Area Forecast Discussion
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000 FXUS61 KPBZ 142326 AAB AFDPBZ Area Forecast Discussion...UPDATED National Weather Service Pittsburgh PA 726 PM EDT Sat Apr 14 2018 .SYNOPSIS... Rain chances will increase later tonight and Sunday with the approach of a cold front. Colder air and showers will follow into early next week. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
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725pm update...continue to wrestle with the PoPs this evening and overnight. Radar showing broad area of showers, but obs indicating nothing more than a very light shower or sprinkles. Have left in PoPs, but would think most location see little to no rain. Temperatures are another headache with front to the north slowly moving southward as surface low over northern WV weakens and washes out, allowing the front to move further south. Amazing differences in surface temps, depending on what side of the front you are located. Temp difference of 20+ degrees over less then 50 miles. Model temp forecasts are having trouble get a firm grip on this. Previous discussion... Do not have much further PoP expansion tonight as the warm sector will only grudgingly give up ground. Rain will mainly focus on the boundary to our north and the approaching frontal wave to the west. Did not change temperature forecast much overnight, but northern counties are tricky, depending on position of boundary, with much colder air not too far to the north.
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&& .SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/... Models are still in good agreement in dragging the strong upper low from the Mississippi Valley into our area by Monday afternoon. The NAM is still very aggressive in pushing the northern boundary through in a back-door way, bringing in much colder air in the low levels, particularly in the northeastern CWA. Did trend max temps down slightly here for Sunday, but for now not totally buying into the colder scenario. Alerted next shift to monitor. The main period of rainfall is still figured from Sunday afternoon through Sunday night, as a moisture-laden low level jet crosses the area. Categorical PoPs are maintained. There are still some caveats to the expectations of heavy rainfall. Overall lack of instability may keep the period of convective rainfall fairly short, although the dynamic nature of the system should allow for at least isolated elevated convection. Also, some recent drying has allowed 6 hour FFG values to rise above 1.6 inches in many areas. However, there is some potential for south-to-north training of heavier showers, particularly from Pittsburgh to areas east and south. Plus, the continued strong ensemble signals for heavy rain, as well as climo max challenging PWATs of 1.3 to 1.4 inches are hard to ignore. Elected to issue a Flash Flood Watch for some of the southeastern counties where confidence in heavy rain is greatest. 1.5 to 2.5 inches of rain is possible here for this event. Confidence in flooding was less elsewhere, but expansion of this watch by future shifts may be warranted. Steady rain will depart the area by Monday morning, and colder air will arrive with the resultant troughing behind the front. Scattered to numerous showers will continue. Snow will mix in first along the ridges on Monday, and then in most areas by Monday night. Given the recent run of warmth, any mostly inconsequential accumulation should mainly be limited to grassy and elevated surfaces. && .LONG TERM /TUESDAY THROUGH SATURDAY/... Troughing with below normal temperatures and showery precipitation will linger into Tuesday morning. Transient riding will provide a drier and milder interlude Tuesday night into Wednesday. Low pressure will advance from the upper Mississippi Valley Wednesday into the Great Lakes Wednesday night. Showers return with this system and linger into Thursday in its wake, with below normal temperatures returning. Drier weather, and perhaps moderating temperatures, may return by the end of the week. && .AVIATION /00Z SUNDAY THROUGH THURSDAY/... General VFR forecast through at least Sunday morning. The exceptions will be at ZZV,FKL and DUJ. ZZV could see a period of MVFR cigs later this evening and overnight as they will be located on the northwestern side of a passing boundary. The same will be true at FKL and DUJ, although it will take a bit longer for lower clouds to reach those ports. Conditions are expected to deteriorate Sunday afternoon as the aforementioned front pushes further south. VIS restrictions are possible overnight at ZZV and FKL, with all other ports seeing little to no rain. Surface winds will increase again on Sunday with easterly gusts of 20 to 30kts possible during the afternoon. OUTLOOK... MVFR is anticipated for Monday and Tuesday as the area will remain under an upper trough of low pressure. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...Flash Flood Watch from Sunday afternoon through late Sunday night for MDZ001. OH...None. PA...Flash Flood Watch from Sunday afternoon through late Sunday night for PAZ021-029-031-073>076. WV...Flash Flood Watch from Sunday afternoon through late Sunday night for WVZ021-509>514. && $$

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