921
FXUS63 KAPX 191317
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
917 AM EDT Sun May 19 2024

.KEY MESSAGES...

- Lingering Rain/storms this morning

- Dry and warm with fire weather concerns this afternoon

- A round of showers and thunderstorms is expected late Monday
afternoon into Monday night. Marginal Risk (1/5) for severe
thunderstorms.

- Cold frontal passage Tuesday night brings another chance for a
  round of showers and thunder.

- Cooler and occasionally unsettled Thursday and beyond.

&&

.UPDATE...
Issued at 917 AM EDT Sun May 19 2024

No major changes needed. Cold front is evident as a skinny band
of cu over ne lower MI, and will progress into se lower MI
today. A bubble high trailing the front builds into upper MI
this afternoon. Any slight chance for precip will end as the
front departs, with re-ignition along the front more likely
well to our south later today. Weak cool/dry advection will
continue; the main drying component will be increased vertical
mixing into much drier air aloft. Elevated fire danger remains a
reasonable approach for this afternoon/evening, as RHs should
crater into the 20-25% range. Limited cloud cover, except for an
initial increase in cirrus blowoff into western/northern areas
late.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 404 AM EDT Sun May 19 2024

PATTERN SYNOPSIS/FORECAST:

Zonal longwave trough across the northern US/southern Canada...with
a lobe dropping into the western end of this over the PacNW. An
upper low continues to spin across the SE US...with some troughing
over SoCal. Primary focus for MI attm is a vort max on the eastern
end of the northern stream trough...spiraling over western Ontario
early this morning. Strengthening height falls and CAA into the
Upper Midwest with this...and looking at a triple point over W.
Central Ontario with an occluded low back over the Manitoba/Ontario
border. Surface cold front stretches down through W. WI, wrapping
back into KS as of 5z. Some convective activity well ahead of this
over WI/upper MI...running into a less favorable environment overall
the further east it gets...and not surprised to see this start
dying...though cell moving into MBL attm produced a gust to 31kts at
the airport as gust front begins to outrun the initial cell.
Interestingly the temp went up at TVC with the gust front,
potentially thanks in part to some downsloping...so not impossible
that TC sees it high very early this morning, with northerly winds
today likely to keep things from getting too out of hand temp-wise.

Cold front to continue to progress through the area this
morning...ultimately swinging out of the Saginaw Bay region this
afternoon, with the expectation that any lingering showers/storms
should be exiting stage right between 14-16z. High
pressure/subsidence and a very dry air mass in its wake for most of
the day, especially across NW Lower (upstream dewpoints generally in
the upper 30s to low 40s behind the front across N. WI/western UP as
of 6z)...with potential for very low afternoon RHs amid warmth and
winds gusting 10-15mph that could be a slight concern on the fire
weather front. Southern portion of the front looks to stall out more
or less zonally across southern lower MI going into tonight...as
return flow strengthens to our west going into Sunday night.

Primary Forecast Concerns:

Lingering Storms this Morning...A few hundred joules of elevated
CAPE expected this morning across NE Lower ahead of the front,
which, with the added lift from the front, has some potential to be
achieved...largely south of a line from Alpena to perhaps HTL or
Gladwin-ish. Would not be surprised to see some slightly beefier
storms over in this region...though think anything would be more
pulsey in nature than terribly well organized, given deep layer
shear isn`t very strong...and the front should be waning in
intensity with time, too. Blob of convection passing between TVC and
CAD as of 7z does give me a bit of hesitancy that it could
negatively impact the environment...though dewpoints in its wake for
now seem to be creeping upward, which could give a slight boost to
convective instability initially as dry air moves in aloft
immediately behind the front...before we start to mix out too much.
Not expecting this threat to last very long, though...as the front
may be out of here fairly quickly in the morning...and we should
quickly begin to mix down that drier air aloft.

Afternoon RHs/Fire Weather Concerns... Temps expected to reach into
the 70s and low 80s over the Saginaw Bay region, where best
downsloping is expected. I do have to wonder, though, noting that
the temp at TVC went up to 73 in the last few hours (at least in
part due to downsloping with the gust front from that cell that
moved through MBL)...if they will get warmer than currently expected
over there...or if they will end up being held in the mid 70s by
generally northerly flow off the Bay. Either way...very dry air mass
advecting in from the west should support dewpoints dropping into at
least the upper 30s or lower across a great portion of the
area...though I have a suspicion we`ll be looking at dewpoints in
the low 30s across parts of the area, especially where
north/northwest flow aids in downsloping. (Would not be surprised if
we end up lower than this...though given that a lot of the area has
been greening up...think it`s still possible we may not get as low
as we otherwise could.) This should bring critical RHs to a majority
of the area...which will be of concern for fire weather purposes,
with wind gusts floating around 10-15mph at max today.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 404 AM EDT Sun May 19 2024

Pattern Synopsis / Forecast:

