Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
300 AM EDT Mon Jun 18 2018
Valid 12Z Thu Jun 21 2018 - 12Z Mon Jun 25 2018
...Guidance/Predictability Assessment and Weather
Highlights/Threats...
Models and ensembles are in closer agreement with overall pattern
timing and evolution, bolstering forecast confidence, with a
composite trending slightly more progressive with mid-latitude
flow and more amplified northern stream flow over Canada. Central
plains closed trough/low energy Thursday slides east-northeastward
over the east-central U.S. then the northeast late weekend. This
occurs as a kicker shortwave trough pushes inland over the NWRN
U.S. Friday and through the Rockies into the central states.
Guidance has also trended to produce a more developed series of
surface lows to run along a main frontal boundary from the Plains
to the Ohio Valley and Mid-Atlantic. Expect periods of locally
excessive convective complexes/rains to focus along this boundary
and in the warm sector aided tropical moisture influx from the
Gulf of Mexico. Guidance differences are indeed more stark
underneath with the short and medium range heavy rain threat over
Texas associated with a tropical disturbance now over the Gulf of
Mexico. This system in some form is expected to lift over Texas
with parts lingering back toward the Rio Grande Valley. The
operational ECMWF and UKMET still both show a much better defined
system and extremely heavy rainfall, while the GFS and ensemble
means offer much less. Tropical nature and slow translation should
combine to pose a heavy/excessive rainfall threat, leaning WPC QPF
in the direction of the wetter lingering scenarios. Otherwise, the
WPC medium range product suite was primarity derived from a
composite model blend across the mid-latitudes.
Schichtel
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