Area Forecast Discussion
Issued by NWS Gaylord, MI

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000
FXUS63 KAPX 160249
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
949 PM EST Wed Nov 15 2017

.UPDATE...
Issued at 949 PM EST Wed Nov 15 2017

999mb surface low just ne of Drummond Isl. Initial cold front has
crossed northern MI, though cold advection is presently
unimpressive. Secondary cold front is pushing south into upper MI,
and much cooler air is found behind that boundary. That airmass
will arrive in northern MI overnight.

Dry slotting is about to exit ne lower MI, with wraparound
moisture across nw/n central lower MI and eastern upper. Moisture
will be in no hurry to depart overnight (though far sw sections
will remain on the outer edge of the wraparound plume). The
arrival of colder air and sharply increased overlake instability
will result in precip becoming more convective with time,
especially after 2 am.

Pops will remain high in much of northern MI overnight, though
will start to come down in areas not prone to lake effect
(especially the far se). Precip will eventually mix with and turn
to snow, though this process may take another 1-2 hours longer
than earlier planned. That will keep accums small: up to an inch
in eastern upper, less than an inch in northern lower MI.

Outside of the above adjustments, no major changes.

&&

.NEAR TERM...(Tonight through Thursday)
Issued at 321 PM EST Wed Nov 15 2017

...Widespread rain continues into the evening, then changing to snow
late tonight...

High Impact Weather Potential...Minimal

Pattern Synopsis/Forecast...Low pressure is centered over central
Lake Superior this afternoon, with the associated cold front
extending through the western U.P., Wisconsin, and down to northern
Missouri. Rain ahead of this cold front has produced around 0.50 to
1.00 inches over most of northern Michigan...with areas east of I-75
over northern lower receiving the highest amounts so far. Some snow
did mix in with the rain over the higher terrain of northern lower
Michigan for a few hours, but no accumulations due to the above
freezing temperatures. This snow began to change to all rain once
again as WAA became more prominent.

The widespread light to moderate rain will continue it`s move
northeastward and should be out of the forecast area by tonight.
Showery precipitation (in the form of rain) and drizzle will
continue until around midnight, when the colder air behind the
aforementioned cold front begins to cool the temperatures
sufficiently enough. 850mb temperatures will be near -6C, this with
lake temperatures still between 9-12C will be enough to enhance the
precipitation over northwestern lower Michigan, parts of eastern
Upper, and possibly even clipping the Rogers City/Alpena areas with
lake enhanced/effect snows. Any new snowfall amounts overnight/early
morning will only be minor. High pressure and drier air will
diminish any lingering lake effect snow/clouds late Thursday,
providing a quick break before the next system begins to impact the
forecast area.

Temperatures will remain in the upper 30s to near 40 until cold
frontal passage around midnight, when they will begin to drop to the
upper 20s/lower 30s by sunrise. Highs Thursday will only reach into
the lower 30s over eastern upper and the mid to upper 30s over
northern lower.

&&

.SHORT TERM...(Thursday night through Saturday)
Issued at 321 PM EST Wed Nov 15 2017

...Wet start to the weekend...

High Impact Weather Potential...Somewhat gusty winds Saturday
afternoon with rain transitioning to snow, but not expecting any
significant impacts.

Pattern Synopsis/Forecast...Ridging at the surface and aloft will
slide across northern Michigan Thursday night, with warm air
advection developing around daybreak Friday as the ridging shifts
east. A digging longwave trough crossing the Rockies on Friday will
give way to a couple developing surface lows...one traversing
southern Canada and another ejecting northeast from Colorado. The
northern low will drag a trailing cold front through northern
Michigan early Saturday while the southern low lifts through
southern Lower Michigan. This will bring another round of widespread
precipitation to the area, with colder air wrapping around into the
Upper Great Lakes by late Saturday afternoon as the system departs
and northwest winds increase.

Primary Forecast Concerns...Time of arrival of showers on Friday and
occasional ptype concerns.

