040
FXUS63 KAPX 121758
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
158 PM EDT Sun May 12 2024

.KEY MESSAGES...

- Thunderstorm potential late this afternoon into tonight. A few
  strong/severe storms possible, mainly this evening.

- Continuing rain/thunderstorm chances for central Lower Monday/
  Monday night.

- Rain chances return Thursday and beyond.

&&

.UPDATE...
Issued at 1128 AM EDT Sun May 12 2024

Current forecast remains on track as showers work across parts of
northern Michigan. These showers are expected to move out of
northern lower Michigan by mid afternoon, leading to a lull in
precip chances and sunshine into this evening. Scattered to numerous
showers/storms will move into northwest lower and eastern upper this
evening, and move through the area tonight. A few strong storms will
be possible, with the main hazards being gusty winds and small hail.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 340 AM EDT Sun May 12 2024

Synopsis/pattern: Yesterday`s system of concern is near Niagara
and heading east. A surface ridge axis extends northward across
Lake MI and eastern upper MI, providing brief benign wx here.
Our next system is over far nw Ontario, with a cold front
trailing off into nw MN and eastern ND. This front moves into
the area late tonight.

Forecast: Dealing with some shallow ground fog in the usual
sheltered locales. That should erode fairly quickly past
sunrise. There have been some weak warm-advection-forced
showers/sprinkles early this morning in parts central/western
upper MI and northern WI. This is ahead of an elevated warm
front, and behind the surface ridge. These will continue to
migrate eastward, reaching western Chip/Mack Cos toward mid-
morning. Sct showers will continue to develop eastward across
the UP, far northern and ne lower MI, late morning to mid
afternoon. Trailing this, partial sunshine will break out,
especially in nw lower MI. That will help warm nw lower into
the lower 70s today, with 60s to upper 50s elsewhere (coolest
near Lakes Huron and Superior). Surface moisture does not
recover (yet), with dew points in the low-mid 40s most commonly.
So available Cape is minimal thru, say, 21Z/5pm.

But a surface warm front then pushes east into the area,
heading into this evening. Moisture in the BL jumps, with dew
points climbing to around 50f. That gives a narrow window
(before diurnal cooling kicks in) to boost MlCape values to
300-500j/kg. That corresponds with 0-6km bulk shear of 30-40kt,
and sw winds at 1km also of 35-40kt. So it`s another event with
reasonable shear and wind fields, but unimpressive instability.
Kind of wish either shear or instability were a little bit
stronger to get real excited. But SPC has a marginal svr risk
late today in a good portion of northern lower MI, and that
isn`t unreasonable. Main hazard is wind and perhaps hail,
between 6 pm and midnight.

So likely pops develop initially in eastern upper MI, the
Straits, and far nw lower MI, by early evening. That expands
se-ward thru the evening and early overnight, before pops start
to diminish and exit closer to morning. A chance for showers/
storms lingers in the far se thru 12Z. Localized QPF will exceed
0.50"

Min temps tonight from the lower 40s n to lower 50s se.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 340 AM EDT Sun May 12 2024

Pattern Forecast: Large scale pattern for this week starts with a
northern branch short wave trough/upper low over northern Manitoba
tracking east across James Bay...though it will slow/stall there as
heights build downstream over the Atlantic.  Meanwhile a southern
branch low over the Four Corners this morning crosses the central/
southern Plains Monday and into the southeastern U.S. by Wednesday.
Great Lakes remains in between these two features through midweek...
then another split trough coming in off the Pacific and into central
North America Thursday...and spreading height falls across the
region for the end of the week.

Northern branch wave passing by well to the north of the Great Lakes
has an associated surface cold front that will drop into Lower
Michigan Sunday night...and then stall across central Lower Michigan
as front parallels upper level flow.  Eventually this front should
be given a nudge south by high pressure over Hudson Bay/Baffin
Island ridging south into the upper Lakes Monday night/Tuesday with
north/northeast boundary layer flow setting up across Michigan.
Southern branch short wave trough over the mid/lower Mississippi
Valley Tuesday will have a surface reflection that tracks across the
Ohio Valley with eventual secondary cyclogenesis over the mid
Atlantic...while surface ridge continues to hang on over the upper
Lakes.  Pattern evolution gets more muddled toward the end of the
week but the idea in general for height falls and some resultant low
pressure moving through the Great Lakes perhaps in the later
Friday/Saturday time frame.

Primary Forecast Concerns:

Continuing rain/thunderstorm chances for central Lower Monday/
Monday night: Cold front will arrive in western Upper Michigan late
this afternoon and work its way into Lower Michigan after midnight.
Front looks like its going to get hung up south of M-72 Monday
morning...there may some showers along the low level theta-e axis
coincident with the boundary at the start of the day.  Some low
level instability will develop with diurnal heating which will
bubble up additional convection south of an MBL-APN line during the
afternoon. Meanwhile...southern branch short wave trough moving out
of the central/southern Plains expected to have a developing
deformation rain band that will spread into central/southern Lower
Monday afternoon/evening with a surge of deep layer moisture into
the southern half of the state (precipitable water 1.25-1.50 inch).
Northern edge of this precipitation shield will probably scrape
areas south of that same MBL-APN line...overnight mid level winds
shift more northwest across the northern half of the state which is
forecast to push the deformation zone farther into southern Lower.
As long as this pans out expectation is that rain threat should come
to an end by sunrise Tuesday.

Rain chances return Thursday and beyond: After a couple of dry days
with high pressure ridging in from the north...split Pacific trough
moves into the Plains/Midwest Thursday.  The majority of Thursday
may end up staying dry...better rain probabilities look to be occur
on Friday. And Saturday right now is a bit of a toss-up.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 157 PM EDT Sun May 12 2024

VFR conditions will persist across TAF sites into this evening.
Ongoing scattered showers are expected to move east of most TAF
sites later this afternoon, with the exception potentially being CIU
where showers will likely last into the early evening. A second
round of showers and storms is anticipated later this evening into
tonight, where a few strong storms capable of producing gusty winds
and hail will be possible. CIGs look to temporarily lower to MVFR,
and potentially IFR for a brief time, later tonight behind precip.
VSBYs may also drop to MVFR/IFR later tonight with patchy fog
possible. Otherwise, VFR conditions are expected to return shortly
after sunrise on Monday.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory until midnight EDT tonight for LHZ348-349.
     Small Craft Advisory until 10 PM EDT this evening for LMZ323-
     341-342-344>346.

&&

$$

UPDATE...DJC
SHORT TERM...JZ
LONG TERM...JPB
AVIATION...DJC