National Weather Service - Area Forecast Discussion

FXUS63 KAPX 191105

Area Forecast Discussion
National Weather Service Gaylord MI
705 AM EDT Thu May 19 2022

.NEAR TERM...(Today through Tonight)
Issued at 347 AM EDT Thu May 19 2022

...Much needed rain looking likely tonight...

High Impact Weather Potential: Watching the threat for thunderstorms
tonight. Severe weather is not expected at this time.

Pattern Synopsis/Forecast:

Zonal and relatively fast-paced flow continues across much of the
northern Conus at this early hour. Embedded shortwave trough racing
east into the northern Great Lakes, helping kick off a few scattered
light showers as it passes. Main wave of interest for this forecast
cycle analyzed well to our west, the center of which is moving
across southern Alberta and Saskatchewan. This wave will help kick
large scale amplification into high gear tonight and Friday, helping
develop broad troughing into the northern Plains/southern
Canada...with subsequent downstream ridge amplification across the
Great Lakes. Deepening southwest and increasingly moisture rich flow
between these systems will drive shower and storm development
tonight into Friday, some of which could become locally severe and
produce heavy rain (greatest severe threat remains on Friday...see
that information in the short term section to follow).

Primary Forecast Concerns/Challenges:

Main focus on increasing shower and thunderstorm threat tonight.


Expect any light showers associated with current wave to pivot off
to our east quickly this morning. Looks as if much of the day will
remain dry thereafter, with perhaps a few light showers returning
across western areas late today as initial stages of moisture
advection begins. Skies should become partly to mostly sunny across
much of the area later this morning and early afternoon, and when
combined with strengthening warm air advection, should help
temperatures reach into the 70s across a good portion of northern
lower Michigan, with cooler reading near the big waters and across
eastern upper Michigan. Expect showers and thunderstorms to ramp up
significantly this evening to our west along intense instability
gradient and on nose of 50+ knot low level jet. Simply following
greatest mass convergence axis on nose of this low level jet
supports these storms racing northeast into our area overnight.
Greatest support for more organized storms appears to center across
eastern upper Michigan where jet support will be maximized. Storms
will become increasingly elevated as they enter our area, with best
cape and severe weather parameters becoming increasingly detached to
our west. So, currently not expecting any of these storms to become
severe. Precipitable water values nearing an inch and a half support
some locally heavy rains with any more organized storms. Again,
greatest threat for this heavy rain is north of the big bridge.
Definitely a mild night, with lows mostly ranging through the 50s.


.SHORT TERM...(Friday through Saturday)
Issued at 347 AM EDT Thu May 19 2022

...Severe thunderstorms possible Friday...

High Impact Weather Potential: Thunderstorms capable of producing
all severe hazards will be possible Friday.

Pattern Synopsis:

Troughing and the associated jet will pivot across the upper Midwest
and lift into Canada Friday, supporting a cyclone that will trek
from the upper Great Lakes over James Bay during that time. The
attendant cold front will slide across the area during the afternoon
and evening, likely stalling further downstate overnight. Subtle
perturbations embedded in prolonged NW upper-level flow over the
baroclinic zone will lead to eventual surface pressure falls and
induce a weak cyclone over the eastern Great Lakes late Saturday.

Forecast Details:

The main focus of the period will be on the potential for severe
weather on Friday, mainly across the northern lower peninsula. Will
echo SPC`s thoughts in their Day 1 06Z Outlook by saying that plenty
uncertainty currently exists in how Friday will play out. The
biggest forecast challenges are:

1.) Ongoing convection Friday morning. As mentioned in last night`s
short term and the near term above, at least some convective
activity is expected across the area leading into Friday morning.
Depending on its extent and intensity, this will play a vital role
in severe chances later in the afternoon. Thunder is expected
through the morning and, based on elevated instability and
relatively strong shear aloft, strong/marginally severe storms
cannot be ruled out through the morning hours. Will once again
emphasize uncertainty, but higher confidence currently exists in
this activity clearing out by late morning for a relative lull in
rain/thunder chances.

