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Area Forecast Discussion (AFD)

Issued by Omaha/Valley, NE (OAX)

                            
000
FXUS63 KOAX 202053
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
353 PM CDT Fri Sep 20 2019

.SHORT TERM...(Tonight through Monday)
Issued at 351 PM CDT Fri Sep 20 2019

Water vapor imagery this afternoon showing large scale flow aloft 
consisting of a large high pressure dome situated over the eastern 
half of the CONUS along with a well amplified longwave trough 
across the western half and an embedded circulation centered over
the Great Basic. 

Meanwhile surface low pressure was centered over ND with a strong 
thrust of Gulf moisture into the Central Plains. Morning PW plow 
revealed 1.4" at KOAX and 1.6" at KTOP. Latest obs were showing, for 
the most part, dew points around 70 over the CWA.

Models are in agreement large scale pattern will become more 
progressive in nature beginning tonight when Great Basin upper low 
gets ejected and moves toward the western Dakotas late tonight. With 
this, synoptic scale lift increases over the region in conjunction 
with associated cold front approaching the CWA. Models are in decent 
agreement showing precip breaking out within the warm sector ahead 
of the front early Saturday morning. The boundary is progged to 
become quasi-stationary Saturday afternoon and take on an 
orientation from east-west over the southern CWA. 

With near stagnant differential divergence acting as a forcing 
mechanism, conditions will become quite favorable for heavy 
rainfall Saturday night into early Sunday morning. As of now, 
models are pointing to the CWA for possible excessive rainfall 
where precip efficiency will be most prevalent. PWs approximately
over 150% of normal will phase with deep low level warm cloud 
layer and max omega. Precip activity south of I-80 should be 
coming to a gradual close through early Sunday morning. As of now,
rainfall totals over 2 inches appear possible over 
Nemaha/Pawnee/Richardson counties in NE and Page county in IA. 
Thus, a Flash Flood Watch will be in effect Saturday night into 
early Sunday morning over portions of southeast NE and southwest 
IA. 

Increasing heights building in from the west will result in very 
pleasant conditions Sunday afternoon into Monday. 

Highs on Saturday will be in the low 80s. On Sunday and Monday 
highs will be in the 70s.

.LONG TERM...(Monday night through Friday)
Issued at 351 PM CDT Fri Sep 20 2019

Precip chances in the extended periods will come in part to several 
impulse associated with the next system digging down the western 
states and eventually bottoming out over the southwestern CONUS. 
The GFS and ECM differ slightly with timing of main circulation 
into the Central Plains. GFS progs in into the CWA early Friday 
morning while the ECM brings it through Friday afternoon. 


Highs on Tuesday will be in the upper 80s. Highs in the low/mid 70s 
then Wednesday through Friday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1158 AM CDT Fri Sep 20 2019

A cold front over the western Dakotas as of late morning will
shift east across the northern Plains tonight and eventually
through the mid MO Valley on Saturday. Gusty south winds ahead of
the front will draw an increasingly moist air mass north through
the region. The net result is for the development of MVFR ceilings
at all TAF locations tonight. While isolated showers and
thunderstorms will be possible late this afternoon into early
evening in the vicinity of KOMA, and overnight at KOFK, better 
thunderstorm potential will not materialize until Saturday 
afternoon along and south of I-80.


&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Flash Flood Watch from Saturday evening through Sunday morning 
     for NEZ068-089>093.

IA...Flash Flood Watch from Saturday evening through Sunday morning 
     for IAZ090-091.

&&

$$

SHORT TERM...DEE
LONG TERM...DEE
AVIATION...Mead