FXUS61 KPBZ 111155 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 755 AM EDT Sat May 11 2024 .SYNOPSIS... Low pressure tracking from Michigan into western New York State is expected to bring showers and thunderstorms to the forecast area into tonight. Showers are expected to end Sunday morning with dry weather expected on Monday. The weekend will be about 10 degrees below normal on temperatures, with readings rapidly climbing to nearly 10 degrees above normal for Monday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... KEY MESSAGES: - Areas of fog early this morning - Showers and thunderstorms today - Small hail and gusty wind possible this afternoon ------------------------------------------------------------------- Areas of fog should mix out shortly as winds increase and diurnal mixing initiates. Otherwise, a shortwave trough and surface cold front will track eastward out of the Great Lakes and Upper Midwest region today. Increasing moisture and ascent in warm advection ahead of the front will result in a band of showers moving across the region from mid to late morning into the afternoon. The cold front will quickly follow, with scattered showers and thunderstorms developing. HREF MU CAPE values reach 500 j/kg during the peak heating of the day. This, along with low freezing levels around 5-6kft, should result in a potential for small hail in some of the storms. 25-40kt low to mid level wind and 40kt 0-6km shear should also result in a potential for wind gusts up to 40 mph. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/... KEY MESSAGES: - Thunderstorm potential ending early this evening - Scattered showers continue, mainly north of Pittsburgh ------------------------------------------------------------------- THe cold front will complete its passage this evening, with the thunderstorm potential ending. A mid and upper low across southern Ontario and the Lower Great Lakes will drop southeastward overnight, maintaining isolated to scattered showers across the region. Cold advection overnight should result in overnight lows averaging around 5 degrees below seasonable levels. && .LONG TERM /SUNDAY THROUGH FRIDAY/... KEY MESSAGES: - Temperatures remain about 10 degrees below normal Sunday. - Rapid warmup Monday to nearly 10 degrees above normal. - Showers and thunderstorms return Tuesday/Wednesday. ------------------------------------------------------------------- Cold upper 500 mb low of 5450-5480 meters over PA in the morning will pull east over the Atlantic with large height rises on the order of 150 meters expected during the day Sunday. Lingering morning showers in the northeast part of forecast area should end with significant drying by afternoon. It will remain cool with highs in the lower 60s. Short wave ridging is expected Monday with sunshine pushing temperatures much higher. With mean 850 mb temps rising 8C in 24 hours, this will result in at least a 15 degree warmup with highs 75-80. Given the tendency for NBM to run about 2F too cool on days with strong insolation and deeper mixing, nudged MaxT up a couple of degrees. Guidance in relatively good agreement in bringing upper trough across STL area Tuesday and up the Ohio River valley Wednesday. Showers and thunderstorms will result Tuesday with southwest flow bringing PWs around 1.25" to area. Showers may linger Wednesday beneath upper trough. Upper ridging builds on Thursday and dry conditions are expected to return. Uncertainty begins to increase Thursday and Friday with rather large 500 mb height standard deviations in the NBM, so confidence in the late week forecast is relatively low. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/... A band of showers is expected to cross the region later between 14z-19z under warm advection ahead of an approaching cold front. MVFR visibilities with localized MVFR cigs are expected with these showers. Dry advection aloft may create a window of drier weather behind the shower lin before scattered to numerous showers and thunderstorms develop along the cold front. Upper level support and greater moisture content will favor northwest PA for this convective activity, with decreasing probabilities moving towards KZZV. Sufficient wind flow aloft, and a low freezing level, should result in gusty wind and small hail in some of the storms. Shower activity will slowly dissipate overnight (ending later in NW PA) with the exit of the surface cold front and upper level trough axis. Cold advection by Sunday morning should return MVFR to localized IFR stratocu to most terminals. .Outlook... Diurnal mixing and influence of high pressure will return VFR conditions Sunday afternoon through Monday. Slow progression of the next upper level trough system means increases precipitation and restriction potential Monday night through Wednesday night, peaking Tuesday night into Wednesday. && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...None. OH...None. WV...None. && $$ SYNOPSIS...Craven NEAR TERM...WM SHORT TERM...WM LONG TERM...Craven AVIATION...Frazier