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
989 FXUS63 KMQT 250922 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 522 AM EDT Sat May 25 2024 .KEY MESSAGES... - Showers, with some thunder move out today followed by clearing skies. - Approaching low pressure system brings isolated showers far west Saturday evening then 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 into the weekend. 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 /TONIGHT THROUGH FRIDAY/... Issued at 521 AM 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, a few cooler days, and then warmer and dry to take us into the weekend. Forecast period starts off tonight, with the main focus being a deepening surface low and shortwave lifting northeast into the Great Lakes. With the system being over the Central Plains tonight, a weak associated frontal boundary will stall out over western Lake Superior, allowing warm air advection to ride a low level jet into the region. This may support some rain showers and modest weak elevated CAPE may support some thunderstorms across the west half of Upper Michigan and central/western Lake Superior. Otherwise, a mild night is expected with lows near 50F. The aforementioned surface low/shortwave will build into the region through the day Sunday and stick around Monday. 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, 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. High pressure and a dry airmass builds into the region Wednesday and should maintain mostly dry conditions for the forecast area to finish off the week. 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. Recent NBM run suggests around 20% of temps falling below 35F in the interior by Thursday morning. I suspect this probability to be a little low given deterministic solutions suggesting PWATS could be below 0.2 inches, coupled with the light winds and cooler airmass. 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. Earliest potential for this appears to be late Friday in the west. && .AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 111 AM EDT Sat May 25 2024 Occluded front is currently moving across Upper MI, and shra will end with its passage. With front already passed IWD, expect VFR to prevail at that terminal thru the fcst period. Gusty winds to around 20kt will occur overnight and to around 25kt today. Shra and potentially some tsra will develop this evening over western Lake Superior. IWD may be affected, but confidence is low attm. At CMX, front will pass in the next hr or two, bringing a wind shift from easterly to gusty westerly to 25-30kt. LLWS will also end with fropa. MVFR cigs may linger to mid morning under the upslope westerly winds at CMX, but VFR will prevail thereafter. CMX has a better chc of being affected by shra and possible tsra this evening. Included shra mention, but no thunder given the lower confidence of thunder impacting the terminal. At SAW, with the shra that have occurred, upslope sse wind should result in IFR cigs setting in over the next hr or so. Improvement to VFR will occur within 2 hrs after fropa. VFR will then continue thru the end of the fcst period. Westerly winds will be gusty to around 20kt at SAW today. && .MARINE... Issued at 521 AM EDT Sat May 25 2024 As the low pressure system currently in southern Ontario lifts north and weakens, converging southerly flow will back throughout the day Saturday and weaken. In eastern Lake Superior, winds decrease from 20 kt, gusting 25-30 kt, early this morning to 5-10 kt by mid- morning, to less than 5 kt by early Saturday afternoon. Winds in western Lake Superior remain higher for somewhat longer, diminishing from 20 kt, gusting 25-30 kt, early this morning to 5-10 kt by Saturday evening. Waves throughout this time will diminish from 6-9 ft across Lake Superior to 3-5 ft by Saturday evening. A slight chance of thunderstorms exists on and off throughout Saturday night 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, veering slightly until Sunday morning. Waves continue to decrease to 1-3 ft by Sunday midnight. Ahead of the low currently in the lower Plains, winds throughout Sunday will back and strengthen beginning mid- morning. 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 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 5-10 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...JTP AVIATION...Rolfson MARINE...RE