We have potential for a Prob-Warn exercise this afternoon across the high plains adjacent to the mountains of eastern Wyoming through eastern New Mexico. Thunderstorms are not imminent, however, so to make the most of this shortened week, we will run archive PAR and CASA events between 1830 and 2030 UTC. The forecaster teams will be the same as yesterday, with Kevin and Eric moving over to the CASA desk and Mark and Brad working PAR.

Training on probabilistic warnings will ensue between 2030 and 2200 UTC. We then intend to run Prob-Warn operations in eastern New Mexico from 2200-0200 UTC. Moderate southwesterly upper flow is in place on the far western high plains, while moist southeasterly low-level upslope is increasing. A stalled frontal boundary will begin to lift northward through New Mexico this afternoon, and veering wind profiles north of the front will favor rotation with updrafts initiating in the deep mixing zone along the high terrain. Deep layer shear may actually be stronger up north toward Wyoming…but greater moisture/instablity, and a potentially wider CAPE axis favors operations in northeast New Mexico…where several models, including the short range ensemble, suggest a high probability of thunderstorms. The SPC has outlooked that area with a Slight Risk, including a small 5% tornado contour.

Patrick Burke (EWP Weekly Coordinator, 27-30 May)

Our four forecaster/evaluators (Eric Stevens, Brad Colman, Mark Melsness, and Kevin Brown) arrived at the NWC early this afternoon, and are ready to hit the ground running in this Holiday-shortened week. Today should be our best chance for a central Oklahoma IOP, so we have split the forecasters among PAR and CASA for training on those programs through 3 pm. After checking the weather… we may be able to swap and allow the groups to train on both programs. If weather dictates that operations begin prior to 5 pm, however, we will forego WDSSii Training. Kevin has WDDS experience, and other scientists are available to either drive WDSS or train the other forecaster “on the fly.”

The forecast is for thunderstorms to initiate near the intersection of a cold front and outflow boundary in northwest or west central Oklahoma. Other storms may initiate farther south along the outflow boundary toward southwest Oklahoma and western north Texas. Storms should then move east and southeast toward the PAR and CASA domains, although some southward propagation may occur within the instability axis. The northeastward extent of this activity toward central Oklahoma is somewhat in question…as that area was overturned by an MCS earlier today. At worst…we expect a few severe storms at long range but within the PAR domain. At best…we could have severe storms in both the PAR and CASA domain by early to mid evening. The Shear/CAPE combination is sufficient for rotating storms…and even a tornado threat just east of the outflow boundary…although weak mid level winds may lead to a quick transition toward high precipitation character.

Patrick Burke (EWP Weekly Coordinator, 27-30 May)

SPC has higlighted a MODT Risk of severe storms, with emphasis on long-tracked tornadoes, in their 1630 UTC outlook, across portions of Western KS, and adjacent areas of CO and NE.  A SLGT Risk extends along a progged dryline into Western Oklahoma.  Concerns for the southern target include cap strength and weaker low-level shear.  Plans are to conduct a ProbWarn IOP for the KS area, unless storms develop in Western Oklahoma, where instead we’d conduct PAR operations, since there haven’t been live PAR operations yet this week.

Greg Stumpf (EWP Operations Coordinator)

Today we anticipate operations in an SPC “slight risk” area in NE Colordado / SE Wyoming. The outlook reads:

CONCERNING THE SEVERE POTENTIAL…RUC DATA SHOWS THE STRONGEST VERTICAL SHEAR ACROSS WY AND NE CO WITH 0-6 KM SHEAR VALUES IN THE 40 TO 55 KT RANGE. AS INSTABILITY CONTINUES TO INCREASE…THE SHEAR SHOULD SUPPORT ISOLATED SUPERCELL DEVELOPMENT. STEEP MID-LEVEL LAPSE RATES SHOULD FAVOR A THREAT FOR LARGE HAIL. ALTHOUGH LARGE HAIL WILL BE THE GREATEST THREAT…THE RELATIVELY DRY BOUNDARY LAYER WITH TEMPS IN THE 70S F AND SFC DEWPOINTS IN THE 40S F MAY LOCALLY ENHANCE DOWNDRAFTS FOR A DAMAGING WIND THREAT.

