![National Oceanic and Atmospheric Administration](/build/images/header/noaa.d87e0251.png)
![National Weather Service](/build/images/header/nws.4e6585d8.png)
![United States Department of Commerce](/build/images/header/doc.b38ba91a.png)
Prognostic Meteorological Discussion
Issued by NWS
Issued by NWS
Versions:
1
001 FXUS21 KWNC 181916 PMDTHR US Hazards Outlook NWS Climate Prediction Center College Park MD 300 PM EDT June 18 2024 SYNOPSIS: A brief respite from excessive heat is favored for much of the northern contiguous states (CONUS) during the early part of week-2, as several areas of mid-level low pressure progress across the country. During the second half of week-2, high heat and humidity are favored to return to the Ohio Valley, southern Great Lakes, northern and central Appalachians, and Mid-Atlantic region. Across the western Gulf Coast region, there is an increased risk of heavy precipitation with flooding possible, though much depends on the possible formation of another tropical cyclone over the Bay of Campeche. HAZARDS Slight risk of excessive heat for much of the south-central and southeastern CONUS, Wed-Tue, Jun 26- Jul 2. Slight risk of excessive heat for the Ohio Valley, portions of the southern Great Lakes region, the northern and central Appalachians, and the Mid-Atlantic, Sat-Tue, Jun 29-Jul 2. Slight risk of heavy precipitation over the western Gulf Coast region, Wed-Tue, Jun 26- Jul 2. Flooding possible over much of the western Gulf Coast region. Slight risk of heavy precipitation for southern Florida, Wed-Tue, Jun 26-Jul 2. Slight risk of heavy precipitation in the vicinity of the Upper Mississippi Valley, Wed-Fri, Jun 26-28. Flooding possible in the vicinity of central and southern Minnesota. Slight risk of high winds for the High Plains region, Wed-Fri, Jun 26-28. Rapid Onset Drought risk for much of the Mid-Atlantic and interior Carolinas. Rapid Onset Drought risk for the Ohio Valley. DETAILED SUMMARY FOR FRIDAY JUNE 21 - TUESDAY JUNE 25: https://www.wpc.ncep.noaa.gov/threats/threats.php FOR WEDNESDAY JUNE 26 - TUESDAY JULY 02: One or two cold fronts are forecast to move across much of the northern one-third to one-half of the CONUS during the early portion of the week-2 period, accompanied by cooler temperatures and reduced humidity. The break from the heat, however, is favored to be short-lived, as another mid-level ridge is expected to develop and strengthen over northeastern parts of the Lower 48 states during the second half of week-2, with a return to high heat and humidity. This is supported by the three ensemble mean model solutions (GEFS, ECENS, and Canadian (CMCE)). The 0z ECENS solution predicts seasonal or slightly above-normal temperatures across New York and New England, with high temperatures ranging from the 70s near the Canadian border to mostly 80s for southern parts of this region. Temperatures could approach 90 deg F in a few interior portions of the Northeast. The ECENS and CMCE ensemble means predict the mid-level ridge axis to be near the central Great Lakes region, which allows for back-door fronts and cooler marine air to influence the northern Atlantic coastal plain. Over much of the south-central CONUS, little to no relief of the heat and humidity is anticipated. Accordingly, there is a slight risk of excessive heat for this broad area for the duration of week-2. A skill weighted hybrid excessive heat tool (that considers forecast values of both actual air temperature and the effect of humidity) depicts much of this region (east of the Rockies) experiencing heat index values of 105 deg F or greater. West of the Rockies, where humidity is often less of a factor, actual air temperatures in the lower elevations of Utah are predicted to reach the mid-upper 90s during the period. A storm system from the Gulf of Alaska is predicted to move into the Pacific Northwest early in week-2, gradually reducing daytime high temperatures across a significant portion of the northwestern CONUS. For precipitation, there is a slight chance for heavy precipitation across the vicinity of the Upper Mississippi Valley, Jun 26-28. Precipitation guidance from the Probabilistic Extremes Tools (PETs), the uncalibrated ECENS, and the synoptic pattern are generally consistent with this feature. Flooding is also possible in much of this area, as precipitation has been occurring frequently, and soil moisture values remain high. A slight risk for heavy precipitation has also been posted for the western Gulf Coast region and southern Florida based on objective precipitation guidance, with the PETs favoring at least one-inch over a 3-day period. The PETs extended the slight risk as far west as the upper Texas coast, but this risk area was subjectively extended southward to the Mexican border due to concerns of an additional tropical cyclone potentially developing in the week-2 period across the Bay of Campeche and tracking north or northwestward. Flooding is also possible for coastal areas of Texas and Louisiana, in large part due to a combination of very heavy rainfall amounts anticipated during the earlier week-1 period and the possible follow-up with another tropical cyclone in week-2. Two areas of Rapid Onset Drought (ROD) are highlighted on todays Hazards map. One area includes much of the Mid-Atlantic region and interior Carolinas, and the other area includes much of the Ohio Valley. Much of these areas have below-normal soil moisture values, and are experiencing 1-4 inch 30-day precipitation deficits at this time. The expectation of high heat and high evapotranspiration (ET) rates for the next 2 weeks make this region vulnerable to rapid onset drought. The various PET tools agree on high winds (20-25 mph) across the High Plains during the first three days of the Outlook period. This is attributed to enhanced downslope flow over the eastern foothills of the northern and central Rockies and adjacent High Plains. In the Southwest, the mid-level atmospheric circulation is gradually moving toward its climatological monsoon circulation, but is not quite there yet. The expected presence of a mid-level trough across the Northwest, and the lack of a well-defined subtropical ridge centered over the Four Corners region, support this idea that the monsoon circulation is still not in place. However, dynamical models forecast increases in regional dew point temperatures over the next two weeks, with places like Phoenix and Tucsons values reaching the upper 50s and low 60s deg F. Typically at the beginning of the climatological monsoon season, the air over the Southwest is still very dry and initial moisture surges into that region often result in precipitation that falls aloft but doesnt reach the ground (i.e., virga). This is also a time that is ripe for dry thunderstorms accompanied by frequent lightning, and locally strong downburst winds, both of which could increase/exacerbate wildfire activity. FORECASTER: Anthony Artusa $$