289 FXUS63 KAPX 051758 AFDAPX Area Forecast Discussion National Weather Service Gaylord MI 158 PM EDT Wed May 5 2021 .UPDATE... Issued at 937 AM EDT Wed May 5 2021 Still plenty of low clouds out there this morning, with even areas of drizzle impacting some of the interior of northern lower Michigan. Aggressive drying noted just upstream, and would expect some of this dry air and increased surface based mixing to help scour out the overcast heading through this afternoon. Temperatures will be several degrees below normal, with highs mostly ranging through the 50s. && .NEAR TERM...(Today through Tonight) Issued at 330 AM EDT Wed May 5 2021 Impactful weather: Frost development likely late tonight north. Pattern synopsis and forecast: Large scale upper troughing continues to engulf much of the heart of the country, including the Great Lakes, with several shortwaves seen within this troughing. The one of concern for nrn Michigan, is wrapping ESE through south central Canada, and was associated with sfc low pressure and spotty light precipitation around the Dakotas, resulting from low to mid level weakish theta-e convergence and DPVA in a steep 850-500mb lapse rate regime. In nrn Michigan attm, skies remained mostly cloudy with low level moisture stuck under an inversion. There have been some very spotty drizzle at times, seemingly few and far between, and maybe more so in the interior higher terrain of nrn lower. Not all that much weather for today and tonight. Maybe some patchy drizzle continues for a couple/few hours past daybreak, but the mostly cloudy low level clouds are expected to scattered out today, with the best afternoon cumulus likely in the SE/E CWA. Some gusty NW winds are expected once again today, but those will fall off heading through tonight, as some relatively higher pressure moves into the region late tonight. Also arriving late tonight, is the aforementioned shortwave currently in south central Canada. The theta-e convergence associated with the wave weakens with time through tonight, and the overall deep layer -divQ is fairly weak late tonight. There is however, still a slight chance of a little light rain around the Frankfort, Manistee and Cadillac areas prior to daybreak. All-in-all, pretty quiet weather. High temperatures today will largely be in the low to mid 50s. Lows tonight will largely be in the low to mid 30s, with upper 30s/near 40F in the GTV Bay region. The coldest temperatures will be in eastern upper/far nrn lower and far NE lower. These readings, combined with thinnest cloud and light winds overnight will necessitate a frost advisory in far nrn lower (we have not started issuing those headlines for eastern upper yet). && .SHORT TERM...(Thursday through Friday) Issued at 330 AM EDT Wed May 5 2021 High Impact Weather Potential: Frost potential Thursday night and Friday night... Pattern Synopsis/Forecast: At the start of the short term...broad troughing will be in place over much of the Eastern US, with amplified ridging extending northward from the desert southwest into the Canadian Rockies, with troughing upstream of that, poised to move onto the west coast of North America. A few shortwaves look to pivot through the flow into troughing over the Great Lakes, leading to periodic precipitation chances that will make overnight low temperature forecasts quite challenging. As west coast troughing tries to progress eastward...will look for the edge of that ridge to press up against our troughing...strengthening the thermal gradient and ultimately, a northwest-southeast oriented jet max that, as it moves through the Great Lakes Friday into Friday night, will favor subsidence and surface high pressure over the region. With a cold air mass already in place...will be watching Friday night especially very carefully for frost potential as skies may become clear with light winds in the region. Primary Forecast Concerns: Frost potential and precipitation chances through the period. 500mb heights look to fall through the first part of the short term...as a strong shortwave dives southward into the base of the trough Thursday night. That said...will be looking for high temperatures to primarily flutter around in the 40s here at the surface both days. In addition...with mid-level moisture around for most of the first 24 hours or more of the short term...will be expecting a more fall-like couple of days than early May-type weather. First shortwave, less amplified than the second, looks to rotate through early Thursday with a broad swath of mid-level moisture associated with it...with its surface reflection potentially centered somewhere just to our southwest. This will lead to some rain (and/or snow) potential for the first half of Thursday before it scoots out...though there may be some low-level dry air to contend with at times. The second shortwave dives in late Thursday into Thursday night...increasing cloud cover and perhaps bringing another shot at overnight precipitation for much of the area (yay for those concerned about frost)... which may be mixed with or fall as snow in some locations, given the cold air mass in place. The second shortwave lingers moisture over the region into Friday afternoon...slowly departing eastward through the day and most likely ending precipitation chances...at least, for a time. Additionally, as there may be some potential for skies to stay a little clearer along the eastern half of the CWA Thursday evening/night before clouds move in...will have to monitor that area, especially the typically colder locations, for somewhat increased frost potential then. Temperatures may be cold enough for some to be wary of freeze concerns...but frost development may be hindered by winds and cloud cover as some minor cold advection moves in aloft with the second shortwave. As the second shortwave departs eastward through the day Friday...it will put the western half of the CWA under the frost potential microscope for Friday night...as it would be more likely to stay clear there. Additionally, the western half of the CWA will be closer to the ridge and high pressure...but will have to watch for perhaps another shortwave to wiggle through the flow and maybe keep the cloudiness over the region for Friday night. These details will surely be monitored in the coming shifts...as Friday currently looks to be the better night of the short term for stereotypical radiational cooling potential. .LONG TERM...(Friday night through Tuesday) Issued at 330 AM EDT Wed May 5 2021 High Impact Weather Potential: Frost/freeze potential at times... Going into the long term...will be looking for non-zero precipitation chances through the weekend as more shortwaves wiggle through the troughing over the Great Lakes...and something of a shift in the pattern as the west coast troughing tries to cut under the ridge out west. This would lead to a more zonal, rather than amplified pattern, though we would be on the colder, northern side of things and likely stay cool right on through the weekend. This means frost/freeze potential is non-zero as well. As flow becomes more broad/zonal aloft...will have to watch for the rear of the jet max aloft to lift northward...which could lend to upward motion in support of surface troughing as another shortwave drops in from the north. Attm...the low pressure and the heaviest moisture looks to stay south of the area...but future shifts will be keeping an eye on trends as things will certainly change in the coming days. Otherwise...with various shortwaves swinging through the flow and reinforcing troughing over the region...things should stay on the cool and perhaps dreary side for Mother's Day weekend...with potential for perhaps some moderation in temperatures for the end of the extended. && .AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon) Issued at 155 PM EDT Wed May 5 2021 Conditions expected to steadily improve across the taf locations this afternoon and evening. More clouds arrive tonight, perhaps lowering cigs back to MVFR at KMBL late. Gusty winds quickly subside this evening. && .MARINE... Issued at 330 AM EDT Wed May 5 2021 Low pressure deepens and tracks up through New England and Atlantic coast today through tonight, while relatively higher pressure moves into northern Michigan. The pressure gradient will remain tight enough today for advisory level winds from Whitefish Bay, through the St. Mary's, and into the NE lower nearshore waters around Presque Isle Light. Speeds drop off tonight and remain sub-advisory through Thursday night. Chances for showers returns in the Thursday through Friday evening timeframe. && .APX WATCHES/WARNINGS/ADVISORIES... MI...FROST ADVISORY from midnight tonight to 9 AM EDT Thursday for MIZ016>018-022-023-099. LH...SMALL CRAFT ADVISORY until 8 PM EDT this evening for LHZ347-348. LM...NONE. LS...SMALL CRAFT ADVISORY until 8 PM EDT this evening for LSZ321-322. && $$ UPDATE...MB NEAR TERM...SMD SHORT TERM...FEF LONG TERM...FEF AVIATION...MB MARINE...SMD