Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
210 AM EST Sun Feb 13 2022
Valid 12Z Wed Feb 16 2022 - 12Z Sun Feb 20 2022
...Mid-late week system to bring potential for heavy rain and
severe weather from the south-central to eastern 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 an upper
trough/low likely centered near the Four Corners early Wednesday,
which will track eastward and phase with 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 and
Thursday. 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, before additional
troughing enters the Pacific Northwest by Sunday.
...Guidance Evaluation/Predictability Assessment...
Model guidance continues to show fairly good agreement with the
overall pattern described above, but with detail differences that
could be impactful to the sensible weather. The bulk of guidance
still shows evidence to maintain the closed low within the western
U.S. trough to start the period early Wednesday, then quickly join
with northern stream troughing in the central U.S. by Thursday.
Over the past day or so, guidance has trended toward 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. The 12Z CMC continued its position southwest of other
solutions with the western upper system and then shear it out more
dramatically farther east, resulting in a weaker surface pattern.
The newer 00Z CMC is in somewhat better alignment with its upper
level pattern but its surface low may be displaced south of a
preferred position. An average of GFS/ECMWF/UKMET runs from the
12Z/18Z cycles once again served to reflect these model trends
toward a slightly faster front and initially weaker low but also
maintain a measure of continuity from the previous forecast.
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 by late in the week, with GFS runs
strongest and ECMWF runs weakest with this feature, and confidence
remains minimal with the specifics. However there is decent
agreement on an upstream shortwave/cold front approaching the
Pacific Northwest over the weekend.
Preferences for the system over the West and continuing eastward
favored starting the forecast with the 12Z/18Z GFS and 12Z ECMWF
and UKMET for about the first half of the period. Then the blend
incorporated some of the 18Z GEFS/12Z ECMWF means by the weekend
given decreasing confidence in some details.
...Weather Highlights/Threats...
Showers and thunderstorms will become widespread over the central
U.S. on 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 spreading toward much of
the Eastern Seaboard on Thursday and Thursday night. Current
forecasts show the Southern Appalachians could see particularly
high rainfall totals given terrain enhancement there. 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 given
that wintry weather could be within a fairly narrow band, and a
faster forecast low/front track may temper snowfall amounts. Gusty
winds are possible with the system as well, and at this point
appear most likely near the Northeast coast on Thursday night in
strong southerly flow ahead of the quickly strengthening surface
low.
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 light
precipitation may reach the northern Pacific Northwest/Rockies by
Friday, which could increase in amounts by Saturday. 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 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 southern half of the Plains into the Mississippi
and Ohio/Tennessee Valleys Wednesday into the Eastern Seaboard on
Thursday. Daily records could be set for some locations,
especially for warm lows in the East on Thursday, while a few
record high maxima could be challenged as well. On the backside of
the front, temperatures should flip to near or below average,
shown in the Great Basin/Rockies and north-central U.S. on
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, while central parts of the Plains could
even reach 20F above average with temperatures in the 60s by
Sunday.
Tate/Rausch
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