Update history for SPC HREF Ensemble Viewer


  1. New products: time-min updraft helicity. Ensemble minimum and neighborhood probability of magnitude threshold exceedance are plotted. Note that all HREF members now display time-min UH (from mid-June 2019 onward).
  2. New products: combined time-max/min updraft helicity products. Ensemble min and max are plotted together with separate color tables. Neighborhood probabilities are calculated for exceeding magnitude thresholds that are different for time-max vs. time-min (thresholds for max are currently larger than min by a factor of 2.14 based on preliminary hail verification statistics; small changes are possible in the future).
  3. New product: precipitable water (PW) mean and threshold exceedance probabilities.
  4. New product: maximum wind gust (ensemble min/mean/max).
  5. New product: combined probabilities of high wind and low visibility coinciding with snow to highlight blizzard potential.
  6. Ensemble mean storm motion vector overlay available for PW products and calibrated thunder guidance.
  7. Ensemble max reflectivity overlay available for PW products.
  8. Color table for 10-m AGL wind speed extended downward to shade values as low as 10 mph.
  9. New GIS underlay: terrain.


  1. Add two new ensemble members: HRRR and HRRR -6h.
  2. Extend HREF forecasts to 48-h lead time (some members drop out late in forecast; see "HREF members" link on right menu for details).
  3. New product: member viewer for composite reflectivity with 4-h max and min 2-5 km UH tracks. Minimum UH is unavailable on NAM Nest and HRW NMMB members as of March 2019, but may be added soon.
  4. New products: freezing rain QPF and FRAM-based accretion estimate.
  5. New product: ensemble mean cloud cover for low-, mid-, and high-level clouds.
  6. Several additional thresholds added for (2-m RH, 10-m hourly max wind) combined probabilities.
  7. Ensemble max 2-5 km UH contours available as overlay on some environmental fields (e.g., CAPE).
  8. Introduce new UI to toggle between SPC outlook overlay products and issuance times. All D1 and D2 convective and fire outlooks now available.
  9. NWS TOR/SVR warnings available as verification for 4-h and 24-h products.
  10. Replace rollover buttons for forecast times with slider bar.
  11. "Other Overlays" (GIS, SPC Outlooks, Verification) toggled on by user remain active after new page load.
  12. Some fields reorganized into member-viewer style UI: multiple exceedance probability thresholds combined into "threshold probs" suites (QPF, snowfall, SBCAPE, etc.), plus ensemble min/mean/max suites added for SBCAPE, 2-m RH, and 10-m hourly max wind.


  1. New products: rolling 4-h windows for many time-maximum field products (updraft helicity, updraft, 10-m AGL wind speed, and reflectivity). The rolling 4-h windows replace the sequence of 3-h windows previously plotted.
  2. New products: Fixed-Layer STP mean, P[>1], and P[>3]. Fixed Layer STP formulation is from Gallo et al. (2018).
  3. New products: QPF gridpoint probability for 1-h P[>1"]; 6-h P[>1"]; 6-h P[>2"]; and 6-h P[>3"].
  4. New product: updraft helicity member viewer. Some fields on this product are currently unavailable for NAM Nest and HRW NMMB members, but will be included in the future.
  5. Add 700-500 mb lapse rate (contours, transparent fill) as optional overlay for 700 mb product.
  6. Add surface based CAPE (contours) as optional overlay for 0-1 km and 0-3 km SRH products.
  7. Add surface based CIN (contours, hatching) as optional overlay for SBCAPE products.
  8. Add ensemble mean 2-m AGL temperature (contours at 50°F and 60°F) as optional overlays for Fosberg products.
  9. Change color table for 1-h mean snowfall product.
  10. Add hotkeys: J and L for changing forecast times, K and I for changing members in member viewer (existing hotkeys are unchanged).


  1. Initial site launch coinciding with HREFv2 operational implementation.