Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Detroit/Pontiac Michigan
600 PM EST Friday Feb 5 2016
Several hour period of shsns will affect terminals during the first
few hours of the forecast as a surface trough passes through lower
Michigan. MVFR ceilings and/or visibilities will be possible with some of this
activity...but with the trough clearing the area in the 01z-03z time
frame...expect improving conditions much of the night into Saturday
with VFR ceilings common. SW flow will veer to west-northwest briefly in the wake
of this trough...but back to SW once again in advance of the next
fast approach trough.
For dtw...period of MVFR ceilings...and perhaps visibilities...as trough works
through terminal. After 02z-03z...ceilings will trend to VFR...and above
5kft overnight into Saturday. SW winds 10 knots or less will veer to
west overnight and then back to SW Saturday...increasing into the 10
to 12 knots range with a few higher gusts.
//Dtw threshold probabilities...
* high for ceilings at or below 5kft through the evening. Low overnight.
Previous discussion...issued 333 PM EST Friday Feb 5 2016
12z DTX sounding revealed an 850 mb temperature of -12 c...a touch colder
than model initializations. Solid low level (925-850 mb) Theta-E
ridge/(2+ g/kg of specific humidity)/convergence/ traversing through
lower Michigan today generating some Lake Michigan enhanced
scattered light snow shower/flurry activity (mainly north of I-
69)...despite being embedded underneath an upper level ridge out
ahead of the central North American trough.
Majority of the upper level energy/pv over the plains will drop into
Texas tonight...with deep cold low/pv anomaly rotating through
northern Ontario. Still...a modest 500 mb height fall center to
track through Southern Lower Michigan...but low levels will be
drying out with westerly flow...and expecting snow shower/flurry
activity to end with mainly just middle/high clouds as the upper level
shear axis tracks through Saturday morning.
The weekend will feature a modest warmup...as potent upper level
energy/jet off the coast of the Pacific northwest spills into the
northern plains and into the western Great Lakes...with 500 mb
closed low/circulation developing. Subsequent large scale
ascent/developing occlusion/narrow moisture plume (pw value around
half an inch) on Sunday supporting chance probability of precipitation...expanding to likely
probability of precipitation Sunday night...along with sufficient cooling expected to trend
precipitation to all snow with light accumulations.
Per 12z Euro...925 mb temperatures rising to -4 to -2 c on Saturday with
favorable southwest flow expected to translate to highs in the middle
30s to around 40 degrees (similar to today). Highs in the low to middle
40s are then expected on Sunday as 925 mb temperatures sneak above zero.
Sufficient clouds persisting during night hours expected to hold mins
in the 20s.
Changes coming about early in the new work week. A strong polar jet
diving through the Midwest will carve out a deep trough which will
hold through the end of the week. Temperatures on Monday will
make a run at 40f one last time before much colder air filters
into the region. High temperatures will fall into the 20s by
Wednesday...holding there through the remainder of the week. The
upper low will stall over the Great Lakes the first half of the
week keeping snow chances in the forecast through that stretch.
Weak shortwave ridging will maintain quiet weather for February
standards throughout much of the weekend. Modest southwesterly winds
will increase during the day Saturday in advance of a clipper low
pressure system. Wind gusts will approach 30 knots Saturday
afternoon over Central Lake Huron. Wind directions will eventually
back to the southeast Sunday before an expansive surface low settles
and stalls over the central Great Lakes.
Lake St Clair...none.
Michigan waters of Lake Erie...none.
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at www.Weather.Gov/Detroit (all lower case).