####018008499#### FXUS63 KMQT 151929 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 329 PM EDT Thu May 15 2025 .KEY MESSAGES... - Strong to severe storms are expected from SW to NE this evening, most likely in the south-central U.P. The strongest storms will pose a large hail and damaging wind threat. - Another round of showers and storms, potentially strong to severe, returns for Friday afternoon and evening. - Dense fog remains present across the open waters of Lake Superior at least through this evening. && .SHORT TERM /THROUGH TONIGHT/... Issued at 329 PM EDT Thu May 15 2025 Water vapor and RAP analyses have a negatively tilted trough swinging over the Dakotas and into western MN, with an upper low closing off over SD and a prominent dry slot moving northeastward through south-central MN. An occluded low is analyzed over the eastern Dakotas, with an occluded front extending southeast across MN into far northeast IA. Will also note a 40-45kt 850mb LLJ analyzed across MN. Closer to home, skies have largely cleared out as daytime mixing has allowed fog/low stratus that plagued most of the UP earlier today to mix out. However, a cu field has developed across the area with deepening mixing. If we need further evidence that we're destabilizing nicely, RAP analysis has as much as 2000j/kg of SBCAPE over most of the UP. This could spell bad news for later this evening, but more on that shortly. Meanwhile, under sunny skies, temperatures are having no trouble reaching well into the 70s, apart from areas where SE flow is onshore of the Great Lakes (the eastern Keweenaw, the Lake Michigan shorelines). There, temperatures are only reaching the 60s. The occluded front continues to work northward the rest of the afternoon, finally reaching the MI/WI border closer to 00Z on the nose of the dry slot and LLJ. Model guidance is pretty enthusiastic about more discrete convection developing across MN and WI along the front this afternoon coalescing into a broken arc of showers and storms that will quickly move northeastward through the UP from around 00-06Z. We'll be running out of daylight by the time this reaching the UP, so there is some uncertainty regarding how much surface-based instability we'll have left to play with. However, HREF still favors MUCAPE up to 1000/1500j/kg as the line moves through. Modestly curved low level hodographs, bulk shear values 30- 40 kts, and 1-3km SRH upwards of 300 m2/s2 suggest embedded supercells within the line of storms, posing a very low end tornado threat. That said, the main hazards will be hail (1-2") and damaging winds >60 mph. Meanwhile, a more widespread QPF footprint is expected, with a widespread 0.25-0.50in expected and higher totals in the heavier downpours. As storms will be moving rather quickly, flash flood threat remains rather low, but we'll want to pay attention to rainfall rates in areas that received excessive rainfall due to training thunderstorms last night. Latest SPC guidance has all of Upper Michigan (save for the far NE and Keweenaw) within a Slight Risk (risk level 2 of 5). An Enhanced Risk (risk level 3 of 5) extends along the MI/WI border southward. Otherwise, non-thunderstorm winds will be on the increase as well as we head towards the evening hours, with gusts of up to 20-25mph becoming common and higher gusts to 30mph possible particularly in the higher terrain across the western UP. Winds fall back slightly behind the boundary the second half of the night. Expect skies to largely clear out once again with temperatures falling back into the lower to mid 50s. && .LONG TERM /FRIDAY THROUGH THURSDAY/... Issued at 329 PM EDT Thu May 15 2025 By Friday morning, stacked low pressure will be spinning over northern MN. A dry slot moving over the UP will lead to a dry start to the day, but then another round of showers/storms develops into the afternoon as the system finally begins to move through the Great Lakes and drags a cold front through. CAA aloft will allow for steep midlevel lapse rates, and a 40-45kt LLJ will be directed over the eastern half of the UP...but soundings show quite a bit of dry lower level air that will need to be overcome. Will continue to be worth monitoring, with SPC having the eastern UP in a Marginal (category 1 of 4) risk for severe. Otherwise, strong southerly winds develop Friday afternoon as a 10/mb pressure gradient sets up over the UP, and while the depth of mixing is questionable, we could still tap into stronger winds aloft. A sharp cold front presses through the area on the backside of the low early Saturday, bringing additional rainfall and ushering in much