Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 345 AM EDT Sun Jun 27 2021 Valid 12Z Sun Jun 27 2021 - 12Z Tue Jun 29 2021 ...Historic and dangerous heat wave to continue throughout the Northwest... ...Heavy rain could lead to additional instances of flash flooding over the next few days from the Southern Plains to the Great Lakes, as well as portions of southwest Louisiana and the Upper Texas Coast... ...Much above average temperatures found across the Northeast to end the weekend... After record-breaking heat was felt over the Pacific Northwest and Northern Great Basin on Saturday, even hotter temperatures are forecast today and Monday throughout the region. The same intense upper-level ridge responsible for the ongoing heat wave is expected to inch eastward along the U.S.-Canada border through Tuesday morning. This will allow for several more days of dangerous heat across the northwest corner of the country, as well as parts of western Nevada and California. High temperatures are forecast to soar 20-30+ degrees above average in Washington and Oregon, including highly populated areas west of the Cascade Mountains. Highs well into the triple digits will significantly increase the threat of heat related illnesses. Record-breaking warm minimum temperatures are forecast as well, with low temperatures only falling into the 70s ( normally the high temperature during this time of year). Both Seattle, WA and Portland, OR are forecast to break their current all-time high temperature records on Sunday and Monday. In fact, the high temperature forecast of 112 degrees for Portland, OR today would break their previous all-time high temperature record by 4 degrees. Parts of Idaho may also threaten daily and monthly temperature records as heat builds into the region early this week. Excessive Heat Warnings/Watches and Heat Advisories have been issued to highlight the unprecedented and abnormal temperatures for this part of the country. Residents are advised to find air-conditioned areas, drink plenty of water, and avoid strenuous activities. Throughout the central U.S., a stalled frontal boundary will continue to be the focus for scattered showers and thunderstorms through at least the middle of the week. This stationary front currently bisects the country from the Great Lakes to the southern High Plains and is where much of the active weather can be found. Flash flooding remains the biggest concern, as multiple days of heavy rain has led to saturated soil across a large area between Oklahoma and Lower Michigan. A Slight Risk (level 2/4) of Excessive Rainfall has been issued for today from eastern New Mexico to central Illinois. Downpours may also lead to flooding concerns along the Gulf Coast between southwest Louisiana and the Upper Texas Coast today and Monday. Tropical moisture and intense rainfall rates could produce multiple inches of rain in a short amount of time. Lastly, a surface trough located over the western Atlantic Ocean is expected to swing into the Southeast on Monday and could produce scattered thunderstorms and localized heavy rainfall throughout southeast Georgia and coastal South Carolina. Heat and humidity are forecast to build into the Northeast to the end the weekend as a Bermuda high pressure system strengthens over the Atlantic Ocean and ushers continuous southerly winds up the East Coast. Even though it will be incomparable to the heat wave experienced across the Northwest, a few daily high temperature records could be set. High temperatures 10-15 degrees above average are forecast over New New England by Monday, with widespread highs into the low-to-mid 90s expected from the Mid-Atlantic to southern Maine. Heat Advisories have been issued for parts of the area. Snell Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php