Area Forecast Discussion
Issued by NWS Marquette, MI
Issued by NWS Marquette, MI
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940 FXUS63 KMQT 051058 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 658 AM EDT Wed Jun 5 2024 .KEY MESSAGES... - A cold front moves through the U.P. today. Expect some occasional downpours from the associated showers and thunderstorms. No flash flooding is expected. - Some high-based showers and thunderstorms look to develop over the western half of the U.P. late this afternoon. A strong thunderstorm or two with gusty winds and hail is possible. - Gusty wind producing showers and thunderstorms this evening west half. - Showery weather and much cooler conditions Thursday through the weekend under the influence of low pressure. && .SHORT TERM /THROUGH THIS AFTERNOON/... Issued at 220 AM EDT Wed Jun 5 2024 A strong cold front is beginning to make its way into the far west early this morning, bringing showers and thunderstorms along and ahead of the frontal boundary across our area. With limited CAPE relegated to the mid levels of the atmosphere and weak shearing, no severe weather is expected this morning through early this afternoon in association with the cold front. That being said, with the RAP reanalysis on the SPC mesoanalysis page showing PWATs around 1.50 inches moving into the U.P. (which is above the 90th percentile of modeled climatology), heavy rainfall is a threat within the stronger convective cells as the cold front crawls its way eastwards today. With WFO Duluth already having Local Storm Reports in the 1 to 3 inch range already, I wouldn`t be surprised if quite a few spots across the U.P. got an inch or more of rainfall today, even as the convection continues to weaken with time. That being said, with drier conditions to moderate drought conditions in the far west still remaining over the U.P. ahead of showers and thunderstorms, no flash flooding is expected at this time. That being said, the plants will certainly enjoy the rainfall, and hopefully it will relieve the last of the drought conditions over the far west. Behind the cold front, expect skies to clear out as cooler and much drier air moves into the western half of the U.P. this afternoon. As a secondary shortwave moves towards the Upper Great Lakes this afternoon, expect its cold front to move into the western U.P. by the mid to late afternoon hours. The forcing along the front appears strong enough to create some high-base showers and thunderstorms over the western U.P. late today. With strong lapse rates in the lower levels of the atmosphere, skinny but surface-based CAPE up to 500 J/kg, and plenty of dry air in the upper levels of the atmosphere, we could see a strong elevated thunderstorm or two develop late this afternoon over the western half of the U.P.. While rainfall amounts from these showers and storms look to be fairly light (around 0.10 inch of liquid or possibly less) given the strong dewpoint depressions near the surface before convective initiation, they may produce some gusty winds and hail at times. These showers and storms head towards the eastern half of the U.P. as we head into the evening hours. && .LONG TERM /TONIGHT THROUGH TUESDAY/... Issued at 515 AM EDT Wed Jun 5 2024 Flow over and around N America thru early next week will feature pronounced high latitude blockiness. Through the remainder of this week and into the weekend, building mid-level ridging/positive height anomalies, first from ne thru n central Canada and across the Arctic Ocean, and then over western N America will force troffing to develop from s central Canada across the Great Lakes/eastern U.S. The last 24hrs of medium range model guidance has trended toward the western ridge deamplifying/progressing downstream a little quicker next week, resulting in quicker weakening/eastward progression of the troffing affecting the Great Lakes. For Upper MI, this pattern evolution will lead to a period of blo normal temps (seasonably cool) thru early next week. However, the large scale pattern does suggest the potential of unseasonably cool days in the mix, particularly on Thu. The aforementioned model trends for next week suggest a little more aggressive warming that would bring temps back to around normal early in the week and then above normal late week. Farther down the road, the end of the ensemble guidance and the 00z June 4 ECMWF weeklies suggest we`re probably heading toward an overall warm last half of June as heights build across the central and eastern U.S. The CFSv2 counters that idea to some degree with coolness lingering a little longer thru mid month. As for pcpn over the next 7 days, the development of the mid-level troffing from s central Canada thru the Great Lakes region will support showery weather at times Thu thru the weekend. Models have lacked run-to-run consistency and have been and continue to be quite varied on the details of the flow affecting Upper MI. So, pcpn fcst has much more uncertainty than normal. Overall, expect many areas to be dry much of the time as shra are likely to be sct in coverage on most days. Thu is likely to be the day with the most nmrs shra. With mid-level trof weakening and drifting e early next week, dry weather is more likely to prevail. Beginning tonight, secondary cold front will sweep across the area in association with another shortwave