Extreme Dewpoints to -44 in Western NC Saturday
Fellow blogger Frank Strait pointed out this unusual situation last Saturday in the North Carolina and Virginia mountains (my old stomping ground)... official reporting stations had extremely low dew points (as low as -44 F!) producing extremely low relative humidities (2-3%!) Here's a map of the lowest dew points recorded that day (I have circled Jefferson, NC and Hillsville, VA):
Note that both of those are official NWS stations, and neither are marked Orange (Caution) by MESOWEST (though some observations near that time were).
Of course, government sensors, especially dew point sensors, are notorious for being inaccurate. Still, the data was reported by multiple stations at the same elevation and looking at this Stuve Diagram (a SKEW-T that makes sense to non-meteorologists by plotting temperatures vs. height as perpendicular lines) I think that it's plausible that the readings were correct:
That chart shows dew points below -40 at around 5,000 feet elevation which would include the highest elevations in the Appalachian mountain chain. That sounding was taken at Roanoke the night before which is considerably to the NE of the readings we observed, so I don't think it's out of the question to think that air might have dipped to the elevation of Boone (3179 ft.) or Hillsville (2179 ft.)
Frank thought it could have been a rare "tropopause fold" event but the upper air archives I have didn't specify the tropopause level and it's been too long since college (we both went to UNC-A) to speculate further. If you have an opinion leave me a Comment.
Report a Typo
