Area Forecast Discussion
Issued by NWS Portland, ME
Issued by NWS Portland, ME
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060 FXUS61 KGYX 291609 AAB AFDGYX Area Forecast Discussion...UPDATED National Weather Service Gray ME 1209 PM EDT Sat Jun 29 2024 .SYNOPSIS... A warm front will approach from the west today as high pressure drifts away from the area. This front will bring increasing clouds along with chances for showers and embedded thunder late this afternoon and tonight. A cold front crosses Sunday bring scattered strong to severe thunderstorms. High pressure builds in Monday and Tuesday for fair weather into the middle of next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 12 PM Update: Continue to boost shower chances and cloudiness while lowering temperatures for the afternoon based on noontime observations and regional radar/satellite data. Large area of light-moderate rain across New York will arrive from southwest to northeast later this afternoon into the evening for all but possibly our southeastern zones. Until then...cloudy skies prevail with a few sprinkles. 930 AM update: A few sprinkles have pushed across southern NH into western ME this morning /even here at the WFO/ as relatively robust radar returns work against a substantial dry H8-7 layer on the 12Z GYX raob. Boosted cloud cover base on morning GOES 16 visible satellite imagery...but other than these sprinkles...expect cloudy but dry conditions through the morning with more showers pushing in from the west /now over central NY/ this afternoon. Remainder of the forecast including high temperatures look good. 635 AM Update...Latest radar shows healthier returns moving into western NH with surface obs confirming this precipitation is reaching the ground. Have therefore increased PoPs across NH into far western Maine through this morning to account for these trends. Otherwise have tweaked T/Tds to capture the latest round of observations. Previously... Latest water vapor imagery shows a short wave crossing Minnesota early this morning with mainly zonal flow across the eastern Great Lakes into New England. At the surface high pressure centered east of Cape Cod will drift eastward today while a warm front approaches from the west. The approaching front will allow for clouds to thicken and lower through today. Latest radar shows weak returns over much of New England while ample dry air aloft around 700 mb noted on the 00Z KGYX sounding and at the surface is limiting this precipitation to reach the ground. Moisture advection will continue through today allowing for the atmosphere to saturate enough for showers to break out west to east late this morning into this evening. As has been mentioned over the past few forecast cycles, deep moisture will become quite impressive tonight with PWATs climbing to 1.75 to 2.25 inches along with warm cloud depths greater than 12kFT and increasing elevated instability. These ingredients combined will favor heavy rainfall rates while forcing for ascent will be weak while these ingredients are in place. The 00Z HREF maximum 24-hour QPF ending Sunday morning paints much of the area with less than 1.25 inches while the HREF mean is only around 0.5 inches. The exception here is in the mountains where there could be localized amounts greater than 1.5 inches. Therefore, the overall threat for flooding with rainfall today through tonight is low, while it should be monitored given the heavy rainfall ingredients. Otherwise, today will feature mostly cloudy skies with increasing chances for showers west to east with highs in the 60s and 70s north to south. Widespread showers with embedded thunder area likely tonight with increasing humidity bringing the potential for patchy fog. The warm front and associated forcing will lift northeast of the area Sunday morning reducing the chances for showers towards day break. Lows tonight will range from the mid 50s to upper 60s north to south. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/... The 00Z CAM suite is in decent agreement that much of the area will start off Sunday with little in the way of shower activity as the forecast area becomes enveloped within the warm sector of low pressure moving through Quebec. Dewpoints are modeled to rise into the upper 60s to low 70s through Sunday morning while breaks in the clouds will allow for surface heating. The 00Z HREF suggests there will be sufficient destabilization with mean MU CAPE climbing to 1500-2000 J/kg by early afternoon. All the while a vort max will be racing across Quebec with a cold front crossing the region Sunday afternoon. The plume of MU CAPE will be well placed beneath a corridor of deep layer shear of 40-50 kts, which will be more than sufficient for organized convection across the area. The 00Z is quiet bullish with scattered convection with strong rotating updrafts developing from the Canadian Border through SW New Hampshire with these storms tracking ESE to the coast. This has resulted in SPC expanding the Slight Risk across all of Maine and much of New Hampshire, with just portions of far NW New Hampshire in the Marginal Risk. The primary threat will be damaging winds while less than impressive mid level lapse rates will make hail a secondary threat. Low level winds look to be mainly out of the SW with mainly straight hodographs limiting the potential for spin-ups, although some backed flow near the coastal plain brings a non- zero threat. In addition to building humidity temperatures will climb into the low to mid 80s with the added humidity bringing heat indices close to 90F. Storms look to clear the coast by 00Z Monday. && .LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/... I suppose its safe to say we have worked our way into a typical summer pattern as 500 MB ridging take residence S of the Mason- Dixon line, and troughs in north-shifted jet stream. Are generally flatter and more mobile. We start off a little on the cool side but the trend will be fore warming to near and above normal 850 MB temps by mid to late week. The tricky part is what becomes of the closed low that shifts to our SE late in the week and whether it acts as a block to allow S_SW flow to settle, making for another round of hot/humid weather or keep flow more zonal which will lead to more typical summer wx. As for chances of shra/tsra, beyond Sunday, we do see some of wave move to our N around Wed-Thu. The cold front will push offshore Sunday night with cooler and drier air moving in at least for Mon- Tue, with highs a little below normal on Monday, but nice otherwise, and warming back to near normal on Tuesday. Wed will be warmer still with a bit of increase in humidity, but should stay dry most of the day. Wednesday night and Thursday are the next chance of precip, but theres still a lot of uncertainty with this weaker system. && .AVIATION /16Z SATURDAY THROUGH WEDNESDAY/... Short Term...Clouds thicken and lower from west to east today with conditions dropping to MVFR and then IFR tonight. Scattered rain showers are likely late this afternoon and overnight with embedded thunder. Conditions improve Sunday morning before a cold front brings strong to severe storms tracking WNW to ESE across the area between 18Z Sunday and 00Z Monday. Long Term...Mainly VFR Mon-Wed. Also valley fog possible at KHIE/KLEB Sun and Mon night. && .MARINE... Short Term...High pressure moves east of the waters today with increasing southerly flow bringing SCA conditions from this afternoon through Sunday. A cold front crosses the waters Sunday evening bringing the threat for strong storms tracking into the waters. Long Term...SW winds drop off Sun night, and stay below SCA levels through mid-week. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Small Craft Advisory until 11 PM EDT Sunday for ANZ150>154. && $$ SYNOPSIS... NEAR TERM...Arnott/Schroeter SHORT TERM...Schroeter LONG TERM... AVIATION... MARINE...