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fxus63 kdtx 171653 
afddtx

Area forecast discussion
National Weather Service Detroit/Pontiac Michigan
1153 am EST Mon Dec 17 2018



Aviation...

The ongoing low level cold air advection augmented by a diurnal
contribution will maintain a chaotic coverage of stratocumulus
through the afternoon and evening hours. Recent satellite trends
suggest the degree of dry air accompanying this cooling northwest
flow may allow for some breaks in the coverage at times. Cigs
hovering near or just above 3k ft during this time. Timing the
dissipation of clouds continues to carry a higher degree of
uncertainty tonight. Mixed signal yet within recent model guidance,
differences owing to whether dry air can work sufficiently into the
existing moist layer to scour out existing cloud. Going forecast
will continue to highlight the early morning period for increasing
clearing potential. An intermittently gusty northwest wind this
afternoon will ease with sunset.

Dtw threshold probabilities...

* moderate for ceiling 5000 ft or less through the evening. Low
probability tonight.

&&

Previous discussion...
issued at 400 am EST Mon Dec 17 2018

Discussion...

Regional satellite and mesoanalysis reveals strongly confluent flow
forcing a cold front southward through the lower peninsula at press
time. Surface temperatures range from the low to mid 30s ahead of
the front and immediately behind it beneath nocturnal stratus to the
teens and 20s in the unmodified airmass over Minnesota and
Wisconsin. Cross-section analysis shows the lead edge of the cold
air aloft extending well ahead of the surface front, which is
currently still back over northern lower. In fact, latest rap and
06z NAM suggest 850mb front is already about halfway through the
cwa, supporting rapid boundary layer growth as soon as the surface
front passes later this morning. Deep Post-frontal northwest flow
will ensue with winds gusting over 20 mph and rapid expansion of
stratocu limiting temperature recovery as cold advection continues
through the day. Slight upward tick in temps is likely during peak
heating simply due to mixing, but otherwise little movement from
current readings. Forecast soundings and upstream trends offer
increased confidence in persistence of stratus through tonight as
moisture remains trapped beneath lowering inversion heights. Nudged
overnight low temperatures up accordingly, but there remains plenty
of room for an additional upward adjustment. Any clearing potential
will likely be closer to Tuesday morning as the surface ridge
positions directly overhead coincident with maximum subsidence.

Little change for Tuesday as the mid-level thermal trough remains in
place. A moderating trend will commence Tuesday through Thursday as
heights gradually build in spite of suppression due to shortwave
energy tracking across southern Canada and the northern Great
Lakes. The resulting rather Flat Ridge will be sufficient to allow
temperatures to recover into the 40s in spite of ample mid/high
debris.

The active subtropical jet noted on full disk imagery will be key to
the slow evolution of the pattern during the week, and likely the
greatest source of uncertainty. Currently supporting broad/weak
upper energy near the Mexican border, this energy will essentially
act as a readily available as a pv Reservoir as mid-latitude
troughing amplifies over the Front Range in response to strong
Pacific jet energy coming onshore early this week. The resultant
longwave trough is progged by the 00z ec to extend clear to
Guatemala, which is guaranteed to cause a high degree of sensitivity
in the solution space. One way or another, a significant cyclone is
likely to emerge over the eastern US. Initially warm, eventual
infiltration of cold air as northern stream energy feeds into the
trough will likely support rain ending as snow along the deformation
zone track.

Marine...

A period of cold air advection following an early morning cold
frontal passage will deepen the over-lake mixed layer and will
support gusty northwest winds today. Wind gusts will primarily top
out around 30 knots. The exception will be across north-Central Lake
Huron where a few gusts to gale force will occur this morning. Winds
will gradually decrease this afternoon as both the gradient relaxes
and Post frontal cold air advection weakens. High pressure will
build into the region from the west tonight and drift across lower
Michigan on Tuesday. This will result in a substantial decrease in
winds and waves tonight. The high will drift to the East Coast tues
night into Wednesday, resulting in strengthening southwest winds on
the back side of the surface high. Warmer air will also advance into
the region, limiting over-lake mixing depths and thus keeping wind
speeds in check.

&&

DTX watches/warnings/advisories...
Michigan...none.
Lake Huron...Small Craft Advisory until 4 am EST Tuesday for lhz421-441>443.

Gale Warning until noon EST today for lhz361-362.

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

$$

Aviation.....Mr
discussion...jvc
marine.......SC

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