cooler temps in the 40s-60s (warmest south-central) for the late weekend and early work week. Troughing over the west pushes the weak central CONUS ridge (and resulting low-1020s mb surface high) over the UP by Sunday, with dry weather Sunday into the work week. With dry, well-mixed soundings Monday afternoon, we will want to pay attention to a potential for a good dewpoint drop and potentially some fire weather concerns. However, will (perhaps needlessly) point out that this comes in the wake of a couple rounds of precipitation. Attention then turns upstream to the next low pressure to eject out of the Plains and into the Lower Midwest by midweek. However, the exact timing, track, and thus impacts remain uncertain as some of the deterministic and ensemble guidance is suggesting that our exiting high pressure (by then centered somewhere over eastern Ontario/Hudson Bay) could suppress this southward. && .AVIATION /18Z TAFS THROUGH 18Z FRIDAY/... Issued at 128 PM EDT Thu May 15 2025 Fog and low stratus have lifted at all terminals this afternoon, with just some agitated cumulus developing across the area as daytime mixing deepens. Thus, a period of VFR is expected at least through the remainder of the afternoon with generally dry and sunny conditions. Heading into the evening, a line of showers and thunderstorms (some strong to severe) move through between 00-06Z. Any convection could lead to quick reductions to MVFR or worse, depending on rainfall rates. Following this passing line, MVFR ceilings may linger at SAW the rest of the night. Meanwhile, southerly winds will be on the increase. Expect gusts up to 20-25kts at IWD and CMX this afternoon into tonight, with winds backing off slightly late tonight. A period of low level wind shear is expected from around 06-12Z, then wind gusts at the surface pick up again to 20-25kts into the daytime hours at all terminals. && .MARINE... Issued at 329 PM EDT Thu May 15 2025 Deepening low pressure over the Plains is leading to increasing NE winds across the lake, with gusts generally around 20-25kts this afternoon. Winds begin to turn more to the SE this evening, with gusts increasing to around 25-30kts for much of the lake ahead of an approaching frontal boundary. This front produces a line of thunderstorms, potentially strong to severe, which is expected to move through late this evening through around midnight. Winds briefly fall back to around 20kts the second half of tonight, but pick up again to around 20-30kts out of the south across the eastern half of the lake. A few gale-force gusts are not out of the question, especially in the southerly downsloping areas in the nearshore waters north of the Upper Peninsula. Winds then briefly relax below 20 kt until post-low winds out of the northwest ramp up to 25-30 kts again Saturday through early Sunday. Uncertainty then grows in regards to the next low pressure moving out of the Plains, which could lead to elevated winds again early next week. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... Dense Fog Advisory until 8 PM EDT this evening for LSZ265>267. Dense Fog Advisory until 11 PM EDT /10 PM CDT/ this evening for LSZ162-263-264. Lake Michigan... Dense Fog Advisory until 8 PM EDT this evening for LMZ221-248- 250. && $$ SHORT TERM...LC LONG TERM...LC AVIATION...LC MARINE...LC ####018006613#### FXUS61 KALY 151930 AFDALY AREA FORECAST DISCUSSION National Weather Service Albany NY Issued by National Weather Service Burlington VT 330 PM EDT Thu May 15 2025 .SYNOPSIS... An unsettled weather pattern will continue across the region with daily chances for showers and thunderstorms on Friday into the upcoming weekend. A few stronger storms are possible on Friday and Saturday afternoons across the area. Temperatures will remain above normal through Saturday, before cooler air arrives on Sunday. Highs generally in the mid 70s to lower 80s with lows mostly in the upper 50s to mid 60s on Friday and Saturday. && .NEAR TERM /THROUGH FRIDAY NIGHT/... Breaks in the overcast have helped to warm temps into the 70s to a few values near 80F this aftn with dwpts in the 60s, resulting in sfc based CAPE values in the 1200-1800 J/kg per LAPS analysis. This instability has allowed for showers and thunderstorms to develop in a pulse like storm environment, that features very weak deep layer shear of <15 knots. However, with very slow moving storm motions <15 knots, localized areas of heavy rainfall are possible thru early this evening. Convective activity should slowly weaken and dissipate after sunset with loss of sfc heating. Sounding data shows plenty of llvl moisture developing