Recognize & Embrace Uncertainty

RAP BLIPMAP FORECASTS
BLIPMAP™ = Boundary Layer Information Prediction MAP
 [The Boundary Layer (BL) is the region mixed by thermal eddies]
 Created by Dr. John W. (Jack) Glendening, Meteorologist 

BLIPMAPs display thermal soaring parameters over a geographic region.

18Z  SouthEast  Forecasts
20km RAP RESULTS    

Current time  day:                   Forecast Availabily
The "current day" changes shortly after 2Z     Time="---" if none yet available for current day

For RAP BLIPMAP forecasts at validation times other than 18Z and/or overlaying multiple parameters, use the UniViewer OR regional Viewer OR auxiliary BLIP data display software.  Forecasts in 3 hour increments are also available at the regional Multi-Time Index 

For additional on-line information:  BLIPMAP HELP page

NEWS
Blipmap Forum:
 Latest: Fri Nov 6 09:30 "Re: NAM Termination and BLIPMAP Future" [Ron Schwartz]

DrJack sez:
  (Latest 5 news items) April 20, 2026 update:  Univiewer MiniBlipspot previous day problem fixed
November 5, 2026: 
NAM Termination and BLIPMAP Future
   The U.S. National Weather Service has stopped running its NAM model, so no new NAM BLIPMAP forecasts will be created.  The RAP forecasts will continue, but they are limited to current day forecasts. 
   I'd seen an announcement that NWS intended to retire the NAM in August - but that date came and went, then a subsequent intended termination date of September came and went, then similarly for October - but finally in November the termination is reality. 
   Given that warning, I'd intended on the death of NAM to post an announcement offering to transfer the site, forecasts, etc. to anyone willing to take them over with the intent of updating to replace NAM with the more recent "Rapid Refresh Forecast System" (RRFS) model with its improved resolution - else would terminate the BLIPMAP forecasts in the spring, since NAM model more important than RAP due to its forecasts out to two days instead of just current day. 
   BUT just before that date Kurt Thams, who has seen the same announcements of NAM demise, on his own initiative contacted me and offered to work on transferring the newer NOAA model and keep the legacy going.  So I will be working with him on that.  Given his experience both in computer systems and in soaring, I think that the forecasts will be in good hands. 
   So watch this page for further info.  Kurt tells me he is actively working on getting the system revised to work with NOAA's newer model.  If anyone wants to get involved they can reach him by email by using his last name combined with circled-at-symbol with his last name and dot-com =
    In the interim, I have disabled the contributions link until I can be assured of the BLIPMAP future. 
Jack

February 24, 2026:  Server Costs: 
    Yearly Expenses:  website ~$600 + registration ~$100 = $700 / year
    Yearly Income:  2025: $210
 

REGISTRATION:
All BLIPMAPs are now freely available to registered users.  Registration (free) is needed for direct (no-nag-screen) forecast access.  New users can Register here.  Currently registered users can Logon (get new cookie) here or view registration (cookie) status here.  More info is available at the Registration Information webpage. 
EMAIL POLICY: 
There are many advantages to having one person's knowledge be shared and available to others, so I expect most BLIPMAP issues to be handled through the Blipmap Forum and ask those who have a question or problem or experience which could be of interest to others to post it there.  This allows others to comment on the matter if they have any personal experience and also allows any response I make to be read by others.  If you send me an email, I will respond personally only if it's nature is not appropriate for such posting - in other cases I will simply reply with a request to post to the forum. 
FEEDBACK REQUEST: 
I only look at the webpages and maps that I use personally or that I suspect might contain an error.  If you notice a consistent problem with either, please post a message on the Blipmap Forum.
 

BLIPMAP SERVER FUND STATUS
February 24, 2026:  $1624
(to be be updated ~yearly)



FORECASTS
THERMAL PARAMETER FORECASTS:
COMPOSITE: Thermal Updraft Velocity & Buoyancy/Shear Ratio          
      "Classic" Coloring:       Latest      FirstToday      PreviousDay     
      Fixed Coloring:       Latest      FirstToday      PreviousDay     
B/S Ratio stippling (dense=0-4 sparse=4-7) overlays Thermal Updraft Velocity contours to indicate where strong thermals can be broken by vertical wind shear.  See "Thermal Updraft Velocity" and "Buoyancy/Shear Ratio" parameter descriptions below for more information. 

