Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Detroit/Pontiac Michigan
1259 PM EDT Tuesday Jun 2 2015
Few-scattered diurnal cumulus around 5k feet this afternoon as high pressure
ridging continues to nose in from Canada. This will continue a
light easterly flow through the taf period.
//Dtw threshold probabilities...
Previous discussion...issued 336 am EDT Tuesday Jun 2 2015
Short term...today and tonight
Middle level ridging will expand into the southern Great Lakes/Northern Ohio
valley during the short term...north of a quasi stationary upper low
meandering across KY/TN. This will sustain surface ridging across
the eastern Great Lakes and lower Michigan. The surface ridge axis will remain
across Lake Huron and cntl/northern lower Michigan today...sustaining a light east-
NE wind through the period. This flow has picked up some moisture
off southern Ontario and has resulted in some periodic low clouds
streaming into the southern half of the forecast area. This moisture will
lead to some periodic cumulus with the onset of daytime heating. The
degree of dry air intrusion into the afternoon mixed layer should
keep any period of enhanced cumulus field to a minimum...thus offering a
good deal of sunshine today. After relatively chilly morning
readings...temperatures will warm nicely today under early June insolation.
Middle level subsidence and continued easterly flow will keep mixing
heights relatively low. Some modification of the airmass from
yesterday...adding a few degrees to the 925mb temperatures...will support
daytime highs around 70 /with cooler readings near the lakes/.
Lingering surface ridging will support good radiational cooling
conditions again tonight. Higher daytime temperatures and a little better
easterly gradient tonight will keep temperatures a little warmer compared
to this mornings readings /low 50s in urban Detroit and 40s
Embedded shortwave within quasizonal west-southwest flow aloft will force high
pressure over the Canadian Maritimes, which has extended into the
Great Lakes, off the East Coast late tonight. This will result in
high pressure gradually losing its grip from the top down as flow
becomes subtley cyclonic in the middle and upper levels. At the
surface, lake enhancement of the local pressure field will delay the
exit of high pressure and ensure another nice weather day for Wednesday.
Mixing to 850mb within a dry column will ensure full insolation
through at least midday with high temperatures reaching the middle 70s.
By afternoon, veering middle-level flow around the northern periphery
of the compact circulation over Tennessee will advect some elevated
moisture into into lower Michigan from the southeast which may
contribute to an increasing high based cumulus field by late afternoon. Lack
of depth to moisture eliminate any precipitation concerns for Wednesday.
Pattern more or less persists Wednesday night into Thursday as
heights remain rather stagnant over the Great Lakes and the
Tennessee upper low only slowly drifts east. This will contribute to
a gradual increase in column moisture into Thursday which will
subsequently aid a more robust diurnal cumulus field by afternoon.
Slightly improved 700 mb-500 mb lapse rates shown by the NCEP suite will
tilt the thermodynamic field just slightly in favor of an afternoon
shower or thunderstorm, most likely within a corridor of inland
troughing, but the potential at this time does not appear to be Worth a weather
mention in the grids.
High amplitude ridging across the northern tier will force high
pressure back into the Great Lakes Thursday night through Friday.
Potential for showers along the associated baroclinic zone will
depend on timing of lower amplitude disturbances. Modeled quantitative precipitation forecast
looking a little aggressive on Friday given poor environment and ill-
defined forcing. Blended grid 30 pop is fine.
Weak pressure gradient will support light winds across the waters
for the remainder of the week. Lone exception is Lake Erie where
enhanced easterly flow around the periphery of the high will support
slightly elevated winds and waves in the nearshore waters of Lake
Erie during the latter half of Wednesday but Small Craft Advisory
conditions are not anticipated.
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).