462 
fxus63 kmpx 211203 
afdmpx 


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


Update... 


Added 12z taf discussion below. 


&& 


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.../12z taf issuance/ 


Widespread vlifr ceiling and visibilities conditions are in place over 
western WI this morning...which formed in the high pressure ridge under 
the middle and upper level dry air. MVFR to occasional IFR visibilities were 
common over the Minnesota taf sites. Expect the increasing southerly flow 
to cause rapid improvement in visibilities over the Minnesota taf sites by 
16z...but lighter winds and status will hold visibilities down at least 
into MVFR until 18z. Otherwise expect VFR conditions and just scattered 
high clouds for the afternoon into the evening. An increasing 
moist flow ahead of the approaching front and trough will cause 
an expansion of MVFR ceilings from the Central Plains into our area 
overnight. Some lift will also cause areas of drizzle. There will 
also be an increasing risk of IFR ceilings and visibilities into at least 
the MVFR category at the end of the period..especially east. 


&& 


Mpx watches/warnings/advisories... 
Minnesota...dense fog advisory until 10 am CST this morning for Goodhue. 


WI...dense fog advisory until 10 am CST this morning for Barron- 
Chippewa-Dunn-Eau Claire-Pepin-Pierce-Polk-Rusk-St. Croix. 


&& 


$$ 


Mpg/jpr