498 FXUS63 KMQT 201129 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 729 AM EDT Sat Mar 20 2021 .SHORT TERM...(Today and tonight) Issued at 448 AM EDT SAT MAR 20 2021 ...ELEVATED FIRE WEATHER CONCERNS TODAY... As high pressure continues to slowly slide east through the Lower Great Lakes region, weather will remain dry and warm through the short-term period. As the ridge slides east the pressure gradient will tighten on its backside in response to a trough/frontal boundary approaching from the western Plains. South-southwest winds will become gusty today across the U.P. with 20-30 mph gusts expected to be widespread. The SW wind downslope areas could see a few gusts as high as 35 mph at times. The strong SW wind along with clear skies will lead to deep mixing and temps in the upper 50s and low 60s for highs across the west half (low 50s east half due to moderating onshore wind from Lake Michigan). These highs are near the max end of all guidance, but wouldn't be surprised to a few readings hit the mid 60s over the west half with deeper mixing possible. The main concerns focus on fire weather today into at least this evening thanks to this combination of the gusty southerly winds, warmer temps, and very dry air mass in place. The key will be just how deep the mixing will be. Looking at dew points off fcst soundings assuming mixing to 900 mb or a bit higher expect sfc dew points mostly in the low teens although wouldn't be surprised if a few spots dip into the single digits over the west. Along with temps around 60, this means RH values bottoming out as low as 15% across the west and central U.P., and around 30% east. The exception will be right along Lake Michigan where the wind off the water will advect cooler and more moist air onshore. From coordination with the fire weather partners yesterday it was decided to issue an SPS highlighting the potential for grass fires today and reminding everyone to avoid outdoor burning. Will continue the SPS into at least the early evening hours as RH recovery will be poor tonight due to mixing from winds maintaining RH values as low as 30 pct west and 50 pct east into the evening. The primary concern will be for small grass fires over open areas since the grass has dried out after more than a week without precipitation, whereas much of the heavily forested areas are still retaining several inches to a foot or more of snow. Gusty southerly winds will likely continue tonight, especially for downsloping areas along Lake Superior where gusts could reach 35 mph or more at times. Winds will be enhanced by a 50 kt LLJ moving across the area. Min temps tonight should be on the higher end of guidance due to the mixing of the winds. Look for low temps generally in the 30s. .LONG TERM...(Sunday through Friday) Issued at 435 AM EDT SAT MAR 20 2021 Starting off Sunday morning, the upper level weather pattern will continue with split flow energy for the northern and southern jet streams with respect to latitude. An embedded shortwave disturbance aloft at 500mb will continue to be enhanced via surface cyclogenesis. A surface lo over Manitoba will deepen as it propagates to the east on Sunday. This will continue to keep Upper Michigan in the warm sector, along with gusty sw winds, and above average temperatures. Low relative humidity values below 30 percent are likely as temperatures surge by Sunday afternoon to values 20-25 degrees above average. This will increase fire weather concerns for Sunday, but should stay below headline criteria. As the surface cold front advances toward the southeast Sunday night, precipitation will begin to occur along it. As the column begins to cool and moisten aloft, rainfall will be the result across Upper Michigan. It will be a cold rain Sunday night into Monday for areas that do indeed receive it. At this time, will continue the trend of slight chance to chance rain in the forecast. Temperatures from Sunday night into Monday will be mild, with lows not going cooler than near 40 degrees before warming up to the middle 40s to lower 40s. The only exception looks to be in the northern Keweenaw area where a secondary cold front and cloud cover will assist with temperatures staying on the lower threshold through day's end. On the heels of the departing shortwave on Monday afternoon, a stronger surface lo will begin to develop via lee side cyclogenesis from the 4 corners region. Upper level jet energy will eject out of the Rockies by Monday night, and models are beginning to signal a warm conveyor belt of energy being transported well ahead of the main surface lo from the Central Plains into the Upper Midwest area close to Upper Michigan. Most likely scenario at this point would be an additional shot of light rain showers Monday night into Tuesday. By Tuesday morning, the bulk of the energy will likely become absorbed into the southern jet stream, and quickly propagate toward the Great Lakes. This longwave trough will become negatively tilted as it approaches the Great Lakes. Quite a bit of moisture will accompany this surface lo, so we could see a decent shot of rainfall accumulation for the area. PWAT values of 0.5" to 1" from Tuesday afternoon into Wednesday evening will be advected into the area. Models do show the moisture advecting into the area, but the GFS is the most aggressive with the surface lo advecting in much colder temperatures behind it. 850mb temperatures per the GFS by early Thursday get as cold as -12C, which would cause any lingering precipitation to fall as snow. Certainly something to watch as our area slowly transitions into a spring weather pattern versus a predominant winter weather pattern. Thursday afternoon into early Friday, an additional weak shrtwv embedded in the upper level flow will approach the region and perhaps interact with a mesolow that may develop over eastern Lake Superior. This could bring an additional shot of lake enhanced snow shower activity with temperatures hovering slightly above freezing on our northern shorelines adjacent to the lake. Friday into Saturday is trending toward an upper level ridge pattern temporarily developing over the Upper Midwest and northern Great Lakes region. On the backside of this upper level ridge, models begin to diverge with deterministic solutions trending either dry or with a mid-latitude cyclone developing over the Central Plains that may impact the Great Lakes by the end of next weekend. Despite the anticipated active weather week approaching, the CPC is trending toward slightly above average temperatures and near normal chances of precipitation. && .AVIATION...(For the 12Z TAFS through 12Z Sunday morning) Issued at 725 AM EDT SAT MAR 20 2021 High pressure remains in control which means TAFs continue to be VFR. Only concerns will be a period of LLWS at CMX today and then LLWS at all terminals tonight as a strong low-level jet max moves across the region. SW winds become a bit gusty at all of the terminals later this morning, over 30 knots at IWD, 25-30 knots at SAW and nearly 25 knots at CMX. && .MARINE...(For the 4 AM Lake Superior forecast issuance) Issued at 448 AM EDT SAT MAR 20 2021 Southwest winds ramp up to 20-25 knots over the west half of the lake this morning but then diminish a bit this afternoon. Over the east half, southerly winds are expected to increase to around 30 kts late this afternoon and continue at 30 kts through Sunday evening. Winds on the west half will remain in the 20-25 kt range through the weekend. Lighter winds are expected Monday as a low pressure trough moves over the area. By Tuesday, a low pressure system over the Mississippi Valley will result in winds veering around to NE and increasing to 20-30 kts, greatest over the western third of the lake. NE winds may even reach low-end gales over the west end late Tuesday into Wednesday morning before backing N and diminishing to 20 knots or less late Wednesday night into Thursday as the low lifts northward across the lake and weakens. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...Voss LONG TERM...BW AVIATION...Voss MARINE...Voss