Scientific Forecaster Discussion
fxus63 kdtx 051050
Area forecast discussion
National Weather Service Detroit/Pontiac Michigan
550 am EST Thu Dec 5 2019
Low level dyring has eroded most of the MVFR based status that
affected the area last evening. Ongoing mid level subsidence and the
advection of a warmer and drier low level airmass across lake mi and
into srn lower mi today will result in a diminishing trend to the
remaining 4-5k ft strato cu layer; which is already in progress per
recent satellite trends. A weakening wind field with just some
increasing mid level clouds will then prevail through the afternoon
and evening. A mid level frontal system and sfc low set to track
across the area overnight will likely bring some light snow
(possible rain) to mbs. The probabilities for any precip will be
much lower from fnt south.
For dtw...the westerly winds will diminish below 8 knots after 19 or
20z roughly. Current satellite trends also suggest the 5k feet cloud
deck will erode by late morning.
Dtw threshold probabilities...
* moderate in ceilings at or below 5000 ft this morning.
issued at 422 am EST Thu Dec 5 2019
Snow showers will continue to diminish in coverage and intensity
this morning as mid-level northwest flow weakens and backs zonally
from an upper level trough pivoting toward the North Atlantic. This
will effectively cut off the lake enhanced moisture corridor which
persisted well into the overnight hours, coincident with an axis of
favorable DPVA. Mid-level vapor imagery aptly illustrates the
forcing transition over the eastern counties where the back edge of
the current shower activity continues to erode.
Dry air advection with isentropic downglide will increase dewpoint
depressions in the 850-700 mb layer for the afternoon hours.
Compressional warming from elevated anticyclonic flow will
contribute to the development of an inversion layer which will help
limit low cloud depths. Skies remain mostly cloudy for much of today
with only slight surface temperature increases owing to a muted
diurnal curve. This will keep highs in the mid to upper 30s once
again. Dry afternoon conditions give way to increasing pops for the
evening and overnight segments as an Albert clipper descends on
central lower Michigan. Moderate confidence persists in keeping the
bulk of the precip north of the M-59 corridor given strong model
consensus regarding track and intensity as the surface low is driven
along by a deepening shortwave. Precip type remains more uncertain
given warm near-surface layer temperatures, but forecast soundings
do suggest nearly all snow north of I-69 while a rain-snow mix is
plausible along the southern fringe of the precip shield. As far as
accumulations go, most areas that do see pure snowfall will end up
with around a half inch. One inch totals are possible for Huron and
The low will race eastward overnight reaching Toronto by daybreak.
Its assoicated cold front will be dropping south into Northern Ohio/in
setting up a stretch of northwest flow for Southeast Michigan as heights build
ahead of an anticyclonic circulation encroaching from the upper
Mississippi Valley. Although conditions will be dry, a jet streak
intersection will lead to a period of gusty winds (20-25 mph range)
during the afternoon assuming the mixed layer profile remains
marginally supportive. One potential benefit of these windier
conditions will be that some of the driest air aloft in nearly a
week should Transfer down helping scour out what has been a nearly
continuous stratus deck. High temperatures will be more-or-less
unchanged on Friday, but skies will become partly to mostly sunny
during the afternoon/evening before better clearing overnight helps
promote radiational cooling with lows dropping into the mid 20s, and
perhaps the upper teens for the Tri-Cities region.
Saturday brings the arrival of additional height rises and even
drier low levels prior to sub-850 mb winds backing southwesterly.
This will usher in a major thermal shift with temperatures rising
about 10 degrees above normal as highs on Sunday and Monday will be
in the 40s once warm air advection ramps up throughout the column. Solid chances
exist for widespread rainfall along a sharp baroclinic zone as
higher thetae air pumps northward along the warm conveyor-belt
originating near the Gulf. An Arctic front then pushes through on
Tuesday ahead of a sub-500 mb 2 pvu anomaly trapping a polar airmass
across the Great Lakes through the latter half of next week. Low
temperatures in the teens Tuesday and Wednesday night certainly seem
reasonable, even this far out.
Fresh northwest wind with gusts to near-gales through early this
morning will steadily diminish as high pressure builds into the area
from the south. Waves along the exposed nearshore waters of
The Thumb will follow suit, falling below Small Craft Advisory
criteria by late morning. Conditions will remain seasonably
unsettled with episodes of elevated southwesterly and northwesterly
flow associated with regular passage of weak cold fronts. No
significant events for the next week.
Michigan...Lakeshore flood advisory until 10 am EST this morning for miz049.
Lake Huron...Small Craft Advisory until 10 am EST this morning for lhz421-441-
Lake St Clair...none.
Michigan waters of Lake Erie...none.