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000
FXUS63 KAPX 230731
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
331 AM EDT Fri Jun 23 2017

.NEAR TERM...(Today and Tonight)
Issued at 1237 AM EDT Fri Jun 232017

...Widespread showers and thunderstorms end this morning...

High impact weather potential...Still some heavy rain concerns
through early this morning.

Pattern synopsis/forecast...Convective cold pool augmented cold
front making slow southeast progress into central lower Michigan at
this early hour. Heavy rain producing thunderstorms broke out along
and just ahead of this front, mostly across central lower Michigan
(a good 75 miles south of what nearly all of last nights guidance
indicated). Core of upper level forcing tied to robust jet core
bringing mostly lighter showers further north. Strong mid level
shortwave trough and attendant surface low pinwheeling east into
western Ontario, with secondary vort max extending south into the
northern Mississippi Valley. This vort will race east and shear out
in the process, with it and eastward progression of upper jet core
forcing a much quicker east exit to the cold front and overhead deep
moisture plume this morning. A much less moist airmass will follow,
quickly ending the rain threat this morning, and bringing much
quieter weather through tonight.

Primary forecast concerns/challenges...Addressing lingering heavy
rain concern early this morning.

Details...Still will be dealing with convection through early this
morning, with the focus for much of the stronger activity expected
to be down near Saginaw Bay. Overnight storms have easily produced
inch per hour rainfall rates across central lower Michigan, and see
no reason not to see similar rates in the far southeast yet for a
time this morning. Storms have remained transit, so expect rainfall
totals to not get too out of hand. Still, given such rainfall
efficiency, would expect to see ponding on area roadways and poor
drainage areas. Drier air makes steady southeast progress later this
morning into this afternoon, spreading across all our area by later
today. May see just enough lingering moisture to kick off a few
diurnally driven light showers across northeast lower Michigan late
this morning and early afternoon. Cool air aloft and lake augmented
secondary surface trough/zone of enhanced convergence might do the
same this afternoon across eastern upper. Dry condtions expected
elsewhere after this mornings lingering activity. Temperatures will
not be too far off from those experienced yesterday, but it will
feel more comfortable as dewpoints begin to tank this afternoon.

Dry conditions expected tonight as northwest flow continues. A
noticeable cooler night with temperatures ranging in the upper 40s
to middle 50s. May see a bit of patchy fog in those sheltered low
lying areas.

&&

.SHORT TERM...(Saturday through Sunday)
Issued at 328 AM EDT Fri Jun 23 2017

...Unseasonably cool with shower chances...

High Impact Weather Potential...Minimal, but a few non-severe
thunderstorms possible Saturday and Sunday afternoons.

Pattern Synopsis/Forecast...Active ~100 knot upper jet will meander
south into the Ohio Valley, carving out a broad longwave trough
over the Great Lakes this weekend. This will keep an unsettled
weather pattern going and also allow an unseasonably cool airmass
(by late June standards) to establish itself over the region into
early next week; temperatures aloft from 925mb to 700mb will drop
to 1 to 3 standard deviations below the mean. Cold air advection
will continue in earnest on Saturday, though it will gradually
weaken with time as the 1000-500mb thickness gradient slowly
relaxes. Resultant steep low/mid level lapse rates will allow for
some diurnal shower activity as daytime instability develops. A
closed upper low will rotate across the Upper Midwest, crossing the
Lower Peninsula Saturday night into Sunday morning. This will
provide a little better forcing, but somewhat limited moisture will
make it tough to generate any decent rainfall coverage across
northern Michigan. Additional shortwave energy combined with steep
lapse rates will allow for more diurnal shower activity Sunday
afternoon into early evening.

Temperatures will be around 10 degrees below normal over the weekend
with highs in the 60s to around 70 both days, though slightly cooler
Sunday. Lows Saturday night will dip into the upper 40s inland.

Primary Forecast Concerns...Rainfall coverage and thunder chances
over the weekend will be the main forecast challenge. SPC sounding
climatology for APX shows our expected PWATs hovering around 0.8
inches to be right on par with the mean for late June. So, moisture
will be adequate but not impressive. With only weak to moderate
synoptic forcing through the weekend, however, think rainfall
coverage will be limited to scattered. The NAM does show a stronger
vort max generating heavier QPF that comes ashore northwest Lower
Saturday night, but think it is overdone. Surface trough with weak
low level confluent wind pattern will hang out just north of the
Straits on Saturday, providing a little more enhanced lift there.

Despite the anomalously cool airmass overhead, the strong resultant
low/mid level lapse rates will yield MLCAPEs of several hundred J/kg
Saturday and Sunday afternoons (highest over northeast Lower). This
may lead to a few pulse thunderstorms with perhaps some small hail
and gusty winds, but lack of deep layer shear should preclude any
severe threat.

&&

.LONG TERM...(Sunday night through Thursday)
Issued at 328 AM EDT Fri Jun 23 2017

High impact weather potential...Minimal, but some thunderstorms
possible Wednesday afternoon into Thursday.

Broad upper trough and unseasonably cool conditions will remain over
the Great Lakes heading into Monday with continued shower chances.
By Tuesday, however, upper ridge over the western CONUS and
surface high pressure over the middle Mississippi Valley will shift
eastward. Despite the upper ridge flattening out as it moves
overhead, northern Michigan should enjoy a rare dry day on Tuesday
with plenty of sun, not to mention a strong boost in temperatures
as warm air advection ramps back up. Models track a developing
surface low from the Northern Plains into Ontario Wednesday into
Thursday. Still plenty of uncertainties with this system`s timing
and track, but it looks to bring a return to showers and
thunderstorms for northern Michigan. A tight pressure gradient will
also lead to breezy south/southwest winds Wednesday and Thursday
afternoons, allowing for near normal temperatures.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1150 PM EDT Thu Jun 22 2017

Showers/storms overnight, departing late into Fri morning.

Cold front pushing into eastern upper MI late Thu evening, and
will continue across northern lower MI overnight. Showers/t-storms
will continue at times ahead of the front, impacting primarily MBL
and to a lesser degree TVC/APN. Expect a period of lower cigs
overnight as the front passes, though less so than earlier
thought (no worse than MVFR). Cigs will improve on Friday to VFR.

Westerly winds, veering nw into Fri evening. May get a bit gusty
Fri afternoon, especially at PLN.

&&

.MARINE...
Issued at 328 AM EDT Fri Jun 23 2017

Gradient winds and waves not expected to be of any issue over the
next several days. Cold front finishes crossing the area this
morning, with winds become west behind it. Winds are expected to
remain west to northwest right through the upcoming weekend. Just
a few showers linger about parts of the area today, with showers
and perhaps a rumble of thunder becoming a bit more commonplace
both Saturday and Sunday afternoon.

&&

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

$$

NEAR TERM...MSB
SHORT TERM...MEK
LONG TERM...MEK
AVIATION...JZ
MARINE...MSB