National Weather Service Raw Text Product

Displaying AFOS PIL: AFDDTX Received: 2018-10-18 11:05 UTC


274 
FXUS63 KDTX 181105
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
705 AM EDT Thu Oct 18 2018

.AVIATION...

Ideal aviation conditions will be in place across SE Michigan as a 
broad region of high pressure moves through the Ohio valley today 
and tonight. VFR clear is expected to last well into tonight as 
westerly flow brings in very dry low level air from the Midwest. 
Early morning satellite imagery indicates the air is too dry even 
for lake effect stratocu off Lake Michigan which suggests little if 
any cloud response over land with daytime heating. Expect wind to 
hold under 15 knots across the region with a few gusts around 20 
knots possible in the MBS area during the afternoon. Moderate 
southwest wind continues tonight with clear sky only giving way to a 
few patches of high clouds by sunrise Friday.  

.DTW THRESHOLD PROBABILITIES...  

* None.

&&

.PREV DISCUSSION...
Issued at 341 AM EDT Thu Oct 18 2018 

DISCUSSION...

Seasonably cold resident airmass now firmly entrenched throughout 
the region, noting early morning temperatures currently settling 
below freezing. Moderation of the existing thermal profile will 
prove modest today, owing to the limited thermal advection as 
surface ridging only slowly exits eastward and effectively delays 
the onset of greater low level southwest flow. The advent of 
gradually increasing upper heights as the mean trough axis releases 
to the northeast will leave a relatively standard response off the 
cold morning readings. Afternoon temperatures projected to reach the 
upper 40s to lower 50s. Increasing stability and depth to the dry 
layer contained within the background of confluent mid level 
northwest flow will afford plenty of insolation potential. However, 
a period of greater lake Michigan moisture flux within the emerging 
southwest gradient may support some downstream expansion of 
stratocumulus into the Flint and Saginaw Valley regions this 
afternoon. 

Shortwave upper ridge axis currently draped across the midwest will 
slip through the region tonight. Ensuing increase in low-mid level 
warm air advection under strengthening southwest flow will 
subsequently provide an additional upward trend in temperatures both 
tonight and Friday. Limited radiational cooling potential tonight 
despite a mostly clear sky, given the likelihood of a well mixed 
boundary layer condition maintained by the firm southwest gradient. 
Lows of upper 30s in the coldest locales. Some increase in mid cloud 
funneling downstream of the next system could muddle the overall 
diurnal temperature response on Friday. Otherwise, pure advective 
component alone should support highs of mid to upper 50s. Turning 
gusty by afternoon within a moderately mixed late day boundary 
layer. Gusts 25 to 30 mph, highest Saginaw Valley and thumb region. 

Closed mid level circulation fixated over the four corners region 
will release a piece of energy into the southern periphery of the 
mean northern stream flow over the next 24 hours. This pv anomaly 
will accelerate eastward on Friday, arriving over southeast Michigan 
early Friday night immediately in advance of a rapidly amplifying 
longer wave northern stream trough. This will provide a window for 
shower development within the associated uptick in mid level ascent 
and along the attendant cold frontal boundary, although somewhat 
limited in potential as greater theta-e advection remains south of 
the region. 

Strong height falls will descend over the great lakes during the 
first half of the weekend, leaving high amplitude troughing to 
define conditions throughout the duration of the weekend. This 
translates into another stretch of well below normal temperatures - 
850 mb temperatures bottoming out at -7 to -9C Sunday morning. 
Initial period of modest cold air advection commences early Saturday 
in the wake of the lead cold front, with a secondary stronger surge 
likely tied to the inbound mid level trough axis late Saturday into 
Saturday night. Another day of gusty conditions given the underlying 
pattern of caa and prospects for a deep mixed layer. Precipitation 
potential Saturday and Saturday night less defined at this stage, 
owing to uncertainty in placement of stronger pva streaming through 
the trough and overall moisture quality/depth. Outgoing forecast 
will maintain a simplistic chance mention during this period. Higher 
confidence for dry conditions during the latter half of the weekend, 
the region residing within the increasingly subsident region
contained along the backside of the departing trough axis.

MARINE...

Marine wind backs to the southwest today as high pressure builds 
across the Ohio valley and speed increases tonight as low pressure 
moves into northern Ontario. The strongest wind tonight will be 
across Saginaw Bay and central Lake Huron where gusts around 30 
knots will be common. A gust near gale force remains possible 
tonight but is expected to be marginal and brief as subsidence and 
low level warm advection continuously lower the mixed layer through 
the night and into Friday morning. The low pressure system then 
deepens considerably Friday afternoon and night which ramps up 
potential for southwest gales with more substantial magnitude and 
duration. Small Craft Advisories are in effect tonight and lead into 
a Gale Watch late Friday through Friday night. Moderate northwest 
wind trailing the front continues Saturday but is projected to 
remain below gales through Saturday night. The weekend finishes with 
high pressure moving across the central Great Lakes Sunday.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

MI...None. 

Lake Huron...Gale Watch from Friday afternoon through late Friday night for 
     LHZ362-363-421-462-463.

     Small Craft Advisory from 8 PM this evening to 4 AM EDT Saturday 
     for LHZ441>443.

     Small Craft Advisory from 2 PM this afternoon to 2 PM EDT Friday 
     for LHZ421.

     Small Craft Advisory from 2 PM this afternoon to 4 AM EDT Saturday 
     for LHZ422.

     Gale Watch from Friday morning through Friday evening for LHZ361.

Lake St Clair...NONE.

Michigan waters of Lake Erie...NONE.

&&

$$

AVIATION.....BT
DISCUSSION...MR
MARINE.......BT


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