403 
fxus63 kgrr 210014 
afdgrr 


Area forecast discussion 
National Weather Service Grand Rapids Michigan 
810 PM EDT Sat Mar 20 2010 


Latest update...aviation... 


Synopsis...(354 PM EDT Sat Mar 20 2010) 
a nearly stationary front will linger over Southern Lower Michigan 
resulting in some precipitation through Sunday morning. High 
pressure will strengthen over Ontario Monday into Tuesday pushing 
the frontal boundary south of the Michigan border. 


&& 


Short term...(354 PM EDT Sat Mar 20 2010) 
(tonight through Monday night) 


The main forecast issue deals with the precipitation potential 
tonight into Sunday am. 


The 12z run of the NAM showed the snow persisting over my central 
counties from near kbiv to klan into this evening. Then a lull for 
part of the night...followed by another round of mainly snow late 
tonight into Sunday am. Forecast soundings for kbtl and kazo show a 
potential for freezing rain from 12z to 15z. The GFS and local WRF are mainly 
dry tonight into sun am. 


Watching radar and satellite trends implies the NAM is right. The 
band of precipitation extends southwest through central Illinois. The 
cells within this band are moving northeast. So we will see the 
snow persisting into the late afternoon and evening hours. Another 
surge of precipitation in Missouri is also moving northeast. If 
this feature holds together it will arrive later tonight. So while 
there will be a lull in the precipitation tonight...I will feature 
likely probability of precipitation for mainly my southern and central counties. Then for 
Sun morning I will go with chance probability of precipitation for the southern half of my 
area...mixing in some freezing rain for the Interstate 94 corridor. My 
northern counties are expected to stay dry and clearing will allow 
for decent cooling. 


Still looks like the upper low will spread a band of precipitation 
up to near jxn on Monday. Will maintain dry weather then...but it 
will be a close call. 


&& 


Long term...(330 am EDT Sat Mar 20 2010) 
(tuesday through saturday) 
southern stream system will be exiting out of the picture by Tuesday 
as it heads across southern New England. This results in a rather 
quiet extended period. A ridge of high pressure will settle in 
behind it. Tuesday looks to be a pleasant day with sunshine and 
highs in the 50s. A cold front is expected to cross the region on 
Wednesday. Main affects from this system will be a return to more 
normal temperatures with highs mainly from 45 to 50 Wednesday through Sat. We could 
see a few light showers passing through on Wednesday...but these look 
minor due to the lack of moisture. 


The models differ late in the week as the GFS shows another cold 
front for Friday...while the European model (ecmwf) does not have this front. For 
now will carry a slight chance of a shower again on Friday. Saturday 
looks dry as the models have ridging building in. 




&& 


Aviation...(810 PM EDT Sat Mar 20 2010) 
a narrow band of IFR conditions with snow has been impacting the 
area today and this evening... although models suggest that enough 
drying should take place in the low levels for conditions to go 
predominately MVFR by 03z (with a lull in precipitation coverage). 


Conditions should stay predominately VFR at mkg tonight (and 
sunday)... as the dry low level air mass in more entrenched the 
farther north you go. 


Toward 09z-12z a potential resurgence in narrow precipitation bands suggested 
by the models could yield another 3-6 hour period of IFR conditions 
along the I-94 corridor... with even a slight risk of freezing rain 
12z-15z at azo and btl. This threat is too low at this time that it was not 
included in the tafs... but it is Worth mentioning here. 


With the exception of perhaps jxn... all sites are expected to go 
VFR toward/after 18z Sunday. 


&& 


Marine...(354 PM EDT Sat Mar 20 2010) 
will cancel the Small Craft Advisory early as the offshore component 
has increased and wind speed decreased. 


&& 


Hydrology...(354 PM EDT Sat Mar 20 2010) 
water levels will continue to recede into Monday as no significant 
precipitation is forecasted. 


&& 


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


&& 
$$ 


Synopsis: mjs 
short term: mjs 
long term: jk 
aviation: Meade 
marine: mjs 
hydrology: mjs