Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
1142 AM EDT Wed Mar 27 2019
Valid 12Z Sat Mar 30 2019 - 12Z Wed Apr 03 2019
...Overview and Weather Highlights/Hazards...
Upper ridging over western Canada will refocus into Alaska to
favor troughing through central/eastern Canada and the Upper
Midwest/Great Lakes/Northeast. A lead low pressure system will
exit through the eastern Great Lakes/St. Lawrence Valley this
weekend as the trailing cold front traverses the s-central and
eastern U.S., lingering across Florida and the Gulf of Mexico.
This system may bring a variety of weather including some weekend
snow from the upper Great Lakes to northern New England and
moderate rainfall and convection ahead of and along the front.
Above average temperatures preceding the front will be replaced by
cooler than average temperatures that will moderate over the
following few days.
A series of southern stream Pacific shortwaves will progress
through the West/Southwest then eastward across the U.S. southern
tier. This may invigorate Gulf of Mexico frontal wave genesis next
week depending on exact timing/strength of the feature aloft and
offshore conditions. Rainfall may be enhanced over parts of
Florida northeastward along the GA/SC/NC coast, but could also
stay just offshore. Upstream, another system will push into the
West Coast early next week which may result in a bit cooler
temperatures amid periods of moderate rain and heavier elevation
snows from the Northwest to the northern Rockies then eventually
onto the Plains.
...Guidance Assessment/Preferences...
The latest 06Z GFS/00Z ECMWF and 06Z GEFS/00Z ECMWF ensemble means
seem to offer reasonably similar larger scale pattern evolutions,
but less than stellar consistency with stream interactions and
timing/strength of a multitude of smaller-scale systems embedded
within the flow. Preferred a composite blend to mitigate this with
a majority deterministic blend to start, transitioning to nearly a
50/50 deterministic/ensemble blend next Wed. This offered a good
starting point for the exiting system this weekend where the
models have come into better agreement as well as over FL and off
the SE coast next Tue/Wed where the 06Z GFS was preferred over the
00Z ECMWF (perhaps too far east) but confidence remained lower
than average there given mixed ensemble trends.
Fracasso/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