Area Forecast Discussion

FXUS63 KAPX 182029 CCA
Area Forecast Discussion...CORRECTED
National Weather Service Gaylord MI
329 PM EST Sun Nov 18 2018
.NEAR TERM...(Through Tonight)
Issued at 310 PM EST Sun Nov 18 2018
...Brief Break From the Snow, but More is on the Way...
High Impact Weather Potential: Lake enhanced snow showers off Lake
Michigan ramp up late tonight, potentially impacting morning
Pattern Synopsis/Forecast: Afternoon composite analysis reveals 
broad westerly flow and a fairly tight N-S thermal gradient in 
place across the Great Lakes, associated upper jet streak 
stretches from the Ohio Valley up through New England. Weakening
upper jet entrance region forcing along the thermal gradient 
continues to produce a narrow corridor of snowfall across far SE
lower Michigan and northern Ohio. 
Meanwhile, elongated surface high pressure and wedge of dry air 
sits across lower Michigan and has finally brought a good deal of 
clearing skies/sun to much of northern Michigan. Further north, 
low pressure is over Hudson Bay with an arctic boundary arcing 
down through Ontario and into eastern Lake Superior. Satellite
imagery and MRMS radar data shows a narrow band of snowfall with 
the front that extends from eastern Lake Superior into SE Ontario. 
Primary Forecast Concerns: Lake enhanced snows tonight through 
Arctic boundary and thin line of snow to the north will be 
pressing down across Lake Superior to just north of the U.P. this 
evening and eventually down into and stall through eastern upper
Michigan by morning. Stronger synoptic forcing and steeper low 
level lapse rates remain out across southeast Ontario. But with 
Lake Superior over lake instability, still anticipating enhanced 
snowfall to gradually press down into northern Chippewa county 
tonight along with several inches of snow possible across a small
portion of Chippewa county (Paradise area). 
Meanwhile, northern stream short-wave and attending surface low 
(clipper-ish system) will swing out of southern Canada and into 
the western Great Lakes toward morning and cross northern 
Michigan on Monday. This will begin to spread some light snowfall 
of it's own into the region during the late overnight timeframe. 
Bigger forecast concern is the degree of W/SW flow lake enhancement
we see in the vicinity of the stalled boundary through the 
Staits/tip of the mitt late overnight and continuing Monday. 
Somewhat modest over lake instability. But combined with low level
convergence and increasing synoptic moisture/forcing through the 
DGZ, think a few inches of snow is possible just by daybreak in 
the Tip of the Mitt with more to follow on Monday. Plan is to  
hoist a winter weather advisory for the Tip of the Mitt with the 
afternoon forecast (see below for more). 
.SHORT TERM...(Monday through Wednesday)
Issued at 310 PM EST Sun Nov 18 2018
High Impact Weather Potential: Snow expected Monday leading to 
slippery travel conditions across parts of northern Michigan. More 
accumulating snow possible late Tuesday - Tuesday night.
Pattern Synopsis: Broad/low amplitude troughing across much of the 
CONUS will continue to dominate the upper level pattern through the 
middle of the upcoming week while ridging continues to build along 
the West Coast. By early Monday morning, a shortwave trough axis is 
expected to be draped from near Hudson Bay southeastward through the 
upper Mississippi Valley...expected to race eastward through the 
day. Attendant developing surface reflection is expected to track 
right across northern lower Michigan accompanied by an area of snow 
across the region. High pressure gradually noses into the area late 
Monday through early Tuesday, ultimately bringing much drier air to 
the region before another clipper system (similar to Monday's in 
many ways) pivots southeastward out of Canada into the northern 
lakes Tuesday night into Wednesday...once again increasing snow 
chances across the forecast area.
Primary Forecast Concerns/Challenges: PoPs and snow amounts through 
the forecast period.
