Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 220904
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
404 AM EST Thu Feb 22 2018

.UPDATE...
Issued at 404 AM EST Thu Feb 22 2018

Quick update on hydro issues across the southern counties. Rifle
River gauge near Sterling remains in flood territory and
projected to do so through Friday afternoon. River flood warning
will obviously continue there. Tobacco River gauge at Beaverton
has dipped below flood stage. However...readings in the last few
hours have bumped back up a bit suggesting there might be ice
jamming issues developing. Thus...I`m reluctant to cancel the
river flood warning just yet.

Otherwise...ongoing areal flood warning remains in effect through
this afternoon which is fine. Considered trimming out Ogemaw and
Iosco counties since I have not heard of any flood issues across
those counties. But...prudent move is to allow day crew to make
some calls to those areas and find out. So...will leave everything
intact for now.

&&

.NEAR TERM...(Today through Tonight)
Issued at 332 AM EST Thu Feb 22 2018

...Another round of light icing late tonight into Friday...

High Impact Weather Potential...Light ice accumulation across
parts of northern lower Michigan toward Friday morning`s commute.

Pattern Synopsis/Forecast...Trough/ridge pattern remains across
the CONUS with impressive ridging/record breaking warmth along the
SE Atlantic coast...anchored by a 596 DM 500 MB high off the
coast. Deep southwest flow and tight baroclinic zone also remains
stretched from the SW CONUS up across the Great Lakes and an associated
upper jet core riding over top the northern lakes region. Notable
short wave feature is rounding the four corners region and will
bring some impactful weather to northern Michigan to end the work
week. Proximity to the tight baroclinic zone/thermal gradient will
present addition P-type issues over the next several days.

Primary Forecast Concerns...Mixed precip and light icing
potential late overnight through Friday.

Surface high pressure currently centered in the western Great
Lakes will slide eastward through the region through the course
of the day. Return flow low-mid level warm advection forcing is
already underway across Kansas/Nebraska/Iowa producing a notable
batch of mid cloud cover and elevated radar returns pushing
northeastward across Iowa. Pocket of warm advection forcing and
cloud cover will pivot up through northern Michigan through the
course of the day into the evening leading to partly-mostly cloudy
skies overall. However...per forecast soundings and despite the
upstream radar returns...I don`t think we see much in the way of
any precip...given a layer of fairly dry low-mid level air that
hangs on through the afternoon and evening. Will likely see mid
level returns press into the region...but plan to keep the
forecast dry through this evening.

Gets a bit more "interesting" overnight. Aforementioned short
wave over the 4-corners region ejects northeastward with some
semblance of a closed lower level circulation/surface low lifting
into the upper Midwest overnight and across the northern lakes
region on Friday. Another round of strong warm advection
forcing...aided by upper jet entrance region forcing...will bring
precip expanding up into northern Michigan during the overnight
period...especially after 09Z or so. Not nearly as moist (or long
lived) as our recent system...although PW values do briefly top
0.8" which isn`t bad for this time of year. Model ensemble
guidance is tightly clustered between 0.15" and 0.25" total QPF
with this system with the greatest amount through the U.P. where
strongest QG-forcing for ascent is projected to track.

Bigger question and forecast concern...what will that precip be.
Surface temps across the CWA through the overnight hours pretty
much all projected to remain below freezing as light precip
expands into the region and warm nose aloft (Tw > 0C) advects up
through all of northern lower Michigan by morning. This suggests
light precip will "run the gamut" of snow->sleet->freezing rain
across northern lower Michigan toward Friday morning...with mainly
snow in the tip of the mitt and north of the bridge.

So...a bit of a mess possible by the Friday morning commute. But
fortunately as mentioned precip amounts overnight are expected to
be light with under half an inch of snow accumulation for the
northern counties...and just light icing (less than 0.1") in the
south. Of course...any amount of icing is problematic for travel
and we may need advisories at some point to handle the light
icing issues. But given this is a late 2nd->third period
issue...will let the day shift make the final call on that.

