Area Forecast Discussion
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000 FXUS61 KPBZ 251804 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 204 PM EDT Sun Jun 25 2017 .SYNOPSIS... Upper low pressure will maintain cooler temperature and a periodic shower chance for the first half of the week. && .NEAR TERM /THROUGH TONIGHT/...
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Mid-level temperatures look to fall off another 4-5C by through the late afternoon and evening hours as a mid-level short wave crosses the area concurrent with peak heating. A fairly vigorous upper jet streak will be transiting likewise, and the combination of DPVA, right entrance region upper divergence, and increasing lapse rates will yield a good combination of forcing for ascent and instability. This will at the very least generate a marked uptick in cumulus development along a boundary that moves through this afternoon. The mitigating factor will likely be fairly lean layer moisture. However, given the instability profiles, 12z sounding convective temperature of 71F that should easily be eclipsed, and hi-res model depictions, isolated showers with the passing short wave seem like a fairly good bet and were added to the forecast for most areas. Furthermore, model soundings suggest wet bulb zero heights falling off toward 5 kft, which would favor some small hail development in the more vigorous updrafts. With cold advection underway through the day through the column, high temperatures will be largely restricted to several degrees below normal. Even with the cold pool overhead, stabilization should occur fairly efficiently overnight due to dry air, a weakening wind field, and loss of favorable jet streak dynamics. This should allow temperatures to fall off rapidly with the lower dewpoints in place, resulting in low temperatures well below normal. Fries
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&& .SHORT TERM /MONDAY THROUGH TUESDAY/...
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Mean troughing will remain across the area through the short term period. This combined with the passage of a more vigorous mid-level system will allow for rather unsettled conditions with scattered showers throughout the period. Likewise, with mid- level cooling, lower convective temperatures, and subdued 850 mb temperatures, even with decent mixing, surface temperatures will remain well below normal. Fries
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&& .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
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The pattern rapidly evolves to favor flat ridging moving toward the Appalachians by the latter half of the work week. However, the lack of deepening of the system that shifts toward the upper Mississippi Valley combined with a fairly weak subtropical ridge off the southeastern U.S. coast will mean moisture advection should occur fairly readily over the flat ridge. As such, while a short period mid-week looks dry, humidity and thunderstorm chances should return with warmer air later in the week. Fries
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&& .AVIATION /18Z SUNDAY THROUGH FRIDAY/... VFR conditions will continue through the period with diurnal cu and gusty winds diminishing with the loss of heating/mixing tonight. Scattered showers are possible, mainly in the vicinity of the northern terminals, as a shortwave passes through the upper trough and temperatures continue to cool aloft. The same can be said for tomorrow. .OUTLOOK... Brief restrictions are possible with showers and scattered storms tomorrow and Tuesday with the passage of the upper trough axis. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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