quickly following today`s wave. Shra/tsra arriving over the w late aftn will continue eastward thru the evening with the risk of strong/gusty winds diminishing with loss of daytime heating and stabilization. Overnight, broadening mid-level low centered nw of Lake Superior will increase its influence over Upper MI. Within the circulation, another shortwave will approach from northern MN. As a result, some shra will linger thru the night. On Thu, Upper MI will be situated firmly under mid-level low circulation with center over or very near to Upper MI. Shortwave tracking se from ne MN combined with the start of daytime heating will support a rapid development/expansion of shra during the morning. The shra should diminish in coverage over the w in the aftn in the wake of the wave. Considerable cloud cover will limit daytime heating/instability, so thunder potential is overall minimal. Fcst will only include a mention of thunder over the e and se fcst area due to a little more instability potential before clouding over and development of widespread shra. Under considerable cloudiness, passing shra, rather stiff wnw winds and 850mb thermal trof driving se into the area, it will be unseasonably cool for much of the area. Highs in the 50s F will likely be the rule across the w thru n central ranging up to the low/mid 60s F s central/se. Lakeside locations exposed to wnw winds across Lake Superior may not see max temps above 50F. W side of the Keweenaw likely to be coolest. Showers will diminish Thu night in the wake of shortwave, but won`t end, particularly over the e where there is actually some isentropic ascent as warmer air to the n and ne weakly advects toward the thermal troffing over the area. On Fri, center of mid-level low drifts e toward southern Ontario. Weak shortwave ridging develops into western Upper MI btwn that low and another mid-level low over s central Canada. This is suggestive of fewer shra over western Upper MI on Fri compared to Thu, more areas likely to be dry thru the day. To the e, closer to the mid- level low, there will be a greater chc of shra. High temps on Fri will be coolest over the e where more clouds/shra are expected. Mid 50s to around 60F expected there. Low/mid 60s expected to the w, except closer to Lake Superior where temps will be in the 50s. Over the weekend, the lack of run-to-run consistency and model disagreement on the details of the flow from s central Canada thru the Great Lakes region leads to decreasing confidence in pcpn chc/coverage, and that plays a role in temps as well. As a result, fcst is generally broad brushed with 30-50pct chc of shra, targeting the aftn hrs when a little instability will aid shra development. Expect high temps in the 50s near Lake Superior in areas exposed to nw winds across the lake and 60s F inland. With medium range models trending toward troffing easing and shifting e early next week, expect a trend to dry weather across the board. For the moment, there`s not really any support for including a specific shra chc Mon or Tue. There`s some indication of a shortwave trof to affect the Upper Lakes on Wed, and that would offer the next mention of chc shra. Temps will head back to around normal. && .AVIATION /06Z TAFS THROUGH 06Z THURSDAY/... Issued at 658 AM EDT Wed Jun 5 2024 A cold front bringing showers and thunderstorms across the area continues east throughout the rest of the day as conditions at KCMX and KSAW quickly drop down to IFR this morning, possibly dropping down to LIFR for an hour or two late this morning (I`d give it about a 60 to 70% chance for it to occur before returning to IFR conditions fairly quickly; it will be dependent on heavier rainfall rates). Meanwhile, KIWD should progressively improve to VFR this morning, with the other TAF sites joining in on the improving conditions by early to mid afternoon. VFR conditions continue through this evening as high base showers and thunderstorms form in the western U.P. late this afternoon and travel eastward through this evening. Some gusty and erratic winds, as well as some hail, could be seen with these high base showers and thunderstorms late this afternoon and evening across the area. We could see cigs deteriorate down to MVFR Thursday morning as another low pressure approaches. && .MARINE... Issued at 515 AM EDT Wed Jun 5 2024 Low pres trof currently over western Lake Superior will continue eastward, exiting the eastern lake mid to late aftn. While wind gusts to around 20kt are expected today, showers and thunderstorms along/ahead of the trof may result in locally enhanced winds just ahead of and just behind the trof. A secondary trof will lead to more thunderstorms developing over MN and moving out across western Lake Superior this aftn/evening, posing a risk of locally strong wind gusts. During tonight and Thu, steady w to wnw winds generally at around 20kt with occasional gusts to 30kt will set in from w to e. These winds will remain unchanged thru Fri. A slight diminishing of winds will occur over the weekend with sustained speeds falling back to around 15kt. Also of note, there will likely be some fog present thru this evening, mainly across the e half of Lake Superior. Passage of second trof should clear the fog off of the lake during tonight. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...TAP LONG TERM...Rolfson AVIATION...TAP MARINE...Rolfson