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Area forecast discussion 
National Weather Service Grand Rapids Michigan 
1142 PM EDT Monday Oct 6 2008 


Latest update...aviation... 


Synopsis...(323 PM EDT Monday Oct 6 2008) 
fair weather will prevail through Tuesday afternoon as high pressure 
slowly moves off to the east. Low pressure will bring showers late 
Tuesday night and Wednesday. 


&& 


Short term...(323 PM EDT Monday Oct 6 2008) 
(tonight through Wednesday night) 
rain showers tenaciously hung around this afternoon but radar trends 
show they are ending for all but the far north...where one last 
batch remains. Expect dry weather overnight as frontal boundary 
washes out and convergence/overrunning weakens. 


Fair weather also expected into tomorrow evening as front approaches 
from the west. Latest model guidance shows rain not arriving until 
after 06z Wednesday...so dropped probability of precipitation for the western forecast area for 
Tuesday evening. The front moves through between 06z and 18z Wednesday 
with only light quantitative precipitation forecast expected as best moisture and lift remains both 
north and south of lower Michigan. There is some elevated 
instability in model soundings on Wednesday morning but it is 
marginal enough to leave thunder out of the forecast for now. 


Clouds and showers should linger through the day on Wednesday which 
should hold maximum temperatures down a bit. Went with latest mav guidance 
which was a bit lower than previous forecast. Very slow improvement 
Wednesday night. Kept low chance probability of precipitation going for now...although it 
appears that deep moisture departs by 00z Thursday. 


&& 


Long term...(323 PM EDT Monday Oct 6 2008) 
(thursday through monday) 
the medium range models still Haven/T come into agreement on what 
will happen next weekend. The European model (ecmwf) remains consistent with it/S own 
solution from the past few runs and shows a cutoff low developing 
over Nevada/California which is similar to the glbl Gem solution (the GFS is 
farther northeast over Utah and not as deep). The difference is that 
the European model (ecmwf) builds a stronger ridge over the eastern US than the Gem and 
GFS. Interestingly though...the GFS is trending a bit slower and 
farther west with these features compared to the past few days. On 
the surface all of the models agree that the high over the eastern Great 
Lakes will drift southeast to the middle Atlantic by Thursday. That 
will allow a cold front to slip south of the County Warning Area by Thursday 
morning. South flow then develops in response to the building ridge 
and the deepening West Coast trough. Differences appear after 
Thursday. The European model (ecmwf)/GFS/glbl Gem/gefs ensembles develop a surface low in 
the Southern Plains. The European model (ecmwf) is the farthest northwest with this. Given 
the digging nature of the West Coast low...this solution makes the 
most sense to ME. So even though the GFS/glbl Gem/gefs ensembles 
move that low northeast toward lower Michigan by Saturday and move 
the front through Sunday (although they have been trending 
slower)...I/M leaning toward the European model (ecmwf) solution. That suggests that 
warmer weather will prevail through next weekend as the upper ridge 
builds. The cold frontal passage should hold off until Monday. We/ll have chance 
probability of precipitation in the grids beginning Sunday for rain showers/thunderstorms and rain ahead of and along 
the front and continuing through Monday. 


&& 


Marine...(323 PM EDT Monday Oct 6 2008) 
stronger wind speeds of at least 10 to 15 kts will continue tonight 
as the east to southeasterly surface pressure gradient tightens up. This 
will result in increasing wave heights to around 2 to 4 feet. Wave 
heights higher than that should not impact our nearshore waters 
due to the easterly wind orientation. 


&& 


Aviation...(1142 PM EDT Monday Oct 6 2008) 
upstream surface trough will gradually approach the next 24 hours. A 
thickening and lowering cloud deck can be expected. Conditions will 
be VFR for the remainder of tonight...with high cirrus level clouds 
in place. On Monday...the cirrus will lower gradually into an 
altocumulus deck...dropping from 20000ft to 8000ft. Between 03z-06z 
tomorrow evening it is possible some rain showers will be spreading 
in with slightly lower ceilings in the 3500-5000ft range. 
Decided...given the dry air in place...not to introduce 
precipitation and lower clouds just yet. So...a VFR forecast...with 
easterly winds throughout. 


&& 


Hydrology...(323 PM EDT Monday Oct 6 2008) 
no Hydro issues expected this week. 


&& 


GRR watches/warnings/advisories... 
Michigan...none. 
Lm...none. 


&& 


$$ 


Synopsis: ostuno 
short term: ostuno 
long term: 93 
marine: ostuno 
aviation: Duke 
hydrology: ostuno