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Prognostic Meteorological Discussion (PMD)

Issued by National Weather Service (NWS)

FXUS02 KWBC 211526

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
1026 AM EST Mon Jan 21 2019

Valid 12Z Thu Jan 24 2019 - 12Z Mon Jan 28 2019


Guidance shows an amplified upper pattern featuring an eastern
Pacific/West Coast ridge and an expansive east-central North
American trough. The overall mean pattern appears to have fairly
high predictability, but embedded shortwaves remain more difficult
to resolve. The ridge may retrograde a bit next week and
teleconnections favors an increased potential for positively
tilted troughing to then develop over the West.

...Guidance Evaluation/Preferences...

The WPC medium range product suite was derived from a blend of
reasonably well clustered guidance from the 00 UTC GEFS/ECMWF
ensemble means. The 06 UTC GEFS is not as well clustered.
Deterministic models offer even more run to run variance days 4-7
and their less certain detail was downplayed.

...Weather Highlights/Hazards...

Frontal waves will focus areas of significant precipitation in the
East Thu with the best snow potential over interior New England.
The Great Lakes will see episodes of snow all week from a
combination of passing systems and lake enhancement, with other
areas east of the Rockies seeing some precipitation with low
pressure/frontal passages. Another organized precipitation threat
over the East exists this weekend into next Mon. While forecast
confidence in coverage/intensity has been less than average, the
00 UTC GEFS/ECMWF ensemble means are now in better agreement with
the development of a mid-Atlantic coastal low. The rain-snow line
should extend fairly far southward given the cold pattern becoming
established over the eastern half of the country. Meanwhile at
least a couple shortwaves/fronts and trailing high pressure should
bring periods of snow to parts of the northern and central Rockies
with most activity likely to be in the light-moderate range.


WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation and winter weather outlook
probabilities are found at: