The Geography of Cold

This morning it was mightly cold out there...particularly as I biked into work. But such cold varies greatly over the area, particularly on cold mornings in winter when the winds are light. This morning was a good example (see map). At 8 AM the temps varied from the upper teens in the western foothills of the Cascades to the mid-30s over Puget Sound. The range of temperatures were somewhat limited last night by the considerable cloudiness, that lessens the ability of the surface to radiate heat to space. Thus, on some nights the range of temperatures are even greater. In my NW weather book, I describe a night when five cars of UW students and staff drove around the region in instrumented cars. We found temperatures ranging from 25 near Maple Valley to 45 near the sound. Temperatures were several degrees cooler in valleys that were only 50-100 feet lower than the crests. Tomorrow morning should be just as cold, with temps certainly getting into the mid and lower 20s. My rhodies are not doing well.
The models are in agreement that conditions should stay dry until this weekend, when some frontal systems will approach, bring rain and warming conditions. But the real excitement may be early next week, when some models are suggesting a potential pineapple express period..with heavy rain in the mountains.
F