811 
fxus63 kmpx 161839 
afdmpx 


Area forecast discussion 
National Weather Service Twin Cities/Chanhassen Minnesota 
139 PM CDT Tuesday Mar 16 2010 


Update... 


18z aviation discussion added below. 


&& 


Discussion... 
it appears we will finally be ridding ourselves of the low 
clouds and fog which has plagued much of the area for the past 
week or so. Latest water vapor imagery and RUC upper air analysis 
show a few weak embedded vorticity maxes currently moving east across 
the state... with the more significant shortwave just beginning to 
enter the western edge of Minnesota. It is a fairly sharp trough 
with an equally Sharp Ridge behind it. The subsidence behind it 
appears to be doing a good job of clearing out the cloud cover... 
so it will just be a waiting game for our area as the ridge folds 
over across the state this afternoon into tonight. Some spotty 
light rain in the area of weak forcing and deeper saturation ahead 
of the trough will continue for a good part of the day today... 
but Don/T expect it to linger into tonight. The NAM... GFS... and 
European model (ecmwf) are in fairly good agreement on the large scale features the 
next several days...so generally used a consensus approach with 
their guidance and the previous forecast. Overall...the trend 
will be for a scouring out of clouds and moisture over the next 24 
hours... then a steady warming with continued fair weather into 
early Wednesday... followed by the arrival of cooler weather for 
the end of the week and the weekend as the upper jet shifts south 
of the area. 


For today... it looks like mostly cloudy skies will prevail across 
the area and the weak forcing ahead of the upper trough will 
continue to squeeze out some light rain... mainly over the central 
and eastern portion of the area where deeper moisture is present. 
Dnva will arrive in earnest late this afternoon into tonight... 
which should work to scour out the cloud cover from northwest to 
southeast. High temperatures today shouldn/T rise too dramatically 
given the clouds... although portions of west central Wisconsin 
could Jump Up quickly before the clouds arrive... so kept warmest 
readings in that area. Ridging will prevail tonight through 
Wednesday night... with a good surge of warmer temperatures aloft 
looking to arrive on Wednesday into Wednesday night ahead of the 
next shortwave and associated frontal boundary which look to move 
through on Thursday. The inversion on Wednesday looks to be a bit 
sharper than the past few days... so it may not warm as 
dramatically as one might expect given the warm temperatures aloft. 
However... with winds expected to pick up some mechanical mixing 
could help with the thermal mixing... so bumped up highs a bit and 
wouldn/T be shocked if things wound up warmer still. 


Continued to keep Thursday dry for now... since moisture ahead of 
the frontal boundary look anemic. Temperatures on Thursday should 
still manage to warm up nicely... with the better cold advection 
not arriving until later in the day. Didn/T make any substantive 
changes for Friday into Saturday... with some chance for precipitation 
across the southern portion of the area where the tightening 
baroclinic zone will be positioned north of the shortwave and 
surface low that will be moving northeast from the Southern Plains 
as we head through the weekend. The 00z GFS and European model (ecmwf) continue to 
keep the bulk of any precipitation south and east of our area... with 
slightly colder than normal temperatures and primarily dry weather 
in place across Minnesota. 


&& 


Aviation.../18z taf issuance/ 


Surface ridge this afternoon sliding south across Dakotas. WV imagery 
showing nice shortwave over central Minnesota dropping south across area. 
Rain ahead of this wave now confined to southeast Minnesota and is quickly 
pulling out of the msp area and outside of a few light showers at 
msp through 20z...all taf sites will be dry for the remainder of 
the taf period. Dry air associated with the high pressure scouring 
out clouds across northwest into central Minnesota. Seeing strong low level q 
vector divergence moving in this evening...so this should help to 
continue scouring things out into tonight. Unfortunately...there 
are indications from isentropic sfcs on the RUC/GFS that clouds 
stuck near the eastern Minnesota border right now will linger there well into 
tomorrow morning...so there are question Marks as to when msp will 
finally break out. Other problem to watch for tonight is the 
return of dense fog. Mav/met/lamp bring dense fog into all 
terminals but stc/eau. Pressure gradient will be slackening 
overnight...with winds dropping off...but they do not look to go 
calm...so confidence in dense fog forming is not too high at this 
point. However...with clouds holding temperatures down this 
afternoon and no strong push of dry air...will not take much for 
temperatures to get down to dewps. At this point brought visibilities down to 
1sm with some lower tempo groups...but this will be the problem to 
watch tonight. 


Kmsp...low clouds very persistent across the area as band of 
moisture is trapped on eastern edge of surface ridge. Seeing sporadic 
heights in this cloud band with msp on the low end of 
heights...with MVFR/VFR ceilings noted to the north. Should see gradual 
increase in heights this afternoon before things finally clean out 
after 06z. Though all guidance shows visibilities going down to at least 
1/2sm in fog in the morning...not too confident in this occurring as 
there is no snow left to add moisture to the atmo and winds look 
to stay up around 5kts. For direction...winds will remain northwest this 
afternoon/evening...but by tonight...center of surface ridge will be 
south of the area allowing the winds to turn to the west by they 
morning rush. 


&& 


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


$$ 


Trh/mpg