Severe Weather Discussion for March 24 – 30, 2014.
– Severe thunderstorms are possible for central and eastern Oklahoma on Thursday.
– Showers and thunderstorms are possible across Oklahoma on Wednesday.
– Fire danger on Thursday.
– Temperatures will be in the low 60s Monday, mid 50s Tuesday, upper 50’s Wednesday, mid 70s Thursday, mid 50s Friday, mid 60s Saturday, and low 70s Sunday.
– Severe Thunderstorms: 20%
Unseasonably cold temperatures will give way to a decent warm up on Monday as a reinforcing shot of cold air moves into the region for Tuesday. Beyond that, models agree that the persistent mid-level ridge to our west will finally weaken and shift east as progressive 500mb flow develops. Rex block associated with the western ridge will likewise weaken and the trapped upper system will eject northeast towards Oklahoma on Wednesday. Moisture return will start as the system moves across the region. An area of showers and some thunderstorms seems possible across the state with it.
Upper system moves into the western U.S. on Wednesday and progresses eastward into the central U.S. on Thursday. 12z GFS/EC are at odds on how this system will evolve and subsequently translate east. The GFS is weaker with the lead wave, keeping more energy back west while the EC has a more focused trof with two embedded waves. I’m siding with the EC for now, since each solutions offers different sensible weather impacts. Unfortunately this carries into the the weekend, so siding with the wrong model will mess up the forecast beyond Thursday.
Aside from the mid-level pattern differences, the models can be used to derive expected surface conditions on Thursday. Both show moisture return on Thursday in the upper 50s to near 60F range, although the EC has the dryline near I-35 at 7pm Thursday while the GFS is much farther east, owing to the early wave Thursday midday. Temperatures appear to warm nicely across the state and EC develops CAPE values @1800 J/Kg. PW values are in the 0.9 inches range, a little low for severe weather. Something that caught my eye on the 00z EC was the focused shortwave trof and vortmax on Thursday. This could compensate for lack of moisture, although the 12z EC shifted from that solution. Deterministic model windfields are favorable for severe thunderstorms with hail and wind the primary threats. Can’t say I see the other threat at this point and it has been 229 days without one. Thursday appears to be a slight risk and have put probabilities in that area. The fire threat may be more substantial than the severe weather threat as dewpoints plunge post dryline. As noted previously, the GFS would argue for far eastern Oklahoma to get storms. I do not see this as a chase day, although I’m rather interested in finding such a day.
Models do hint at progressive pattern continuing beyond this forecast period. Temperatures do cool post Thursday’s system, but warm steadily through the weekend.
First guess at temperatures per EC/NAM are little off from going NWS numbers. I went lower than NWS on Wednesday since the EC and especially the NAM are much lower. Given the upper system moving through the area, I think the lower numbers are a good bet. Another difference is next Sunday when the EC is very warm, showing upper70s. Since the normal high will be 69F by that time, I went low 70s. Hopefully the EC will be right but certainly not the trend this season.