Forecast discussion - Today and Tonight

High pressure draped across the southeast united states coupled with low amplitude northwest flow
aloft will facilitate persistence of dry conditions through the forecast period and a continuation
of southwest gradient flow. Ongoing light warm advection will warm 925mb temperatures by 10 or more
degrees over the next 24 hours, ensuring high temperatures in the mid 20s, or about 5 to 10 degrees
warmer than yesterday. More potent energy located well upstream will encroach on the Great Lakes
overnight. Strengthening southwest gradient will force a gradual rise in temperatures overnight. No
arguments from 00z guidance that indicate temperatures bottoming out around 20 early before rising
back into the mid 20s by sunrise Saturday. Nothing more than episodic mid/high clouds expected
through the daylight hours before better low-level moisture lowers the cloud deck after sunset.

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Remaining Forecast opinion -

Lower amplitude mid level northwest will define conditions locally through the upcoming weekend.
Weak shortwave energy originating from the Gulf of Alaska will shear into this flow over the next 48
hours, translating across Southeast Michigan on Saturday. Corridor of warm air advection will emerge
immediately in advance of the height falls, prompting a solid upward adjustment in temperatures
relative to today. Extensive cloud cover will dampen the response to some degree, but a modestly
mixed environment through 925 mb /-2 to -3C/ supports highs of mid-upper 30s. Brief shot of
isentropic ascent on the front end and a late day cold frontal passage warrants a low end PoP
mention throughout the day, but the limited moisture quality and lackluster forcing will seemingly
restrict precipitation chances. Ensuing weak cold air advection into Saturday night, the process
perhaps yielding a few flurries as moisture briefly deepens with the passing 850-925 mb frontal
slope. This frontal zone will temporarily settle just to the south by Sunday morning, providing a
window of opportunity for some clearing overnight. Going forecast leaning toward the colder end of
guidance for lows Sunday morning, latest model evidence providing little evidence to move away from
this position /upper teens to lower 20s/.

Frontal zone will wash back eastward and across Southeast Michigan on Sunday as the mass fields
reorient again with the approach of another weak shortwave. Clouds will likely remain problematic
accounting for both the fropa and a brief uptick in cyclonic vorticity advection with the shortwave
itself. Once again, moisture will be lacking to suggest anything more than a lower end probability
for a few snow showers to develop. A moderating thermal profile will again support highs of middle
30s.

The existing troughing will ease early next week, increasing depth to the low level west-southwest
flow establishing a firm period of warm air advection. The magnitude and duration of this warm up
still carries some uncertainty yet at this time scale, 00z GFS considerably more progressive with
the next inbound height fall center and stronger frontal passage /Wednesday/ relative to the ECMWF
and Canadian /following weekend/. Regardless, looking at a stretch of seasonable conditions through
at least the midweek period.

. . posted at 305 AM EST Friday March 6 2015


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