Early Monday, focus revolves around the aforementioned incoming 
shortwave and developing area of low pressure across the northern 
Great Lakes. Ongoing snow is expected across much of eastern upper 
and the Tip of the Mitt before gradually spreading further south and 
east toward the M-72 corridor by the late morning/midday hours and 
further southeast toward Saginaw Bay during the afternoon. Morning 
snow could be locally lake enhanced off of Lake Michigan, primarily 
across the Tip of the Mitt, including portions of Emmet, Cheboygan 
and Charlevoix counties (and perhaps the northern half of Leelanau) 
given west-southwest boundary layer flow across a sufficient 
delta T environment, deep moisture extending through the column, 
inversion heights rising to near 9 kft aided by increasing 
synoptic support, and omega pegged in 5-6 kft deep DGZ. Current 
expectation is for an additional 2-4" in parts of the 
aforementioned counties (locally higher) during the day Monday, on
top of what falls late tonight (discussed above in the near term 
section). In coordination with the near term forecaster, have 
opted to issue a Winter Weather Advisory for the Tip of the Mitt 
for storm total snowfall of 3-6" (locally higher) late tonight 
through Monday. Lesser accumulations elsewhere on Monday... 
generally 1-3" across the remainder of the northwest lower from 
the Lake MI shoreline to the I-75 corridor north of M-72 (though 
will have to watch for lake enhancement elsewhere)... tapering to 
an inch or less east of I-75/south of M-72.
Synoptically aided snowfall expected to exit the forecast area by 
late Monday afternoon/evening as arriving surface high pressure 
ushers in much drier air behind the departing system. Given plenty 
of lake induced instability remaining, scattered snow showers may 
continue downwind of Lake Michigan and Superior...primarily for 
north-northwest flow locales in far western Chip/Mack and across the 
GTV Bay region west of US-131. Minimal accumulation expected Monday 
night-Tuesday morning given a significant loss of moisture and 
inversion heights falling to sub 3 kft.
During the day Tuesday, winds gradually back westerly and eventually 
west-southwesterly in advance of the next approaching clipper 
system. This will transition any lingering light lake effect snow 
showers toward the M-32 corridor and eventually the Tip of the 
Mitt before the system aids in spreading another round of snow 
across the region late Tuesday into Wednesday morning. Lake 
enhancement downwind of the big waters is certainly a possibility 
once again with advisory level accumulations not out of the 
question in those areas that see enhancement. Something to monitor
as we head through an increasingly busy holiday travel week. 
Temperatures remaining below normal through the forecast period with 
highs ranging from the mid 20s to low 30s across the forecast 
area...coldest on Tuesday as many areas struggle to reach the upper 
20s. Overnight lows certainly chilly as well with the coldest 
temps expected Monday night...ranging from teens across many areas
to the low 20s in northwest lower collar counties of Lake 
.LONG TERM...(Wednesday night through Sunday)
Issued at 310 PM EST Sun Nov 18 2018
High Impact Weather Potential: Minimal.
Warm air advection expected to be underway Wednesday night into 
Thursday leading to a gradual boost in temperatures beyond the 
Thanksgiving holiday into next weekend (perhaps even some rain 
towards the Friday night-Saturday time frame). The moderating 
temps don't look to last long as long-range guidance hints at 
troughing returning to the Great Lakes by late next weekend into 
the start of the following week.
.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 115 PM EST Sun Nov 18 2018
VFR conditions have returned to the terminal sites and most of
northern lower Michigan. That will remain the case through the
rest of the afternoon. Tonight, cold front will sag into northern
Michigan from the north while another wave presses out of Canada
into the region on Monday. Lake enhanced snow showers are expected
to ramp up again overnight over northern Lake Michigan in advance
of these features targeting some heavier snow showers into the tip
of the mitt and the PLN terminal site. Lighter snows overspread
the rest of northern lower Michigan and terminal sites on Monday
bringing a return to MVFR flight conditions.
Issued at 310 PM EST Sun Nov 18 2018
Gusty W/SW winds out there today will begin to diminish tonight
and into Monday. Will keep going small craft advisories as is,
with some headlines dropping off early this evening and rest by
midnight. Winds turn into the north on Monday with another period
of gusty winds later Monday into Monday night. Another round of
small craft advisories may be needed at that time.
MI...WINTER WEATHER ADVISORY from 4 AM to 7 PM EST Monday for MIZ016-
LH...SMALL CRAFT ADVISORY until 7 PM EST this evening for LHZ345-346.
     SMALL CRAFT ADVISORY until midnight EST tonight for LHZ347-348.
LM...SMALL CRAFT ADVISORY until 7 PM EST this evening for LMZ341.
     SMALL CRAFT ADVISORY until midnight EST tonight for LMZ323-342-
LS...SMALL CRAFT ADVISORY until 7 PM EST this evening for LSZ321-322.