####018010983#### FXUS61 KPHI 161411 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 1011 AM EDT Fri May 16 2025 .SYNOPSIS... A warm front lifts north across the area this morning. Periods of showers, thunderstorms, and humidity continue through Saturday ahead of a strong cold front that passes through late Saturday afternoon into Saturday evening. High pressure builds into the area on Sunday and persists into Tuesday before another period of unsettled weather returns Wednesday into Thursday. && .NEAR TERM /THROUGH TONIGHT/... 1010 AM...A Severe Thunderstorm Watch is now in effect for most of the region. See the previous discussion below for details. Previous discussion from 9:40am...The morning fog is beginning to mix out from south to north as a warm front inches northward this morning. An MCS located now along the Susquehanna River Valley and pushing ESE. Concern is now growing that as the warm front lifts northward, the warm sector will intersect with the MCS, helping reinvigorate the cluster of storms and increase their severe potential. The associated outflow boundary from the MCS is also beginning to trigger off some convection, forming a broken line from Harrisburg to DC, providing another area of lift to form additional thunderstorms. The area of interest at this time is extreme southeast PA, mainly south of the PA turnpike, into the Delmarva Peninsula. Severe parameters will be present, with CAPE values increasing to 1000+ j/kg with bulk shear values around 35 to 40 knots. Damaging winds and large hail look to be the biggest threats but a brief tornado or two cannot be ruled out. Finally, given how wet it's been and that these storms will be capable of producing very heavy downpours, localized flooding will also be possible. As we get further into the day Friday towards the afternoon and early evening, the forecast becomes a little more uncertain. Following the initial round of showers/storms with the MCS there are indications that more scattered convection develops as we go through the afternoon. This later convective development could on the one hand be aided by residual boundaries from the earlier convection but could also be mitigated if the MCS takes longer to move through since this would give the atmosphere less time to recover. Otherwise, the morning fog will have been broken up with the first round of convection moving through and we may even see some sunny breaks or partial sunshine for a time in the afternoon. But again, this could fuel convective redevelopment and this second round of storms could also be severe. It will be a warm and very humid day with highs generally ranging from the mid to upper 70s north to the low to mid 80s south. Right near the shore though it will be a bit cooler. For Friday night, there may still be some convection ongoing into the evening but this should diminish with time leading to another brief lull. Once again, there could be some low clouds, mist, and fog that form due to the continuing moist environment. The action won't be over though because by later Friday night the main slug of energy more directly associated with low will be approaching and this could bring another MCS into the area sometime either overnight Friday night or Saturday morning. There remains a lot of uncertainty on this though. Otherwise, it will be a mild, muggy night with lows mainly in the 60s. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... Mid/upper level low over the Great Lakes will pivot east on Saturday as a vigorous shortwave tracks across the Mid-Atlantic with northwest flow developing in its wake on Sunday. At the surface, an area of low pressure will slide across Ontario/Quebec by Saturday night before meandering near Nova Scotia on Sunday. A strong cold front will pass through the area late Saturday afternoon into Saturday night. To start out Saturday, a MCS originating from the lower Ohio Valley is progged to approach our area on Saturday morning. The overall nature of this feature depicted by the latest CAM guidance is that it will be decaying or even dissipate as it approaches our area. A few showers and thunderstorms may be possible through the morning hours especially north and west, but since this feature is mesoscale driven, it's very difficult to depict where this feature may be come Saturday morning. Skies should be partly to mostly cloudy through the morning however, before clearing out by early afternoon. Temperatures will climb into the 80s for most areas with dew points in the low to mid 60s making it feel quite uncomfortable outside. The cold front will continue to make its way east through the afternoon where isolated to scattered thunderstorms will re-develop by the afternoon. In addition to the better forcing, we'll have MLCAPE values around 1000-1500 J/kg, DCAPE around 900 