964 
fxus63 keax 202049 
afdeax 


Area forecast discussion 
National Weather Service Kansas City/Pleasant Hill MO 
348 PM CDT Sat Mar 20 2010 


Discussion... 


Models are all in pretty good agreement with regard to movement of 
the upper level low. Watervapor loop shows the upper low/pv anomaly 
digging and beginning to move east across northern Texas and 
Oklahoma. Models show this feature to continue east-southeast along 
the Red River valley into southern Arkansas. At the surface...the 
low pressure area currently moving east across Arkansas will stall 
and pivot over eastern Arkansas through Sunday morning. Dry air in 
the lower levels is continuing to be drawn into northern Missouri on 
strong northerly winds gusting up to around 30 miles per hour. This will mean a 
sharp cut off to the additional measurable snowfall. 


Appears one deformation band setting up generally from about Wichita 
to Kansas City. Radar imagery shows vorticity maximum spinning over northwest 
Arkansas...with a more convective type band with higher moisture 
stretching north-northeast toward central Missouri...which will 
likely become the main deformation band overnight. So think as the 
upper system continues east and and the aformentioned vorticity maximum 
sequesters the bulk of the moisture...the western deformation band 
will diminish during the evening as the eastern band becomes better 
established. 


Meanwhile light to occasionally moderate snowfall will continue 
across much of the forecast area...from about Saint Joseph to 
Bethany eastward...with the heavier snow expected mainly southeast 
of a Kansas City to Kirksville line. Additional snowfall of 1 to 2 
inches is expected across northern sections...with greater amounts 
of around 4 inches additional expect south of a line from Paola to 
around Sedalia. So will cancel the far northwest two tier of 
counties from the advisory...leaving the rest of the 
advisory/warning outline as is. It is possible the warning will 
need to be extended farther into central Missouri. 


However as the upper level system continues to approach the Arkansas 
area...a significant amount of warm air will get drawn in from the 
east. Expect snow this evening and early overnight...to change back 
to a winter mix from east to west before daybreak. How far west it 
will make it before the precipitation end remains in question. Still looks 
like precipitation will shut off from northwest to southeast during the day 
Sunday. 


Short/medium range (sun night-sat)... 


Fairly quiet conditions expected for the beginning of next 
week...with warming temperatures and chance of rain by the latter 
portions of next week the primary concerns. Once powerful upper level 
storm system begins to eject eastward into the Tennessee River 
valley Sunday night...mid-lvl ridging will quickly take its place 
through Tuesday...ahead of yet another southeast diving Pacific short wave trough. 


Given the expectation of snow and perhaps some deeper snowpack in 
the south...temperatures will be very difficult through Wednesday. On 
Monday...expecting minimal mixing overall as surface ridge axis will be 
sliding through The Heart of the County Warning Area. Given nearly full sunshine and 
a quickly melting snow cover would expect a decent rebound in temperatures 
into the 40s. Tuesday will provide a more favorable condition for 
deeper mixing and warmer temperatures as low-level ridge axis slides to 
the east of the area. By Tuesday afternoon 925:850mb wind should average 
20-30knots with 850mb air some 8-10 degrees advecting NE. Would like 
a slightly better surface wind fetch...but still feel upper 50s to lower 
50s may be attainable despite lingering snow cover and the potential 
of a bit of lingering fog. Ensemble spreads are much lower on 
Tuesday with temperatures between the middle 50s and low 60s. 


Will also be concerned with the potential for fog late Sunday night 
and again Monday night and Tuesday night as warmer air begins to 
overtake the vast snowpack. 


A bit more uncertainty arrives by Wednesday and continues through Friday. 
GFS/ec/gefs forecasts pull yet another short wave trough through the Pacific northwest on 
Sunday...dropping the short wave into the Great Basin much like this 
weekends storm. Newer model guidance is a bit faster than previously 
thought as the wave is quickly caught up in the fast northern 
stream. Have lowered temperatures slightly on Wednesday as a quick moving 
cool front will race through the area on Wednesday. Not a ton of 
cold air with this front...but may be enough to limit temperatures slightly 
with a north wind prevailing. The 12z GFS has trended towards the 
more bullish European model (ecmwf) solution for Thursday. Despite moisture scouring out of 
the atmosphere behind this larger upper level trough...feel given the 
amplitude of the approaching wave...the currently prognosticated low-middle 
level warm air advection...and its ability to tap into a Richer airmass...precipitation 
should be attainable. Thus...have bumped up probability of precipitation a bit for late Wednesday 
night and Thursday. 


Beyond Thursday...stagnant pattern looks to persist into the weekend 
as the region will struggle to consistently remain warm. Given the 
persistence of this pattern...the suggestion by the European model (ecmwf) and GFS of 
yet another quickly diving Pacific northwest short wave by the end of next weekend 
would be plausible. Ahead of this wave...would expect another 1-2 
day bump up in temperatures. 


Dux 


&& 


Aviation... 


Second wave of accumulating snow...with ceilings/visibility generally in the 
IFR/low MVFR Cat...has moved into the kc area. While this snow is 
not accumulating as much as the first with rates much less due to a 
layer of dry air mixing in...some accumulation is expected. That 
being said...light snowfall on pavement has seemed to thus far melt 
on contact. Light snow is expected to continue into the evening. 
Little or no additional accumulating snow is expected at kstj with 
kmci likely on the northern edge of 1 to possibly 2 inches...mainly 
on grassy surfaces. MVFR ceilings will last into this evening before 
the stratus departs to the east and VFR conditions return by Sunday 
morning. 


Winds may be of more concern with this system. North winds of 15 to 
20 kts with gusts of 25 to 30kts will persist across the region 
through at least the evening hours...leading to some 
blowing/drifting snow and therefore slushy areas on pavement. 


Nrr 


&& 


Eax watches/warnings/advisories... 
MO...Winter Storm Warning until 1 PM CDT Sunday for moz043>045-053- 
054. 


Winter Weather Advisory until 7 am CDT Sunday for moz007-008- 
014>017-021>024-028>030-037. 


Winter Weather Advisory until 1 PM CDT Sunday for 
moz025-031>033-038>040-046. 


Kansas...Winter Storm Warning until 1 PM CDT Sunday for ksz057-060. 


Winter Weather Advisory until 7 am CDT Sunday for ksz103>105. 


&& 
$$ 

National Weather Service Glossary of Abbreviations

Non-Expanded Version (with abbreviations)