Highest Pressure in Decades Over The Northwest?

Do you feel the pressure?  Is it like the weight of the world is on your shoulders?  There may be a reason:  right now we are experiencing some of the highest atmospheric pressures in years and probably decades.

Take a look at the National Weather Service sea level pressure analysis at 7 PM (below).

A very strong high pressure area is centered over the Northwest and southwest Canada, with pressures greater than 1040 hPa over much of the region and a 1046 hPa center over southern BC.  1046 hPa is equivalent to 30.89 inches of mercury.  Folks, this is REALLY high sea level pressure.  At Sea-Tac the 9 pm pressure was 1042.6 hPa--and it is still going up!  There has been a huge pressure rise over the past 24h--roughly 20 hPa. The highest SLP I see at 9 PM is 1045.2 hPa at Lytton BC (elev 751 ft).

From experience I know these pressures are very unusual, but lets check the UW pressure archives.  Here are the hourly pressures at Sea-Tac airport since 1996.  Looks to me like the pressure last hour (9PM Wednesday is the final plotted red dot) was the highest during the entire record shown here (I confirmed by looking at the numbers).  So the highest pressure in 15 years!  That is impressive.

And the pressure is still going up!  The Portland International Airport has recorded a maximum barometric pressure reading of 30.76" (4:53am observation) which is tied for the second highest reading since records began at the airport in 1940 (thanks to Steve Pierce for this information). The bottom line is that we are experiencing truly unusual pressure right now...I wonder what this does to people with arthritis and sensitive joints.

 This push of high pressure over the Northwest is creating huge pressure gradients over the southwest U.S.  Here is the latest model prediction for tomorrow morning.  High pressure over us and a big pressure differences over Colorado, Utah, Nevada, California, and the offshore waters.

Very strong winds will be the result of these big pressure gradients, including gusts hitting 50-80 mph in places.   In fact, it has already started.  Take a look at the latest wind reports of greater than 45 mph over the western U.S.---quite a few of them.

And here are some recent reports from the National Weather Service office near Los Angeles.  Gusts as high as 69 mph so far.

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE OXNARD CA
802 PM PST WED NOV 30 2011

..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..

0557 PM NON-TSTM WND GST 1 NW SANTA CLARITA 34.42N 118.53W
11/30/2011 M67 MPH LOS ANGELES CA MESONET

67 MPH GUST AT SAUGUS RAWS LOCATED 1450 FT

0555 PM NON-TSTM WND GST 5 N SAN FERNANDO 34.36N 118.42W
11/30/2011 M64 MPH LOS ANGELES CA MESONET

64 MPH HOUR GUST AT CAMP NINE RAWS LOCATED AT 4000 FT

0753 PM NON-TSTM WND GST 8 ESE CASTAIC LAKE 34.60N 118.58W
11/30/2011 M69 MPH LOS ANGELES CA MESONET

69 MPH GUST AT WARM SPRINGS RAWS LOCATED AT 4930 FT

High pressure will bring us dry conditions and some sun...but air quality may decline.