Area Forecast Discussion
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027 FXUS61 KPBZ 240735 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 335 AM EDT SUN JUL 24 2016 .SYNOPSIS... Hot and humid conditions will continue. The best chance for showers and thunderstorms will return on Monday with the passage of a weak cold front. && .NEAR TERM /THROUGH MONDAY/...
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Quite the dewpoint discontinuity remains over the area early this morning as the weak surface boundary has sagged southward. Regardless of where that boundary is this morning, low level flow looks to quickly turn west-southwesterly after sunrise. This will bring the air currently residing over southwestern Ohio toward our CWA. As a result, dewpoints should climb rapidly into the daytime on as the boundary lifts back north of the area. A convective complex currently decaying while slowly trudging eastward near the southern end of Lake Michigan will manage to spread high clouds toward the area for portions of the day on as model RH projections do surge above 500 mb through the morning. However, even in the upper levels, flow does manage to back a bit more southwesterly through the day, which should shunt a bit of that moisture northward by afternoon. However, to be complete, some of the hi-res guidance does sag the remnants of the complex southeastward toward the CWA by afternoon. Satellite trends would suggest that even if this were to occur, there would likely be scant activity remaining with it. What was particularly unusual on Saturday was the spread of 90F+ temperatures across the area with 850 mb temperatures that really didn`t even manage to meet 20C. That said, the drier boundary layer present in some areas on Saturday will not be readily apparent on today with dewpoints surging toward and above 70F. However, consensus 850 mb temperatures manage 22C with 23C likely toward Morgantown. This should put the majority of the area into the 90s for highs...and even well into the 90s over Ohio. Thus with dewpoints increasing and high temperatures at least as high as Saturday even with more high clouds, a heat advisory has been coordinated for all Ohio, non-mountainous West Virginia, and southwestern Pennsylvania counties generally south of the turnpike. Yet another warm front does start to move through the area by late Sunday, increasing the chances of showers and thunderstorms as it does. This will bring increasing clouds and dewpoints into tonight, which will likely keep low temperatures well above 70 in most spots. The associated cold front looks poised to advance southeastward by Monday afternoon and evening. However, strong mixing and warm advection with a very humid air mass ahead of it will again mean a day with heat index values possibly reaching 100 degrees again on Monday. Fries
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&& .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
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A sweeping cold front will bisect the forecast area Monday night, as the parent upper-level low shifts into the eastern Great Lakes. The boundary will be slow to sag south of the area, prolonging shower and thunderstorm chances into midday Tuesday. By Tuesday afternoon, surface high pressure and drier air will invade from the north and quell rain chances north of I-70. Wednesday is expected to be mostly dry, with the exception coming in the ridges where the elevated heat source could generate a few showers or thunderstorms. Relief from the recent high dewpoints will finally come with fresh air behind the front. Dewpoints will drop precipitously into the low to mid 60s by Tuesday afternoon, and upper 50s to low 60s by Wednesday. Despite temperatures holding above average, the lower dewpoints will feel much more comfortable than the current air mass. TAx
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...
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A bit of a pattern shift expected later this weekend carrying into the weekend. High pressure that has led to the current heat wave will gradually retrograde back to the four corners region of the southwest CONUS. This will allow a broad trough to replace the zonal flow over our region by Thursday. Several shortwaves will pass through the upper-level flow pattern, bringing periodic rain chances through the weekend. With the broad upper-level trough firmly in place, temperatures will return to near-normal by the weekend. TAx
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&& .AVIATION /08Z SUNDAY THROUGH THURSDAY/... Some high clouds are moving over the area as of 06z. This is slowing radiational cooling and also likely slowing the onset of visibility restrictions. Due to ample low level moisture and recent rain, it still seems fairly likely some amount of fog will be present by morning generally from KPIT southward. Otherwise, some increase in mid-level clouds will be apparent through the day from NW-SE as the next system to affect our region approaches for this evening. Otherwise, VFR conditions will be common after some morning fog. Fries .OUTLOOK /SUNDAY THROUGH THURSDAY/... Restrictions will be possible late Sunday and Monday with the approach and passage of a weak cold front. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...Heat Advisory from noon today to 8 PM EDT this evening FOR OHZ039>041-048>050-057>059-068-069. PA...Heat Advisory from noon today to 8 PM EDT this evening FOR PAZ020-021-029-031-073-075. WV...Heat Advisory from noon today to 8 PM EDT this evening FOR WVZ001>004-012-021-509. && $$

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