This list contains the more common questions directed at the National Weather Service
in Seattle, either by phone or through e-mails to
the webmaster. So before contacting the National Weather Service, please read this list of commonly asked questions. Please be aware that if you call during a particularly active weather
situation, we may ask you to call back at a later time.
This is because we need to focus our resources on the situation at
hand. We are glad to fulfill your request, but
our primary mission of helping save lives and property must come first!
can I get historical weather and climate information?
A1. Our Climate
Page should be the first place you go for climate and
historical weather data within the past 5 years. The NOWData interface can help you find records, normals,
and provides many other ways of sorting data for sites in western Washington.
If you need any certified data for legal purposes, or if you need a large volume of data (an amount that would take our staff more than 5-10 minutes to collect),
contact the National Climatic Data Center (NCDC). If you need to
call them on the phone, do so early in the day since they are in the
Eastern Time Zone. NCDC usually charges a small fee for their services.
The Western Region Climate Center is also available for climate
The National Climatic Data Center
151 Patton Ave, Room 120
Asheville, NC 28801-5001
Phone: (828) 271-4800
Fax: (828) 271-4876
For hourly weather data within the past 30 days, go to the
State Obs Map. Select your site of interest. In the resulting web address, there should be a part reading "num=48". Change this part to
read "num=744". This feature controls the number of hours for which data is displayed. You can get up to 30 days of data this way!
If you find a site on the State Obs Map but want data that is more than 30 days old, go to
Select a location. In the pop-up window on the left-hand menu, choose either the "Past Data" or "2 Week Summary" feature.
If you still can't get what you need, then call us anytime at 206-526-6087, or e-mail us at firstname.lastname@example.org.
Q3. How can I arrange a tour of the National Weather Service?
A3. Tours of the National Weather Service
in Seattle are available by appointment only. Tours for groups with children younger than 9 years old are not recommended.
The optimal ratio of participants to tour guides is 15:1; the maximum ratio is 25:1. Groups of more than 50 people are discouraged.
Tour length is typically 45 to 60 minutes. If you are interested in setting up a tour, please
start by filling out our online request form. You may also
call our office at 206-526-6095.
Q4. What are the current road conditions across the mountain passes?
A4. The Washington State Department of Transportation (WSDOT) is the authority on current road conditions,
tire requirements and closures. Access the most up-to-date road information
for the mountain passes by:
Q5. How should I submit a weather or spotter report?
from weather spotters are most valuable to our forecasters
in real-time as an event is unfolding, or soon after the
event is done. Therefore, the quickest way to pass along your
information is to call us on the telephone.
Trained Skywarn (TM) Weather Spotters are given a
spotter identification number and an unlisted toll-free phone number
to use when calling us. If you are not a spotter but would like to be one, please visit our
Spotter Page for more information. In the meantime, non-spotters can
pass along weather reports through our public phone number,
206-526-6087. For information on what to report, click here.
Please do not submit a weather report via the webmaster e-mail account.
Checking the webmaster e-mail account is a low-priority duty, especially during active weather. It typically gets checked about once each week but can go unchecked
for up to a month during the winter holidays and summer break.
A7. Meteorologists across the globe use the same standard for keeping time. This avoids confusion in coordinating weather data from numerous
time zones around the world. The standard for timekeeping is called "Greenwich Mean Time" (GMT). GMT is the current local time in Greenwich (London),
England, where the Prime Meridian is established (zero degrees longitude). Other names for GMT are UTC (Universal Coordinated Time)
and Z Time (Zulu Time). Any of these terms (GMT, UTC, Z) are acceptable, and they all mean the same thing. Most U.S. meteorologists
use the term Z-time. So when you see 12Z, that means it is 12 noon in Greenwich, England. 20Z means it is 8 pm there,
and 00z means it is midnight there.
Here in the Pacific Time Zone, you would subtract 7 hours to get Pacific Daylight Time (PDT) from mid-March to early November. During Standard
Time (early November-mid March), you would subtract 8 hours to get Pacific Standard Time (PST). For example:
12Z = 4 AM PST (by subtracting 8 hours)
12Z = 5 AM PDT (by subtracting 7 hours)
20Z = 12 noon PST (by subtracting 8 hours)
20Z = 1 PM PDT (by subtracting 7 hours)
00Z = 4 PM PST (by subtracting 8 hours)
00Z = 5 PM PDT (by subtracting 7 hours)
04Z = 8 PM PST on the previous day (by subtracting 8 hours)
04Z = 9 PM PDT on the previous day (by subtracting 7 hours)
A8. In listing weather conditions, such as at
this link, there are six different codes that are used for sky cover. Each represents
a different amount of cloud cover. The codes are:
SKC: Completely clear skies
CLR: No clouds below 12,000 feet. (12,000 feet is the upper limit where most automated instruments can detect clouds)
FEW: 10-20% cloud cover
SCT: 30-50% cloud cover (short for "scattered")
BKN: 60-90% cloud cover (short for "broken")
OVC: 100% cloud cover (short for "overcast")
The numbers that follow the coverage codes represent the height of a cloud base in hundreds of feet above the ground. For example, OVC013 means that there
is an overcast layer of clouds 1,300 feet above the ground. 001 means clouds only 100 feet above the ground, and 200 would indicate clouds 20,000 feet
above the ground..
