Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Pittsburgh PA
913 PM EDT Thursday Aug 28 2014
high pressure will keep the region dry through Friday.
Warmth...humidity...and the chance for showers and storms return for
Near term /until 6 am Friday morning/...
no major changes were needed for the late evening update.
temperatures will fall below the seasonal avgs tonight as dry high pressure
slides over the region. The cool morning lows were forecast close to
bias corrected GFS MOS...but with downward adjustments for the
ridge and northern counties.
Short term /6 am Friday morning through Sunday night/...
amplifying ridge aloft...in advance of northern plains to upper MS valley
trough...will ensure precipitation free conditions...but with warming temperatures
Developing SW flow and forcing for ascent with the eastward advance of that
trough is forecast to increases moisture and precipitation chances by Saturday
afternoon...and cumulate in likely probability of precipitation with passage of the trough axis
Warm temperatures throughout the short term period were prognosticated using a blend
of already close bias corrected GFS MOS and sref means.
Long term /Monday through Thursday/...
several disturbances embedded in zonal flow aloft will keep occasional shower
and thunderstorm chances through much of the long term period. The best chance for
precipitation will be with stronger wave toward middle weak. Temperatures should average several
degree above the seasonal levels.
Aviation /01z Friday through Tuesday/...
dry surface high pressure undr weak west-northwest flow aloft will ensure genl VFR and
light surface wind through Friday. Some fog is expected in the river
valleys during the pre dawn...and that could briefly impact the
sites closest to the rivers.
Outlook.../Thursday through Monday/...
crossing low pressure is likely to generate showers...tstms...and
restrictions on Sunday.