Area Forecast Discussion
Issued by NWS Gaylord, MI

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510
FXUS63 KAPX 281807
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
207 PM EDT Sun May 28 2017

.UPDATE...
Issued at 1046 AM EDT Sun May 28 2017

Latest GOES-16 imagery reveals a collection of updrafts rapidly
initiating over the Tip of the Mitt as convective activity
becomes surface based. Interior northern Lower temperatures are
rising into the upper 60s (even some low 70s) already, so the
convective temperature will soon be reached across the rest of
northern Lower. The 12Z APX sounding shows a respectable CAPE
profile above the surface inversion with PWATs around 1". Thus,
conditions are ripe for shower and thunderstorm development late
this morning tied to some weak energy aloft passing overhead. The
main band of showers and storms, tied to the approaching deep
mid-level trough, is currently crossing Lake Michigan. A line of
showers/storms has developed just ahead of the main precip shield
due to low level convergence and is already making landfall
around Manistee. The activity will continue to track northeast
across northern Michigan through this afternoon as the upper
trough pivots across the area. Synoptic models all point to a QPF
bullseye over far northeast Lower and eastern Chip/Mack counties.

This main round of showers/storms should largely clear far eastern
Upper and northeast Lower by around 6pm (give or take) but hi-res
models hint at the possibility of convergent lake breezes perhaps
triggering another smaller band early this evening almost along
I-75. So, expect areas west of I-75 to dry out first late this
afternoon or early evening with the drying line progressing east
through midnight. There may even be a bit of clearing in our
southwestern counties late today. With this update, have refined
sky cover and timing of PoPs to reflect latest trends and hi-res
guidance. Rest of the forecast remains largely on track with only
minor cosmetic adjustments made.

&&

.NEAR TERM...(Today through Tonight)
Issued at 352 AM EDT Sun May 28 2017

High impact weather potential: Possible thunderstorms. Severe storms
not expected.

Pattern synopsis and forecast:

Upper level and sfc low pressures were slowly drifting through
Ontario, with it`s associated cold front draped southward through MN
and the Dakotas along larger scale upper troughing. Scattered
showers were common across nrn MN along the front, and ahead of a
clearly defined vorticity maximum seen on latest satellite imagery.
There was also some light rains/showers that were trying to get
going along another sheared out wave lifting through the western
Great Lakes, with even some earlier sporadic rumbles of thunder
across eastern Lake Superior. Not very strong forcing across the
region, outside of DPVA with the upper troughing and weakish low to
mid level warm advection, but clouds were expanding with cooling
cloud tops across nrn Michigan/Wisconsin. All of the real active
weather was well south of us, in the deeper instability and
associated with sfc low pressure from the low to mid Mississippi and
Ohio river valleys.

Large scale upper troughing sharpens up through the day across the
western Great Lakes as the one clearly defined vorticity maximum
wraps into far western Lake Superior, and as another wraps back into
MN. DPVA increases across nrn Michigan out ahead of the system cold
front which arrives tonight. See no reason clouds will do anything
but increase/thicken up through the day and evening with showers
developing into a nice band/swath just ahead of the front and upper
troughing. Instability will be lacking, with models doing what they
do best, in overdeveloping SBCAPE/MLCAPE. Can foresee a few hundred
j/kg with lapse rates aloft steepening to 6.5c/km later this
afternoon/evening for some embedded thunderstorms. The forcing and
deeper moisture will depart by later this evening, with the upper
low re-positioning itself over western Lake Superior late tonight.
Stronger energy does try to sneak in late, but any precipitation
will remain out west of nrn Michigan.

High temperatures in the upper 60s to lower 70s with lows tonight
generally in the upper 40s to lower 50s.

&&

.SHORT TERM...(Monday through Tuesday)
Issued at 352 AM EDT Sun May 28 2017

...Showers and Thunderstorms Then cooler...

High Impact Weather Potential...Thunderstorms Monday afternoon,
although at this point they don`t look to be severe.

