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Area Forecast Discussion
Issued by NWS Marquette, MI
Issued by NWS Marquette, MI
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421 FXUS63 KMQT 151654 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 1254 PM EDT Mon Jul 15 2024 .KEY MESSAGES... - Marginal risk (category 1 out of 5) of severe thunderstorms today mainly from 4-10 pm EDT. Main threat is damaging winds and large hail. - Cooler and drier for midweek with the arrival of high pressure. && .SHORT TERM /THROUGH TODAY/... Issued at 1254 PM EDT Mon Jul 15 2024 Early afternoon water vapor imagery shows a midlevel anticyclone centered around the Four Corners and a cutoff low just southwest of Hudson Bay. Stronger 500 mb flow between these features is spreading eastward into the Upper Great Lakes, with a notable shortwave trough now progressing into northern MN. High convective debris clouds are spreading into the local area ahead of this feature and also along the northern periphery of a decaying MCS over southern MN/WI, but there is some clearing noted over northern WI where some lower cu is developing. Gradual moistening is taking place over the western UP where dewpoints are creeping back up into the low to mid-60s. Surface pattern is a bit messy, but there is a cold front apparent from roughly Thunder Bay SWWD to about Fergus Falls, MN. Modest destabilization ahead of the incoming wave/cold front should continue over roughly the SW half of the UP this afternoon due to clearing skies and weak advection of better low-level moisture. Despite midlevel lapse rates decreasing to less than 7 C/km, this should allow for the development of 1000-1500 J/kg MLCAPE just ahead of the incoming disturbances. Further north toward the Keweenaw, Marquette area and points east, destabilization is less certain with MLCAPE likely remaining less than 1000 J/kg. Deep-layer shear does look good, increasing to 40-45 kt. Low-level winds are a bit more modest and may actually decrease a bit ahead of the front, leaving low-level convergence a question-mark. Still, high confidence in a rather quick-moving area of showers and thunderstorms moving across the UP from west to east this afternoon, primarily 4-10 pm EDT. Marginal risk (category 1/5) for severe weather with a few storms capable of damaging winds and large hail. Risk appears highest south of a line from roughly Manistique to Ontonagon. Cold and dry advection ensues tonight, ushering out the seasonably warm airmass of the last couple days. Skies clearing with lows in the mid-50s to near 60. && .LONG TERM /TONIGHT THROUGH SUNDAY/... Issued at 427 AM EDT Mon Jul 15 2024 Starting Monday evening, storms are expected to be ongoing over central Upper MI ahead of the cold front to the west. As the front and shortwave push east out of the area, storms exit our CWA by around midnight. Some of these storms could still be strong to severe given the bulk shear of ~35-40 kts, lightly capped MUCAPE of 500-1500 J/kg, and 1km helicity ~100 m2/s2. Otherwise the UP returns quiet as lows settle into the mid 50s to low 60s. Tuesday and Wednesday, the positively tilted mid level trough over northern Ontario becomes more vertically oriented as it pivots over the UP before swinging east toward Quebec and New England for Thursday. This results in a period of northwest flow, supporting some light northwest winds gusting up to 20 mph and cooler temps. A shortwave rotates over the UP on Tuesday ahead of the trough, yielding slight chances for light showers in the afternoon. With the main trough pivoting overhead on Wednesday, cloud cover and chances for showers increase again. That said, a drier airmass will be advecting in from the northwest, evident in the PWATs dropping to around 0.7-0.9". Thus, this round will also bring very low impact accumulations if any. Also with a couple hundred J/kg of MUCAPE, no severe weather is expected. Highs on Tuesday stay mainly in the 70s while Wednesday cools off even more with highs only in the mid 60s to low 70s. Lows Tuesday and Wednesday night dip into the 40s in the interior with 50s near the lakeshores. High pressure then builds in from the west Wednesday, continuing to shift east-southeast over the Great Lakes through the rest of the week into next weekend. This results in a gradual warming pattern late next week into the weekend with dry weather likely through the first half of the weekend. Also during this period, the mid level ridge over the west amplifies, resulting in troughing over northern Ontario/Quebec. That leads to the next precip coming from a shortwave trough dropping south across the Upper Great Lakes late next weekend, although confidence on timing is low given the spread in deterministic solutions at this time. From there, ensemble guidance indicates that the fairly drier pattern is expected to persist with another sfc high pressure building in from northwestern Canada as the amplified ridge eventually gives way and shifts eastward across the CONUS. This means that outside any additional shortwaves, precip will be largely driven by diurnal heating or lake breeze convergence moving into next week. && .AVIATION /12Z TAFS THROUGH 12Z TUESDAY/... Issued at 755 AM EDT Mon Jul 15 2024 VFR conditions expected to prevail for duration of TAF period outside of impending factors. First, smoke from upstream wildfires could cause visibility restrictions and will need to be monitored. For now, will keep at VFR, though. Also, a line of showers and thunderstorms is expected to move through the TAF sites this afternoon along and ahead of a cold front. Flight restrictions cannot be ruled out in any storms that become strong to severe. And, expect a windshift to the northwest with frontal passage. && .MARINE... Issued at 427 AM EDT Mon Jul 15 2024 Winds remain light and somewhat variable through this morning as weak sfc ridging moves over the lake and the next round of storms approaches from the west. Storms are expected to move over the west end of the lake this afternoon, continuing east across the lake into the evening hours. Some of these storms will be capable of producing gusty winds, frequent lightning, and isolated large hail. Patchy dense fog is possible, especially in the wake of precipitation. Winds turn west to northwest behind the cold front Monday evening into Monday night. Winds are generally expected to remain below 20 kts through the remainder of the forecast period as high pressure builds in from the west on Wednesday, continuing east-southeast over the Great Lakes Basin through the rest of the week and into the weekend. However, the strongest winds up to 20 kts are most likely on Tuesday and Wednesday. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... Dense Fog Advisory until 5 PM EDT this afternoon for LSZ250- 251-267. Lake Michigan... None. && $$ SHORT TERM...Thompson LONG TERM...Jablonski AVIATION...TDUD MARINE...Jablonski