Weather Prediction Center

National Oceanic and Atmospheric Administration

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
247 PM EST Tue Nov 12 2019

Valid 00Z Wed Nov 13 2019 - 00Z Fri Nov 15 2019

... Widespread record cold spreading from the Plains eastward toward the
East Coast...

...Active Lake Effect snows continue downwind of the Great Lakes...

...Persistent warm and dry weather over the West will continue to elevate
fire weather concerns for portions of southern California...

A vast majority of the central and eastern U.S. will have below normal
temperatures has the Arctic airmass spreads from the Plains into the
Ohio/Tennessee Valley and eastward. Hundreds of locations may set new
records during this time. By Wednesday morning, low temperatures in the
teens and 20s will be common along much of the East Coast, the Ohio
Valley, and down as far south as the upper Texas coast, making it feel
like the middle of winter for these areas. Freeze and Hard Freeze warnings
are in effect from the Texas Coast to coastal South Carolina. Temperatures
will begin to warm up on Thursday once the expansive high pressure system
migrates offshore the New England Coast.

Meanwhile, snow currently falling across portions of the Tennessee Valley,
the Appalachians and the Northeast will begin to taper off this evening-
while the lake effect snow will persist into Wednesday morning. Rain,
spanning from Florida to New England, will continue to track
east-northeast offshore this evening. Additionally, an upper-level
disturbance arriving from northern Mexico will increase the chance of rain
along the Gulf Coast as a coastal front forms just offshore.

Rain and snow chances will increase across the Pacific Northwest and the
Interior as an upper-level disturbance moves inland. Amounts are expected
to be on the lighter side as the system quickly passes through the Plains
Wednesday and into the Great Lakes region by Thursday. For the Great
Basin/Rockies region, warmer and drier conditions are expected to prevail
which will maintain an increased risk for spread of wildfires.

Campbell


Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
436 PM EST Tue Nov 12 2019

Valid 12Z Fri Nov 15 2019 - 12Z Tue Nov 19 2019

...Pattern Overview and Guidance/Predictability Assessment...

Upper ridging on either side of North America will favor a series
of troughs progressing across the CONUS.
For days 3-4, an upper trough crossing the southeast causes
low pressure to develop just off the Southeast coast and move
northeastward to off the Mid Atlantic coast by day 5 and off the
New England coast days 6-7. Models cluster in 2 camps, with the
GFS/GEFS Members/Canadian slightly faster in moving the low
northeast and the ECMWF/ECMWF mean/00z UKMET slower. A blended
solution is proposed to mitigate the timing differences.

A Western trough on Friday will progress across the northwest and
northern Rockies and then the northern Plains Sat and into the
upper Great Lakes/mid MS Valley Sun 17 Nov. The southern portion
of the trough amplifies over western Gulf states Sun night-Mon
with low pressure developing over the Gulf and continuing a slow
east movement on Tue, with a wave of low pressure along the front
traversing Florida.

The next wave crossing the northern Pacific toward the Pacific
northwest is poised to approach or move onshore Monday 18 Nov.
The last couple of runs of the ECMWF showed a closed low
developing within the wave (just off the northern Ca/Southern OR
coast 12z Tue 19 Nov), but most ECMWF and GEFS ensemble members
show an open wave persisting.
The operational progs blended the operational run with the
operational GFS and respective 00z ECMWF and 06z GEFS ensemble
means and show an open wave until more solutions show the closed
low developing.


...Weather Highlights/Threats...

Below average temperatures in the East will slowly moderate back
toward more typical mid-November values by early next week. Much
of the West will have temperatures above normal by 5-15 degrees
through this weekend, moderating early next week with the arrival
of the next upper trough.

The system in the southeast to mid Atlantic coastal waters should
keep the heaviest rains offshore but is close enough to produce
showers in coastal areas. The strong pressure gradient between the
low and mid 1030s high over New England leads to windy conditions
along the southeast to the mid Atlantic coasts. The precipitation
shield will move northward into New England early next week.

Several systems out of the Pacific will maintain a rather wet
period for at least coastal Washington/Oregon and the Cascades,
with less rain/snow along and just west of the Continental Divide.


Petersen/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

- Heavy precipitation across portions of the Cascades, Sun-Tue,
Nov 17-Nov 19.
- Heavy rain across portions of the Pacific Northwest, Sat-Sun,
Nov 16-Nov 17.
- Heavy rain across portions of the Mid-Atlantic, Fri-Sat, Nov
15-Nov 16.
- Flooding occurring or imminent across portions of the Northern
Plains.
- High winds across portions of the Southeast, the Mid-Atlantic,
and the Northeast, Sat-Mon, Nov 16-Nov 18.
- Much below normal temperatures across portions of the
Mississippi Valley, the Central/Southern Appalachians, the
Tennessee Valley, the Great Lakes, the Mid-Atlantic, the
Southeast, the Southern Plains, and the Ohio Valley, Fri, Nov 15.
- Much below normal temperatures across portions of the Northeast,
the Central Appalachians, the Middle Mississippi Valley, the
Mid-Atlantic, the Southeast, the Great Lakes, and the Ohio Valley,
Sat, Nov 16.

