Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
434 PM EST Thu Jan 27 2022
Valid 12Z Sun Jan 30 2022 - 12Z Thu Feb 03 2022
...Overview...
By the start of the medium range period early Sunday, the deep
system tracking just off the East Coast late this week into the
weekend should reach a position east or northeast of Maine, still
supporting some strong winds even if precipitation tapers off.
This storm will continue moving rapidly away from New England
during the day Sunday. For information on the storm's effects
before early Sunday consult the WPC website for updated Key
Messages and check your local forecast at weather.gov. Through the
rest of the period, the dominant theme will be a significant
pattern change as an upper trough strongly amplifies from the
northeastern Pacific into the western/central U.S. while a strong
ridge builds and then persists over the eastern Pacific, and
another ridge crossing the East Coast Tuesday settles over the
western Atlantic thereafter. This evolution will initially spread
precipitation across the West and then likely produce significant
precipitation farther eastward as a leading front interacts with a
strong flow of Gulf moisture, with the possibility of wintry
weather on the backside of the front. Ahead of the trough, a
southern stream shortwave/upper low may generate some enhanced
rainfall along/north of the Gulf Coast around Monday.
...Guidance Evaluation/Predictability Assessment...
An operational model blend early in the period favoring the
00Z/06Z GFS and 00Z ECMWF and CMC followed by a transition toward
about half the total weight of 06Z GEFS/00Z ECMWF means continued
to provide a good representation of consensus ideas, with mainly
just typical run-to-run detail changes versus previous cycle. For
the storm producing lingering effects over New England, there are
still meaningful differences in the short range due in part to
fine-scale issues with the supporting upper low, so there is still
a fair amount of uncertainty over the exact location/structure of
the storm as of early Sunday. Overall the latest GFS/GEFS mean
continue to be on the faster side and the ECMWF/ECMWF mean are
slowest, conforming to long-historical tendencies.
Meanwhile guidance continues to consolidate for the handling of
the southern stream shortwave/upper low emerging from the
Southwest, with the 00Z UKMET straying faster than most other
solutions. This feature should rapidly shear out beyond the
Plains. Farther west, there are still differences in how some
energy pulls off from the southwestern part of the shortwave
approaching the West Coast Sunday but now with less pronounced
spread than in previous cycles. As the larger scale upper trough
digs into the western/central U.S. Tuesday-Thursday, the ensemble
means and a multi-run average of operational runs suggest above
average predictability for the large-scale feature while
individual members/model runs show embedded detail uncertainties.
Examples of the latter include to what degree flow may separate
near the Four Corners region around Wednesday and the character of
upstream energy dropping into the mean trough by Thursday. GFS
runs have been persistent with a stronger feature for the latter
compared to the ECMWF runs, and these differences do affect the
width of the troughing as well as the axis somewhat, and the
timing of the surface cold front pushing ahead of the trough. The
blend of deterministic and ensemble guidance used for the end of
the period worked as a compromise at this point.
...Weather Highlights/Threats...
Expect strong winds over New England at the start of Sunday to
moderate over the course of the day as strong low pressure tracks
rapidly away from the region. Otherwise the effects of the initial
storm will be in the short range. See the WPC website for latest
Key Messages on the system and additional information in the
Probabilistic Heavy Snow and Icing Discussion, plus check your
local forecast at weather.gov.
The upper trough/low reaching the Southwest by early Sunday should
produce little if any precipitation over that region. However, as
the feature continues eastward, there will be some potential for
locally moderate to heavy rainfall from eastern Texas across parts
of the Gulf Coast region during the first half of the week. Best
potential at this time appears to be over eastern Texas with lower
confidence in details farther east. Some aspects of this event may
hinge on small-scale details not easily resolved very far in
advance. The northeastern Pacific upper trough digging into the
West Sunday-Tuesday will spread moderate amounts of rain and
mountain snow from the Pacific Northwest eastward and
southeastward into much of the Rockies. Highest totals are likely
to be in the Pacific Northwest but should not be too extreme. In
general the forecast remains on track for a significant increase
of coverage and intensity of precipitation over the east-central
U.S. by Wednesday-Thursday as the upper trough emerges from the
Rockies and the leading cold front interacts with a strong low
level feed of Gulf moisture. At this time the best potential for
heaviest rainfall extends across the lower half of the Mississippi
Valley into parts of the Ohio/Tennessee Valleys. Wintry weather
will be possible on the northwest side of the moisture shield,
with at least some potential for meaningful snow from the
central/south-central Plains northeastward through the Great
Lakes. While confidence in a heavy rain area appears better than
average, details with the wintry precipitation in the colder air
may be more dependent on lower-confidence details of ejecting
shortwave energy and frontal waves.
Cold conditions near the East Coast will extend through Sunday
with many areas 10-20F below normal. Subfreezing lows should
extend into portions of Florida and parts of the Florida Peninsula
may challenge daily records for both morning lows and daytime
highs. Much of the Plains will see above normal temperatures
Sunday into the first part of next work week, with some
northern/central areas possibly seeing plus 20F or greater
anomalies on one or two days. This warm air will progress into the
eastern half of the country Tuesday-Thursday, bringing a broad
area of temperatures 10-20F above normal and perhaps greater
anomalies for lows over the Northeast by Thursday. Also during
Tuesday-Thursday much of the West and then into the Plains will
see an episode of chilly temperatures with the Rockies and Plains
seeing the best potential for readings 10-20F below 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
Hazards:
- Heavy precipitation across portions of the Middle Mississippi
Valley, the Great Lakes, and the
Ohio Valley, Wed, Feb 2.
- Heavy rain across portions of the Lower Mississippi Valley and
the Southern Plains, Mon, Jan 31.
- Heavy rain across portions of the Middle/Lower Mississippi
Valley, the Central Appalachians, the
Tennessee Valley, the Central/Southern Appalachians, the
Southeast, and the Ohio Valley, Wed-Thu,
Feb 2-Feb 3.
- High winds across portions of the Mid-Atlantic and the
Northeast, Sun, Jan 30.
- Much below normal temperatures across portions of the Plains,
the Rockies, the Upper/Middle
Mississippi Valley, the Central Great Basin, and the Upper Great
Lakes, Wed-Thu, Feb 2-Feb 3.
- Much below normal temperatures across portions of the Northeast,
the Central/Southern
Appalachians, the Tennessee Valley, the Mid-Atlantic, the
Southeast, the Great Lakes, and the Ohio
Valley, Sun, Jan 30.
- Much below normal temperatures across portions of the Southeast,
Sun-Mon, Jan 30-Jan 31.
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