under subsidence inversion, so anticipating areas of low clouds and fog, especially deeper protected valleys. Expect similar conditions overnight at KPOU as the previous night with areas of low clouds and patchy fog/br likely. Also, areas that received rainfall this aftn, have higher probability of fog/br tonight with light winds. Lows generally in the upper 50s southern Dacks to lower 60s Capital District/Hudson Valley. For Friday SPC has placed locations mainly along and south of the Mohawk Valley in marginal risk (1 out of 5) for severe storms. The pre-storm environment wl feature slightly better deep layer shear in the 20-30 knot range with sfc based CAPE values of 1500 to 2000 J/kg. In addition, better synoptic scale ascent wl arrive via 700 to 500mb s/w energy in the southwest flow aloft. This lift and instability/shear parameters supports increasing areal coverage of convection by early aftn with some stronger storms possible. Primary threat given thermodynamics would be small hail, localized gusty winds, and brief heavy downpours, especially with pw values in the 1.0 to 1.50" range. Highs wl be very similar to today with values in the upper 70s to lower 80s. Friday night is quiet with less fog/mist potential given increasing boundary layer flow of 4 to 8 knots. && .SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/... Key Messages: - SPC has increased the marginal to slight risk (level 2 of 5) of severe thunderstorms Saturday for parts of the area. Some storms may produce damaging winds and/or large hail, along with frequent lightning and localized heavy rainfall. Discussion: Another active day is anticipated with several rounds of showers and storms likely. SPC has increased the risk to slightt (2 out of 5) for severe weather. Synoptic pattern shows approaching mid/upper lvl trof with several embedded 5h vorts rotating acrs our cwa. These strong dynamics wl interact with favorable deep layer shear of 35 to 45 knots and CAPE values of 1200 to 2000 J/kg to produce localized strong to possibly severe storms. Still some uncertainty on amount of clearing/destabilization behind morning convection, along with timing of aftn/evening energy. The pre- storm environmental conditions suggest strong shear and weak- moderate instability with good dynamics, helping increase the probability of some organized convection. In addition, localized heavy rainfall wl be possible as WPC keeps central/northern cwa in marginal risk of exceeding flash flood guidance. Highs on Saturday in the 70s to near 80F. Lows drop back into the 50s on Saturday night with lowering sfc dwpts on west/northwest winds behind boundary. && .LONG TERM /SUNDAY THROUGH THURSDAY/... Closed mid/upper lvl circulation moves directly overhead on Sunday with diurnal driven showers likely during the late morning into the aftn hours. The greatest concentration of precip/qpf wl be acrs the higher trrn of the southern Dacks/southern Greens and eastern Catskills. Highs wl be much cooler on Sunday with values in the upper 50s to mid/upper 60s. Cyclonic northwest flow and associated cold air advection continues on Monday into Tues with progged 850mb temps approaching 0C. A few lingering showers are possible acrs the favorable upslope areas of the Dacks/southern Greens on Monday with cool highs only in the 60s. Tuesday is quiet with weak high pres nosing into the area, followed by more unsettled wx for mid to late week associated with our next full latitude trof. Still some uncertainty with development and timing of system, but probability of another period of unsettled wx is increasing for mid to late week. && .AVIATION /20Z THURSDAY THROUGH TUESDAY/... Currently MVFR cigs at KPOU and KPSF, while VFR conditions prevail at KALB and KGFL this aftn with light and variable winds. Expect cigs to slowly improve to VFR conditions at all sites in the next 1 to 3 hours with a few isolated to widely scattered showers and embedded rumbles of thunder. Have utilized PROB30 groups this aftn/evening to cover this potential as winds remain light under 8 knots. Tonight CIGS lower to MVFR with greatest potential for IFR/LIFR cigs at KPSF and KPOU between 06-12z Friday. Vis will be mostly VFR but MVFR/IFR vis possible at KPSF/KPOU in a mix of mist and fog. Conditions trend toward MVFR between 12-15z and all sites should have VFR conditions by 15z Friday as south winds increase 5 to 10 knots. Outlook... Friday Night: Moderate Operational Impact. Chance of SHRA...TSRA. Saturday: High Operational Impact. Definite SHRA...TSRA. Saturday Night: Moderate Operational Impact. Chance of SHRA. Sunday: Moderate Operational Impact. Breezy. Chance of SHRA. Sunday Night: Low Operational Impact. Breezy. NO SIG WX. Monday: Low Operational Impact. Breezy. NO SIG WX. