Area Forecast Discussion
Issued by NWS Marquette, MI
Issued by NWS Marquette, MI
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860 FXUS63 KMQT 112331 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 731 PM EDT Sat May 11 2024 .KEY MESSAGES... - A few rumbles of thunder possible late tonight west, then scattered thunderstorms to develop Sunday afternoon into early evening, especially south central. There is a marginal risk (5%) of large hail and/or damaging wind south central. - Dry weather returns by Monday, continuing through Wednesday afternoon. && .SHORT TERM /THROUGH SUNDAY/... Issued at 424 PM EDT Sat May 11 2024 Water vapor imagery and RAP analysis show nw flow from western Canada to the Great Lakes region. The vigorous shortwave that brought shra to Upper MI last night is now tracking into southern Ontario. A much weaker shortwave is currently over central Lake Superior/central Upper MI. Upstream, the next vigorous shortwave is dropping se into northern Manitoba. Shortwave currently over the area combined along with MLCAPE increasing to 100-300j/kg per latest RAP has supported isold/sct shra development across central Upper MI this aftn. A few rumbles of thunder have occurred from around Escanaba into Menominee County where MLCAPE is maximized. To the e, low stratus is noted along Pictured Rocks extending e and ne over the lake. Current temps range from the 40s e along Lake Superior to the lower 60s F well inland over western Upper MI. Ongoing isold/sct shra over central Upper MI will end over the next few hrs. Attention then turns to the shortwave currently over northern Manitoba. It will reach northern Ontario Sun morning. In response, a 35-45kt low-level jet develops into Upper MI late tonight/Sun morning, leading to a good push of waa/isentropic ascent and rather sharp theta-e advection. As a result, sct -shra should develop into roughly the w half of Upper MI overnight, spreading eastward Sun morning. Initial surge of theta-e advection may support some -shra into western Upper MI this evening, but there is a good layer of dry air from around 800mb to the sfc. Might be a few sprinkles. Expect min temps tonight ranging from the low/mid 30s e where skies will be mainly clear longest to the mid/upper 40s far w where clouds increase before sunset. After the 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 across the central, s central in particular. Consensus model guidance has MLCAPE increasing to around 400-700 j/kg Sun aftn though NAM/RAP are up to 1000j/kg. Deep layer shear of 30-40kt will support storm organization and an isolated svr risk for large hail and damaging winds. Wetbulb zero heights at 7-9kft are supportive of a large hail risk while dry subcloud air/inverted v profile will enhance potential of strong winds. Expect highs on Sun in the 60s along Lake Superior w and also across the e into the mid 70s F interior west half. && .LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/... Issued at 331 PM EDT Sat May 11 2024 A couple cold fronts will press through the Upper Great Lakes Sunday evening, allowing a cool to seasonable airmass to break into the region through at least mid-week. Ahead of the initial cold front on Sunday, afternoon shower and thunderstorm development may occur if we`re able to destabilize enough following the Sunday morning isentropically/warm frontally forced showers. By 0z Sunday and the start of this forecast period, the cold front looks to be draped across the central UP with the aforementioned shower/thunderstorm region out ahead stretching from Menominee County northeastward into the eastern UP. The environment at this point should be less conducive for any new convective development given the quickly waning influence of the day`s diurnal heating. However, if a strong or severe storm does develop earlier, guidance suggests enough deep layer shear could sustain updrafts into the evening hours. However, the window will be short lived given the cold front`s fast eastward progression. By 3z, CAMS all suggest convective activity should be outside of the forecast area. Behind the cold front, a dry airmass will press into the region while a secondary cold front moves through after midnight Sunday night. This, in addition to surface ridging building over the area, will sustain a dry couple of days for the forecast area. The daytime high temperature gradient Monday and Tuesday should stretch from near 50F by Lake Superior to the low-mid 60s across the south- central. On Wednesday, more widespread 60s are expected, with most areas outside of the immediate lakeshores and Keweenaw looking to climb into the low-mid 60s. Overnight lows should be mostly in the 30s, with chances for sub-freezing temperatures in the interior- central spots (20-30% chance). Fire weather concerns should be mitigated by the near to slightly cooler then normal conditions and light winds these days. But daytime mixing into a dry airmass aloft may support RH values nearing 30% for some interior central and west locations. Mid-level ridging shifts through the region on Wednesday followed by a shortwave pressing through Minnesota/western Ontario Wednesday night. Consensus among the 12z deterministic guidance suite has this pressing into our forecast area Thursday, supporting another round of showers through the day. This contrasts some with the GEFS, EC, and GEPS ensemble systems, where some members suggest precip could start Wednesday night. && .AVIATION /00Z TAFS THROUGH 00Z MONDAY/... Issued at 729 PM EDT Sat May 11 2024 VFR conditions will prevail thru this fcst period at IWD/CMX/SAW. As low pres drops into far northern Ontario tonight, a low-level jet will develop into Upper MI late tonight into Sun morning, resulting in 2-6hrs of LLWS at all terminals, lasting longest at IWD. The low- level jet will also generate sct showers, but confidence in a shower passing over any of the terminals is low. Not expecting conditions to drop out of VFR if a shower does occur. More showers/possible t-storm will develop Sun afternoon across central Upper MI, possibly affecting SAW. && .MARINE... Issued at 331 PM EDT Sat May 11 2024 Winds are mainly expected to remain below 20 kts through the entire forecast period, with some exceptions. A warm front will lift through the lake late tonight and early Sunday. Ahead of and behind the front, some isolated 20-25 kt wind gusts will be possible. The stronger pressure gradient will be Sunday across the east half and behind the warm front; however, the increasingly stable airmass over the lake should work against mixing the stronger southerly winds to the surface. Given the environment, higher reporting platforms would be more likely to observed these stronger winds then the surface buoys. A cold front will press from west to east through Lake Superior through the day as well. A shower or thunderstorm can`t be ruled out by afternoon across the east half, but with the focus for convection being over Upper Michigan and not Minnesota, the probability is low (20-30%). Behind the front, high pressure will settle over the lake, supporting a few days of mostly 20kts or less over the lake through at least midweek. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... Small Craft Advisory from 2 PM to 11 PM EDT Sunday for LMZ248- 250. && $$ SHORT TERM...Rolfson LONG TERM...JTP AVIATION...Voss MARINE...JTP