637 
fxus63 kgid 182051 
afdgid 


Area forecast discussion 
National Weather Service Hastings NE 
351 PM CDT Thursday Mar 18 2010 


Short term...tonight through 12z Saturday. Main forecast 
challenge will be timing of transition between rain and snow...and 
determining snow amounts from tonight through Friday night. 


Water vapor loop depicts a strengthening shortwave trough in the 
northern rockies heading our way as it continues to dampen the 
positively tilted high amplitude ridge over our area. The trend 
continues to be more and more progressive. The surface cold front 
has already made it through a good chunk of Nebraska and could be 
in the Tri-Cities area by evening. Middle-level frontogenetic forcing 
really gets going late tonight into Friday. Any large scale 
forcing will remain well south of the County Warning Area...as the closed low 
developing with this wave will be well to the south as well. One 
area of concern will be the possibility of a narrow band of 
enhanced instability somewhere over the County Warning Area mainly toward Friday 
morning. MUCAPES near 200 j/kg...negative epv...and continued 
middle- level strong middle- level frontogenetic forcing makes ME a bit 
worried that this may occur...which could easily tack on another 
couple inches of snow and some thunder as an addition to the 
weather. The main problem is that it is extremely difficult to 
figure out where such a small feature may set up...and almost have 
to see the virtual whites of the eyes before making any kind of 
advisory decision. Generally speaking...the main concern outside 
of this band developing will be reduced visibility as the snow 
falls with the strong north wind predicted. With such a warm day 
today...along with already relatively warm soil 
temperatures...much of the snow to fall will melt...so the threat 
of blowing snow from snow already reaching the ground is of less 
concern...except in the potential area of enhanced convection. 
Kept the general 1 to 3 inches going for generally snow 
amounts...slightly shifted to the south. The one caveat will be 
where the narrow axis of instability might set up for Friday...if 
it happens at all. 


Increased chances of precipitation to 100 percent. Plenty of 
moisture and lift leaves ME no doubt here. Temperatures will go 
nowhere on Friday and will generally tumble through the day with 
the expected cold air advection. 


Long term...12z Saturday through Thursday. Lingering 
precipitation will still be possible across extreme southeastern 
portions of our County Warning Area Saturday morning...however these precipitation 
chances will quickly diminish by middle day as low to middle level 
frontogenesis pushes off to the southeast...leading to dry 
conditions through the rest of the day. Continued northerly flow 
and cold air advection at the low levels...along with cloud cover will promote 
cool conditions on Saturday with high temperatures across the County Warning Area 
likely not climbing out of the low to middle 30s. Much more pleasant 
weather to follow Sunday...Monday and Tuesday as upper level 
ridging and return flow at the surface commence. Guidance 
continues to suggest afternoon highs in the 40s and low 50s 
Sunday. With 850mb temperatures rising to near +8 c on Monday and Tuesday 
and guidance suggesting highs in the 50s and 60s both 
days...certainly appears as though we are heading for a couple 
days early next week with above normal temperatures. GFS and ec 
both continue to indicate a middle level disturbance pushing through 
the region by middle next week...so have maintained increased cloud 
cover Wednesday and Thursday with slight chances for 
precipitation. 


&& 


Previous discussion... /issued 1201 PM CDT Thursday Mar 18 2010/ 


Aviation...18z kgri taf. VFR conditions to continue at the kgri 
terminal through 04z. The passage of a cold front will then bring MVFR 
to IFR ceilings to the terminal. A shift in surface winds from 
the south to the north will also occur around 02z...with pressure 
rises Post-frontal passage increasing surface winds to near 20 kts...gusting 
to near 25 kts. Low to middle level frontogenesis behind the surface 
front will promote precipitation at kgri by 10z...with a rain and 
snow mix then expected through the rest of the forecast period. 
Precipitation will increase in intensity Friday morning...likely 
resulting in some visibility restrictions at kgri by 14z. 


&& 


Gid watches/warnings/advisories... 
NE...none. 
Kansas...none. 
&& 


$$ 


Heinlein/Bryant