Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
200 AM EST Thu Feb 21 2019
Valid 12Z Sun Feb 24 2019 - 12Z Thu Feb 28 2019
...Major Upper Midwest/Great Lakes/Interior New England Winter
Storm Sunday/Monday...
...Guidance/Predictability Assessment and Preferences...
Guidance was reasonably well-clustered at mid-larger scales
through the medium range period and a composite blend of the
latest ECMWF/UKMET/Canadian and ECMWF ensembles offers a
reasonable starting point for the forecast. The GFS and GEFS are
less robust to bring lower level colder air southward next week
and their solutions were downplayed as the FV3 showed an opposite
trend more in line with the other guidance.
...Weather Highlights/Hazards...
A threat for significant snows/some icing exists around a deep
surface low. The rapidly deepening system (central pressure fall
of about 20mb/24 hrs between Sat and Sun morning) lifts into the
Great Lakes and then exits out the St. Lawrence Valley Sunday into
Monday. This system has the potential to deepen into the upper
970s mb or at least low 980s mb which may be close to monthly
record low pressure values for portions of Lower Michigan Sunday.
Expect strong/gusty winds and potential blizzard conditions over
the Upper Midwest/Great Lakes and into Canada Sunday-Monday. Mild
air will surge northward east of a trailing cold front with a
brief spike in temps to the 60/70s as far north as the
Mid-Atlantic. Farther south, a prolonged heavy rain pattern will
finally end with cold frontal passage, with lead record warm temps
possible over Florida.
A long-standing and wintry mean upper trough over the West
deamplifies next week, but will still be reinforced over the
Northwest into Sun-Mon as energy undercuts and digs to the lee of
a blocking Alaska-centered closing upper high. This will bring
unsettled weather across the Northwest/Northern CA and the
north-central Intermountain West/Rockies. The best chance for
heavy snow will be from the Cascades to especially northern CA
with emergence of uncertain Pacific flow undercutting the northern
stream.
Flatter flow downstream over central and eastern U.S. next week
reduces potential for big storms, but a series of smaller/less
predictable systems will progress over the region. This will still
favor cold air surges/anomalously cold temps through the n-central
U.S. and snow swaths over the northern tier states. Rainfall also
redevelops across the Gulf Coast/FL with the fronts, but guidance
has backed off with amounts.
Schichtel
WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation and winter weather outlook
probabilities are found at:
https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif
https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html
https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4