- Surface Conditions
__2-m Temperature / 10-m Wind__- Ens Mean | Ens Max | Ens Min | Ens Spread | Postage Stamps
- Ens Mean Sfc T Anomaly | Prob Sfc T < 32 F
__2-m Dewpoint / 10-m Wind__- Ens Mean | Ens Max | Ens Min | Ens Spread | Postage Stamps
- Ens Mean Sfc Td Anomaly
__Misc.__- Ens Mean: Heat Index | Wind Chill | PBL Height | 2-m RH
- Prob Visibility: < 3 mi | < 1 mi | < 0.25 mi
- Ens Spread: Mean Sea-level Pressure
- Postage Stamps: Equivalent Potential Temp. | 10-m wind
- Ensemble Plumes Page
- Precipitation
__1-hr Precip__- Prob Matched Mean | Ensemble Max
- Neighbor Prob: > 0.01 in | > 0.25 in | > 0.5 in | > 1.0 in | > 2.0 in
__6-hr Precip__- Ens Mean | Ensemble Max | Ensemble Min
__24-hr Precip__- Ens Mean | Ensemble Max | Ensemble Min
__Accum. Precip__- Ens. Mean | Prob Matched Mean | Postage Stamps
- Neighbor Prob: > 1.0 in | > 2.0 in | > 3.0 in | > 6.0 in | > 10.0 in
- Reflectivity
- Ensemble Max: Comp Refl | 1 km AGL Refl
- Prob Match Mean: Comp Refl | 1 km AGL Refl
- Neighborhood Prob > 40 dBZ: Comp Refl | 1 km AGL Refl
- Paintball > 40 dBZ: Comp Refl | 1 km AGL Refl
- Postage Stamps: Comp Refl | 1 km AGL Refl
- Member Viewer: Comp Refl & UH

- Ensemble Mean Fields
- Wind/Height: 250 mb | 300 mb | 500 mb | 700 mb | 850 mb | 925 mb
- Temperature: 250 mb | 300 mb | 500 mb | 700 mb | 850 mb | 925 mb
- Relative Humidity: 700 mb | 850 mb | 925 mb
- Dewpoint: 850 mb | 925 mb
- Absolute Vorticity: 500mb
- Potential Vorticity: 320K PV
- Ensemble Spread Fields
- Height: 250 mb | 300 mb | 500 mb | 700 mb | 850 mb | 925 mb
- Wind Speed: 250 mb | 300 mb | 500 mb | 700 mb | 850 mb | 925 mb
- Temperature: 250 mb | 300 mb | 500 mb | 700 mb | 850 mb | 925 mb
- Dewpoint: 700 mb | 850 mb | 925 mb
- Probabilities
- Prob: 850 mb temperature < 0 C | 925 mb temperature < 0 C
- Precipitable water
- Ens mean | Postage stamps
- Simulated Satellite
- Member 1: Water Vapor | IR
- Postage Stamps: Water Vapor | IR
- Ensemble Soundings
- Ensemble Sounding Viewer

- Instability
- Ens Mean: SBCAPE | MLCAPE | MUCAPE | Lifted Index
- Ens Max: SBCAPE | MLCAPE
- Prob SBCAPE: > 500 | > 1000 | > 2000 | > 3000
- Prob MLCAPE: > 500 | > 1000 | > 2000 | > 3000
- Postage Stamps: SBCAPE
- LCL / LFC / BMIN / STP/ Echo tops
- Ens Mean: LCL Height | LFC Height | Parcel BMin
- Sig Tor Parameter (STP): Max | Mean | NEProb > 1 | NEProb > 3
- Echo tops: Max | Mean | Prob matched mean
- Neighborhood prob echo tops: > 30,000 ft | > 35,000 ft
- Wind shear
- Ens Mean: 0-1 km | 0-6 km
- Ens Max: 0-1 km | 0-6 km
- Storm-relative Helicity / Storm motion
- Ens Mean: 0-1 km | 0-3 km
- Ens Max: 0-1 km | 0-3 km
- Prob 0-1 km SRH: > 100 | > 300
- Prob 0-3 km SRH: > 200 | > 450
- Ens Mean: Bunkers Storm Motion

- Winter Precip
__1-hr Accumulation__- Dominant 1-hr Precipitation Type
- 1-hr Probability of Winter Precip
- Snow: Ens Mean | Prob Match Mean | Stamp
- Snow Neighbor Probs: > 1" | > 2" | > 3"
- Freezing Rain: Ens Mean | Prob Match Mean | Stamp
__6-hr Accumulation__- Snow: Ens mean | Ens max
- Freezing rain: Ens mean | Ens max
__12-hr Accumulation__- Snow: Ens mean | Ens max
- Freezing rain: Ens mean | Ens max
__24-hr Accumulation__- Snow: Ens mean | Ens max
- Freezing rain: Ens mean | Ens max
__Running total accumulation__- Snow: Ens mean | Prob Match Mean | Stamp
- Snow Neighbor Probs: > 1" | > 3" | > 6" | > 12" | > 24"
- Snow grid-point Probs: > 1" | > 3" | > 6" | > 12" | > 24"
- Freezing rain: Ens mean | Prob Match Mean
- Sleet: Ens mean | Prob Match Mean

