Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
FXUS63 KDTX 251924
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
324 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.
Cold northwest flow will maintain unstable conditions across area
waterways today. Small craft advisory conditions will persist
during this time for all near shore waters of Lake Huron including
outer Saginaw Bay. Gusts of 25 to 30 knots will be common across
the open waters, but winds are expected to remain below gale force.
Winds and subsequently waves will gradually diminish late today and
tonight as high pressure builds into the region. Winds will
increase out of the east Wednesday and Wednesday night as low
pressure lifts toward the region. Strongest winds expected
Wednesday night and early Thursday, where gusts of 25 to 30 knots
are again expected. While the potential for a period of near gale
force is still possible over portions of the open waters, the
current forecast maintains gusts below gales at this time.
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
Issued at 141 PM EDT Tue OCT 25 2016
Diurnal cu field underway under with the inversion around 4kft
holding CIGS around 3-4kft. This will persist through the afternoon
and should quickly scatter out this evening. Skies will clear out in
the lower levels but cirrus streaming in from upstream will keep
some upper level clouds around. Northwesterly winds will weaken
tonight while becoming easterly by morning. Clouds will be
increasing while CIGS lower as the next low pressure system tracks
just south of the MI border. The warm front remaining to our south
will lead to overcast skies and increasing easterly flow. Start time
for precipitation looks to remain outside the current taf window.
For DTW...Winds will continue to bounce around from 300-340 this
afternoon for a couple more hours. High pressure overhead will cap
off the winds around 7 to 8 knots before decreasing this evening.
Diurnal CU around 4kft will take us into the evening hour with a
rapid decline in coverage after 23Z.
//DTW Threshold Probabilities...
* high confidence in cigs aob 5000 ft this afternoon.
Lake Huron...Small Craft Advisory until 8 PM EDT this evening FOR LHZ421-441>443.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
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