Area Forecast Discussion
Issued by NWS Marquette, MI
Issued by NWS Marquette, MI
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798 FXUS63 KMQT 021143 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 743 AM EDT Thu May 2 2024 .KEY MESSAGES... - 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 through the middle of next week. && .SHORT TERM /THROUGH THIS AFTERNOON/... Issued at 346 AM EDT Thu May 2 2024 Upper Michigan is between two systems tonight with 500 mb ridging resulting in mostly clear skies and efficient radiational cooling. RGB composite satellite imagery shows low clouds across the far east and mid/upper level clouds to our southwest with clear skies across most of the CWA. Light anticyclonic winds and clear skies have allowed temps to tumble well below afternoon dew point values with a handful of sites at or below 35F even all the way to the lakeshores in a few spots. Iron Mtn and the Sault have reported fog and RGB imagery suggests implies some in the Michigamme Highlands too, but observed visibilities have been greater than a mile so far. Continued nocturnal cooling may allow for increased coverage or intensity of patchy fog, but mid-level clouds are beginning to move over our coolest locations so decided to leave fog out of the forecast for now. Looking ahead through today, the primary forecast challenges are related to cloud/precip trends with latest model guidance indicating a slightly earlier arrival of both. This feeds back onto high temps that are coming in a few degrees cooler than the previous forecast and now appear warmest ~60F across the east where cloud cover should arrive latest. HREF guidance brings the first measurable precip into locations adjacent to Wisconsin between 17-19Z (1-3 PM CDT) this afternoon then to a line between Houghton, Marquette, and Escanaba between 19-21z (3-5 PM CDT). Generally tried to mimic that timing in going forecast, but rain may struggle to move over the eastern UP until tonight. && .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 /12Z TAFS THROUGH 12Z FRIDAY/... Issued at 743 AM EDT Thu May 2 2024 Except for brief instances of shallow radiation fog, VFR conditions continue at all terminals into this afternoon. An approaching system lowers cigs and results in vsby restrictions with rain showers. Cigs lower to IFR this afternoon then to LIFR this evening or overnight, but confidence in timing is low. Easterly upslope flow at SAW and CMX may result in LIFR prevailing longer than IWD where flow is downsloping. && .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...EK LONG TERM...Rolfson AVIATION...EK MARINE...Rolfson