322 
fxus63 kapx 120538 
afdapx 


Area forecast discussion 
National Weather Service Gaylord Michigan 
1236 am EST Friday Mar 12 2010 


Synopsis.../issued at 415 PM/ 


Low pressure over Iowa is expected to spread a band of rain across 
Michigan tonight. This system will bring additional rain chances 
through Saturday night...with above normal temperatures. 


&& 


Short term.../issued at 937 PM/...tonight 


Large swath of precipitation gradually swinging north through 
Michigan this evening in association with upper level vorticity center 
rotating north across the area. Best middle level divergence-q and upper 
divergence fields remain over western portions of the 
area...closer to parent upper dynamics. Precipitation may end up 
being the heaviest and most persistent in this area /west of tvc- 
cad line/...but all of northern lower should get at least some rain 
overnight as 850mb Theta-E ridge swings north across northern 
lower. Current forecast has this handled quite well and will make 
only modest adjustments for timing. More questionable over eastern 
upper...where forcing and deeper moisture are lacking through 12z. 
In this area...precipitation may not get in there tonight. 


Will also add areas of fog after midnight to all of northern 
lower...based on trajectories and upstream observation. Temperatures not 
falling much from their current readings...with many areas 
remaining in the 40s. 


Jk 
&& 


Long term.../issued at 415 PM/...Friday and beyond 


Continued above normal temperatures through the entire period with 
some much needed rainfall likely over the next couple of days. The 
main long term forecast concern revolves around the movement and 
timing of the plains system through this weekend. 


Friday...latest Wing of moisture continues to swing northeastward 
across northern half of the forecast area as the plains system 
continues to spin its wheels. Then the question becomes how much 
clearing and if so...whether or not any convective precipitation 
will develop. Models try to hold onto low level moisture...but we 
have been able to scour out the low stuff over the last couple of 
days so expect at least partial clearing in the afternoon. This 
should lead to decent instability development (mid level lapse rates 
between 6.5-7 c/km) so could see additional shower development. 
Increased temperatures across northwest downslope areas into the 
middle 50s (hope that is enough) with only middle 40s expected near 
the Lake Huron shoreline due to on-shore flow. 


Friday night into Saturday night...plains storm system finally looks 
like it will make a move to the east with deepening low pressure at 
the surface. This should lead to a large area of light rain 
progressing to the northeast. How far north remains the question 
with large and expansive high pressure remaining to the north across 
central Canada. Therefore will continue with chance probability of precipitation far north 
and bump probability of precipitation up to high likely for much of northern lower except 
categorical far south. Lows in the upper 30s and lower 40s and highs 
Saturday in the cooler but still above normal 40s. 


Sunday...any leftover light rain is expected to Peel out of the area 
in the morning with clearing in the afternoon. Mild with highs 
ranging from the middle 40s east to the middle 50s west. 


Monday through Thursday....high pressure ridging at the surface and 
aloft reestablishes itself across the region. This will lead to 
another stretch of dry and mild weather. Highs generally in the 
middle 40s to lower 50s and lows a bit chillier but still way above 
normal with in the middle 20s to lower 30s. 


Sullivan 


&& 


Marine.../issued at 440 PM/ 


Easterly winds will increase tonight as a low pressure system lifts 
northward through the upper Midwest. However...think lake stability 
will keep winds and waves under small craft conditions through the 
night. Winds/waves diminish somewhat on Friday and will remain 
below small craft heading into the weekend. 


Adam 


&& 


Aviation.../issued at 1238 am/...valid for 06z tafs 


Low level wind shear is at its peak at 06z and will diminish by daybreak as 
low-level wind fields weaken. 


Jh 


Low pressure over the upper Midwest will send a large area of rain 
and fog with IFR conditions through northern lower Michigan overnight 
into early Friday morning. The most persistent rain will be at 
ktvc...with much lighter precipitation expected at kapn and kpln. 
The precipitation will end Friday morning...with ceilings gradually 
improving to MVFR by midday or early afternoon. Another round of 
deeper moisture may begin to move toward the area Friday evening 
..resulting in lowering ceilings/visibilities once again. 


Jk 


&& 


Apx watches/warnings/advisories... 
Michigan...none. 
Lm...none. 
LH...none. 
Ls...none. 


&& 


$$