Area Forecast Discussion
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473 FXUS61 KPBZ 250742 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 342 AM EDT Tue Oct 25 2016 .SYNOPSIS... High pressure will bring dry and cool conditions into Wednesday. Low pressure will bring showers back into the forecast Wednesday night through early Friday. && .NEAR TERM /THROUGH TONIGHT/...
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General northwest flow will continue through the day today with some indications of a bit of a multi-lake fetch enhancing moisture flow toward the northern portions of the area. Model soundings and hi-res solutions both favor the continuation of a stratocumulus deck generally from Pittsburgh northward and developing into the ridges through the morning with diurnal enhancement likely toward early afternoon on Tuesday. A shower or two will be possible in the far northern reaches of the area due to very unstable low level lapse rates and some indications of saturation depth through the stratocumulus layer. Otherwise, the area remains dry through the day today with over-lake fetch decreasing late. This should start to allow for the dissipation of stratocumulus by that juncture. As high pressure continues to slowly build toward the area into the nighttime tonight, surface flow should gradually relax. This will basically entirely remove the lake influence in the temperature field across the area and allow for fairly optimum conditions for radiational cooling. The only fly in the ointment may be some incoming mid or high clouds from the west. However, because model depictions of mid and upper level RH fields are less than impressive, it seems more likely this possible cloud cover will be somewhat insignificant. Thus, low temperatures were allowed to fall toward or below freezing on a fairly widespread basis outside of the urban core. However, since we will be two weeks beyond the end of the normal growing season, no additional frost or freeze headlines are planned at this time beyond the ones already in effect this morning. Fries
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&& .SHORT TERM /WEDNESDAY THROUGH FRIDAY/... As a deepening Great Lakes low pressure system approaches Wednesday, a warm front will lift across the area. This will bring an increase in clouds, but dry air near the surface should maintain a dry forecast through much of Wednesday. Shower chances increase Wednesday night as the surface low moves into IN/OH. Models seem a bit slower with the approach of this system, but the general track largely remains the same. Categorical PoPs have been included across the north for Thursday morning with likelies maintained elsewhere. An increasing low-level jet will keep Wednesday night lows relatively warm and return gusty winds to the region Thursday. Timing details could change some, but the current forecast follows a GFS-modified diurnal trend instead of a more climatological trend. The upper low will close off over New England Thursday night, keeping cold northwest flow across the region into Thursday night with scattered showers. && .LONG TERM /FRIDAY NIGHT THROUGH MONDAY/... Any lingering northwest flow showers should wane Friday evening as high pressure briefly crosses the region. Models show another system dampening the crest of the broad upper ridge to the west early Saturday, but significant model differences exist on track and timing. Regardless, unsettled weather looks to continue over the weekend, with focus of rain showers north of Pittsburgh. Thus, have maintained the likely PoPs across the northern 1/3 of the forecast area. A building ridge will then establish over the southeastern CONUS early next week with drier and much warmer conditions expected. && .AVIATION /08Z TUESDAY THROUGH SATURDAY/... VFR conditions seem most likely to continue at all sites through the period. Some lake-induced showers may wander as far south as KFKL and KDUJ for a time toward morning, making some MVFR conditions a possibility, however they shouldn`t linger. Stratocumulus should also start to scatter out from the southwest by afternoon with all sites likely to see nearly clear conditions by evening on Tuesday. Fries .OUTLOOK /TUESDAY THROUGH FRIDAY/... The next chance for general restrictions will late Wednesday into Thursday as the next disturbance crosses the region. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...Frost Advisory until 9 AM EDT this morning FOR OHZ039-048-049- 057>059-068-069. PA...None. WV...Frost Advisory until 9 AM EDT this morning FOR WVZ004-012. && $$ is the U.S. government's official web portal to all federal, state and local government web resources and services.