Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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213
FXUS63 KDTX 230503
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1203 AM EST Thu Nov 23 2017

.AVIATION...

Low level wind backed to the south and southwest during the evening
ahead of the next low pressure system organizing over central
Canada. The southwest flow has driven low clouds out of SE Michigan
while mid and high clouds thicken ahead of the Canadian low. The end
result is VFR with some virga on radar over the terminal corridor
through the night and Thanksgiving morning. A few wind gusts near 20
knots will be possible at FNT and MBS during the afternoon as
southwest flow matures ahead of the cold front over the northern
Great Lakes. This front is expected to stall there while the
influence of high pressure over the Ohio valley returns late in the
day through Thursday night.

//DTW THRESHOLD PROBABILITIES...

* None.

&&

.PREV DISCUSSION...
Issued at 253 PM EST Wed Nov 22 2017

Discussion...

Quiet weather pattern expected for the rest of the week. While lower
stratus will erode into tonight, middle deck of clouds will thicken
as a weak shortwave races into central Great Lakes within northwest
upper flow regime. This should bring relatively steady temperatures
overnight as most area fall into the mid/upper 20s right away this
evening and then only oscillate slightly after midnight.

Southwest flow will increase in the wake the surface ridge over the
area as it settles southeast. This will begin a warming trend on
Thanksgiving as locations climb into the upper 30s to lower 40s with
a trend from mostly cloudy to partly cloudy skies throughout the day
as the aforementioned shortwave moves east of the area with time.

With generally clear skies on Thursday night, expect temperatures to
fall back into the upper 20s to around 30 during the evening as the
pressure gradient remains relatively weak through midnight. Expect
temperatures to once again remain relatively stable overnight as the
gradient tightens as deep low pressure shifts east into northwest
Ontario in response to the next strong shortwave digging out of the
Gulf of Alaska region.

This surface low, in the neighborhood of 980 mb, will approach the
Quebec border by Friday evening with southwest flow south and east
of the trailing cold front strengthening further during the day.
Gusts during the best mixing of the afternoon should reach 30 mph at
least with temperatures climbing into the upper 40s to lower 50s in
response to this warm air advection pattern. This cold front moves
southeast across the area Friday night, bringing at least a chance
of showers to the area. No snow shower activity is expected as the
temperatures will still generally be in the lower 40s during model
consensus for precipitation timing (and only fall into the upper 30s
at the coldest by early Saturday morning).

Behind the frontal passage, northwest cyclonic flow will advect
colder air across the region on Saturday with lake-effect clouds and
a few flurries/sprinkles possible throughout the day. High pressure
then builds into the region for Sunday bringing dry conditions while
highs top out near 40 as the thermal trough exits the region. As
high pressure sets up along the East Coast and low pressure develops
over the Central Plains, an increasing southwest gradient under
upper level ridging will allow warm advection to set up over the
region early next week. This will allow highs to make a run for the
low 50s both Monday and Tuesday as dry conditions continue.

MARINE...

Active stretch of weather over the lakes after high pressure slides
across the area tonight. Cold air funneling into the region with
tightening gradient ahead of a weak front will promote strengthening
southwest winds over the waters. Though gusts will stay below gale
force, a period of small crafts for a portion of Saginaw Bay will
needed. The next low pressure system will track through Ontario
Friday pulling a cold front through the Great Lakes Friday night.
Increasing gradient and southwesterly flow ahead of the front Friday
into the overnight will likely reach gale force thus a gale watch
has been issued for the majority of Lake Huron. A secondary cold
front will then drop through on Saturday ushering in a fairly cold
airmass and increased northwest flow.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

MI...NONE.

Lake Huron...Gale Watch from Friday morning through late Friday night for LHZ362-
     363-462-463.

     Small Craft Advisory from 3 AM to 4 PM EST Thursday for LHZ421.

Lake St Clair...NONE.

Michigan waters of Lake Erie...NONE.

&&

$$

AVIATION.....BT
DISCUSSION...DG/JD
MARINE.......DRK


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