Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 191736
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
136 PM EDT Sat Aug 19 2017

.UPDATE...
Issued at 1056 AM EDT Sat Aug 19 2017

Thickest of the synoptic cloud cover has exited to the east. Cu
field is sprouting away from Lake MI, and a n-s oriented band of
altocu is also progressing across eastern upper and far northern
lower MI. Background synoptic nw to w surface winds are
decreasing, and that trend will continue as low pressure over
Quebec moves away. In fact, given the position of the low and high
(far sw WI), the lowering of pressures over land areas with
diurnal heating will act to further loosen the pressure gradient
over northern MI.

It will still take time to overcome the synoptic wind and generate
a lake breeze in ne lower MI. In fact, the most recent run or two
of the HRRR still initiate convection there, but not until 4-6 pm.
HRRR pretty consistently indicating that upper MI will be more
active - especially central upper MI. There is also consistency in
bringing some remnant showers to parts of nw lower MI.

Much of the above is reflected in the going forecast. However,
some timing adjustments are in order: pushing pops in ne lower MI
to a little later in the day, and speeding up the potential for
showers to reach nw lower MI to as soon as 6pm.

&&

.NEAR TERM...(Today through Tonight)
Issued at 245 AM EDT Sat Aug 19 2017

High impact weather potential: A thunderstorm in lake breeze
convergence today?

Pattern synopsis and forecast:

Upper level troughing was directly overhead early this morning,
while more pronounced ridging was over the nrn plains. At the sfc,
low pressure was in western Quebec and was continuing to track east,
but low level cyclonic convergence/sfc troughing was still stubborn
to depart. This has resulted in a prolonged period of low level
clouds and spits of light rain across nrn Michigan. In addition, mid
and upper level clouds were also pushing into the region, associated
with the upper level troughing. All this cloud has kept temperatures
from falling, remaining in the upper 50s to lower 60s most areas.

Not much going on in weather today through tonight. Can certainly
see mostly cloudy skies through at least a portion of the morning
hours past daybreak, as well as spits of light rain. With the
further eastward progression of the sfc low, passing upper trough,
and incoming higher pressure, skies will gradually allow some sun to
appear. Believe that low level moisture is still plenty enough to
result in a decent coverage of cumulus, especially in interior
eastern upper and far NE lower where lake breeze convergence is
expected. In addition, modifying RUC/GFS fcst soundings, 200-600j/kg
of MLCAPE is revealed. Can see maybe some isolated showers with an
outside shot at a weak/garden-variety thunderstorm in these areas.
Of course, we have to get the warming today from the sun.

Other showers may be able to drift down into NW lower this evening,
generated from lake breezes in far NE WI/central upper. Not much in
the way of help aloft in sustaining any precipitation, but there is
at least some indication of weak vorticity in the NW flow aloft.
Plus, the lakes are relatively warm with some BL instability holding
through evening. Otherwise, skies will decrease in clouds overnight,
with only some higher level cloud possible.

High today in the middle 70s most areas with lows in the upper 50s
and lower 60s tonight.

&&

.SHORT TERM...(Sunday through Monday)
Issued at 245 AM EDT Sat Aug 19 2017

High Impact Weather Potential: Minimal.

Pattern Forecast: Low amplitude ridging on Sunday gives way to
increasingly unsettled weather early next week with a frontal
boundary sliding into the Great Lakes.

Primary forecast challenge:  Shower and thunderstorm chances Sunday
night into Monday.

Fairly quiet weather during the daylight hours on Sunday with return
low level flow developing as high pressure slowly slides to the
southeast of the area.  This will push warmer H8 air into the Great
Lakes, with high temperatures into the 80s in many areas. Upstream
trough/frontal boundary sags toward the western lakes/upper Michigan
Sunday night. Moisture pooling in vicinity of the boundary, with
theta-e axis folding southward through upper Michigan and toward the
Straits. With modestly steep mid level lapse rates and increasing
amounts of deep layer moisture, showers/storms will become more
numerous over upper Michigan and northwest lower Michigan.

Front remains draped across northern lower Michigan on Monday (sorry
eclipse viewers), with plenty of clouds and scattered showers/storms
with additional ripples of shortwave energy riding along it.  A warm
and humid day, with dewpoints well into the 60s (possibly
approaching 70 degrees over southwest parts of the area).  Despite
the clouds/pcpn...temperatures still into the 80s in many areas.

Eclipse viewing forecast...Not very good for much of northern
Michigan with frontal boundary in the area bringing mostly cloudy
skies.  The best viewing in the state likely over southeast Michigan
where less clouds are expected.

.LONG TERM...(Monday night through Friday)
Issued at 245 AM EDT Sat Aug 19 2017

Frontal boundary and weak surface low will push through the Great
Lakes Monday night into Tuesday.  There are still some question
marks between the models as to the speed of the frontal boundary and
the strength of the surface reflection riding along it.  Will carry
high rain chances Monday night into Tuesday (especially northern
lower), with locally heavy rain a possibility given deep layer
moisture in place (PWATs nearing 2 inches).  Another shot of very
cool late summer air takes hold for the middle and end of the week.
There could even be some lows in the 30s in the typically cooler
locations for the end of the week under ideal radiational cooling
conditions.  A few showers still likely on Wednesday, with drier
conditions expected for the end of the week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 135 PM EDT Sat Aug 19 2017

VFR.

Cu field blossoming away from Lake MI. Could well see a few
showers pop up in ne lower MI thru early evening, though chance
for APN to be directly impacted is too low to include a mention in
the TAF. Cu fades away tonight, though not before some convective
remnants move se from central upper MI toward the TVC area. Have
not included any mention of fog tonight, as pressure gradient may
be just enough to keep things slightly stirred. If not, some fog
may appear at any site but TVC.

Ongoing w to nw breeze will diminish tonight, and pick up out of
the sw by late morning Sunday.

&&

.MARINE...
Issued at 245 AM EDT Sat Aug 19 2017

Low pressure in western Quebec will press eastward today, being
replaced by higher pressure through tonight and into Sunday. A slow
moving cold front will then press into Lake Superior Sunday and
Sunday night. Remnant gusty westerly flow with some low end advisory
gusts through daybreak in and around Presque Isle Light, will
gradually swing around more southerly while weakening later today
and tonight. Light southerly flow increases through the day Sunday
and Sunday night, but no advisories expected at this time.


&&

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

$$

UPDATE...JZ
NEAR TERM...SMD
SHORT TERM...JK
LONG TERM...JK
AVIATION...JZ
MARINE...SMD


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