NWS Sterling for next week:
Beyond Sunday, the pattern turns active once again. During the early
to mid week time period, there`s reasonable confidence surrounding
the placement of larger scale features, but higher levels of
uncertainty with respect to the smaller scale details, which of
course will be critical in determining the sensible weather
conditions that we ultimately experience.
During that time period model guidance is in good agreement that a
relatively persistent pattern will develop on the synoptic scale,
with strong upper ridging over the Eastern Pacific/Alaska and deep
troughing downstream over central and eastern Canada. At jet level,
a strong jet extending across much of the Pacific will split into
two streams, with one riding up and over the Alaskan Ridge, and
another undercutting the ridge, and then progressing eastward toward
southern California, and eventually east to northeastward across the
CONUS. Subtle disturbances originating in both the northern and
southern streams will move eastward through the waveguide, moving
atop a sharp north-south temperature gradient in place across much
of the CONUS, with each disturbance providing a chance for some warm
advection driven precipitation. With various rather subtle
disturbances originating in both the northern and southern stream
impacting the forecast, confidence in the smaller scale details
remains low.
Compared to yesterday, chances for snow on Monday have trended
downward, but there`s still a low-end threat showing up in ensembles
from central Virginia to southern Maryland.
The greatest chance for a more substantial wintry precipitation
event still looks to be during the day Tuesday, as a disturbance
currently in the southern stream over the central Pacific reaches
the Southern California coast Monday and then rapidly accelerates
east-northeastward across the CONUS. Snow and/or ice look to be the
most likely precipitation types with this system, with locations
further north having greater chances to see all snow, and locations
further south having greater chances for mixing with sleet and
freezing rain. A changeover to all rain may even be possible across
southern portions of the forecast area. Latest incoming guidance
shows relatively high probabilities (greater than 50 percent) for a
plowable snow across much of the forecast area (especially
along/north of I-66/US-50), but there`s plenty of time for northward
or southward shifts in guidance to change the outlook. We will
continue to monitor this system over the upcoming days.
Guidance begins to diverge further by Wednesday. Some models (such
as the 00z Canadian) continue the wintry precipitation through
Wednesday, while most others bring the precipitation to an end,
leading to dry conditions.
