Area Forecast Discussion
Issued by NWS Marquette, MI
Issued by NWS Marquette, MI
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970 FXUS63 KMQT 050504 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 104 AM EDT Wed Jun 5 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. -Showery weather through at least this weekend with a trend toward much cooler temperatures as a closed low sets up shop over the Great Lakes. && .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 /THURSDAY THROUGH TUESDAY/... Issued at 447 PM EDT Tue Jun 4 2024 Models and ensembles trending toward a blocky pattern in the high latitudes of North America from the middle of this week into at least the early part of next week. Models indicate mid-level ridging/positive height anomalies, first from ne Canada across the Arctic Ocean, and then over western N America will force mid- level troughing 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 through 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 troughing will support showers/t-storms late tonight/Wed as the lead cold front passes across the area. Models advertise a mid-level low closing off over the Great Lakes region by Thu, leading to showery weather. Generally, the pattern of mid-level troughing or a mid-level low near the area through at least the first half of next week will support frequent opportunities of showers. Model details will be muddied on the timing/track of shortwave impulses circulating around mid-level low into Upper MI, so pcpn fcst will have much more uncertainty than normal. At this time, 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 showers are likely to be scattered in coverage on most days. Beginning Wednesday, a vigorous shortwave now moving out across the Northern Plains today will take on a negative tilt as it swings into the western Great Lakes Wed morning. With the arrival of the negative tilt shortwave there will be uptick in forcing/upper diffluence along the associated cold front as it moves w-e across the area. Precipitable water increasing to around 200pct of normal will support locally heavy downpours. HREF 90th percentile has streaks of 1.5 inch or higher pcpn amounts, indicating the heavier rainfall potential with some of the convection. Elevated cape of several hundred j/kg along and ahead of the cold front will also support isolated t-storms. In the wake of the fropa showers/t-storms 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 afternoon/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 fcst soundings showing potentially several hundred j/kg of MLCAPE building, deep layer shear 25-35kt, and a drier profile blo cloud layer, there is a potential for gusty wind producing storms late Wed aftn/evening across the west half of Upper MI. While winds probably won`t reach severe criteria, it will definitely be something to monitor late Wed afternoon, especially if instability ends up on the higher end of current guidance which would raise the potential of isolated severe wind gusts. Showers/t-storms will spread into the eastern fcst area during Wed evening with the gusty wind risk diminishing as instability wanes. 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 shower 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, showers will take on a diurnal component and expand in coverage away from the stabilizing influence of Lake Superior under nw winds. Would expect s central and se Upper MI to see most numerous shower coverage. 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 showers/clouds are more widespread than currently expected, highs will be lower. Showers should diminish Thu night with the loss of diurnal instability. Friday into Saturday will likely be very similar to Thursday, but with the mid-level low shifting slightly e, though diurnal shower coverage will likely decrease a bit each day from Thursday`s coverage. As with Thursday, if clouds/shower coverage are more widespread, highs Fri and Sat will be lower than the current forecast of upper 50s to mid 60s F. Over the late 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 shower potential and the ensembles also support this by indicating persistent mid-level troughing into early next week. Similar to the previous days, if showers and clouds are more widespread or persistent on Sunday, high temps will only be in the 50s across the w and n and 60s s central. Overall, it appears the influence of the mid-level low should diminish during the early part of next week, so would expect showers to become more isolated at that time. && .AVIATION /06Z TAFS THROUGH 06Z THURSDAY/... Issued at 104 AM EDT Wed Jun 5 2024 Overnight, SAW and CMX will remain VFR and dry and CMX will have some LLWS. A cold front will move 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 will fall to IFR by late tonight before going back to VFR Wed morning. SAW and CMX will fall to IFR by Wed morning and then go to VFR Wed afternoon. && .MARINE... Issued at 447 PM EDT Tue Jun 4 2024 Other than some 20-25 kt ne wind gusts over western Lake Superior and se winds over eastern Lake Superior, winds tonight will generally be less than 20 kts. Thunderstorms moving out over western Lake Superior this evening ahead of an approaching trough will pose a risk of strong wind gusts. This trough will then sweep across Lake Superior late this evening thru early Wed aftn with more storms possible. While wind 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 trough. More thunderstorms developing over MN and moving out across western Lake Superior Wed afternoon/evening 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 die down slightly by Sat. Also of note, fog will be dense at times on western and central Lake Superior into this evening. This fog should depart with passage of the trough late this evening through early Wed afternoon. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...GS LONG TERM...Voss AVIATION...07 MARINE...Voss