Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
157 PM EST Sat Feb 12 2022
Valid 12Z Tue Feb 15 2022 - 12Z Sat Feb 19 2022
...Mid-late week system to bring potential for heavy rain and
severe weather from the south-central to east-central U.S. and
wintry weather from the Midwest through Great Lakes and interior
Northeast...
...Overview...
The dominant focus of the medium range forecast will be a sharp
upper trough likely centered from the northern Rockies through
California as of early Tuesday. This feature, possibly containing
an upper low for a brief time, will track eastward through midweek
and then become incorporated into a Plains/east-central U.S. mean
trough. This evolution aloft will lead to surface cyclogenesis and
strong frontal systems in the central U.S., drawing moisture
northward from the Gulf of Mexico and producing notable
precipitation from the Plains eastward next Wednesday into Friday.
Expect rain and thunderstorms in southern areas, while snow and
wintry weather are likely on the northern and western side of the
precipitation shield across the central Rockies/Plains and through
the Midwest, Great Lakes, and interior Northeast. By
Friday-Saturday expect a weaker clipper system tracking near the
Canadian border to bring a cold front into the northern tier while
a steadily weakening (but initially quite strong) eastern Pacific
upper ridge drifts toward the West Coast.
...Guidance Evaluation/Predictability Assessment...
Latest models and ensembles have been showing some incremental
adjustments for the upper system initially dropping into the West
and associated surface evolution through the week. To start the
period, guidance is keeping the western trough a little more open
and by early day 4 Wednesday gives mixed signals for whether there
will be a closed low--though still with majority support to favor
showing one in a single deterministic forecast. Either way the
recent trends have been for a more open feature as it ejects into
the Plains, leading to a somewhat weaker and faster surface system
from the Plains through Midwest and Great Lakes. Low pressure does
eventually strengthen farther northeastward as northern stream
dynamics increasingly influence the system. Latest CMC runs stray
southwest of other solutions with the western upper system and
then shear it out more dramatically farther east, resulting in a
weaker surface pattern. An average of GFS/ECMWF/UKMET runs from
the 00Z/06Z cycles provided a measured adjustment from continuity.
It will be interesting to see if persistence of a weaker scenario
in the CMC foreshadows additional weakening/progression in other
solutions, such as seen in the new 12Z ECMWF. Beyond the early
period detail differences, the combination of upstream energy
diving into/through the West from Wednesday onward and northern
stream troughing that reaches the Plains/Mississippi Valley still
contribute to some of the uncertainty in forecasts of this system
over the course of the period. Lingering southern tier shortwave
energy, with fairly low predictability for specifics, may have an
effect on frontal waviness and precipitation toward the end of the
period.
Elsewhere, continuity is fairly good in principle for the system
forecast to track near the Canadian border/Upper Great Lakes
around Friday-Saturday while typical differences exist for precise
timing of the trailing front. Models vary for a weak and
small-scale shortwave rounding the Pacific upper ridge and then
dropping into the West late in the period. Confidence is currently
minimal for specifics of this feature. However there is decent
agreement on an upstream shortwave/cold front approaching the
Pacific Northwest later next Saturday.
Preferences for the system over the West and continuing eastward
favored starting the forecast with the 06Z GFS/00Z ECMWF and 00Z
UKMET for about the first half of the period. Then the blend
incorporated some of the 06Z GEFS/00Z ECMWF means by days 6-7
Friday-Saturday given decreasing confidence in some details.
...Weather Highlights/Threats...
Underneath the upper low/trough over the West Tuesday into
Wednesday, expect light to moderate precipitation in the form of
lower elevation rain and mountain snow to spread from California
and Great Basin/Northern Rockies into the Central Rockies. Showers
and thunderstorms will become more widespread over the central
U.S. by Wednesday into Thursday as surface low pressure
consolidates in the High Plains and advects substantial moisture
from the Gulf of Mexico northward into the Plains,
Mississippi/Tennessee/Ohio Valleys, and eventually the
Appalachians and Eastern Seaboard. Strong storms are possible,
with the Storm Prediction Center outlook showing some severe
threat for parts of the southern Plains into the Lower Mississippi
and Tennessee Valleys and vicinity on Wednesday and Thursday.
There could also be flash flooding concerns where heavy rainfall
occurs, possibly in similar regions and into the Southern
Appalachians. Continue to monitor forecasts as uncertain details
of these potential threats become better refined. At the same
time, expect a band of snow in the colder air on the northwestern
periphery of the system. The best potential for meaningful
accumulations currently extends from central parts of the Plains
and Midwest/Middle Mississippi Valley into the Great Lakes region
and interior New England, while mixed precipitation/ice cannot be
ruled out in the transition zone between the snow and rain.
Totals/location of any snow will be very sensitive to precise
strength and track of the system, and wintry weather could be
within a fairly narrow band. Strong winds may be possible in the
gradient between the surface low and high pressure to the
northwest, and then possibly along parts of the East Coast within
the southerly flow ahead of the system. Recent trends toward low
pressure being weaker and faster, at least from the Plains through
Ohio Valley/Great Lakes, could temper snowfall and wind speeds
somewhat.
Dry conditions should prevail over much of the lower 48 behind
this system. By Friday or Saturday the system along the Canadian
border may bring some snow into the Upper Great Lakes while a
little light precipitation may reach the northern Pacific
Northwest/Rockies. Some moisture may linger over the far
Southeast/Florida but with low confidence in coverage and
intensity of rainfall at this time.
The change and progression of the overall pattern will be evident
in temperatures over the course of next week, as warmer than
average temperatures push eastward through the workweek ahead of
the trough/frontal system and cooler temperatures spread behind
the cold front. Highs of 10-20F above average and lows 15-30F
above normal will be shunted from the Plains on Tuesday into the
Mid-Mississippi and Ohio Valleys (while persisting in the Southern
Plains) on Wednesday, then into the Eastern Seaboard on Thursday.
Some lows in the East could challenge daily records for warmth if
they hold for the calendar day. On the backside of the front,
temperatures should flip to near or below average, first over the
West and spreading to the Rockies, Plains, and Midwest Wednesday
and Thursday before tracking into the eastern third of the country
for the latter part of the week while moderating. Best potential
for temperatures 10-20F below average will be over the southern
half of the Rockies/High Plains and Upper Midwest into the Great
Lakes. An increasing portion of the West and eventually the Plains
should warm up to above average once again by the end of the week.
Parts of the Great Basin and vicinity could see highs at least 10F
above normal.
Rausch/Tate
Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards outlook 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