Area Forecast Discussion
Issued by NWS Marquette, MI
Issued by NWS Marquette, MI
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700 FXUS63 KMQT 110511 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 111 AM EDT Sat May 11 2024 .KEY MESSAGES... - Showers increase in coverage from west to east this evening, with rain continuing overnight into Saturday morning for the central and eastern UP. - Scattered thunderstorms to develop Sunday afternoon, especially south central. There is a low chance (2%), for marginally severe hail and/or wind. - Dry weather returns Monday through Wednesday afternoon. && .SHORT TERM /THROUGH SATURDAY/... Issued at 338 PM EDT Fri May 10 2024 Early afternoon water vapor imagery shows a vigorous, compact, and strengthening shortwave trough now pivoting near the Twin Ports. DCVA forcing bands of clouds and showers from the western UP back into NW WI/western LS. Initial band appears to be mainly virga/sprinkles as it interacts with the antecedent dry airmass. 12 minutes of light rain was observed at IWD as this activity passed. Successive bands of showers should allow for gradual moistening and more widespread showers with time this afternoon and evening for the west and central, but totals will be hydrologically insignificant (although there could be a few brief heavier downpours). Some gusty winds could occur due to evaporational cooling with these showers, with a couple upstream automated observations recording 30 kt gusts. Thunder potential is still low, but cannot be ruled out mainly over the WI border counties this afternoon/evening. Surface reflection of this wave will strengthen late tonight into Saturday morning over northern Lower MI as the midlevel wave goes negatively tilted. This will result in the eastward progression of the showers slowing down as a mesoscale pivoting band develops along the NW flank of the low. This will keep rain in the forecast overnight for the eastern UP, while coverage gradually decreases in the central. Some of these showers will likely linger into Saturday morning for the eastern UP and possibly for the higher terrain of the north-central due to moist upslope flow. A good soaking rain could occur where the band pivots, as HREF 90 percentile shows a 0.75 to 1" area over Alger and Schoolcraft Counties. Otherwise, a high pressure ridge builds in from west to east through the day with an associated clearing trend (which may not be until in the afternoon for the central and east). Highs expected to be in the upper 50s/low 60s, except low/mid 50s along Lake Superior due to onshore flow. && .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/... Issued at 442 PM EDT Fri May 10 2024 Current ridging over western N America will force a couple of shortwaves to dive se into eastern N America over the next several days. The first drops into the Great Lakes region tonight/Sat. The second wave won`t drop as far s due to the upstream ridge losing some amplitude. It will pass across northern Ontario Sun/Mon. Thereafter, mid-level troffing developing into western Canada/northern U.S. Rockies early next week will shift downstream thru the week. There is and has been considerable model spread on the evolution of this trof, amplitude of the upstream ridge forcing the trof, and the progression of shortwaves around that ridge into the trof. Early on in the fcst period, a couple of periods of pcpn are expected, the first with the shortwave dropping thru the Great Lakes region tonight/Sat and the second with the shortwave reaching northern Ontario on Sun. A dry period will follow Mon/Tue and likely thru Wed aftn. Approaching mid-level trof will bring shra back to Upper MI Thu/Fri. Whether it ends up being sct or widespread pcpn will depend on the highly uncertain evolution of the trof. As for temps, readings most days thru the middle of next week will be around normal, then there is more uncertainty late week depending on rain coverage/potential sfc low developing into the Great Lakes region. Warmest day will be on Sun. Closer to Lake Superior, it will be on the cool side for at least Mon/Tue as high pres ridging building southward into the Great Lakes brings a gradient onshore wind component. Beginning Sat night/Sun, shortwave over the NW Territories tonight will reach northern Ontario Sun morning. In response, a 30-40kt low- level jet develops, leading to a good push of waa/isentropic ascent and theta-e advection into Upper MI late Sat night/Sun morning. As a result, sct -shra should develop into roughly the w half of Upper MI overnight Sat night, spreading eastward Sun morning. After this initial waa/isentropic ascent pcpn moves across the area, attention on Sun aftn turns to lake breeze aided cold front that moves across the area. Timing of this feature will be coincident with peak heating Sun aftn across the central, s central in particular. The NAM/GFS have MLCAPE increasing to 500-1000j/kg, though the NAM peaks at around 1500j/kg. The CMC RDPS and ECMWF are less than 500j/kg. With consensus deep layer shear of 30-40kt, an isolated svr storm is a possibility if the higher MLCAPE materializes. That will depend on how much cloud cover and even shra from earlier in the day linger into the aftn. Expect highs on Sun in the mid 60s to mid 70s for much of the area, though it will turn cooler closer to Lake Superior once winds shift off of the lake. Shra/tsra will exit the s and e Sun evening. A secondary cold front will pass uneventfully during the night, setting up dry days on Mon/Tue as sfc high pres builds s into the western Great Lakes. Will be cool near Lake Superior on Mon/Tue, especially e half, under gradient northerly winds due to high pres ridge building s into the area. Expect 40s F to be the rule. Temps both days will range up to the low/mid 60s well inland w half. There is plenty of dry avbl to mix down, especially on Tue. RH may fall blo 30pct interior w, but winds will be lighter in that area than over the rest of the U.P. to limit fire weather concerns. The 12z medium range model runs not did show any trend toward agreement with the approaching mid-level trof mid and late week. Agreement is there for dry weather to linger thru Wed aftn. Lingering dry air aloft is avbl to mix down, so it cloud be another day with RH under 30pct in the interior. Thereafter, fcst will reflect broad brush mostly 30-40pct chc shra for Thu/Fri. && .AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 110 AM EDT Sat May 11 2024 Wraparound moisture from low pressure deepening over northern Lake Mi will continue scattered showers overnight mainly into central Upper Mi. SAW will be most impacted from this system seeing VFR conditions lower to MVFR in these showers and perhaps briefly to IFR overnight before quickly improving back to MVFR late Saturday morning and to VFR Saturday afternoon as high pressure builds back in from the west. Expect VFR conditions to mostly prevail at IWD and CMX. && .MARINE... Issued at 442 PM EDT Fri May 10 2024 Expect winds mostly under 20kt thru Wed. However, there are a couple of periods where winds will be a little stronger. Approaching cold front Sat night will result in increasing southerly winds. Across mainly the e half of Lake Superior, gusts up to around 25kt are possible by Sun morning, but these stronger winds would be at the high obs platforms due to the stability within the chilly marine layer. Then on Mon, high pres ridge building s into the western Great Lakes may support higher nw wind gusts to 25kt over far eastern Lake Superior. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...Thompson LONG TERM...Rolfson AVIATION...Voss MARINE...Rolfson