Area Forecast Discussion
Issued by NWS Marquette, MI
Issued by NWS Marquette, MI
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825 FXUS63 KMQT 130847 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 447 AM EDT Sat Jul 13 2024 .KEY MESSAGES... - Seasonably warm Saturday through Monday with periods of showers and thunderstorms, some of which could be strong to severe. - Cooling and drying trend into the midweek portion of next week with the arrival of high pressure. && .SHORT TERM /TODAY/... Issued at 446 AM EDT Sat Jul 13 2024 Water vapor imagery/surface analysis early this morning indicate subsidence over Upper Michigan due to upper level ridging. This equates to mostly clear skies and a warm morning with temperatures holding in the 60s across the forecast area per current ground-based obs. Limited cloud cover and WAA in the southerly surface flow will push today`s highs well into the 80s with downsloping areas near Lake Superior approaching the 90 degree mark. In addition to the heat, focus will be on a shortwave trough approaching from the west this afternoon. CAMs/HRRR solutions, though, keep any convective development confined to the far western portions of the UP mid/late afternoon with the shortwave being counteracted by high pressure over the remainder of the forecast area until the evening hours. && .LONG TERM /SUNDAY THROUGH FRIDAY/... Issued at 353 PM EDT Fri Jul 12 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 through this weekend. This will lead to the primary driver of sensible weather to be weak shortwave impulses in the zonal flow. While the synoptic 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, especially in the form of MCS`s. High pressure then settles over the region by Tuesday, allowing for a cooler dry period towards the middle and late week period next week. Sunday, another warm day is on the horizon. The NBM looks to be on the high side of most guidance showing highs approaching 90, contrasting the median of available guidance showing highs on Sunday in the low to mid 80s in the interior with upper 70s near the Great Lakes. Moisture values increase as well, with the PWATs exceeding 1.5 inches representing the 90th percentile of climatology by the NAEFS and GRB sounding climatology. Dew points are forecast to be around 70 for at least some period of time for much of the UP, with the highest chances (60-80%) of exceeding 70 being the south-central creating quite muggy conditions. Monday looks to be similarly warm, though slightly lower chances of dew points being oppressively high. These hot and humid 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 over 2000 J/kg on Sunday (with the 90th percentile showing worst-case values of over 3000) and values around half of that on Monday. 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 Sunday and Monday. However, without great consensus on forcing, exact probabilities or timings are unknown at this time. Another complicating factor is that the NAM Nest is showing the primary storm mode Saturday is MCS- like, which should be a good analog for conditions on Sunday and Monday. Predicting the location of upstream MCS development is highly challenging at time periods of 48+ hours. By Tuesday, broad troughing aloft shifts from northern Ontario towards the East Coast and ridging fills in behind. As a result of the advancing ridging, 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 /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 128 AM EDT Sat Jul 13 2024 VFR conditions and light winds will prevail in this TAF period. Some fog/mist will be possible overnight at KIWD and KSAW, but confidence is low. Guidance continues to lack concensus with tomorrow`s convective event. At this point, it continues to look as if KIWD may begin seeing thunderstorms by Saturday afternoon. && .MARINE... Issued at 353 PM EDT Fri Jul 12 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. && $$ SHORT TERM...TDUD LONG TERM...GS AVIATION...JTP MARINE...GS