Pattern Synopsis/Forecast...The 500 mb low is over the Upper Great
Lakes Region Monday morning, and it slowly moves to the northeast to
south of James Bay by Tuesday evening(00z/Wed), where it remains
through the night.

As with any upper level low, this will be activated by the diurnal
heating cycle, kicking off the showers and limited thunderstorms
Monday afternoon as the 500 mb temperatures fall to less then -20c
producing a mid level lapse rate (700-500 mb) of about 7 C/km. We
lose the heating overnight, and with the upper low moving northeast
out of the forecast area, the rain will taper off.

Tuesday morning will start quiet enough, but showers are expected to
become scattered again as the cool air of the 500 mb low rotates
over the region, but with the center of the low now a couple hundred
miles to the NE, will expect rain showers as the mid level lapse
rates fall to around 6 C/km. As the day draws to a close, and the
low moves a little more NE the rain showers will become isolated, or
even dry out Tuesday night into Wednesday morning.

Primary Forecast Concerns...Considering the amount of stratocu that
should be associated with this system, the CAPE during Monday
afternoon is a few hundred J/kg on both the GFS and the SREF and the
shear is less than 30 knots. So will expect that there will be some
thunder activity, but nothing severe Monday afternoon, and with the
trend of the CAPE even lower on Tuesday, that thunder is not
expected, just rain showers.

.LONG TERM...(Tuesday night through Saturday)
Issued at 352 AM EDT Sun May 28 2017

...Below Normal Temperature Trend...

High Impact Weather Potential...None

Extended (Wednesday through Saturday)...Wednesday, the upper low
continues to move NE, but a new impulse begins to dive into the weak
500 mb trough, upstream  in northern Manitoba. So rain will probably
move through the forecast area Wednesday afternoon, and then dry out
Wednesday night. As the low dives into the Upper Great Lakes, the
models disagree on the evolution of the low, itself, but not the
result, rain showers Thursday afternoon. The GFS suggests the low
cuts off to the north of Lake Superior and continues the rain
showers into Friday morning. However, that`s where the models begin
to differ. The 500 mb low on the ECMWF is north of New England,
while the GFS has it north of Lake Superior. The GFS produces rain
showers through the early evening, while the ECMWF is dry from the
afternoon and overnight. Saturday, rain moves up from the SW with a
secondary sfc low moving into Wisconsin on the ECMWF while it
remains dry on the GFS. Not sure which model has the better
solution, so have gone closer to the GFS, being dry, so that we
don`t get an overly wet forecast from the differing solutions.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 207 PM EDT Sun May 28 2017

Band of showers continues to lift northeast across northern MI
with scattered thunderstorms just out ahead. Heavier downpours
reducing visibilities and ceilings down to IFR at times. Expect
thunderstorms are pretty much over for KMBL, KTVC, and KPLN as
leading edge of the activity is now advancing into northeast
Lower, so KAPN will stand the best chance for any thunder the
rest of this afternoon. Hi-res models show the bulk of rain
clearing out of the western terminals by around 21Z and out of
KAPN by around 23Z. There could be a lingering isolated light
shower or two behind this main batch of rain through early
evening as a boundary approaches from the west.

Clearing line evident on satellite now over western Lake Michigan
will creep into northern Lower towards evening with partial
clearing possible for KMBL, KTVC, and possibly KAPN overnight.
With today`s rainfall, this would set the stage for some
radiation fog overnight with MVFR vsbys possible, mainly for KAPN
and KPLN where SW winds will be a tad lighter. Scattered showers
and possibly a storm or two expected on Monday with SW winds
becoming a bit gusty towards afternoon.

&&

.MARINE...
Issued at 352 AM EDT Sun May 28 2017

Low pressure slowly drifts through Ontario through Monday, with the
pressure gradient remaining loose through this evening, with
relatively light flow and developing lake breezes this afternoon.
The gradient tightens up late tonight into Monday with a chance for
some low end advisory level gusts through Tuesday.


&&

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

$$

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



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