The IOP should begin at 6pm CDT, with PAR and CASA playback cases taking up the bulk of the afternoon.

Travis Smith (EWP Weekly Coordinator, 19-23 May)

There is already a Severe T-Storm Watch box out for N. Carolina/Virginia at briefing time, and it looks like we’ll let the storms mature and have a Prob Warning Guidance IOP beginning at 4pm CDT. This is a good region for SHAVE verification as well, so we will try to coordinate the two projects in order to maximize verification of the PWG grids.

The forecasters will split up and work on PAR and CASA playback cases until then.

Travis Smith (EWP Weekly Coordinator, 19-23 May)

Good day for training! The SPC outlook for today is “See Text”, with a 2% tornado probability over the S. Illinios/Kentucky/Tennessee area and 5% hail probability over three different areas (Upper Midwest/Central Plains/Ohio Valley). There is big 500mb trough in the east with generally NW flow over the risk areas.

Today’s plan(afternoon):

• general orientation / map discussion
• CASA orientation
• PAR orientation
• WDSSII training

In the evening, we will do a Probabilistic Warning Guidance training exercise, in real-time if storms develop, or displaced real-time if not.

Travis Smith (EWP Weekly Coordinator, 19-23 May)

… Not so good.

The system that we worked at the end of 14 May 2008 has translated eastward along the Gulf Coast States and is ongoing at the time of our 1 pm briefing. As the day goes on, the upper level trough that has been the “weather maker” the past day or so, will lift out to the NE. This takes the deeper (0-6km) shear with it, though the ongoing convection has developed an MCV and low-level shear should be good. The atmosphere is not terribly unstable though, so the existing and diminishing threat is most a tornado/wind threat for any convection that survives the day. There is a small spot in S TX that might allow us an IOP, and Dan M. also has suggested MN as an area with non-severe, but “popcorn” thunderstorms that would make for an interesting case to watch. This leaves us with nothing to work in the CASA / PAR domains.

We’ll do the PROBWARN archive case and perhaps another CASA / PAR case. If there is time and weather, we’ll try a realtime IOP later in the day.

Kevin Manross (EWP Weekly Coordinator, 12-16 May)

Quick review of the outlook for 14 May 2008.

Not expecting SVR in the PAR / CASA domain, though there should be some convection. We’ll focus our efforts on PROBWARN due to this, and the fact that we haven’t done a PROBWARN IOP yet this week.

Location will likely be W / C TX where return flow is best.

Kevin Manross (EWP Weekly Coordinator, 12-16 May)

Alrighty – this is our best chance for CASA this week (likely for PAR too), for severe weather. We will probably have convection in the CASA domain tomorrow, but I’d be surprised to have much in the severe category.

We have a front that has sagged into central OK and has recently initiated in Lincoln CO (~2145z). The line looks like it is trying to continue to initiate toward the SW in the CASA network. The boundary appears to be visible in the Ern part of the network.

CAPE values have been progged to be rather extreme (~4000 J/Kg), but the shear is not terribly favorable for significant tornado threat. However, with a boundary colocated with high CAPE, we might have some opportunity for tornadic storms. Nevertheless, shear is sufficient for supercells with large hail.

Kevin Manross (EWP Weekly Coordinator, 12-16 May)

Nothing much to get excited about today. SPC has a slight risk issued for the DRT area based mainly for downstream of “old faithful”. Otherwise, the CONUS is dominated by a mid-continent ridge with an exiting upper-level low off the east coast and a trough digging through nrn NV. This west coast upper trough will be the weather-maker for the week. In fact, this trough is progged to become very positively tilted and progress only slowly eastward.

That being said, it appears that our best bet for *severe* convection in our CASA domain may be late tomorrow afternoon/early evening as a cold front drapes across OK. Therefore, we have performed all the intro seminars this afternoon and this evening, Dave and Dan P. are working through a CASA case. Ron P. and dan M. are working through a PAR training case.

Kevin Manross (EWP Weekly Coordinator, 12-16 May)