National Weather Service - Area Forecast Discussion
000
FXUS63 KAPX 271053
AFDAPX
Area Forecast Discussion
National Weather Service Gaylord MI
653 AM EDT Sat Apr 27 2024
.KEY MESSAGES...
-- Showers/isolated thunderstorms this morning, ending before
noon.
-- Scattered severe thunderstorms are possible this evening
into tonight, bringing the chance for damaging winds, large
hail, and a tornado or two.
-- Scattered showers with isolated thunderstorms Sunday into
Monday.
-- Light rain showers Tuesday night into Wednesday.
&&
.SHORT TERM /THROUGH TONIGHT/...
Pattern Synopsis:
Well defined shortwave trough currently over the Upper Midwest will
continue to lift into the northern Great Lakes today, becoming more
open with time as amplified ridging folds over New England. The
associated surface cyclone will trek across the far northern Great
Lakes and Ontario today, eventually working into Quebec later
tonight. The attendant warm front will lift northward through the
area this morning into early afternoon, as a cold front draped
southwest from the system center looks to slide from northwest to
southeast across northern Michigan this evening and tonight.
Forecast Details:
Showers/isolated thunder this morning -- Showers ongoing across
parts of northern Michigan will continue through much of this
morning, along with the potential for isolated embedded
thunderstorms. This activity should end before noon, leading to a
lull in shower/storm chances through the afternoon into the early
evening hours. With this, morning cloud cover is expected to scatter
out this afternoon, helping temperatures to warm into the low to mid
70s.
Scattered severe storms possible this evening into tonight -- Bottom
line up front is that scattered severe thunderstorms will be
possible this evening into tonight, primarily across northern lower
Michigan between 6PM and 2AM. All severe hazards will be possible
with any strong storms that form later today, including damaging
winds, large hail, and the potential for a few tornadoes. With a
complicated forecast involving high uncertainty -- relatively low
confidence in strong storms, but any strong storms will carry the
potential to produce tornadoes -- will expand on the details of
these uncertainties below:
1.) Will strong storms form? (forcing, instability, and capping) --
This is perhaps the biggest question at this time. Current
confidence is that storms will develop in the 6PM - 9PM timeframe
along/ahead of the cold front. However, competing factors will be at
play. From the synoptic perspective, activity later today may
actually be fighting weak subsidence aloft - which will work
against strong storms attempting to develop.
To oddly add, a bit of a "Goldilocks" scenario may need to come
together to maximize severe potential later today. Ample buoyancy in
terms of severe parameters should be in place this evening (~1,500
J/kg MLCAPE) to support strong storms. However, too strong of
advection aloft to bring steeper lapse rates (increasing
instability) may also end up preventing strong storms from forming
due to a stronger capping inversion. If cloud cover clears and we
warm more aggressively than anticipated, this could decrease
favorable moisture within the boundary layer and potentially prevent
stronger storms from forming. Thus, a delicate balance of
sufficient moist boundary layer depth and instability aloft may
be necessary for severe storms. Current thoughts lean towards a
more favorable environment in place later today at this time.
2.) How strong may storms be? -- While there is relatively high
uncertainty in strong storms forming later today, any strong storm
will be capable of producing damaging winds, large hail, and
tornadoes. Strong deep-layer shear (~45-50 kts) will overlap with
aforementioned instability to support potential for organized strong
storms. Southwest winds veering and strengthening quickly off the
surface will create plenty of low-level streamwise vorticity with
looping hodographs and ~250-300 effective SRH to support a tornado
threat with any multicell clusters/embedded supercells. While there
will be a strong component of boundary-parallel flow that typically
tends to keep convection in the zone of forcing and promote a linear
storm mode, relatively slow initial frontal movement may be enough
to help keep any strong storms semi-discrete in nature for a short
window during the evening -- increasing severe potential for a
period of time. To note, convection-allowing models tend to struggle
across the Great Lakes in scenarios like this. While most output may
seem unimpressive at first look, a supportive environment for all
severe hazards will be in place later today and will still be
monitored closely -- despite what some current/future model forecast
reflectivity suggests. Be sure to stay tuned to the latest forecast
for updates, especially later today as the severe risk will linger
into the overnight hours.
&&
.LONG TERM /SUNDAY THROUGH SATURDAY/...
Pattern Synopsis and Forecast:
Southwest flow aloft will remain on Sunday. Spokes of energy swing
through during the day and into the overnight hours resulting in
scattered rain showers and perhaps some embedded thunder, especially
overnight. Warm front lifts through northern Michigan on into Monday
as low pressure system moves into the Upper Midwest resulting in
continued shower and some possible storm development. Frontal
boundary with drier airmass will follow Monday night as low pressure
system moves northeastward. Another low pressure system will move
well to the north of the area with another shot at showers or storms
in the Tuesday night to Wednesday time frame as the associated sfc
boundary passes through. Looks messy and potentially unsettled
thereafter late next week.
Primary Forecast Concerns:
Energy aloft will rotate through northern Michigan within southwest
flow Sunday and Sunday night. Thus, a couple rounds of scattered
showers with a few embedded thunderstorms will be possible (albeit
most of the instability looks to remain south of our area). Although
showers are likely Monday morning, mid to upper 50s dewpoints and
70s sfc temps during the afternoon will likely foster at least a
little instability. That being said, mid level lapse rates are quite
poor as there will be warmer air in the mid levels of the
atmosphere. Thus, thunderstorms will be possible during the
afternoon hrs Monday. Any organized threat does appear limited
though for the aforementioned reasons (I suppose still worth
keeping an eye on). Sfc boundary will move through Monday night
putting an end to precipitation by Tuesday morning as drier air
works into the region.
Next period in time to monitor will be Tuesday night into Wednesday.
Upper level low will move from the Northern Plains into Canada
Tuesday evening into Wednesday with an associated sfc low following
suit. Sfc boundary associated with this feature will move from the
MN-WI into Michigan Tuesday night into Wednesday potentially
focusing some shower development. There did appear to be some minor
instability on Wednesday via the previous guidance, but the latest
suggests very little. Thus, for right now calling it a chance for
showers (some of the guidance is diminishing shower threat as it
approaches the area, will have to see if that holds true) but really
does not appear too terribly impactful unless the thermodynamic
environment/precipitation coverage improves. Temperatures remain
mild through mid week. Looks to be a lot of energy and moisture
hanging around the center of the country in the extended, thus could
more rain chances to end the week.
&&
.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Showers will continue to work across northern Michigan this morning
and are expected to end by this afternoon. While most areas are
still VFR, MVFR CIGs are expected to move in over the next few
hours. Clouds are expected to scatter out early this afternoon,
likely leaving VFR conditions in place into tonight. The exception
will be CIU where IFR/MVFR CIGs look to stay in place longer in
closer proximity to better moisture. Chances for showers and storms
return early this evening into tonight. South winds will gradually
veer to southwest winds with speeds of 10-15 kts with gusts to 20-30
kts into this evening before a cold front moves through later
tonight. LLWS will also be possible for the next few hours
across northern Michigan TAF sites.
&&
.APX WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory until 2 AM EDT Sunday for LHZ345>349.
Small Craft Advisory until 2 AM EDT Sunday for LMZ323-341-342-
344>346.
Small Craft Advisory until 2 AM EDT Sunday for LSZ321-322.
&&
$$
SHORT TERM...DJC
LONG TERM...JLD
AVIATION...DJC
NWS APX Office Area Forecast Discussion