Rapid increase in deep layer moisture through the day on Friday as
low level jet slides over northern Michigan, ramping up the warm air
advection. PWATs are progged to range from around 0.8" across
eastern Upper to near 1" down towards Saginaw Bay by Friday evening.
Isentropic lift and a warm front will lift northeast across northern
Michigan Friday morning, triggering showers just upstream initially.
That activity is expected to slowly increase in coverage as it
meanders eastward through the day. So expect eastern Upper and
perhaps Tip of the Mitt to see showers first, with the activity
progressively spreading east across the rest of northern Lower
during the afternoon. Still some subtle timing difference between
the models, so only moderate confidence right now in timing the
showers across northern Lower.

More or less steady precipitation thereafter for the entire forecast
area heading into Friday evening. Perhaps some breaks developing in
the precipitation shield towards Saturday morning as the surface low
and cold front traverse the area, but another surge of more
widespread precip is likely late morning into the afternoon as the
H5 trough approaches. Synoptic precip will transition to more of a
lake effect regime late in the afternoon as colder air builds into
the region. This will also result in somewhat gusty northwesterly
winds Saturday afternoon behind the cold front.

In terms of ptypes, generally rain for most at onset on Friday, but
there may be some snow mixed with rain across portions of eastern
Upper and interior northern Lower. Low level temperatures will
actually rise a bit Friday night under the influence of warm
advection, so this should lead to a transition to all rain. Falling
temperatures behind Saturday`s cold front will allow for a rain/snow
mix in the higher elevations, eventually transitioning to all snow
late in the day. While moderate rainfall of 0.5 to 0.75" will be
possible from this event through Saturday afternoon, only minor (if
any) snowfall accumulations are expected through this forecast
period.

.LONG TERM...(Saturday night through Wednesday)
Issued at 321 PM EST Wed Nov 15 2017

Expect a bit of a roller coaster through the extended period. Things
will get off to a cold, wintry start Sunday as cold air moves in on
the heels of departing low pressure. The tight pressure gradient and
cold advection regime will continue to bring some gusty winds
Sunday, with the cold NW flow bringing lake effect snows as well.
High pressure sliding by to our south will back winds to the SW
Monday, bringing some warm advection and shutting down the lake
effect. This will also moderate temperatures a bit early in the
week, with some areas getting back into the upper 30s which is about
normal for this time of year. That will be short lived; however, as
another cold shot comes mid-week.

Still some questions and uncertainties with expected amounts from
the lake effect on Sunday. There will be plenty of instability, and
inversion heights look respectable, but the persistence of wind
direction is still not being handled real well right now. Omega
looks to be a bit displaced from the DGZ in long term guidance right
now as well, which would keep accumulations on the lower side. Will
start to get a better idea in the coming days on how things start to
line up for accumulation potential.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 632 PM EST Wed Nov 15 2017

Lake enhanced rain and snow showers overnight. Improving Thursday.

Low pressure over eastern Superior will move east. Cooler air
returning to the region and wraparound moisture will result in
lake enhanced showers. These will be mostly rain at the Taf
sites, though will turn to snow inland. MVFR to IFR cigs thru the
night. Drier air slowly arrives on, ending precip and lifting
cigs.

Gusty w to nw winds.


&&

.MARINE...
Issued at 321 PM EST Wed Nov 15 2017

Winds and waves will continue building to Gale criteria throughout
the rest of today and especially tonight, behind the approaching
cold front associated with a low pressure system centered over
central Lake Superior and moving eastward. Drizzle and rain showers
will change over to snow behind this cold front as well. Any
lingering showers will diminish throughout the day Thursday as high
pressure and drier air will bring a quick break in the weather
before the next storm system begins to impact the nearshore waters
later Friday with more rain and snow...and possibly more
Smallcraft/Gale headlines for the weekend.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...SMALL CRAFT ADVISORY until 6 PM EST Thursday for LHZ345-346.
     GALE WARNING until 6 PM EST Thursday for LHZ347>349.
LM...GALE WARNING until noon EST Thursday for LMZ323-341-342-344>346.
LS...SMALL CRAFT ADVISORY until 6 PM EST Thursday for LSZ322.
     GALE WARNING until 6 PM EST Thursday for LSZ321.
&&

$$

UPDATE...JZ
NEAR TERM...TL
SHORT TERM...MK
LONG TERM...AM
AVIATION...JZ
MARINE...TL



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