Thermal Updraft Velocity (W*)          
      "Classic" Coloring:       Latest      FirstToday      PreviousDay
      Fixed Coloring:       Latest      FirstToday      PreviousDay
Average dry thermal updraft strength near mid-BL height.  Subtract glider descent rate to get average vario reading for cloudless thermals.  Thermal strengths will be stronger if convective clouds are present.  W* depends upon both the BL depth and the surface heating.  MoreInfo

Buoyancy/Shear Ratio (B/S)          
      "Classic" Coloring:       Latest      FirstToday      PreviousDay
      Fixed Coloring:       Latest      FirstToday      PreviousDay
Dry thermals may be broken up by vertical wind shear (i.e. wind changing with height) and unworkable if B/S ratio is 5 or less.  If convective clouds are present, the actual B/S ratio will be larger than calculated here.  [This parameter is truncated at 20 for plotting.]   MoreInfo

Height of Boundary Layer Top (TI=0 height)     
      "Classic" Coloring:       Latest      FirstToday      PreviousDay
      Fixed Coloring:       Latest      FirstToday      PreviousDay
Height of the average dry thermal tops, or Thermal Index TI=0 height.  Over flat terrain maximum thermalling heights will be lower due to the glider descent rate and other factors.  However, thermal tops will be higher over small-scale topography not resolved by the model and some pilots have reported that in elevated terrain the heights they can reach over local terrain features correspond better with the TI=0 height than with Hcrit.  In the presence of clouds the thermal top will increase, but the maximum thermalling height will then be limited by the cloud base (see the "Cloud prediction parameters" section below).  [This parameter is truncated at 22,000 for plotting.]   MoreInfo

Height of Critical Updraft Strength (Hcrit)     
      "Classic" Coloring:       Latest      FirstToday      PreviousDay
      Fixed Coloring:       Latest      FirstToday      PreviousDay
This parameter estimates the height at which the average dry updraft strength drops below 225 fpm and over flat terrain is expected to give better quantitative numbers for the maximum cloudless thermalling height than is the traditional TI=0 height given above, although the qualitative patterns should be similar for both parameters.  (Note: the present assumptions tend to underpredict the max. thermalling height.) In the presence of clouds the maximum thermalling height may instead be limited by the cloud base (see the "Cloud prediction parameters" section below).  [This parameter is truncated at 22,000 for plotting.]   MoreInfo

Thermal Height Variability     
      "Classic" Coloring:       Latest      FirstToday      PreviousDay
      Fixed Coloring:       Latest      FirstToday      PreviousDay
This parameter estimates the variability (uncertainty) of the BL top (TI=0) height prediction which can result from meteorological variations.  Larger values indicate greater variability and thus better thermalling over local "hot spots" or small-scale topography not resolved by the model.  But larger values also indicate greater sensitivity to error in the predicted surface temperature, so actual conditions have a greater likelihood of differing from those predicted.  MoreInfo


WIND PARAMETER FORECASTS:
COMPOSITE: Wind Speed and Direction in the Boundary Layer     
      "Classic" Coloring:       Latest      FirstToday      PreviousDay     
      Fixed Coloring:       Latest      FirstToday      PreviousDay     
BL Wind Direction streamlines overlay BL Wind Speed contours,  See "Wind Speed in the Boundary Layer" and "Wind Direction in the Boundary Layer" parameter descriptions below for more information. 

Wind Speed in the Boundary Layer     
      "Classic" Coloring:       Latest      FirstToday      PreviousDay
      Fixed Coloring:       Latest      FirstToday      PreviousDay
The speed of the vector-averaged wind in the BL.  This prediction can be misleading if there is a large change in wind direction through the BL (for a complex wind profile, any single number is not an adequate descriptor!).  MoreInfo

Wind Direction in the Boundary Layer     
      "Classic" Coloring:       Latest      FirstToday      PreviousDay
      Fixed Coloring:       Latest      FirstToday      PreviousDay
The direction of the vector-averaged wind in the BL.  This prediction can be misleading if there is a large change in wind direction through the BL (for a complex wind profile, any single number is not an adequate descriptor!).  Note that there will be a abrupt artificial gradient at the "cross-over" between 0 and 360 degrees.  MoreInfo

