Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
333 PM EDT Wed Jun 07 2023

Valid 00Z Thu Jun 08 2023 - 00Z Sat Jun 10 2023

...Hazardous air quality levels will persist across the Northeast and
Mid-Atlantic through Thursday before shifting westward into Ohio Valley on
Friday...

...Heavy rainfall possible throughout central and northern Rockies on
Wednesday; rainfall threat will shift northward into Montana on Thursday
and Friday...

...Below-average temperatures to continue in the East and Southwest, while
Pacific Northwest and Plains stay above-average.

Hazardous air quality and widespread smoky conditions will persist through
Wednesday afternoon and evening throughout the Northeast and Mid-Atlantic
as smoke associated with wildfires in Canada continues to push southward
into the lower 48. As a nearly stationary upper-low churns off the New
England coastline, sustained northerly winds will allow the smoke to
spread southward, with major metro areas such as Boston, New York City,
Philadelphia, and Washington D.C. expected to experience unhealthy air
quality levels for all age groups through Thursday, before winds shift
more easterly, pushing smoke further west into the interior Northeast and
Ohio Valley on Friday. It is important to limit time outdoors, as exposure
to air pollutants can aggravate health problems such as asthma, heart
disease, and lung disease. To ensure proper safety, take breaks when
possible or wear a mask that will help protect you from the smoke. In
addition to the smoke, breezy winds and low humidity over portions of the
Lower Great Lakes and Mid-Atlantic, where conditions remain very dry due
to a recent lack of rainfall, have prompted an Elevated Risk of Fire
Weather from the Storm Prediction Center through Wednesday afternoon.

Elsewhere, there will be numerous chances for heavy rainfall across the
interior Pacific Northwest and Intermountain West through Friday as
anomalous moisture from the Gulf of Mexico continues to stream
northwestward into the region between a closed low across the Great Basin
and an upper-level ridge in the Plains. Wet antecedent soil conditions in
conjunction with isolated heavy rainfall rates approaching 1"/hr in
developing thunderstorms could lead to flash flooding concerns through
Wednesday afternoon across the central and northern Rockies, resulting in
an expansive Slight Risk of Excessive Rainfall for the region. The threat
of heavy rainfall will continue into Thursday and Friday, with the primary
risk area shifting into Montana and Idaho as the upper low pushes
northward. 48-hour rainfall totals across western Montana may approach
1-2", with locally heavier amounts possible as developing thunderstorms
produce rainfall rates of up to 1"/hr, resulting in the issuance of a
Slight Risk of Excessive Rainfall for the region through Friday.

Temperature-wise, with the aforementioned persistent upper-low across the
Northeast, conditions will remain cool through the end of the week with
temperature anomalies of 10-20 degrees below average, as daytime highs
remain in the upper 60s to low 70s. Similarly, most of coastal California
will remain in the 60s while highs will be warmer, but still below
average, in the interior valleys and Desert Southwest, with 80s to low 90s
expected. In contrast, under the ridging across the Plains and Northwest,
temperatures will be as much as 10-20 degrees above average. High
temperatures on Wednesday and Thursday in the Northern Plains and interior
Pacific Northwest will be in the upper 80s to low 90s.


Russell


Graphics available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php