Valid Saturday June 01, 2019 to Friday June 07, 2019
US Hazards Outlook
NWS Climate Prediction Center College Park MD
EDT May 24 2019Synopsis
: After an amplified pattern over most of
the contiguous U.S. during week-1, zonal flow is forecast for much of the lower
48 through week-1. Mid-level low pressure is likely to develop over the Great
Lakes, suppressing the mid-level high pressure over the eastern U.S. from the
prior period. The heat wave expected to start over Memorial Day Weekend is
likely to linger into early June. Over the central U.S., the perpetually wet
pattern over the Central Plains looks like it will start to wane mid-period.
- Moderate risk of heavy precipitation for
portions of the Central Plains and Middle Mississippi Valley, Sat-Sun, Jun
- Slight risk of heavy precipitation for portions of the Central Plains and
Mississippi Valley, Sat-Mon, Jun 1-Jun 3.
- High risk of excessive heat for portions of Alabama, Georgia and South
Carolina, Sat-Mon, Jun 1-Jun 3.
- Moderate risk of excessive heat for portions of the Southeast, Sat-Tue, Jun
- Slight risk of excessive heat for portions of the Lower Mississippi Valley,
the Tennessee Valley, and the Southeast, Sat-Tue, Jun 1-Jun 4.
For Monday May 27 - Friday May 31: WPC Days
3-7 U.S. Hazards For Saturday June 01 - Friday
As we round out the week for our hazards forecast, the 06z GEFS
upper-level pattern finally has fallen in line with what the ECMWF has been
forecasting all week. Due to this evolution, there is more confidence in
today's forecast on the 500hPa height pattern and its likely impacts. Both
models now indicate that negative height anomalies will likely be over the
Great Lakes with the bulk of the trough northward into Canada. The ridge over
the eastern US during the prior period is forecast to be suppressed southward
due to this troughing, weakening the positive height anomalies and keeping them
confined mostly to the Southeast. Zonal flow is predicted to dominate for most
of the period over the CONUS.
With the weak ridging over the Southeast through the early half of the
period, the models show good agreement of this heat wave for the region lasting
through the first few days of June. As has been messaged for the past few days,
we expect a dry heat prior to the period and early on, mainly through day 8.
Apparent temperatures should be close to dry bulb temperatures, and could be
near 100F. As we continue further into week-2, dew points are forecast to begin
to rise and humidity is likely to take a role in escalating the apparent
temperature or heat index. With the now closer ridge placement over the central
Gulf Coast, both the ECMWF and GEFS show good agreement on the duration and
placement of the warmest temperatures; however, the GEFS does not forecast heat
quite as extreme as the ECMWF. Again, we are favoring the ECMWF solution for
this forecast due to the run-to-run consistency throughout this week. The high
risk for excessive heat over southern Alabama, Georgia and South Carolina is
valid from June 1-June 3, where the greatest chance for around 100F is focused.
A broader moderate risk is forecast until June 4th for the Deep South, while a
slight risk for the same time period is extended north through Southern
Virginia and the central Gulf Coast. With the lack of precipitation over the
next two weeks and the duration of this heat event, there is a possibility of
flash drought development in parts of the region, especially in the high and
moderate risk regions.
Prior to this period, a ridge-trough upper-level pattern is forecast over
the CONUS, leading to a mean baroclinic zone aligning from the Central and
Southern Plains. The upper-level pattern is expected to become zonal over the
Central U.S. early in week-2, but surface lows are forecast over the High
Plains and drop over the Central and Southern Plains into the middle
Mississippi Valley for the first half of the period. A moderate risk of heavy
precipitation is forecast the central Plains, from northeast Texas toward
eastern Missouri for June 1- June 2, where the probabilistic tools are
indicating a 40% chance for rainfall totals over 1 inch. A wider slight risk is
forecast further north through portions of the Midwest, June 1-June 3. Much of
the region highlighted for both the slight and moderate precipitation risks is
currently at 95-99 percentile for soil moisture with the anomalously high
amount of rainfall it has received this spring. The deluge of precipitation
that has plagued the Central Plains for the past few months makes the region
extremely vulnerable to flooding, so these additional rains are likely to
trigger river and flash flooding. There should be at least a break to this
persistent wet pattern for the Central Plains for that latter half of week-2.
The upper-level trough forecast over the Aleutians at the beginning of
week-2 is projected to propagate along the southern coast, weakening the
widespread upper-level ridging over mainland Alaska. The South Coast and
Aleutians are likely to have an active storm track through week-2, with the
strongest system currently forecast for the beginning of June. However,
rainfall amounts and winds from this system are still expected to remain below
our hazardous criteria. The influence of this trough will likely wane toward
the end of the period and weak upper-level ridging is forecast to build
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