Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 251801
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
201 PM EDT Sun Jun 25 2017

.UPDATE...
Issued at 1032 AM EDT Sun Jun 25 2017

Not much change from the early morning discussion and forecast.
Upper low now moving across Lake Huron, with a smaller scale wave
spinning in and around Manistee. Both are focusing the better
scattered shower activity, which is already showing an uptick in
coverage this morning. Will focus best chances for picking up
additional rains with these features for the next few hours, but
as we transition into afternoon, can see diurnal processes and
lake breeze/frontal boundaries taking over the focus of where
showers will be. This suggests that westerly flow into NW lower
ought to see lower shower chances and perhaps more sun, while the
frontal zone in eastern upper along with lake breeze convergence
there and across NE lower will have the greatest shower activity.
As far as thunder, these two areas also will have the greatest
instability, as modified RUC soundings suggest skinny MLCAPES
around 3-500 j/kg and perhaps up to 1000j/kg in interior eastern
upper. Think this is more of an isolated thunderstorm scenario,
with much less in the way of upper level support, as was the case
yesterday. Severe chances pretty slim to none. Small hail will
certainly be possible though.

&&

.NEAR TERM...(Today through Tonight)
Issued at 433 AM EDT Sun Jun 25 2017

...Periodic showers today and cool for late June...

High Impact Weather Potential: Minimal...a few thunderstorms this
afternoon/early evening.

Pattern Synopsis/Forecast: 06z surface/composite analysis shows a
roughly east-west oriented front laying across Upper Michigan and
extending into southern Quebec.  Upper low spinning across the upper
Great Lakes early this morning...moving into western Lower Michigan.
Nicely defined deformation zone to the north of this upper low has
an attendant band of rain arcing from northeast Wisconsin...across
central/eastern Upper Michigan and across northern Lake Huron.
Scattered showers also closer in to the main circulation/cold pool
over northwest Lower...did have some lightning with it earlier over
Lake Michigan but no strikes recently (as of 0715z).  500mb
temperatures around -24C within the center of the low...an
impressive 3 standard deviations below the mean for late June. Water
vapor imagery shows another well-defined vorticity center dropping
south across Lake Winnipeg...with another southeast digging short
wave trough over southern Saskatchewan.

Upper low making nice eastward progress across the Lower Peninsula
early this morning...and will track into the lower Great Lakes this
afternoon while trailing short wave trough over Manitoba follows
quickly on its heels into the upper Lakes tonight.  Cold front
across Upper Michigan doesn`t appear to move much today as overall
gradient is rather weak...but a surface response to the second wave
is expected to form over the state tonight.

Primary Forecast Concerns: Initial area of rain associated with
deformation zone expected to tend to thin out as the morning
progresses...IR imagery already showing cloud top warming across
northeast Wisconsin.  Scattered showers will accompany the passing
upper low across northern Lower early this morning...and though
upper level support will slide east this afternoon...some skinny
instability will allow for some spotty convection to develop with a
bit more focus along the Lake Huron and southeast Upper Michigan
lake breeze boundaries.  Cooler than normal temperatures will also
be notable today...with temperatures hanging mainly in the 60s
(normal highs in the mid-upper 70s).

While this activity wanes during the evening...another round of rain
will arrive from the west with the next short wave trough.  Best
chance for rain tonight likely across Upper Michigan and leaking
into northwest Lower.

&&

.SHORT TERM...(Monday through Tuesday)
Issued at 433 AM EDT Sun Jun 25 2017

...Cool, showery Monday then drying out and warming up...

High Impact Weather Potential...Minimal. Small chance for a
thunderstorm or two on Monday.

