709 
fxus63 kmpx 100552 
afdmpx 


Area forecast discussion 
National Weather Service Twin Cities/Chanhassen Minnesota 
1152 PM CST Tuesday Mar 9 2010 


Aviation... /06z taf issuance/ 


Low pressure over northwest MO is expected to lift slowly northward into 
southern Minnesota on Wednesday and then dissipate over west central Minnesota 
as a new low approaches from the south on Thursday. Strong forcing 
forecast to move northward across the taf sites late tonight and 
Wednesday morning. This should translate into several bands of 
rain moving across the taf sites through 18z with rain diminishing 
to drizzle in the afternoon. The troubling part of the forecast is 
the current dry slot that worked into eastern Minnesota and western WI 
from northern Illinois this evening. We now have a hodgepodge of 
IFR/MVFR/VFR ceilings from the Twin Cities metropolitan on east through 
krnh and Keau. As the rain bands move northward overnight... 
believe ceilings will deteriorate to MVFR or IFR. Sites to the 
west should stay below 010 with visibilities at or below 2sm through the 
day Wednesday. A second concern will be Wednesday evening as the 
low pushes into west central Minnesota. This will bring in drier middle 
level air which may cause more dense fog with vlifr ceilings and 
visibilities as the low level air is being cooled from both the 
snow pack and the clearing above. 


Kmsp...MVFR ceiling should lower to below 010 by 09z as the first 
of several bands of rain move northward. Some improvement during 
the late morning to low MVFR as the forcing and precipitation 
bands move north. Confidence not high for the forecast Wednesday 
evening as vlifr conditions may develop as drier air works in 
aloft leaving a moist low layer. Mainly east winds from 8 to 10 
knots through Wednesday morning gradually turning southeast toward 
evening and diminishing near 6 knots. 


&& 


Discussion... /issued 336 PM CST Tuesday Mar 9 2010/ 


First wave of light rain pushing north around 20 kts across S Minnesota 
which will bring several hours of light rain across area as it lifts 
north remainder of the afternoon and early evening. Precipitation amounts 
should generally be in the .10 range. Concern behind this feature is 
for a period dense fog. Intro for this evening across SC Minnesota and 
then across the area for the overnight. Will issue an advisory for SC 
Minnesota for until 12z. 


Well developed vorticity in northwest MO has been developing next round of 
showers across no MO into S Iowa. Strong forcing lifting back north 
into SC Minnesota by 06z and across area overnight. Hope is that this next 
round of showers will prevent dense fog from becoming more 
persistent and widespread...but do expect widespread visibilities of 1/2sm 
or lower. Stronger moisture transport with this wave should lead to 
higher rainfall amounts...more in the .20 to .50 range. 


Upper low now in Kansas/NE will lift slowly north tonight and weaken on 
Wednesday as next trough plows across the SW states and into OK on 
Wednesday. Will be a break in the more significant precipitation as this 
feature pivots northwest and OK low then lifts north into Iowa and becomes 
our next player for more rains on Thursday/Thursday night. Some 
concern with good axis of middle level instability wrapping into area 
and 40 knot 850 mb jet that this shot of rains could be higher than 
The Rounds preceding it. 


Temperatures will remain mild with very little diurnal range the 
next several days with clouds and high dewpoints across area. Combo 
of mild temperatures...fog and precipitation should take a large whack out of the 
snowpack by Saturday. 


Temperatures and profiles next few days should remain warm enough to 
keep precipitation as liquid. 


Added mention of -ra for southeast areas into early Saturday with wrap 
around continuing as upper slowly slides east. 


&& 


Mpx watches/warnings/advisories... 
Minnesota...dense fog advisory until 6 am CST Wednesday for Blue Earth-Brown- 
Faribault-Freeborn-Martin-Nicollet-Redwood-Steele-Waseca- 
Watonwan. 


WI...none. 
&& 


$$ 


Rah/bap