Area Forecast Discussion
Issued by NWS Marquette, MI
Issued by NWS Marquette, MI
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879 FXUS63 KMQT 051924 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 324 PM EDT Wed Jun 5 2024 .KEY MESSAGES... - Some high-base showers and thunderstorms look to develop over the western half of the U.P. this evening. A strong thunderstorm or two with gusty winds and hail is possible. - Showery weather and much cooler conditions expected Thursday through the weekend under the influence of low pressure. && .SHORT TERM /THROUGH THURSDAY NIGHT/... Issued at 323 PM EDT Wed Jun 5 2024 GOES-16 Visible imagery shows clearing skies along the MI/WI state line behind an advancing cold front, with the band of rain showers from that front now mainly confined to the eastern half of the UP. Through 1830Z, the only electrically active storm has been a sub- severe cell that started in southern Menominee County and has transited the Bay of Green Bay and is imminently arriving at the Garden Peninsula. Under cloudy skies for much of the day, highs are around 10 degrees cooler than yesterday, mainly in the low 70s. Attention turns upstream this evening to the clearing in the west, which already is showing signs of some cu development supported by diurnal heating and a secondary shortwave evident on RAP Analysis 500mb heights. The 12Z HREF showed much less available instability relative to yesterday`s storms with only around 500-1000 J/kg of SBCAPE available. Shear is right around what it was yesterday with around 20 kt of effective bulk shear and 50-100 0-3km SRH. It is worth noting that while instability is surface-based, the depth of the mixed layer at the surface is around 6,000 ft, so cloud bases are going to be relatively high. Reflectivity paintball plots in the HREF show that CI will begin in northern Wisconsin and push east into the UP around 20Z, somewhat losing energy as it progresses and maintaining cellular form. Thinking hazards are once again isolated damaging wind gusts and pea to quarter sized hail from "core dumps". Less total precipitation is expected with this round of showers, with HREF mean 6-hourly precipitation only around 0.2-0.4 inches. In the wake of showers, lows look to fall to the 50s tonight, with winds staying out of the west. && .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 /18Z TAFS THROUGH 18Z THURSDAY/... Issued at 134 PM EDT Wed Jun 5 2024 VFR prevails at all TAF sites to begin this afternoon. -SHRA has moved out of IWD and CMX with SAW forecast to also clear out of precip in the next hour or two. This evening, a second wave of showers is expected to move in from the west, with some stronger TSRA possible at IWD. VFR is expected to prevail through these SHRA/TSRA. In the morning hours, low (20-40%) SHRA chances return to the forecast along with likely (50+%) reductions in ceiling height to MVFR, though models have trended later with the onset of MVFR conditions over the last few model cycles. Expect winds to remain primarily out of the west, occasionally gusty. && .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...GS LONG TERM...Rolfson AVIATION...GS MARINE...Rolfson