Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 222119 AFDCTP Area Forecast Discussion National Weather Service State College PA 419 PM EST Thu Feb 22 2018 .SYNOPSIS... A nearly stationary frontal boundary will remain just south of out Pennsylvania today 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 7 PM THIS EVENING/... Water vapor loop shows a well defined upper level shortwave with an almost classic baroclinic leaf feature lifting into the entrance region of a powerful upper jet streak moving through eastern Canada. The trough axis is entering western Pa as of early afternoon and the radar confirms this with the back edge of the precip beginning to look more ragged as it moves through my western counties. Weaker UVVs have led to snow going back over to some sort of wintry mix at BFD where the temp has recovered above freezing. The advisory for mixed precip is set to expire at 21Z and this looks reasonable as temperatures nudge to just above freezing and the precipitation tapers off to spotty showers or drizzle. From earlier... The lower branch of the thermally direct circulation into the upper jet streak is providing a potent ageostrophic component to the flow out of the NE helping to keep the cold air filtering south into the ridge-valley region. This will keep the possibility of isolated pockets of freezing rain or drizzle in the forecast until things taper off between about 3 and 5PM, according to the latest HRRR timing. && .SHORT TERM /7 PM THIS EVENING THROUGH SUNDAY NIGHT/...
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Residual low level moisture, combined with an upsloping easterly flow, is likely to yield lingering drizzle/mist/fog over much of the region into tonight. Pockets of light freezing rain and drizzle are likely over the higher terrain in north- central PA into the southern Poconos tonight through early Friday morning. As the next batch of rain moves into the area, expect another icy interval Friday morning across this area including the northern portion of Schuylkill County before changing to rain in most areas Friday afternoon. Extended the winter weather advisory overnight until midday Friday for Potter, Tioga, N. Lycoming and Sullivan Counties (covering the lingering -fzra/-fzdz and best period of icing Friday morning) and also expanded to include Schuylkill Co. based on ice accum and coordination with BGM/PHI. Anticipate some icy spots Friday morning with impacts to the AM commute. Elsewhere expect plain rain 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. The focus then shifts to potential flooding with waves of moderate to locally heavy rain move over the area through the weekend. Flood watch was issued for west-central PA through Sunday evening. Expect significant rises on streams, creeks and river tribs with streamflows already above normal. The ground/soil is very 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.
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&& .LONG TERM /MONDAY THROUGH THURSDAY/...
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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.
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&& .AVIATION /21Z THURSDAY THROUGH TUESDAY/... Widespread MVFR/IFR will continue into the evening and overnight. Rain continues to fall from about I-80 southward with a wintry mix over the northern tier. BFD has gone back to a wintry mix and the temp has risen to 34. Timing of the back edge of the steady rain/mix looks good to taper off between about 2-5PM. Active weather will continue into the weekend with several disturbances bring widespread rain and sub VFR conditions. 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. && .HYDROLOGY... Active hydrologic pattern through Sunday. Recent snow melt and rainfall has soils quite saturated. 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...
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Flood Watch through Sunday evening for PAZ004>006-010>012- 017>019-024>026-033>035-045. Winter Weather Advisory until noon EST Friday for PAZ006-037- 041-042-058.
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&& $$ SYNOPSIS...La Corte NEAR TERM...La Corte SHORT TERM...Steinbugl LONG TERM...Steinbugl AVIATION...La Corte/Lambert HYDROLOGY...Ross

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