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
764 FXUS63 KMQT 010123 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 923 PM EDT Sun Jun 30 2024 .KEY MESSAGES... - There is a slight chance (<20%) for patchy frost across portions of the interior-western UP tonight. - Dry weather continues through Monday evening. - Next rounds of showers and thunderstorms arrive Monday night, continuing into Wednesday. Gusty southerly winds up to 25-35 mph are also expected on Tuesday. - Warm and wet pattern expected to continue well into July. && .UPDATE... Issued at 922 PM EDT Sun Jun 30 2024 Main fcst concern overnight is how low temps will fall, and with that, the potential of frost for the first morning of July. Sfc high pres will be settling over the western Great Lakes during the night, allowing for calm/near calm conditions tonight across the fcst area. Skies are already clear, and the air mass is very dry. Precipitable water tonight will be running just 30-40 percent of normal to enhance what is already setting up to be a good radiational cooling night. Afternoon dwpts bottomed out in the mid 30s F at some sites across the fcst area, and that is likely a good indicator of where temps will be heading at the traditional interior cold spots. 12z MET guidance for KLNL had a min temp of 34F tonight, also a good indicator of where traditional interior cold spots across the w will end up. Fcst has been updated to knock a few degrees off of min temps. While fcst reflects mid/upper 30s F across a fairly large portion of the interior, would not be surprised at all to see the typical cold RAWS sites fall toward 30F. Expected coverage of possible frost across the interior w is still very low and spotty given the isolated nature of the lowest temps that are supportive of frost and also the short duration of the those lowest temps. && .SHORT TERM /THROUGH TONIGHT/... Issued at 231 PM EDT Sun Jun 30 2024 Robust upper ridging over the Plains is supporting a sprawling 1028mb surface high centered over MN this afternoon. With strong subsidence over the UP, there is hardly a cloud in the sky. In spite of this, temperatures remain quite cool; temperatures are only climbing into the lower 60s across much of the UP, while shoreline locations and the easternmost portions of our CWA are struggling even to break out of the upper 50s under chilly NW flow off of Lake Superior. NW winds are staying somewhat gusty across the eastern half of the UP, but gusts should fall back heading into the evening. Tonight, as the aforementioned high pressure becomes centered overhead, even stronger radiational cooling and calm winds will lead to widespread overnight lows in the upper 30s to lower 40s. The frost potential across the interior-western UP is still difficult to pin down, with most of the guidance staying just warm enough to preclude frost. Only about 10% of href ensemble members reach the mid 30s, while the NBM 10th percentile also only flirts with the mid 30s. Will note, however, that some spots in the western half of the UP fell farther into the 30s than expected, with the "winner" of the night (Watton) reaching as low as 34F. Therefore, have been just confident enough to come in a couple degrees under guidance, particularly across Iron and southern Baraga counties, where we may just get cool enough for patchy frost. This will continue to be monitored/adjusted as needed. In addition, dangerous swimming conditions for Marquette and Alger counties are expected through this afternoon. && .LONG TERM /MONDAY THROUGH SUNDAY/... Issued at 428 PM EDT Sun Jun 30 2024 The primary focuses of the extended forecast will be for Monday night through Tuesday night as well as a system moving through the 4th of July night, continuing into the weekend. The generally wet pattern returns Monday night. July starts off dry with mid level ridging centered over the UP. The sfc high continues shifting eastward as well, resulting in southerly flow, warmer temps, and increasing cloud cover late in the afternoon/evening. Highs on Monday will climb into the 70s, warmer in areas with downslope flow. Meanwhile, the mid level trough currently over British Columbia begins shifting east, continuing over the Canadian Prairie provinces through Tuesday. This sends a shortwave northeast over the Upper Mississippi Valley Monday night, lifting northeast through northwestern Ontario on Tuesday. This set up supports cyclogenesis in the lee side of the Rockies in southern Alberta tonight. The low is progged to move east, just north of the international border, through Tuesday morning. Then with the support of the northeast lifting shortwave alongside a left exit region of a ~110 kt upper level jet, the low deepens to ~993mb as it lifts northeast toward Hudson Bay by