Area forecast discussion 
National Weather Service Omaha/valley NE 
557 PM CDT Sat Jul 23 2016 


Short term...(tonight through tuesday) 
issued at 350 PM CDT Sat Jul 23 2016 


12z upper-air analysis and early afternoon water vapor imagery 
revealed a polar-branch short-wave trough from Saskatchewan into the 
northern High Plains with downstream ridging present from Manitoba 
into Ontario. Meanwhile, a lower-latitude perturbation, embedded 
within a sub-tropical moisture plume was progressing from the mid 
Missouri Valley into upper Midwest. Expect the former impulse to 
track across the Canadian prairie provinces late today and tonight, 
effectively flattening the antecedent mid-level ridge over the 
north-central states. Meanwhile, an associated cold front 
stretching from the central Dakotas through north-central into 
southwest Nebraska as of 20z will advance southeast through much 
of the mid Missouri Valley tonight, with this feature eventually 
clearing our southeast Nebraska and southwest Iowa counties Sunday 
morning. 


Persistent mid and high-level cloudiness has stunted daytime 
heating, especially across our southern County Warning Area today with 20z temperatures 
commonly in the upper 80s to lower 90s. However, given heat 
indices currently hovering around advisory criteria at many 
locations, we will maintain the going excessive heat warning until 
7 PM. Otherwise, consensus of latest model guidance is suggestive 
that the strongest large-scale forcing for ascent and associated 
pre- frontal thunderstorm development will remain to our northeast 
tonight. However, recent visible satellite imagery shows a growing 
altocumulus castellanus field ahead of the front from north of Yukon to near onl to 
bbw. As such, we will maintain slight chance pops along the front 
tonight. 


Mid and high-level clouds will increase across the area Sunday in 
advance of a short-wave trough amplifying from the upper Mississippi 
Valley into central South Dakota. Weak vorticity advection and some 
frontogenetical forcing may be sufficient to promote a few mid-level 
showers and storms across our far northern counties Sunday 
afternoon. Meanwhile, in the south, weak warm advection atop a 
shallow frontal surface will maintain a chance for isolated showers 
and thunderstorms there as well. The increased clouds and slightly 
cooler, Post-frontal air mass should yield highs largely in the mid 
80s. 


A surface high will develop southeast through the mid Missouri 
Valley Sunday night with the subsequent deepening of a Lee trough 
over the northern High Plains on Monday. Aloft, mid-level heights 
will build over the northern plains during that time frame, ahead of 
low-amplitude disturbance which will emerge into the northern High 
Plains Monday afternoon. Warm advection will strengthen over 
southeast Nebraska Sunday night in conjunction with the nocturnal 
llj, where we have maintained the going slight chance to chance 
pops. Conditions will generally be dry Monday with highs in the 
mid to upper 80s. 


The aforementioned short-wave trough moving into the northern High 
Plains Monday afternoon will be the first in a series of 
disturbances tracking east-southeast through the Dakotas and mid 
Missouri Valley Monday night through the middle part of this 
upcoming week. This pattern will favor multiple rounds 
thunderstorms over the region with a risk for flooding rains and 
possible severe weather, namely in the Tuesday night to Wednesday 
night time frame. 


Long term...(tuesday night through saturday) 
issued at 350 PM CDT Sat Jul 23 2016 


As mentioned above, the polar-branch of westerlies will become 
increasingly active around midweek as the prevailing flow 
transitions to northwest over the north-central Continental U.S.. by the end of 
next week into early next weekend, the 12z deterministic runs of the 
European model (ecmwf) and GFS indicate pronounced ridging over western North 
America with a broad downstream trough near or east of the 
Mississippi Valley. This large-scale pattern configuration will 
continue to support a chance of thunderstorms with temperatures 
near or slightly below seasonal normals. 


&& 


Aviation...(for the 00z tafs through 00z Sunday evening) 
issued at 555 PM CDT Sat Jul 23 2016 


Generally expect VFR conditions through the period. Mid level 
clouds will move across the taf sites overnight. There could be 
some isolated rain showers or thunderstorms and rain but coverage generally looks to low 
to mention. Winds will turn to the northwest or north overnight 
as the frontal boundary moves through. 


&& 


Oax watches/warnings/advisories... 
NE...excessive heat warning until 7 PM CDT this evening for nez011- 
012-015>018-030>034-042>045-050>053-065>068-078-088>093. 


Iowa...excessive heat warning until 7 PM CDT this evening for iaz043- 
055-056-069-079-080-090-091. 


&& 


$$ 


Short term...Mead 
long term...Mead 
aviation...Miller 






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