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
223 FXUS63 KMQT 120022 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 822 PM EDT Thu Jul 11 2024 .KEY MESSAGES... - Quiet weather persists into Friday. - Isolated (~20%) showers with a few rumbles of thunder in the interior Friday. - Hot and muggy conditions this weekend with the potential for a few strong to severe thunderstorms Saturday through Monday. - Cooling and drying trend into the midweek portion of next week with the arrival of high pressure. && .UPDATE... Issued at 822 PM EDT Thu Jul 11 2024 Late afternoon/early evening showers along the lake breeze boundary in our eastern counties have fizzled in the last hour thanks to weakening low level convergence along the lake breeze boundary. Otherwise, temps have begun their daily dip after peaking in the 70s and 80s. Expecting the remainder of the evening to be filled with partly to mostly clear skies and calm conditions. && .SHORT TERM /THROUGH TONIGHT/... Issued at 151 PM EDT Thu Jul 11 2024 Surface high pressure is sprawled out over the Great Lakes, and water vapor imagery reveals dry midlevel air overhead. Visible satellite shows plenty of fair weather cumulus over the central and interior-eastern UP, though lake breezes off of Superior and Lake Michigan are also evident. This diurnal cumulus shouldn`t be considered a harbinger of showers/storms later in the day given dry, well-capped soundings. Otherwise, temperatures are already well into the 70s across most of the area, on track to peak in the upper 70s to lower 80s in the interior UP. The exception, of course, is along the lakeshores of the Great Lakes. Look for highs in the mid 70s along Lake Michigan, and in the 60s to lower 70s along Superior. Skies remain clear overnight, and with light winds, temperatures should easily be able to fall back to the dewpoint. Expect lows in the mid 50s across most of the area, and closer to 60F along the Superior shorelines of the western and north-central UP. && .LONG TERM /FRIDAY THROUGH THURSDAY/... Issued at 357 PM EDT Thu Jul 11 2024 Aloft, the path of most prominent troughs and ridges is well to the north over Canada, leaving the Upper Great Lakes in a primarily zonal pattern aloft. This will lead to the primary driver of sensible weather to be weak shortwave impulses in the zonal flow. While the forcing may be weak and ambiguous, hot and muggy conditions this weekend will allow for instability to grow, allowing for the potential for strong to severe thunderstorms over the weekend and to begin next week. High pressure then settles over the region by next Wednesday, allowing for a cooler dry period towards the middle and late week period next week. As sunny skies kick off the day on Friday, diurnal heating will allow temperatures to climb to around 80. The main question of the forecast is whether any diurnal convection might develop. Mid-level height rises during the day will provide enough subsidence to keep widespread showers from develop, but enough of the CAMs do resolve shower formation to keep slight chances (15-25%) in the forecast. As SBCAPE values do climb to 750-1000 J/kg, any isolated showers that do form will have potential for some thunder. Over the weekend, warming under low-level meridional flow will send high temps into the mid and upper 80s. The two zones where the NBM highlights probabilities of exceeding 90F are over the south-central on Sunday at 20-40 percent and in downslope areas near Lake Superior on Saturday and Sunday as high as 60-90 percent. Moisture values increase as well, with the 12Z GEFS showing coin-flip odds of PWATs exceeding 1.5 inches by late Saturday and higher chances by Sunday. Dew points are forecast to be in the mid-upper 60s Saturday with Sunday`s dew points touching 70 for at least some period of time for much of the UP, creating quite muggy conditions. These hot summertime conditions will be accompanied with westerly to west-northwesterly flow at 500mb, which will allow for some minor shortwaves to progress through the region. The combination of a summertime airmass and the flow pattern aloft combine for a climatologically favorable setup for convection over the UP. As the hot and humid temperatures set up, CAPE values climb to over 1000 J/kg on Saturday and Monday and over 2000 J/kg on Sunday (with the 90th percentile showing worst-case values of over 3000). With the southwesterly surface flow contrasting the west-northwest flow aloft, directional shear will be present, though speed shear will be somewhat lacking. Regardless, shear will be present enough to help maintain whatever thunderstorms do initiate, so if forcing is present enough to realize the plentiful instability, severe weather is a possibility for Saturday through Monday. However, without great consensus on forcing, exact probabilities or timings are unknown at this time. There might (20%) be one more day of afternoon rain showers, but as broad troughing aloft shifts from northern Ontario towards the East Coast, ridging fills in behind and high pressure to around 1020mb will keep weather quiet Wednesday and Thursday. A cooling trend is also expected to accompany the arriving ridging as north and northwest flow will bring highs only in the upper 60s and low 70s Tuesday through Thursday. && .AVIATION /00Z TAFS THROUGH 00Z SATURDAY/... Issued at 713 PM EDT Thu Jul 11 2024 VFR conditions, under mostly clear skies and light winds will prevail in this period. By afternoon Friday, diurnal cumulus may develop, but VFR conditions should continue. && .MARINE... Issued at 357 PM EDT Thu Jul 11 2024 Light pressure gradient will keep wind gusts below 20 knots and wave heights below 3 feet for the next week. The greatest hazards will come in the form of thunderstorms which will threaten the lake Saturday through Monday, with a few storms being potentially strong to severe in the nearshore waters. Patchy dense fog is also a possibility in the wake of precipitation. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ UPDATE...JTP SHORT TERM...LC LONG TERM...GS AVIATION...JTP MARINE...GS