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Question: Why was there a winter storm watch on Thursday (1-5-17) even though you guys said it wouldn't snow until Friday night (1-6-17)? I thought watches meant there is a chance of it happening right now; please explain. — Panther

Answer: The lead time for different kinds of watches from the National weather Service varies somewhat with the type of event involved. A severe thunderstorm watch, for example, is usually issued shortly before or right at the beginning of the period in which conditions are favorable for severe storms to develop, in line with your perception of the timing of watches. However, for winter storms that are expected to affect an area, they strive to provide more advance notice that confidence in the occurrence of impactful wintry precipitation has reached a level that justifies highlighting the expected conditions in a watch. Depending on how confident the forecast has become, a winter storm watch may be issued as little as 18 hours before wintry precipitation sets in, or as much as 48 hours. As the storm gets closer and confidence in likely impacts becomes even higher, the watch may be upgraded to a warning.
Jan. 14, 2017 | Tags: maps & codes, preparedness, winter weather

Question: Is it true that each snow flake has a different pattern from any another one? If true, this is mind boggling as billions upon billions of snowflakes fall each year! Does each raindrop have the same basic shape and does each pellet of ice look similar? What is it about snow that reveals this miracle of creation? — Ed Thomas

Answer: On some level, it is impossible to absolutely guarantee that no two snow crystals have ever been at least very nearly the same, since trillions have formed and there is no way to observe more than a tiny fraction of them in detail. However, the manner in which snow crystals grow varies considerably depending on both temperature and relative humidity and since any growing group of snow crystals may move through a variety of surroundings during the time that the crystal grows, a huge variety of combinations become possible, with even slight variations over short distances leading to slightly different structures from one crystal to the next. In many cases, the appearance would be very similar at a glance, but in great detail small differences would become apparent. Small raindrops are almost spherical drops of water, so as long as they are about the same size, many would only be distinguishable on a molecular level. Larger raindrops can oscillate through a variety of shapes due to winds and to drag forces associated with falling through the air, but on average is something along the lines of a hamburger bun, rounded on top and flattened on the bottom. Sleet pellets would be somewhat similar, with small ones tending to be spherical and larger ones less so, but once frozen of course their shapes would not oscillate but remain more or less the same as when the water droplet froze (neglecting any change in shape due to sublimation). In order to keep this answer from getting much longer, we'll refer you to an interesting rumination on the question of uniqueness of snow crystals (incidentally, most snow "flakes" we see falling are collections of multiple snow crystals stuck together) that is available as part of a really nice web site on the subject of snow crystals. You can find the essay and links to all of the site's content at www.its.caltech.edu/~atomic/snowcrystals/alike/alike.htm.
Jan. 13, 2017 | Tags: cool sites, snow

Question: I am putting a roof on a new shed. The instructions say overlap shingles in direction of prevailing winds so the strongest winds cannot catch the shingle overlap. The roof ridge runs north and south. In Raleigh would more strong winds come from the southern direction than the northern? — Mary

Answer: On an overall average basis, wind statistics (as summarized in "wind rose" graphics) show that the Raleigh area has a prevailing southwesterly wind, and that the higher end of routine winds speeds (the 15-25 mph range) come from the southwest, except for a shift to the northeast for September and October. There is also a notable increase in winds from the northwest during the winter months associated with cold air surges in the wake of cold frontal passages. Unfortunately, when it comes to the highest wind gusts, those that are more likely to produce some damage, there is more variability, as thunderstorms can produce intense gusts from any direction (a bit more frequently from the southwest in spring and summer). On the other hand, intense winter post-frontal wind outbreaks usually have a northerly component, while strong gusts associated with nor'easters and with tropical systems usually come from the north or northeast. If your roof ridge ran east-west, we'd probably lean toward recommending an overlap that accounts for strong westerly winds more so than easterly, but given the north-south ridge line, it's a closer call - though we'd probably go with accounting for strong northerly winds. If you're interested in seeing wind roses for Raleigh, you can see them at mesonet.agron.iastate.edu/sites/windrose.phtml?network=NC_ASOS&station=RDU and/or climate.ncsu.edu/windrose.php?state=NC&station=KRDU.
Jan. 12, 2017 | Tags: preparedness, winds

Question: Has it ever snowed for over a straight 24-hour period in central (Wake / Durham) NC? — Russell

