953 
fxus63 kdtx 191740 
afddtx 


Area forecast discussion 
National Weather Service Detroit/Pontiac Michigan 
140 PM EDT Friday Mar 19 2010 




Aviation... 


Southwest winds will gust between 20 and 25 knots through 00z ahead 
of a cold front. The front will drop through Southeast Michigan taf 
sites between 00z and 04z...bringing a northerly shift in winds 
and allowing an overcast deck around 6000 feet to spill into the 
region. Ceilings will drop further overnight...becoming MVFR 
around daybreak as additional moisture arrives and begins to ride 
northeast along the front. Scattered light showers are expected to 
develop late tonight...however coverage will be limited enough to 
withhold mention in the tafs. The best chance for precipitation will be 
after 14z Saturday. Colder air pushing down from the north will 
bring mixed precipitation starting tonight...changing to all snow 
from fnt northward Saturday afternoon. A changeover to all snow is 
expected to hold off until Saturday evening from ptk south. 


&& 


Previous discussion...issued 324 am EDT Friday Mar 19 2010 


Short term...today 


Southeast Michigan is in for another round of warm weather as 
southwest flow continues to bring warm 850 mb temperatures of +4 to 
+6 celsius with highs again forecast to be 10 to 15 degrees above 
normal. With steep low level lapse rates of 8 to 10 c/km in the 
lowest 825 mb winds will again be gusty across the area in this deep 
mixing layer with winds of 25 to 30 knots in the boundary layer. 
Although clouds will increase across the area today as the cold 
front approaches...especially across the northern County Warning Area...the weather 
will remain dry across the County Warning Area as the front reaches northern 
Michigan by the late afternoon hours. 


Long term... 


A noticeable cool down for the weekend...but bouncing back early 
next week. 


Elongated upper wave tracking through Ontario at the present time. 
Secondary trough/upper wave following in behind will really give the 
cold front a push south through Southern Lower Michigan late 
tonight/Saturday...as surface/925/850 mb frontal zones seen sliding 
south of the state....but middle level fgen lingers. 00z NAM/GFS 
thermal profiles support snow (except across the far south)...but 
quantitative precipitation forecast will be light (tenth of an inch or less)...as the County Warning Area struggles 
to get into the right entrance forcing. So...with marginal surface 
temperatures and fairly light snowfall rates...any accumulations 
will be a struggle with impacts on the roads minimal during the 
daytime hours. 


Good model consensus with the southern wave cutting off over the 
western Gulf Coast states...with Southeast Michigan on the downwind 
confluent side of the upper level ridge on Sunday...and it looks 
like we could end up being dry (which the 12z European latched onto 
and the 00z run continues). The airmass also modifies during the 
day...as we are caught in between a cold front sliding into the 
northern Great Lakes and the western Gulf Coast system. Thus...if 
the southern wave is booted off/pulled to the northeast Sunday 
night...precipitation should be in the form of rain...as 850 mb 
temperatures rise between 1-4 c and surface temperatures will have to come down 
from the highs in the middle 40s. 


Monday's highs will be dependent on how far east the storm system 
will be and whether Southeast Michigan will be impacted by the 
deformation zone...which remains possible...per 00z Canadian. 
With the poor handling/track record with this storm system by 
the models...will play The Middle Ground and call for middle 40s for 
highs with a low chance of rain (per inherited forecast). 


Ridging ahead of the next shortwave trough should support a 
good rebound in temperatures on Tuesday with sunshine...and will up 
maxes to around 50 degrees....which may be very conservative (10 
degrees) if the European ends up being right...as 850 mb temperatures seen 
climbing to 6 c. 


Marine... 


Gusty winds up to 20 knots will develop once again today as a weak 
cold front drops through the western and central Great Lakes. Winds 
will shift to the north over Lake Huron late today...then over Lake 
St Clair and Western Lake Erie tonight as the front pushes through 
then stalls south of the Michigan state line. Low pressure lifting 
up this boundary over the weekend will bring unsettled conditions 
and draw colder air down into the region from Canada. This will 
bring a chance for rain and snow...and strengthen winds on Sunday 
night and Monday. The potential exists for gusts to reach small 
craft conditions along the nearshore waters and up to 30 knots over 
the Lake Huron open waters. 


&& 


DTX watches/warnings/advisories... 
Michigan...none. 
Lake Huron...none. 
Lake St Clair...none. 
Michigan waters of Lake Erie...none. 


&& 


$$ 


Aviation.....Hlo 
short term...kurimski 
long term....sf 
marine.......kurimski 




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