000
ACUS01 KWNS 211954
SWODY1
SPC AC 211952

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0252 PM CDT Fri Sep 21 2018

Valid 212000Z - 221200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS THE
LOWER GREAT LAKES REGION...

...SUMMARY...
Severe thunderstorm winds and a couple of tornadoes are possible
across parts of the lower Great Lakes region through this evening.

...Discussion...
No significant changes have been made to the ongoing forecast,
except for removing areas behind the primary surface trough
(extending from western Kentucky to western Ohio as of 20Z).
Convection is slowly deepening along the trough from the mid Ohio
Valley to Lakes Erie and Ontario this afternoon. Storms are still
expected to evolve into a QLCS structure, given relatively
uni-directional deep-layer flow and strong low-level shear. Damaging
winds will be the primary threat, although a couple brief tornadoes
could occur from eastern Ohio to western New York. By mid/late
evening, convection should be entering a considerably less favorable
thermodynamic environment across eastern PA/NY and New England,
where stratus clouds have been persistent. A localized damaging wind
threat could be maintained given strong wind fields, but with most
large-scale ascent focused in Canada, deeper convective circulations
(and resultant downward momentum transfer) should diminish notably
overnight.

..Picca.. 09/21/2018

.PREV DISCUSSION... /ISSUED 1126 AM CDT Fri Sep 21 2018/

...Lower Great Lakes from 21-03z...
A midlevel shortwave trough over the upper Great Lakes will move
quickly eastward over southern ON and QC through tonight, as an
associated surface cyclone moves northeastward and deepens from Lake
Superior.  A trailing cold front will progress eastward across the
OH Valley and lower Great Lakes by this evening.  Surface heating in
cloud breaks south and west of a surface warm front will allow
destabilization across western NY into western PA/OH, in advance of
the cold front.  Thunderstorm development is expected along the cold
front and pre-frontal trough by mid afternoon from OH into
southwestern ON, and perhaps along a weak lake breeze along the east
shore of Lake Erie.

12z regional soundings revealed rather poor lapse rates above 700
mb, though surface temperatures in the 80s with boundary-layer
dewpoints in the 68-72 F range will support MLCAPE of 1000-2000
J/kg.  Deep-layer vertical shear will increase with the approach of
the midlevel wave from the Great Lakes, with effective bulk shear
expected to strengthen to 45-55 kt.  Though supercells will be
possible with the initial development (mainly in southwestern ON),
largely front-parallel shear vectors and deep-layer flow suggest
that convection will evolve rather quickly into a squall line in the
21-00z time frame.  Damaging winds will be the main threat with the
line of storms, given the potential for downward transport of 50-60
kt low-midlevel flow.  Along the east edge of the warm sector, there
will be a narrow zone of enhanced low-level shear coincident with
surface-based buoyancy.  Based on the expected linear convective
mode, a few embedded circulations and a couple of QLCS tornadoes
will be possible.  The severe threat should increase by 20-21z
beginning in central/northeastern OH, then spread east-northeastward
into western PA/NY through this evening.  As the storms move east of
the stronger buoyancy and into central NY/PA, weakening is expected
by about 03z.

$$

000
ACUS02 KWNS 211658
SWODY2
SPC AC 211656

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1156 AM CDT Fri Sep 21 2018

Valid 221200Z - 231200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
The threat for organized severe weather appears low on Saturday.

...Discussion...
Fast/confluent westerly flow aloft will persist across the Northeast
and parts of the Midwest Saturday, in the wake of a strong shortwave
trough advancing east into the Canadian Maritimes. The resultant
surface pattern will feature an elongated ridge building east across
the lower Great Lakes and into the Northeast. In turn, a cold front
will gradually progress south/southeast along the Mid-Atlantic
coast. A few storms are expected along/ahead of the front in
Virginia/North Carolina by afternoon, within a weak/modestly
buoyancy environment characterized by favorable boundary-layer
moisture, but poor mid-level lapse rates and dry air. Combined with
weakening flow with southward extent, this thermodynamic environment
should keep any severe threat low.

The aforementioned front will extend westward to north Texas (more
in the form of a stationary front). Ahead of a primary vorticity
maximum, rich tropospheric moisture will maintain a heavy rain
threat where elevated warm advection/frontogenesis is maximized.
Weak/disorganized mid-level flow intersecting only modest buoyancy
should preclude organized severe weather, though.

