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Displaying AFOS PIL: AFDAPX Received: 2019-02-18 11:42 UTC
140 FXUS63 KAPX 181142 AFDAPX Area Forecast Discussion National Weather Service Gaylord MI 642 AM EST Mon Feb 18 2019 .NEAR TERM...(Today through Tonight) Issued at 317 AM EST Mon Feb 18 2019 ...Fairly quiet, but cold temps tonight... High impact weather potential...none. Low pressure is over n central PA, moving ne. This low will weaken today as secondary development occurs off the east coast. Associated snow swath over the southern Great Lakes is moving east and slowly diminishing. That will exit, and in its wake a large area of high pressure will move from s central Canada into the Great Lakes thru tonight. Very light snow is occurring down by OSC/Gladwin. Expect that to gradually exit over the next few hours, with little if anything left after 7 am. Cloud cover elsewhere largely consists of mid and high clouds, and there are a number of thin spots, especially north of a TVC-APN line. Cloud cover will substantially erode from n to s, especially after sunrise. Eastern upper MI should be mostly sunny by late morning, and most of northern lower will do the same during the afternoon. The lakes will provide some exceptions, though. Our initial 1000-850mb winds are from the ne, pushing lake clouds into ne lower MI (where higher synoptic clouds are present). However, as the surface low departs and loses influence, the fetch backs to north by midday, and nw/nnw by late afternoon. That will support partly to mostly cloudy skies near/w of M-37 in nw lower MI this afternoon. We also currently see lake clouds and snow showers in the immediate MQT area on ne winds. with 850mb temps around -16C. Those will gradually get shoved eastward, with increasing clouds in western Chip/Mack Cos this afternoon, along with a chance of snow showers. 1000-850mb winds back a little further to the wnw as we move thru tonight. The arrival of surface high pressure and a drier airmass will limit lake effect potential. A chance of snow showers continues to be justified in western Chippewa Co. In nw lower, ice cover on Lake MI will help limit snow showers to primarily Leelanau/Benzie/ Manistee/Gd Traverse Cos. Partly to mostly cloudy skies will hold in those areas, while we are partly cloudy to mostly clear elsewhere. Max temps today in the teens to lower 20s. Will go sharply below guidance min temps tonight, especially away from Lk MI, where lows of -5 to -15f will be common. && .SHORT TERM...(Tuesday through Wednesday Night) Issued at 317 AM EST Mon Feb 18 2019 High Impact Weather Potential...Widespread accumulating snow Wed into Wed night. Possibly some minor ice accumulation south of M-72 Wed afternoon-evening due to freezing drizzle. Pattern Synopsis/Forecast...Anomalous ~1040 mb surface high will sit overhead Tuesday morning, with its center drifting east of Lower Michigan by late afternoon. Generally fair weather expected through this timeframe with subtle warm air and moisture advection developing behind the departing high heading into Tuesday night. Attention then turns to a developing low over the Middle Mississippi Valley Wednesday morning that will lift through the Great Lakes region Wednesday night. This system will bring the next round of widespread accumulating snowfall to northern Michigan. Primary Forecast Concerns...Diminishing light lake effect potential on Tuesday. Snow timing/amounts on Wednesday. Conditions will be supportive Tuesday morning for some lingering lake effect along the Lake Michigan shoreline from Manistee to the Leelanau Peninsula. Light ambient wind fields Monday night will lead to land breeze development and enhanced convergence just offshore, where a dominant band is expected to hug the lakeshore through at least mid-morning Tuesday. As the high drifts east during the day, developing southwest flow will drive the band farther inland as it begins to gradually dissipate in the face of increasing warm air advection and falling inversion heights. Offshore SSW flow near Whitefish Bay should preclude any lake effect up that way. Limited moisture and inversion heights at or below 4000 feet should limit overall strength of the lake effect, so overall impacts should be low with little to no accumulation. The only concern would be if the band lingers in one place Tuesday morning along the shoreline before diurnal winds give the weakening band some forward momentum. Main focus of the period revolves around Wednesday's system. Increasing isentropic lift and upper level difluence will spread across northern Michigan during the day ahead of the approaching system. At the same time, moisture return will be decent as we tap into some Gulf moisture by afternoon. The exact track the surface low will take is still far from certain, as evidenced by the 18.00Z NAM being a significant outlier, taking it well north into eastern Upper. For now will discount that solution and take a general consensus of other guidance, which favors the low lifting northeast through the Lower Peninsula. Snow looks to arrive around or shortly after 7am Wed south of Grand Traverse Bay, spreading northeast across the remainder of the forecast area by the noon hour. The dry slot looks to gradually encroach from the south Wed afternoon into the evening, kicking off a south to north diminishing trend Wed night, with remaining system snow exiting the Tip of the Mitt and eastern Upper by daybreak Thursday. Due to lingering uncertainties with regard to storm track, still too early to pin down precise snowfall amounts. However, there is a consistent signal among various guidance for the heavier QPF (up to a third of an inch) to lay out across the Tip of the Mitt and eastern Upper. With snowfall ratios generally in the 10-15:1 range, looks like we could be dealing with advisory level snowfall of about 3 to 5 inches north of M-72 between 7am Wed - 7am Thu. Lesser amounts of 1 to 3 inches as you go south of M-72, as that area could see some freezing drizzle (up to a tenth of an inch of icing) mix in Wed afternoon-evening as the dry slot works into the area. This far out these forecast snow/ice amounts are preliminary and will be subject to later refining, of course, but overall model trends have been fairly consistent over the last 24 hours, so forecast confidence is medium at this time. The good news is winds don't look too strong to cause blowing/drifting problems with this system, with gusts generally around 20 mph or less. .LONG TERM...(Thursday through Sunday) Issued at 317 AM EST Mon Feb 18 2019 High Impact Weather Potential...Minimal at this time. As our snow system departs Thursday morning, slightly colder air in its wake will wrap around back into eastern Upper and northwest Lower to generate a period of lake effect. However, overlake instability appears marginal with H8 temperatures only dropping to around -10 to -11C and inversion heights generally 3000 feet or less. Conditions will slowly become less favorable with time through Friday. A weak wave is progged to push through on Saturday, bringing a chance of snow, perhaps mixed with rain in some areas as temps climb into the mid 30s. Sunday looks potentially much more interesting as models are trying to latch onto a more robust system lifting into the Great Lakes. Very low confidence in storm track, but medium-range guidance shows a fairly intense developing surface low lifting somewhere through the region. This would have the potential to produce significant wintry precip somewhere across the region (much too early to tell where, as we don't yet know the system's track) and likely gusty winds. && .AVIATION...(For the 12Z TAFS through 12Z Tuesday morning) Issued at 642 AM EST Mon Feb 18 2019 Some MVFR cigs at APN this morning, thanks to ne low level winds off Lk Huron. Those winds will back today, as low pressure moves east away from the region. MVFR cigs will exit APN, but eventually roll in off of Lake MI into TVC/MBL by tonight. Otherwise mostly VFR. Light n to nw winds. && .APX WATCHES/WARNINGS/ADVISORIES... MI...NONE. && $$ NEAR TERM...JZ SHORT TERM...MK LONG TERM...MK AVIATION...JZ