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USNA News Center

A Cool Pattern this Weekend (and perhaps the first frost of the season) 14 OCT 2015

  POSTED ON: Wednesday, October 14, 2015 2:22 PM by A.R. Davies

The first in a series of cold fronts pushed across Maryland on Tuesday, with the second, and perhaps more pronounced, front on-tap for Friday. As a result, seasonably cool conditions are likely through the weekend, along with our first true taste of Fall.  As shown in the Figure below, the five day average temperatures (Thursday-Sunday) will be 3-4oC (~7-9oF) below the climatological mean.

Five Day Avg Temperature Anomaly (15-19 OCT)

The initial frontal passage on Tuesday evening dropped the regional temperatures on Wednesday back closer to the climatological norm (upper 60’s) via northwesterly flow and partly sunny skies.  High pressure will build across the Ohio River Valley on Thursday, resulting in sunny and seasonably conditions. As shown in the Figure below, a clipper system will slide to our north Thursday evening, with a trailing cold front set to pass the region during the day on Friday.  Like the frontal passage on Tuesday, very little rainfall will be associated with the system (only a 25% chance of rain on Friday).

6 hour precip, MSLP, and 850 mb temperature at 0800 on 16 OCT

Behind the clipper, a brisk northerly wind on Saturday will usher in the coldest air of the Fall season thus far.  Well north and west of Annapolis, there is a chance for some topographically-induced snow showers on Saturday across central Pennsylvania, western Maryland, and northern West Virginia (windward side of the Appalachian Mountains).  Closer to home, the overnight low temperatures will approach the freezing point early on Sunday and Monday morning. As shown in the Figure below, the NCEP GFS (American Model) Ensemble Mean suggests the freezing line will be just north and west of I95 on Sunday morning, with roughly a 10% chance of the overnight low dropping below freezing in Annapolis, MD.  The probability of the first frost of the season increases considerably north and west of Annapolis, away from the water and in the colder valleys.  By Tuesday, expect a bit of a warm-up with the high temperatures back in the upper 60’s.

Probability (%) of the minimum temp < 32 degrees at 0800 on 18 OCT


Disclaimer: This is not an official U.S. Navy weather forecast and should not be confused with the official Navy weather forecast provided by the Fleet Weather Center in Norfolk, VA.  Furthermore, the official U.S. Government forecast for the greater Annapolis area is issued by the National Weather Service Baltimore/Washington Forecast Office in Sterling, VA.

Category: General Interest


Alexander Davies
Meteorologist & Oceanographer
Oceanography Department