J/kg, and modest shear as indicated by point forecast soundings. These parameters will support damaging winds being the primary concern and possibly some severe hail. A brief tornado also cannot be ruled out as some low level shear will be in place. This is in line with the Storm Prediction Center which keeps the entire area in a Slight Risk (Level 2/5). Unfortunately, this threat is conditional and entirely dependent on the morning MCS and how it evolves, so the forecast may vary significantly by this time tomorrow. Nonetheless, the cold front will push off the coast by Saturday night and the threat for storms wanes in addition to the loss of daytime heating. Sunday is looking like the better half of the weekend as tranquil weather returns with the upper trough moving further east. Partly to mostly cloudy skies are expected with dry conditions and lower humidity. Perhaps an isolated shower is possible north and west, but general thinking is most of the area will stay dry. The one thing to note is winds will increase as diurnal mixing occurs as the area lies wedged between systems resulting in a tightening pressure gradient. Wind gusts up 30-35 mph will be possible. Gusts will diminish into Sunday night under mostly clear skies. Despite the windy conditions, high temperatures should mainly be in the 70s (with 60s in the Poconos). && .LONG TERM /MONDAY THROUGH THURSDAY/... By Monday, low pressure over the Canadian Maritimes will begin to move further east into the North Atlantic. At the same time, high pressure will settle over the Mid-Atlantic before moving offshore on Tuesday. Aloft, the area will be situated under northwest flow in wake of exiting upper trough. All in all, a tranquil weather period is in store with mostly clear skies, light winds and dry weather. By Tuesday night and through the middle of the week, our attention will turn to our next weather system which will take aim at the area. Global and ensemble guidance both feature a deep upper trough moving into the Great Lakes/Northeast region around the middle of the week with a potential coastal low developing before moving up towards New England. This would indicate another period of unsettled weather with periods of rain starting as early as Tuesday night, and more so on Wednesday and Thursday. Still quite a ways out from this potential, so have generally stuck with NBM guidance and capped rain chances at chance (~30-50%). In terms of temperatures, we'll encounter temperatures around average on Monday, before dipping below average for Tuesday through Thursday as the area remains situated within the deep upper trough. && .AVIATION /14Z FRIDAY THROUGH TUESDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Today...Restrictions to IFR/LIFR fore most sites to start the day then some improvement to MVFR expected between 14-17Z. However, around this time there will be a complex of showers and storms moving through as it moves in from the west but still some uncertainty on the details including how strong it will be at this time. Winds light and variable early in the day becoming SW 5 to 10 knots in the afternoon. There could be some additional showers/storms that form in the mid to late afternoon. Moderate confidence. Tonight...Any showers/storms diminish through the evening with with the potential for low cigs and low visbys once again due to stratus, mist and fog. Low MVFR or IFR appears likely. More showers and storms could move in late. S to SW winds around 5 knots. Low confidence. Outlook... Saturday through Saturday night...Primarily VFR expected. Scattered showers and thunderstorms likely, especially during the afternoon and early evening. Any shower or thunderstorm may cause temporary sub-VFR conditions, gusty winds and/or visibility restrictions. Sunday through Tuesday...VFR. Gusty winds up to 25-30 kt possible on Sunday. Otherwise, no significant weather expected. && .MARINE... Areas of dense fog over the waters likely to be an issue through the first half of Friday. Beyond this time, increasing chances for showers/storms over the waters in the afternoon. Generally sub SCA except any storms could produce locally strong winds. The risk for some showers/storms over the waters continues Friday night along with the potential for low visbys due to fog. Outlook... Saturday through Saturday night...No marine headlines expected. Sunday through Sunday night...SCA conditions possible due to wind gusts up to 25 kt. Monday through Tuesday...No marine headlines expected. && .TIDES/COASTAL FLOODING... The Coastal Flood Advisory for northwestern Burlington and lower Bucks Counties has been extended until 8 AM Saturday. Minor coastal flooding is expected with the early morning high tide this morning and on Saturday. It's possible minor coastal flooding may occur on Sunday as well, where further extensions may be needed. For areas of the lower tidal Delaware River near Philadelphia may encounter spotty minor coastal flooding through Saturday, but should fall short of advisory levels. