fxus64 koun 210222 

Area forecast discussion 
National Weather Service Norman OK 
922 PM CDT Fri Apr 20 2018 

decreased the chance of rain for this evening across central 


numerous showers and isolated thunderstorms continue across 
northwest Oklahoma this evening. These showers/storms appear to be 
associated with a lead shortwave trough/vort Max that will 
continue to lift north-northeastward. This will initially prevent 
much eastward progress of the rain. Therefore, the chance of 
showers/storms was decreased markedly for this evening across 
central Oklahoma. 

Behind this lead wave, the primary wave will approach the 
Southern Plains. As this happens later tonight, a low-level jet 
and attendant isentropic ascent will result in widespread rain to 
develop (which will facilitate the eastward shift of rain). The 
greatest ascent appears to be across south central into central 
Oklahoma by late tonight into Saturday morning. Where there is 
essentially a 100% chance of rain. 



Previous discussion... /issued 625 PM CDT Fri Apr 20 2018/ 

21/00z tafs. VFR conditions expected to prevail majority of area 
through 06z before conditions deteriorate with incoming ra/tsra. 
As upper storm system moves over the region, cigs will fall and by 
12z and beyond, widespread IFR conditions are expected both during 
and after the heavier rain activity moves east. Added thunderstorms and rain to all 
sites given potential for at least embedded thunderstorms and rain but impacts 
should be brief at any terminal. 

Previous discussion... /issued 344 PM CDT Fri Apr 20 2018/ 

showers and a few thunderstorms are just west of our forecast 
area as of 3:30 PM, and the area of rain will continue to move 
northeast this afternoon and into the evening. Short-range models 
consistently show another band of rain that will form ahead of 
this one later this evening, possibly bringing rain into central 
Oklahoma a couple of hours before midnight. 

Showers and a few thunderstorms are forecast to increase in 
coverage through Saturday, before the system begins to move away 
to the east Saturday night and Sunday. 

Surface-based instability will be generally lacking, and most- 
unstable cape values will be too low to support anything beyond 
isolated marginally severe storms. In short, severe storms are 
unlikely in our forecast area through the event. 

As this system departs, northwest flow aloft will become 
established. This is typically a dry pattern in winter, but we 
will have at least a chance of showers and thunderstorms with a 
couple of fronts that move into Oklahoma/North Texas. The first 
is expected on Tuesday, and the second one late in the week, 
probably Friday. Again, severe weather is relatively unlikely with 
both fronts. 


Preliminary point temps/pops... 
Oklahoma City OK 49 56 45 62 / 80 100 60 10 
Hobart OK 50 57 44 66 / 80 90 20 0 
Wichita Falls Texas 52 59 45 67 / 80 80 20 0 
gage OK 47 53 41 64 / 90 60 20 0 
Ponca City OK 47 54 45 62 / 80 90 60 10 
Durant OK 50 58 50 65 / 30 90 70 10 


Oun watches/warnings/advisories... 

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