Area Forecast Discussion
Issued by NWS Marquette, MI
Issued by NWS Marquette, MI
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
794 FXUS63 KMQT 251944 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 344 PM EDT Sat May 25 2024 .KEY MESSAGES... - Approaching low pressure system brings isolated shower or thunderstorm chances to the far west this evening. - Approaching low pressure system brings widespread rain chances late Sunday into early Monday. Rainfall amounts >1 inch are possible by Monday evening. - Below normal temperatures for the first half of the week, followed by a drying trend midweek. Patchy frost possible Thursday morning. && .SHORT TERM /THROUGH THIS AFTERNOON/... Issued at 240 AM EDT Sat May 25 2024 Upper air pattern consists of a 500 mb closed low near Lake Winnipeg this morning which meanders slowly northwest into western Ontario by 00z Sun. There is some 850-500 mb q-vector convergence and some moisture that comes into the west late in the day while earlier moisture and q-vector convergence moves out across the cwa this morning. Showers will continue to move out this morning and then the next wave comes into the far west by late this afternoon. Appears like this next wave would be in the southern part of a deformation zone from the closed low that gives the far west a glancing blow. Could be some thunder with this elevated convection. Overall, did not make too many changes to the going forecast. && .LONG TERM /SUNDAY THROUGH SATURDAY/... Issued at 342 PM EDT Sat May 25 2024 Active pattern for Upper Michigan continues in this forecasting period. The long term pattern for Upper Michigan will start off with an anomalous surface low and shortwave lifting northeast into the Great Lakes Sunday and Monday. From there, broad mid-level troughing establishes itself across the eastern half of North America before ridging gradually builds into the region for the latter half of the week and into the weekend. Together, these will yield early week rain with cooler temperatures, followed by a dry period midweek and warming temperatures late week. After early morning rain showers pull out of the western UP, expect one more brief period of dry weather through the morning ahead of an approaching shortwave and deepening surface low ejecting out of the Plains. This tracks somewhere between northern IL and southern WI by Sunday evening, and will continue to move ENE into the Lower Peninsula Sunday night through Monday before moving north of Lake Huron and rapidly deepening by Monday evening. PWATS building to 1- 1.5 across the region coupled with increasingly strong dynamics should yield widespread rain for Upper Michigan by Sunday afternoon, persisting until the system pulls away Monday. QPF varies per model given persistent subtle differences in track, but the general thinking is widespread 0.5-1.5 inches of rain, with those most likely to see the higher amounts being the central and eastern portions of Upper Michigan. Precip should end west to east through the day Monday, but another shortwave pressing eastward across Minnesota/Wisconsin, followed by a more broad shortwave dropping southeast out of Ontario/Manitoba Monday night may support shower activity into Tuesday night. The best potential for additional rainfall during this period will be across the eastern UP, closer in proximity to the deep low to our northeast and the wraparound moisture being directed into the area. High pressure and a dry airmass builds into the region Wednesday and should maintain mostly dry conditions for the forecast area to finish at least through early Friday. As the early week surface low pulls away, a cool airmass will rotate into the region. Daytime temperatures on Tuesday/Wednesday look to be in the 50s and 60s with overnight lows in the 40s and 30s. That said, NBM 25th percentile shows temperatures dipping below 35F across much of the interior UP by Thursday morning; with light winds and a cool and very dry airmass, temperatures flirting with frost advisory criteria are a good bet. Dewpoints, too, will be something to watch during the midweek period. Dry and well-mixed soundings, particularly Wednesday, could lead to plummeting dewpoints and RH falling into the lower 30s%. A mitigating factor for the fire weather risk, in addition to fairly light winds, will be the widespread rain in the preceding days. Ridge axis builds into the region Thursday night while another trough presses out of the Rockies. Current thinking is for surface high to maintain its spot over the region until the eastward progressing trough shifts into the region. This could allow PoPs to creep into the western UP as early as Friday. && .AVIATION /18Z TAFS THROUGH 18Z SUNDAY/... Issued at 146 PM EDT Sat May 25 2024 VFR cigs/vsby are expected to prevail at each terminal through this TAF period, but showers and embedded thunderstorms are expected to impact IWD/CMX this evening. Gusty southwest winds up to 25 kts continue at IWD and up to 35 kts at CMX until wind profiles weaken and surface heating subsides late this afternoon. Confidence in thunder occuring is in the 50-75% range, justifying inclusion in TAFs even though storms may not track directly over each terminal. TAFs reflect the most likely outcome, which is a brief ~2-3 hour period of shra/-tsra followed by a 12-15 hour dry period toward the end of the TAF period. However, a weak frontal boundary lingering nearby may be sufficient to trigger light rain showers throughout Sunday morning at CMX/IWD. Showers are increasingly likely late in the TAF period as a low pressure system lifts north toward Upper Michigan with a period of light to moderate rain expected at all terminals late on Sunday. SAW stays dry with VFR cigs/vsby through tonight, but deteriorating cigs/vsbys are expected near or shortly after the end of this TAF period. && .MARINE... Issued at 342 PM EDT Sat May 25 2024 Low pressure over the Ontario/Manitoba border continues to track northward this afternoon while weakening. Winds remain elevated across western Lake Superior, coming in out of the SW and continuing to gust to around 20-25kts through the early evening while to the east, SE winds are coming in at around 10 knots. Winds across the western half of the lake fall below 20 knots later this evening. A slight chance of thunderstorms exists on and off throughout tonight in the southern part of western Lake Superior, including the Keweenaw, and lingering mid-lake into Sunday morning. By early Sunday morning, weak high pressure building into the region results in light southerly flow of less than 5-15 kt, backing to the E/SE by mid-morning ahead of an approaching low over the Plains. Waves fall to around 1-3ft. By early Sunday evening, winds are forecasted to be easterly across Lake Superior at 10-15 kt. Winds continue to back and build throughout Sunday night as the Colorado low approaches, reaching northerly by Monday morning at 15-20 kt and waves building to 3-5 ft. A slight chance of thunderstorms exists on eastern Lake Superior very early Monday morning. Backing continues until Monday night, when steady northwesterly flow becomes established at 10-20 kt, being higher potentially up to 25kts in eastern Lake Superior. This northwesterly flow and wave heights of 3-5 ft are expected to remain steady until Wednesday midday when high pressure begins to build into the area. At this time, expect light and variable winds and decreasing waves until Thursday midday, when light southerly flow at 5-15 kt re-establishes itself, along with waves 1-3 ft, for the remainder of the forecast period. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...07 LONG TERM...LC AVIATION...EK MARINE...LC