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...Coastal Flood Advisory until 8 AM EDT Saturday for PAZ106. NJ...Coastal Flood Advisory until 8 AM EDT Saturday for NJZ019. DE...None. MD...None. MARINE...Dense Fog Advisory until noon EDT today for ANZ430-431-450>455. && $$ SYNOPSIS...DeSilva/Hoeflich NEAR TERM...Fitzsimmons/MJL SHORT TERM...DeSilva LONG TERM...DeSilva AVIATION...DeSilva/Fitzsimmons MARINE...DeSilva/Fitzsimmons TIDES/COASTAL FLOODING... ####018009817#### FXUS62 KMHX 161412 AFDMHX Area Forecast Discussion National Weather Service Newport/Morehead City NC 1012 AM EDT Fri May 16 2025 .SYNOPSIS... Inland troughing is expected today, followed by a cold front passage on Saturday. High pressure then builds in late in the weekend and into early next week. && .NEAR TERM /UNTIL 7 PM THIS EVENING/... As of 1015 AM Friday... KEY MESSAGES - Another conditional risk of severe weather late today - Humid with above normal heat today Previous shift's forecast remains in good shape for now. It should be noted that some new machine learning guidance (namely the 06z NCAR NN HRRR) has shown a noticeable uptick in probability of some severe weather impacting areas north of Highway 264 (50-60% chance, up from 30-40%), zoning in on an MCS crossing the Appalachians and riding the ridge along the NC/VA state line. 12z CAMs and guidance will hopefully offer more confidence in this potential solution. Prev disc...Yesterday's severe thunderstorms formed on the periphery of a stout mid/upper level ridge that has been anchored over the Southeast U.S. of late. That ridge is forecast to build a bit further north today, with an even stronger cap expected compared to yesterday. Meanwhile, heating of a moist boundary layer beneath a stout EML plume will once again support an area of moderate to strong instability over ENC, with MLCAPE reaching, or exceeding, 3000j/kg. The majority of deterministic guidance suggests a moderate to strong cap will remain in place through the day, which would be a significant limiting factor for sustained deep convection. Not all guidance shows this, though. Adding to the limitations is the mid/upper ridging near the region, providing an area of large-scale subsidence. The effect of ridging may be short-lived, though, as guidance suggests the ridge will flatten late in the day as an upper trough pivots east across the Ohio Valley. What appears likely is that there will be several clusters of severe thunderstorms well upstream associated with the upper trough. Guidance differs on the evolution of these clusters of storms, but upscale growth, and the upper pattern, favors one, or more, MCS' translating east from the OH/TN Valleys to the Mid- Atlantic/Carolinas. This convection will encounter the strong cap mentioned above, making it unclear whether or not convection can survive all the way to ENC. Should sufficient erosion of the cap occur, as some guidance suggests, there would be sufficient shear and instability to support MCS maintenance and an attendant risk of damaging winds. Some hail could occur as well, but wind appears to be the primary risk. Stay tuned for updates through the day on this potential. For now, we'll continue to hold with a low chance of thunderstorms focused north of HWY 70. This is also where the cap may be the "weakest", and where the greatest risk of severe weather would be focused. Otherwise, moderate to strong heating, plus warming thicknesses beneath the ridge, should support highs reaching the 90s inland, and 80s along the coast. With dewpoints in the 60s and 70s, this should allow the "feels like" temperature to reach the mid to upper 90s for much of the area. && .SHORT TERM /7 PM THIS EVENING THROUGH 6 AM SATURDAY/... As of 200 AM Friday... KEY MESSAGES - Conditional severe thunderstorm risk may linger into tonight The mid/upper level ridge over the region will continue to get flattened tonight as an upper trough shifts east from the OH Valley to the Northern Mid-Atlantic. Guidance suggests multiple MCS' may be ongoing upstream of ENC, and the environment may support some continuation of this activity into the eastern Carolinas with an associated risk of gusty to damaging winds. Given the expectation of a strong cap in place, any MCS may tend to weaken with time as it approaches the area, but stay tuned for updates on this potential. && .LONG TERM /SATURDAY THROUGH THURSDAY/... As of 0430 Friday...A series of weak cold fronts pushes through the area this weekend with a more significant system to impact the area late next week. Weekend...Upper low over Great Lakes drifts Eward toward New England coast with ridging