Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
1154 AM EDT Sun May 19 2019
Valid 12Z Wed May 22 2019 - 12Z Sun May 26 2019
...Overall Weather Pattern...
It remains evident that the upper level pattern across the
continental U.S. will stay amplified and slow to change next week.
A hot upper level ridge over the southeast U.S. becomes anchored
over the region and gradually becomes stronger for the second half
of the upcoming work week. Across the western U.S., a large scale
upper trough will be dominant as multiple shortwave perturbations
keep conditions cool and unsettled/wet. This will also be slow to
move given the expected development of an omega block type pattern
upstream over the eastern Pacific. Lead main weather features
include a strong low pressure system for the Plains and Upper
Midwest mid-week, followed by weaker lows and slow moving fronts
from the Southwest to the Northeast U.S. later in the week on the
western and northern periphery of the Southeast ridge.
...Models and Preferences...
The 06 UTC GFS and 00 UTC ECMWF/UKMET seem in good agreement
Wed-Fri and a composite seems reasonable. By next weekend, the GFS
still shows weaker upper level ridging expanding from the
southeastern U.S. compared to the guidance consensus and
especially the ECMWF. The GFS has more run to run continuity
issues than the ECMWF. Given uncertainties and trends, the WPC
product suite was derived from compatable 06 UTC GEFS/00 UTC ECMWF
ensemble means and 00 UTC ECMWF.
...Weather Highlights and Hazards...
The main things that will make weather headlines for the second
half of the week and extending into next weekend will be the
anomalous heat and humidity building across the southeastern
quadrant of the nation, the unseasonably cool weather expected for
the interior western U.S. and northern plains, and the ongoing
threat of heavy rainfall and potential severe weather eminating
from the central U.S. High temperatures are forecast to be on the
order of 10 to 15 degrees above late May averages from the Midwest
to the Southeast U.S., with the hottest readings expected for the
Friday to Sunday time period. There is a good chance that the
first 100 degree temperatures of the season could be realized
across inland portions of southern Georgia and South Carolina. The
opposite will hold true for the unsettled western U.S. under the
influence of the upper level trough and periods of widespread but
more modest precipitation/elevation snows, with daytime highs of
15 to 25 degrees below normal for mid-week, and then moderating to
5 to 15 degrees below normal by the end of the forecast period.
Heavy rain will likely be an issue again for parts of the central
plains and Midwest with the stalled frontal boundary in place for
the end of the week and into the weekend. There are some
differences in the model placements of the heaviest QPF axis, but
the consensus is for the heaviest rain to develop from northern
Texas to Iowa with the potential for flash flooding. Strong to
severe thunderstorms are also likely in this same general area.
D. Hamrick/Schichtel
Additional 3-7 Day Hazards information can be found on the WPC
medium range hazards chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php
WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation, winter weather outlook probabilities
and heat indices are at:
https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif
https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html
https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml