Area Forecast Discussion
Issued by NWS Marquette, MI
Issued by NWS Marquette, MI
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982 FXUS63 KMQT 021914 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 314 PM EDT Thu May 2 2024 .KEY MESSAGES... - A Plains low pressure system moving through the Upper Great Lakes will bring widespread rainfall from this afternoon into tonight of .2 to .5 inch, highest west half. - Active pattern continues through next week as a series of low pressure systems track across the U.S. and affect Upper MI. Above normal precipitation expected, including chance of thunderstorms at times. - Mostly above normal temperatures expected, generally 5 to 10 degrees above normal on the majority of days thru the middle of next week. && .SHORT TERM /THROUGH TONIGHT/... Issued at 311 PM EDT Thu May 2 2024 Tonight, a vigorous shortwave now over the central/eastern Dakotas will lift east-northeast and reach western Lake Superior Fri morning. Main surge of waa/isentropic ascent and strong 850-700mb moisture transport ahead of this shortwave advances across Upper MI this afternoon/evening, as widespread showers now over west and south central spread east across the rest of the fcst area late this afternoon/early evening. There isn`t much elevated cape (basically less than 200 j/kg), but this may lead to a few rumbles of thunder over the east half later this evening into the early overnight where models peg weak elevated CAPE values. Occluded front associated with shortwave will reach western Upper MI around 06z, will extend roughly thru Munising to Manistique by 12z Fri and will exit Luce County by 15z. Showers will abruptly end with the passage of the occluded front as model soundings show sharp mid-level drying surging into the area. Lower levels will dry out quickly as well on Fri as daytime heating builds mixed layer and taps very dry air aloft. Expect skies to trend sunny Fri morning over the w half and early to mid aftn across the e. Expect lows tonight to range from the lower 40s west to mid to upper 40s south central and east. && .LONG TERM /TONIGHT THROUGH WEDNESDAY/... Issued at 458 AM EDT Thu May 2 2024 Last 24-48hrs of medium range model guidance maintains an active pattern across the Lwr 48 thru next week as a series of vigorous waves track off of the N Pacific and then across the U.S. Late next week into the mid month period, it appears this pattern will breakdown. The active pattern will be beneficial in easing ongoing drought over western and eastern Upper MI as frequent rainfall events are expected. An updated drought monitor will be issued this morning, but the last one from 4/25 indicated drought conditions in western Upper MI were into the severe category in portions of Gogebic/Ontonagon counties. To the e, moderate drought was indicated from eastern Delta to western Mackinac counties. The frequent pcpn events will also ease spring fire weather concerns. So, expectation is for pcpn from now thru the end of next week to be above normal for most areas of Upper MI. As for temps, with the progressive nature of the flow and frequent shortwave passages, no prolonged periods of well above normal or well blo normal temps will occur. Instead, expect some fluctuation in temps, but mostly around normal to above normal. Majority of days will be above normal, generally 5- 10 degrees above normal. Farther down the road, there are still indications for a cooler period mid month, probably beginning late next week, per recent EPS runs which show troffing/weak negative height anomalies over the Great Lakes region and ne U.S. There is also consistency in recent CFSv2 ensemble means showing a cooler period mid month. Don`t know much about the strengths/weaknesses of the ECMWF AI machine learning model yet, but it has had a run-to-run signal for a chilly period generally around May 15 with 850mb temps down toward -4C over Upper MI. Beginning tonight/Fri, vigorous shortwave over eastern SD this evening will reach western Lake Superior Fri morning and will be approaching Hudson Bay Fri evening. Main surge of waa/isentropic ascent and strong 850-700mb moisture transport advances across Upper MI this aftn/evening, providing the period of more widespread shra. There isn`t much cape for parcels lifted from top of sfc based inversion. Most guidance is less than 200j/kg, but a few models show spotty up to 300j/kg. Might be a few rumbles of thunder. Occluded front associated with shortwave will reach western Upper MI around 06z, will extend roughly thru Munising to Manistique by 12z Fri and will exit Luce County around 15z. Shra will abruptly end with its passage as sharp mid-level drying surges into the area. Lower