Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 190857

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
357 AM EST Fri Jan 19 2018


Upper level flow eases into a period of lower amplitude westerlies
over the next 48 hours, as a larger scale pattern adjustment
refocuses the predominant north-central Canadian lower height
anomaly back north of the border, leaving flow of pacific origin to
govern conditions. Steady low level southwest flow tucked beneath a
gradually increasing upper height field will sustain a stretch of
above normal temperatures lasting into the weekend. Most noteworthy
increase in the thermal profile expected today, as the 850-925 mb
layer warms a solid 5-7 degrees from readings noted yesterday,
thanks in part to a low level column that remains absent of
meaningful moisture. Thickening high cloud through the day, but no
signal per recent observations or near term model guidance to
suggest low stratus becomes a concern until the weekend. Highs
largely in the upper 30s. Nocturnal cooling potential tonight
contained by a persistent 10kt southwest gradient and thick canopy
of cirrus. Lows in the vicinity of 30 degrees.

Milder conditions hold firm throughout the weekend period. Any
additional warming of the resident airmass will remain muted as the
southwest gradient eases and low stratus becomes an increasing
factor. This will place maximum daytime readings around 40 degrees
each day. Lack of tangible ascent will favor dry conditions through
at leas the first half of the weekend. Noted increase in low level
saturation may introduce the potential for some drizzle to develop
starting Sunday morning. However, prefer a conservative stance at
this stage with model guidance often providing an overzealous
response with a significant contribution to the near surface moist
layer from snowmelt /see NAM and ARW/. Should drizzle materialize,
there could be a small window where brief sub-freezing temperatures
support freezing drizzle.

Elongated area of strong height falls crashing into the west coast
tonight will organize into a deep closed system as it enters the
central conus by late this weekend. This system will then slowly
wobble through the great lakes early next week. Maturing warm sector
environment immediately downstream will send a warm frontal
structure toward lower Michigan Sunday night and Monday. Period of
isentropic ascent across the frontal slope will bring increasing
rainfall potential during this time.  Forcing transitions to a
period of deep layer dynamic ascent sometime Monday as both low and
upper level jet forcing impinges on the region. Given the degree of
mid level theta-e advection, an elevated rumble of thunder not out
of the question Monday. Mildest day of this stretch, with readings
well into the 40s.

Cooling thermal profile throughout Tuesday in the wake of the
surface low passage. Moist cyclonic flow beneath the passing 500 mb
cold pool will bring the potential for some snow showers.  This
inbound air mass will lack any arctic connection, leaving conditions
still rather seasonable as the coldest of this air settles in for
Wednesday.  Renewed warming trend then commences late next week.



The Great Lakes is positioned on the northwest side of an area of
high pressure centered over the Gulf Coast states and will remain so
heading into the weekend. This will keep a persistent warm southwest
flow in place through Saturday night before they back to
southeasterly ahead of the next low pressure system. This low will
deepen as it starts lifting into the western Great Lakes on Sunday
before working through the central Great Lakes on Monday and Monday
night. Winds will be elevated but gusts will be tempered by warm air
advection heading into the weekend.


Issued at 1213 AM EST Fri Jan 19 2018


Quiet aviation period during the next 24 hours. Development this
evening has been extensive stratus deck that is just settling down
into northern Saginaw Bay this evening behind the vigorous
shortwave. Current satellite trends have this staying out of the
KMBS terminal. Second development has been very well mixed gradient
flow to the south of the shortwave. Suspect that some nocturnal
processes are at play too, ducting stronger momentum under inversion
that is down to 900mb. Southeastern Michigan will remain in
relatively close proximity to the jet stream axis aloft, which will
keep high cloud over the region. For this reason, went fairly bullish
on opaque high cloud.


* None.


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



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