Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
1157 AM EDT Thu Mar 28 2019
Valid 12Z Sun Mar 31 2019 - 12Z Thu Apr 04 2019
...Overview...
Strong upper ridging over Alaska will drift northwestward into
northeastern Russia next week will favor a westward shift in
troughing over the CONUS--initially over the Great Lakes and
Northeast Sun-Mon then back to the Plains/Upper Midwest next
Wed/Thu. Troughing in the northeastern Pacific will continue to
send systems into the West underneath the Alaskan upper high,
focused around Mon-Tue.
...Guidance Assessment/Preferences...
The models/ensembles generally agreed on the longwave pattern with
differences on timing/strength of the embedded systems. Areas of
concern were 1) over the Gulf Mon/Tue where low pressure is still
forecast to develop along a slowly moving cold front, but
ensembles show a large amount of separating in timing/location of
said low (ECMWF and its ensembles generally slower than the
GFS/UKMET and GEFS. Ensemble signal has been inconsistent so an
intermediate solution was preferred for now. By Tue/Wed, the 00Z
ECMWF/GFS come into better agreement with especially the ECMWF
ensemble mean, so that cluster of solutions was preferred which
was slower than the 06Z GFS/FV3-GFS, keeping it closer to the
Outer Banks but just offshore.
In the West, another system will push through the Great Basin
Tuesday then onto the Plains Wednesday. 00Z GFS seemed to raise
heights too quickly behind this system given the teleconnections
(and most ensembles) that favor at least some troughing to remain
just east of the Rockies. Ensemble means showed this nicely and
was the majority of the preference. With a slowly westward moving
trough axis, this would favor any surface low development to lift
northeastward through the Great Lakes around next Thursday with a
cool shot of Canadian air behind it.
...Weather Highlights/Hazards
Cooler temperatures will spread eastward from the Plains to the
East Coast behind the exiting system on Sunday while rainfall
expands along the central/eastern Gulf Coast into northern Florida
and the Southeast Mon/Tue. Rainfall could be locally heavy
depending on how and where the surface low (or lows) develop(s).
In the West, frontal system will bring rain/snow to Oregon
eastward with a modest precipitable water axis back to Hawai'i. PW
anomalies of +2 to +3 will support some locally heavy
precipitation but progressive movement will limit the duration. As
a northern stream front and Pacific energy interact east of the
Rockies, another area of at least modest precipitation will expand
across the Upper Midwest and western Great Lakes. This may
exacerbate ongoing flooding as rain is expected for most areas
southeast of a ~Rapid City, SD to International Falls, MN line
(per the current forecast) with some snow to the northwest.
Fracasso
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