2.) Degree of instability/support in place by early afternoon. With
a potential lull in convective activity, this could allow for the
partial clearing of cloud cover ahead of the advancing cold front.
In turn, this would aid destabilization of the warm sector and
enhance severe chances Friday afternoon -- and may even be the key
to severe weather materializing. While model guidance displays ample
values of total MLCAPE through the profile, interrogating forecast
soundings will bring to light concerns in the true degree of
instability across northern Michigan Friday afternoon. Very moist
thermo profiles/pseudoadiabatic lapse rates will make for "skinny"
CAPE, which will limit potential upward forcing air parcels can
achieve. This will be compounded by the fact that northern Michigan
will be experiencing height rises through the day, providing
evidence of little to no upper-level support -- and convection may
even be fighting a slightly unfavorable large-scale dynamic
environment aloft.

3.) Convective evolution. While confidence is high in thunderstorms,
the limitations discussed above cast uncertainty on the evolution of
potentially severe thunderstorms. Forecast PWAT values are near
climatological max values, which will also contribute to the
potential for a more wet, messy convective evolution Friday
afternoon that would potentially limit higher severe potential.
Boundary-parallel cloud-layer flow along the cold front will also
lead to quick upscale growth across NW lower Michigan with storms
Friday afternoon. Perhaps the most significant severe potential
would come with any potential storms that initiate away from the
front, whether it is due to differential heating boundaries with
partial afternoon clearing and/or along modified remnant outflow
boundaries from AM convection.

All this said, damaging wind gusts would be the primary hazard with
storms that form along the cold front. Forecast soundings displaying
strong low-level shear (0-3 km shear in excess of 40kts) show the
potential for a tornado or two with any bowing segments that favor
line-perpendicular shear. As mentioned above, any multicell clusters
that initiate/sustain themselves in the open warm sector would be
capable of producing all severe hazards. However, plenty of
uncertainty still exists and the lack of more substantial
instability and upper-level support may end up hindering potential
severe storms Friday. Otherwise, localized flooding will be possible
across areas that experience multiple rounds of storms today through
Friday as high PWATs will lead to efficient rainfall. Additional
rain chances are expected on Saturday as the front stalls south of
the CWA and forcing aloft slides overhead.

.LONG TERM...(Saturday night through Wednesday)
Issued at 347 AM EDT Thu May 19 2022

High Impact Weather Potential: Frost/freeze concerns Sunday night.

As the stalled front discussed in the short term sits south of the
CWA amidst a weak surface pressure response along the boundary,
forcing aloft will generate the chance for continued showers across
parts of northern lower Michigan Saturday night and Sunday morning.
Subsidence on the backside of the departing wave will build dominant
high pressure that will spread from the northern Great Plains into
the Great Lakes by Sunday night. Clear skies and calm winds will
allow for efficient radiational cooling overnight, likely dropping
overnight lows near or below freezing and creating frost/freeze
concerns late Sunday night across interior northern Michigan. High
pressure appears to settle in through the beginning of the week
before the next main chance for rain arrives in the Wednesday/
Thursday timeframe. Otherwise, temperatures are expected to remain
slightly cooler than average through the weekend and much of next
week as highs stay in the low to mid 60s most days across the


.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 701 AM EDT Thu May 19 2022

Low cigs expected to scatter out this morning, leaving behind just
some mid and higher level clouds. Moisture increases from the west
again tonight, perhaps bringing some showers (thunderstorms?) to
western taf locations...and MVFR cigs to KPLN. Wind shear expected
to develop tonight as low level jet spreads overhead.


Issued at 347 AM EDT Thu May 19 2022

Mostly light winds today ramp up tonight and Friday out of the south
and southwest. Over-water conditions will be stable, but will still
likely see small craft advisory conditions late tonight into Friday,
especially across northern Lake Michigan. In addition, shower and
thunderstorm are expected tonight and Friday, any of which could
bring locally gusty winds and heavy rain. Winds become light again
Friday night on into the start of the weekend.


LM...SMALL CRAFT ADVISORY from midnight tonight to 5 PM EDT Friday
     for LMZ344>346.



NWS APX Office Area Forecast Discussion