Area Forecast Discussion
Issued by NWS State College, PA

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260 FXUS61 KCTP 271434 AFDCTP Area Forecast Discussion National Weather Service State College PA 1034 AM EDT WED JUL 27 2016 .SYNOPSIS... A weak front will remain along or just to the south of the Commonwealth through tonight, as high pressure maintains warm and mainly dry conditions. An area of low pressure approaching from the west is likely to lift through the region on Friday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Satellite shows some clouds along southern tier. Nothing of note on radar. For consistency and collaboration showed some slight chance showers along border. No QPF and slight PoPs numbers. Most of the broken to overcast cloud decks should stay close to PA/MD border. So farther north in the shallow drier air the more sun. Dew points today mainly in the 60s so a bit of relief. Temperatures probably close in most areas to yesterdays maximums. Temperatures were mainly a model blend with some HRRRV1 temperatures added for texture. HRRRV1 is too warm for daytime highs but shows upper 80s in northwest and northwest mountains, near 90 central and southwest mountains, and mid-upper 90s in southeast. HRRRV1 has run about 2-3F too warm the past week or so. Many locations have seen 5 to 7 days of high temperatures of 90 or greater recently. A rather enduring heat episode.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
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Most guidance holds off the rain until Thursday afternoon. The NCAR EFS and HRRRV2 imply this too. This evening should be rain free. Clouds in southern areas will increase this evening and overnight and chance of showers will increase in southwest after midnight. The NCAR EFS implies showers in southwestern areas a few hours after 5 AM Thursday morning. The rain spreads to the east and north during the day. This is close to the GEFS viewed in 3-hour increments showing rain by 2 PM in southwest and over most of central and southern areas by 7 PM. NCAR EFS may be a bit faster with the lighter amounts. Suffice to say chance of showers in extreme southwest in morning with increasing chance of rain into afternoon spreading across the region. Lower PoPs in northernmost areas. Most guidance implies a better slug of rain possible overnight Thursday into Friday, beyond the scope of this forecast period (see below).
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&& .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
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In the medium to long-range period...conditions slowly revert to near normal in temp and precip as several chunks of short wave energy in the westerly flow aloft helps to carve out a mean 500 mb trough axis over the Glakes and Ohio Valley region during the Thu- Fri timeframe. The peak in unsettled weather (with perhaps some periods of down- right rainy conditions) occurs Thursday night and Friday as a well-defined wave of sfc-850 mb low pressure lifts ENE out of the Ohio Valley and heads across the I-95 Megalopolis. Followed a blend of EC/GEFS/superblend and NBM guidance for that particular 24-36 hour period to arrive at likely pops for rain and scattered TSRA. Some uncertainty in timing and areal coverage of the convection led us to undercut the NBM by 10-20 percent for now, recognizing issues with large scale model convective parameterization schemes (and subsequent exaggeration of the areal coverage and broader qpf amounts) means that we`ll likely see more concentrated areas/bands of heavy convection, compared to the model depicted, larger cold season stratiform look to the precip shield. Portions of Southern and Central PA...close to the track of the 1006-1008 mb sfc low will likely see some localized heavy 1-2 inch,12-24 hour rainfall amounts by Friday afternoon...with even the potential for some pinpoint heavier amounts from embedded TSRA, as a tongue of 2 inch pwat air lifts north and wraps cyclonicly into sern PA and the Lower Susq Valley. For later Friday through the upcoming weekend, a large area of high pressure (1020-1024 mb) near the border of southern Quebec and Ontario will try to push drier air south into the Mid Atlantic Region. Another...apparently weaker wave of low pressure at the sfc and aloft lifts NE out of the Ohio Valley over the weekend and brings an enhanced chc for showers. Slight diffs in timing/location exist between the EC/GEFS and NBM guidance. However...the target period for the best chc of showers and isolated to sctd TSRA appears to be late Sat into Sunday. Afterward, heights begin to rise from the southwest, accompanied by a ridge of surface high pressure building east into PA with mainly dry conditions and a rebound in temps for early next week.
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&& .AVIATION /14Z WEDNESDAY THROUGH SUNDAY/...
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VFR most of the day today. Relatively light winds. Flying conditions will change Thursday into Friday as a frontal wave brings rain and showers to the region. Expect increased chance of MVFR and IFR Thursday into Friday with areas of rain and isolated thunderstorms. Conditions should improve Friday into Saturday. OUTLOOK... THU-FRI...areas of MVFR and IFR in Rain and isolated TSTMS SAT-SUN...Mainly VFR.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...DeVoir NEAR TERM...Grumm SHORT TERM...Grumm/DeVoir LONG TERM...Lambert/Gartner AVIATION...Grumm/Dangelo

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