall has soils quite wet. Streamflows are also running high. Recent rainfall has stream flows above average. So focus will turn to where the heaviest rain falls and if it is heavy enough to produce flooding. Models consistent with heaviest rain west of the CWA but still close enough to keep a flood threat over the western half of the CWA. Issued a Flood Watch for this area to address the threat. Right now no river forecast to flood, but expect significant rises and will monitor closely. Some poor drainage and small stream flooding is likely. && .CTP WATCHES/WARNINGS/ADVISORIES... Flood Watch through Sunday evening for PAZ004>006-010>012- 017>019-024>026-033>035-045. Winter Weather Advisory until noon EST today for PAZ006-037- 041-042-058. && $$ SYNOPSIS...DeVoir/La Corte NEAR TERM...DeVoir/La Corte SHORT TERM...DeVoir/Steinbugl LONG TERM...DeVoir/Steinbugl AVIATION...La Corte/Ceru HYDROLOGY...

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