Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
157 AM EST Tue Mar 5 2019
Valid 12Z Fri Mar 8 2019 - 12Z Tue Mar 12 2019
...Weather Pattern Overview...
An active weather pattern is expected during much of the medium
range period as a large scale trough originating from the Pacific
amplifies over the Rockies and High Plains. This will induce
surface cyclogenesis east of the Rockies and become a strong
surface low as it tracks northeastward. A second disturbance is
forecast to affect the West Coast region by early next week, and
this should also lead to the development of the surface low over
the southern plains by the end of the forecast period.
...Model Guidance Evaluation and Preferences...
The models and ensemble means indicate reasonable agreement on the
synoptic scale for the end of the week, and slightly better
agreement compared to yesterday. One of the main differences on
Friday is that the GFS based guidance indicate a more developed
lead surface low crossing the Ohio Valley region, whereas the
CMC/ECMWF/UKMET support more of an elongated surface trough.
The strong surface low that is forecast to develop across the
Plains and then track northeastward is indicating reasonably good
agreement on Saturday morning across eastern Colorado as lee
cyclogenesis gets underway. Model differences are more apparent
by Sunday regarding the track of the surface low across the
Midwest states and then the Great Lakes region. In terms of
trends, both the EC mean and GEFS mean continue to trend stronger
and slightly faster with this storm system, and the Canadian mean
has trended closer to the GEFS and EC means compared to
yesterday's runs. Similar to yesterday, the FV3 is faster than
the model consensus and loses ensemble support. The GFS and its
ensemble members are generally on the stronger side of the
forecast guidance. Taking all of these factors into account, the
forecast was primarily derived from the 12Z ECMWF/18Z FV3 and
GFS/12Z CMC for the first two days, and then some of the ECMWF and
EC/NAEFS mean for the second half of the forecast period. The WPC
forecast is similar to the previous one regarding the track of the
storm, except now it is forecast to be slightly more intense.
...Sensible Weather and Potential Hazards...
Widespread rain and thunderstorms are expected to develop from the
Gulf Coast to the Ohio Valley and southern Appalachians 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 to Tennessee, where a general 1 to 3 inches of rain
is likely that may lead to some flooding issues based on the
current forecast. Depending on where the surface low tracks, a
corridor of blizzard conditions will be possible across parts of
the northern plains, Upper Midwest, and western Great Lakes
region. It is still too early to mention precise locations given
current model differences. Another facet to this low pressure
system will be the potential for strong to severe thunderstorms to
develop in the warm sector, and this is something that the Storm
Prediction Center is currently monitoring. More rain is likely
across the central and southern plains by next Tuesday associated
with the next storm system.
Heavy snow will likely continue for another day on Friday across
the higher elevations 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 gradually ending early
Saturday.
The northern-central Plains will likely continue to see below
normal temperatures most days with highs tending to be 10-20F
below normal with locally more extreme anomalies one or more days.
The West will tend to see below normal highs for much of the
period but morning lows should be above normal late this week.
The southern and eastern U.S. should have a brief surge of warmth
ahead of the front associated with the Plains/Great Lakes storm
during the weekend, followed by a return to cooler weather.
D. Hamrick
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