Q9. In the Current Conditions listings, why do
amounts in the 1-hour Precip column not always add up to equal the 24-hour Precip?
A9. In our Current Conditions listings (here is an example),
1-hour precipitation amounts do not always add up to equal the 6-hour and 24-hour totals. This is usually because the 1-hour precipitation
amounts reported at airports get reset only once every hour. The resetting always takes place at the time of the
routine observation (usually about :53 to :55 past each hour). If rapidly changing conditions warrant a special observation at a non-routine time,
the observation will indicate an incomplete 1-hour total since the last routine hourly observation. If you are trying to corroborate the
"hourly" precipitation with the
24-hour precipitation, you will only want to add hourly precipitation reports from the routine hourly observations around :53-:55 past each hour
and throw out amounts reported in the special non-routine observations.
Q10. What is the difference between rain and showers?
A10. "Shower" is used to describe precipitation that is discontinuous. "Showers"
are characterized by the suddenness with which they start and stop,
by the rapid changes of intensity, and usually by rapid changes in
the appearance of the sky. In western Washington, when the forecast calls for a high probability of showers, you
would usually expect breaks in the rain with sun breaks between showers. A forecast for "showers" does not usually imply a complete washout,
or all-day rain.
"Rain", or stratiform precipitation, is relatively continuous and uniform in intensity (i.e., steady rain versus rain showers). "Rain"
will usually develop gradually, last for hours, and then end gradually. All-day washout type rains are described by the term "rain".
are Heating Degree Days and Cooling Degree Days?
A11. Both of these Degree Days (abbreviated HDD and CDD) are used to estimate energy requirements for heating and air conditioning.
Heating degree days are typically calculated as how much colder the mean temperature at a location is than 65°F on a given day.
For example, if a location experiences a mean temperature of
55°F on a certain day, there were 10 HDD (Heating Degree Days) that day because 65 - 55 = 10.
Cooling degree days are typically calculated as how much warmer the mean temperature at a location is than 65°F on a given day.
For example, if a location experiences a mean temperature of 75°F on a certain day, there were 10 CDD (Cooling Degree Days) that
day because 75 - 65 = 10.
Q12. Why do the Freezing Level forecast and the Temperature
forecast at mountain locations sometimes not match up?
A12. Multiple freezing levels sometimes develop over the mountains, and our meteorologists are typically forecasting the highest freezing
level. To get multiple freezing levels, you must have an atmospheric “inversion”. An inversion is simply a super-stable layer of the atmosphere
in which the temperature gets warmer, not colder, as you rise in elevation.
Inversions can develop under several scenarios. The most common scenario is what we call a nocturnal inversion.
This occurs when the temperature on the ground drops below freezing at night, even as the air temperature one thousand feet off the ground, or one thousand feet
up a mountain slope, remains above freezing. If this is the reason for an inversion and you are below the forecast freezing level, the temperature at your
location should rise above freezing in the afternoon.
Inversions are also quite common in the winter months near the major passes in the Cascades when an
upper ridge develops aloft and an east wind develops at the surface. During the long nights of winter,
cold dense sub-freezing air develops and becomes trapped in the deep sheltered valleys east of the Cascade crest. When an east wind develops,
it carries the low-lying cold air west through the passes in a shallow layer, often beneath warmer air above. In a pattern like this,
Snoqualmie Pass (near 3,000 feet) might have afternoon temperatures in the mid 20s, while Paradise (near 5,500 feet and well away from the passes) can easily be
20-30 degrees warmer, despite being 2500 feet higher in elevation. Again, it is the highest of multiple freezing levels that our meteorologists are usually forecasting.
Q13. Why are NWS text products typed in ALL CAPITAL LETTERS?
A14. It is not because we want to scream at you! This practice goes back many, many years and relates to international
requirements for message dissemination. Some of our international partners still use low-tech dissemination technology which requires
the continued use of ALL CAPS. Since the U.S. is an international member of the World Meteorological Organization (WMO), we follow those guidelines that still
exist for the benefit of all nations. That is why TAFs, AIREPs, Marine Forecasts, etc. are typed in ALL CAPS.