Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 191927

Area Forecast Discussion
National Weather Service Gaylord MI
327 PM EDT Mon Jun 19 2017

.NEAR TERM...(Tonight through Tuesday)
Issued at 324 PM EDT Mon Jun 19 2017

...Self-destruct Sunshine and Afternoon Thunder Tuesday...

High Impact Weather Potential...none.

Pattern Synopsis/Forecast...500 mb upper low will continue to spin
just north of the Upper Great Lakes and with it will rotate spokes
of energy over the forecast area, during the heat of the day. This
will continue the  showers and thunderstorms from the afternoon into
the evening, before ending. There will still be a small chance for
showers overnight, as another shortwave trough rotates into the
region overnight. Models (GFS, ECMWF, and both Hi-Res models) show
showers overnight and then increasing in coverage late morning
before the MLCAPE pushes up into the 200-300 J/KG range from the
daytime heating in NE Lower around 18z. However, this time, the
upper low and the cold pool aloft begins to finally move to the east
and brings the chances down by 00z/Wed.

Primary Forecast Concerns...Wet bulb zero heights are even lower
than today (around 6900 ft.) so the chances for small hail will
still be there. The DCAPE is also around 150 J/KG so there could be
some winds issues, and if the storms become "pulsey" we could run
into some issues with the thunderstorms. However, this seems to be a
remote chance based on the magnitudes of the MLCAPE.


.SHORT TERM...(Tuesday night through Thursday)
Issued at 324 PM EDT Mon Jun 19 2017

...Briefly drying out midweek...

High Impact Weather Potential: Chance of thunderstorms Thursday
through Thursday night.

Pattern Forecast: Broad/weak upper level troughing continues across
the eastern third of the CONUS Tuesday evening with the last in a
series of shortwaves progressing east across the forecast area.
Subtle shortwave ridging and attendant bubble of high pressure
briefly works its way atop the Great Lakes Tuesday night - Wednesday
before heights gradually lower Thursday ahead of vertically stacked
low pressure trekking eastward across southern Canada. This combined
with a subtle perturbation cutting across the central plains will
combine for renewed shower and thunderstorm chances late Wednesday
night/early Thursday through Thursday night.

Primary Forecast Concerns/Challenges: Shower/thunderstorm arrival
timing late Wednesday night - Thursday.

Any lingering isolated showers east of I-75 Tuesday evening are
expected to end quickly as any mentionable forcing and mid level
moisture ahead of Tuesday afternoon`s shortwave slides into southern
Ontario. Subtle height rises will be the rule for the remainder of
Tuesday night, along with surface high pressure nosing into the
region...becoming briefly centered across the western Great Lakes
during the the day Wednesday. Mostly sunny skies, light winds and
near-normal temps will lend themselves to a nearly picture perfect
first day of astronomical summer.

High clouds will begin to increase late in the day Wednesday,
primarily across western areas, ahead of the next system approaching
from the west. Return flow will be ongoing Wednesday evening as low-
mid level winds gradually shift southwesterly allowing deep layer
moisture to increase (evident by PWs progged above 1.50 inches
across northern Lower by Thursday morning). A thickening/lowering
cloud deck will be the rule after sunset along with showers arriving
west of I-75 as early as sunrise Thursday, spreading eastward across
the forecast through the mid-morning hours. Some of the showers
could be heavy at times with aforementioned deep moisture (PWs >
1.50 inches, K-Index in the mid-30s) as forcing maximized along the
system`s warm front is expected to lift across northern Michigan
through the early morning hours Thursday. This certainly supports
WPC`s Day 3 outlook for excessive rainfall across the far
southwestern counties of the CWA, which is an area that`s already
received 1-3 inches above June`s normal-to-date rainfall. Rainfall
diminishes in coverage and intensity by the midday hours Thursday,
although additional scattered showers and a few thunderstorms will
remain possible through Thursday evening as a cold front is quick to
follow but aids to focus any additional heavier precip downstate
into the Ohio Valley.

.LONG TERM...(Thursday night through Monday)
Issued at 324 PM EDT Mon Jun 19 2017

High Impact Weather Potential...None.

Initial zonal flow pattern aloft won`t last for long as some mid-
level energy coming ashore British Columbia quickly leads to a
developing broad trough over the northern CONUS by the weekend. This
will lead to another somewhat unsettled weather pattern at times for
northern Michigan through the long term period.

Friday morning a cold front will be exiting our southeastern CWA
with a few lingering showers quickly coming to an end as drier air
encroaches behind the front. It appears most of northern Michigan
will be largely dry Friday through Saturday morning. Forecast
details become a little murkier thereafter as some model differences
begin to creep in. The rest of Saturday may very well be mostly dry
across most of northern Michigan as suggested by the ECMWF and
Canadian, but the GFS has a shortwave crossing the area that could
perhaps generate a few showers and maybe a storm or two. For
Saturday night into Sunday, the ECMWF was wanting to bring a
stronger shortwave across the Northern Plains that would lead to a
decent developing surface low tracking through the Lower Peninsula.
However, with the 19.12Z run, the ECMWF has come more in line with
the GFS and Canadian, with only broad upper troughing over the Great
Lakes and a weak surface low. Nevertheless, this system looks to
bring the best shot for some substantial rainfall coverage through
this period of the forecast. We look to dry out Sunday night as a
surface ridge extends into the area but perhaps will see a few
diurnal showers on Monday.

Temperatures look to drop back below seasonal normals by the weekend
as the upper trough moves overhead. Perhaps even some readings in
the upper 40s Sunday night.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 221 PM EDT Mon Jun 19 2017

Showers and Thunderstorms will continue, mainly on the east side
of the state as the upper level low and the daytime heating
continue today. One thing noted is that the west side of the state
is having a bit of a "lake shadow" helping to keep the convection
down a bit until it gets in the vicinity of I-75. As we lose the
heating in the evening, the showers will diminish to some very
isolated showers that shouldn`t impact the TAF sites overnight.
Tuesday looks to be similar with the west side with limited
convection and the east side with the convection again. So expect
the better chances of showers and thunder on the east side with
the better chances for MVFR CIGs as well.


Issued at 324 PM EDT Mon Jun 19 2017

Tonight through Wednesday...The sfc low that has been in the Upper
Great Lakes will begin to move out of the region to the northeast
tonight. As it does the pressure gradient will slacken and remain
that way through Wednesday. Therefore the winds are expected to be
10 knots or less through the day on Wednesday, with a few gusts to
15 knots during the day.




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