Area Forecast Discussion
Issued by NWS Marquette, MI
Issued by NWS Marquette, MI
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475 FXUS63 KMQT 292025 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 425 PM EDT Mon Apr 29 2024 .KEY MESSAGES... - Isolated to scattered showers, some drizzle, and patchy fog continues into tonight. Some fog may be locally dense at times in high terrain, especially in the Keweenaw. - Active pattern continues as a series of low pressure systems track across the region into early next week. Above normal temps/precip are expected including thunderstorm chances. - Elevated fire weather conditions are possible over the west half of Upper Michigan on Wednesday, but will depend on the preceding precipitation. && .SHORT TERM /THROUGH TONIGHT/... Issued at 424 PM EDT Mon Apr 29 2024 RAP analysis has the weak 1006 mb low pressure system over northwest WI with the negatively tilted trough over MN. Low level cloud cover has kept the area fairly insulated today, limiting temperatures to the 40s most of today. With some southeast downslope flow, a few spots in the west may reach into the 50s yet this afternoon. With ample moisture and periods of rain showers, patchy fog has been observed in the METARs and on cameras, especially in the keweenaw where upslope flow off Lake Superior has brought 1/4 mile visibilities to Houghton County Memorial Airport much of today, only to lift to 1/2 mile periodically. The sfc low is progged to slowly meander over western Upper MI through this evening into tonight, bringing an occluded front northeastward with it. This alongside PVA from the mid level trough will yield some isolated to scattered showers. With limited instability, only a few rumbles of thunder are expected. Showers/drizzle will lift northeast tonight as the midlevel trough pivots over Lake Superior and the sfc low slowly weakens as it meanders northeast with it. Areas of fog will continue, especially in the wake of these showers and in upslope flow over the west, especially in the Keweenaw. The continuing low clouds and fog will keep temperatures tonight in the mid 30s to low 40s with warmer temps in the east half of the UP. Additional accumulations through tonight are forecast around 0.1" to 0.25". && .LONG TERM /WEDNESDAY THROUGH MONDAY/... Issued at 415 PM EDT Mon Apr 29 2024 Period of active weather continues with a series of low pressures systems tracking across the area into early next week. There will be several chances for rain with these systems with the best chance of widespread moderate rainfall likely occurring with the system Thursday into Friday as models indicate a feed of Gulf moisture ahead of it drawing in PWAT values in excess of an inch. Starting Tuesday, a mostly dry frontal passage will be moving across the area tonight, but there may be some sprinkles/drizzle along and ahead of the front. Model soundings indicate a potential for a few hours of post-frontal upslope drizzle for the Copper Country Tuesday morning associated with moisture wrapping around the surface low tracking north of the area. Otherwise, expect mostly cloudy skies with highs ranging from the 50s near Lake Superior and east to the lower to mid 60s interior west and south central. A vigorous 500 mb shortwave trough approaches from the Northern Plains Tuesday evening as it becomes negatively tilted and pivots across the area late Tuesday night into early Wednesday. There`s very little time for moisture to return ahead of this disturbance for destabilization and the nocturnal timing further limits thunder potential. However, there`s very good agreement in convection riding into the area along the cold front to our west Tuesday afternoon. These storms appear to grow upscale into an MCS that moves fairly rapidly across the area late Tue night into early Wed. At this point, it looks like the best chance for widespread rainfall will be aligned over the western counties and maybe some of the north central counties closer to the system`s track and where the better deep layer qvector convergence and isentropic ascent is fcst. Any storms that make it into our area should be elevated and shouldn`t pose a hazard. The window for rainfall is brief (~3 hours) leading to light rain amounts less than 1/4 inch. Not great agreement among the models with how much mixing will occur on the backside of this system on Wednesday afternoon. The GFS soundings show the potential of mixing to 6-7 kft through a fairly dry airmass which could drop dew points into the lower 30s (and perhaps lower) over the interior west with min RHs dipping to 30 pct or less over the interior west half. Deep mixing off GFS soundings also suggests westerly gusts could reach near 35 mph. Meanwhile, NAM soundings depict more clouds with less mixing (only to 3-4 kft) yielding lesser wind gusts (20 mph or less) and less afternoon drying of dew points. If the GFS scenario of deeper mixing pans out the combination of gusty winds and lower RHs could potentially lead to elevated fire danger, however the recent moderate rainfalls over the last week could also imply wetter soils/fuels that could limit the threat. High pressure builds in Wednesday night resulting in dry conditions, but then the focus shifts to a low pressure developing over the Plains on Thursday then tracking across our area Thursday night. As a result, rain chances increase on Thursday ahead of the warm front as it lifts north then rain chances end behind Friday`s cold frontal passage. Ensemble probabilities indicate it`s likely that much of the area should see QPF totaling a quarter inch or more during this period with a chance (near 50 pct) of QPF reaching a half inch or more south central. Additional generally light rain chances look to continue through next weekend as weak shortwave impulses continue to move through the mid-level trough hanging over the area. && .AVIATION /18Z TAFS THROUGH 18Z TUESDAY/... Issued at 206 PM EDT Mon Apr 29 2024 A low pressure system currently centered over northwest WI this afternoon will slowly meander northeast over Upper MI through this evening, then Lake Superior overnight into Tuesday. During this period, low clouds and fog will impact flight conditions. As the occluded front lifts northeast with the sfc low, a round of isolated to scattered showers will lift with it into the evening hours. SAW and IWD will see periods of IFR to LIFR cigs and vis with these showers as well as lingering drizzle/fog, but both sites are expected to fall to LIFR tonight. CMX is expected to remain in VLIFR through most of tonight as plenty of moisture and upslope flow keeps fog around and cigs low. All sites are expected improve to MVFR by Tuesday afternoon. && .MARINE... Issued at 415 PM EDT Mon Apr 29 2024 East-northeast gales will quickly fall blo gales late this afternoon/evening as the sfc low now over northwest WI gradually lifts over central Lake Superior later tonight and winds become less than 20 kts. East to southeast winds increase to 20-25 kts Tuesday night, becoming westerly and increasing to 25-30 kts behind a cold front on Wednesday. There is now less than 20% chance for westerly gales up to 35 kts could occur on the windward side of the Keweenaw shoreline. Winds quickly diminish below 20 kts Wednesday night and stay light until the next low pressure approaches on Thursday bringing another episode of gusty easterly to northeasterly winds Thursday night into Friday with maybe a few low-end gale gusts to 35 kts possible over north central and eastern portions of the lake. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... Small Craft Advisory until 11 PM EDT /10 PM CDT/ this evening for LSZ240-241. Small Craft Advisory until 4 AM EDT Tuesday for LSZ243>246. Small Craft Advisory until 2 AM EDT Tuesday for LSZ247-248. Lake Michigan... Dense Fog Advisory until 11 PM EDT this evening for LMZ221-248- 250. && $$ SHORT TERM...Jablonski LONG TERM...Voss AVIATION...Jablonski MARINE...Voss