Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1256 AM EDT Sat Mar 21 2020
Valid Mar 21/0000 UTC thru Mar 24/1200 UTC
...See NOUS42 KWNO (ADMNFD) for the status of the upper air
ingest...
00Z Initial Model Evaluation with Latest Preferences and Confidence
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General weather pattern across the continental U.S.
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Preference: General model blend through 12Z Sunday, then 00Z
GFS/00Z UKMET/12Z ECMWF blend
Confidence: Slightly above average
A split flow pattern aloft will initially be in place across the
continental U.S. on Saturday with a couple of progressive
shortwave troughs in the northern stream and a fairly zonal
southern stream across the southern tier states. A lead shortwave
trough crossing the Desert Southwest early Saturday is expected to
phase with the second in a series of disturbances originating from
western Canada by early Monday across the Ohio Valley region, and
this is expected to spur surface cyclogenesis off the East Coast
for the beginning of the work week. This will likely become a
nor'easter near the New England coast by Monday night as the
phased trough aloft approaches.
Behind the lead shortwave mentioned above will be a large upper
level low that will track eastward towards central California by
Sunday night, and evolve into an open wave as it crosses the
Rockies through Monday. Another upper level low in the northern
stream will track southward along the British Columbia Coast and
reach the Pacific Northwest late Monday and into Tuesday,
accompanied by a cold front moving inland across the region.
The models are in good agreement through Sunday morning. The CMC
becomes considerably slower with the second shortwave arriving
across the northern Plains Sunday night and then becomes too weak
with this feature over the Great Lakes region, leading to a weaker
disturbance near the East Coast. The NAM becomes more amplified
with the southern stream trough that eventually phases, especially
by Monday morning. There is good overall agreement with the upper
low approaching the Pacific Northwest. By the end of the forecast
period, the GFS and CMC are a little farther offshore than the 00Z
UKMET/NAM/12Z ECMWF.
Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml
500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml
Hamrick