Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
247 AM EDT Fri Oct 04 2019
Valid 12Z Mon Oct 07 2019 - 12Z Fri Oct 11 2019
...Another round of cold/snow for portions of Montana next week...
...Overview...
Troughing will exit the Northeast but enter the Pacific Northwest
early next week as a fairly amplified but progressive flow pattern
continues. Western troughing will push through the central states
next Thu/Fri with much below average temperatures in its wake.
...Guidance/Uncertainty Assessment...
The 12Z/18Z GFS and 12Z ECMWF offered reasonable clustering near
their ensemble means and each other such that a blend sufficed
through the period. Typical differences within expected errors for
3-7 day lead times suggested at least average confidence. By later
next week, the ECMWF and its ensemble members were generally
quicker with the central CONUS trough than the 18Z GFS/GEFS but
there was quite a bit of east-west spread by next Fri depending on
the wavelength amplitude of the member--the slower members (with a
deeper trough or closed low lingering in the West) were generally
slower downstream with another closed low near the New England
coast (like the 12Z Canadian). For now, GFS/ECMWF/ensemble
consensus was progressive enough to keep the surface front moving
through the week.
...Weather Highlights/Threats...
Cold front nearing the East Coast will provide a focus for locally
modest to heavy rainfall from the central Appalachians into the
Northeast Monday. This rainfall will be beneficial over areas
currently experiencing drought of varying intensity. Brief warm-up
(70s on the coastal plain, 60s inland) will be replaced by near
average temperatures for the rest of the week in much of the East.
By Tue-Thu the front should settle over the Florida Peninsula and
possibly lead to some rainfall enhancement in its vicinity.
The upper trough dropping southeastward from the Gulf of Alaska
will bring a period of rain and initially higher elevation snow to
the Northwest during the first half of next week with highest
totals over favored westward-facing terrain. Winter Weather
Outlook snowfall probabilities exceed 70% (> 2-3" snow) over
higher elevations on Tuesday in western Montana around Glacier
Park. The cold air behind the leading surface front will progress
southward and eastward which will lower snow levels toward or into
the valley locations of the rest of Montana. High temperatures are
likely to be at least 10-20F below average over the northern
Rockies/Plains on Wed and over much of the northern-central Plains
by Thu. This will spread southward to Texas and eastward to the
Mississippi Valley by Friday but perhaps with less intensity.
Rainfall will expand and perhaps become locally heavy over the
mid-Mississippi Valley late in the period depending on moisture
inflow from the Gulf.
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