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fxus63 kgrr 131745 
afdgrr 


Area forecast discussion 
National Weather Service Grand Rapids Michigan 
1245 PM EST Sat Mar 13 2010 


Latest update...aviation... 


Synopsis...(347 am EST Sat Mar 13 2010) 
a large area of low pressure over the Ohio Valley will continue to 
bring cloudy skies and occasional rain to southwest lower Michigan 
today. The low will slowly drift to the east and the rain will 
become lighter and more scattered tonight and Sunday. The clouds 
should begin to break up from north to south Sunday night and 
sunshine is expected for Monday. Temperatures will remain mild with 
daytime highs reaching the 50 to 55 degree range. Overnight lows 
should fall into the 30s. 


&& 


Short term...(347 am EST Sat Mar 13 2010) 
(today through monday) 
another impulse of rain was over eastern lower Michigan early this 
morning rotating westward around the Ohio Valley upper low. This 
area of rain will affect much of the County Warning Area...especially this morning. 
The rain should lighten up a bit during the afternoon...but high 
probability of precipitation will still be warranted. The main thrust of the precipitation should be 
through by this evening...therefore will carry mainly chance probability of precipitation 
tonight and Sunday as a few showers linger. See Hydro section for 
details on possible impacts from this rainfall to our swollen river 
levels. 


Determining when the rain ends is a bit problematic. Despite the 
eastward progression of the upper low...deeper moisture lingers over 
the area all the way into Sunday evening. Decided to add low chance 
probability of precipitation to the southeast County Warning Area for Sunday evening. Into the overnight drier air 
finally arrives from the north and skies should slowly clear from 
north to south. 


Upper ridging will gradually replace the departing low into early 
next week. This should give US a sunny Monday with temperatures in the low 
to middle 50s. 


&& 


Long term...(347 am EST Sat Mar 13 2010) 
(monday night through friday) 
models continue to show a ridge of high pressure building into the 
area Monday night through Wednesday. This feature moves east on 
Friday with a southerly flow of warm and moist air setting up for 
the end of the week. Given the subsidence associated with the 
ridge...a relatively dry period is expected. 


An impressive surge of Arctic air will be dropping southward through 
Nunavut and Hudson Bay on Friday and will encounter the warm moist 
air lifting up the MS valley. This should lead to a rather strong 
storm for the weekend. 


&& 


Aviation...(1245 PM EST Sat Mar 13 2010) 
biggest challenge for this set of terminals is determining ceiling and 
visibility trends with the persistent system southeast of the area that 
will continue impacting the region. Conditions at most locations 
have improved to MVFR with visibilities actually mainly VFR. Some isolated 
locations like kgrr and kjxn have kept an IFR ceiling...but we expect 
them to come up with the diurnal mixing. Band of rain showers moving 
through the next couple of hours will limit visibilities at times to MVFR. 
Some wind gusts will remain possible through 00-01z. 


Most uncertain time frame will come after sunset tonight and into 
the morning hours. Visibilities are expected to remain VFR tonight with the 
NE winds remaining up a bit through the night. Ceilings are the 
uncertain parameter as they could tend to lower slightly and sneak 
into the IFR category. We believe with a bit of wind remaining 
up...and conditions upstream across Ontario and New York state MVFR 
or above...that we will remain MVFR. This is something to monitor. 
Conditions will then trend better a bit on sun as the system begins 
to move away. A few wind gusts around 20 knots will be possible 
after 15-16z. 


&& 


Marine...(347 am EST Sat Mar 13 2010) 
will hoist a Small Craft Advisory as east northeast winds are 
expected to reach around 25 knots by this afternoon. Due to the 
offshore nature of the winds...waves should remain at three feet or 
less. The winds should begin to diminish toward daybreak on Sunday. 


&& 


Hydrology...(347 am EST Sat Mar 13 2010) 
have allowed the areal Flood Advisory to continue to allow the day 
shift to evaluate the situation. This continues along with many 
river flood advisories. However...overall the flooding will mainly 
impact areas immediately near rivers and streams or lowlands. 


The rain that is expected today into early Sunday should be light 
for the most part. Areas north and west of Grand Rapids should only 
see around a tenth of an inch of rainfall. Areas from roughly Van 
Buren County NE to Gratiot County should see around a quarter inch 
of rain...while the far southeast County Warning Area should receive between a quarter and 
half inch of rain. Since this rain will span a 24-30 hour period 
worsening Hydro conditions are not expected. However this rain will 
prolong the duration of bankfull rivers and nuisance type flooding 
into the middle of next week. 


&& 


GRR watches/warnings/advisories... 
Michigan....none. 
Lm....Small Craft Advisory St. Joseph to Manistee 16z today through 
09z tonight. 


&& 


$$ 


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