Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Raleigh NC
251 PM EDT Thursday Oct 23 2014
Synopsis...an upper level low will track northeast of Long Island
and offshore the New England coast tonight before progressing into
the Canadian Maritimes on Friday. Meanwhile...an upper level
disturbance will dig southeast through the Tennessee Valley into the
southeastern United States on Friday.
Near term /through tonight/...
as of 251 PM Thursday...
A corridor of pronounced subsidence will prevail over the region
this afternoon...between an upstream (tn/Ohio valley) ridge and a
downstream (mid-Atlantic coast) upper level low. Subsidence will
diminish tonight as the middle-Atlantic low tracks further downstream
and an amplifying shortwave trough digs southeast through the
upstream ridge into the Tennessee Valley...though the impact thereof
(dry/stable atmosphere) will remain intact. As a result...expect
clear skies with near normal temperatures tonight. Lows 40-45.
Short term /Friday and Friday night/...
as of 145 PM Thursday...
An amplifying shortwave trough digging southeast through the
Tennessee Valley will track into western NC/upstate SC by sunset
Friday evening...then progress to the southeast coast by sunrise
Sat. Due to the dry/stable airmass in place in the low/middle
levels...forcing (i.E. Dpva) associated/west the upper level wave will be
confined almost entirely to the upper levels (~500 mb) of the
atmosphere. With the above in mind...expect clear skies on Friday
followed by a modest increase in upper level cloud cover (cirrus)
Friday night. Near normal temperatures will persist given little
change in airmass. -Vincent
Long term /Saturday through Thursday/...
as of 125 PM Thursday...
Dry and mild to warm this weekend into next week...
There were only minor issues to consider in the weekend forecast. In
general... rising heights are expected over the southern and
southeastern states with a mean westerly flow. This is a dry flow
and often times is one in which temperatures end up warmer than
statical guidance. The only issues will be the timing of a weak
cold front or surface trough Saturday night and the temperature
forecasts this weekend.
Regardless... a mild to warm weekend is anticipated with a brief
period of middle level cloudiness Saturday night. The mean westerly
flow ahead of the front on Saturday suggests a warming downslope
flow with highs in the 70s. A period of middle level clouds and mixing
should lead to milder lows in the 50s for most areas Saturday night.
Sunday... even though the weak front will drift south and weaken...
sunny skies are expected with highs again well into the 70s. The NE
zones may be a few degrees cooler Sunday (compared to saturday) as
the significant cold air advection is directed more across the northern middle-
Atlantic into New England... but may graze the NE zones for a brief
Monday through Wednesday night should continue to be dry and warm. A
return flow to the southwest should give temperatures even more of a
boost as upper heights rise in the mean zonal flow. Highs may hit 80
over portions of the region Tuesday and/or Wednesday.
A weak cold front may again brush the area Thursday. However... only
subtle cooling is expected late in the week... with a continued dry
look to the overall flow pattern for our region.
Aviation /18z Thursday through Tuesday/...
as of 1145 am Thursday...
24-hour taf period: VFR conditions /clear skies/ will rule through the
taf period in associated/west a dry northwest flow between a potent upper
level low along middle-Atlantic coast and a shortwave ridge upstream
across the Tennessee/Ohio Valley. A northwest breeze at 10-15 knots will decrease to 5
knots or less by sunset...becoming calm overnight.
Looking ahead: VFR conditions will persist through early next week
in associated/west a dry northwest flow aloft. -Vincent