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Area forecast discussion 
National Weather Service Norman OK 
216 PM CDT sun Sep 7 2008 


Discussion... 
main weather event in the near term will be a strong cold frontal passage 
Monday afternoon/night. Surface analysis currently identifies 2 
boundaries - one strengthening from Wyoming and NE Colorado across S and east Nebraska 
and another lifting north across north OK in the differential heating zone S 
of a persistent stratus deck. Latter will continue to lift north tonight 
and the two eventually will consolidate over Kansas by Monday morning. Surface 
low will develop in or near southeast Colorado tonight in response to upper trough 
now digging southeast across Montana. Strengthening low level jet tonight will enhance 
low-level warm advection and frontogenetic forcing over Central 
Plains resulting in increasing convection near and north of the surface 
baroclinic zone - most likely remaining north of OK. Strong 
frontogenetic lift will further strengthen the front early Monday 
as it begins moving southeast. NAM indicates a sharp thermal gradient and 
strong north winds behind the surface front... which should make far northwest OK 
by 18z and the I-44 corridor by 00z Monday evening before exiting 
southeast corner of County Warning Area by around 09z. Decent warming is expected early 
Monday in the drier and slightly veered low-level flow ahead of 
the front... especially west zones... thus highs have been raised 
slightly in most areas. This front will have a bite to it... 
likely sending most areas from late-Summer heat straight into 
blustery jacket weather within a couple hours. NAM surface T fields 
support temperatures dropping sharply from 80s/l90s into the 60s in 2-3 
hours Monday afternoon/evening. Have used the NAM surface T and wind fields 
to depict what is likely to be a decidedly non-diurnal temperature 
change... and to get more resolution into the grids as far as the 
sharp wind shift and thermal gradient. 


Forecast beyond Tuesday is quite a challenge. General pattern around 
midweek indicates broad west-southwest flow aloft from northwest Mexico and Baja California 
region across the S plains... downstream from a S-branch trough over 
CA/NV. Another stronger North-Branch trough is prognosticated to dig into the north 
rockies around Wednesday and move east Thursday... likely pushing another front 
into the area Thu-Fri. Beyond midweek... models go off in multiple 
directions regarding individual features in the middle-latitude flow. 
Ironically... the feature one might suspect most as becoming the 
proverbial monkey wrench in the machinery is the one feature the 
medium-range models most agree upon. GFS/dgex/ECMWF/UKMET all are 
remarkably well clustered with Hurricane Ike reaching the Upper Texas 
coast next weekend. Be that as it may... GFS has trended 
significantly wetter for Wednesday and beyond over the S plains. Mex 
guidance probability of precipitation Wednesday-Sat have increased from general 15pct or less 24 
hour ago to widespread 30-50pct over much of the area. In order to 
maintain forecast continuity we have ditched the 12z/07 gfsmos 
probability of precipitation/weather and reloaded the official grids published last night. For 
day7/sun we will give a nod to the well-clustered solutions 
regarding Ike moving into the arklatex... and paint higher probability of precipitation southeast 
and lower northwest. (That being said... newly-arrived 12z European model (ecmwf) keeps 
Ike on a more S track and brings it into far S Texas next Sat. Sigh...) 
gfsmos maximum/min temperatures have been loaded Wednesday-sun with relatively 
minor modifications to better match up with consensus of 
surrounding office grids. 24 




&& 


Preliminary point temps/pops... 
Oklahoma City OK 67 88 55 73 / 10 20 20 10 
Hobart OK 66 91 54 74 / 10 20 20 10 
Wichita Falls Texas 68 92 58 82 / 10 10 20 20 
gage OK 61 87 50 72 / 10 20 10 10 
Ponca City OK 62 88 55 72 / 10 30 20 10 
Durant OK 68 87 61 85 / 10 10 20 10 


&& 


Oun watches/warnings/advisories... 
OK...none. 
Texas...none. 
&& 


$$ 


25/24