Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 140803

Area Forecast Discussion
National Weather Service Gaylord MI
403 AM EDT Sat Apr 14 2018

.NEAR TERM...(Today through Tonight)
Issued at 403 AM EDT Sat Apr 14 2018

...Strong and prolonged winter storm continues to evolve...

High Impact Weather Potential...Mainly heavy wet snow today will
transition to mixed precip tonight along and south of M-32.
Significant accumulations of heavy wet snow and ice causing very
hazardous travel.

Pattern Synopsis/Forecast...Complex area of low pressure continues
to develop upstream of the Great Lakes and is now centered over
Northern Missouri and Iowa. Associated stationary front extends from
the surface low center eastward thru Northern Illinois to just south
of the Great Lakes region. Rather large precip shield continues to
develop north of this front...ranging from showers and thunderstorms
to mixed precip to all snow within this shield of precip. Latest
lightning detection shows a significant decrease in lightning
activity within the showers and storms just to the NE of the surface
low center as the larger area of strong to severe convection over
Missouri and Central Illinois just ahead of the associated cold
front begins to steal some of the available energy and moisture.

Closer to home...northern edge of the precip shield has pushed
slightly further reaching the Straits with little to no
precip occurring north of the Bridge. Most of the Upper Peninsula
remains high and dry attm thanks to a large area of strong high
pressure and associated dry air centered over Central Canada pushing
southward against the developing low. The battle between these two
strong systems is resulting in a tightening of the temp gradient
over our CWA...resulting in further enhancement of 700-500 mb F-gen
over our CWA as well as upstream well north of the stationary front.
Elongated area of precip within this enhanced F-gen has filled in
and become better organized as a result...the axis of which has
become focused across Northern Lower Michigan north of a line from
MBL to GOV to APN.

As we head thru the morning hours...colder/drier air across Eastern
Upper Michigan will gradually press further south into Northern
Lower Michigan. Axis of max F-gen will gradually push south thru the
rest of Northern Lower Michigan...shifting focus of max QPF
southward as well. Precip is in the process of switching to all snow
from north to south early this morning thanks to CAA from the north.
Surface temps have responded with most locations showing at least a
couple of degrees drop in temp since midnight or so. Certainly the
heavy wet nature of the snow has and will continue to diminish
potential accumulation amounts. Expect a general 3 to 6 inches of
new snowfall early this morning thru today. But hazards associated
with heavy wet snow as well as any lingering mixed precip across our
southern CWA early this morning will easily warrant the continuation
of ongoing Winter Storm Warnings. Also...NE winds will strengthen
today...with gusts of 25 to 35 mph causing blowing snow and further
reducing vsbys. Will upgrade the Winter Wx Advisory for the tip of
the Mitt to a Warning to cover snow this morning and then our next
major wave of snow arriving tonight as the surface low begins to
lift thru Michigan. In coordination with MQT...will also upgrade
the Winter Storm Watch for Eastern Upper Michigan to a
Warning...but will delay the start until 06Z based on latest short
term models trends regarding the arrival of our next major wave
of precip.


.SHORT TERM...(Sunday through Monday)
Issued at 403 AM EDT Sat Apr 14 2018

...And Now the Snow and Ice...

High Impact Weather Potential...The heavy snow for E Upper will
start and continue through Sunday and Sunday night with 8-10 inches
expected in the 24 hrs between 06z/Sun and 06z/Mon. At the same
time, along and south of M-72 we get 0.25" to 0.60" through the 24
hrs between 00z/Sun and 00z/Mon. Then there is another 0.10" around
most of N Michigan Sunday night and Monday. So it`s going to be
messy this weekend.

Pattern Synopsis/Forecast...Sunday morning, the sfc low is on the
IN/OH then moves/morphs to the NE so that a new center moves through
S Lower by Sunday evening. At the same time, the Upper level low
moves into the Upper Great Lakes, and pulls dry air into the region.
The warm air aloft gets pulled into the N lower, but the cold air
from the sfc high over Hudson Bay pushes in. It`s this set up that
produces the snow in the north and the freezing rain in the south.
The low then slows and moves into Lake Huron by Monday morning. Then
it stays near Lake Huron through the day on Monday. As the 500 mb
low moves over Michigan, we continue to get dry air aloft, so the
snow looks like it will go over to freezing drizzle on Monday and
Monday night.

Primary Forecast Concerns...The sfc low track looks consistent over
the last couple of runs, and between the GFS and ECMWF. The issue
that causes concern is the possibility of thunderstorms south of the
warm front that could potentially rob the moisture and heat from the
frontal processes or add to them. The models hint at lines of
thunderstorms that will move east south of Michigan, but what the
orientation south of the front will look like and the affect it will
have on the precipitation is up for grabs. A case in point, while we
have a few good bands over N lower at the moment, some of the radar
returns have fallen apart, as the showers and thunderstorms
developed and moved into Illinois/Indiana and S lower over the past
few hours. So this will continue to be the case through the day
today and into Sunday. Monday, once the cold front moves through
then the issue becomes the dry air aloft and evolves into LES.


.LONG TERM...(Monday night through Friday)
Issued at 403 AM EDT Sat Apr 14 2018

The snow will diminish on
Tuesday as the lows move out of the Upper Great Lakes. Wednesday
could be dry if the ECMWF is right, but the GFS shows some snow/rain
as the next system moves into the region. Thursday and Friday,
primarily look dry over the region as high pressure briefly takes
over before the next system which could arrive by the weekend on the
ECMWF. It takes a little longer to dry out on the GFS which has a
deeper 500 mb low that takes its time to move on.


.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1155 PM EDT Fri Apr 13 2018

Challenging forecast continues as passing areas of rain and snow,
with embedded enhanced convection briefly changing precip to heavy
snow, continuing across the southern taf locations through
early this afternoon. Still appears KPLN will be just north of
the heaviest snow shield. Lower cigs will be more widespread, once
again south of KPLN. Snowfall will be heaviest across KAPN, with
several inches of wet, heavy snow likely by later this morning.
Rain/snow mix will temper accumulations for KTVC and KMBL. Snow is
expected to end this afternoon, with dry air also helping scatter
out the low overcast. Next round of mixed precipitation and lower
cigs arrives from south to north Saturday night and Sunday.
Increasingly gusty northeast winds through the period.


Issued at 403 AM EDT Sat Apr 14 2018

Deep low pressure will slowly lift NE out of the Mississippi Valley
and thru Michigan over the weekend and into early next week. As a
result...winds and waves will continue to reach SCA and gale warning
criteria thru Sunday. This system will also produce several waves of
mixed precip which will likely result in significant accumulations
of snow and ice.


MI...WINTER STORM WARNING until 5 PM EDT Sunday for MIZ020>036-041-
     WINTER STORM WARNING from 2 AM Sunday to 2 AM EDT Monday for
     WINTER STORM WARNING until 2 AM EDT Monday for MIZ016>019.
LH...SMALL CRAFT ADVISORY until 8 PM EDT Sunday for LHZ345-346.
     GALE WARNING until 8 PM EDT Sunday for LHZ347>349.
LM...SMALL CRAFT ADVISORY until 8 PM EDT Sunday for LMZ341.
     GALE WARNING until 8 PM EDT Sunday for LMZ323-342-344>346.
LS...SMALL CRAFT ADVISORY until 8 PM EDT Sunday for LSZ321-322.


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