Area Forecast Discussion
Issued by NWS Marquette, MI
Issued by NWS Marquette, MI
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658 FXUS63 KMQT 041853 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 253 PM EDT Tue Jun 4 2024 .KEY MESSAGES... -A few strong to severe thunderstorms expected in the far western UP today. Not much severe weather is expected, but a few isolated damaging wind gusts and/or marginally severe hail cannot be ruled out (10%). -Cold front spreads from west to east across the UP tonight and tomorrow morning, bringing some thunder and occasional downpours but otherwise no severe weather. -Frequent showers over the next 7 days, but particularly through the weekend. Thunderstorms with strong, gusty winds possible late Wednesday afternoon and evening over western Upper MI. -Above normal temperatures through Wednesday, then turning cooler with an extended period of below normal temperatures through at least the first half of next week. && .SHORT TERM /THROUGH WEDNESDAY NIGHT/... Issued at 250 PM EDT Tue Jun 4 2024 GOES-16 Day Cloud Phase RGB imagery shows a mixture of cloud forms over Upper Michigan and Lake Superior this afternoon. Patches of dense fog are over much of the open waters of Lake Superior with some other lower stratus advecting north. Meanwhile, stratus is breaking into stratocu over the central and eastern areas of Upper Michigan while Gogebic and Ontonagon are starting to see some cu fields bubbling up. This latter area will be the area of most impactful weather this afternoon as CAMs resolve a few strong thunderstorms over the far west later on this afternoon, though some differ in strength. With WAA under warm, southerly flow, temperatures have climbed well into the 70s across the UP with a few spots already in the 80s, especially in areas with downsloping in the far east and far west where clearing was seen earlier than in the central. With all of this surface warming, lapse rates at the low and mid levels have resulted in significant gains in instability. RAP mesoanalysis shows up to 2500 J/kg of SBCAPE along the MI/WI state line at 18Z with some SBCIN present, but less than 25 J/kg. The wind shear is a different story however, with effective bulk shear values less than 20 knots except for after 22Z in the far west. Hodographs are curved, but the magnitude is quite small. Despite this, the 12Z members HREF has been more aggressive than the 00Z counterparts with convective initiation this afternoon in the west, with paintball plots of 40+ dBZ simulated reflectivity showing a smattering of cellular convection over the western third of the UP from 21Z to 03Z. At this time, leaning towards a scattered to isolated cellular convective mode, with a few "core dumps" that may produce an isolated severe wind gust or marginally severe hail, but probabilities only around 10%. By around 06Z tonight, a cold front will arrive from the west and spread a line of showers and weakening thunderstorms from west to east through the west half of the UP through 12Z. No severe weather is expected from the cold frontal line of showers, but some locally heavy downpours are possible as mean NBM precipitation from 06Z-12Z is over a half inch over the far west, with high-end (top 10% of solutions) estimates of over an inch. This is still less than the flash flood guidance, so widespread flash flooding is not a threat with this system. This will begin to veer the winds westerly and bring some temperature falls to the west, but the eastern two thirds of the UP will only see lows in the low 60s to upper 50s. && .LONG TERM /TONIGHT THROUGH MONDAY/... Issued at 530 AM EDT Tue Jun 4 2024 Over the last few days, there have been some changes in how the models depict the flow evolution over and around N America. However, one aspect hasn`t changed, a lot of high latitude blockiness. Through this week and into the weekend, building mid-level ridging/positive height anomalies, first from ne Canada 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 western ridging deamplifies next week, but the EPS is slower to deamplify that ridge and is less progressive with it than the GEFS/GEPS. The positive height anomalies will remain across the Arctic Ocean thru ne Canada/Labrador Sea next week. For Upper MI, this pattern will lead to above normal temps thru Wed trending down to an extended period of blo normal temps (seasonably cool) most days thru next week. However, the large scale pattern does suggest the potential of unseasonably cool days in the mix, particularly Thu thru the weekend. Would not be surprised to see a day or two with highs widespread in the 50s F w and n. The less progressive EPS solution would allow the cool weather to persist longer thru next week than the GEFS/GEPS. As for pcpn, the development of the mid- level troffing will support shra/tsra tonight/Wed as lead cold front passes across the area. Mid-level low closing off over the Great Lakes region suggests showery weather on Thu. Generally, the pattern of mid-level troffing or a mid-level low near the area thru at least the first half of next week suggests frequent opportunities of shra. Models are quite varied on the details of the flow affecting Upper MI, so pcpn fcst will have much more uncertainty than normal. Attm, widespread, all day rains appear unlikely unless a well organized wave develops within this pattern. Many areas will be dry much of the time as shra are likely to be sct in coverage on most days. Beginning tonight/Wed, isold/sct convection should be ongoing across western Upper MI this evening from lingering daytime instability within pool of elevated theta-e. Otherwise, vigorous shortwave moving out across the Northern Plains today will take on a negative tilt as it swings into the western Great Lakes Wed morning. CAMS are in quite good agreement that strong convection developing across MN today will weaken in intensity while approaching western Upper MI mid to late evening due to a combination of