Wind Shear in the Boundary Layer     
      "Classic" Coloring:       Latest      FirstToday      PreviousDay
      Fixed Coloring:       Latest      FirstToday      PreviousDay
The magnitude of the vector wind difference between the top and bottom of the BL.  Note that this represents vertical wind shear and does not indicate "shear lines" (which are horizontal changes of wind speed/direction).  MoreInfo

BL Max. Up/Down Motion (BL Convergence)     
      "Classic" Coloring:       Latest      FirstToday      PreviousDay
      Fixed Coloring:       Latest      FirstToday      PreviousDay
Maximum grid-area-averaged extensive upward or downward motion within the BL as created by horizontal wind convergence.  Positive convergence is associated with local small-scale convergence lines (often called "shear lines" by pilots, meaning horizontal changes of wind speed/direction) - however, the actual size of such features is much smaller than can be resolved by the model so only stronger ones will be forecast and their predictions are subject to much error.  If CAPE is also large, thunderstorms can be triggered.  Negative convergence (divergence) produces subsiding vertical motion, creating low-level inversions which limit thermalling heights.  This parameter can be noisy, so users should be wary.  MoreInfo


CLOUD PARAMETER FORECASTS:
COMPOSITE: Cumulus Cloudbase for Cu Potential > 0     
      "Classic" Coloring:       Latest      FirstToday      PreviousDay     
      Fixed Coloring:       Latest      FirstToday      PreviousDay     
Cu Cloudbase Cloudbase contours are plotted only where that cloudbase is theoretically expected.  See "Cumulus Potential" and "Cumulus Cloudbase" parameter descriptions below for more information.  This composite is useful only for locations where the actual potential threshold for cumulus cloud production agrees with the theoretically-predicted value of zero.

COMPOSITE: OvercastDevelopment Cloudbase for OD Potential > 0     
      "Classic" Coloring:       Latest      FirstToday      PreviousDay     
      Fixed Coloring:       Latest      FirstToday      PreviousDay     
OvercastDevelopment Cloudbase Cloudbase contours are plotted only where that cloudbase is theoretically expected.  See "OvercastDevelopment Potential" and "OvercastDevelopment Cloudbase" parameter descriptions below for more information.  This composite is useful only for locations where the actual potential threshold for OD cloud production agrees with the theoretically-predicted value of zero.

Cumulus Potential     
      "Classic" Coloring:       Latest      FirstToday      PreviousDay
      Fixed Coloring:       Latest      FirstToday      PreviousDay
This evaluates the potential for small, non-extensive "puffy cloud" formation in the BL, being the height difference between the surface-based LCL (see below) and the BL top.  Small cumulus clouds are (simply) predicted when the parameter positive, but it is quite possible that the threshold value is actually greater than zero for your location so empirical evaluation is advised.  I would be interested in receiving end-of-season reports on what threshold value worked for your site.  Clouds can also occur with negative values if the air is lifted up the indicated vertical distance by flow up a small-scale ridge not resolved by the model's smoothed topography.  [This parameter is truncated at -10,000 for plotting.]   MoreInfo

Cumulus Cloudbase (Sfc. LCL)     
      "Classic" Coloring:       Latest      FirstToday      PreviousDay
      Fixed Coloring:       Latest      FirstToday      PreviousDay
This height estimates the cloudbase for small, non-extensive "puffy" clouds in the BL, if such exist i.e. if the Cumulus Potential parameter (above) is positive or greater than the threshold Cumulus Potential empirically determined for your site.  The surface LCL (Lifting Condensation Level) is the level to which humid air must ascend before it cools enough to reach a dew point temperature based on the surface mixing ratio and is therefore relevant only to small clouds - unlike the below BL-based CL which uses a BL-averaged humidity.  However, this parameter has a theoretical difficulty (see "MoreInfo" link below) and quite possibly that the actual cloudbase will be higher than given here - so perhaps this should be considered a minimum possible cloudbase.  I would be interested in receiving end-of-season reports on how well this parameter worked for your site.  [This parameter is truncated at 22,000 for plotting.]   MoreInfo

OvercastDevelopment Potential     
      "Classic" Coloring:       Latest      FirstToday      PreviousDay
      Fixed Coloring:       Latest      FirstToday      PreviousDay
This evaluates the potential for extensive cloud formation (OvercastDevelopment) at the BL top, being the height difference between the BL CL (see below) and the BL top.  Extensive clouds and likely OvercastDevelopment are predicted when the parameter is positive, with OvercastDevelopment being increasingly more likely with higher positive values.  OvercastDevelopment can also occur with negative values if the air is lifted up the indicated vertical distance by flow up a small-scale ridge not resolved by the model's smoothed topography.  [This parameter is truncated at -10,000 for plotting.]   MoreInfo

