Area Forecast Discussion
Issued by NWS Marquette, MI
Issued by NWS Marquette, MI
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651 FXUS63 KMQT 180729 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 329 AM EDT Sat May 18 2024 .KEY MESSAGES... -Breezy south winds and very warm temps in the 70s and 80s today ahead of a cold front that will bring scattered afternoon/evening thunderstorms. The strongest storms may contain small hail. -Borderline elevated fire weather expected this weekend with breezy conditions today then very dry with light winds on Sunday. -More rain chances early to middle of next week as a series of disturbances moves across the area in a developing warm and moist southerly flow. && .SHORT TERM /THROUGH TONIGHT/... Issued at 346 PM EDT Fri May 17 2024 Water vapor imagery and RAP analysis show that the shortwave trof that brought shra to the area yesterday thru last evening has lifted across northern Ontario. In the wake of that wave, westerly flow prevails into Upper MI. An area of sct -shra has been moving out across western Lake Superior to the Keweenaw in an area of waa/isentropic ascent. The -shra that have reached the Keweenaw are really not much more than sprinkles. Elsewhere, skies cleared out quickly in the morning, but daytime heating led to a blossoming of cu. Stabilizing marine layer off of Lake MI and Lake Superior are evident, preventing cu. Temps have risen into the low/mid 70s F in the interior. Closer to the Lakes, temps range down into the 50s with some 40s F at lakeside locations along Lake Superior. Aforementioned waa/isentropic ascent will continue to support some -shra/sprinkles across the Keweenaw over the next few hrs. MLCAPE has increased to 100-200j/kg into far western Upper MI. This limited instability may support development of a few shra/tsra late aftn/early evening, less than 25pct chc. During the night, vigorous shortwave that is now over nw MT will swing out to ND. While the main low-level jet in response to this wave will develop ne thru MN during the night, there will be a modest increase in 850mb winds further ne across western Lake Superior this evening. The resulting increase in waa/isentropic ascent should yield some shra/tsra later this evening across northern portions of western Lake Superior and possibly also nw Upper MI, mainly the Keweenaw where fcst reflects 30pct chc. Shra/tsra associated with the main 40-50kt low-level jet developing across MN would reach western Lake Superior late tonight. Expect min temps tonight ranging from the lower 40s on the east side of the Keweenaw and near Lake MI to 55-60F in the southerly wind downslope areas far w (Ontonagon/Gogebic counties). && .LONG TERM /SUNDAY THROUGH FRIDAY/... Issued at 325 AM EDT Sat May 18 2024 After a continued warm and very dry day on Sunday, the focus then shifts to a couple of widespread rain events for early/mid next week before a transition to a period of below normal temperatures by late week. Beginning Sunday, surface ridging and its associated much drier air mass will take hold in the wake of tonight`s frontal passage. Abundant sunshine and light winds will result in deep mixing into extremely dry mid-levels during the day. For example, the 18z NAM fcst soundings valid at 18z Sunday over several of the interior west half sites show -30C or drier dew points at nearly 800 mb or approximately 5 kft AGL. Fortunately, surface dew points won`t mix that low, but by incorporating the local mixed dew point tool I did cut back on Td values resulting in min RHs closer to 20% across the interior portions of the cwa. The good news is light winds generally 10 mph or less should ease fire wx concerns. Lake breeze activity should limit fire wx concerns along the shorelines due to cooler temps in the 60s and higher RHs. Expect max temps reaching near 80F over much of the interior west half and mid to upper 70s over the interior east half. Models advertise a mid-level trough amplifying over the western CONUS early next week. Periodic shortwaves in a warm/moist sw flow developing ahead of the western CONUS trough will bring more rounds of showers into the area early to mid next week. The first of these shortwaves moves through late Sun night into Monday bringing the initial batch of showers adn isolated t-storms for early next week. Models show this system tapping into Gulf moisture with PWATs increasing to around 1.5 inches by midday Monday. This increase in moisture along with increasing isentropic ascent should lead to widespread wetting rain across much of the cwa. Ensemble probabilities show much of the area (except maybe the tip of the Keweenaw) with a 40-60% chance of seeing 0.5 inch of rain from this system with the greatest chances south central. After a period of drier weather Monday night into Tuesday morning, the next shortwave moves through Tuesday afternoon into Wednesday spinning up a 985-990 mb sfc low which tracks over the far western portion of the fcst area late Tue night into Wed. With PWAT values again increasing to nearly 1.5 inches along with increasing isentropic ascent, PVA and upper diffluence fcst with the shortwave, expect widespread rainfall across the area. EPS probabilites again show a 40-60% chance for getting half an inch of rainfall from this system with the greatest chances southeast and west. Despite the midweek system lifting north and east of the area, models indicate wraparound moisture behind it could support lingering isolated to scattered showers for late week (Thu-Fri) as temperatures trend cooler than normal. && .AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 116 AM EDT Sat May 18 2024 VFR will prevail thru this fcst period at IWD/CMX/SAW. Pcpn associated with a cold front will move into IWD and CMX by late Sat afternoon into early Saturday evening. Gusty winds to 20+kt will then set in at all sites mid to late morning on Sat. && .MARINE... Issued at 325 AM EDT Sat May 18 2024 Stable conditions will lead to light winds of generally 20 knots or less prevailing over the lake into early next week, except for some 20-25 kt southeast gusts today over the east half ahead of an approaching cold front. Thunderstorms are possible today into tonight as the cold front marches across the lake. These storms may contain small hail, gusty and erratic winds, and frequent lightning. More thunder chances return late Sun night into Monday and then again late Tuesday into Tuesday night as a series of disturbances track northeast across the Upper Great Lakes region. Models and ensembles indicate winds will ramp up Tue night into Wed as a stronger low pressure center tracks across the western and northern portions of the lake. Ensemble probabilities show a 40-60 pct chance of gale force gusts to 35 knots late Tue night into Wed across western and northern sections of the lake. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...Rolfson LONG TERM...Voss AVIATION...07 MARINE...Voss