Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Detroit/Pontiac Michigan
619 am EDT Wednesday Oct 22 2014
Moist northeast flow will maintain an extensive stratus deck through
the latter half of the morning. Recent observations suggest
ceilings will largely remain in high MVFR /2000 to 3000ft/. Drier
air will make better in roads this afternoon as high pressure builds
into the region. This is expected to result in a more progressive
clearing trend during this time. A clear sky and light wind with
high pressure in control tonight.
//Dtw threshold threats...
* high confidence in ceilings below 5000 feet this morning. Low
confidence this afternoon.
Previous discussion...issued 350 am EDT Wednesday Oct 22 2014
Short term...today and tonight
Southeast Michigan holding firm this morning within the existing middle
level cyclonic flow attendant to the outer periphery of the
sprawling closed middle level circulation positioned over the middle
Atlantic coastline. Retention of a modestely deep north-northeast
gradient under this pattern sustaining at least a weak cold air
advective component...and likely providing some degree of moisture
flux contribution off Lake Huron. The net result early this morning
being the solidification and renewed westward expansion of stratus
accompanying this cooling/moistening of the sub-inversion layer.
Latest sounding analysis and low level relative humidity fields continue to suggest
the extensive dry layer existing at the edge of building high
pressure just upstream will take some time to make better inroads
locally today. This points to a mostly cloudy first half of the
day...before increasing subsidence and dry air advection aides in a
progressive clearing trend during the afternoon. Highs today in the
lower and middle 50s.
High pressure dominated conditions expected tonight. A diminishing
gradient flow...clear sky...and dry middle level environment continue
to lend confidence toward witnessing a strong radiational cooling
response overnight. Lows making a run into the upper 20s in the
Long term...Thursday through Tuesday
Thursday will start with ridging at the surface and aloft over
Southeast Michigan. This should maintain quiet and dry conditions
over the area. Sunshine and weak thermal advection (h850 temperatures up to
8c) will help boost temperatures into the middle 50s. Models then
continue to show some minor differences with how they handle energy
within the upper trough now seen on water vapor stretching from the
Canadian rockies down towards The Four Corners. NAM is a fast
outlier with the energy into the Great Lakes...while the Euro/Gem
now split the energy...taking the bigger piece down into the
Tennessee Valley while the rest crosses Michigan late Thursday night
and Friday. These solutions continue to show most of the moisture at
the middle and upper levels...and show little in the way of a low-level
forcing mechanism. This continues to support a dry forecast with
just an increase in clouds...but will continue to monitor model
solutions and water vapor imagery in case changes are warranted.
Medium-range models then continue to show strong continuity with a
larger upper low over the Gulf of Alaska diving through Ontario
Friday night through Saturday night. Increased mixing ahead of a
cold front associated with this feature should boost temperatures
closer to 60 on Saturday...as we mix into warmer air aloft that
should arrive late Friday. Dry cold front is then prognosticated to drop
through Saturday evening...bringing an increase in winds and
dropping temperatures back down into the 50s for Sunday.
GFS/Euro then in strong agreement with upper ridging sliding over
the area Sunday into Monday...continuing the stretch of dry weather.
An approaching trough should however boost wind speeds on
Monday...then bring a chance for showers on Tuesday.
Marine...gusty winds and large waves over Lake Huron will continue
to subside through the early morning hours as low pressure moves
towards the East Coast and a ridge of high pressure begins to settle
into the central Great Lakes. The high will remain overhead into
Thursday...bringing fairly calm conditions and dry weather. The next
period of increased winds is expected Saturday into Sunday as a cold
front drops through the area. Small craft advisories may be needed
for portions of Lake Huron.
Small Craft Advisory...nearshore waters from Port Austin to Port
Huron including outer Saginaw Bay...until 8 am Wednesday.
Lake St Clair...none.
Michigan waters of Lake Erie...none.
You can obtain your latest National Weather Service forecasts online
at www.Weather.Gov/Detroit (all lower case).