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Area forecast discussion...updated 
National Weather Service Norman OK 
1017 am CDT Friday Jul 18 2008 


Update... 
isolated showers continue in northern portions of forecast area this morning. 
Additional showers and thunderstorms will be possible this 
afternoon across portions of forecast area. Have extended slight chance probability of precipitation 
further south... especially in western OK and west North Texas. Surface 
trough expected to extend across eastern panhandles this afternoon. 
Models showing showers/thunderstorms developing near the trough and affect 
western portions of County Warning Area. Showers/thunderstorms may also develop near remnant 
outflow boundary that moved into northern OK this morning. A mesoscale convective vortex 
that developed with overnight convection will move across 
southern Kansas possibly into northern OK this afternoon. This disturbance 
may also aid in showers/thunderstorms this afternoon across portions of northern 
OK. Also adjusted hourly grids and sky cover to current trends. 
Will send updates shortly. 


Maxwell 
&& 


Previous discussion... /issued 342 am CDT Friday Jul 18 2008/ 


Discussion... 
convective complex over Kansas has a fairly large surface cold pool and 
continues to be fed by a 35-knots low level jet at 07z... per 850mb winds from 
hvlk1. Associated outflow boundary is moving southeast/S around 15kt and 
likely will make it into northwest/ncentral OK later this morning. Radar 
trends indicate several mesoscale convective vortex centers from southeast Nebraska into SW Kansas... 
drifting E/ESE. Questions today are whether the stuff in Kansas will 
persist long enough to affect north zones after 12z... and whether the 
low-level boundary will stay in the area long enough to provide a 
focus for redevelopment later on. More likely it will either 
dissipate or lift back north into Kansas. We will maintain low probability of precipitation across 
the north today for the possibility of the boundary lingering there... 
perhaps reinforced by differential heating. We may need to make 
some short-term adjustments to probability of precipitation depending on radar trends over 
the next few hours... but in general expect the greater chances to 
remain well to our north today. 


Otherwise it appears that the dog days of Summer will be upon US... 
with temperatures near to slightly above climatology and rain 
chances slim to none into late next week. Upper high currently over 
nm area prognosticated to strengthen a little and move to Colorado... then build 
into the central/S plains next week. 500mb heights and 850mb temperatures 
are prognosticated to rise... but only slightly over the next several days. 
Forecast temperatures generally will mirror these trends. One thing 
to watch for will be a slightly faster heating up over parts of 
ncentral OK where the more-numerous winter wheat fields are being 
cleared /an area known locally as the fhbc/. These areas may be 
among the first to Register 100+ highs by early next week. 


There are a couple features that may affect the area toward the end 
of the 7-day forecast period. One is the tropical system now S of 
hispanola. Both the GFS and the European model (ecmwf) suggest this system may 
develop and eventually get into the SW Gulf sometime next week. 
While direct effects would be well to our S... the associated 
slug of low/mid-level moisture eventually would be transported northwest 
and north across Texas/OK by late next week. Main effect would be higher 
dewpoints leading to a slight drop in maximum temperatures and a slight 
increase in mins. Effective temperatures during the day would be about 
the same given higher relative humidity. Other feature of note is another 
possible frontal intrusion from the north or NE Thu-Fri. European model (ecmwf) is 
somewhat of an outlier with a much stronger upper trough over the 
western Great Lakes next Thursday... and a cold front moving into the 
area next Thursday night. GFS and associated ensemble members have a 
much weaker upper system... and a sprawling upper high dominating 
the central/southern rockies and plains by next Thursday. Even the 
European model (ecmwf) has the upper high anchored over Texas/OK area... and it makes 
sense given that we are going into the climatologically-hottest 
time of the year. For now we will side with persistence... 
climatology... and the GFS... but we will bring the highs down a 
bit toward the latter half of next week to account for current 
guidance trends and the outside possibility of either a front or 
an increase in low-level tropical moisture. Should both happen... 
as suggested by the European model (ecmwf)... low probability of precipitation may need to be added toward 
the end of next week. 24 


&& 


Preliminary point temps/pops... 
Oklahoma City OK 95 70 96 69 / 10 10 0 0 
Hobart OK 95 72 99 72 / 20 10 0 0 
Wichita Falls Texas 97 72 98 74 / 20 0 0 0 
gage OK 92 70 97 70 / 40 20 0 0 
Ponca City OK 94 74 96 71 / 30 20 0 0 
Durant OK 97 72 95 72 / 10 0 0 0 


&& 


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


$$ 


25/30