Area Forecast Discussion
Issued by NWS Gaylord, MI

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000
FXUS63 KAPX 220245
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
1045 PM EDT THU JUL 21 2016

.UPDATE...
Issued at 1012 PM EDT Thu Jul 21 2016

Other than a rather thick cirrus deck from convection in southern
Wisconsin/northern Illinois, nothing happening across northern
Michigan. Recent HRRR runs continue to suggest a thin corridor of
showers will develop and move through northern lower Michigan over
the next few hours, along the northern edge of instability
gradient that will fold down through the region. But, not buying
it at this point and have removed pops from the forecast for the
overnight hours.

UPDATE Issued at 740 PM EDT Thu Jul 21 2016

Behind our line of storms that rolled through earlier in the day,
secondary instability axis has redeveloped across eastern
Wisconsin, pointing up into the U.P. and ahead of subtle surface
trough that meanders from central upper Michigan down through NW
Wisconsin. Several clusters of storms have formed in central
Wisconsin in the last few hours which are diving southeastward
toward Chicago along the tight gradient of instability. Up this
way, we`ve seen a couple showers pop down near Ludington, possibly
along some old outflow. But high resolution guidance continues to
suggest a few showers/storms may yet pop this evening and into the
overnight hours across northern lower Michigan as the secondary
instability folds down into the region. I`m skeptical however, as
ongoing convection in Wisconsin may dominate. But will see.

&&

.SHORT TERM...(This evening and overnight)
Issued at 355 PM EDT Thu Jul 21 2016

Overview...Convective line of showers and thunderstorms that
prompted the watch earlier today is now offshore into Lake Huron. To
the west is a weak sfc trough with a small cluster of thunderstorms
in the Upper Mississippi Valley, that is attached to a sfc low near
James Bay. At 500 mb there is relatively flat flow over the northern
tier of states from the N Plains to New England, with relatively
weak shortwave troughs moving through the flow.

A little further to the west is another area of high pressure, in
the N Plains.

Tonight...main concern is the sfc trough that is expected to cross
the forecast area overnight. some models have been showing another
line of showers and thunderstorms to move over the region. however,
there are a few models, that show little happening overnight. One in
particular (HRRR) which handled the event much better than the rest
which shows that little happens. So have some low chance pops as the
trough moves through overnight. Otherwise, the trough moves through,
and the dewpoints begin to fall, as high pressure builds into the
region by 12z.

.LONG TERM...(Friday through Thursday)
Issued at 355 PM EDT Thu Jul 21 2016

High impact weather potential: Lingering heat. Potential for more
stormy weather to end the weekend.

Pattern synopsis/expected evolution: Massive central plains heat
dome begins to feel the affects of rather aggressive/progressive
flow across southern Canada and the northern CONUS in the coming
days...essentially squashing the northern extent of the ridge axis
this weekend. Weak front sags south in the process, shunting current
active weather regime to our south to start the weekend and bringing
a shot of somewhat drier air overhead in the process.
Soupy/unstable airmass does not go far however, with a fast moving
wave trying to surge it back north into the northern Lakes to end
the weekend. Not sure if it will ever make it, although its
attendant mass adjustment will likely result in another round of
showers and thunderstorms, some of which could be rather
significant.

Primary forecast concerns/challenges: Temperature trends through
Saturday. Shower and thunderstorm evolution Saturday night and
Sunday.

Details: Definitely still warm to end the week on into the start of
the weekend (plenty of sun sure won`t hurt the cause), although not
quite as moist at the lower levels. Simple thermal progs supports
highs into the lower/middle 90s over much of northern lower Michigan
Friday, and just a couple degrees cooler on Saturday.
As mentioned, humidity values will not be quite as high as those
observed today, especially by Saturday. Expect apparent temperatures
to mimic those of the actual highs, negating any type of heat
advisory concerns.

Next chance for showers and thunderstorms arrives later Saturday
night into Sunday as the next fast moving wave (perhaps convectively
agitated) arrives, bringing with it the northern extent of one very
juicy corn belt centered airmass. Still plenty of details to work
out, as is always the case when dealing with convection. Really hard
to get into any specifics, with expected upstream convection likely
playing absolute havoc with what unfolds over our area. Will simply
load that which a consensus blend approach gives, highlighting
greatest shower and thunderstorm concern on Sunday. Marginally fast
mid level flow and what could be some decent instability does raise
some concern for severe weather. Will definitely continue to monitor
trends in the coming days.

Extended (Monday through Thursday) issued at 300 PM EST THURS Jul 21
2016

To begin the work week there is an upper level low at 500mb in NE
Ontario moving out. The flow behind behind the low turns to a zonal
flow before a subtle wave slides through on the day Thursday.
This pattern will provide some relief from the hot conditions of
last week while still keeping Northern Michigan in the seasonable
temp range.

At the surface Monday through Wednesday looks quieter with the zonal
flow aloft and a sfc high pressure moving in from the plains.
Thursday the pops increase as the wave moves through resulting in
some isolated showers. Overall set up looks too weak to produce any
thunderstorms.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 1045 PM EDT Thu Jul 21 2016

Mainly VFR conditions anticipated through the TAF forecast period.
Thick high cloud cover will be found across northern lower
Michigan through the overnight hours but thin out toward morning.
There may also be some lower cloud cover (around 3K bases) found
across the region overnight, but should have minimal impact at the
terminal sites.

Otherwise, diminishing winds anticipated tonight. Winds will
increase again on friday with some westerly gusts into the high
teens to lower 20 knot range.

&&

.MARINE...
Issued at 355 PM EDT Thu Jul 21 2016

Tonight Through Saturday...Winds will continue into the evening with
the small craft criteria, with the waves subsiding by 06z. After 06z
through Saturday, high pressure builds into the region and relaxes
the gradient. Winds and waves are expected to remain below small
craft criteria.


&&

.APX Watches/Warnings/Advisories...
MI...NONE.
LH...NONE.
LM...NONE.
LS...NONE.
&&

$$

UPDATE...Adam
SHORT TERM...JSL
LONG TERM...MSB/Mayhew
AVIATION...Adam
MARINE...JSL



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