...MAXIMUM RISK BY HAZARD...
Tornado:  <2%     - None
Wind:     <5%     - None
Hail:     <5%     - None

..Picca.. 09/21/2018

$$

617
NWUS53 KAPX 212032
LSRAPX

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GAYLORD MI
432 PM EDT FRI SEP 21 2018

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0354 PM     NON-TSTM WND GST 3 SSE EAST TAWAS        44.25N 83.46W
09/21/2018  M48 MPH          IOSCO              MI   MESONET

            MESONET STATION XTAW, 2 SE EAST TAWAS.


&&

$$

000
FXUS63 KAPX 212305
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
705 PM EDT Fri Sep 21 2018

.NEAR TERM...(Through Tonight)
Issued at 341 PM EDT Fri Sep 21 2018

...Winds diminishing...

High impact weather potential...strong winds to gradually weaken.

984mb low pressure is just south of James Bay. Gusty westerly winds
persist in cold advection behind a departed cold front. Earlier
concerns that this would be marginal wind event were shown to be
unfounded; this has been a solid wind advisory event across most of
northern MI. 45-55mph gusts have been common, and have expanded this
afternoon into places like TVC and HTL. Some 20 to 30 percent of
Antrim/Emmet/Charlevoix Cos are without power as I type this, per
local utilities, and those numbers were recently higher. Winds
will relax considerably tonight as the pressure gradient rapidly
relaxes behind the departing low. But wind trends are the clear
primary concern.

The pressure gradient will relax from sw to ne as the surface low
ejects. Guidance and surface ob trends argue that most of northern
MI will need the wind advisory extended at least a bit past 5 pm.
Already extended eastern upper MI and the APN/Rogers City area thru
10 pm. 1km AGL winds of 40-50kt will linger shortly past 00z there
per near term model guidance; losing diurnal heating/mixing will
take a bit of sting out of the winds, but a longer duration
extension was still needed there (especially along coastlines). On
the other side of the forecast area, the far sw (CAD/MBL/FKS) never
got into better winds today, and can leave them alone thru the
original 5 pm expiration. In between these areas, 40-50kt 1km AGL
winds will linger just past 5 pm. An shorter extension is needed
for those counties (including TVC/PLN/GLR/HTL).

Broken cellular cloud cover prevails in most of northern MI, with
with far se seeing more in the way of sunshine presently. There
are a few spits seen on radar here and upstream, but at the moment
only a few blips rise to the level of `showers`. The arrival of
cooler air and lake instability is battling the arrival of drier
mid-level air. A little more moisture is available in eastern
upper MI this evening, as they get grazed by the comma head of the
departing system. Still, hard to go with more than just a sct pop
in eastern upper, nw and n central lower MI thru late evening.
Pops disappear after that, as much drier air arrives and inversion
heights crash.

We have cooled slower than expected today (OSC was still 80f at
3pm!). The pressure gradient will very abruptly relax tonight,
but it will still take quite a while for even well-sheltered
locales to decouple. The current gridded forecast has only a
handful of pixels in both peninsulas reaching temps cold enough
for patchy frost. Have thus removed a mention of such from the Haz
Wx Outlook. It will still be far, far colder tonight than last
night, with mins in the upper 30s to mid 40s.

&&

.SHORT TERM...(Saturday through Monday)
Issued at 321 PM EDT Fri Sep 21 2018

High Impact Weather Potential: None.

Pattern Synopsis/Forecast: As high pressure builds further into the
region through the day Saturday. Winds will continue to diminish as
the pressure gradient relaxes. We will remain under this high
pressure through the weekend, with another area of high pressure
approaching from the north. Convergence associated with these
pressure centers could produce some showers in far northern portions
of the CWA Saturday night/early Sunday, primarily in Chippewa
County. Upstream, low pressure will be lifting through western
Ontario through the day Monday. This will bring a cold front to the
region by mid week, perhaps as early as Tuesday.

Primary Forecast Concerns: Aside from the low chance PoPs across
Chippewa county Sunday, weather over the weekend and into the start
of next week will be relatively quiet. More active weather will
begin Monday night. Isentropic ascent ahead of the approaching front
could bring showers in earlier than expected, but right now it looks
like that won`t start until Monday night.

