Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
407 PM EDT Sun Mar 15 2026

Valid 12Z Wed Mar 18 2026 - 12Z Sun Mar 22 2026

...Record heat expected across the Southwest next week...


...Overview...

An amplified upper level flow pattern will be in place across the
lower 48 for the middle to end of the week, and gradually becoming
less amplified by next Sunday. A highly anomalous upper ridge
situated across the Desert Southwest will deliver summerlike heat
to this region with records expected for multiple days, and
widespread well above average temperatures for most areas west of
the Mississippi River. Upper level troughing should persist across
the eastern U.S. with a new low pressure system potentially
affecting
the Great Lakes and the Northeast by next weekend.


...Guidance/Predictability Assessment...

Model guidance remains in good agreement for the early part of the
forecast period, including the upper high atop the Southwest
reaching over 594dm at times. Downstream, the trough axis should
slowly move from the east-central U.S. midweek into the East late
week. Into next weekend, the initial trough should move into the
Atlantic, but northern stream energy could affect the northeastern
quadrant of the U.S. along with possible surface low pressure.
These features are considerably more uncertain. GFS runs have been
faster at moving this energy into and through the Northeast. 00Z EC
and CMC runs were on the slower side of the AI models/ensemble
means middle ground consensus, but the 12Z EC and CMC are a bit
faster than their older runs. There is a lot of run to run
inconsistency so expect future forecast changes. The WPC forecast
was based on a multi-model blend early, but used more ensemble
means and excluded the GFS from the blend by the late period due
to the northeastern U.S. model differences.


...Weather/Hazards Highlights...

Warm to hot temperatures are forecast to break March records
across much of the southwestern U.S. mid to late week as a massive
upper ridge builds in, peaking in intensity Thursday into Friday.
Highs are forecast to soar past 100 degrees for the first time this
season (and earliest on record) for the lower elevations of
southern California (away from the coast) and Arizona. Numerous
daily records will be broken by the middle to end of the week, and
many monthly March records are also likely. Extreme Heat Watches
are already in effect to account for this and also for how early in
the season this is. Widespread warmer than average temperatures
will also be a concern across much of the Intermountain West and
expanding east to the western High Plains for the second half of
the week, with highs likely to be well into the 90s across western
Texas and much of New Mexico. Readings overall are likely to be
20-30 degrees above mid-March levels from the Southwest up to the
western Dakotas.

A much colder air mass will settle across the East Coast region
for the middle of the week with a Canadian surface high in place
after the passage of the strong cold front, with readings more
typical of January instead of mid-March. Frost and freezing
conditions are possible across the Southeast where vegetation could
be sensitive. There should be a gradual moderation in temperatures
towards the end of the week as the surface high moves offshore.
Rain and inland snow across the northern Mid-Atlantic and the
Northeast could make a return in time for next weekend as the next
storm system approaches from the Great Lakes, although
uncertainties remain.

For the Pacific Northwest, an atmospheric river will be quite
persistent into British Columbia, but will shift/expand into
Washington in particular at times. The precipitation type should
mostly be rain in the warm pattern. Because of the persistence of
the AR after an already wet pattern in the short range, Marginal
Risks are in place for the Day 4/Wednesday and Day 5/Thursday EROs,
with similar integrated vapor transport (IVT) values as the Day
2-3 period and wetter soils by then. A front could enhance the IVT
even further on Thursday. Periods of rain and mountain snow are
also likely in the northern Rockies. On the other side of the
country showers and some thunderstorms are possible across southern
portions of Florida through midweek before a front pushes away.
Maintained a Marginal Risk for southeastern Florida in the Day
4/Wednesday ERO, even though it is uncertain if heavy rain amounts
will be onshore. Other parts of the country should remain mostly
dry.


Tate/Hamrick


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 forecast (QPF), excessive rainfall
outlook (ERO), winter weather outlook (WWO) probabilities, heat
indices, and Key Messages can be accessed from:

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/#page=ero
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml
https://www.wpc.ncep.noaa.gov/#page=ovw