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Area forecast discussion 
National Weather Service Grand Rapids Michigan 
100 PM EDT sun Mar 21 2010 


Latest update...aviation... 


Synopsis...(408 am EDT sun Mar 21 2010) 
some light precipitation will remain possible this morning across 
the southern portion of the area, this precipitation is expected to 
diminish by afternoon...and skies will clear out some from north to 
south. 


A strong system well south of lower Michigan today will lift 
northeast through the day on Tuesday. Some light rain could clip the 
Jackson area Monday afternoon and Monday night. Drier and mild 
weather can then be expected through most of the remainder of the 
week. 


&& 


Short term...(408 am EDT sun Mar 21 2010) 
(today through tuesday) 
the two main challenges of this forecast package include the initial 
threat of precipitation this morning...and the chance of precipitation Monday and Monday night 
as the system taking shape to our south lifts to the NE. 


Persistent band of middle level fgen that has been over the County warning forecast area since 
yesterday morning is in the process of diminishing over the area. 
This is occurring as short wave ridging is building just to our SW 
with the closed low taking shape across NE Texas. A somewhat confluent 
flow is in place. In addition...low level NE flow is advecting in 
drier air. One more batch of spotty precipitation is now across Southern Lake 
Michigan and will try to overspread the southern portion of the area. 


Temperature profiles this morning over the southern couple of rows of the County warning forecast area 
support anything including some sleet...fzra...and plain rain with 
temperatures slightly above freezing 925 mb-850 mb and at the surface. A cold 
wedge is found from 925 mb to near the surface. The entire temperature profile 
below 5k feet will warm above freezing this morning...ending the 
mixed precipitation types. 


Clouds are expected to diminish through the day today from north to 
south. We will see a break in the precipitation then from this afternoon into 
the first portion of the day on Monday as the ridge ahead of the closed 
low will hold in control during that period. 


The closed low is expected to move from its current position across 
NE Texas...to over Virginia by 12z Tuesday. The northern periphery of this 
system does have the potential to clip the area Monday afternoon and 
Monday night. The eastern portion of the County warning forecast area will see an increase in middle 
and high level cloud cover on Monday morning. Models indicate that some 
low level moisture will wrap in across the area...finally bringing 
the low chance of precipitation to the jxn area. Any precipitation will be in the form of 
rain with plenty of above freezing air in the lower levels. 


The system will then pull away from the area early on Tuesday. Some 
residual low level moisture may remain and hold clouds in across the 
southeast portion of the County warning forecast area Tuesday morning. We do expect most areas to go 
mostly sunny/partly cloudy by Tuesday evening. 


&& 


Long term...(408 am EDT sun Mar 21 2010) 
(tuesday night through saturday) 
a northwest flow will persist aloft across the Great Lakes region 
through the extended period which will keep temperatures not far 
off from normals. 


No major systems are forecast to affect the area with mainly dry 
conditions it appears. The forecast did have some small probability of precipitation...20 
percent...but removed them as moisture looks limited through the period. 
A couple of frontal boundaries move through lower Michigan during 
the extended period...one Tuesday night and another Thursday. 
Moisture depth with both look too meager to mention precipitation at 
this point. 


&& 


Aviation...(100 PM EDT sun Mar 21 2010) 
VFR conditions are expected through the next 24 hours. Skies were 
clear north of a mkg to mop line as of 17z. This clearing will 
slowly progress south...making it to the I-96 taf sites by middle 
afternoon. However it probably won't make it to the I-94 taf sites 
until around midnight local time. 


&& 


Marine...(1159 am EDT sun Mar 21 2010) 
winds will remain offshore over the next couple of days. This will 
limit the overall wave height. Sustained values will remain below 
Small Craft Advisory criteria. 


&& 


Hydrology...(408 am EDT sun Mar 21 2010) 
four river points remain in an advisory...all of which are within a 
foot of bankfull stage. The river levels will continue to fall 
through the next few days as we enter a period of more dry 
weather. 


&& 


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


&& 
$$ 


Synopsis: njj 
short term: njj 
long term: Duke 
aviation: jk 
marine: mjs 
hydrology: njj