Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
317 PM EDT Sat Jun 26 2021

Valid 00Z Sun Jun 27 2021 - 00Z Tue Jun 29 2021

...A Historic Unprecedented Heat Wave will grip the Northwest into next
week...

...Heavy Rains, Flash Flooding and Severe Thunderstorms possible from the
Southern High Plains into the Mid Mississippi Valley and Mid West...

...Much above average temperatures expected to develop across the
northeast quarter of the nation Sunday, continuing into next week...

An anomalously strong mid to upper level ridge will move little over the
next two days and remain along British Columbia/Washington State border
area.  This will be the driver for a historic and unprecedented heat wave
that will grip the Northwest for the remainder of this weekend and
continue well into the upcoming week.  Numerous record high temperatures
and record high minimum temperatures are likely to be set over the next
several days across the Northwest from northern California/northwest
Nevada, across much of Oregon and Washington State.  The expected record
high temperatures will not only be for the day, but also for the month of
June and all time.  All time record high temperatures likely to be broken
over the next few days in Seattle, Washington and Portland, Oregon with
forecast temperatures of 110 degrees in Portland on Sunday, breaking the
all time high of 107 degrees ,and a forecast high of 107 degrees in
Seattle on Monday breaking the all time high of 105 degrees.  Much of this
area will see high temperatures 30 to 35 degrees hotter than average and
morning low temperatures  20 to 25 degrees warmer than average over the
next several days.   In many locations, the morning lows will be greater
than the average high temperatures illustrating the anomalous nature of
this historic heatwave.   Excessive Heat Warnings are currently in effect
across Washington State, Oregon, much of Idaho and portions of
California/western Nevada and will likely remain in place going into this
week.

While the Northwest remains stuck in a very hot and dry pattern, the
opposite will be true across portions of the mid section of the nation
from the Southern High Plains into the Mid Mississippi Valley and Mid
West.  The upstream anomalous closed high over the Northwest will also
support a persistent upper level trof across these areas and nearly
stationary frontal boundary stretching in a southwest to northeasterly
direction across these areas.  This will support the potential for
widespread heavy rains, localized flash flooding and severe thunderstorms
in the vicinity of this stationary front Sunday and Monday.   Across the
Central to Southern High Plains, high temperatures are expected to be 20
to 25 degrees colder than average from southeast Wyoming, through
Colorado, New Mexico, western Texas, far western Kansas and western
Nebraska.

While paling in comparison to the record northwestern heat, hot
temperatures are also expected to develop Sunday from the Ohio Valley,
into the Mid-Atlantic and New England.  High temperatures are expected to
be 10 to 15 degrees above average by Monday with these temperatures
approaching record highs in places from southern New England into the
coastal Mid-Atlantic.

Oravec