- Hourly-max Rotation
- Ens Max: 2-5 km AGL UH | 0-3 km AGL UH
**(cyclonic)** - Ens Max: 2-5 km AGL UH
**(anticyclonic)** - Ens Max: 1km AGL Vorticity
- Paintball: UH > 50 | UH > 75 | UH > 100 | UH > 150
- Neighbor Prob: UH > 50 | UH > 75 | UH > 100 | UH > 150
- Hourly-max Updraft
- Ensemble Max Updraft
- Paintball: UP > 10 m/s | UP > 20 m/s
- Neighbor Prob: UP > 10 m/s | UP > 20 m/s
- Hourly-max Downdraft
- Ensemble Max Downdraft
- Paintball: DN > 5 m/s | DN > 10 m/s
- Neighbor Prob: DN > 5 m/s | DN > 10 m/s
- Hourly-max 10-m Wind Speed
- Ensemble Max Wind Speed
- Paintball: WS > 10 m/s | > 20 m/s | > 30 m/s
- Neighbor Prob: WS > 10 m/s | > 20 m/s | > 30 m/s
- Hourly-max Vert. Int. Graupel & Hail Size
- Ens Max: Graupel | Thomp. Hail | Hailcast | Gagne Hail
- Paintball >= 1 in: Graupel | Thomp. Hail | Gagne Hail
- Neighbor Prob >= 1 in: Graupel | Thomp. Hail | Gagne Hail
- Hourly-max Lightning Threat
- Ens Max: Ltg 1 | Ltg 2 | Ltg 3
- Lightning probability: Ltg 3 > 1 flash per 5 minutes
- Day 1 and 2 Severe Weather Probs

Frequently Asked Questions

close all

- How much computational resources are required to run the analysis and forecasting system?
- The forecast system requires 5120 cores on NCAR's Yellowstone supercomputer for approximately 4-hrs.
- Do we plan to produce 12Z initialized ensemble forecasts?
- We are exploring the possibility of initializing 12Z forecasts during Spring 2016, given the availability of additional computing time.
- Are the data freely available for use to external collaborators?
- Yes, subject to UCAR's terms and conditions. Send us an email.
- What is parcel Bmin?
- Bmin represents the buoyancy minimum experienced by an air parcel lifted from a specified height. The graphics on this site use an air parcel lifted from the surface. More information on its development and utility can be found in Trier et al. (2014).
- How are the simulated satellite products created?
- The simulated satellite product is derived from the Community Radiative Transfer Model (CRTM) embedded inside the UPP.
- How is precipitation type determined?
- Precipitation type is computed using the AFWA precipitation type diagnostics package in WRFV3.6.1. The full documentation for this package can be found here. Precipitation type is determined independently from the microphysics scheme using a top-down approach as summarized below:

For each vertical grid column, do the following:- Modify the 2-m temperature by adding the shortwave radiation (W m-2) divided by 100.
- If the modified 2-meter temperature is > 2C, set type to rain.
- Check the vertical profile to find highest cloud temperature (RH < 80%). If a cloud is found, but below it a dry (RH < 70%) layer is found, reset and keep checking.
- If the cloud top temperature is < -9C, set type to snow. Otherwise, set to rain.
- Check the vertical profile that the rain or snow is falling through:
- If snow or ice pellets falls through a melting layer, integrate total melting energy.
- If the integrated energy is > 50 J kg-1, then set type to rain.
- If the integrated energy is between 25-100% of 50 J kg-1, and it subsequently falls through a sub-freezing layer, assume it partially melted and then re- froze into an ice pellet. Reset melting energy to zero.
- If as rain falls it encounters a temperature < -9C, set type to ice pellets.
- Keep running these checks all the way to the ground and adjust types accordingly.
- Once it gets to the ground, rain becomes freezing rain if the modified 2 meter temperature is < 0C.

This produces a snowfall ratio of 10:1 near 0C, 15:1 near -11C, and 20:1 near -27C. This is an obvious simplification, as snow crystals form above the surface in a potentially different thermodynamic environment. In cases where temperatures in the snow growth region are between -12C and -18C, snowfall ratios could easily exceed 20:1. Keep this in mind when examining the snowfall accumulation graphics on this site.

This algorithm tends to produce freezing rain immediately downwind of high terrain, when the actual precipitation type is likely to be snow. This is due to the way in which the highest cloud temperature is determined as described above. We will be investigating this issue during the winter of 2015-2016. - How are the 24-hour smoothed severe weather probabilities produced?
- The severe weather probabilities are produced following a method described in Schwartz et al. (2015), which is based on a method proposed by Sobash et al. (2011). Briefly, the probabilities use diagnostic fields that represent the intensity and behavior of convection to identify locations where severe weather may occur, by selecting thresholds that approximately match the frequency thresholds for observed severe weather. These locations are smoothed to account for location and timing errors to produce a 24-hour severe weather guidance product.
- Where can I find more information about the model configuration?
- Some aspects of the model configuration is documented on our "About" page. Additional documentation is provided in Schwartz et al. (2015).