Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
304 AM EDT Thu May 31 2018
Valid 12Z Sun Jun 3 2018 - 12Z Thu Jun 7 2018
...Record heat expected across the southern Plains...
Guidance and uncertainty assessment
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The forecast period begins on Sunday with an eastern Pacific
trough, upper level ridge over Texas, and both a northern and
southern stream trough over the Upper Midwest and East Coast,
respectively. The trough over the eastern U.S. becomes more
firmly established through the middle of next week, and the upper
ridge over the southern plains continues to govern the weather
pattern over the central U.S. Shortwave disturbances crossing the
northern tier of the nation around the ridge axis will be the main
foci for precipitation.
The guidance is in excellent agreement regarding the persistent
upper level ridge over Mexico and the southern plains through the
entire forecast period, with the 00Z ECMWF indicating the greatest
northward extent across the Plains. Greater differences reside in
the flow across the northern tier of the nation by the Tuesday to
Thursday time period. The 00Z GFS is initially more amplified
with the eastern U.S. upper low, whilst the 00Z ECMWF keeps the
upper low over the Mid-Atlantic region longer. The CMC is much
farther north with the closed low over eastern Canada. For the
northwestern U.S. trough, differences emerge as shortwave energy
ejects eastward across Montana and the Dakotas, and these details
should become more refined with future model runs.
Weather Highlights and Threats
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The best prospects for noteworthy precipitation across the
continental U.S. will be from the Great Lakes to New England in
association with the upper low and trough, along with a surface
low developing offshore. Right now, it appears the heaviest
rainfall from the oceanic low will be over the open waters of the
western Atlantic. Another area of concentrated showers and storms
is expected across the Dakotas and the Upper Midwest by the middle
of next week as a disturbance crosses near the Canadian border.
In the temperature department, the heat wave across Texas and
Oklahoma is forecast to continue going into next week after a
brief and minor abatement on Sunday north of Interstate 20.
Widespread highs exceeding 100 degrees are expected as far north
as Kansas early next week, and a few locations may approach 110
degrees over western Texas. Some record high temperatures are
likely during this time. Above normal temperatures are also
expected across the Rockies and extending northward across the
north-central U.S. Some relief from the hot weather can be found
for the Northeast U.S. and the Pacific Northwest, which will be
under the influence of the upper level troughs. Temperatures near
or slightly below average can be expected for those regions.
WPC medium range forecasts of 500 mb heights, surface systems,
weather grids, quantitative precipitation, and winter weather
outlook probabilities can be found at:
http://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif
http://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif
http://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html
http://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml
http://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
D. Hamrick