Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
1200 PM EDT Sat Jun 02 2018
Valid 12Z Tue Jun 05 2018 - 12Z Sat Jun 09 2018
...Heat wave from the Desert Southwest to the south-central U.S...
...Pattern overview and guidance/predictability evaluation...
Model and ensemble guidance offer a similar and persistent larger
scale pattern over the nation as highlighted aloft by significant
mean troughs off the northwestern U.S. and downstream over the
East that sandwich an amplified/hot Southwest/s-central us ridge.
Recent guidance has trended a bit toward a bit more amplitude and
pattern longevity. This trend seems reasonable. The depiction and
interactions of a multitude of mid-smaller scale systems embedded
with the flow however is proving to be quite problematic days 3-7
and forecast uncertainty with these is producing significant run
to run model issues. This is particularly evident with
disturbances tracking across the northern tier of the U.S. around
the northern periphery of the upper ridge and into the eastern us
mean trough position. These disturbances and associated height
falls will become a local focus for potentially heavy rainfall.
Overall, the WPC medium range product suite was primarily derived
from a composite blend of the 00 UTC GFS/ECMWF and 00 UTC
GEFS/NAEFS/ECMWF ensemble means. 00 UTC guidance seemed to cluster
best overall and maintain max continuity in this pattern.
...Weather highlights and hazards...
Precipitation can be expected from the north-central states to New
England with the upper low and trough, along with a surface low
developing offshore. 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. Model guidance is also signaling possible mesoscale
convective systems (MCS) developing from the south-central plains
and propagating southeast in northwest flow aloft early in the
week.
A potent mid-upper level ridge over the southwest to south-central
U.S. will support a heat wave from the Desert Southwest to the
south-central U.S where daily maximum temperature records will be
threatened.
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
Schichtel