&&

.SHORT TERM...(Friday through Saturday)
Issued at 332 AM EST Thu Feb 22 2018

..Mixed Precipitation Friday then Dry then Another Storm...

High Impact Weather Potential...Ice accumulations of around 0.05"
are possible.

Pattern Synopsis/Forecast...As has been said the last few nights,
the models had not agreed much on the strength of the system, until
tonight. At 18z/Fri, the sfc low is in W/C Upper and both have a
1018 mb low and a fairly similar thermal pattern at 850 mb. Looking
at the model soundings, there is a decent warm nose that pushes up
into the region. The models are showing that the sfc temperatures
should, by 18z/Fri, be warming up enough that that M-72 and points
south should have just rain. In fact, the SREF plumes show that most
of the sites that are most likely to have freezing rain as the p-
type peak at 12z/Fri. So will expect that freezing rain overnight
through about 12z, then will expect the sfc warm air to move in with
some diurnal warming and change it to all rain through the day. by
the afternoon, the upper level moisture strips out, and looking at
the soundings, there is a decent signal for drizzle going into the
evening. The moisture and inversion continue to fall into Saturday
morning so that things dry out. Models show that high cloud during
the day. The next system moves into the Upper Mississippi Valley by
06z/Sun. So far, it looks like the precipitation will be snow, rain
or a mixture of both as the strong low moves stays to the west and
pulls the warm air north in the warm sector. Then the cold front
moves into lower Michigan by 12z/Sun and changes things back to
snow.

Primary Forecast concerns...Main concern with the Friday forecast
will be the speed at which the system crosses the forecast area. As
it moves through the freezing rain will transition to rain/drizzle
by the afternoon. this will depend upon speed of the upper moisture
stripping out. If this moves out faster, then we could go to FZDZ
instead of FZRA, and get lower amounts of ice accretion, before
transitioning to rain/drizzle.

The models seem to be on the same page as far as Saturday night into
Sunday with the precipitation starting as snow and with the strong,
deep, warm advection, transition to rain or a rain/snow mix, before
the cold front blasts in around 09z changing the rain back to snow.

.LONG TERM...(Saturday night through Wednesday)
Issued at 332 AM EST Thu Feb 22 2018

...Continued Above Normal Temperatures, Periodic Precipitation...

Extended (Sunday through Wednesday)...After the system from Saturday
night, Sunday morning lifts to the northeast, the 500mb pattern
turns zonal and temperatures remain in the 30s to around 40 through
the middle of the week.

As mentioned, we are in the midst of the a storm system Saturday
night into Sunday. By 18z/Sun, the sfc low is moving to the NE out
of the Upper Great Lakes and into James Bay by 00z. This blasts the
cooler air into the region, and should transition the rain to snow,
especially as we get into the night. The GFS drops the 850 mb
temperatures to around -10c by 12z/Mon while the ECMWF is -9C and
much drier. With the above normal temperatures at the sfc, will
expect that we will have some sort of a mix. Tuesday, a high builds
into the region and dries things out for the day. The models then
split their solutions Tuesday night as the GFS builds some
precipitation along a baroclinic zone, while the ECMWF has high
pressure and dry weather. So will have low chance pops for now on
Tuesday night which would be snow, but transition to Rain, mixed
rain/snow, during the day as we get into the milder temperatures
again.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1049 PM EST Wed Feb 21 2018

An area of high pressure settling in over the Great Lakes, will be
the main influence over northern Michigan through the forecast
period. VFR CIGS and VSBY are expected through Thursday afternoon as
dry air floods the region. MVFR CIGS will begin to overspread the
region toward the end of the forecast period, early Friday morning,
as another Plains storm system lifts into the Great Lakes.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
&&

$$

UPDATE...ADAM
NEAR TERM...ADAM
SHORT TERM...JL
LONG TERM...JL
AVIATION...SR



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