Area Forecast Discussion
Issued by NWS Gaylord, MI

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407
FXUS63 KAPX 201725
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
1225 PM EST Tue Feb 20 2018

.UPDATE...
Issued at 943 AM EST Tue Feb 20 2018

Forecast challenges are many this morning, ranging from ongoing
ice storm across the northern third of the area, to reports of
heavy rain and flooding down near Saginaw Bay. Slow northward
moving warm front the culprit, with a rather sharp temperature
gradient along this front (as evident by Cadillac spiking from the
upper 30s to lower 50s within a few hours this morning). This
front will continue to bow north, expected to bring much milder
weather and end the icing threat across northern lower in the
process. End times for those south of the big bridge winter
weather headlines still looks reasonable. Cold air will hang on
longest across eastern upper, but that area also is expected to
experience much less precipitation. No doubt untreated road
surfaces will continue to remain ice-covered and very slick as
freezing drizzle/light freezing rain continues.

Waves of moderate to heavy rain will continue to impact areas down
near Saginaw Bay through this evening, with one wave pivoting
overhead now, with another wave of rain set to arrive later today
into this evening. Already receiving reports of standing water
and nuisance type flooding down in that area, and expecting these
conditions to expand/worsen with time as the rain continues. As
such, have upgraded inherited watch to a flood warning, running
this warning right through early Wednesday morning.

UPDATE Issued at 529 AM EST Tue Feb 20 2018

Pellston continues to rack up ice accumulation...up to 0.23 inch
as of 5 am. Although most persistent showers are just about to
end...still quite a bit of freezing drizzle evident on KAPX radar
across northern lower Michigan which may push ice totals over one
quarter inch up that way. So...have pulled the trigger on the ice
storm warning for Emmet and cheboygan counties...where heavier
precip and below freezing temps were most persistent overnight.

&&

.NEAR TERM...(Today through Tonight)
Issued at 352 AM EST Tue Feb 20 2018

...Icing issues persist...

High Impact Weather Potential...Light icing across EUP and the tip
of the mitt.

Pattern Synopsis/Forecast...Overnight composite analysis reveals a
deep open wave trough across the western CONUS and downstream
anomalously strong ridging through the SE states anchored by an
impressive 594 DM high off the Florida coast. Deep S/SW flow extends
from Texas up through the Great Lakes and continues to pull a
moisture rich airmass through the Midwest and lower Great Lakes
region.

At the surface...inverted trough/boundary stretches from some
semblance of a closed surface low over the Midwest up through
central lower Michigan with a very tight thermal gradient across
the northern lakes down into the central plains and associated
strong upper jet core riding up through the western/northern lakes
region into Canada. Waves of precip (with some thunder downstate)
continue to stream through the Midwest up through lower Michigan
basically along the surface front. And with the slightly further
south frontal position...colder air has bled a little further
south into lower Michigan keeping temps right or just above
freezing into the M-72 corridor...especially the higher
terrain...with some icing/sleet occurring in those areas
overnight. Snow and sleet ongoing in EUP.

Surface low to our southwest will ride up through northern lower
Michigan this afternoon/early evening and finally kick the
boundary S/E through northern Michigan by later evening/early
overnight. Strong high pressure and much drier air build into the
region overnight into Wednesday ending the precip and knocking
temperatures back down to near normal readings.

Primary Forecast Concerns...ongoing icing concerns...hydro issues
in the south.

Per regional radar mosaic...current batch of showers moving
through northern lower Michigan will move on to the east within
the next few hours...leaving a bit of a lull in precip at least
for the early morning hours. Several more waves of widespread
precip are anticipated later this morning and throughout the
afternoon/evening as aforementioned sfc low pressure to our SW
swings up through northern lower Michigan. Precip coverage and
amounts still expected to tail off considerably S-N across the
CWA...but of course our bigger issue is the ongoing icing.

Overnight surface obs suggest most of the icing thus far has been
across the tip of the mitt and possibly into Mackinac county. PLN
ASOS reported 0.14 inch of icing between midnight and 3 am which
is a bit concerning since it`s starting to approach ice storm
warning territory. Fortunately...there will be a lull in precip
coming up shortly...so that may keep those icing amounts below one
quarter inch. Will see.