over the Gulf remaining in place. Hot again on Saturday in downsloping flow, pushing highs into the lower or mid 90s with dew points still in the upper 60s leading to heat indices in the mid 90s. Line of showers and storms associated with the front approaching from the from the W forecast to dissipate before crossing over I95. However, guidance shows the clearing early Saturday will allow ample time for destabilization thanks to strong warm up. Continue to carry SChc- Chc showers/tstorms when the prefrontal trough environment begins to interact with the the seabreeze in the afternoon and early evening hours. SBCAPE on the order of 2-3kJ/kg with bulk shear>40-50kt shows potential for tstorm organization that could lead to damaging wind gusts and large hail should cells be able to flourish. The front is forecast to slowly sink S of the FA through Sunday before stalling over the region. Next week...Quiet and relatively cool compared to the weekend earlyweek with downsloping NWerly flow aloft between the departing low and shortwave ridging briefly amplifying over SECONUS. The next vertically stacked low to dig toward the Carolinas midweek upping cloudiness and rain chances again through the end of the week. && .AVIATION /14Z FRIDAY THROUGH TUESDAY/... SHORT TERM /through 12z Saturday/... As of 700 AM Friday... KEY MESSAGES - Low confidence TSRA risk over the next 24 hrs - LLWS impacts expected tonight Mid to upper level ridging will be nosing into the area today, with some subsidence and a fairly stout cap. It will be sufficiently unstable for TSRA, but ridging and the cap calls into question whether or not TSRA will impact ENC over the next 24 hrs. For now, we'll keep a VFR TAF going for all terminals given the low confidence forecast. The focus through tonight will be TSRA well upstream across the TN and OH Valleys. Some guidance suggests this activity will survive the trek across the Appalachians and the piedmont of the Carolinas, eventually reaching ENC late this afternoon or tonight. Should this scenario play out, the environment appears supportive of strong wind gusts of 30-50kt+ and sub-VFR conditions. Stay tuned for updates with later updates in case confidence were to increase regarding the TSRA potential. Outside of the TSRA potential, there will be an increased risk of LLWS impacts after 06z tonight as a modest southwesterly low-level jet overspreads the area. LONG TERM /Saturday through Tuesday/... As of 0400 Friday...Series of weak cold fronts push through the FA this weekend bringing chances of showers and tstorms which represent subVFR potential. && .MARINE... SHORT TERM /through tonight/... As of 130 AM Friday... KEY MESSAGES - Breezy winds and elevated seas to continue through tonight - The thunderstorm risk appears generally lower through tonight A modest pressure gradient across the area this morning will tighten later today through tonight, supporting a continuation of modest southwesterly flow (10-20kt) across area waters. For the coastal waters, this will keep seas elevated (3-5 ft). In general, the thunderstorm risk appears much lower today compared to yesterday. That said, at least some guidance suggests a cluster of thunderstorms may impact the central and northern waters later today through this evening. Should this occur, there would be an increased risk of 30-50kt+ wind gusts. LONG TERM /Saturday through Tuesday/... As of 0430 Friday...SCA issued for Saturday afternoon-Sunday morning. Boating conditions deteriorate Saturday ahead of the next cold front to cross area waters leading to SCA conditions in SWerly 15-25G30kt winds SAT afternoon and evening. Secondary backdoor front sinks S across waters late Sunday. High pressure builds in with Nerly surge late SUN night/MON AM. Generally 10-15kt winds slowly through early week N-NEerly Tuesday becoming Eerly Wednesday as offshore high departs SEward and next low approaches from the W. && .CLIMATE... Record High temps for May 16th, Friday. LOCATION TEMP/YEAR New Bern 95/1933 (KEWN ASOS) Cape Hatteras 84/1994 and 1991 (KHSE ASOS) Greenville 94/1962 (COOP - Not KPGV AWOS) Morehead City 89/1995 (COOP - Not KMRH ASOS) Kinston 96/1941 (COOP - Not KISO AWOS) Jacksonville 91/1998 (NCA ASOS) Record High temps for May 17th, Saturday. LOCATION TEMP/YEAR New Bern 95/1941 (KEWN ASOS) Cape Hatteras 86/1991 (KHSE ASOS) Greenville 95/1915 (COOP - Not KPGV AWOS) Morehead City 85/1991 (COOP - Not KMRH ASOS) Kinston 96/1941 (COOP - Not KISO AWOS) Jacksonville 93/1990 (NCA ASOS) && .MHX WATCHES/WARNINGS/ADVISORIES... NC...None. MARINE...Small Craft Advisory from noon to 11 PM EDT Saturday for AMZ135. Small Craft Advisory from 11 AM Saturday to 2 AM EDT Sunday for AMZ152-154-156-158. && $$ SYNOPSIS...MHX NEAR TERM...RM/MS SHORT TERM...RM LONG TERM...CEB AVIATION...RM/CEB MARINE...RM/CEB CLIMATE...MHX