Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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875
FXUS63 KDTX 231130
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
630 AM EST Thu Nov 23 2017


.AVIATION...

Midlevel thetae advection ahead of approaching shortwave energy has
resulted in a solid opaque altostratus deck across all of
southeastern Michigan. Trajectory of cyclonic circulation through
far northern IN today should keep cloud in place for a good portion
of today. Uncertainty remains high with exactly how cloud trends
will play out later this afternoon. Model data suggests active
midlevel subsidence developing during the afternoon hours, but
forecast soundings are not overly convincing that it will be deep
enough to totally erode out the mid cloud. Active pattern will then
allow moisture from the next system to begin spilling down into the
Great Lakes late tonight.

//DTW THRESHOLD PROBABILITIES...

* None.

&&

.PREV DISCUSSION...
Issued at 332 AM EST Thu Nov 23 2017

DISCUSSION...

After bottoming out early in the mid to upper 20s, temperatures have
been steadily rising since midnight emerging southwest wind fills in
behind departing high pressure. Temps will be near 30 by sunrise.
Very little in terms of active weather for the next several days as
the storm track continues to retract further north.

A weak, moisture-starved wave with virtually no surface reflection
will support overcast mid-level clouds through midday, limiting
insolation for most of the heating period. As a result, temps will
struggle to reach 40 despite notably warmer mid-levels than
yesterday. Mid 30s possible along the glacial ridge and in the
Thumb. Strong low passing north of Lake Superior will maintain a
sufficient gradient to prevent decoupling and keep temps hovering
near 30 through tonight. 850mb temps will surge into the double
digits Friday as highs should easily reach 50 degrees in most
places. Displacement of forcing to the north and a lack of any
respectable system moisture will greatly limit prospects for precip
Friday evening. Nothing more than a low chc pop is warranted given
dry progged soundings and short-lived nature of forcing.

Temps will remain within a few degrees either side of normal through
the weekend. Global models still indicate the potential for
considerable height rises early next week. Continuity has been
shoddy at times as some solutions suggest energy may completely
cutoff over the southwest US, leading to flatter overall westerlies.
Latest solutions are trending away from this scenario, in which case
highs could be pushing 60 degrees by Tuesday.

MARINE...

Active stretch of weather over the lakes as a series of frontal
boundaries work across the region. Southwest flow will become
increasingly more organized today as return flow becomes better
established behind surface high pressure over the eastern U.S. While
the gustiest of the southwest winds will occur out over the open
waters of the Lake Huron basin, wave heights and wind gusts will
respond enough in the long southwest fetch to necessitate a small
craft advisory over outer Saginaw Bay.  A well organized low
pressure circulation will then emerge over the Canadian Prairie
provinces this evening before tracking eastward through Ontario
tonight. Increasing gradient and southwesterly flow ahead of the
front Friday into the overnight will likely reach gale force on
Friday. A gale warning has been issued Friday for much of the
central Lake Huron basin. A secondary cold front will then drop
through on Saturday ushering in a fairly cold airmass and increased
northwest flow.

PREV DISCUSSION...
Issued at 253 PM EST Wed Nov 22 2017

Discussion...

Quiet weather pattern expected for the rest of the week. While lower
stratus will erode into tonight, middle deck of clouds will thicken
as a weak shortwave races into central Great Lakes within northwest
upper flow regime. This should bring relatively steady temperatures
overnight as most area fall into the mid/upper 20s right away this
evening and then only oscillate slightly after midnight.

Southwest flow will increase in the wake the surface ridge over the
area as it settles southeast. This will begin a warming trend on
Thanksgiving as locations climb into the upper 30s to lower 40s with
a trend from mostly cloudy to partly cloudy skies throughout the day
as the aforementioned shortwave moves east of the area with time.

With generally clear skies on Thursday night, expect temperatures to
fall back into the upper 20s to around 30 during the evening as the
pressure gradient remains relatively weak through midnight. Expect
temperatures to once again remain relatively stable overnight as the
gradient tightens as deep low pressure shifts east into northwest
Ontario in response to the next strong shortwave digging out of the
Gulf of Alaska region.

This surface low, in the neighborhood of 980 mb, will approach the
Quebec border by Friday evening with southwest flow south and east
of the trailing cold front strengthening further during the day.
Gusts during the best mixing of the afternoon should reach 30 mph at
least with temperatures climbing into the upper 40s to lower 50s in
response to this warm air advection pattern. This cold front moves
southeast across the area Friday night, bringing at least a chance
of showers to the area. No snow shower activity is expected as the
temperatures will still generally be in the lower 40s during model
consensus for precipitation timing (and only fall into the upper 30s
at the coldest by early Saturday morning).

Behind the frontal passage, northwest cyclonic flow will advect
colder air across the region on Saturday with lake-effect clouds and
a few flurries/sprinkles possible throughout the day. High pressure
then builds into the region for Sunday bringing dry conditions while
highs top out near 40 as the thermal trough exits the region. As
high pressure sets up along the East Coast and low pressure develops
over the Central Plains, an increasing southwest gradient under
upper level ridging will allow warm advection to set up over the
region early next week. This will allow highs to make a run for the
low 50s both Monday and Tuesday as dry conditions continue.

MARINE...

Active stretch of weather over the lakes after high pressure slides
across the area tonight. Cold air funneling into the region with
tightening gradient ahead of a weak front will promote strengthening
southwest winds over the waters. Though gusts will stay below gale
force, a period of small crafts for a portion of Saginaw Bay will
needed. The next low pressure system will track through Ontario
Friday pulling a cold front through the Great Lakes Friday night.
Increasing gradient and southwesterly flow ahead of the front Friday
into the overnight will likely reach gale force thus a gale watch
has been issued for the majority of Lake Huron. A secondary cold
front will then drop through on Saturday ushering in a fairly cold
airmass and increased northwest flow.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Gale Watch from Friday afternoon through late Friday night for
     LHZ462-463.

     Gale Warning from 7 AM to 10 PM EST Friday for LHZ362-363.

     Small Craft Advisory until 4 PM EST this afternoon for LHZ421.

Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&

$$

AVIATION.....CB
DISCUSSION...JVC
MARINE.......CB


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