Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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786
FXUS63 KDTX 180457
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1157 PM EST Fri Feb 17 2017

.AVIATION...

The surface warm front is on the way through Lower Michigan during
the early morning. The passage of the front will be marked by
veering wind to the southwest with a modest increase in speed.
Temperatures rising back into the 40s will be met with dewpoint
rising into the mid 30s as well which still could produce some MVFR
fog or haze while flowing over the cold ground. Otherwise, only a
few patches of high clouds are associated with the front. Assuming
the warm sector remains decoupled, then low level wind shear will be
associated with faster flow above the surface based inversion
reaching around 40 kts at the top of the shear layer. This will lead
to breezy conditions by afternoon as boundary layer growth builds
into the faster wind aloft. Gusts around 20 knots are reachable
across the area based on upstream observations from Friday afternoon
and considering the low level jet will be weakening through the
morning.

//DTW THRESHOLD PROBABILITIES...

* None.

&&

.PREV DISCUSSION...
Issued at 343 PM EST Fri Feb 17 2017

DISCUSSION...

Quiet stretch of weather in terms of precipitation through the early
part of next week as ridging will dominate much of the Central
Plains into the Great Lakes. With deep troughing over the west
coast, resultant ridge will continually build over the Plains and
spill into the region as wave train to our north keeps folding over
the ridge. This wave train will be in the quasi zonal jet just north
of the international border. An upper low traversing the southern
states through Sunday will help prevent stronger warm air advection
from building up through the plains yet a warm front currently
lifting into southern MI will lift into mid MI tonight allowing a
warm up to commence. Heights already building today will peak
tonight around 563dam at 500mb with 850mb temps nearing -12C passing
over the area. This will throw off the typical nocturnal cooling
trend with both temps and dewpoints on the rise after the frontal
passage after 06Z.

Main question overnight will be fog potential as we usher in
dewpoints ranging from 35-40F over still frozen ground. Confidence
is low due to the slightly enhanced wind field due to deeper mixing
in the warm sector and decent dewpoint depressions currently. Could
see some light fog or haze around tonight into Saturday morning but
will hold off on mention in the forecast for now. Saturday will then
be warm and breezy with potential record highs being set. With such
warm air just off the deck, it won`t take much diurnal mixing to
bring that down to the ground. As was mentioned in the previous AFD,
high temps may actually break 60 over much of the forecast area.
This will likely tie or break record highs for the 18th. For Detroit
62 (1976); Flint 56 (2011); Saginaw 53 (1981).

A shortwave will traverse the northern Great Lakes on Saturday with
an associated cool front dropping through later that evening. Flow
will become more westerly but air is not much cooler behind the
boundary as ridging remains strong. So highs will likely remain in
the 50s on Sunday as mid level heights rebound. Sunday will be dry
again with plenty of sun around.

Mild temperatures will persist into next week as heights remain
elevated across the region with the strong west coast trough in
place. This west coast trough releases at the hands of a nearly 150
knot jet making landfall Saturday night/Sunday. This trough will
track across the country reaching lower MI on Tuesday. This will
bring the next chance of precipitation which will be in the form of
rain. Warmer temperatures near 50 will remain through much of the
week as zonal flow holds over the region with the main thermal
gradient locked to our north.

MARINE...

Modest southerly flow this evening will turn to southwesterly by
Saturday morning. The strongest winds will be over outer Saginaw Bay
into the central body of Lake Huron. However, wind gusts should
remain below 25 knots. Winds will become more westerly later on
Saturday, shifting the focus of moderate winds to the north arm of
Lake Huron. The modest winds and mild conditions will support
substantial ice breakup.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

MI...NONE.
Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.

&&

$$

AVIATION.....BT
DISCUSSION...DRK
MARINE.......Mann


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