Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 150445
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
1145 PM EST Sun Jan 14 2018

.UPDATE...
Issued at 1009 PM EST Sun Jan 14 2018

Low pressure is centered over Minnesota and Iowa late this evening
with the associated cold front trailing to the west over Nebraska
and Wyoming. Widespread mainly light snow continues to develop
over Wisconsin and Illinois ahead of this system...with a few
light returns now showing up on KAPX base ref over the past hour.
Southerly flow lake effect snow band swept thru Western Mackinac
county this afternoon and earlier this evening...and appears to
have moved well west of Mackinac county per upstream radars.
Synoptic snow will continue to gradually develop eastward into our
CWa overnight into Monday morning...becoming lake enhanced over
far Eastern Chippewa and Mackinac counties as low level flow
shifts to a more SE trajectory off of Lake Huron. New snow
overnight will be minor...generally under an inch.

&&

.NEAR TERM...(Tonight through Monday)
Issued at 327 PM EST Sun Jan 14 2018

...Lake effect/enhanced snow through Monday...

High Impact Weather Potential...Heavier snowfall and reduced
visibilities for a few areas.

Pattern Synopsis/Forecast...Surface analysis/satellite imagery
reveals elongated surface ridge axis stretching from the Gulf of
Mexico up through the eastern Great Lakes into New England.
Upstream deepening short wave trough is dipping down through the
Manitoba/Ontario region with an associated surface low just
crossing the U.S./Canadian border into northern Minnesota. Short
wave (and attending surface low) will close off while slipping
down into the upper Midwest tonight before pivoting through the
western Great Lakes Monday and Monday night.

Certainly a decent looking/wound up system with a nice pulse of
mid level warm advection forcing out ahead that slides through
the region overnight...followed by a respectable deformation axis
that pivots across the upper Midwest/western Great Lakes through
the day Monday (and Monday night). Available synoptic moisture
is and will be lacking however...evidenced by the overall lack of
good radar returns upstream across the upper Midwest this
afternoon. But I still expect overall light snowfall to
overspread the region mainly overnight (will take that long to
top-down saturate things) and persist through the day Monday with
most areas picking up an inch or two of accumulation.

Primary forecast concerns rests with lake enhanced snow potential.
We already have some decent lake banding in northern Lake Michigan
that has been migrating westward through the western half of
Mackinac county this afternoon. Beaver Island observation briefly
dipped to 1/4SM as the main snow band moved through. Introduction
of synoptic forcing/moisture will only help with lake effect
intensities as we get into tonight. But...low level mean flow also
continues to back SE tonight and eventually easterly on Monday.
This will push the heavier snow bands into Schoolcraft county for
tonight where MQT office already has an advisory posted. So...no
advisory planned from this office although we have been issuing
SPSs to highlight periods of lowered VSBYs.

Lake Huron lake enhanced snow showers become a problem for Monday
as winds gradually back east...dragging northern Lake Huron lake
snows across the E/SE parts of Chippewa/Mackinac counties and
eventually into the NE lower Michigan shoreline area. Several
inches of snow are possible in those areas especially tomorrow
afternoon/evening. Don`t think we will see warning criteria
accumulations however. So I plan to leave the headline decisions
(if any) to the midnight crew.

&&

.SHORT TERM...(Monday night through Wednesday)
Issued at 327 PM EST Sun Jan 14 2018

...East Side Lake Effect Monday night...

High Impact Weather Potential...Moderate to heavy snow amounts
possible in NE Lower Monday night.

Pattern Synopsis/Forecast...500 mb low moves across the state
between 00z/Tue and 00z/Wed. This moves the sfc low through S Lower
and into SW Ontario by 00z/Wed as well. Models show F-gen signal in
N Lower north of the 500 mb low center Monday night into Tuesday
morning. 850 mb temperatures are around -15c the whole time, and
with the RH at 850 mb around 90%, and the in the 700-500 mb level
around 80%, will expect that there will be good flake growth through
the overnight and early morning. As the sfc low moves into SW
Ontario during the day on Tuesday, the wind switch to NNE to N flow
over the forecast area, and a dry tongue extends down from CYAM and
into N Lower. Eventually, the moisture moves a little east, allowing
the moisture on the backside of the system to increase along the N
flow LES regions of the NW Lower. Winds continue to back to the NNW
and then NW through the day on Tuesday, and into Tuesday night, so
that any N or NNW snow bands get pushed into NW Lower by 06z as the
winds go to the WNW and then W by 09z. By 12z/Wed, the 850 mb
temperatures begin to warm lower the instability over lake Michigan,
not to mention the limited fetch as Green Bay is ice covered.
18z/Wed, a 500mb speed max looks to try and kick off some snow
showers over E Upper, especially the ECMWF, but with the dry air
front 850 mb, and lower, not to mention the extremely dry air (850
mb RH<20%) will expect the snow showers  will come to a halt by the
early afternoon, if not sooner.

Primary Forecast concerns...the SE winds will be the main concern
with Monday night. With the 850 mb temperatures around -15c, we are
in the good temperatures for the dendritic growth, and the water
temperatures around 2-3c the instability is good. The moisture is
also good, with 850-700 mb layer RH>80%. The main factor becomes the
wind directions. The models, show that initially, the bands will
continue from Monday afternoon, and go into the evening (03z),
before backing quickly from the SE to the NNE by 12z This would
spread the snow around NE Lower, with some decent bands near APN and
OSC. After that, the snow begins to diminish as the moisture wanes
and then winds continue to back to the West, and we begin to lose
the LES components. More likely we will have moderate to heavy
amounts Monday into Monday night than Monday night into Tuesday.

.LONG TERM...(Wednesday night through Sunday)
Issued at 144 PM EST Sun Jan 14 2018

High Impact Weather Potential...

High pressure across most of the eastern CONUS will bring moderating
temperatures through the extended. Quiet weather is expected through
much of the period, with the next widespread precipitation chances
tied to a system moving out of the southern Plains. There is a good
bit of uncertainty with this, especially in the timing. Guidance
divergence in the track isn`t quite as substantial as the timing,
but could be the difference between seeing all snow, or some rain as
well. This will be something to keep an eye on over the next few
days.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1145 PM EST Sun Jan 14 2018

VFR/high MVFR conditions will deteriorate to mainly IFR conditions
overnight and Monday as widespread synoptic snow develops ahead of
low pressure moving into the Western Great Lakes region. Southerly
winds will shift to the SE and eventually to the east...providing
lake enhancement to ongoing synoptic snow across portions of NE
Lower Michigan (APN)...especially Monday into Monday night. Wind
speeds will generally be around 10 kts...with some gusts to 20
kts expected mainly in NE Lower Michigan (APN).

&&

.MARINE...
Issued at 327 PM EST Sun Jan 14 2018

Gusty southerly winds will back southeast tonight and east on
Monday. This will lead to small craft advisory conditions on Lake
Michigan through at least Monday before winds diminish Monday
night into Tuesday.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...NONE.
LM...SMALL CRAFT ADVISORY until 6 AM EST Tuesday for LMZ323-341-342-
     344>346.
LS...NONE.
&&

$$

UPDATE...MR
NEAR TERM...BA
SHORT TERM...JL
LONG TERM...AM
AVIATION...MR
MARINE...BA



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