Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 131637
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
1237 PM EDT Fri Apr 13 2018

.UPDATE...
Issued at 1231 PM EDT Fri Apr 13 2018

Widespread rain is beginning to enter from the west and even
producing a bit of thunder. With 3-6km lapse rates in excess of
7C/km and MUCAPE 300-600 J/kg, elevated thunderstorms are
developing ahead of the approaching warm front. SPC has also went
farther north with they Day 1 forecast with south of a line from
TVC to about OSC in general thunder. Forecast soundings appear to
have the threat of thunderstorms ending by 05Z. Continuing to fine
tune the afternoon forecast for timing, p-type, and accumulations.

&&

.NEAR TERM...(Today through Tonight)
Issued at 355 AM EDT Fri Apr 13 2018

...Strong and prolonged winter storm begins today and tonight...

High Impact Weather Potential...Periods of mixed precip today and
especially tonight. Significant accumulations of heavy wet snow and
ice causing very hazardous travel.

Pattern Synopsis/Forecast...Complex area of low pressure continues
to develop over the Plains early this morning...with an associated
stationary front extending eastward from the low thru Northern
Missouri to just south of the Great Lakes region. Line of showers
has begun to develop north of this boundary in response to
strengthening 700-500 mb F-gen and isentropic ascent as well as
rapidly deepening moisture as southerly flow ahead of this system
begins to tap into gulf moisture. Closer to home...dry conditions
persist under mainly cloudy skies with temps holding mainly in the
30s.

As we head into today and tonight...elongated area of precip will
steadily expand along and north of the warm front as the deepening
surface low edges eastward into Iowa and Missouri by this evening.
Meanwhile...strong surface high pressure parked over Northern
Ontario and the associated dry air and subsidence will press
southward into Upper Michigan. The result will be a tightening of
the thermal gradient right over Michigan between these two systems.
This will certainly further enhanced lift...and will also make for a
rather difficult precip type forecast across our CWA.

Still appears we will see a brief period of a light mix of precip
during the onset this morning across Northern Lower Michigan...with
mixed light rain and snow persisting much of the day across Eastern
Upper Michigan. All precip should switch over to all rain by around
midday across Northern Lower Michigan...and should remain all liquid
thru the afternoon and into early evening. Expect little to no snow
or ice accumulation during the morning across Northern Lower
Michigan as temps warm thru the 30s to a few degrees either side of
40 in most locations for afternoon highs. The light mix of rain and
snow expected across Eastern Upper Michigan will also have a
difficult time resulting in any accumulation as temps warm thru the
30s.

The strong subsidence and dry air to the north will press further
south tonight...greatly diminishing POPs and the potential for
significant snow accumulation across Eastern Upper Michigan. At this
point...expect Eastern Upper Michigan will only see an inch or two
of new snow tonight with no mixed precip expected. In coordination
with MQT...have opted to delay the Winter Storm Warning and push
back the start time for this headline to 00Z Sunday considering now
significant snow accumulation is expected until then. Still appears
deep moisture and strong lift will likely produce several inches of
heavy wet snow as well as significant ice accumulations across much
of Northern Lower Michigan tonight. There is still quite a bit of
uncertainty and variance among the models as to timing...duration
and amount of the various precip types. In coordination with GRR and
DTX...have decided to maintain the Winter Storm Watch across all of
Northern Lower Michigan with a few hours delay in the start of the
Watch for far Northern Lower Michigan.

&&

.SHORT TERM...(Saturday through Sunday)
Issued at 355 AM EDT Fri Apr 13 2018

...Heavy Snow to the North, Heavy Ice to the South...

High Impact Weather Potential...A prolonged event with potentially
heavy snow in the north and major icing conditions in the south. If
the ice accumulation is right, based on the low level cold air and
the rain, over M-55, then major icing is possible on trees and power
lines.