diminishing sfc based instability, a notable decrease in low-level convergence, and the start of the advection of decreasing theta-e at 850mb. At this point, not expecting svr storms tonight given the currently good model agreement on the weakening trend of the storms approaching from MN/nw WI. If any stronger storms do occur, it would be early this evening with the isold/sct storms from late aftn still taking advantage of late day instability. Although tsra intensity wanes, models are in general agreement that shra/some tsra will become increasingly organized again late in the night thru Wed morning/early aftn as cold front sweeps across the area in association with negative tilt shortwave and uptick in forcing/upper diffluence. Precipitable water increasing to around 200pct of normal will support locally hvy downpours. HREF 90th percentile has streaks of 1-1.5 inch pcpn amounts, indicating the heavier pcpn potential with some of the convection. As fropa occurs, shra/tsra will abruptly end, followed by clearing from w to e early Wed morning thru early to mid aftn on Wed. Attention then turns to secondary cold front arriving late Wed aftn/evening in association with another shortwave. Aloft, height falls continue thru the day with Upper MI becoming situated under expanding mid-level low and cooling mid-levels. With potentially several hundred j/kg of MLCAPE building, deep layer shear 25-30kt (some models even higher), and fcst soundings showing an inverted profile blo cloud layer, gusty wind producing storms seem like a good bet late Wed aftn/evening across the west half of Upper MI. Winds probably not svr strength, but it will definitely be something to monitor late Wed aftn, especially if instability ends up on the higher end of current guidance which would raise potential of isold svr wind gusts. Shra/tsra will spread into the eastern fcst area during Wed evening with gusty wind risk diminishing. On Thu, Upper MI will be situated firmly under mid-level low circulation with recent guidance now showing the center over or very near to Upper MI. Some -shra activity will be ongoing to start the day. Under cold pool aloft combined with any shortwaves swinging around the circulation and the building of weak sfc based instability, shra will take on a diurnal component and expand in coverage away from stabilizing influence of Lake Superior under nw winds. Would expect s central Upper MI to see most nmrs shra. Will be a cooler day with highs in the 50s near Lake Superior for areas where nw winds are directly onshore ranging up to the mid/upper 60s F s central. If shra/clouds are more widespread than currently expected, highs will be lower. Shra will diminish Thu night. Fri will be a near repeat performance of Thu, but with mid-level low shifting e some, diurnal shra coverage will likely be less than on Thu. As with Thu, if clouds/shra are more widespread, highs Fri will be lower than the current fcst of upper 50s to mid 60s F. Over the weekend thru early next week, details of the structure of the mid-level flow from s central Canada thru the Great Lakes region is very uncertain. Models have shown little agreement or run-to-run consistency on the expansiveness, location, movement of mid-level low and shortwave timing/amplitude in the flow. Pattern is certainly suggestive of daily shra potential. Similar to the previous days, if shra and clouds are widespread Sat or Sun, high temps will only be in the 50s across the w and n and 60s s central. It appears influence of the mid-level low will diminish during the early part of next week, so shra potential will decrease at that time. && .AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/... Issued at 134 PM EDT Tue Jun 4 2024 CMX and IWD have recovered to VFR already while SAW is still dealing with MVFR skies for another couple hours. This afternoon, SAW and CMX will remain VFR and dry, though some convection is expected in the western UP, including in the vicinity of IWD. Overnight, a cold front will spread west to east across the TAF sites, and the showers and thunderstorms from that front will usher in lower ceilings and potentially low visibility. IWD and CMX are about 40% likely to fall to IFR in the early to midmorning hours while SAW is over 50% likely to fall to IFR with 25% chance of LIFR by 13Z. Behind the front, gradual improvement in flight categories is expected, with VFR expected at IWD by 14Z, CMX by 17Z, and SAW sometime after this TAF period. && .MARINE... Issued at 530 AM EDT Tue Jun 4 2024 A period of lighter winds, mostly under 15kt, is expected this morning on Lake Superior. Approaching low pres trof will then lead to increasing winds this aftn/evening. Some gusts into 20-25kt range will be possible with the ne winds over western Lake Superior and se winds over eastern Lake Superior. Thunderstorms moving out over western Lake Superior this evening will pose a risk of strong wind gusts. The trof will sweep across Lake Superior late this evening thru early Wed aftn. While winds gusts to around 20kt will continue, the showers and thunderstorms along/ahead of the front may result in locally enhanced winds ahead of and just behind the trof. More thunderstorms developing over MN and moving out across western Lake Superior Wed aftn will also pose a risk of locally strong wind gusts. Thereafter from Wed night thru Fri, fairly steady w to nw winds of mostly 20-25kt are anticipated with occasional gusts to 30kt. Winds may settle back just a bit for Sat. Also of note, fog will be dense at times on Lake Superior today into this evening, especially across the w half. This fog should depart with passage of the trof late this evening thru early Wed aftn. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... Dense Fog Advisory until 11 PM EDT /10 PM CDT/ this evening for LSZ162-263-264. Dense Fog Advisory until 5 PM EDT this afternoon for LSZ245>247-265>267. Lake Michigan... None. && $$ SHORT TERM...GS LONG TERM...Rolfson AVIATION...GS MARINE...Rolfson