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. MA...None. VT...None. && $$ SYNOPSIS...WFO BTV NEAR TERM...WFO BTV SHORT TERM...WFO BTV LONG TERM...WFO BTV AVIATION...WFO BTV ####018004598#### FXUS63 KGRR 151931 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 331 PM EDT Thu May 15 2025 .KEY MESSAGES... - Severe Thunderstorms this Evening - Another Round of Strong to Severe Storms Friday Evening - Windy Saturday, Cooler into Next Week && .DISCUSSION... Issued at 331 PM EDT Thu May 15 2025 - Severe Thunderstorms this Evening Tonight between 8pm and 2am a round of thunderstorms is expected to move through the area bringing with it the potential for damaging winds, large hail, and tornadoes. The main source of lift for these storms will be with the occluded front with upper level divergence aloft along with some convergence in the wind fields at 850-700mb. Instability has been gradually building through the day with Mixed Layer CAPE values currently in the 1500 to 2000 J/kg range across much of the area. Thunderstorms are beginning to develop along the front in Minnesota and are expected to expand south along the front as it moves east this afternoon and into this evening. 0-1km storm relative helicity values peak ahead of the front in the 100 to 150 m2/s2 range and around 200 m2/s2 from 0-3km. Paired with 30 to 40 knots of effective shear and Most Unstable CAPE values around 2000 J/kg this will be a prime environment for rotating updrafts, hence the increased hail and tornado risk. There is some variability in the storm mode as it heads into western Michigan. Individual storms are expected to develop in Wisconsin and may become clustered or form a line as they move across the lake into western Michigan. If storms take a more linear formation, then winds and quick spin up tornadoes would become the main concern. Any isolated or clustered supercells would be more likely to produce all hazards, especially hail. With the risk for severe storms late this evening, make sure you have a way to receive warnings and a plan in place to take shelter when warnings are issued. - Another Round of Strong Friday Evening Most of Friday will be dry with instability building through the day. Steep lapse rates and ample dry air causing an inverted V in soundings will set the stage for an environment favorable for downbursts. Lift provided by the positive vorticity advection swinging around the 500mb low will move in around 8pm Friday causing showers and thunderstorms to develop. Similar to Thursday evening storms taper off shortly after midnight. - Windy Saturday, Cooler into Next Week The same low mentioned in the previous section will gradually track across the northern Great Lakes Saturday. Lingering showers associated with the low should clear early Saturday afternoon, but as the rain and lower clouds clear, gusty westerly winds will develop. Some gusts to 40 mph are possible during the afternoon. Calmer conditions move in for the remainder of the weekend with highs in the 60s and lows in the 40s and 50s. && .AVIATION /18Z TAFS THROUGH 18Z FRIDAY/... Issued at 144 PM EDT Thu May 15 2025 VFR conditions are expected with southeast winds and SCT-BKN cumulus around 3000 to 5000 feet this afternoon. Thunderstorms move in from 00-04Z from west to east tonight. These storms could product gusts greater than 50 knots, large hail, and tornadoes. Additionally storms could briefly bring MVFR ceilings and IFR visibilities. Thunderstorms will linger over any one location for about an hour. Winds become southwesterly as thunderstorms exit to the east overnight with clearing skies. && .MARINE... Issued at 331 PM EDT Thu May 15 2025 A round of thunderstorms is expected between 8 and 10pm with the potential for large hail, damaging winds, and waterspouts. Rough water is expected with this round of storms with southwest winds moving in behind the line. A second round of storms moves in Friday night with the potential for storms to be strong with gusty winds being the primary concern. The low pressure system responsible for these rounds of storms will move through the northern Great Lakes Saturday bringing with it a tight pressure gradient and gusty Westerly winds. A Small Craft Advisory is in effect for Friday through Saturday evening due to winds and high waves. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...Small Craft Advisory from 11 AM Friday to 2 AM EDT Sunday for LMZ844>849. && $$ DISCUSSION...RAH AVIATION...RAH MARINE...RAH