861 
FXUS63 KMQT 021835
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
135 PM EST Sat Jan 2 2021

.SHORT TERM...(Today and tonight)
Issued at 436 AM EST SAT JAN 2 2021

Geocolor satellite imagery showing low cigs propagating from west to 
the east over the U.P. as of 8Z early this morning. A slight wedge 
of clearing from Marquette/Alger County south into Menominee County 
has presented a difficult forecast for overnight lows. The partial 
clearing has resulted in radiational cooling when combined with 
snowpack, thus surface temperatures have quickly dropped into the 
single digits. Observations overnight, including at the NWS 
Marquette office, have shows a very shallow layer of fog that 
developed across several regions. This shallow fog has reduced vis 
to 1/2 mile at times for KSAW airport. The snowpack has created just 
enough moisture in the lower boundary layer to assist with the 
shallow layer of fog. When looking at the 7.3 micron/lower level 
GOES water vapor satellite imagery, a high level of subsidence is 
evident, especially further upstream over the WI/MN regions. This 
strong subsidence aloft in the lower levels of the atmosphere 
coupled with the fast radiational cooling has strengthened 
inversions from the surface to 850mb. This has kept the shallow fog 
present and reduced vis in several areas. 

With the approaching shortwave north of Lake Superior throughout the 
day combined with northwest flow aloft bringing an influx of 
additional warm conveyor belt moisture, have increased the coverage 
for low clouds through later this morning. Guidance initially was 
showing the subsidence taking hold of the area and scouring out low 
level clouds shortly after sunrise this morning, but have decided to 
delay the onset to this transition closer to 18Z. Similar to 
yesterday, this longer duration of low level clouds will limit 
temperatures in the morning. However, once the clearing begins, it 
should happen quickly, resulting in temperatures recovering nicely 
to near 30 degrees. It is important to note that if clearing begins 
over the central U.P. earlier in the morning, this will lead to a 
much higher afternoon maximum for several areas up to near 35 
degrees versus the 30 degree max selected for locations across the 
CWA.

As the day progresses to the overnight hours weak ridging aloft at 
the 500/700/850mb levels will result in slightly warmer levels. 
Surface pressure readings will increase under the dome of high 
pressure that will slide over the Great Lakes toward the east coast 
by Sunday morning. Low level clouds will again return during the 
overnight hours from the lakeshore areas and slowly move inland as 
residual moisture from the lakes and low level inversions take hold 
of the area. However, where clouds take longer to propagate into the 
region, temperatures will decrease rapidly to the lower teens across 
the interior west.

.LONG TERM...(Sunday night through Saturday)
Issued at 134 PM EST SAT JAN 2 2021

Upper air pattern consists of a 500 mb trough in the Ozarks and a 
closed low over NY 00z Mon with a shortwave in the Canadian 
Prairies. The Canadian shortwave moves east and into the upper Great 
Lakes on Mon and this digs into New England on Tue. Pretty quiet for 
this forecast period. 

In the extended, the GFS and ECMWF show a deep 500 mb trough over 
the plains 12z Wed with a ridge in the western U.S. and a shortwave 
ridge over the upper Great Lakes and the Mississippi River valley. 
The deep 500 mb trough forms a closed low over the central plains 
12z Thu that heads east into the southern Appalachians 12z Fri. Huge 
differences show up 12z Sat with the Canadian and ECMWF showing a 
trough over the upper Great Lakes while the GFS has a 500 mb ridge. 
Will be pretty quiet for this forecast period with temperatures 
remaining above normal.
&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1243 PM EST SAT JAN 2 2021

IWD has cleared out and satellite shows CMX will clear out as well 
very shortly. Low stratus remains locked to the higher terrain of 
the central U.P. and thus SAW continues with LIFR cig. There should 
be a period later this afternoon when that cig will lift to MVFR or 
erode into a low scattered cloud deck allowing for a window of VFR 
conditions. But models are insistent that fog and low stratus return 
tonight at SAW so have them going right back down into IFR and then 
LIFR this evening. That low cig will stick around at SAW through at 
least sunrise on Sunday.
&&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 436 AM EST SAT JAN 2 2021

Wind gusts of 20 knots or less will occur until late Saturday 
evening, where stronger gusts will last until early Sunday morning 
on the west half of the lake when SW winds will gust to around 25 
kts. SW winds around 25 kts are expected over the same area again 
during the day on Monday. Light winds 20 kts or less are then 
expected across the lake through at least Wednesday.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&

$$

SHORT TERM...BW
LONG TERM...07
AVIATION...RJC
MARINE...BW