260 
fxus63 kdtx 101055 
afddtx 


Area forecast discussion 
National Weather Service Detroit/Pontiac Michigan 
555 am EST Wednesday Mar 10 2010 




Aviation... 


Low level moisture will continue to gradually increase across the 
area as low pressure lifts north into the upper Midwest. Will back 
off on the time of MVFR...and eventually IFR...ceilings until later in 
the afternoon on through the evening. Once the moisture moves into 
the area though...expect IFR/LIFR visibilities/ceilings late tonight and on 
into Thursday. While there will be passing showers throughout the 
forecast period...coverage will be minimal and will not include in 
the forecast past the tempo group for the ongoing activity which 
will end early in the forecast. 


&& 


Previous discussion...issued 415 am EST Wednesday Mar 10 2010 


Short term...today 


Scattered light showers will continue throughout the day as a low 
pressure system lifts north through the upper Mississippi Valley and 
maintains a steady push of relatively mild and moist air into the 
central Great Lakes. With the center of the system so far west...do 
not expect significant rainfall...and not even a steady rain today 
as hit/miss showers traverse the region. 


Despite cloudy conditions...temperatures will still reach into the 
lower to middle 50s in most locations. The exceptions will be along the 
shorelines of the Great Lakes where east/southeast low level winds 
will maintain 40s as flow comes off of very chilly water and/or ice. 


Long term...tonight through next Tuesday 


The long term features cloudy and damp conditions with the main 
challenge being trying to time periods of rain and determining 
what effect these episodes will have on temperatures. A longwave 
trough extends across the western and central United States with 
three distinct upper level circulations embedded within. By Friday 
these will consolidate into one expansive low pressure system that 
will slowly migrate across the eastern United States through the 
weekend. Vorticity lobes and spokes of moisture extending from the low 
pressure system will bring bands of rain to Southeast Michigan. 


The vorticity maxima over Nebraska will pivot northwards towards 
the Dakotas overnight with shortwave ridging building again over 
the eastern Great Lakes. This is accompanied by an influx of dry 
middle-level air. A break in the precipitation is expected tonight 
but low levels will remain moist with dewpoints hovering in the low 
40s. Any breaks in the clouds this evening will only provide any 
opportunity for fog to develop. Otherwise the stratus is expected 
to gradually lower beneath a strengthening inversion...also 
creating an opportunity for fog. 


The next round of rain is still scheduled to arrive late Thursday 
afternoon from the south. This area of rain is accompanied by 
elevated instability as an occluded front lifts north towards 
Michigan. Have added a mention of isolated thunderstorms to the 
forecast for Thursday night with large scale ascent increasing with 
the approach of a middle-level dry-slot and falling temperatures at 
500mb. Showers are expected to be healthier on Thursday night than 
the ones expected today with precipitable water values climbing to around an inch 
and quantitative precipitation forecast of .25 to .50 inch. Mav guidance is advertising highs near 
60 on Friday which still seems to be on the high sided given the 
surface front will have already occluded as it lifts into far 
lower Michigan. Have trended temperatures up a couple more 
degrees...but remain on the cool side of guidance. 


The last of the three shortwaves gets absorbed into the larger 
trough on Thursday night with cyclogenesis occurring near the Gulf 
Coast. This surface low tracks to the Middle-Atlantic States by 
Saturday on the nose of a strong 160 knot upper jet...with 
easterly flow strengthening on the northern flank of the upper 
level low. The Atlantic Ocean provides a renewed supply of 
moisture to the central and eastern Great Lakes region and we 
look for rain to increase once again on Saturday. Low level 
northeasterly winds increase from Saturday night into 
Sunday as the system gradually starts to pull away...bringing the 
marine influence from Lake Huron further inland. This will finally 
cause temperatures to fall back closer to normal values with highs 
in the low 40s by the end of the weekend. 


Marine... 


A large low pressure system will lift north through the Central 
Plains and then remain in place over the plains and upper Midwest 
into Friday. A steady push of mild and moist air will feed into the 
region in advance of this low...and these general conditions will 
persist into the weekend as the low slowly progresses east across 
the southern Great Lake and Ohio Valley. In general terms...expect a 
prolonged period of unsettled weather with areas of rain lifting 
through the area from time to time. 


East winds will begin to increase today...and potentially become 
gusty over the weekend as the aforementioned low tracks to our 
south. Given the fact that relatively mild air will be flowing over 
Cold Lake waters...there will be a significant stable layer above 
the water...which will prevent gale force winds from mixing down 
to the surface. Small craft advisories may however be needed over 
the weekend for the nearshore...especially across Southern Lake 
Huron. 


&& 


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


&& 


$$ 


Aviation.....Dg 
short term...dg 
long term....kec 
marine.......dg 




You can obtain your latest National Weather Service forecasts online 
at www.Weather.Gov/Detroit (all lower case).