Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
134 PM EST Tue Feb 15 2022
Valid 12Z Fri Feb 18 2022 - 12Z Tue Feb 22 2022
1900 UTC Update...
The latest 00z/06z model cycle continues to show above average
agreement through the entire period on the large scale, with some
lingering uncertainties in the smaller scale details which mostly
show run to run variability anyways. Models have remained mostly
consistent with their previous runs and so, no major changes were
needed for todays update to the WPC medium range product suite.
The only notable change to previous continuity was a slight
northward shift in the QPF axis across the Deep South early next
week, although given the longer time range, remains rather
uncertain anyways. Todays blend consisted of the updated
deterministic model runs for days 3-5, with some incorporation of
the ensemble means on days 6-7 to help mitigate the detail
differences. See previous discussion below for model evaluation
details and associated sensible weather threats.
Santorelli
Previous discussion issued at 0700 UTC...
...Overview...
Low pressure and a strong cold front along with its associated
precipitation will be exiting the East Coast on Friday, behind
which northern stream energy will push a clipper system with some
snow near the Great Lakes region. Then early next week, troughing
is forecast to develop in the West and slowly track eastward along
with a frontal system. Precipitation chances should increase in
the West with this pattern and spread into the central U.S. once
again by next Monday and Tuesday, with the possibility of northern
tier snow and southern U.S. rain.
...Guidance Evaluation/Predictability Assessment...
Recent model guidance shows good agreement overall with the large
scale pattern even through early next week, with some typical
differences in the smaller scale details. 12Z/18Z models remain
fairly well clustered with the strengthening surface low near the
Northeast/southeastern Canada early Friday, along with the track
and strength of the surface low near the U.S./Canadian border
pushing into the Great Lakes region Friday into Saturday. A
multi-model deterministic blend of the 18Z GFS and 12Z ECMWF, CMC,
and UKMET worked well for these features and kept with continuity
well. A somewhat less certain feature during this timeframe is a
compact shortwave rounding the ridge in the eastern Pacific that
could enter the Pacific Northwest or northern California around
Friday night and move eastward, but with some differences in its
timing and placement, which may not be resolved for a while given
its small scale. However, troughing developing in the West early
next week is coming into somewhat better agreement overall with
its development, depth, and movement, but there are still notable
differences as energy spills in from the low predictability high
latitudes. GFS runs have been the strongest with the trough and
occasionally close off an upper low, but recent runs have backed
off a bit on the strength, closer to the pattern shown by the more
consistent ECMWF. Some phasing differences with potential stream
separation also are causing minor model differences that could
continue to be an issue with the evolution of the troughing. But
overall agreement is better than usual considering the forecast
time range of 6-7 days. The WPC forecast phased in some GEFS and
ECMWF ensemble mean guidance for the latter part of the period,
but still kept a majority deterministic model blend throughout
given the fairly good agreement currently, with the blending
process and some usage of the means taking care of individual
model eccentricities.
...Weather Highlights/Threats...
As the medium range period begins Friday, rain and snow will
mostly be exiting the East Coast along with a low pressure/frontal
system, though showers could linger in Florida. Gusty winds could
also continue on Friday particularly in the Northeast near the
strong surface low. Snow is forecast for the end of the week
across the Great Lakes region with the clipper system, with
generally light to perhaps locally moderate amounts. Mainly dry
conditions are expected elsewhere on Friday, before precipitation
starts to increase in the West over the weekend with the upper
trough coming in. Coastal and valley rain and mountain snow are
likely over the Pacific Northwest spreading into California, the
Great Basin, and the Rockies. Snow is possible for the Northern
Plains as well by early next week, but with low confidence in the
snow axis and amounts at this point. By Monday and Tuesday moist
inflow will return from the Gulf of Mexico, increasing rain
chances across the Gulf Coast states.
The East Coast can expect temperatures to be warmer than average
Friday morning, even setting daily records for warm lows, before
quickly falling behind the cold front, leading to temperatures
right around average for the weekend. Meanwhile, colder than
normal temperatures by 10-20F are expected in the south-central
U.S. to Midwest on Friday and moderating by Saturday. Temperatures
will be warmer than average starting in the Northwest late this
week and spreading into the Plains this weekend, and highs in the
60s are forecast by Sunday as far north as Nebraska and western
Iowa. Warm temperatures shift/spread to the East Coast early in
the workweek while the western half of the nation cools down
underneath the trough. The northern and central High Plains could
see temperatures 15-25F below normal Monday into Tuesday.
Tate
Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards outlook 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