Area Forecast Discussion
Issued by NWS Pittsburgh, PA
Issued by NWS Pittsburgh, PA
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030 FXUS61 KPBZ 092146 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 446 PM EST Sat Nov 9 2024 .SYNOPSIS... Dry weather will continue before low pressure brings widespread rainfall Sunday into Monday. Uncertainty increase into next week with possible rain chances returning by mid-week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... KEY MESSAGES: - Increasing clouds tonight; rain may arrive in eastern Ohio before sunrise. - Overnight temperatures remain a bit above normal. ------------------------------------------------------------------- Made generally minor adjustments to the forecast tonight, mainly focused on dewpoints and sky cover. Easterly flow and a very dry column are supported low dewpoints and relative humidity levels in the 20 to 30 percent range across the CWA, with locally drier values. Temperatures in the upper 50s/lower 60s currently represent above-normal values. Southwest flow aloft behind departing high pressure will continue to help thicken mid and upper-level clouds this evening. Warm advection will keep overnight lows in the upper 30s-low 40s. A warm frontal boundary will lift towards the Upper Ohio Valley tonight ahead of Upper Midwest low pressure. Increasing isentropic lift and precipitable water will continue to thicken cloud cover, but high condensation pressure deficits/antecedent dry air will generally keep any precipitation from arriving in our eastern Ohio counties until after 09Z or so. && .SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY NIGHT/... KEY MESSAGES: - High confidence in widespread wetting rainfall on Sunday. ------------------------------------------------------------------- Deep southwest flow will provide a strong pull of Gulf and remnant Rafael moisture on Sunday with integrated vapor transport values 2-4 SD above normal and ensemble mean precipitable water near 1.3" which is near the daily maximum value. As low pressure lifts through the Great Lakes region, widespread rainfall is expected to arrive in the morning hours. The most steady rain likely comes Sunday afternoon as an 850 mb jet encroaches and enhances low level convergence. Current ensemble probability for a wetting rain (at least 0.10") is very high at 95-100% areawide. Similarly, at least 0.25" is 90+% with a 60-75% chance of a half an inch. The higher end (90th percentile) of the goal posts has continued to sit around an inch and is likely contingent on capitalization of whatever marginal instability can develop; instability likely won`t be surface-based given the low-level warm advection regime, so any severe weather threat is low. The system will be progressive overall, but wouldn`t rule out some localized totals nearer to the 75th-90th percentile in some of the maximized higher rainfall rates. && .LONG TERM /MONDAY THROUGH SATURDAY/... KEY MESSAGES: - Low confidence rain chances for the beginning of the week. - Better rain chances come mid-week but still some uncertainty.- - Highs a few degrees above normal. ------------------------------------------------------------------- Some showers may linger into Monday behind departing low pressure as a weak secondary trough moves through, but ensemble clusters suggest increasing uncertainty with the upper level pattern to start out next week as an additional upper wave follows quickly behind the original one from Sunday. Some clusters merge these waves while others favor a flatter, more progressive pattern. A slower departure would favor cooler temperatures and lingering precip chances through Monday night while a faster pattern favors warmer, drier conditions. Overall consensus is that high pressure and upper ridging briefly return which favors still above normal temperatures through mid- week. Another better chance for rain may come sometime Wednesday into Thursday with another round of low pressure, but significant differences among the ensembles suggests a low confidence forecast by this point. Therefore, it is likely that given the drier trend, Friday will likely see high pressure and dry conditions returning. && .AVIATION /21Z SATURDAY THROUGH THURSDAY/... VFR conditions will prevail through Saturday with wind out of the east and gradually veering to south of east this evening after 00z. SCT to BKN upper level cloud deck, with upstream base height observations between 150-200, will push into the area tonight as moisture increases ahead of approaching low pressure that will bring widespread rain and restrictions on Sunday. Cloud bases lower further into the morning hours on Saturday and restrictions are favored to overspread the region coincident with precipitation as low level saturation is achieved. Latest ensemble probability indicates most likely arrival time of showers and MVFR CIG/VIS in rain around 12z at ZZV, 15z at PIT, and 17z at LBE, though a couple hi res models are slightly more progressive than the ensemble mean. MVFR conditions are high probability (90+%) with a 50-70% chance of both IFR CIG and VIS as a low level jet aids in forcing and more moderate rain, but timing of this is currently just encompassed at the end of the PIT TAF period. Visibility and ceilings will improve some headed into the overnight hours Sunday night, but lingering low-level moisture overnight doesn`t bode very well for a high confidence return to VFR. .Outlook... A passing cold front early Monday will decrease the potential for rain. However, restrictions may linger into late Monday morning due to residual low-level moisture and cold advection. && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...None. OH...None. WV...None. && $$ SYNOPSIS...88 NEAR TERM...CL SHORT TERM...CL/88 LONG TERM...88 AVIATION...MLB