Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 280947
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
547 AM EDT Wed Jul 28 2021

.NEAR TERM...(Today through Tonight)
Issued at 329 AM EDT Wed Jul 28 2021

Impactful weather: Chance of severe storms and rainfall totals
exceeding flash flood guidance tonight, largely in and around the
GTV Bay area, and off to the south and west of there. Excessive
rainfall totals possibly exceeding flood guidance values for
flooding threat tonight.

Pattern synopsis and forecast:

Upper level troughing lingers over much of the eastern seaboard
states early this morning, while broad ridging continues to engulf
most of the western half of the conus. Nrn Michigan remains in
between, with upper level NW flow in place, and while there is
currently no more than very weak perturbations in the flow moving
overhead, there is a bit more defined vort max/wave dropping through
srn MN that helped spawn showers and thunderstorms last evening
across far SE MN. This was along/north of a quasi-stationary/warm
front that extends into srn Lake Michigan, within a strong theta-e
and instability gradient. This convection has since been tracking
S/SE, well away from our neck of the woods. Seen much further
upstream, was additional shortwave activity lifting up the western
periphery of the upper ridging across the Pac NW/nrn Rockies, while
other activity was crossing western Canada on the northern
periphery. This was resulting in more convection in these areas.
Here in nrn Michigan, we reside in a relatively drier, yet still
somewhat moist atmosphere. PWATs were around an inch, and sfc dew
points were in the lower half of the 60s most areas. The partly
cloudy/mostly clear skies combining with light winds/sfc dew points
and wet ground in spots, has resulted in the development of patchy
fog/reduced VSBYS. All-in-all...pretty quiet.

The core of the upper ridging will hold in the central Plains/lee of
the Rockies through tonight, but mid level height rises protrude up
through the western provinces of Canada. This will allow the
aforementioned western/northern periphery shortwave activity to
progress around the ridge, and dive into the western Great Lakes/nrn
Michigan tonight. This path will be along and north of that warm
front, with perhaps a sfc low pressure riding the boundary down
through central MN into srn Lake Michigan by daybreak Thursday.
While today will generally just see some passing mid and high cloud,
along with some FEW-SCT higher-based afternoon cumulus, with a cap
at 8kft preventing any daytime convection. However, showers and
storms are expected to fire across eastern portions of MN and NW
Wisconsin.

This convection is expected to follow the best LLJ theta-e
convergence along and north of the front, with DPVA and great right
entrance region divergence allowing for good deep layer -divQ to
impact nrn Michigan. The strongest forcing and deepest moisture
(PWATs possibly exceeding 2.00") are more likely to focus in the srn
half of Lake Michigan and the GTV Bay region. This is where the
greatest chance of showers and storms is expected to be, but all of
nrn Michigan will have chances for rainfall.

Speaking of rainfall, a WSW oriented LLJ could allow for continued
development of showers and storms behind the initial batch to come
through, and training of areas of showers and storms within that 2+"
PWAT air, may occur over the same areas. FFG has taken a hit in many
areas over the last few rainfall events, and total rainfall may be
able to exceed current FFG numbers across portions of the GTV Bay
areas, especially down by Manistee. Flooding may be an issue and
total rainfall will have to be monitored closely tonight.

Also, 0-6km effective bulk shear is expected to increase through the
evening, into the 35-45kt range, while several hundred j/kg of
MUCAPE will be available. It will not be out of the question for
the initial storms to become severe, with damaging winds and large
hail being the primary threats. This severe threat will primarily
impact Leelanau county through Traverse City and over into Gladwin
county, and all areas south and west of there. In general, the
severe threat will turn more to a flooding threat into the late
evening and overnight hours.

High temperatures will largely be in the lower to middle 80s. Lows
tonight will largely be in the mid and upper 60s due to increasing
clouds and BL winds, as well as being in a humid air mass.

&&

.SHORT TERM...(Thursday through Friday)
Issued at 329 AM EDT Wed Jul 28 2021

High Impact Weather Potential: Minimal attm...