OvercastDevelopment Cloudbase (BL CL)     
      "Classic" Coloring:       Latest      FirstToday      PreviousDay
      Fixed Coloring:       Latest      FirstToday      PreviousDay
This height estimates the cloudbase for extensive BL clouds (OvercastDevelopment), if such exist, i.e. if the OvercastDevelopment Potential parameter (above) is positive.  The BL CL (Condensation Level) is based upon the humidity averaged through the BL and is therefore relevant only to extensive clouds (OvercastDevelopment) - unlike the above surface-based LCL which uses a surface humidity.  [This parameter is truncated at 22,000 for plotting.]   MoreInfo

BL Max. Relative Humidity     
      "Classic" Coloring:       Latest      FirstToday      PreviousDay
      Fixed Coloring:       Latest      FirstToday      PreviousDay
This parameter provides an additional means of evaluating the formation of clouds within the BL and might be used either in conjunction with or instead of the other cloud prediction parameters.  Larger values indicate greater cloud probability, but use of this parameter must be empirical since no theoretical guidance is available - for example, pilots must determine by actual experience the percentage that correlates with formation of clouds above local mountains.  The cloud base height is not predicted, but is expected to be below the TI=0 height.  MoreInfo

CAPE     
      "Classic" Coloring:       Latest      FirstToday      PreviousDay
      Fixed Coloring:       Latest      FirstToday      PreviousDay
Convective Available Potential Energy indicates the atmospheric stability affecting deep convective cloud formation above the BL.  A higher value indicates greater potential instability, larger updraft velocities within deep convective clouds, and greater potential for thunderstorm development (since a trigger is needed to release that potential).  Note that thunderstorms may develop in regions of high CAPE and then get transported downwind to regions of lower CAPE.  Also, locations where both convergence and CAPE values are high can be subject to explosive thunderstorm development.   MoreInfo

Surface Dew Point Temperature     
      "Classic" Coloring:       Latest      FirstToday      PreviousDay
      Fixed Coloring:       CurrentDay      Current+1      PreviousDay
This model-predicted surface dew point temperature can be compared to the actual dew point temperature at 2m during the day to evaluate the accuracy of model moisture predictions.  MoreInfo


FUNDAMENTAL BL PARAMETER FORECASTS:
Boundary Layer Depth     
      "Classic" Coloring:       Latest      FirstToday      PreviousDay
      Fixed Coloring:       Latest      FirstToday      PreviousDay
Depth of the layer mixed by thermals.  This parameter can be useful in determining which flight direction allows better thermalling conditions when average surface elevations vary greatly in differing directions.  MoreInfo

Surface Heating     
      "Classic" Coloring:       Latest      FirstToday      PreviousDay
      Fixed Coloring:       Latest      FirstToday      PreviousDay
Heat transferred into the atmosphere due to solar heating of the ground, i.e. the heating that creates thermals.   [This parameter is truncated at -100 and +1000 for plotting.]   MoreInfo

Surface Temperature     
      "Classic" Coloring:       Latest      FirstToday      PreviousDay
      Fixed Coloring:       CurrentDay      Current+1      PreviousDay
This model-predicted surface temperature can be compared to the actual temperature at 2m during the day to evaluate the accuracy of model heating predictions.  MoreInfo

Experimental     
      "Classic" Coloring:       Latest      FirstToday      PreviousDay
      Fixed Coloring:       Latest      FirstToday      PreviousDay
The parameter displayed here varies, often being one used for testing.  See news items for reports of experimental parameter changes. 

Experimental2     
      "Classic" Coloring:       Latest      FirstToday      PreviousDay
      Fixed Coloring:       Latest      FirstToday      PreviousDay
The parameter displayed here varies, often being one used for testing.  See news items for reports of experimental parameter changes. 


MISCELLANEOUS:
Maps
Geographic Map
Actual Terrain Map
Model Terrain Map
Model Terrain Map - alternate colors


OTHER METEOROLOGICAL FORECASTS from RAP model:
Sounding profiles from GSD interactive sounding webpage
Link to webpage generating temperature, humidity, and wind profiles on a skew-T plot.  Interactive capability provides additional functions (if your browser has java available).