Pattern Synopsis/Forecast...The main low pressure moves out of SW
Iowa and into the Mid-Mississippi Valley by the afternoon. This
pushes the warm air over the stalled front in Lower Michigan. The
warm air nose just below 700 mb is between 1-3c  and with the sfc
temperatures in the mid to upper 20s overnight in N Lower south of M-
72, will expect that ice and sleet will be possible through the
night. With the sfc low continuing to stall/split in N Indiana, and
the sfc high over Hudson Bay, the undercutting cold air will
continue to push south, and the warm air riding up the front will
continue to make in roads north over N Lower. So the cold air will
be able to offset the rain north of M-32 so that it`s all snow, with
a mix between M-32 and M-72, and then south of M-72 freezing
rain/sleet, with the heaviest freezing rain along M-55 where the
models are spitting out 0.25"+ ice accumulations. The 500 mb low
begins to finally move to the east and into the Upper Great Lakes by
09z/Monday. This allows some dry slotting and lowers the amounts as
the precipitation becomes more showery.

Primary Forecast Concerns...The ice accumulations will be
problematic as the models are pushing the amounts south to around M-
55. Models and forecast tools show 0.50"+ amounts possible in the
south east counties. This probably the high end, with the more
likely amounts begin 0.25"+ more likely as the models and tools tend
to over do things. However, it`s not out of the realm of
possibilities, so will continue with that in the forecast for now.

.LONG TERM...(Sunday night through Thursday)
Issued at 355 AM EDT Fri Apr 13 2018

Freezing rain/drizzle/ and rain
will continue Monday as the the 500 mb low moves over the region and
mid level dry air gets ingested, producing the drizzle over the
region. Eventually by 00z/Tue the dry air is gone, and with all the
temperatures in the column below freezing will expect light snow as
we begin to diminish the snow overnight. Turning into Lake Effect
snow on Tuesday, and may be rain by the afternoon. Models dry things
out Tuesday night, only to bring in the next system Wednesday
afternoon as rain moves in, then a mix of rain and snow for the
region overnight. 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.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1222 PM EDT Fri Apr 13 2018

Conditions will gradually deteriorate to MVFR and eventually IFR
as widespread rain develops north of a warm front. There is also a
possibility of thunderstorms south of a line including TVC to
OSC. This precip will transition to mixed precip from north to
south tonight as colder low level air pushes into the
region...including the possibility of freezing rain. NE winds 10
to 20 kts with some higher gusts today will further strengthen
tonight to 20 to 30 kts with higher gusts possible.


&&

.MARINE...
Issued at 355 AM EDT Fri Apr 13 2018

Deep low pressure will slowly lift NE out of the Central Plains and
thru Michigan over the weekend and into early next week. As a
result...winds and waves will strengthen to SCA and gale warning
criteria by late this afternoon and tonight...and will continue to
reach criteria thru Sunday (at least). This system will also produce
several waves of mixed precip which will likely result in significant
accumulations of snow and ice.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...WINTER STORM WATCH from late tonight through Sunday afternoon
     for MIZ020-025>036-041-042.
     WINTER STORM WATCH from 8 PM EDT this evening through Sunday
     afternoon for MIZ016>019-021>024.
     WINTER STORM WATCH from Saturday evening through late Sunday
     night for MIZ008-015.
LH...SMALL CRAFT ADVISORY from 11 PM this evening to 8 PM EDT Sunday
     for LHZ345-346.
     GALE WARNING from 2 AM Saturday to 8 PM EDT Sunday for
     LHZ347>349.
LM...SMALL CRAFT ADVISORY from 11 PM this evening to 8 PM EDT Sunday
     for LMZ341.
     GALE WARNING from 5 PM this afternoon to 8 PM EDT Sunday for
     LMZ323-342-344>346.
LS...SMALL CRAFT ADVISORY from 11 PM this evening to 8 PM EDT Sunday
     for LSZ321-322.
&&

$$

UPDATE...TL
NEAR TERM...MR
SHORT TERM...JL
LONG TERM...JL
AVIATION...TL
MARINE...MR



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