NCBlizzard

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    Durham, NC

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  1. I’m at 31.3 with a wet bulb of 30.2 in South Durham, right at I-40. A solid glaze on elevated surfaces/trees (maybe 0.05”), but sidewalks and roads are just wet. I’m surprised we got this cold here based on trends late last night. At 9 AM, my station was 2.2°F colder than the NAM and 1.4°F colder than the HRRR projected. Some more light precip moving in now so we’ll see if those trends mean anything at this point. Oddly enough, GFS/RDPS have been the most accurate on temps so far.
  2. I agree it definitely runs colder, and sometimes by a lot. At the very least, it seems to run 2-4°F too cold on average. RGEM forecast low for tonight here is 15, which is 6 degrees cooler than the NWS forecast and around 10 degrees cooler than all other models except the Canadian. I have a hard time believing we get to 15 here, but we shall see…
  3. Yep - I figured that would be the case too, which makes the reality easier to deal with. Gotta love the Triangle haha. Just an extra 30 minutes of snow with the initial rates would have made a huge difference. It was challenging to track the transition on radar. Correlation coefficient was pretty useless since it was all snow up where the radar beam was 2+ hours ahead of a transition at the surface.
  4. Ended up with about 1.4” here 7 miles south of Downtown Durham, near Southpoint Mall. Transition didn’t fully happen until a little after 2AM. NAM better modeled the timing of that than the HRRR here. HRRR was better on surface temperatures though and was really the only one besides the RDPS (and NWS National Blend of Models) showing it making below freezing. The NAM was 2°F or so too warm on surface temperatures. The band that came through 2:45-3:30 AM or so meant business - easily was 2-3” /hr rates. You could tell all the snow was melting from the ground up throughout the event, but those heavier rates easily overcame. 4” soil temperature here was 47.5°F going into the event and is now still only 42°F, although all the snow is basically gone now. Ended up being exactly what I expected here, and certainly nice to see some snow!
  5. A little over 1" 7 miles south of downtown durham. Temp is down to 31.6. Massive flakes earlier for a solid hour. Snowfall rate has gone down slightly. Still accumulating but now mainly just on elevated and grassy surfaces
  6. Turned all snow in South durham roughly 15 minutes ago. Elevated surfaces getting covered. Temp is down to 33.1 and dropping steadily
  7. Decided to throw together a call map. One of the toughest areas to nail down is basically I-40 in Orange through Wake County and points southwest since sleet may cut into totals and even a slightly delayed transition can really make a difference. Here’s hoping for the best!
  8. Yep, been stuck in that hole for a while here in south Durham. I noticed it on the HRRR but hoped it was a fluke. Overall, had a brief rain/snow/sleet mix early this morning 5-6 am, leaving a trace on elevated surfaces. Then a rain/snow mix since 7:30. I didn't have my hopes too high overall though. And you're right about the Triangle being really lucky the past several years. Can't complain much at all given that.
  9. Transitioned from a mix to all rain in south Durham (near Southpoint mall for those familiar) an hour or so ago. 34.9 currently, which is about 1-2°F cooler than the NAM/HRRR forecast for 8AM.
  10. Rain/snow/sleet mix in South Durham. Temperature has dropped to 36.7.
  11. While every model was too warm with dew point/wet bulb temperature here at my place in Durham, still just a cold 33° rain. Below is the forecast dew point error for 9 AM compared against the 32.7°F recorded at my station: HRRR +0.8° GFS +1.1° RGEM +2.2° NWS NDFD +2.3° NAM +2.3°
  12. I'm near Southpoint Mall and all snow. It's really coming down. My station is reading 34 and wet bulb is almost to 32 Sent from my SM-G975U using Tapatalk
  13. I noticed as well, and the same is happening at my house with the dewpoint dropping at -2.8°/hr now. There seems to be a stretch of locally higher DP through parts of S Orange, S Durham, and W Wake county but hopefully that disappears quickly. NAM dewpoint forecast was about a degree higher at 8AM that what I measured with my station.
  14. For my house in S. Durham, the NAM is way warmer than the current air temperature, with GFS/HRRR being the best right now.
  15. There is a snow melt forecast variable, which I assume accounts for things like ground/air temperature, and that would be incorporated to calculate the snow depth. I also believe it accounts for snow density/compaction. I'm not sure of the overall accuracy. You can see all of the forecast variables here: https://www.nco.ncep.noaa.gov/pmb/products/nam/nam.t00z.bgrdsf00.tm00.shtml