Area Forecast Discussion
Issued by NWS Marquette, MI
Issued by NWS Marquette, MI
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063 FXUS63 KMQT 031134 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 734 AM EDT Mon Jun 3 2024 .KEY MESSAGES... - Showers and a few thunderstorms progress eastward across west and central Upper MI today. Greatest coverage will be over the west. Severe storms not expected. - Frequent opportunities for showers and thunderstorms over the next 7 days, with a break on Tuesday. - Above normal temperatures through Wednesday, then turning cooler for the second half of the week. && .SHORT TERM /THROUGH THIS AFTERNOON/... Issued at 312 AM EDT Mon Jun 3 2024 Water vapor imagery and RAP analysis show weak mid-level troffing over the Northern Plains. One vort max is noted over eastern ND, but it`s difficult to pick out clearly any others. Radar imagery shows shra/tsra from MN to Nebraska/KS with greatest coverage across MN within 40-50kt low-level jet and the resulting 850mb theta-e advection that has developed in response to the aforementioned ND vort max. Radar imagery has occasionally been suggestive of potentially one or two convectively induced weak vort maxes within the shra/tsra area. The shra/tsra have spread out over nw WI, and shra have recently arrived over far western Upper MI. Temps across the fcst area currently range from the mid/upper 40s F at a few of the traditional cold spots across the e to the mid 60s F at KIWD. As shortwave over eastern ND lifts ene today, stronger core of the low-level jet will mostly pass just nw and n of Upper MI, suggesting that wider coverage of heavier rainfall will brush w and nw Upper MI this morning. Meanwhile, with the southern end of the low-level jet weakening to around 30kt at it translates over Upper MI today, would anticipate a diminishing of shra as they progress across the area, and much of the guidance indicates that. If a weak vort max is concealed in the convection in MN, that would work to delay the expected diminishing of shra. Of note is a better defined convectively induced vort max over eastern Nebraska. Models indicate that this feature will lift to Upper MI later this aftn, potentially reinvigorating shra across the central and/or eastern fcst area. Models have mixed signals on whether this feature will hold together and/or aid shra. Will be something to monitor for an increase in rainfall later aftn. Whatever the case, shra won`t reach the far eastern fcst area until late in the day. CAPE is meager today with abundant cloud cover limiting heating, but enough is present for non sfc-based parcels or potentially sfc based parcels this aftn if there is some thinning of clouds to maintain mostly just a schc thunder mention. With expectation of clouds mostly dominating, knocked high temps down a little. Expect upper 60s/lwr 70s F for the most part, though eastern areas away from Lake MI should reach the mid 70s due to thinner cloud cover thru at least the morning. && .LONG TERM /TONIGHT THROUGH SUNDAY/... Issued at 334 AM EDT Mon Jun 3 2024 As a cold front loses some steam over the eastern half of the U.P. tonight, scattered shower and thunderstorm frequency lessens as they continue to march eastward with time. With warm air advection from the Gulf immediately moving in behind the front (one of the reasons the cold front starts to die out), expect a saturated layer of air up to 4 to 5 kft to bring some patchy fog and drizzle across the U.P. behind the showers and thunderstorms of the dying front. This will keep low temperatures tonight well above normal; temperatures are projected to only get down into the mid 50s near Lake Michigan to around 60. Moving into Tuesday, expect skies to scatter out a little as the last of the showers and storms moves out of the far eastern U.P. into northern Ontario and the low-level clouds causing the drizzle/patchy fog across the rest of the area scatters out during the morning hours. CAMs have recently backed-off on precipitation chances throughout the day Tuesday in comparison to the global models. Therefore, while I`m thinking partly cloudy skies are still likely (70+% chance) to occur across the area Tuesday, rainfall chances shouldn`t enter into the U.P. again until late this afternoon over the far west at the very earliest as a second, stronger cold front approaches from the Northern Plains. With warm air advection continuing ahead of the cold front, expect the warmest temperatures of the week to occur Tuesday, with highs getting into the 80s across some of the interior areas, particularly over the west and downslope areas near Lake Superior where the increasing southerly downslope winds throughout the day could locally increase temperatures by at least a few degrees; the warmest temperatures will likely be around Ontonagon to the Porkies. In addition to the warm temperatures, Tuesday may also feel pretty muggy, with CAMs bringing dewpoints into the mid to upper 60s by the afternoon hours. Therefore, if you`ve got A.C., it may be your best friend on Tuesday. The cold front looks to begin bringing showers and thunderstorms to the western U.P. Tuesday evening. Severe weather is currently not expected with the passage of the cold front Tuesday night at this time as the showers and storms associated with it are expected to come during the overnight hours, when CAPE will be lacking in the atmosphere. In addition, bulk shear values generally look to remain well below 30 knots, which should prevent the updrafts from tilting enough for the downdrafts of the storms to kill them. However, there are some outlier models that, should they come together just right, may allow for some strong to severe convection to reach the far western U.P. Tuesday evening; this would bring some marginally severe hail and winds to the far west before the convection diminishes overnight. However, the chance of this occurring is very low (<5%). With ensemble guidance showing PWATs above the 90th percentile of climatology at around 1.5 inches, heavy rainfall seems to be the main threat Tuesday night through Wednesday. I wouldn`t be surprised if some places received over an inch of