Pattern Synopsis/Forecast:

Thursday morning...convection/precipitation should still be ongoing
as surface cold front and associated energy aloft move on out of the
Great Lakes. Subsidence will be in play behind the front Thursday
afternoon into Friday...with cooler air funneling into the region
for the end of the week. Another shortwave dropping through the flow
Friday night into Saturday will bring the next shot at
precipitation...and serve to reinforce the cooler idea for rest of
the forecast period (including the long term).

Primary Forecast Concerns: Rain/storm potential Thursday and again
Friday night...gusty winds Thursday afternoon and night...

First things first...will likely be looking at lingering
precipitation Thursday morning as surface cold front sweeps through
the area. There is still a touch of uncertainty in how quickly the
cold air aloft moves into the mid-levels...but overall idea has the
best moisture departing by Thursday afternoon. Wouldn`t be entirely
out of the question for some shower activity to linger across the
UP/NE Lower, though mid-level subsidence should be working into the
area behind the front Thursday, putting an end to those chances
through the day. May still see some diurnal cu development as we mix
out behind the front, though. Given tightening pressure gradient
behind the front...to some extent at the surface, but better aloft
in the mid-levels...will have some concerns for it to be a bit on
the gusty side Thursday afternoon and perhaps into Thursday
night...as we will have some instability aloft, potentially to mix
down some stronger winds, as the cooler air moves over the warmer
waters. Sort of a typical post-cold-frontal idea (gusty winds behind
the front).

Majority of Friday should be relatively nice...with Canadian high
pressure dropping in and bringing with it some quite dry
air....which we may need to monitor in future shifts for potential
for low afternoon RHs. Given antecedent dry air Friday with the
Canadian airmass...wonder just how quickly we`ll be able to moisten
up the atmosphere...and how quickly we`ll be able to get in on any
precipitation Friday night. Am therefore suspecting precip will be a
bit slow to move in Friday night. We`ll see. In the interim...Friday
will feel much more refreshing than the first half of the week has
felt.

.LONG TERM...(Friday night through Tuesday)
Issued at 329 AM EDT Wed Jul 28 2021

High Impact Weather Potential: Minimal attm...

If you like cooler weather, you`re gonna love the long term
forecast! Shortwave energy digging down the flow Saturday will
reinforce the westward extent of troughing this weekend...keeping
rain chances in play for the first half of the weekend. The overall
idea will be for cooler weather...though just how cool remains the
question, depending on how deep the troughing ends up across the
region. Additional wiggles in the flow as energy pinwheels through
the trough into early next week may be enough to keep showers in the
forecast...but will likely tend to keep things dry in the forecast
until higher confidence develops in the coming days. The bigger
story will be the cooler weather... the air conditioners should
finally catch a break!

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 546 AM EDT Wed Jul 28 2021

Fog will burn off fairly quickly this morning, and a quiet day is in
store with good sunshine and subdued wind speeds, resulting in
afternoon lake breezes. The main action comes in tonight, ahead of a
sfc low pressure and a warm front, which is expected to bring good
chances for showers and storms to much of northern Michigan. The
best chance for convection, as well as severe weather and heavy
rainfall totals, will be in and around the Grand Traverse Bay
region, obviously including TVC, and especially MBL. Conditions
after the early fog will be VFR, until MVFR/possible IFR CIGS are
expected to arrive late tonight for the NW lower airports, along
with possible reductions in VSBY due to convection.

&&

.MARINE...
Issued at 329 AM EDT Wed Jul 28 2021

A relatively quiet day with good sunshine and subdued wind speeds,
resulting in afternoon lake breezes. The main action comes in
tonight, ahead of a sfc low pressure and a warm front, which is
expected to bring good chances for showers and storms to much of
northern Michigan into Thursday morning. No real synoptic wind
speeds to be concerned with, but any thunderstorms will have the
ability for erratic and very gusty speeds. There is even a risk for
severe storms tonight, with damaging winds and large hail both being
concerns. A tighter pressure gradient does settle in through the day
Thursday, and overlake conditions will be neutral to slightly
unstable. This may very well result in advisory level NW winds that
continue into Thursday night.


&&

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

$$

NEAR TERM...SMD
SHORT TERM...FEF
LONG TERM...FEF
AVIATION...SMD
MARINE...SMD


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