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Area Forecast Discussion (AFD)

Issued by Norman, OK (OUN)

                            
726 
FXUS64 KOUN 242325
AFDOUN

Area Forecast Discussion
National Weather Service Norman OK
625 PM CDT Wed May 24 2017

.DISCUSSION...

&&

.AVIATION... /For the 00z TAFs/
Winds will become east-southeast this evening and then southeast
tomorrow strengthening during the afternoon with some gusts to 25
knots possible. VFR conditions will prevail. 

&&

.PREV DISCUSSION... /issued 412 PM CDT Wed May 24 2017/ 

DISCUSSION...
The primary forecast issue is the potential for severe weather on
Saturday. 

A rapid warming trend is expected to commence by Thursday and 
Friday as a low-level thermal ridge develops across the southern 
Plains. Model consensus indicates 850 mb temperatures to near ~30C
across parts of western north Texas by Thursday afternoon. 
Consequently, high temperatures will likely warm into the low 
100Fs across parts of north Texas. 

Late Thursday night into Friday, a cold front is expected to 
shift southeastward and stall near the Red River by Friday 
afternoon. Opted to lower temperatures below blended guidance 
across northern Oklahoma, where cooler air may advect southward. 
Hot temperatures are still expected across southern Oklahoma and 
adjacent north Texas Friday afternoon. 

A strong cap is expected to be in place with very warm 800-700 mb
temperatures aloft with 800 mb temperatures near >=22C. 
Therefore, expect the cap to suppress convection for Friday 
afternoon. The cold front is expected to lift northward as a warm 
front Friday night. 

There is a signal that an MCS will develop in the upslope flow 
across eastern Colorado/western Kansas Friday afternoon. This MCS 
may affect northern Oklahoma Saturday morning and result in a 
remnant boundary located somewhere across northern Oklahoma. 

By Saturday afternoon, a complex mesoscale pattern is expected to
develop across Oklahoma. Currently, the greatest uncertainties 
are 1) the location of a potential triple point and 2) the 
strength of the cap.

A dryline is expected to be situated somewhere in vicinity or 
perhaps just east of I-35 Saturday afternoon. In addition, a cold 
front will enter northwest Oklahoma Saturday afternoon. The 
remnant boundary from the aforementioned MCS may begin to lift 
northward Saturday afternoon--becoming an effective warm front. 
The location of any remnant boundary and its intersection with the
dryline and cold front would result in a triple point with an 
enhanced potential for severe weather in its vicinity.

The cap is expected to be weaker Saturday afternoon with at least
isolated storms possible. Both the 24/12Z ECMWF and GFS do 
initiate convection along the dryline. The NAM does not initiate 
convection; however, this is a known bias due to the BMJ 
convective parameterization scheme. 
 
The atmosphere south and east of these boundaries will be at 
least moderately unstable with progged MLCAPE >=3500 J/kg as a 
very moist airmass (dewpoints >=70F) is forecast in the warm 
sector. Effective bulk shear is also progged to be >= 50 knots. 
Therefore, the parameter space will be sufficient for severe 
thunderstorms, including supercells. Large to giant hail will be 
possible with significant CAPE in the hail-growth zone. 

There is some uncertainty on the exact location of the 
aforementioned mesoscale features (and the attendant triple 
point). For example, the ECMWF is the farthest west with the 
dryline while the 24/06Z NAM is the fastest with the cold front. 
The location of these features will modulate where the greatest 
risk for severe weather will be Saturday afternoon. The bottom 
line: Saturday will have to be monitored carefully as there will 
be the potential for very intense storms if they form. 

Thunderstorms will remain possible across southeast Oklahoma as 
the cold front passes by Saturday night.

Beyond Saturday, the Plains are expected to transition into 
northwest flow aloft. This will allow cooler temperatures across 
the area. In addition, there is a chance MCSs could affect parts 
of the area (especially northern Oklahoma) by the middle of next 
week. 

Mahale

&&

.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK  72  53  86  66 /   0   0   0   0 
Hobart OK         79  55  91  63 /   0   0   0   0 
Wichita Falls TX  79  56  94  74 /   0   0   0   0 
Gage OK           77  54  91  59 /   0   0   0   0 
Ponca City OK     68  51  82  62 /   0   0   0   0 
Durant OK         74  54  87  72 /   0   0   0   0 

&&

.OUN WATCHES/WARNINGS/ADVISORIES...
OK...None.
TX...None.
&&

$$

03/12