Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 180057

Area Forecast Discussion
National Weather Service Gaylord MI
857 PM EDT Mon Oct 17 2016

Issued at 857 PM EDT Mon Oct 17 2016

The weather is really starting to crank up now, with sfc low
pressure lifting into eastern upper and low to mid level strong
waa throwing deepening low level moisture (12c at H8) via a 70kt
LLJ over a warm front across the Straits/eastern upper. Deep layer
-divQ is strong, aided by upper divergence on the nose of an 120kt
jet streak punching into Wisconsin. The atmosphere was already
primed with 1000-1200 j/kg in place with 6.5c/km lapse rates. The
arrival of a shortwave and the sfc low just to our west, was
resulting in storms from Wisconsin, to developing showers and
storms working toward eastern upper, all along and north of the
frontal zone. 0-6km bulk shear was more than impressive at 60kt,
but the low levels were stable under extensive clouds and
temperatures in the mid to upper 50s.

The strong forcing and elevated instability over the next 4-5 hrs
will result in a threat for primarily large hail, and it`s looking
more so like western sections of Chippewa and Mackinac counties of
eastern upper are the main threat. Probably too early to say that,
we`ll see how this lays out. Significant severe parameter was
15,000 to near 20,000 m3/s3, suggestive of the potential for maybe
up to 2" diameter hail. The cool BL will limit effectiveness for
the strong winds aloft from reaching the sfc. Also, the energy
helicity index diminishes with time and the stable BL won`t help
tornadic matters either. Primarily a large hail threat.

The sfc cold front with a much less unstable atmosphere overnight
into Tuesday morning, and only some showers expected, but can`t
completely rule out a little thunder. The severe threat should be


.SHORT TERM...(Tonight and Tuesday)
Issued at 315 PM EDT Mon Oct 17 2016

Complex and somewhat challenging forecast tonight, as there are lots
of things going on and a fair number of uncertainties.  Next short
wave will advance through the upper Midwest and northern Great Lakes
region late tonight into Tuesday morning, accompanied by an
impressive upper jet streak punching into the Great Lakes.  As this
happens, surface low develops and deepens quickly as it heads into
Lake Superior overnight.  Strongest QG-forcing slides across
northern Wisconsin and northern Michigan, mainly from the Tip of the
Mitt into eastern upper, where another round of showers and
thunderstorms are likely. Still some low end severe threat given
0- 6km bulk shear values of 60-80kts and elevated instability
along and north the sloped warm frontal surface. Once again,
stable lower layers will remain a limiting factor to well
organized severe weather but as we saw earlier this morning, deep
layer shear can sometimes compensate for the lake of surface based
instability to still produce strong updrafts and large hail (ping
pong ball size in Glennie this morning). Can`t even rule out an
isolated spin up along or just north of the frontal boundary. The
other factor is wind, where some of the showers/storms may be able
to tap into the very strong wind fields aloft to bring very gusty
winds to the surface. Pressure gradient will be tightening this
evening and expect a window from late evening through the
overnight hours with gusts of 40+ mph in some locations along the
immediate Lake Michigan coast, as well as around Whitefish Point.
Some wind advisory gusts a possibility, but the duration for this
event is short and will therefore not issue any land based wind
headlines at this time (but will highlight winds in the HWO and
weather graphics).

Front slides through the area Tuesday morning with a relative
whimper, lacking deep moisture or forcing. Some scattered showers
likely along the boundary but that should be about it. Winds will
remain gusty during the morning, especially northeast lower
Michigan, where coastal convergence with northwest flow will
result in some 30+ mph gusts. After a very mild night
in the upper 50s to lower 60s (summerlike), temperatures will be
steady or slowly on the decline on Tuesday with developing cold
air advection after fropa.

.LONG TERM...(Tuesday night through Monday)
Issued at 315 PM EDT Mon Oct 17 2016

Tuesday night through Thursday...

High impact weather potential: None expected.

Pattern synopsis/Expected evolution: By Tuesday night, rather zonal
flow is expected across the midsection of the nation with a 130+ kt
speed max extending from the central plains through the northern
Great Lakes. At the same time, a shortwave trough begins to take
shape lee of the Rockies before sliding toward the area late
Wednesday night into Thursday with surface cyclogenesis ongoing
across the Ohio Valley, aiding to draw in much cooler air across
the northern plains/Great Lakes late week into the weekend.