Associated uptick in southerly flow ahead of an ejecting trough and
associated developing surface low across the central Plains will be
enough to force a stationary front northward from downstate into the
APX footprint through the day Monday, resulting in a rich moisture
feed to the region. As this happens, progressive 500mb flow will
drive a subtle shortwave along the front from the western Corn Belt
into the Great Lakes, bringing about potential for rounds of showers
and thunderstorms later Monday afternoon into Monday night as the
front stalls out overhead Monday night, which likely continues
shower and storm chances into Tuesday. Upstream, the aforementioned
developing cyclone deepens considerably (potentially sub 990mb) as
it surges into the vicinity of western Lake Superior. This should
provide ample warm air advection to force the stalled frontal
boundary north of Lake Superior, putting the region firmly within
the warm sector of the cyclone by late Tuesday afternoon. Associated
cold frontal boundary looks to surge through the area Tuesday night,
and pending on if we can destabilize / remain unstable enough, this
may set the stage for another round of showers and thunder across
the region. Low pressure will become closed off somewhere in the
vicinity of the upper Great Lakes after Tuesday night, which should
deliver cooler air to the region, but the continued presence of
shortwaves pivoting around this system will lead to some continuity
of unsettled weather through the remainder of the week before things
dry out some Thursday and Friday.

Temps: 70s and 80s Monday (could change based off morning cloud
cover / rain trends), mainly 70s Tuesday (near 80 closer to Saginaw
Bay). 60s and 70s Wednesday fall to somewhat more seasonable upper
50s to mid 60s Thursday and Friday.

Primary Forecast Concerns:

Sneaky Active Monday / Monday Night?: Better forcing is expected to
arrive as a quick-moving wave rides along the northward lifting
frontal boundary into Michigan. Latest CAMs are all over the place
with where this jolt of energy will result in surface based showers
and storms to blossom in the vicinity of the front (where surface
dewpoints bump into the low-to-mid 60s and rapid destabilization up
to ~1250 to 2000 J/kg MLCAPE may materialize). Where this surface
based instability is realized, there is potential to see a stronger
storm. Not a lot of shear present in the grand scheme of things ,
most likely gusty outflow driven / multicell storms that potentially
evolve into a bowing segment... some hail is possible too). Some
models initiate as far north as the Bridge... and this appears to be
taken into consideration by SPC as they have introduced a Marginal
Risk (1/5) of severe storms Monday for locales south of the Bridge.
Another factor looks to be efficient rainfall. PWATS of 1.25-1.50
are expected by Monday evening, which based off APX sounding climo,
is well above the 90th percentile for the mid-late May. The
atmosphere is going to be juiced, and with the wave approaching
closer to 21-00z, that opens the door for instability to be
maximized. As such, model soundings show a textbook "skinny CAPE"
profile found with heavy rainfall events. It`s not impossible for
localized 2.00"+ rainfalls in a short timeframe, especially in any
areas that see multiple storms. At this time, the favored area for
this in the CWA is M-72 and south into central Michigan.

Tuesday: Stalled warm front will be forced farther northward by
deepening low pressure across the western Corn Belt, which then
proceeds to move into the vicinity of western Lake Superior. On
paper, this is a favorable spot for low pressure to produce severe
weather in the APX footprint, but there will be some significant
hindrances. First, the nocturnal passage of the front brings
question to how much can initiate along the front, especially if
deep convection over IA/IL/WI follows an instability gradient and
passes to our south, choking off deeper moisture flow. Good dynamics
in place suggest a severe threat if we can get anything to initiate.
Potential for CAPE values in excess of 1,000 J/kg, bulk shear of 45-
55kts, coupled with diffluent flow aloft suggest that deeper
convection and tilted updrafts are a distinct possibility Tuesday
night. Given the later timing and excellent forcing, thoughts are
still that this setup would favor a linear convective mode (QLCS?)
with all severe hazards on the table. As such, SPC has placed areas
west of US 131 in a Slight Risk (2/5) and the rest of the area in a
Marginal Risk (1/5) for severe storms. Will have to continue to
watch the evolution of this setup over the next two days.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 645 AM EDT Sun May 19 2024

Cold front crossing the area this morning. Lingering fog/low stratus
over CIU and APN to lift quickly. Few high-based (7kft) cu trying to
be CB attm...best chance for any development into TS through 16z
would be from APN to HTL and east toward OSC/Y31...but chance is
very small; have put VCSH for APN this morning to account for this.
Otherwise...expecting clear skies and NNW winds 5-15kts; low
probabilities of gusts up to 20kts. Lake breezes to develop this
afternoon, with greatest impact at APN where winds should try
to switch to more easterly. Flow begins to turn to the SE this
evening with increasing high clouds (cloud bases 10kft and up).
For now...expecting TS/RA chances to hold off till after this
TAF period.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.

&&

$$

UPDATE...JZ
SHORT TERM...FEF
LONG TERM...HAD
AVIATION...FEF