Area Forecast Discussion
Issued by NWS Gaylord, MI

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870
FXUS63 KAPX 170830 CCA
AFDAPX

Area Forecast Discussion...CORRECTED
National Weather Service Gaylord MI
330 AM EST Tue Jan 17 2017

.NEAR TERM...(Today and tonight)
Issued at 315 AM EST Tue Jan 17 2017

High impact weather potential: Freezing rain and accumulations.

Pattern synopsis and forecast:

Sfc low pressure and it`s associated slightly negatively tilted
upper trough are crossing nrn Il early this morning. Initial round
of WAA precip underneath double jet structure upper divergence,
and ahead of analyzed vorticity advection has weakened over the last
few hours as it moves into extremely dry air out ahead of it, as
seen on 00Z APX sounding. Strongest of forcing has worked in over
the GTV Bay region where the best reflectivities have been, while
sfc temperatures were at freezing or just below, with warming and
above freezing readings aloft and atmospheric saturation for
limited/no further wetbulb effects. Hence, precipitation has mainly
been freezing rain with just some intermittent snow/sleet mainly on
the front end of the precipitation. Forcing is stronger out ahead of
the main upper trough with the addition of DPVA, and was working
into srn Lake Michigan where additional precipitation was developing.

Heading into and through this morning, the initial round of WAA and
DPVA with the vort max weakens as it continues to move into very dry
air to the north. Meanwhile, additional DPVA joins upper divergence
and WAA as the sfc low works into srn lower, and results in the
strongest forcing through daybreak. Worst conditions over this time,
with continued cool/dry easterly low level flow keeping sfc temps at
33F or below (slightly warmer in downsloping flow across coastal
areas of NW lower). The atmosphere slowly saturates north through
nrn lower while this is going on, with warming temperatures aloft. A
great setup for primarily freezing rain. Now, as far as QPF, all
signals point toward the greatest QPF working in across the SE CWA.
This makes sense with the main upper trough and shortwave crossing
SRN lower. The deep moisture and forcing only scrapes eastern upper,
with minimal QPF expected there. Most of the precipitation arrives
when temps climb to 32F/33F, but even a degree or two above
freezing, cold road surfaces will continue to result in icy
conditions, while secondary roads will be quite slippery/hazardous.
For the most part, the advisories follow the expected transition to
a cold rain (maybe into early afternoon for the highest of terrain
around Gaylord), and will not tweak ending times. Day crew can
follow temperature trends to make those tweaks. Main idea, is that
this is primarily a freezing rain event for nrn lower, with the
impacts of such to continue even after the true freezing rain ends,
especially secondary roads.

The deepest moisture gradually exits through morning with maybe
things ending as a bit of freezing drizzle/drizzle. The sfc low
pushes through the eastern Great Lakes by evening while sfc
troughing lingers back across lower Michigan resulting in some
possible patchy light rain/mixed precip. Nice inversion aloft will
trap lower level moisture for cloudy conditions through much of the
night, but dry air sneaks into the western CWA late for possible
clearing skies.

Highs 32F-36F with lows tonight lower half of the 20s in eastern
upper to upper 20s/near 30F south.

&&

.SHORT TERM...(Wednesday through Friday)
Issued at 315 AM EST Tue Jan 17 2017

...Fairly quiet stretch of weather...

A blocky and stopped up pattern looks to set up across the region.
This is in the form of a rex block with ridging to the north and
troughing to the south which will make it tough for weather systems
to make it too far north into northern Michigan through the upcoming
weekend. However, there is some extended model disagreement on this
with the 17/00z ECMWF now depicting low pressure moving up into the
area Friday while a majority of other models dampen out the wave
before it makes it this far north. Confidence on this pattern which
is rather anomalous is on the fair at best but will side with the
drier guidance for now. Extended models do agree that the block
moves off to the east leading to a better chance of precipitation
early next week (mainly in the form of rain). Temperatures will be
on the mild side for sure as there is little to no cold air to be
found anywhere close to us.

Wednesday into Thursday night...Models are in good agreement that
very little is going on during this time. It`s too warm aloft for
any over lake instability. The one issue is cloud cover with model
soundings trying to hold onto a bit of low level moisture. Overall
partly cloudy skies and mild temperatures are expected with highs in
the upper 30s to middle 40s and lows in the middle 20s to lower 30s.

&&

.LONG TERM...(Friday night through Monday)
Issued at 315 AM EST Tue Jan 17 2017

Mainly dry and mild weather is expected through the weekend as
long as the ridge to the north hold it`s ground and allows for the
dry easterly flow to shield the area from systems to the south. By
early next week this pattern breaks down allowing low pressure to
make it up into our neck of the woods leading to the chance for
mainly rain Monday. Rather mild conditions expected to continue
through the period with cooler conditions perhaps returning by the
middle of the week.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1153 PM EST Mon Jan 16 2017

Wintry mix of precipitation (including freezing rain) and
attendant low cigs/IFR conditions will continue to slowly push
north through the overnight, with IFR conditions in low cigs and
light precipitation continuing through today. Not expecting
significant amounts of freezing rain or sleet/snow, but enough to
likely cause some impacts at the taf locations. Precipitation is
expected to gradually change over to light rain later today as
surface temperatures warm. Light winds through this taf cycle.


&&

.MARINE...
Issued at 315 AM EST Tue Jan 17 2017

Low pressure crosses srn lower Michigan today and then through the
eastern Great Lakes tonight with easterly winds turning northerly.
The easterly winds are expected to sneak into advisory levels over
Lakes Michigan and Huron today. Winds lighten up tonight as they
back SW into Wednesday morning. Winds increase through Wednesday
into Wednesday night with potential advisories over mainly Lake
Michigan.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...WINTER WEATHER ADVISORY until noon EST today for MIZ016>036-041-
     042.
LH...SMALL CRAFT ADVISORY until 5 PM EST this afternoon for LHZ345-
     347>349.
LM...SMALL CRAFT ADVISORY until 5 PM EST this afternoon for LMZ323-
     342-344>346.
LS...NONE.
&&

$$

NEAR TERM...SMD
SHORT TERM...AJS
LONG TERM...AJS
AVIATION...MSB
MARINE...SMD



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