969
FXUS63 KAPX 181538
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
1138 AM EDT Tue Jun 18 2024

.KEY MESSAGES...

- Very hot, humid conditions continue with scattered
  showers/storms today.

- Warm to hot temperatures will linger through the work week

- Rain and storm chances linger through most of the forecast

&&

.UPDATE...
Issued at 1138 AM EDT Tue Jun 18 2024

Synopsis: 13z surface/composite analysis shows a 995mb low over
eastern South Dakota...warm front extends east-northeast across
Minnesota/far western Upper and into northeast Ontario. Second
frontal boundary extends north across eastern North Dakota and into
far northwest Ontario.  Plenty of low level moisture south of warm
front with dew points across state (with the exception of the
Keweenaw Peninsula) well into the 60s with some lower 70s across
Lower Michigan...and surface temperatures across northern Lower
already well into the 80s as of 15z.  Upper level high centered over
the mid Atlantic with deep layer south/southwest flow into the Great
Lakes.  A mid/high level overcast was spreading northeast from
southern Lake Michigan/southern Lower Michigan toward northern
Lower...along with some high based radar returns.  This is
associated with a compact but well-defined vorticity center entering
southwest Lower per water vapor imagery.  This deep layer southerly
flow is also pulling an impressive plume of moisture north...
emanating from the area around Potential Tropical Cyclone One
in the southwest Gulf. Precipitable water values over 1.75
inches over southern Lake Michigan and 2.00+ inches across parts
of Illinois/ Indiana/western Kentucky.

Forecast Update:  In addition to the approaching mid/high cloud
deck..some Cu are starting to bubble up over northern Lower.  12z
APX sounding already had over 900J/kg MLCAPE with -95J/kg MLCINH...
straight up modification of that sounding for the current 86/66
at KGLR yields 1764 J/kg with an elimination of MLCINH. So the
arrival of the short wave trough from the south should increase
the chances for showers/thunderstorms to develop. Not much in
the way of deep layer shear so organized severe threat will be
low but could see some pulse type severe especially with a wet
microburst wind threat. Looking at high temperature records
today think most of them are safe...will come close at GLR
(92/1994) and PLN (93/2007). Records of 96 and 97 at KTVC/KAPN
respectively may bit a bit of a reach especially with increasing
cloud cover.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 403 AM EDT Tue Jun 18 2024

Pattern Synopsis:

Impressive, strong ridging will continue to dominate the eastern
CONUS today and tonight with surface high pressure centered far off
the Atlantic coast. Northern Michigan will remain locked between
said high pressure and an elongated cyclone stretching across the
Upper Midwest/Ontario into Wednesday morning as the ridge/trough
inflection point gradually across the northern Great Plains through
the period.

Forecast Details:

Very hot, humid conditions with showers/storms today -- South-
southwesterly low-level flow will continue warm, moist advection
across the Great Lakes, keeping very hot, humid conditions in place
for many areas today. Widespread highs in the mid 80s to low 90s are
anticipated this afternoon with heat indices reaching into the mid
to upper 90s. The hottest conditions today are anticipated across
northeast lower, the Straits, Grand Traverse Bay region, and the far
eastern U.P. Temperatures should quickly rise into the mid/upper 80s
across most of northern Michigan by late morning, but the
development of scattered showers/storms by early afternoon should
work to limit how hot temperatures get -- especially across interior
areas. Best chances for showers/storms will be along and east of I-
75 this afternoon and should move southwest to northeast, allowing
portions of far northeast lower to warm into the 90s before
substantial cloud cover and rain-cooled air lower temperatures.
Thus, high temperatures may be seen during the early afternoon hours
for many across the area with temperatures cooling from
aforementioned convection during mid/late afternoon. While small
hail, gusty winds, and locally heavy downpours will be possible with
any strong storms, severe weather is not anticipated this afternoon.
Tonight will fail to offer meaningful relief from daytime heat as
lows only cool into the low to mid 70s across the area.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 403 AM EDT Tue Jun 18 2024

Pattern Synopsis and Forecast: The upper level high will be centered
over northern Mid Atlantic region by Wednesday. At the same time an
upper level trough will be over central Canada, continuing southwest
flow aloft over the Great Lakes region. A well established Gulf
moisture tap will continue to maintain higher moisture amounts in
this region, keeping PW values around 1.5" through Sunday. Hot
temperatures and intermittent rain and storm chances will be seen
over the whole CWA through early next week as the upper level high
slowly widens to our south by the end of the work week. Ample
moisture will continue to rotate around the high, even as winds
become more west. The upper level high will weaken as it widens,
allowing an upper trough to reach MI from Canada this weekend. This
should finally cool temperatures back down to near or even a few
degrees below normal. Rain chances will continue as a progressive
patter is hinted to establish early next week.


Primary Forecast Concerns/Key Messages: Hot temperatures will likely
continue through Thursday as upper level heights continue to trend
upward. Moisture will linger, giving way to the uncertainty in the
duration of very hot temperatures. However afternoon temperatures
will likely continue to feel uncomfortable through the end of the
work week. Upper level heights finally start to trend down Friday,
and so will temperatures start to gradually decrease. Higher chances
of an upper level trough swinging through this weekend, brining more
rain chances but will allow temperatures to drop to near seasonal
again. Rain and storm chances will exist almost each afternoon as
moisture continues to be provided to the region. The lack of a
defined trigger will make the exact location and time hard to nail
down, however most storms will likely have heavy rain, lightning,
and possibly small hail and/or brief gusty winds (however that is
less likely at this time). If convection can kick off over a defined
boundary, training could be an issue of some storms. This could lead
to locally higher amounts of QPF. The wet pattern will likely hang
around for the foreseeable future.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 630 AM EDT Tue Jun 18 2024

Mainly VFR conditions are expected across northern Michigan through
the TAF period. Scattered showers and thunderstorms will be possible
later today, although explicit mention of thunder has not been
included in the 12Z TAFs at this time due to uncertainty in coverage
and timing. Otherwise, south-southwest winds around 10-15 kts are
expected to gust between 20-30 kts at times into this evening. LLWS
will also be possible at northern Michigan TAF sites later this
evening.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory until midnight EDT tonight for LHZ348-349.
     Small Craft Advisory until 5 PM EDT Wednesday for LMZ323-341-
     342-344>346.
     Small Craft Advisory until 8 PM EDT this evening for LSZ321.

&&

$$

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