Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 161803
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
203 PM EDT Mon Apr 16 2018

.UPDATE...
Issued at 1046 AM EDT Mon Apr 16 2018

Large area of mostly light to moderate snow continues to slowly
pinwheel northwest as deep upper level pressure passes overhead.
Most persistent snow should focus into northwest lower and
eastern upper Michigan this afternoon and evening where low level
convergence becomes maximized and marginal lake enhancement
begins. Added a tier of counties further south into the advisory
area to account for some low visibilities and accumulating snow.
These should be allowed to expire shortly as best snows pivot
further north. Otherwise, at least for now, inherited headlines
will remain, waiting for full guidance suite and relocation of
better snows to determine future headline decisions.

UPDATE Issued at 406 AM EDT Mon Apr 16 2018

One omission from the original discussion: APN/Rogers both
reporting light rain/fzra presently. Nam Bufr data switches that
back to snow by 7 am, with a brief intervening period of sleet.

&&

.NEAR TERM...(Today through Tonight)
Issued at 336 AM EDT Mon Apr 16 2018

...Winter not done yet...

Triple-point low over western VA is now the dominant surface low. A
sharp inverted trof extends up toward the southern tip of Lk Huron,
and a weak surface wave is present near Lapeer MI. High pressure is
anchored over ne Canada. A closed 500mb low will pass just south of
lower MI today. However, a shortwave will pinwheel back into the
northern lakes as this happens, and this will close off directly
over our heads this evening. This will help maintain an easterly
feed of moisture into the region, and give us some dynamics to act
on that moisture. In addition, 850mb temps of -13/-14C may allow a
lake response to develop. The end result is another pretty typical
mid-winter forecast.

Plume of deep moisture, now just grazing parts of ne lower and
eastern upper MI, will gradually get drawn back westward this
morning. Radar has already lit up substantially since midnight
with convective echoes over central/eastern areas. Expect precip
rates to increase again toward daybreak for APN/Rogers and on up
into far eastern upper MI. 500mb heights will sharply lower this
morning, and a weak surface low reflection will lift ne-ward
across Lk Huron. In response, snowfall rates in the areas
mentioned above will be legit heavy at times in the daylight
morning hours. Expect 2-4" of accums this morning/midday, along
and north of a CVX-GLR-Black River line.

This afternoon, a subtle mid-level dry slot will form in ne portions
of the forecast area, as a closed 500mb circulation emerges over the
Straits area. A rain/snow mix will enter the equation from Gladwin
to Harrisville and points south. Meanwhile, moisture will wrap back
into nw lower MI, along with the colder 850mb temps mentioned above.
Forcing is less than this morning, but it`s getting cold enough for
Lake MI to help out. The above plays out thru tonight, though the
850mb thermal trof does start to ease southward late in the
overnight. Inversion heights settle in at 800mb, 5.0-5.5k ft. NW to
borderline WNW flow, when combined with lingering ice cover over the
ne tip of Lake MI, will focus better lake enhanced snow from midday
today into tonight in the Gd Trav Bay region. Afternoon accums of 1-
2" in nw lower, far n central lower, and eastern upper. That segues
to 2-4" tonight in much of nw lower MI, with lesser amounts
elsewhere.

Ongoing winter storm warnings are fine, except for Leelanau, which
won`t get caught up in the early morning activity very much. They do
get involved by late morning and beyond as lake enhancement kicks
in. Will cancel the Leelanau warning, but will put them, Benzie, Gd
Traverse, and Kalkaska in an advisory that kicks in later this
morning and goes thru late tonight.

Lots of clouds. Max temps low-mid 30s. Min temps mid-upper 20s.

&&

.SHORT TERM...(Tuesday through Wednesday)
Issued at 336 AM EDT Mon Apr 16 2018

...Moderating Temperatures...

High Impact Weather Potential...Minimal as the snow diminishes and
we get some light rain.

Pattern Synopsis/Forecast...The models show the lake effect snow
should diminish as the 850 mb temperatures warm t around -6c or so
by 00z/Wed, and that the 700-500 mb layer rh begins to dry out
allowing for some <50% RH air in the layer. This leads to a
temporary reprieve of the last few days, with Tuesday night into
Wednesday morning being dry. However, an Alberta clipper system
drops through the Northern Plains and brings some WAA snow and
rain/freezing rain Wednesday afternoon and into Wednesday night. The
sfc low moves into New England by 12z/Thu and the dry air in the 700-
500 mb layer returns into the Upper Great Lakes.

Primary Forecast Concerns...Not sure I buy the blends idea of
freezing rain for Wednesday night. Maybe we get patchy drizzle and
temperatures cool to just below freezing so that we get some
freezing drizzle. The ECMWF soundings for Wednesday night are pretty
dry and the QPF is very low. The NAM and the GFS both really push
some sort of rain/drizzle with the sfc temperatures around 32F. so
will have to watch this. The impacts at most would be a slippery
morning commute on Thursday, but nothing that would raise a
headline. I`m willing to go out on a limb and side with the ECMWF of
little to nothing for the Wednesday night. We`ll have to see how
strong the Hudson Bay high is and whether it can push some low level
dry air to keep the warm front from producing much.

.LONG TERM...(Wednesday night through Sunday)
Issued at 336 AM EDT Mon Apr 16 2018

...Becoming precip-free with Moderating Temperatures...

Extended (Thursday through Sunday)...The models dry things out
through the weekend, as High pressure builds into the Upper Great
Lakes at the sfc and aloft. Lots of dry air pushes into the region
as a result and the 500 mb heights begin to build. This pushes our
temperatures up from the lower 40s on Thursday to the lower 50s on
Sunday. It would be surprising if, with the sunshine that one would
expect with this pattern that we could get back to the normal high
temperatures for this time of year which are the mid to upper 50s.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 201 PM EDT Mon Apr 16 2018

More of the same with MVFR to IFR conditions expected under
passing snow showers and low cigs. Visibility will be reduced,
especially through early this evening before snow becomes more
scattered. A few inches of new snow is expected, especially at
KPLN and KTVC. Gusty northwest winds will develop, lasting right
through Tuesday morning.

&&

.MARINE...
Issued at 336 AM EDT Mon Apr 16 2018

Blustery ne winds will continue to back to the n and nw, while
remaining gusty. Advisories will likely be extended for a lengthy
period, perhaps into Tuesday.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...WINTER WEATHER ADVISORY until 5 AM EDT Tuesday for MIZ020-
     025>027.
     WINTER STORM WARNING until 8 PM EDT this evening for MIZ008-
     015>019-021>024.
LH...SMALL CRAFT ADVISORY until 5 PM EDT Tuesday for LHZ345>349.
LM...SMALL CRAFT ADVISORY until 5 PM EDT Tuesday for LMZ323-341-342-
     344>346.
LS...SMALL CRAFT ADVISORY until 5 PM EDT Tuesday for LSZ321-322.
&&

$$

UPDATE...MB
NEAR TERM...JZ
SHORT TERM...JL
LONG TERM...JL
AVIATION...MB
MARINE...JZ



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