Answer: Because of the way weather observations are recorded and archived, especially older ones, it can be hard to absolutely verify the occurrence of completely continuous snowfall. However, we got some kindly assistance from the State Climate Office of NC, who searched observation archives from the Raleigh-Durham airport and found four instances in which every top-of-hour observation there showed snow falling for at least 24 consecutive hours. In order of descending duration, they were: 40 consecutive hours beginning on Jan 15, 1965, at 6 pm (total accumulation of 5.8 inches), 32 consecutive hours beginning on Jan 7, 1973, at 4 pm (total accumulation of 6.4 inches),
25 consecutive hours beginning on Feb 23, 1989, at 4 pm (total accumulation of 4.9 inches), and 24 consecutive hours beginning on Jan 30, 1965, at 5 am (total accumulation of 3.9 inches). We can't guarantee that snow didn't stop and start at some point in between the hourly observation times, but these are nonetheless impressive stretches of snow for our area. One other instance, beginning Jan 2, 2002 at 7 pm, brought 26 consecutive hours with some snow reported, but that one did have a single hourly observation at 8 am on Jan 3 in which sleet was reported at the top of the hour. Earlier in that hour, and again after about a 45-minute period of sleet, snow was reported, for a total of 10.8 inches.

Jan. 11, 2017 | Tags: past weather, records/extremes, snow

Question: So do reporters stay over at station or nearby walking hotels? Or do you have to drive in these conditions? Am curious! — Peggy

Answer: The station attempts to both keep us safe and ensure that we can stay on the air in bad weather situations by contracting with a couple of hotels that are fairly close by. There might be more people involved than you would initially think, as keeping our operation going requires anchors, reporters, meteorologists, producers, directors, crew members for audio and video, editors, managers, web site and mobile products staff, and so on. The hotels are a bit outside of walking distance, but close enough that the drive doesn't involve long distances, big hills and the like, and we operate shuttles using a couple of large 4-wheel drive vehicles.
Jan. 10, 2017 | Tags: preparedness, winter weather

Question: Why does Weather Underground no longer list month-to-date and year-to-date precipitation totals? I'm suffering from withdrawal. — Doug Black

Answer: We're wondering if you might have caught the siteon a day with a glitch of some sort. As far as we can tell, those two variables are still listed in the "summary" section of the historical data section of their web site. If you go to the "Almanac" section of our weather page and use the "Get Historical Data" section to view observations from a selected date, we send you to the Weather Underground listing for RDU on that date by default. Once there, you can also choose to change the weather station location and the date, or to view the data by week or month instead of for a single day.
Jan. 9, 2017 | Tags: past weather, wral.com

Question: When was the last full day of sun? — Patricia

Answer: Friday, December 30th was a rather bright day with only two tenths cloud cover, although there were some periods with scattered clouds at 6-7,000 feet above the ground. Before that, the next prior day with even less cloud cover was Saturday, December 10th 2016, with much of the day clear, and just a few hours in which thin, sparse cirrus clouds at about 25,000 feet up were reported. That day had only 1/10th of possible cloud cover, and most of us would have considered it a "sunny" day.
Jan. 8, 2017 | Tags: clouds, past weather

Question: What is the bright star in the southwest sky? — Martin

Answer: Based on the time and date you sent in your question, along with the direction you noted, we're quite certain you were seeing the planet Venus, in its current position as the "evening star." Early that evening, it was located about 30 degrees of elevation above the southwest horizon, gradually setting from that point, and as is typical for Venus, was very bright.
Jan. 7, 2017 | Tags: astronomy

Question: What days did we have thunder this week? — Tammy Woerner

Answer: You were asking about the final week of 2016, and during that week there was some thunder that occurred in areas south and east of Raleigh on Thursday morning, December 29th. As far as we could determine, that was the only day of the week with storms in the central/eastern NC region.
Jan. 5, 2017 | Tags: past weather, thunderstorms

Question: For the past few days I have been checking on the forecast for January 6-8 and seeing a possible snow storm. Every day it changes. For instance, a few days ago it said snowfall could be seen up to 10 inches, but now it says just a trace. Have you been tracking this storm? — Aiden Salpeck

Answer: We're writing this answer a couple days before you'll see it, and at this time the low confidence and variability of modeled solutions for that time frame continues to be significant, with different models showing dramatically different patterns once we get beyond about Thursday and beyond - in addition, as you noted each new round of model projections this far in advance has frequently differed notably from those run just 6 or 12 hours earlier, as new observations are ingested. For that reason, there isn't much we can tell you about specific timing, types or amounts of precipitation that isn't highly subject to change by the time this is published, so we'd encourage you to tune in to our weathercasts and check in frequently on our online and mobile forecasts for updates as we finish the week and head into the weekend.
Jan. 4, 2017 | Tags: preparedness, winter weather, wral.com

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