Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
434 PM EDT Fri Mar 18 2022
Valid 12Z Mon Mar 21 2022 - 12Z Fri Mar 25 2022
...Strong low pressure system will likely produce heavy
rain/severe storms across portions of the southern U.S. and heavy
central Rockies snow by early next week...
...Overview...
The dominant focus of the medium range forecast will be an upper
low expected to track northeast from the Four Corners states
Monday onward, possibly opening up as northern stream energy
phases with it after midweek. This feature will support strong low
pressure that should track from the southern High Plains through
the Great Lakes and New England/southeastern Canada. Expect the
system to spread a myriad of significant and hazardous weather
across the eastern two-thirds of the lower 48, including
potentially heavy snow over the central Rockies and vicinity,
heavy rain from the south-central U.S. to the Ohio/Tennessee
Valleys and Southeast, and severe thunderstorms from Texas through
the Deep South. Some precipitation in the northern fringe of the
moisture shield could be in the form of snow over the
central/eastern U.S. as well. Behind this system a strong upper
ridge will build into the West, bringing mostly dry and warm
weather to the region. The anomalous warmth over the West could
bring record highs to parts of California around Tuesday-Thursday.
Pacific shortwave energy may erode the western ridge somewhat late
in the week.
...Guidance Evaluation/Predictability Assessment...
During the first half of the period, the latest 00Z/06Z
operational model consensus provides a good depiction of
significant features. Guidance maintains the recent tendency to
keep the central U.S. upper low intact into Wednesday as it
reaches the Midwest. There are still noticeable differences with
specifics at the surface but these have lower predictability due
to sensitivity to exact shortwave details aloft. Meanwhile
guidance has become more agreeable with the cyclonic flow over the
Northeast during the first half of the week, with solutions
generally gravitating to an evolution between the extremes seen in
earlier GFS and ECMWF clusters. Meanwhile the upper ridge building
into the West should be strongest during Tuesday-Wednesday.
The latter half of the forecast still contains various
uncertainties, in particular exactly how Pacific shortwave energy
will dampen the northern part of the western North America ridge.
These details affect how southern tier Canada flow may interact
with upper low reaching the Midwest by midweek, and then how much
if any flow separation may occur in the vicinity of the Northeast
U.S. and southeastern Canada plus timing of the rest of the trough
over the lower 48. Thus far the ensembles suggest that the 00Z
GFS/CMC may be overdone with how much separation occurs over
eastern North America and the 06Z GFS has partially nudged back
toward consensus. Farther south/southwest, the majority says the
upper trough should extend back into northern Mexico into late
week. The 00Z ECMWF could be a bit fast, though much improved over
its prior run and not extreme versus its ensemble members. The 00Z
CMC leans to the weaker side of the full spread with the western
ridge late in the period. Guidance comparisons led to trending the
operational model blend toward 40-50 percent 06Z GEFS/00Z ECMWF
means by days 6-7 Thursday-Friday with lingering model input from
the 06Z GFS/00Z ECMWF.
...Weather Highlights/Threats...
Ample Gulf of Mexico moisture flowing into the surface/upper-level
lows tracking northeastward over the central U.S. will lead to
widespread rain and thunderstorms for the Southern Plains and
Lower Mississippi Valley early in the week, spreading eastward
into the Ohio and Tennessee Valleys and Southeast by around
midweek. Per the Storm Prediction Center, storms could be severe
in eastern Texas Monday and across the Gulf Coast states as the
week progresses. Furthermore, heavy rain is likely to cause areas
of flash flooding particularly due to heavy rain rates Monday into
Wednesday, and Slight Risk areas are indicated near the
Ark-La-Tex/eastern Oklahoma and for the Lower Mississippi
Valley/Mid-South region for Days 4 and 5 in the experimental WPC
medium range Excessive Rainfall Outlook. Rain should spread into
the Eastern Seaboard around Thursday. Additionally, heavy snow is
increasingly likely for the central Rockies Monday, with some
potential for snow to spread into the High Plains as well. An area
of enhanced rainfall also appears likely from the Central Plains
into Middle Mississippi Valley/Midwest, though with lesser totals
than those expected farther southeast. There is a gradual
improvement in agreement that at least some precipitation should
reach areas from the northern parts of the Plains through the
Northeast, with some of this moisture possibly producing snow.
Probabilities for at least a quarter inch liquid in the form of
snow are still relatively low though. In the West, the Pacific
Northwest should see an episode of rain/high elevation snow on
Monday and possibly a little light/scattered activity later in the
week. Otherwise the West will see dry weather through the week.
The strong upper ridge building into the West will lead to a broad
area of highs 10-20F above normal Tuesday-Friday with slightly
higher localized anomalies possible. Best potential to reach daily
record highs will be over California during Tuesday-Thursday.
Dampening of the northern part of the upper ridge by Friday may
start a gradual cooling trend over some areas but also spread the
warmth across the eastern Great Basin and Southwest/Four Corners
region. Leading upper level troughing will support high
temperatures 10-20F below average across the Intermountain West
Monday and the central/southern High Plains Tuesday and Wednesday.
The cooler air should moderate closer to normal by the latter part
of next week and could trend moderately above normal Friday. Ahead
of the Plains storm, the Midwest will see warmer than average
temperatures by around 20F or so on Monday and generally warmer
than normal conditions are likely across much of the eastern third
of the U.S. for most of the week. Isolated record highs are
possible over parts of Florida Tuesday-Wednesday.
Rausch/Tate
Hazards:
- Heavy snow across portions of the Central Rockies and Central
High Plains, Mon, Mar 21.
- Heavy precipitation across portions of the Central High Plains,
Mon, Mar 21.
- Severe weather across portions of the Southern Plains to the the
Lower Mississippi Valley, Mon, Mar 21.
- Heavy rain across portions of the Southern Plains to the Lower
Mississippi Valley, Mon, Mar 21.
- High winds across portions of the Central and Southern High
Plains, Tue, Mar 22.
- Severe weather across portions of the Lower Mississippi Valley,
the Tennessee Valley, and the Central Gulf Coast, Tue, Mar 22.
- Heavy rain across portions of the Lower Mississippi Valley, the
Middle Mississippi Valley, the Tennessee Valley, the Ohio Valley,
and the Central Gulf Coast, Tue, Mar 22.
- Severe weather across portions of the Southeast, Wed, Mar 23.
- Heavy rain across portions of the Southeast, the Southern
Appalachians, and the Mid-Atlantic, Wed, Mar 23.
- Flooding possible across portions of the Middle Mississippi
Valley and the Great Lakes.
- Much above normal temperatures across portions of California,
Tue-Thu, Mar 22-Mar 24.
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
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