Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 170439
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
1139 PM EST Thu Feb 16 2017

.UPDATE...
Issued at 915 PM EST Thu Feb 16 2017

Quiet night ahead...in a relative sense. Large scale ridging/warm
air continues to build across the central and northern plains...
edging into the western Great Lakes this evening. A tight thermal
gradient and some modest warm advection forcing along the eastern
edge of the ridge is producing several batches of mid/high cloud
cover now streaming through the region tonight. Had one pocket of
stronger forcing and ominous looking radar returns roll through
the SW part of the CWA this evening. Elevated returns however
revealing mostly virga, with no surface obs reporting any precip,
although I would not be surprised if a few flurries were seen by
some.

Rest of tonight: Several batches of mid and high cloud cover will
continue to roll eastward through the region. Strongest forcing
and best shot at actually seeing any precip has already slid on by
into southern lower Michigan. Thus the dry forecast will hold.
Meanwhile, we currently have quite the range of temps across the
CWA, ranging from 11 degrees at Rogers City where skies have been
mainly clear for a sliver of eastern upper and northeast lower
Michigan, to 29 degrees at Frankfort under cloudy skies. Temps
will likely roller coast through the night as thicker cloud cover
rolls through, then drop everywhere again late as clouds thin
toward morning. So a tough low temperature forecast, but I have
tweaked forecast lows a bit, mainly to account for those cold
readings already seen at Rogers City/Cheboygan/Kinross etc.

&&

.NEAR TERM...(Tonight and Friday)
Issued at 321 PM EST Thu Feb 16 2017

...Much talked about warm-up begins Friday...

High Impact Weather Potential: Nothing.

Pattern Synopsis/Forecast: Current amplified NOAM pattern in the
rapid process of breaking down as upstream Pacific flow remains very
progressive. Our area still largely under the influence of east
coast Gyre, with northwest upper level winds overhead. Lake
processes have largely ended as low/mid level warm advection begins
to ramp up. Subtle vort lobe/weak shortwave rotating southeast on
backside of this eastern trough bringing a band of high and mid
level clouds into the area. Regional radars show some light snow
falling out of this cloud deck back to our northwest, although very
dry low levels has prevented much of this from reaching the surface.

As mentioned, pattern goes through some serious changes heading
through tonight and Friday, with east coast system getting the rapid
boot to the northeast as upstream ridging builds east into our area
by later Friday. Combine that with an eastern retreat to current
overhead surface high pressure, and all systems are go for a
significant upward temperature response on Friday.

Primary forecast concerns: Addressing cloud and temperature trends
through Friday.

Details: Initial concern lies with that southeast band of upper and
mid level moisture tied to passing vort max. Clouds will increase
into this evening, but still think lack of deeper low level moisture
will prevent any meaningful snow from reaching the surface (suppose
a few flurries are possible). Skies expected to scatter out again
later tonight as moisture plume departs. Above cloud trends make for
a rather challenging temperature forecast, especially considering
dry low levels and maintenance of light winds. Still think there is
a decent window later tonight for temperatures to drop
significantly, so will continue to side to the colder end of the
guidance spectrum, featuring widespread lows in the teens in the
traditional colder interior regions.

Big story for Friday is the upward temperature trend. Just off-the-
deck warm air advection is simply off the charts, with H8
temperatures pushing +10c by evening!. While shallow inversion
levels will prevent tapping this full warming potential, plenty of
sunshine and developing light southerly flow will sure do a number
on surface temperatures. Backward run trajectory models show
tomorrows afternoon near-surface airmass currently sitting over
southern Illinois, where temperatures are currently well into the
50s. Airmass will of course modify some as it heads north over the
cool waters and snow pack. Still, think most guidance progs are
giving too much credit to just how much this will cool the airmass.
Will side toward the warmer end of the guidance spectrum (Canadian
region numbers, which has a history of doing excellent in these type
of anomalous temperature events), with much of northern lower into
the 40s, and upper Michigan just a few degrees cooler.

&&

.SHORT TERM...(Friday night through Sunday)
Issued at 321 PM EST Thu Feb 16 2017

...Dry warm weather...

High Impact Weather Potential...none

Pattern Synopsis/Forecast...Alberta clipper system rides well to the
north from the 500 mb ridge progressing through the Upper Great
Lakes. sets up warmth that is 2 to 3 standard deviations above
normal for the weekend. So the only issues that this would cause
will be the melting snow running off into the rivers. So there will
be some rises.

Primary Forecast Concerns...As stated, the primary concerns will be
run off from the snow melt. With the dewpoints being around
freezing, and the temperatures so warm (40-50F) the dryness may help
to keep the glaciated snow from melting off rapidly. This will be
something to watch in the coming days.

.LONG TERM...(Sunday night through Thursday)
Issued at 321 PM EST Thu Feb 16 2017

High Impact Weather Potential...rivers?

Extended (Monday through Thursday)...the days 4-8 day anomalies are
showing positive height anomalies over the Upper Great Lakes for
most of the period, which would keep us, most of the time, above
normal. The only brief pause would be Monday night into Tuesday when
the attendant cold front to a system moving out of the Plains into
the Hudson Bay, brings rain or in some areas, a mix of rain and
snow. We then get into a flat ridge (so positive height anomalies)
with a few shortwave troughs moving through it. It again keeps us
(at least at 850 mb, almost 2 to 3 SD above normal again. Thursday
is the one day when we begin to head back to normal as a cold front
sags south to cool things off.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1139 PM EST Thu Feb 16 2017

VFR conditions anticipated through the upcoming TAF forecast
period. Narrow band of mid/high level cloud cover will slide
through the region overnight into Friday morning...cloud bases
AOA 6K feet.

On Friday...VFR continues as warmer air noses into the region
through the day. Model guidance continues to suggest the
development of lower stratus/fog Friday night...the result of
warmer air/increasing dewpoints and snowmelt. Continue to believe
that guidance is a bit premature although some fog development may
occur Friday night for parts of northern lower Michigan. We may
indeed get into some stratus/fog issues heading into the weekend,
but only after warmer air/higher dewpoints get here.

&&

.MARINE...
Issued at 321 PM EST Thu Feb 16 2017

Light/variable winds become southeast tonight and increase
in speed some as surface high pressure pushes east. Both winds and
waves expected to remain below advisory criteria. This same idea
continues through Friday night, although winds slowly veer more
southwest with time.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...NONE.
LM...NONE.
LS...NONE.
&&

$$

UPDATE...TBA
NEAR TERM...MSB
SHORT TERM...JSL
LONG TERM...JSL
AVIATION...TBA
MARINE...MSB



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