Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

000 
FXUS63 KDTX 110834
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
334 AM EST Wed Dec 11 2019

.DISCUSSION...

Lake effect snow showers will continue to drift eastward across 
lower MI this morning. The slight southwesterly wind component is 
directing the bulk of these showers in the typical corridor between 
M59 and I69 but flurries are possible across most of the area. A 
surge of cold air overnight has kept the radar and satellite images 
pretty consistent through the night with cloud tags extending pretty 
far west across Lake MI. This longer fetch has helped the showers 
persist even as convective depths are limited to only 4-5kft (5kft 
in the 11.00Z DTX sounding last evening). This limited vertical 
extent to the showers will limit the potential for more significant 
snowfall. Though the moisture profile is shallow, a good portion of 
the moisture and strong low level lapse rates do fall within the DGZ 
which will help in the efficiency of these showers. A trough axis 
will sweep across Lake MI this morning and across SE MI by about 18Z 
this afternoon. Initially this trough will increase precip potential 
across the area as it picks up the Lake MI moisture plume and pushes 
it east, but much drier air noted in the models rushes in behind the 
trough  for the afternoon which should bring a fairly quick end to 
the showers. All in all, most locations may only see flurries or a 
dusting of snow through the first half of the day, but there is 
potential with convergence along the trough to get a little better 
band to set up which may produce up to a quarter inch of snowfall. 

The trough this morning will usher in the coldest air of the week 
which will keep highs only in the upper teens to mid 20s. The drier 
air will encourage clearing skies under the center of an area of 
high pressure that will center itself over lower MI tonight. We 
could see a quick drop in temperatures under favorable radiative 
conditions sending temps down to around 10F with some of the 
typically colder locations maybe hitting single digits. Working 
against even colder temps is incoming mid clouds ahead of a clipper 
that will skirt across the straits Thursday and Thursday night. 
These clouds should fill in by early morning which is typically when 
min temps bottom out. 

Models continue to keep the the bulk of the warm frontal forcing 
well to the north resulting in a dry day for SE MI. There is a low 
potential of some afternoon showers for the Saginaw Valley and 
Northern Thumb as the center of the low attempts to clip Mid MI but 
at this point will keep it limited to a slight chance mention as 
model soundings are dry in the lowest 8-10kft. A notable increase in 
temperatures as winds flip to southerly and bring highs back into 
the 30s. Warming trend will continue through the end of the week 
with 40s more the norm Friday and Saturday.

Next chance of precip will come Saturday and Sunday as a northern 
stream trough sweeping through the Great Lakes begins to phase with 
a strong southern stream system lifting up the east coast. Warm air 
in place ahead of the trough Saturday will lead to rain but as the 
trough axis passes east by Sunday morning we should see a change 
over to snow or a rain/snow mix.

&&

.MARINE...

A cold front pushes through the region this morning, bringing a 
renewed surge of arctic air that will increase instability and 
deepen the mixed layer over the water today. With a tightened 
gradient in place, the result will be a strengthening west wind. 
Best potential for marginal gale-force gusts remains over northern 
Lake Huron where cold advection and fetch will be maximized, and a 
Gale Warning remains in effect until this evening. Small Craft 
Advisories also remain in effect for the Lake Huron nearshore waters 
from Saginaw Bay to Port Sanilac where wave action will be elevated. 
Scattered snow squalls and freezing spray will be threats across 
Lake Huron into tonight, with significant reductions in visibility 
possible in the heaviest activity. Conditions then improve tonight 
as high pressure passes just to our south, but this relief will be 
short-lived as another low pressure system lifts into the Great 
Lakes on Thursday and brings an increase in southerly flow. The 
potential exists for gales across southern Lake Huron Thursday 
evening.

&&

.PREV DISCUSSION...
Issued at 1156 PM EST Tue Dec 10 2019 

AVIATION...

A steady influx of lake Michigan moisture within cold west-southwest 
flow will maintain an extensive lower stratus into day on Wednesday. 
This will continue to encourage some light snow shower or flurry 
development through the morning hours. Generally VFR conditions 
through this time, although a period of higher intensity snow shower 
activity does remain possible as cold air advections strengthens 
again. PTK northward more favorably positioned to witness this 
activity given the prevailing trajectory, allowing for brief 
disruptions into MVFR/IFR. Gusty westerly conditions will emerge 
during the morning period, reaching near 25 knots at times during 
the day.  

For DTW...Periodic light snow showers/flurries will remain possible 
through the morning hours as metro continues to reside on the 
southern edge of the lake moisture plume. VFR conditions with no 
accumulation expected, as any heavier activity expected to remain 
north. Westerly winds /260-280 direction/ turning gusty Wednesday, 
reaching near 25 knots at times.

DTW THRESHOLD PROBABILITIES...

* Medium for ceilings below 5000 feet tonight and Wednesday. 

* Medium for westerly wind gusts reaching crosswind threshold 
  Wednesday.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Small Craft Advisory until 10 PM EST this evening for LHZ421-441-
     442.

     Gale Warning from 10 AM this morning to 7 PM EST this evening for 
     LHZ361-362.

     Small Craft Advisory until 7 PM EST this evening for LHZ422.

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

$$

DISCUSSION...DRK
MARINE.......TF
AVIATION.....MR

National Weather Service Glossary of Abbreviations