Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
353 PM EST Thu Feb 28 2019
Valid 12Z Sun Mar 03 2019 - 12Z Thu Mar 07 2019
...Low pressure system likely to bring threat of heavy snow/ice
from portions of the Mid-Mississippi/Ohio Valleys to the
Mid-Atlantic and Northeast Sun-Mon...
...Pattern Overview...
The forecast of large scale flow has maintained good continuity
over the past day. Downstream from persistent mean
ridging/positive height anomalies over northwestern North America,
a trough will amplify into the eastern U.S. with greatest depth
around midweek before the trough axis continues into the western
Atlantic. At the same time a mean ridge will build into the
west-central U.S. as a mean trough settles near the West Coast.
...Guidance Evaluation/Preferences...
Agreement among models/ensembles has improved significantly over
the past 24 hours with respect to many of the forecast details
during the medium range. A blend of the latest deterministic
solutions (ECMWF/GFS/CMC/UKMET) was used as a starting point for
the forecast during days 3-5 (Sun-Tue). Solutions are now
relatively well clustered around the ensemble means with the wave
of low pressure expected to move from the lower Mississippi Valley
to off the New England coast Sun-Mon, with confidence increasing
in the potential for significant winter weather north/west of the
low track. Farther west, models also show improved consensus with
respect to an energetic shortwave/low pressure system expected to
reach the West Coast Tue night into Wed. Solutions show spread on
both timing and amplitude of this feature, however the ensemble
means are reasonably well-centered within the spread. This makes
the means suitable to comprise a significant component of the
forecast for days 6-7 (Wed-Thu). Overall, the forecast remained
close to continuity with only minor adjustments.
...Weather Highlights/Hazards...
A broad area of precipitation will accompany the vigorous wave
tracking northeast over parts of the eastern states and into the
Canadian Maritimes Sun-Mon. Northwest trends in the past day have
pushed the most likely area for significant wintry weather to an
axis extending from the Mid-Mississippi Valley/Ohio Valley into
portions of the Mid-Atlantic and Northeast. At this time, the
specifics remain a bit murky with respect to p-type in the major
cities along the East Coast, but the greatest potential for heavy
snows should be across interior areas from Ohio/Pennsylvania to
interior New England. A more consistent theme from yesterday is
the potential for heavy rainfall over parts of the Lower
Mississippi Valley and Tennessee Valley/interior Southeast.
Rain and higher elevation snow in progress over the
central/south-central parts of the West late in the weekend will
taper off from west to east. Then from Tue onward the next system
in the series will spread a broad area of moisture across the
West, with greater northward extent than with the previous system.
Favored terrain over northern and central California should once
again see the highest precipitation totals with this system.
Moisture reaching northern portions of the West may bring wintry
weather to low elevations over some areas given the cold
temperatures in place from early in the week.
Continue to expect coldest temperatures relative to normal during
Sun-Mon with some central U.S. locations seeing anomalies of
30-45F below normal and a widespread area over the Plains/Midwest
with readings that will approach or break daily records--more
likely a greater number for cold highs. Interior Northwest
locations may also see some temperatures at least 20F below normal
with local challenges to daily records. The area of potential
daily records will likely shift more into the eastern half of the
country (Midwest/Great Lakes/Ohio Valley) by Tue.
Ryan/Rausch
Hazards:
- Heavy rain across portions of California, the Central Great
Basin, the Pacific Northwest, and the Southwest, Tue-Wed, Mar
5-Mar 6.
- Heavy rain across portions of the Mid-Atlantic, the Northeast,
the Tennessee Valley, the Lower Mississippi Valley, the Southern
Appalachians, the Southeast, and the Ohio Valley, Sun-Mon, Mar
3-Mar 4.
- Heavy snow across portions of the Central Great Basin, the
Northern Plains, the Northern Rockies, the Central Rockies,
California, the Northern Great Basin, the Pacific Northwest, and
the Southwest, Wed-Thu, Mar 6-Mar 7.
- Heavy snow across portions of the Central Rockies, the
Northeast, the Central Great Basin, the Southern Rockies, the
Middle Mississippi Valley, the Mid-Atlantic, the Southern
Appalachians, the Central Appalachians, the Great Lakes, the Ohio
Valley, and the Southwest, Sun-Mon, Mar 3-Mar 4.
- Heavy snow across portions of the Central Rockies, Thu, Mar 7.
- Severe weather across portions of the Southeast, the Lower
Mississippi Valley, the Southern Appalachians, and the Tennessee
Valley, Sun, Mar 3.
- Flooding possible across portions of the Mid-Atlantic.
- Flooding occurring or imminent across portions of the Lower
Mississippi Valley, the Tennessee Valley, the Great Lakes, the
Middle Mississippi Valley, the Mid-Atlantic, California, the Upper
Mississippi Valley, the Southeast, the Pacific Northwest, and the
Ohio Valley.
- Flooding likely across portions of the Southeast.
- Much below normal temperatures for much of the eastern
two-thirds of the country, including the interior sections of the
Pacific Northwest, Sun-Thu, Mar 3-Mar 7.
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