levels will dry out quickly as well on Fri as daytime heating builds mixed layer and taps very dry air aloft. Expect skies to trend sunny Fri morning over the w half and early to mid aftn across the e. However, weaker wind fields over the e and resulting lake breeze development may end up allowing lower clouds to persist there thru the aftn, at least closer to the Great Lakes, especially if widespread fog develops over the Lakes with the rainfall this aftn/tonight. Expect high temps on Fri ranging thru the 60s F, even lwr 70s F portions of interior w to central. Will be locally cooler along the Great Lakes. Over the w interior, deepening mixing will support dwpts tumbling to around 30 or even upper 20s F, resulting in RH falling to 20-30pct. Fcst soundings also support gusty westerly winds to 25-30mph. Even though there will be gusty winds, warm conditions and low RH, recent rainfall, including this aftn/tonight, will work to limit fire wx concerns on Fri. Dry weather will continue Fri night. Then, next shortwave will already be approaching by Sat aftn, resulting in a chc of shra spreading w to e Sat aftn/night. Model spread is high with some models show nothing more than spotty pcpn while others are more widespread. Ensemble guidance doesn`t show much more than a 10-30pct chc of rainfall exceeding a tenth of an inch. Better chc of pcpn will be over the western fcst area as upper diffluence from right entrance of sw-ne oriented upper jet will pass across that area before weakening as it shifts e. Fcst will only reflect a 20-40pct chc of shra spreading w to e Sat into Sat evening. In the wake of the shortwave, dry weather returns for Sun with sfc high pres ridge arriving. A model trend that showed up 24hrs ago for Mon has been locked onto as models solidly agree on a more amplified mid-level ridge over the Upper Great Lakes on Mon. So dry weather will continue on Mon as well. For the time range, agreement is good for the next shortwave swinging out of the Rockies on Mon to result in a mid-level low over the Dakotas for Tue. In response, strengthening waa/isentropic ascent will spread toward Upper MI late Mon night/Tue, supporting shra spreading into the area late Mon night/Tue morning. Anchored by the mid-level low, mid-level troffing will then expand across the Rockies and Plains to Great Lakes during the midweek period, resulting in additional shortwaves tracking thru the trof to the Upper Great Lakes. Thus, expect more opportunities for shra Tue thru Thu. && .AVIATION /18Z TAFS THROUGH 18Z FRIDAY/... Issued at 129 PM EDT Thu May 2 2024 An approaching system has lowered conditions down to MVFR this afternoon in rain showers and lower clouds. Cigs will continue to lower to IFR this afternoon then to LIFR this evening or overnight, but confidence in exact timing is low. Easterly upslope flow at SAW and CMX may result in LIFR prevailing longer than IWD where flow is downsloping. Expect improvement to VFR at all terminals as a west-southwest develops in the wake of the system`s cold front moving across the area. && .MARINE... Issued at 458 AM EDT Thu May 2 2024 Winds have fallen to under 15kt across Lake Superior during the night. These lighter winds under 15kt will linger across eastern Lake Superior today. Meanwhile, over western Lake Superior, NE winds will be on the increase again as the next low pressure lifts toward the Upper Mississippi Valley. Expect NE winds up to around 25kt by late aftn over far western Lake Superior. E to SE winds will increase up to 25kt over eastern Lake Superior tonight. Probability guidance only indicates about a 10pct chc of low end gale gusts for this event. As low pres lifts into northern Ontario on Fri, winds will shift sw. While gusts up to 25kt will continue over western Lake Superior, winds will fall off to mostly under 15kt over the eastern lake in the afternoon as winds back around to the se. Over the weekend, expect winds mostly below under 20kt across Lake Superior under a relatively weak pres gradient. High pres that arrives over the Upper Great Lakes late weekend will shift e on Mon while a deep low pres emerges over the western Dakotas. This will result in increasing easterly winds Mon into Tue. Expect winds up to 30kt by Tue. With showers moving across Lake Superior this aftn and tonight, some fog will likely develop, and it could become locally dense. Fog will push mostly to Canadian waters for Fri due to the sw winds. If the fog does not clear off of the lake on Fri, it may expand back across eastern Lake Superior during Fri aftn as winds back to the e to se. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...Voss LONG TERM...Rolfson AVIATION...Voss MARINE...Rolfson