Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 252300

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
700 PM EDT TUE OCT 25 2016


There was a large diurnal component to the cloud cover this
afternoon. This has led to a rapid decrease in their coverage with
the loss of daytime heating. The low level flow will veer from the
NNW this evening to the east by daybreak Wed morning. The airmass
across Lakes Huron and Erie is cold enough to generate a lake
response. This and the presence of a rather deep inversion based
between 3500 and 4500 ft will likely result in a strato cu field
attempting to push into the TAF sites from Lake Huron overnight.
There is some uncertainty as to whether or not this will lead to a
bkn or ovc cig as recent hi res solutions suggest the better
likelihood of greater cloud coverage will be over the thumb region
as the flow veers rather quickly. Given this uncertainty, a mention
of scattered clouds in the 3k-4k ft layer will be carried through
daybreak at this time.

For DTW...The low level flow will likely keep the sub 5k ft clouds
north of metro. The main concern will be the potential for a brief
period of lower clouds to advance into the area from the northeast
overnight prior to the winds veering more easterly. There will be a
better chance of a sub 5k ft cloud layer late Wed morning as the
winds veer toward the southeast, resulting in a trajectory off Lake
Erie. These clouds may actually expand during the course of the day
as a region of widespread light rain slowly overspreads the area
from southwest to northeast.

//DTW Threshold Probabilities...

*  Low in ceilings below 5000 ft tonight through daybreak Wednesday.
   Moderate late Wednesday morning through afternoon.


Issued at 346 PM EDT Tue OCT 25 2016

Weak shortwave energy emerging over the front range of the Rockies
this afternoon will encounter a weak static stability environment
favorable for a self-deepening scenario driven by latent heat
release over the Lower Missouri and Upper MS River Valleys tonight.
Strong deep layer isentropic ascent will overspread the area late
Wednesday morning through the afternoon as the surface low
translates from eastern Nebraska to north-central Illinois.
Development overcast skies from south to north will be followed by
widespread virga as precipitation works to overcome dry air
reinforced by stout easterly flow. Expect a band of rain to lift
from south during the late morning through the early afternoon in
advance of stronger forcing.

Noteworthy model spread exists with regard to the position of the
surface low by Wednesday evening. This appears to be due, initially,
to tonight`s convection pulling the height falls in the higher
resolution runs further north while synoptic-scale forcing dominates
the low track in the global models. As strong isentropic ascent
ramps up within the classic right entrance region over SE Michigan
and system relative fgen becomes increasingly focused in the lower
portion of the troposphere, the exact position of the attendant warm
front will be important as it will largely dictate how wet/dry our
southern counties are during Wednesday afternoon. Trailing energy
currently over the Pacific Northwest coast at 18z this afternoon is
initialized reasonably well by the GFS and especially the ECMWF -
which made a strong move toward the 12z GFS in allowing the energy
to make a faster entrance into the Great Lakes, forcing the surface
low toward a more northeasterly track by late Wednesday night into
Thursday morning. It is worth noting that the GFS/EC now handle the
timing of this energy in quite similar fashion, but the low track of
the EC seems unexpectedly further south. The forecast is largely
biased toward GFS solution which is essentially a suppressed version
of the convective response observed in the high res along with a
dynamically (and climatologically) preferred track toward the tip of
Lake Erie. Widespread stratiform rain can be expected by late Wed
evening into the overnight period to go along with strong east winds
gusting toward 20 kts and temperatures in the mid 40s falling as low
as the upper 30s. Cyclonic flow and lingering moisture within the
thermal trough will ensure skies remain cloudy after lingering
precip departs early Thursday. Highs will struggle out of the mid
40s Thurs as h85 temps stay solidly in the negative single digits
beneath plenty of clouds.

A broad area of high pressure situated over the eastern half of the
US will bring dry conditions to our area throughout Friday
afternoon. The next chance for rain will enter Friday night into
Saturday, mainly north of I-69, as low pressure travels eastward
across Ontario. Additional chances for precipitation will return on
Sunday as a second low from the Great Plains pushes over MI
throughout the day. Confidence for the early half of next week is
increasing regarding a possible warming trend. A broad area of high
pressure centered over the western Atlantic and low pressure
situated over the northern Great Plains will allow S/SW winds to
usher in warmer temperatures, with 850 mb temps sitting at 14C in
the GFS and 8C in the ECMWF models at 18Z. Temperatures returning
into the 60s will not be out of the question Monday - Tuesday.


Northwesterly flow will continue to decrease through the remainder
of the afternoon and evening as high pressure slides over the
region. Current small craft advisories in effect for Lake Huron
nearshore zones will be cancelled as decreased winds have allowed
wave heights to subside below criteria. Wind will turn easterly
Wednesday as we reside on the north side of a warm front that will
lift into the northern Ohio Valley. The associated low will then
track east along the front Wednesday night. The easterly winds will
increase through the day tomorrow peaking Wednesday night and
Thursday before turning northerly Thursday evening. Winds are
currently expected to remain below gale force but will likely
necessitate small craft advisories once again as winds gust to 25 to
30 knots.


A low pressure system developing over the central Plains will track
through the northern Ohio Valley Wednesday night, resulting in a
widespread rainfall event locally Wednesday through Thursday. The
heaviest rainfall will occur late Wednesday into Wednesday night
before tapering off Thursday. This system will result in a broad
area of rainfall with amounts around three quarters of an inch
through expected.


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



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