Wednesday evening. This system ends the dry period Monday night in the west as WAA/isentropic ascent touches off the first round of showers, later supported by the northeast rotating shortwave and increasing 900-850mb LLJ up to ~45-50 kts. Confidence is growing in a brief lull or even break in the showers late Tuesday morning/afternoon (better chances for a drier period in the west) before a second round of showers and thunderstorms ahead of the low pressure system`s trailing cold front continues PoPs into Wednesday. With limited elevated instability (100-300 J/kg of MUCAPE) for the first round, thunderstorms can`t be ruled out Monday night through Tuesday morning, but no severe weather is expected. Instability remains limited for the second round, but thunderstorm chances look slightly better with maybe a few hundred J/kg more of MUCAPE (6/30 12Z LREF indicates up to ~750 J/kg in the 90th percentile). Also, mid level lapse rates will be higher (approaching 6.5 C/km) and this round has better synoptic forcing; severe weather potential still remains low (<10%). With the LLJ overhead and a tighter pressure gradient on Tuesday, some breezy southerly winds are expected with gusts up to 25-35 mph. Model soundings do leave potential for mixing to yield higher gusts up to 40-45 mph and the 6/30 12Z HREF does show probabilities of gusts exceeding 35 mph reaching around 50-70%. This will bear monitoring with future forecast packages. Tuesday will be slightly cooler than Monday with highs in the mid 60s to mid 70s. On Wednesday, the mid level trough now centered over northern Ontario, will moves east over Quebec. The last precip should end by the afternoon as PVA ends behind the cold front and departing trough. The dry period looks to persist through most of the 4th of July. Temps on Wednesday and the 4th of July will be the warmest for the week with highs in the mid 70s to mid 80s and lows in the mid 50s to low 60s. Confidence is growing in a sfc low developing over the lee of the central Rockies Wednesday night, lifting northeast into the Great Lakes region for Friday afternoon into Saturday. A mid level trough also moves through the Upper Great Lakes Friday into Saturday morning. NBM PoPs captures this with an increase in PoPs to around 30-50% Thursday night from the southwest, then 40-60% PoPs for Friday into Friday evening. With uncertainty increasing Saturday onward, 15-35% PoPs are sprinkled through the rest of the weekend. && .AVIATION /00Z TAFS THROUGH 00Z TUESDAY/... Issued at 717 PM EDT Sun Jun 30 2024 Very dry air mass associated with high pres settling over the western Great Lakes tonight will result in VFR continuing thru this fcst period at IWD/CMX/SAW. Winds will be light to calm at all terminals tonight, then on Mon, southerly increasing to around 10kt, except becoming ESE at CMX. && .MARINE... Issued at 428 PM EDT Sun Jun 30 2024 High pressure continues shifting east over the Great Lakes through, maintaining light winds below 20 kts through at least Monday. Another system presses in from the west Monday night, bringing with it waves of rain and maybe some thunderstorms, into Wednesday. These rain showers may support fog developing and periods of low visibility on the lake. A stout 900-850mb low level jet up to ~45-50 kts will also come with this system. This along with the tighter pressure gradient will support increasing southerly winds Monday night into Tuesday. Internal probabilistic tools suggest a low probability (15-30%) that winds will exceed 33 kts. Given the increasingly warm airmass and stability over the lake at the time, the going forecast represents winds to 20-30 kts over the eastern 2/3 of the lake. That said, localized terrain driven influences should support small pockets of mixing down low end gales, particularly downwind of the lakeshores east of Marquette and along the northern shores of the Keweenaw. Given the setup and the consensus of the strength of the low level jet, this will bear monitoring in future forecast packages. Another round of moisture will lift through Tuesday night into Wednesday while winds settle down. The cold front presses through west to east Tuesday night into Wednesday morning, allowing winds to become westerly/southwesterly for Wednesday. Another period of stronger winds up to 20-30kts, looks possible between the Keweenaw and Isle Royale Wednesday in this southwesterly flow. High pressure returns briefly for Thursday with a weaker low pressure system expected to pass over the Upper Great Lakes next weekend. Light winds below 20 kts returns Wednesday night, continuing likely through the rest of the work week. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ UPDATE...Rolfson SHORT TERM...LC LONG TERM...Jablonski AVIATION...Rolfson MARINE...Jablonski