INFORMATION
FORECAST DESCRIPTION:

    BLIPMAPs predict thermal soaring conditions resulting from surface heating of the Boundary Layer (BL), the scientific term for the turbulent atmospheric region mixed by surface-based thermals (so thermal tops occur at the top of the BL).  The BLIPMAP program post-processes numerical weather model predictions to provide parameters suited to the needs of soaring pilots and presents them in graphical format, as in this sample BLIPMAP.  Relative differences, both in location and in time, are expected to be more reliable indicators of soaring differences than are the precise numerical values.  BASIC thermal forecast parameters gives a short list of the parameters most important for thermal soaring.
    A sequence of forecasts, all for the same validation time of 18Z, is produced during the day as new observational data becomes available, each updated forecast having a shorter forecast period between the latest observation and validation times.  [Model initialization (observation analysis) time + Forecast Period = Validation (forecast) time]  The most important link is the first link on each line, "Latest", which gives the most recent (shortest period) forecast. The following "FirstToday" link gives the first forecast from the current day, which can be used to determine whether the model is significantly altering its predictions during the updating.  The last link, "PreviousDay", gives the last forecast from the previous day's prediction sequence, useful for those who want to compare their experiences from yesterday's flight to the RAP BLIPMAP predictions.  At the top of each forecast plot is the name of the parameter, the validation date and time, the forecast period, and the data source. 
    The parameters are averages over 20km grid squares as forecast by NOAA's Forecast Systems Laboratory RAP model as run operationally by NOAA's NCEP (National Centers for Environmental Prediction).  RAP BLIPMAPs are updated as new RAP forecasts become available, normally at 3 hr intervals. 
    The parameter values are represented by color hues which increase in "warmness" as the value increases in magnitude.  When many gradations are required, two cycles are made through the color wheel with "light" and "intense" tints respectively representing ranges of lower and higher magnitude. A screen magnifying tool, such as the freeware Super Magnify for Windows machines or Xzoom for X11/Linux/Unix machines, helps when discrimination between adjacent contours is difficult.  Alternatively, the size of an image can be increased/decreased by many browsers (Firefox users can install the Image Zoom plug-in extension to add that capability). 
    State outlines are depicted on each BLIPMAP in white.  The RAP topography is plotted as black contours, at 500 ft intervals with thicker lines at 2000 ft intervals, to assist in location identification but also to emphasize the smoothed nature of the model topography.  The BLIPMAP does not predict thermal lift created by small-scale terrain features which are not resolved by the model topography, which often give localized updrafts significantly stronger than those over the surrounding smoother terrain.  Maps of location identifiers and additional topography information for this region are available at the SE Grid Orientation webpage.
    RAP BLIPMAPs can also be viewed using a regional BLIPMAP Viewer or a UniViewer - both can create a BLIPMAP image sequence. The viewers are most useful for quickly cycling between or through BLIPMAPs since the images exactly overlie - and some consider them easir to use than this index page.  The viewers can automatically alter the image size on loading, as might be desired by those with smaller screens for example.  Alternate graphical display formats are also available using BLIP data display software. 

Notes:
    As with all weather products, users should check the date on each map for currency.  Small anomalous diamonds, the size of an individual model gridpoint, may appear in the plots, particularly for more sensitive parameters such as convergence or cloud parameters; these result from numerical noise and should be disregarded.

Medal     Heros: I personally thank those whose support is listed on the Contributors webpage.


Link to the BLIPMAP Viewer for this region
Link to the BLIPMAP UniViewer
Links to the identified location map for this region and to its key
Links to the BLIPMAP Archive Viewer and RAP Archive Viewer with IGC overlay
BLIPMAP HELP webpage - for additional on-line information

Link to the latest BLIPSPOT forecasts for individual locations
Link to the BLIPMAPs for all regions
Link to the latest TIP forecasts for longer predictions at individual CA-NV locations
Link to the latest Upper-Air WINDIP forecasts for CA-NV
Link to the latest LWIP fine-scale wave forecasts for Lake Tahoe and Owens Valley regions

Link to the Registration Information webpage
Link to the Subscription Information webpage
Link to the Registration/Subscription Logon webpage (new window)
Link to DrJack's home page