Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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807
FXUS63 KDTX 162033
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
333 PM EST Fri Feb 16 2018

.DISCUSSION...

NEAR TERM / REST OF TODAY THROUGH TONIGHT

As of 330 PM EST...Regional satellite trends continue to depict
stratus layer gradually eroding into a broken stratocu layer from
northwest to southeast across the region, as drier air accompanying
high pressure ridges into the region. Enough boundary layer moisture
coupled with diurnal heating has allowed a few flurries to squeak
out across portions of the Saginaw Valley and Thumb, although of
little consequence.

The area of high pressure will track just south of the region across
the Ohio River Valley into tonight, with cloud cover clearing out by
this evening and continuing through early tonight. This clearing
will be relatively short-lived, as emerging northern and southern
stream energy from the Plains brings increasing high clouds towards
daybreak Saturday. The clear skies coupled with initial low-level
cold air advection (transitioning to warm air advection late in the
night) will allow low temperatures to fall into the teens tonight.
Where deeper snowpack still exists, particularly north of M-59, a
few areas could dip as cold as the upper single digits.

SHORT TERM / SATURDAY THROUGH SUNDAY NIGHT

The high pressure will continue sliding east towards the Mid-
Atlantic as the northern and southern stream energy continue to
approach from the west. Dry weather will continue through much of
the day Saturday with high temperatures a few degrees warmer than
Friday in the mid and upper 30s. The 12z model suite continues to
largely fall in line with previous model guidance regarding snow
potential Saturday evening through Saturday night. A lack of phasing
coupled with moisture transport being shunted to the southeast will
only lead to a chance of snow showers, with the best shot at seeing
some minor accumulations (less than an inch) north of the M-59
corridor.

Another quick passing area of high pressure to the south will yield
tranquil weather on Sunday. High temperatures will reach into the
lower 40s across much of the region as the moderating trend
continues as low-level warm air advection increases. This tranquil
period will be short-lived as a significant pattern shift in the
longwave pattern begins to take shape as vigorous Pacific energy
moves into the western CONUS.

LONG TERM / MONDAY THROUGH THURSDAY

The aforementioned Pacific energy will allow a deep longwave trough
to develop across the western CONUS, with upper-level ridging
developing off the eastern seaboard. A low amplitude northern
hemispheric wave pattern will lead to a period of blocking flow
Monday and continuing through much of the long term, with southeast
Michigan placed right in the crosshairs of the resultant baroclinic
zone between the differing airmasses.

The long range forecast continues to feature significant uncertainty
and spread amongst the long range guidance, both from a
deterministic perspective and within their own ensemble members such
as the ECMWF. These ramifications will have a big impact on
precipitation potential and intensity Monday-Wednesday. At this
time, confidence is moderate that the baroclinic zone will set up
somewhere in the vicinity of southeast Michigan, with several waves
of low pressure riding up along it. Some consensus in the guidance
though for the upper-level jet axis being anchored northwest of the
region does lend increasing confidence that southeast Michigan will
be on the warm side of the baroclinic zone. Strong warm air
advection and moisture transport will occur in the warm sector
allowing temperatures to soar Monday and Tuesday. High temperatures
Monday look to reach well into the 50s and on Tuesday, possible
record highs with areas south of Flint possibly cracking into the
lower 60s. For more on potential record high temperatures, see the
Climate section below.

Accompanying the warmth though will be the potential for heavy
rainfall. Due to so much uncertainty in the eventual placement of
the baroclinic zone, it is still too early to hone in on exact
amounts, but there is the potential for well in excess of an inch of
rain beginning Monday and persisting through Wednesday. Thunder will
even be possible at times as well, especially Tuesday, as elevated
instability creeps northward into the region. The forecast continues
to remain uncertain beyond Wednesday as another surge of
precipitation potentially impacts portions of the region.

&&

.MARINE...

Winds will undergo a steady backing toward the southwest during the
course of the night as high pressure traverses the Ohio Valley. The
southwest gradient will then increase during the day Saturday as the
high drifts off the east coast and a cold front approaches the
region from the northwest. The extensive ice cover will keep peak
wind gusts primarily below 30 knots on Saturday. Winds will veer to
the west northwest with the passage of this sfc trough Saturday
night, with speeds decreasing into Sunday as the gradient relaxes.

&&

.HYDROLOGY...

There is high probability of a substantial warming trend Monday into
Tuesday, resulting in a complete melt off of all snow cover across
Southeast Michigan. This warming will occur as a result of strong
southerly flow ahead of a slow moving front. In addition, periods of
rain are expected along this front, beginning Monday and possibly
persisting into Wednesday. Forecast confidence on how quickly this
system moves east of the region and where the axis of heaviest rain
will fall still carries a good deal of uncertainty. There is however
a chance that total rainfall amounts will exceed one inch. While the
complete melt of snow will not be enough to support flooding. The
potential rainfall with the snow melt will lead to a chance for
significant rises on area rivers and streams.

&&

.CLIMATE...

Record high temperatures will be possible across much of southeast
Michigan Tuesday. Here is a look at record high temperatures for
Tuesday, February 20th:

Detroit                63 (set in 2016)
Flint                  61 (set in 1930)
Saginaw/Tri-Cities     62 (set in 1930)

&&

.PREV DISCUSSION...
Issued at 1143 AM EST Fri Feb 16 2018

AVIATION...

Lift associated with a short wave trough that will track across Se
Mi early this afternoon combined with diurnal mixing will continue
to result in some lifting of the strato cu base, possibly to MVFR.
Can not rule out a few flurries with this wave, particularly around
MBS and FNT. A push of mid level subsidence and dry air advection
behind this wave will then offer the potential for a clearing trend
late this afternoon into the evening. The circulation around sfc
high drifting toward the mid Atlantic early Sat morning may however
allow some remnant low clouds to funnel back across Se Mi under a
deepening low level inversion. Despite indications of this in the
latest hi res models, confidence is not yet high enough to carry an
overcast low cloud deck in the TAFs late tonight through Sat
morning.

For DTW...There will be a gradual weakening of the northwest winds
this afternoon while they slowly back toward the west. This will be
a result of the high pressure system expanding into the Ohio Valley
and the corresponding weakening of the sfc gradient.

/DTW THRESHOLD PROBABILITIES...

* High for cigs below 5000 ft this afternoon. Low this evening
  through the day Saturday.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&

$$

DISCUSSION...IRL
MARINE.......SC
HYDROLOGY....SC
AVIATION.....SC
CLIMATE...IRL


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at www.weather.gov/detroit.



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