HMT Forecast 2/6/2008 19:41 UTC
Not much has changed since yesterday over the ARB. The previous forecasts still remain valid. This morning the satellite water vapor imagery indicated a plume of moisture reaching the E Pacific coastal areas near 49N 127W. The near term models show coastal showers a possibility today/tomorrow with the main moisture going north of the ARB. However, I would not rule out a brief shower or two.
Models show a ridge building over the coast that reaches its maximum on or about 06UT 2/9 (Saturday) and then a short wave crossing the area on or about 12UT 2/10. It is not anticipated that this will bring significant precipitation to the ARB. Following this, the ridge rebounds by 00UT 2/12 and a cut-off 568 low develops beneath the ridge at 29N 119W. By 18UT 2/13 the cutoff opens and progresses as an open wave to the south of the region (this is in the GFS). In contrast, the EC doesn't create the intense cutoff low under the ridge but has a more vigorous open wave progressing over the ridge that brings 0.02 inches of precip to the ARB on or about 2/13.
During yesterday's telecon the question arose regarding the conditions for melting the snowpack that exists in the ARB. I am not an expert in this area but did run some numbers. The current integrated daily solar energy flux for today over the ARB is 9.87 MJ/m^2 (horizontal plane), this for comparison purposes is about 50% more energy than the area was receiving at winter solstice (6.42 MJ/m^2), and for further comparison the region receives 27.37 MJ/m^2 at summer solstice. Also, I forecast today's high temperature for the ARB to be about 44F, cooler at mountain tops. Unfortunately, I lack the background knowledge to translate this into snowmelt from sensible and radiative heat flux, but maybe someone reading this blog can determine that from these numbers.
The general forecast for near term IOP events remains nil. The long range forecast past 228 hours looks to break down rapidly in the ensembles. Up to that time, there does not appear to be an IOP opportunity. Perhaps we can enlist climate experts to help us with a long-term forecast discussion.
Dan Birkenheuer ESRL/GSD