Meanwhile...as the sfc low to our southwest rides up through
northern lower Michigan over the next several hours...warmer
(above freezing) air up will slide up through all of northern
lower Michigan...ending the freezing rain threat for northern
lower Michigan by late morning or so. It will take a bit longer
for temperatures to warm above freezing in eastern upper Michigan
with some light icing likely to continue through a good part of
the day.

Headlines: Current headlines look appropriate for the moment
although I will have to keep an eye on ice accumulations across
the tip of the mitt (PLN). May have to pull the trigger on an ice
storm warning if accumulating ice does not diminish there soon.
Icing issues will end for all of northern lower Michigan by around
noon or so and probably earlier for the M-32 corridor (temps
already >32F at GLR and at APX). So...current advisories will
remain intact...but I will trim back the end time by a few hours
for the Otsego->Alpena corridor. Eastern upper Michigan
(especially Chippewa county) will be dealing with light icing for
much of the day as temps just warm to AOA freezing readings this
afternoon. But given a bit more snowfall up that way last evening
and overnight...I don`t think ice accumulations will reach
warning criteria there.

Finally...hydro issues. MMRS 24 hr precip totals suggest between
0.5 and 0.75 inch of precip across the SE counties thus far...with
several more waves of precip to come likely doubling those totals.
No known flooding issues down that way as of yet. Thus will keep
the flood watch going until we hear otherwise. River flood warning
for the Rifle River near Sterling was issued last evening based
on the RFC river forecast and will of course also remain intact.

&&

.SHORT TERM...(Wednesday through Thursday)
Issued at 352 AM EST Tue Feb 20 2018

...Beginning Drier Weather until Thursday night...

High Impact Weather Potential...

Pattern Synopsis/Forecast...High pressure drives moisture out of the
Upper Great Lakes during the morning. The high then moves across the
Upper Great Lakes Wednesday night, and then onto the east on
Thursday. By 00z/Fri, the next system begins to knock on the door
and moves into northern Michigan between 09z/Fri and 12z/Fri. It
looks like there could be some mixed precipitation along M-55 during
that time, with the chance of snow elsewhere. 850 mb temperatures go
above freezing along M-55 and the ECMWF suggests as far north as
M-72.

Primary Forecast concerns...Most of the time will be rather quiet as
the high moves through the Upper Great Lakes and northern Michigan.
The questions arise with the Thursday night/Friday morning forecast
as the warm air moves north. A couple of things to think about...if
the winds are due south like the GFS and ECMWF show, then the sfc
warmth will move north with the 850 warmth, so we may not get much
in the way of mixed precipitation. The SREF, however, is showing a
WSW wind, which is almost a neutral/cold advection, and would bring
the likelihood of snow along M-55. Think will continue the forecast
since it looks more of the middle of the road.

.LONG TERM...(Thursday night through Monday)
Issued at 352 AM EST Tue Feb 20 2018

...A Brief Cool off, then Gradually Warming for the Weekend...

Extended (Friday through Monday)...After the front moves through on
Friday morning, high pressure builds into the forecast area and
dries thing out through Saturday afternoon. Saturday evening a
strong wave moves out of the Central Plains, and into lower Michigan
overnight. The GFS has a 988mb low, while the ECMWF has a 1005mb
low. Both models has roughly the same track, but the strength of the
storm will wrap more warm air on the GFS solution while the ECMWF
would have more snow. Sunday looks like it will be a day where the
afternoon may dry out, but the Sunday night definitely does and into
Monday afternoon. Another quick storm moves through the region late
Monday afternoon and night.

Temperatures through days 4-7 look to be in the lower to mid 30s in
E Upper each day, while N lower temperatures range from the mid 30s
to the lower 40s.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1223 PM EST Tue Feb 20 2018

More IFR/MVFR conditions expected into this evening as low clouds
and rain spread back northeast across the taf locations. Cigs and
rain scatter out later tonight into Wednesday as high pressure
builds into the region. Low level wind shear end later today, with
light surface winds becoming a bit gusty out of the northwest
later tonight into Wednesday morning.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...WINTER WEATHER ADVISORY until 1 AM EST Wednesday for MIZ008-015.

ICE STORM WARNING until 1 PM EST this afternoon for MIZ016-017.

WINTER WEATHER ADVISORY until 1 PM EST this afternoon for MIZ018-
019.

&&

$$

UPDATE...MB
NEAR TERM...BA
SHORT TERM...JL
LONG TERM...JL
AVIATION...MB



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