Area forecast discussion 
National Weather Service Omaha/valley NE 
1256 PM CDT Friday may 24 2013 




Aviation...18z tafs for koma...klnk and kofk. 


VFR conditions will prevail at least through early this evening. 
Thereafter...expect scattered thunderstorms and rain development in central Nebraska with 
activity pushing into eastern Nebraska toward midnight. Occasional strong 
thunderstorms and rain will be possible in response to strengthening low level jet. Early 
Sat morning...influx of low level moisture will result in IFR ceilings 
settling in over eastern Nebraska through most of the morning hours. 


Dee 




Previous discussion... /issued 342 am CDT Friday may 24 2013/ 


Discussion... 
looks like quite the active weather pattern will develop over the 
middle of the country today and remain in place the next 7 days. 
Upper lows/troughs moving toward the East Coast and along the West 
Coast will keep our part of the world under weak ridging at least 
through Sunday. Then more southwesterly flow takes over as western 
trough moves a little east. Despite weak ridging aloft...several 
impulses will move overhead which will trigger off-and-on episodes 
of potential precipitation over the weekend. 


At lower levels...moist southerly flow at the surface through at 
least 850mb is forecast to overspread all of the plains later today 
and persist through much of next week. 850 dew points were already 
10-14c from southwest Kansas through the Texas Panhandle...and this 
air should be moving into western Nebraska today then spread east 
through western Iowa tonight. At the surface...easterly flow was 
keeping dew points in the 40s this morning...but 60s dew points in 
the Southern Plains will surge north and become entrenched over our 
County Warning Area on Saturday. 


So with moisture becoming increasingly favorable for precipitation 
and weak impulses moving overhead...really can not rule out at least 
small chances for showers/thunder at any time through the Holiday 
weekend. For today...moisture will not be as robust...but decent middle 
level warm advection will be sweeping through eastern Nebraska during 
the day with initial surge of middle level moisture. Already seeing 
signs of that warm advection as middle level clouds have expanded from 
western into central Nebraska. Only precipitation noted so far was in 
northwest Kansas...but short range and mesoscale models are all 
hinting at hit-and-miss convection spreading into eastern Nebraska 
during the day. So will maintain small chances in our west this 
morning...with better chances in the afternoon as southerly flow 
becomes more robust. 


Perhaps the best chances for convection through the weekend will 
come during the nighttime hours as low level jet dynamics contribute 
to forcing. Afternoon instability will certainly increase each day 
through Monday...and any upper impulse could release that 
instability. But nailing down those impulses with much more than a 
day or so lead time is nearly impossible. So forecast will reflect 
chances for thunderstorms each of the next several days...with 
more likely probability of precipitation coming during the evening and overnight hours. 


Heavy rain may occur with any of these convective episodes as well. 
Precipitable water values are forecast to come close to 1.5 
inches...which is well above normal levels for this time of year. 
Plus freezing levels approaching 13000 feet suggest warm cloud depth 
could enhance rainfall production. Will have to watch how and where 
things develop over the next couple of days to fine tune any 
possible flooding concerns. 


The rest of the week Tuesday through Thursday may bring better 
chances for severe storms in the Central Plains. Western upper 
trough should be pushing into the plains with stronger middle level 
flow and slightly cooler air aloft spreading into the plains. 


Dergan 


&& 


Oax watches/warnings/advisories... 
NE...none. 
Iowa...none. 
&& 


$$ 


99/99