420 
fxus63 kmpx 211722 
afdmpx 


Area forecast discussion 
National Weather Service Twin Cities/Chanhassen Minnesota 
1122 am CST Sat Nov 21 2009 


Discussion... 


Seeing foggy morning across eastern County Warning Area thanks to residual moisture 
and proximity surface high just south of the Great Lakes. Once the fog 
Burns off this morning...will see yet another balmy middle to late 
November day. Expect full sunshine...and srly winds will help 
usher in much above normal temperatures yet again. Mixing down tool to h9 
on NAM/GFS suggests highs in 50s across entire County Warning Area today. Mav 
seemed to have best Handel on highs for today based on mix down 
tool...so went close to it for highs. With low level flow expected 
to be just east of south...would not be surprised to see downslope 
favored regions north of the Buffalo Ridge make a run at 60. Winds 
will also become breezy out west this afternoon as gradient 
tightens and some 30 knots winds get down to about 925 mb...BUFKIT mix 
down tool would suggest gusts in the middle 20 kts out there this 
afternoon. 


Still looks good for stratus to return tonight as low level jet 
slides over Minnesota and strong warm air advection with isentropic upglide 
ensues...expect most of area to be overcast by 12z Sunday. This will 
lead to a rather mild evening Saturday night. For rain chances 
Saturday night/Sunday...deep moisture continues to be lacking... 
suggesting another light rain/drizzle type event. Based on 290k 
surface from NAM/GFS...not really seeing good adiabatic Omega until 
late morning across mainly wis...so continued trend in forecast of 
favoring eastern County Warning Area for rain. 


For Sunday into next week...models continue to struggle with 
progression of systems...but with European model (ecmwf)/NAM/Gem all similar in their 
handling of things sun through Tuesday...stayed close to a blend of those 
solutions for this part of forecast. GFS/sref are fast/north 
outliers with this system...but dprog/dt for GFS does show it 
trending toward slower/more southern European model (ecmwf) solution with time. So with that 
in mind...expect cold front to enter County Warning Area Sunday...but will 
stall/wash out as main upper forcing heads to Hudson Bay and it 
encounters strong dry high pressure in control from the Great Lakes 
east. As this occurs...strong 500 mb trough will begin digging/cutting 
off across northern plains Monday...quickly turning cold front into a 
warm front Sunday night. With the front prognosticated to be over central 
Minnesota...have highest probability of precipitation Sunday night there. By 00z Tuesday...both 
European model (ecmwf)/Gem already starting to form a close 500 mb low...with NAM doing 
so by 12z Tuesday. As this occurs cyclogenesis starts in the 
NE/KS/MO/IA area Monday night...with whats left of front becoming 
more of an inverted trough across western Minnesota. This will favor precipitation 
chances to the western half of County Warning Area Monday/Tuesday as 500 mb low slows while in 
process of cutting off. Other big change continued by the European model (ecmwf) in 
its 21.00 run was for this to be a much warmer system as well...so 
raised temperatures considerably for the first half of next 
week...with 50s likely hanging around till Monday...with highs and 
lows Tuesday/Wednesday about 5 to 10 degrees warmer than previous forecast. 
This of course has large implications on p-type as now expecting 
this to be a primarily rain event...with mixed precipitation holding off 
until Tuesday night as the low pulls from Iowa to eastern WI...finally 
pulling some cooler air into the region. Rest of forecast from 
Thanksgiving on still looks good...as surface ridge should lead to a 
dry/cool Turkey day. 


&& 


Aviation.../18z taf issuance/ 


Latest observation south of mpx County Warning Area has numerous ceilings/visibility in the LIFR 
area with MVFR ceilings/visibility in Kansas/NE moving N/NE. This will be 
the source region for later this evening/overnight across most of 
mpx County Warning Area with LIFR or IFR ceilings/visibility a good bet for most of taf 
sites. Early term remains problematic with eau as MVFR ceilings 
moving northward across eastern Iowa...which may keep eau MVFR this 
afternoon...with decreasing visibility/ceilings overnight. Latest GFS/NAM has 
strong isentropic lift this evening below 90h which means lower 
ceilings/visibility developing. Drizzle also a good bet as lower 
ceilings and subtle lift in the boundary layer should help to 
generate some light precipitation. These LIFR/IFR ceilings/visibility 
will likely continue through 15z...then slowly rise...especially for 
axn as the frontal boundary and subsidence should begin to erode 
lower ceilings. Ceilings/visibility could be lower than expected as per 
earlier observation in Kansas source region. However...will keep conditions 
just above minimums with confidence level not extreme for this 
type of scenario. ..jlt.. 


Cwsu discussion... 


Just thin high clouds currently over msp. Do not expect lower clouds 
until this evening. Parts of Iowa still fighting dense fog and low 
clouds... expect that moisture to advect into msp vicinity this 
evening. At least IFR ceilings expected... possible LIFR ceilings and fog 
toward morning. Some improvement during the day Sunday... afternoon 
ceilings should rebound to the 015-020 range. 


South winds increasing...a gust or two of 20 kts possible this 
afternoon. More southeast this evening, and not quite as breezy 
Sunday...around 10 kts. - Kfm 


&& 


Mpx watches/warnings/advisories... 
Minnesota...none. 
WI...none. 
&& 


$$ 


Mpg/jlt