Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
1204 PM EST Tue Mar 05 2019
Valid 12Z Fri Mar 08 2019 - 12Z Tue Mar 12 2019
...A Stormy Pattern with Multiple Hazards Continues over the
Nation...
...Model Guidance Evaluation and Preferences...
The WPC medium range product suite was mainly derived from a
composite blend of well clustered guidance from the latest
GFS/ECMWF and GEFS/ECMWF ensemble means in a stormy pattern with
above normal forecast predictability. Adjusted blend weightings
gradually from model guidance to the ensembles over time
consistent with gradually growing forecast spread.
...Weather Highlights and Hazards...
A lead system works through and the east-central then eastern
states Friday into Saturday that offers modest but widespread
moisture/precipitation potential. This will include some snow/ice
threat potential to the north of an associated wavy front and
modest coastal low as moisture spreads over slow to recede
cold/dammed high pressure.
Meanhwhile, heavy snows will likely continue on Friday focusing
into favored terrain of the Intermountain West and Rockies as the
strong Pacific disturbance crosses the region. Total snowfall
amounts on the order of 1 to 2 feet are possible across parts of
the central and northern Rockies, before easing this weekend in a
pattern with secondary northern stream energies and associated
cold surge works down through the West.
Ample mid-upper level trough energy moving out of the West will
lead to cyclo/frontogenesis over the central U.S. Widespread rain
and thunderstorms are then slated to develop from the Gulf Coast
to the Ohio Valley and southern Appalachians this weekend as a
rich supply of Gulf moisture surges northward ahead of a strong
cold front from the surface low. The heaviest rainfall is likely
from eastern Texas and Tennessee Valley/Mid-south to the southern
Appalachians, where heavy rains/repeat cells are likely to lead to
some flooding issues. There is a significant threat for heavy
wrapping snow/ice and a corridor of blizzard conditions across
parts of the northern plains, Upper Midwest, and western Great
Lakes region. Another facet to this deep low will be potential for
strong to severe thunderstorms to develop in the warm sector that
the Storm Prediction Center is currently monitoring.
Upstream, the pattern again favors amplified mid-upper level
trough development off the west coast this weekend. This will
support modest precipitation over the Pacific Northwest but more
ample height falls and cooling are slated for California and the
Southwest early next week. This would enhance precipitation focus,
though current forecast amounts are mainly moderate. Additional
widespread rain may then develop across the s-central U.S. in
about a week as the system works into the region to spawn another
round of cyclo/frontogenesis.
Schichtel
Additional 3-7 Day Hazards information can be found on the WPC
medium range hazards chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php
WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation, winter weather outlook probabilities
and heat indices are 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
https://www.wpc.ncep.noaa.gov/heat_index.shtml