Weather

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fxus63 kdtx 131108 
afddtx 


Area forecast discussion 
National Weather Service Detroit/Pontiac Michigan 
708 am EDT Monday Oct 13 2008 




Aviation... 


VFR conditions are expected today as high and middle clouds move into 
the region from an approaching low across the northern plains. 
Clouds will increase tonight as the cold front associated with the 
low moves into western Michigan. Clouds could approach MVFR late 
tonight as precipitation chances increase to around 30 percent at mbs. 
However given this is the end of the taf cycle will leave the 
current tafs dry with VFR conditions. 


&& 


Previous discussion...issued 359 am EDT Monday Oct 13 2008 


Short term...today 


Another warm day is on tap as winds become southeast ahead of an 
approaching low pressure system. The main forecast issue becomes 
high temperatures as the met guidance suggests temperatures will reach the 
upper 80s across some locations. However 850 mb temperatures across 
the area will fall a good 4 degrees during the day today...with some 
middle and high level clouds moving into the region. With filtered 
sunshine and falling 850 mb temperatures will lean towards the cooler mav 
numbers today...with temperatures expected to get close to 
yesterdays highs. 


Long term...tonight through Sunday 


Main story for the extended period will be the return of Fall-like 
weather to Southeast Michigan. 


Water vapor imagery shows the western low has begun to split...with 
one main area of energy now lifting up through the northern plains 
and the second weaker chunk of energy settling down into the 
southwest. Models remain in good agreement with lifting the first 
chunk of energy up into Ontario by tonight...effectively breaking 
down the upper ridge that has provided the unseasonably warm and 
sunny weather to Southeast Michigan the past several days. As this 
system passes to our north on Tuesday...it will send a cold front 
down across lower Michigan. GFS is now running faster than the other 
models with the southward progress of this feature and the 
associated surface trough...and will continue to follow the more 
consistent solutions of the NAM/Euro. Although frontal dynamics 
continue to look weak...low-level moisture pooling ahead of the 
front looks impressive...with expected precipitable water surge to nearly 1.5 inches 
and NAM cross-sections showing specific humidities between 8 and 12 
g/kg up through 6000 feet mean sea level. Will continue to carry high chance 
probability of precipitation for the whole area. Have removed thunderstorm chances however 
as NAM/GFS have both trended more stable...with model soundings even 
showing a fairly strong cap centered near 700mb. 


Pattern becomes a little complicated late Tuesday through Thursday 
as the cold front stalls either over southern Michigan or Northern 
Ohio (late tuesday)...in response to southerly flow increasing as 
the shortwave over the southwest lifts up into the Central Plains. 
Surface wave associated with the shortwave is expected to ride over 
the stalled baroclinic zone on Wednesday and Wednesday 
night...likely providing focus for more widespread 
precipitation...at the very least for the southern County Warning Area. In the 
meantime...another low pressure system will track across northern 
Canada. This will send another cold front down through lower 
Michigan late Wednesday night and Thursday. This next front will 
usher in much cooler and drier air...effectively pushing out 
precipitation (except for lake effect) and sending h850 temperatures 
plummeting below 0 degrees c by Thursday afternoon. 


Cool northerly flow and high pressure will briefly build in on 
Thursday before energy drops out of the northern plains and carves 
out a deep trough over the eastern u... models indicate will 
affect US into next weekend. Have made cuts to temperatures Thursday 
through Saturday with the expectation of a prolonged period of 
northerly flow as the jet stream dives well south of US. 
Temperatures will struggle to reach the upper 50s/60 on Thursday and 
only climb into the middle 50s by Friday and Saturday. Will hope to see 
some recovery by Sunday as GFS/Euro show southerly flow increasing 
ahead of the next system passing through Canada. 


Marine... 


High pressure will remain in control over Michigan today 
providing another day with unseasonably warm temperatures. Clouds 
and winds will start to increase however as a cold front approaches. 
Winds will increase noticeably late tonight over Northern Lake 
Huron...with northwesterly gusts between 25 and 30 knots developing 
behind the cold frontal passage in the early morning. The front will 
weaken as it slides southward across Southern Lake Huron...with 
associated gusts decreasing as well. Small craft advisories may be 
needed for the nearshore waters of Lake Huron as winds and waves 
increase from Monday night into Tuesday...however conditions do look 
marginal. 


The weather will remain relatively active though the end of the 
week...with several weak disturbances and cold fronts passing 
through. A strong cold front will push down from Canada Wednesday 
night...ushering in a period of prolonged northerly flow and strong 
cold air advection that will last into the weekend. Although the 
winds do not look particularly strong...the destabilizing effect of 
the cold air over the warmer waters and the long fetch over Lake 
Huron may allow waves to build higher than 4 feet across Southern 
Lake Huron. 


&& 


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


&& 


$$ 


Aviation.....Kurimski 
short term...kurimski 
long term....hlo 
marine.......hlo 




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