Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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005
FXUS63 KDTX 261810
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
110 PM EST Sun Feb 26 2017


.AVIATION...

Weak system with diffuse shortwave energy will push across the
northern great Lakes this afternoon. The system will bring an axis
of modest, midlevel moisture across the region. Returns on regional
mosaic generally outlines this moisture axis and represents largely
virga or snow flurries to the west of the area. The big negative for
light snow to reach the ground at KMBS and KFNT will be the layer of
dry air in the lowest 6000 ft, in addition to very rapid transition
of the trough axis from netural to negative tilt. This change in
orientation will make any duration of moisture and forcing extremely
brief. The main aviation narrative remains the southwest winds
today. Observational and forecast trends suggest the ongoing
forecast is a touch on the high side. With the winds expected to
increase this afternoon dependent on mixing depths, will largely
hold to the inherited wind forecst. For tonight, a decaying cold
front will push into southern lower Michigan while stalling out.
Models suggest some better midlevel moisture filling in along this
boundary but confidence is low in coverage of BKN VFR cigs. The
potential for some very light hz exists at daybreak Monday, with any
fog low.

For DTW...Southwest winds will increase this afternoon. High
confidence in wind gusts reaching and exceeding 25 knots with medium
to low confidence in winds reaching 30 knots. Most recent hourly
probs show a guidance trend for weaker forecasted wind gusts this
afternoon.

//DTW THRESHOLD PROBABILITIES...

* None.

&&

.PREV DISCUSSION...
Issued at 345 AM EST Sun Feb 26 2017

DISCUSSION...

Today will turn out a little warmer than Saturday, at least on the
thermometer, as it will feel just as harsh due to windy conditions
persisting. Wind gusts around 20 mph during the morning will return
into the 30 mph range around noon and could reach 40 mph in the Tri
Cities and northern Thumb by mid afternoon. The southwest direction
will bring in some warmer air and help lift temperatures to around
40 across the area while feeling more like 20. A warming trend then
remains on track to quickly get underway to start the week.

The strong wind field today will be supported by a wave of low
pressure moving quickly through the northern Great Lakes up against
expansive high pressure centered over the SE states. The resulting
compression of the surface pressure gradient will keep the wind
elevated and gusty as boundary layer depth builds through the day.
The SE states surface high will extend into Lower Michigan during
the morning before being directed eastward by afternoon. Early
morning satellite imagery shows this process being effective at
sweeping out the low clouds along and east of the ridge axis. The
cloud edge is a reasonable representation of the low level thermal
trough departing the area as well. The ensuing southwest flow
between the systems will then continue to supply warmer and much
drier air through the low levels. This will be important in
determining how much if any snow might occur as the northern stream
wave moves through the region. Prospects look slim as model
depictions of mid level isentropic lift/theta-e advection occurring
ahead of the wave continue to appear weak and moisture-starved.
Model soundings indicate the dry air holding through the low levels
supporting no more than a low chance POP for trace amounts of snow
reaching the ground in the Tri Cities area. Expect mid level clouds
to return and virga to show up on radar over the rest of the region.

The cold front trailing this system will wash out over central Lower
Michigan tonight in favor of renewed high pressure by Monday. This
will be the result of a rebound in the 500 mb height pattern between
the departing northern stream wave and a new long wave trough
developing out west, the continued development of which will
accelerate the warming trend in the Great Lakes Monday into Tuesday.
Surface low pressure development in the lee of the Rockies through
the Plains will direct persistent southerly flow into Lower Michigan
during this time. The temperature trends look solid as they are
being governed by large scale features. Timing the next round of
precipitation has lower predictability due to the dependence on
short wave energy arriving from the long wave trough Monday night
into Tuesday. The good news here is that, even if faster solutions
verify, surface temperatures are expected to be above freezing at
southern locations that have a chance POP prior to 12Z Tuesday
morning. There is then a time window for readings to warm above
freezing at points north Tuesday morning before moisture arrives
there. This would be followed by another generous helping of
rainfall across the area Tuesday through Wednesday as the primary
low pressure system moves along the surface front stalled over the
region. Colder air will then fill back in over the Great Lakes on
the heels of this system to finish the week.

MARINE...

A gale warning remains in effect today through this evening for
Saginaw Bay and central Lake Huron with small craft advisories in
effect for the remaining marine areas. Moderate westerly flow during
the morning will become southwest and increase again during the
afternoon into this evening as low pressure moves through the
northern Great Lakes. The associated cold front will settle over
Lower Michigan and central Lake Huron tonight and dissipate in favor
of high pressure by Monday morning. Favorable marine conditions in
the form of light south wind and milder air will then continue
through Tuesday. The next low pressure system is projected to arrive
Wednesday on a track through the central Great Lakes followed by
colder air on moderate northerly wind for the end of the week.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Gale Warning until 10 PM EST this evening for LHZ362-363-421-422-
     441-462.

     Small Craft Advisory until 7 PM EST this evening for LHZ442-443.

Lake St Clair...Small Craft Advisory until 7 PM EST this evening for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory until 7 PM EST this evening for LEZ444.

&&

$$

AVIATION.....CB
DISCUSSION...BT
MARINE.......BT


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at www.weather.gov/detroit.



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