Pattern Synopsis/Forecast...Deep longwave trough will remain over
the Upper Great Lakes through Monday night. A potent shortwave will
briefly evolve into a closed upper low as it passes over the Lower
Peninsula on Monday, changing back to an open wave as it crosses
Lake Erie. Some additional weak mid level energy will stream in
behind this shortwave Monday night, followed by another weaker
shortwave dropping through eastern Ontario on Tuesday that may
/just/ brush eastern Upper. Beneath the closed low, a weak surface
low and cold front will drift across northern Michigan on Monday,
providing some additional forcing. Large surface high will slide
into the middle Mississippi Valley by Tuesday morning, with a ridge
building over northern MI Monday night. Meanwhile, a flattening
upper ridge over the Plains will make some eastward progress during
the day on Tuesday, providing some additional subsidence and a
transition to warm air advection.

Primary Forecast Concerns...Temperatures and rain chances on Monday
will be the main forecast challenge. With the cumulative cooling
trend from the weekend continuing into Monday, expect temperatures
will find it a little harder to recover during the day following
morning lows in the mid 40s to low 50s. Despite expected mostly
cloudy skies and healthy shower activity that will limit daytime
heating, raw deterministic guidance looks a bit on the cool side.
Ensemble members show a fair amount of spread in forecast highs, but
means are generally in the upper 50s to low 60s which looks more
reasonable and is also in line with MOS guidance. Regardless, Monday
will be a cool day by late June standards...a good 10-15 degrees
below normal.

Showers are expected to be scattered to numerous during the day
Monday as the vertically stacked low moves through the area.
Forecast soundings show a nearly saturated column through the mid
levels, and there will likely be a small amount of CAPE (a few
hundred J/kg) that develops. This may be enough for a thunderstorm
or two over mainly northern Lower, but think storm chances will be
considerably lower than this weekend given very limited instability
and weaker low level lapse rates.

.LONG TERM...(Tuesday night through Saturday)
Issued at 433 AM EDT Sun Jun 25 2017

High impact weather potential...Thunderstorms possible at various
times from Wednesday afternoon through Saturday.

Flattening upper ridge upstream will slide into the Upper Great
Lakes Tuesday night into Wednesday. At the same time, some weak mid
level energy associated with a shortwave over Ontario will probably
brush eastern Upper, and there is a small chance this could trigger
a shower or two. Otherwise better rain chances will hold off until
Wednesday afternoon as a developing low over Minnesota interacts
with strong Gulf moisture advection. With models coming into good
agreement, confidence is increasing in the potential for heavy
rainfall across northern Michigan Wednesday evening as a warm front
and robust ~50 knot low level jet nose their way through the region.

The remainder of the week also looks fairly active as a few
shortwaves ripple across the northern CONUS and interact a steady
stream of moisture coming from the Gulf. Considerable uncertainties
for the late week period, but models are hinting at the possibility
of another stronger system sometime in the Friday to Friday night
timeframe. Temperatures look to be near or just a tad below normal
through the period.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 156 PM EDT Sun Jun 25 2017

Fairly widespread shower activity across nrn lower Michigan, with
most of the action to impact APN through the day/early evening.
Showers were popping off near/just east of the NW lower airports
and strengthening some as they track eastward. Maybe some thunder
at APN a few times into this evening. Small hail a possibility.
Could have a bit of a break in the showery activity this evening,
before they become more numerous later tonight and through Monday
with the approach of weak low pressure and low level troughing.
Winds will be light and variable through tonight, with some bit of
gustiness possible at TVC/MBL tomorrow out of the WNW after the
low pressure slides east.

&&

.MARINE...
Issued at 433 AM EDT Sun Jun 25 2017

No major issues today into this evening as pressure gradient will be
light and winds will be locally dominated by lake breeze components.
Surface low development over northern Michigan overnight in response
to upstream short wave trough will allow for stronger northwesterly
winds to develop on Lake Michigan heading into Monday.  Wind gusts
may be sufficient to require Small Craft Advisories Monday
afternoon/evening along the northwest Lower nearshore zones.


&&

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

$$

UPDATE...SMD
NEAR TERM...JPB
SHORT TERM...MEK
LONG TERM...MEK
AVIATION...SMD
MARINE...JPB



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