Weather

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fxus63 kgid 280520 
afdgid 


Area forecast discussion 
National Weather Service Hastings NE 
1220 am CDT Thursday Aug 28 2008 


Aviation...the primary issue for the 06z taf will be the 
possibility of fog early this morning. Fog has begun to develop in 
a few spots already this morning...and 00z NAM bufr soundings 
suggest fog is likely at kgri early this morning. Will bring 
visibilities down into the 2-4sm range...but show rapid 
improvement as a frontal boundary pushes through the region. Winds 
also increase out of the north and become gusty behind the front. 
Winds should then subside during the evening. 


&& 


Previous discussion... /issued 310 PM CDT Wednesday Aug 27 2008/ 


Short term...this evening through Thursday night. Primary forecast 
concern centers around thunderstorm chances. 


Early this afternoon surface observations depicted a nearly stationary 
trough of low pressure over the Central Plains. Satellite imagery 
showed a shortwave upper level trough tracking across the 
northern plains. The surface trough is somewhat detached from the best 
upper level forcing across our area resulting in only minimal 
precipitation chances. The most favored region for showers and 
thunderstorms tonight into Thursday will once again be northeast 
of our County Warning Area with only an outside chance of an isolated storm 
building southwest into our County Warning Area. Even then...our more favored 
northeastern zones only have a slight chance of seeing 
thunderstorms. 


The surface trough slides southeast of our County Warning Area during the day on 
Thursday taking with it all chance of rain. Temperatures will be 
right around normal for this time of year with Thursday highs in the 
lower 80s. 


Long term...12z Friday through Wednesday. Main forecast concerns 
involve precipitation chances early next week. 


Still looks like a pleasant Holiday weekend shaping up for the area 
particularly Friday through Sunday...characterized by predominantly 
dry conditions and warming temperatures. The dry weather becomes a 
little more questionable by Labor Day...but precipitation chances 
still look quite low through the daytime hours. Surface high 
pressure slowly drifts east across the region on Friday under west 
to slightly northwest flow aloft around an elongated area of surface 
high pressure sprawling eastward across the southern Continental U.S.. after a 
crisp start to the day...abundant sunshine should help temperatures 
warm into the lower to middle 80s for highs. Models show hints of a 
middle-level shortwave ripple rounding the ridge and possibly brushing 
the southwest County Warning Area Friday night. Have kept the forecast dry with 
confidence in such a feature quite low even only a couple days 
out...but will need to keep an eye on this possibility. 


The surface high shifts east on Saturday while the Lee trough 
deepens to the west...resulting in increased return flow Saturday 
and Sunday. Meanwhile the upper ridge translates across the region 
on Saturday...followed by increasing southwest flow aloft on Sunday 
between the eastward shifting ridge and digging trough over the 
western Continental U.S.. this will spell warming temperatures Saturday and 
Sunday...with highs reaching into the upper 80s on Sunday. As the 
upper trough continues to push eastward through the intermountain 
west Sunday night and Monday...weak isentropic lift develops over 
the County Warning Area late Sunday night into Monday while subtropical moisture 
begins to flow northeast through the plains on the southwest flow 
aloft. Have some concerns that some isolated convection could 
develop on Monday with the increased moisture tap and weak 
isentropic lift...which could be supplemented by any lead 
shortwave energy ejecting ahead of the western trough. 
However...operational GFS seems to be the outlier with this 
possibility at this point...with the European model (ecmwf)/CMC Gem/GFS ensembles 
suggesting dry conditions through the daytime hours...and even the 
operational GFS would keep the better precipitation chances west 
and south of the County Warning Area until evening. Thus will hold off on probability of precipitation for 
the daytime hours on Labor Day...but will need to keep a close eye 
on this over the next few days. 


Precipitation chances increase Monday night and Tuesday as the upper 
trough lifts northeast into the northern plains...sending a cold 
front through the forecast area late Monday night into Tuesday. Main 
dynamics will stay well north of the area...but surface front and 
likely some middle-level frontogenetical forcing pushing through will 
bring a return of rain chances to the area. Models differ somewhat 
with how progressive the system will be...with the European model (ecmwf) trying to 
cut off the upper low sooner thus making it less progressive overall 
versus the GFS which is slower to cut off the system. For now 
have not lingered any probability of precipitation beyond Tuesday...hedging toward the 
slightly more progressive solution. After a warm Labor Day...the 
front will knock temperatures back down Tuesday and Wednesday. 


&& 


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


$$