rainfall due to the showers and storms via the abundance of moisture ahead of the cold front. The cold front continues through the eastern half of the U.P. Wednesday as a secondary shortwave drops down from Canada and brings light rain showers and maybe a thunderstorm or two back across the western half of the U.P. Wednesday afternoon behind the front. Behind the cold front, expect cooler temperatures to dominate the rest of the extended forecast period as a synoptic troughing set-up settles over Canada and rotates multiple shortwaves across our region throughout the rest of this week and upcoming weekend. This will bring multiple light rain shower chances across our area for the rest of the extended period, and maybe a thunderstorm or two during the afternoon hours when daytime heating becomes maximized. In addition, I have a hunch that the dewpoints will be lower than what the NBM is currently forecasting for the latter half of the forecast period; with the cold air advection bringing dry northerly air into our region, I wouldn`t be surprised if mixing in the boundary layer is greater than what`s predicted by the medium range models. Thus, there is a chance (~25-30%) that we could see min RHs dropping down closer to 30% starting Thursday. However, my confidence in this solution remains small at this time as there is a bit of model divergence as to when exactly the shortwaves will impact our area as model diffluence has increased between the different medium range models on the shape of the upper-level synoptic pattern. With the inclusion of rain showers increasing dewpoints at the sfc throughout the latter half of the forecast period from time-to-time, I decided to leave the dewpoints alone for now. ECMWF EFI is also hinting at some windier conditions come Thursday and Friday as the EFI values of 0.5 to 0.7 are expected those two days. This may help to enhance drying at the surface and increase wildfire spread (should any occur). The winds for Thursday and Friday may need to monitored in future forecast packages given the increased fire weather impacts they could have should the gustier winds materialize. && .AVIATION /12Z TAFS THROUGH 12Z TUESDAY/... Issued at 734 AM EDT Mon Jun 3 2024 Disturbance is spreading shra thru western Upper MI attm. These shra will continue eastward this morning with expectation of a diminishing trend. Aftn and early evening may feature new shra development thru mainly central Upper MI. At IWD, ongoing shra should end 13-14z. Then, additional shra may develop at times thru mid to late aftn. Confidence is low so only VCSH was included in fcst. MVFR cigs developing this morning at IWD may hang around thru the day. Some clearing to VFR this evening will be followed by potential fog overnight. While fcst reflects MVFR, IFR or even LIFR not out of the question. Ongoing LLWS at IWD will end by late morning. At CMX, expect shra until around 15z. While cloud bases will remain above 3000ft, vis should fall to MVFR. Additional shra may develop thru mid aftn. Expect IFR to LIFR to develop at CMX tonight under light upslope ese flow off of Lake Superior. Ongoing LLWS will end by late morning. At SAW, a period of shra will occur late morning, but conditions should remain VFR. Additional shra development is expected during the aftn/evening. If any of those shra pass across SAW, MVFR will be possible. Expect IFR to possible LIFR to set in later tonight under upsloping southerly winds. && .MARINE... Issued at 334 AM EDT Mon Jun 3 2024 Southeast winds increase to 20 to 25 knots over the north-central lake and the southerly shoreline today ahead of a cold front pushing through; I wouldn`t be surprised if we had locally higher downslope winds near the tip of the Keweenaw, given that it`s a `hotspot` for stronger winds when the winds come from the southerly direction. Once the dying cold front passes through, expect the winds to slacken back down to 20 knots or less by this evening and to remain that way until a second, stronger cold front moves through Tuesday night and Wednesday, when southeast to southerly wind gusts of 20 to 25 knots will again be seen over the central lake and also probably over the southerly downslope areas along the U.P.`s shoreline (particularly the tip of the Keweenaw). Behind the cold front, we could see southwest to westerly winds pick up to around 20 knots over the west half of the lake Wednesday afternoon as a secondary shortwave moves through. However, with model divergence increasing and cold air advection decreasing for that point in time, gusts have trended slightly lower than what was predicted yesterday. As additional shortwaves rotate through our area the rest of this week through this weekend, expect winds to increase from the west and northwest at times; we could see westerly winds gust up to 20 to 30 knots Thursday and again to 20 to 25 knots from the northwest Friday as shortwave lows impact the Upper Great Lakes. As for other marine concerns this week, expect some patchy fog over the western and north central lake today behind the cold front as the moisture from the rainfall becomes trapped near the water`s surface due to the strong temperature inversion caused by the cool lake waters; the fog could be dense in some spots. This patchy fog looks to persist until the second, stronger cold front moves through Tuesday night and Wednesday, when the cooler air behind the front could allow the moisture to mix out. As for the thunderstorm chances this week, a few thunderstorms are expected to move from the far western lake early this morning to the far eastern lake by Tuesday morning. Thunderstorms return late Tuesday afternoon as the second cold front moves into the far western lake; some severe weather could be seen over the far west Tuesday afternoon and evening near Duluth, although the chance for severe weather is still rather low (~5%); severe hail and winds are the primary concerns. The thunderstorm activity continues across Lake Superior from west to east Wednesday until leaving into northern Ontario late in the day. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...Rolfson LONG TERM...TAP AVIATION...Rolfson MARINE...TAP