National Weather Service Raw Text Product

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