.LONG TERM...(Monday night through Friday)
Issued at 321 PM EDT Fri Sep 21 2018

Rain chances will increase Monday night ahead of an approaching cold
front. These rain chances will continue through early Wednesday as
forcing along the cold front replaces isentropic ascent ahead of it.
Lingering showers should clear up by Wednesday morning. Post frontal
subsidence and high pressure briefly building in will bring more
quiet weather after mid week, with another system approaching for
the weekend.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 705 PM EDT Fri Sep 21 2018

Strong NW winds of 15 to 25 kts gusting to 35 kts will steadily
diminish this evening...dropping below 10 kts during the overnight
hours. Residual showers will come to an end this evening as
well...with decreasing clouds overnight and SKC below 12 kft
expected for Saturday as high pressure builds into the region.

&&

.MARINE...
Issued at 321 PM EDT Fri Sep 21 2018

Gales will gradually diminish this evening and tonight, as strong
low pressure just south of James Bay moves further ne away from
the region. Will fine-tune gale warning expiration later this
afternoon. High pressure will build toward the southern lakes for
Saturday, resulting in much quieter marine conditions. Sw winds
will pick up a bit on Sat night, especially on Lake MI. Advisory-
level winds/waves not out of the question.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...WIND ADVISORY until 8 PM EDT this evening for MIZ016-017-019>023-
     026>030-033>036-041-042.
     LAKESHORE FLOOD WARNING until midnight EDT tonight for MIZ008-
     016-019>021-025-031.
     BEACH HAZARDS STATEMENT until 8 PM EDT this evening for MIZ016-
     019>021-025-031.
     BEACH HAZARDS STATEMENT until midnight EDT tonight for MIZ008-
     015-017-018-024-030-036-042.
     WIND ADVISORY until 10 PM EDT this evening for MIZ008-015-018-
     024.
LH...GALE WARNING until midnight EDT tonight for LHZ345>349.
LM...GALE WARNING until midnight EDT tonight for LMZ323-341-342-
     344>346.
LS...GALE WARNING until midnight EDT tonight for LSZ321-322.
&&

$$

NEAR TERM...JZ
SHORT TERM...AM
LONG TERM...AM
AVIATION...MR
MARINE...JZ

000
ACUS11 KWNS 212304
SWOMCD
SPC MCD 212304
NYZ000-PAZ000-WVZ000-OHZ000-220100-

Mesoscale Discussion 1494
NWS Storm Prediction Center Norman OK
0604 PM CDT Fri Sep 21 2018

Areas affected...Eastern Ohio...western and central
Pennsylvania...western and central New York

Concerning...Severe Thunderstorm Watch 386...387...

Valid 212304Z - 220100Z

The severe weather threat for Severe Thunderstorm Watch 386, 387
continues.

SUMMARY...Mainly a damaging wind threat continues with storms along
a cold front. Gradual weakening is expected as the boundary layer
cools, and storms begin moving into a less heated/more stable
airmass. A wider warm sector in western/central Pennsylvania may
allow for storms with isolated damaging wind gusts to continue east
of Severe Thunderstorm Watch 0386, and a Severe Thunderstorm Watch
issuance downstream may be necessary.

DISCUSSION...Earlier semi-discrete storms have recently congealed
into a squall line, from ROC, down to LCK, with the corridor of
strongest storms (with a history damaging wind gusts) located from
just west of BFD to PHD. These storms have organized in a kinematic
environment characterized by 50-60 knots of bulk effective shear,
with up to 250-300 m2/s2 effective SRH noted in northwest PA into
western NY. Despite the favorable shear environment, the airmass
downstream of the squall line (central PA to central NY) is more
stable, with surface temperatures mainly in the low 70s, owing to a
stratus deck which has limited insolation.

As such, the squall line is expected to traverse a more buoyant
airmass for the next few hours, characterized by surface
temperatures in the lower 80s and MLCAPE up to 1000 J/kg. During
this time, storms may continue to produce damaging wind gusts and
perhaps exhibit transient low-level rotation (given the strong
low-level speed shear in place). Thereafter, a weakening trend is
expected given the cooler temperatures to the east and the
cooling/decoupling of the boundary layer overall.

The buoyant warm sector between the ongoing squall line and a more
stable airmass to the east is narrower in New York as opposed to
western and central Pennsylvania. Storms may continue past the
eastern bounds of Severe Thunderstorm Watch 0386 with at least an
isolated damaging wind threat and an additional Severe Thunderstorm
Watch issuance may become necessary in a few more hours.

..Squitieri/Grams.. 09/21/2018

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...BTV...ALY...BGM...BUF...CTP...PBZ...CLE...

LAT...LON   40098211 40668190 41428057 42487904 43337784 43817645
            44247538 43967495 43417492 42097615 41227696 40377816
            39947927 39978099 40098211