Valid Tuesday July 30, 2019 to Monday August 05, 2019
US Hazards Outlook
NWS Climate Prediction Center College Park MD
EDT July 22 2019Synopsis
: As we move into the doldrums of
summer, mid-level pressure patterns over the country are forecast to be mild,
with mostly weak high pressure over the contiguous U.S. Some excessive heat may
creep into the Northeast early in the period, but should be gone by mid-week.
After a brief respite from the above normal temperatures over Alaska in week-1,
they are likely to return to the western portion of the mainland early week-2.
- Moderate risk of excessive heat for portions of
the Northeast, Tue-Wed, Jul 30-31.
- Slight risk of excessive heat for portions of the Mid-Atlantic and the
Northeast, Tue-Thu, Jul 30-Aug 1.
- Slight risk of much above normal temperatures for portions of mainland
Alaska and the Aleutians, Tue-Thu, Jul 30-Aug 1.
- Flooding possible across portions of the Central and Southern Rockies, the
Central Great Basin, and the Southwest.
For Thursday July 25 - Monday
July 29: WPC Days 3-7 U.S.
Hazards For Tuesday July 30 - Monday
The week-2 time period looks to be fairly quiet over the
majority of the country, with mid-level ridging overspreading the lower 48.
Upstream, a mid-level trough is likely over western Canada, with another
ridging over the northern Pacific through most of week-2. Models show good
agreement with the mid-level height pattern through Week-2, though the impacts
from this pattern are expected to be minimal.
The mid-level high pressure over the CONUS is expected to be weak over the
majority of the country, though it may amplify over the Northeast early in the
period. Both the GEFS and ECMWF probabilistic tools indicate a 20-60% chance of
temperatures exceeding the 85th climatological percentile over the Northeast,
with maximum temperatures forecast to remain around 90 degrees F. However, a
plume of moisture is also forecast over the region, which is likely to drive up
heat indices near 95 degrees F. A moderate risk of excessive heat is forecast
for the northern part of the region, including Maine, New Hampshire and
Vermont, for July 30-31, where air conditioning is not as widespread and the
population is more vulnerable to the impacts of heat waves. A slight risk for
excessive heat is highlighted for the wider 20% chance region for July 30-Aug 1.
Late week-1 and early week-2, a brief pause is forecast for Southwest
Monsoon activity. The Eastern Pacific basin is showing possible tropical
cyclone formation in some models in Week-2, indicating the region is likely to
have enhanced convection and moisture early. This enhanced moisture flow out of
the eastern Pacific should renew monsoon activity mid-week, and could lead to
flash flooding for parts of the Four Corners region for the latter half the
period. The majority of the moisture does look like it will be over Arizona,
but could stream northward toward central Colorado.
Mid-level low pressure over the Bering Sea is expected to propagate over
mainland Alaska in the middle of week-1. This will likely interrupt the
persistent above normal temperatures for much of the mainland; however, weak
mid-level ridging is expected to fill in behind the propagating trough early in
the week-2 period. A slight risk for much above normal temperatures is forecast
for the first half of the week, July 30-August 1, but concentrated along the
western coast. Toward the end of the period, this ridging is expected to weaken
further and troughing may be introduced along the South Coast. This weakly
amplified pattern is not expected to produce winds that meet the hazardous
threshold along the western coast of Alaska. The return to above normal
temperatures will likely continue to exacerbate fire weather conditions over
mainland Alaska, with the abundance of available dry fuels. According to the
Alaska Interagency Coordination Center, over 1.66 million acres have burned
statewide (as of July 18th, 2019) since the beginning of the
Forecaster: Christina Maurin
Please consult local NWS Forecast Offices for short range forecasts and region-specific information.
Week-2 Probabilistic Extremes Tool
GFS Ensemble Forecasts