Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 172301
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
601 PM EST Sat Nov 17 2018


.AVIATION...

Predominant cigs this evening/overnight will range lower VFR. I-94
corridor will see lowering cigs early Sunday morning as light snow
in fgen forcing lifts just into the region. It appears mvfr/-sn will
persist into late morning before shifting off the the east. Cigs
will edge back up to lower VFR and even scatter out further north at
KFNT and especially KMBS.

For DTW...Flurries are expected to lift back into terminal with fgen
by 10z-12z w/ light snow...vsbys 3-5sm...persisting Sunday morning.
MVFR cigs can be expected at that time, but improve back to lower
VFR by midday once the disturbance initiating the fgen forcing
passes.

.DTW THRESHOLD PROBABILITIES...

* High for cigs aob 5kft.

* High for ptype of SN Sunday morning.

&&

.PREV DISCUSSION...
Issued at 300 PM EST Sat Nov 17 2018

DISCUSSION...

Unrelenting pattern characterized by well below normal temperatures
and episodic light snow potential will continue right through the
early week period. An inconsequential area of light snow/flurries
ongoing this afternoon will gradually contract in scale across
southern sections as existing forcing wanes with time through early
evening. To the north, recent satellite and radar trends suggest a
window remains for some pockets of light lake effect snow showers to
drift into the saginaw valley and thumb through the evening hours.
Little to no accumulation expected going forward through early
tonight.

Cold frontal boundary sags southward into the Ohio valley this
evening, before stalling tonight as the frontal slope becomes
parallel with the mean flow. West to east elongated axis of modest
mid level fgen will emerge along the boundary in the presence of
favorable right entrance region upper jet support during this time.
Slight northward drift of this ascent across the 700-600 mb frontal
slope residing locally will provide a brief window Sunday morning
for light snow to develop across the Ohio border region. Both the
placement and magnitude of this forcing still carries some
uncertainty, but areas generally south of the I-94 corridor appear
more favorably positioned now to witness a period of light snow.
Accumulation potential within the one half to one inch range across
portions of Lenawee/Monroe counties, with a much lower likelihood of
seeing any accumulation up into the I-94 corridor. Conditions Sunday
otherwise governed by the presence of weak high pressure, with a
corresponding lack of meaningful thermal advection solidifying yet
another day of well below normal daytime temperatures. Highs mid-
upper 30s.

Additional shortwave energy digging into the existing mean trough
will provide another round of strong height falls for the early week
period. Lead edge of this amplification process will drive a cold
front into the region late Monday into Monday night. Brief pre-
frontal window Monday for modest thermal recovery under developing
low level southwest flow. The temperature response likely muted
though by the high degree of cloud cover, ensuring daytime readings
remain well below average. Increase in low-mid level ascent as the
frontal boundary and shortwave lift through will provide at least a
chance of snow Monday night. Snowfall potential carries strong
reliance on defining the placement of the best mid level dynamics
tied to the main pv feature and attendant upper jet axis, with
current model projections suggesting a greater chance exists over
northern lower MI.

A strengthening thermal trough and persistent cloud cover will bring
colder temperatures to Michigan by Tuesday as highs only peak in the
upper 20s to lower 30s followed by lows in the 20s. Flow will turn
more zonal late Tuesday into early Wednesday which will help
moderate temperatures as warmer westerly flow fills in, allowing
highs to peak in the mid to upper-30s as h850 temperatures climb
from an average of -12C to -5C. The back edge of a second thermal
trough will filter in late Wednesday to Thursday and will return
h850 temperatures back down to an average of -13C, once again
capping highs in the low to mid-30s.

Confidence remains high regarding a pattern shift during the late-
half of next week as moves across the Plains late Thursday into
Friday and strengthens across northern TX/southern OK, strengthening
a ridge across the eastern states. Surface high pressure centered
across the Great Lakes into Ontario will bring extended periods of
sunshine Thursday into Friday and will aid in increasing
temperatures Friday into the weekend as anticyclonic flow takes hold
when the high pressure travels east into New England. The warm-up
will be marked by h850 temperatures increasing to 0-4 C Friday into
the weekend and will translate to daytime highs peaking in the mid-
40s starting Friday. The ECMWF and associated MOS guidance is less
aggressive with waa next weekend, so opted to not increase highs
into upper-40s per yesterday`s discussion.

Negatively-tilted shortwave trough and weak cold front will bring
the chance for precipitation throughout Saturday. If the trough
moves in early enough, a chance to see a wintry mix will be
possible, however, confidence is too low to at this time to discern
precipitation type.

MARINE...

A tightening pressure gradient between high pressure and an area of
low pressure tracking across southern Hudson Bay will lead to gusty
winds over northern and central Lake Huron Sunday, with gusts of 20-
30 knots common. Moderate southwesterly flow will continue to linger
through the early week period with broad high pressure in place.

&&

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

$$

AVIATION.....DG
DISCUSSION...MR/AM
MARINE.......JVC


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