Tuesday night through Wednesday night: Tuesday`s cold front should
be well south and east of the CWA by Tuesday evening, ultimately
returning precip chances to near zero and gradually filtering in
cooler air across northern Michigan. As upper level troughing
approaches from the west on Wednesday, expecting an increase in
cloud cover (especially during the afternoon), although most
locations look to remain dry. The exception is across portions of
eastern Upper/ Straits/Tip of the Mitt where a few sprinkles or
light showers may kick off late Wed. evening into the early
overnight hours as a a pocket of low-mid level moisture associated
with a subtle ripple embedded within the larger aforementioned
trough rotates through the area. Above normal temps continue with
highs in the low-mid 60s across the area. Overnight lows both nights
bottom out in the 40s.

Thursday: Surface cyclogenesis is ongoing across the Ohio Valley
Wednesday night into Thursday with the axis of heaviest precip
expected to remain over Indiana/Ohio; however, guidance continues to
struggle with the overall northern extent of precip throughout the
day. Certainly the best threat for showers will be south of M-72 and
east of I-75, tapering as you head north and west. Have bumped up
PoPs slightly across those areas, but widespread/heavy precip is not
expected. Perhaps the bigger story on Thursday will be the start of
a more appreciable cool down for the upcoming weekend as cooler air
spills into the northern Great Lakes on the back side of the
departing Ohio Valley low pressure system. Thursday`s highs are
expected to struggle to reach the mid-50s, save for locations near
Saginaw Bay.


500MB pattern shows troughing developing over the great lakes for
the first part of the period...allowing a pretty good shot of colder
Canadian air to spill over the region. The GFS is a bit more bullish
with just how cold the air would be...presenting H8 readings of -6c
as far south as West Branch. From a moisture/weather perspective the
Euro is the model that`s more bullish on precip potential than the
drier GFS.  All that said, there`s enough evidence in both models to
suggest the blended solutions of "less cool and drier" for the first
part of the period might be overdone.  In chatting with the
neighbors...we agreed to shave a few degrees off temps Thursday
night through Saturday morning.  We also added some chance pops for
lake effect potential.  Should this come to fruition...wouldn`t be
shocked to see a few snowflakes...particularly during the diurnally
favored periods where lows may be approaching the 32 degree mark.
The second half of the period is pretty hazy.  The pattern wants to
shift more zonal, but a quick moving short wave ripples through
Sunday to Monday.  Although I think we`ll see temperatures moderate
a bit for Sunday and Monday, we`re talking about just back to
normal...which may "feel" cool considering just how warm it`s been.



.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 746 PM EDT Mon Oct 17 2016

...More LLWS...

Sfc low pressure will lift along a warm front draped across
eastern upper. Showers and storms will fire off in the vicinity of
this warm front primarily impacting PLN for a time this evening.
Severe storms with large hail are possible across eastern upper,
with a smaller chance in the vicinity of PLN. The system cold
front and additional possible showers will cross late tonight into
Tuesday, with the chance for thunder quite low. Skies are then
expected to become sct-bkn with afternoon cumulus.

CIGS will lift to VFR through evening and into the overnight,
before lowering back to a period of MVFR with/behind the cold

The main story once again are winds. Low level winds really ramp
up significantly starting right at the first hour of the TAF.
35-50kts of LLWS are expected just above the sfc through most of
the night until the cold front and weaker pressure gradient
arrive. Winds shift more westerly behind the front with gusts
kicking in again as Tuesday morning progresses.


Issued at 315 PM EDT Mon Oct 17 2016

Gusty winds will be found on the lakes tonight and Tuesday
as a warm front lifts north through the area and a deep area of
low pressure tracks through the northern Great Lakes. Widespread
Small Craft Advisories through the period, with a 3-5 hour window
of potential gale force gusts on Lake Michigan late this evening
and overnight.

Winds gradually diminish through the day Tuesday and especially
Tuesday night.


LH...SMALL CRAFT ADVISORY until 4 PM EDT Tuesday for LHZ345>349.

LM...SMALL CRAFT ADVISORY until 4 PM EDT Tuesday for LMZ323.

     GALE WARNING until 5 AM EDT Tuesday for LMZ341-342-344>346.

LS...SMALL CRAFT ADVISORY until 4 PM EDT Tuesday for LSZ321-322.



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