Scientific Forecaster Discussion
fxus63 kdtx 251930
Area forecast discussion
National Weather Service Detroit/Pontiac Michigan
330 PM EDT Tue Jul 25 2017
Very dry airmass in place, as 12z DTX sounding checked in with a precipitable water
value of 0.49 inches, with dew pt depressions of 43 c at 700 mb and
14 c at 850 mb. Subsequently, cu development has been limited to non
existent this afternoon.
Upper level ridge axis will be in place tonight, providing clear
skies and temps likely falling back into the mid 50s to lower 60s.
Warmer tomorrow, as return southwest flow kicks supporting
temperatures climbing into the mid 80s (possible upper 80s) with
near full insolation. With 850 mb temps progged to climb toward 20 c
ahead of the cold front, 90 degrees would be in play, but mixing
depths expected to come up short of 850 mb with the cooler start.
Upper level energy/trough over southern Alberta will be deepening as
it slides into the western Great Lakes on Thursday, leading to
cyclogensis over the eastern Ohio Valley and into to the mid
Atlantic on Friday. Narrow 850 mb Theta-East Ridge axis to enter County Warning Area by
Thursday morning, and slide south of the state during the day.
Deeper moisture (pw's of 2+ inches) to remain across Ohio Valley.
Mid level lapse rates in place over Southeast Michigan on Thursday
look weak, with convective available potential energy also mainly below 1000 j/kg, thus not a whole
lot of severe weather concerns as surface front should be south of
the state by late afternoon as well.
A broad expanse of surface high pressure will build from central
Canada into the Great Lakes Friday and then last right through the
weekend. This will bring dry weather and a fresh supply of cooler
air with lower humidity, especially Friday when high temperatures
are projected to drop back into the 70s with lows in the 50s Friday
night. A gradual modification of the air mass will progress each day
after leading to highs around 80 Saturday and in the lower 80s
Sunday. Global model solutions are in loose agreement on the timing
of the next front, later Monday into Tuesday. At this point, the
front appears weak and moisture starved with a range of solutions on
the upper air pattern by that time frame. High pressure still
anchored over much of the country east of the Mississippi favors a
conservative approach to rain potential if the front can even make
it into the southern Great Lakes by then.
High pressure centered over Lake Huron this afternoon will drift
east reaching the New England states by Wednesday morning. Light
southeasterly winds will veer to the southwest Wednesday on the
backside of the high and ahead of an approaching cold front. Gusts
could reach 20 knots ahead of the front but fetch will keep higher
wave over the open waters. This front will bring the chance of
showers and thunderstorms to Lake Huron as early as Wednesday
afternoon. The front will sag south spreading precipitation chances
south through the rest of the eastern lakes overnight into Thursday.
North to northeast winds will increase to near 20 knots Thursday
night in the wake of this front. Waves will build in response to
this flow, and a Small Craft Advisory may be needed late Thursday
night into Friday for portions of the nearshore waters.
A cold front will progress southward through the area Thursday
morning, bringing a chance of showers and thunderstorms. There is an
opportunity for locally heavy rainfall with amounts exceeding a
quarter of an inch. At this time a low pressure system along the
front looks like it will track south of the area, but if it comes
back north, we could see even higher rainfall totals closer to a
issued at 117 PM EDT Tue Jul 25 2017
High pressure centered over mid Michigan has resulted in a few dry airmass
with light winds. Some cirrus debris from upstream convection has
spread into the area with only a few diurnally driven cu popping up.
Though winds will be light (generally less than 10 knots), they will
be veering from easterly this afternoon, to southeasterly tonight,
finally emerging southwesterly Wednesday morning as the high drifts
//Dtw threshold probabilities...
Lake St Clair...none.
Michigan waters of Lake Erie...none.