Area Forecast Discussion
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000 FXUS61 KPBZ 221031 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 631 AM EDT FRI JUL 22 2016 .SYNOPSIS... Hot and humid weather is forecast for today into early next week, along with intervals of scattered thunderstorms. && .NEAR TERM /THROUGH TONIGHT/...
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630 AM...A band of thunderstorms currently extends along the Lake Erie shoreline and is heading southeast. Think that some weakening is likely over time as the line heads into a more unfavorable air mass with less available CAPE and 0-6km shear. Likely PoPs are still prudent along/north of I-80 with an increase to higher chance values south to Pittsburgh. Think that this line will degenerate into more scattered activity by late morning...but confidence is fairly low as hi-res models seem to be struggling right now. Previous discussion... Boundary layer moisture will be on the increase today, evidenced by dewpoints rising into the lower 70s in some of the area. While 850 mb temperatures will be a bit warmer than yesterday, cloud cover is expected to be a bit more widespread during the day, helping to keep temperatures from soaring well into the 90s. Nevertheless, low 90s are a good bet for some areas, especially southeast Ohio. Heat index values should reach the upper 90s in this area. While a few locations will flirt with triple digit apparent temperatures, do not think coverage will be widespread enough to warrant heat advisories at this time. As far as precipitation coverage, elected to keep PoPs in the scattered range for the afternoon and evening. Some relatively warm mid level air will help to hinder development at least initially. Also, think that the better deep layer shear will remain with a shortwave crossing the Great Lakes into New England. This should keep a lid on any organized severe weather threat. Nevertheless, decent mixing will promote inverted-V soundings which may point to an isolated wind damage potential with any storms that manage to develop. A weak boundary will sink into the area tonight. Activity will diurnally decrease this evening ahead of it, but given high moisture, presence of the front, and lingering convective boundaries, think at least isolated activity will remain possible for most of the night. Otherwise, a classicly muggy July night can be expected, with low temperatures on either side of 70.
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&& .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... A weak boundary will stall out over the southern third of the forecast area by Saturday morning. Models continue to activate showers and thunderstorms along this boundary through the afternoon, but a lack of upper- level support and dry air through the column should limit development. Opted to continue with slight chance/isolated shower or thunderstorms south of Pittsburgh. Remaining mid-level moisture will clear the southern border by late Saturday, ending the low rain chances. Near-surface moisture and high surface dewpoints will linger, resulting in another warm and humid night with lows well above average. Surface high pressure will shift east Sunday as the next system moves through the southern Canadian Plains. This will return southerly flow, and re-enforce the warm and humid airmass. A few showers could develop across our western zones Sunday afternoon as the weak boundary returns north as a warm front. Heat indices Saturday and Sunday will reach into the mid and upper 90s for a majority of our forecast area, and approach 100 for a few of our southwestern counties. An HWO mention will be maintained for this. Warm and humid conditions will carry into the new work week, although an increase in clouds will limit high temperatures. A weak, sweeping cold front will drag across the area Monday, bringing a chance of rain for all, but the progressive nature of the system will limit amounts. && .LONG TERM /MONDAY THROUGH THURSDAY/... Rain chances will quickly dissipate in the wake of the cold front, Tuesday, bringing a return to dry conditions. The upper-level flow pattern will temporarily flatten to nearly zonal, as high pressure builds at the surface. Temperatures will moderate under the zonal flow aloft, but will remain a few degrees above normal. Consistent model agreement on the digging of a trough over the cornbelt in the latter part of next week. This will bring rain chances back to the forecast Thursday and Friday. && .AVIATION /12Z FRIDAY THROUGH TUESDAY/...
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Watching a band of thunderstorms along the Lake Erie shoreline, which is moving slowly south. Expect some weakening with time as they move into a more hostile environment. Still, a brief period of IFR visibilities in heavy rain looks like a good bet at FKL and DUJ between 12Z and 14Z, and used TEMPOs for this. To the south, with higher uncertainty, continued to use VCTS wording. A brief thunderstorm is possible at any terminal this afternoon in the hot and humid environment. Confidence in timing best chances this afternoon is low, and kept prevailing conditions VFR. Should see a typical decrease in activity this evening, with clouds scattering with time. MVFR visibilities in mist are possible late tonight, especially in any area that gets rain today. .OUTLOOK /FRIDAY NIGHT THROUGH TUESDAY/... Restrictions will be possible late Sunday and Monday with crossing disturbances.
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&& .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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