Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
FXUS63 KDTX 191057
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
657 AM EDT WED OCT 19 2016
Ideal radiational cooling has led to patches of shallow ground fog.
Whatever fog is left should lift 12z-13z. Otherwise, VFR conditions
are expected under high pressure with increase mid to upper level
clouds tonight as shortwave begins to lift into area. Conditions
will then deteriorate pretty quickly just beyond the forecast period
as area of rain expands over area mainly post-12z Thursday as this
wave...and associated surface low pressure...ejects through the Ohio
For DTW...Any fog during the first hour or the forecast will be very
shallow and of little significance. All obstructions to forecast
will basically hold off until 12z-14z or so Thursday morning as
rain/stratus fill in steadily.
//DTW Threshold Probabilities...
Issued at 309 AM EDT Wed OCT 19 2016
Surface high pressure will continue to expand into Lower Michigan
today providing dry and quiet weather. Mid/high clouds will begin to
increase late ahead of the next low pressure system however. Decent
mixing heights (5000 ft+) and sunshine will help boost temperatures
into the upper 60s to low 70s this afternoon. While these readings
are 6-8 degrees cooler than yesterday, they are still almost 10
degrees above normal.
Upper trough west of the Rockies will slide through the Central
Plains tonight and Thursday. Height falls and good upper divergence
from right entrance region forcing will allow surface low pressure
to quickly spin up over the Tennessee Valley before lifting up across
Ohio and the Eastern Great Lakes. Elevated portion of the warm front
(700-850mb) will lift into Michigan as the low tracks southeast of
the area late tonight and Thursday. A cold front associated with an
upper low tracking into Ontario will meanwhile start to slowly push
down into Michigan, helping to guide moisture into the area and
tighten the thermal gradient. Overall, isentropic ascent looks
rather weak (GFS/NAM) and confined to the far Southeast corner of
the state, but NAM shows a good amount of more upright forcing from
mid-level FGEN (700-850mb) very late Wednesday night into Thursday.
Low static stability above the FGEN layer if it does indeed settle
into the area would help provide a generous coverage of rainfall as
PW values rise to 1 inch. Question will be how far into Michigan
rain shield extends, with expectation for a sharp edge provided by
dry northwest flow behind the Canadian cold front. Better
instability (thunder chances), forcing, and moisture is also
expected to remain southeast of the area, and lower coverage than
currently forecast could result if lower portions of the front light
up instead. Forecast overall was changed little from previous, with
likely pops still running roughly along and south of a line from PHN
to PTK to ARB.
Cold front will slowly be pulled through Southeast Michigan late
Thursday and Thursday night, ushering in much cooler air that will
drop max temps into only the low 50s by Friday. Drier weather is
expected overall through the end of the week as a ridge of high
pressure slowly slides in, but may see a few lake effect rain
showers over the thumb Friday. Temperatures are expected to drop
into the 30s Friday night, but northwest gradient looks strong
enough at this time to mitigate frost threat. Some model solutions
also brush the area with a backdoor cold front Friday night into
Saturday, which would increase cloud cover. Cool weather will
continue into the weekend with max temps in the upper 40s to low 50s
on Friday and mid 50s to near 60 on Sunday.
A ridge of high pressure will bring favorable marine conditions
during the day today. However, this period of relatively benign
weather will be short as low pressure lifts into the Ohio Valley
late tonight into Thursday night. A tightening pressure gradient to
the north of this system will bring increased northerly flow from
late Thursday into Thursday night.
This strengthening onshore flow over Lake Huron will most likely
lead to the necessity of Small Craft Advisories over the nearshore
waters. Windy conditions will then persist from Friday into Saturday
as this low deepens substantially as it lifts into the eastern Great
Lakes. Small craft advisory conditions will likely persist during
this time frame. At this time, it appears gusts will remain just
short of gale force.
Low pressure will lift into the southern Ohio Valley late tonight
into Thursday and then shift east into the northeast CONUS late
Thursday night into Friday. This system will likely bring rain to
parts of Southeast Lower Michigan from overnight tonight into at
least Thursday evening.
Given the fact that the track of this system is so far south and
southeast of the area, a tight gradient in rainfall amounts can be
expected from northwest to southeast across lower Michigan. At this
time, it appears that one quarter of an inch of rainfall will be
possible along the Irish Hills with amounts closer to one half an
inch possible further southeast from parts of Metro Detroit south to
the Michigan and Ohio state line.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
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