771 
fxus63 kmpx 192012 
afdmpx 


Area forecast discussion 
National Weather Service Twin Cities/Chanhassen Minnesota 
312 PM CDT Friday Mar 19 2010 


Discussion... 


Main forecast challenges in the coming week revolves around 
temperatures and what are dwindling hopes for precipitation next week. 


Currently...WV imagery shows shortwave in northwest flow approaching northwest 
Minnesota. This wave is embedded within a trough that stretches from the 
Ontario/Manitoba border SW into the 4 corners region. Currently 
seeing a strong system spinning up on the SW edge of this trough 
over the 4 corners which will be closing off tomorrow as it 
slowly trudges east across the Southern Plains and eventually into the 
middle Atlantic Tuesday. This looks to create an impressive March 
winter storm from central OK into northern Illinois...but we will remain 
north of any of this activity as surface ridging stays in control. 
Have not seen temperatures warm very much today in cloud cover...so will 
have low starting point for lows tonight. Current forecast still 
looked reasonable so only tweaked lows a couple of degrees 
down...especially in the northwest where temperatures have yet to leave the 20s. 
Cool down looks to be short lived...with coldest 850 mb temperatures expected 
Saturday morning. Surface ridge will be ovhd Saturday...so expecting 
neutral temperature advection with temperatures near normal under clear 
skies. By Saturday night...surface high slips south of the 
area...setting region up into return flow. Will have to deal with 
one more near normal night for lows Sunday night despite warm 
advection starting thanks to clear skies and cooler high temperatures 
from Saturday. 850 mb temperatures by Monday night will once again be around 
+8c...so have continued to increase highs for Monday with entire 
area now into the 50s. From Tuesday and beyond...temperature 
forecast gets a bit hairy thanks to another cold from that is 
prognosticated to drop across the region. 19.12 GFS/Gem bring this 
through Tuesday while the European model (ecmwf) holds off until Wednesday. If the 
European model (ecmwf) is correct...would see another day of temperatures around 10 degree 
above normal Tuesday...before temperatures make a run back to normal by 
the middle of next week behind the front. 


For precipitation...dry surface ridge pushing down into area currently is 
sufficiently preventing precipitation from getting up into the County Warning Area...all 
guidance in agreement with keeping any quantitative precipitation forecast south of the area...so 
have no chances for precipitation tonight. With upper ridge building back 
in for Sunday through Monday night...area will be dry...but another 
trough will be working across The Rockies in this time frame. 
Energy from this trough will approach the area Tuesday...but 
Gem/GFS/ECMWF seem to settling in on a split flow solution for 
this system...with a weak northern stream wave moving across the international 
border in the Tuesday/Tuesday night time frame...while the southern end 
of this trough slows down and across the central rockies...similar to 
current system. Like the current system...area gets stuck between the 
two waves an looks to remain high and dry. Have left slight chance 
probability of precipitation going for the Tuesday/Tuesday night time frame...but not 
looking to good to see anything at this time. After this...southern wave that 
gets hung up over The Rockies Wednesday is prognosticated by the 
European model (ecmwf)/GFS to drift south of the area Friday as another strong 
shortwave rounds polar vortex over Hudson Bay. Unfortunately...area 
looks to be to far from either one of these waves...so have started 
Friday off dry until it becomes more apparent one of these systems 
will get close enough to the region to actual warrant the mention 
of probability of precipitation. 


Of interesting note...looking back at snowfall data for the Twin 
Cities from the state climatologist...every March since 1884 has 
had measurable snowfall /lowest was 0.1 inches in 1981/ and with 
now through Friday /the 26th/ looking snow free...we may be on our 
way to a unique climatological event here in the Twin Cities of no 
snow for the month of March. The cities average nearly 10 inches 
for the month. Will give US something interesting to keep an eye 
on as we near the end March. 


&& 


Aviation.../18z taf issuance/ 
widespread MVFR ceilings are in place across the region at the 
current time in the area of cold advection and cyclonic flow 
behind the cold front which moved through. The boundary layer flow 
is expected to become anticyclonic late this afternoon and tonight 
with the boundary layer relative humidity also dropping off as increasing 
subsidence works into the area behind the shortwave trough 
currently over northwest Minnesota. Expect to see the current 
ceilings rise a little bit this afternoon owing to the typical 
diurnal fluctuations... but Don/T expect as much of a rise as 
suggested by the NAM... mainly given the cold advection and lack 
of much temperature rise. The clearing trend tonight should 
generally occur from northwest to southeast... although some 
clouds may hang on a bit longer of the far west and southwest due 
to the lingering layered clouds above the drying boundary layer. 
Some diurnal cumulus can be expected on Saturday... but for now it 
appears this will mainly be scattered or at or above 3k feet. 


Kmsp... main uncertainty/challenge is with the ceiling height in 
the first 6 hours... which looks like it may hang around very 
close to 3k feet before rising again then eventually scattering out 
tonight. Otherwise... fairly confident that conditions will be VFR 
through the period with the gusty winds settling down this evening. 






&& 


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


$$ 


Mpg/trh