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

Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
727 AM EST Tue Nov 12 2019

Valid 00Z Wed Nov 13 2019 - 00Z Wed Nov 20 2019

...Weekend Heavy Rain Threat...

Models and ensembles agree in showing a relatively benign weather
pattern for Hawaii into Friday in a pattern with weak flow and
limited moisture and showers. The pattern amplfies and becomes
more active over the weekend into early next week as guidance
shows an increasing signal for significant upper trough
amplification to the northwest of the state. Lowering heights and
increasing instability will accompany the approach of a cold front
into the islands along with a lead increase in deep layered
tropical moisture influx into the state. Solutions also agree on
the potential for moisture from an easterly wave to potentially
also be drawn northward into the frontal zone, with precipitable
water values rising upwards to 2 inches. This setup should support
the potential for an increasingly widespread threat of heavy
rainfall that could be prolonged by possible upper closed low
development and the resumption of trades in a tightening pressure
gradient over the state as surface high pressure builds/bridges to
the north of the state. A composite guidance solution is favored
given favorable solution evolution/clustering.

Schichtel/Tate

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
838 PM EST Tue Nov 12 2019

Day 1
Valid 01Z Wed Nov 13 2019 - 12Z Wed Nov 13 2019

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Burke

Day 1 threat area: www.wpc.ncep.noaa.gov/qpf/94epoints.txt

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
344 PM EST Tue Nov 12 2019

Day 2
Valid 12Z Wed Nov 13 2019 - 12Z Thu Nov 14 2019

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Bann


Day 2 threat area: www.wpc.ncep.noaa.gov/qpf/98epoints.txt

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
345 PM EST Tue Nov 12 2019

Day 3
Valid 12Z Thu Nov 14 2019 - 12Z Fri Nov 15 2019

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Bann


Day 3 threat area: www.wpc.ncep.noaa.gov/qpf/99epoints.txt

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
400 PM EST Tue Nov 12 2019

Valid 00Z Wed Nov 13 2019 - 00Z Sat Nov 16 2019


Days 1-3...

...Great Lakes...
Models show low level winds backing to the south ahead of a weak
shortwave trough moving across the northern Plains and upper
Midwest on Wednesday. This is expected to a support a long-fetch
Lake Michigan lake effect snow band, raising the potential for
some locally heavy amounts over the eastern U.P. of Michigan on
Wednesday.

As winds veer to the west late Wednesday, lake effect snow bands
may produce some locally heavy snows east of Lake Michigan into
Lower Michigan.

For Days 1-3, the probability of significant icing (0.25-inch) is
less than 10 percent.

Pereira

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
436 PM EST Tue Nov 12 2019

Valid 12Z Fri Nov 15 2019 - 12Z Tue Nov 19 2019

...Pattern Overview and Guidance/Predictability Assessment...

Upper ridging on either side of North America will favor a series
of troughs progressing across the CONUS.
For days 3-4, an upper trough crossing the southeast causes
low pressure to develop just off the Southeast coast and move
northeastward to off the Mid Atlantic coast by day 5 and off the
New England coast days 6-7. Models cluster in 2 camps, with the
GFS/GEFS Members/Canadian slightly faster in moving the low
northeast and the ECMWF/ECMWF mean/00z UKMET slower. A blended
solution is proposed to mitigate the timing differences.

A Western trough on Friday will progress across the northwest and
northern Rockies and then the northern Plains Sat and into the
upper Great Lakes/mid MS Valley Sun 17 Nov. The southern portion
of the trough amplifies over western Gulf states Sun night-Mon
with low pressure developing over the Gulf and continuing a slow
east movement on Tue, with a wave of low pressure along the front
traversing Florida.

The next wave crossing the northern Pacific toward the Pacific
northwest is poised to approach or move onshore Monday 18 Nov.
The last couple of runs of the ECMWF showed a closed low
developing within the wave (just off the northern Ca/Southern OR
coast 12z Tue 19 Nov), but most ECMWF and GEFS ensemble members
show an open wave persisting.
The operational progs blended the operational run with the
operational GFS and respective 00z ECMWF and 06z GEFS ensemble
means and show an open wave until more solutions show the closed
low developing.


...Weather Highlights/Threats...

Below average temperatures in the East will slowly moderate back
toward more typical mid-November values by early next week. Much
of the West will have temperatures above normal by 5-15 degrees
through this weekend, moderating early next week with the arrival
of the next upper trough.

The system in the southeast to mid Atlantic coastal waters should
keep the heaviest rains offshore but is close enough to produce
showers in coastal areas. The strong pressure gradient between the
low and mid 1030s high over New England leads to windy conditions
along the southeast to the mid Atlantic coasts. The precipitation
shield will move northward into New England early next week.

Several systems out of the Pacific will maintain a rather wet
period for at least coastal Washington/Oregon and the Cascades,
with less rain/snow along and just west of the Continental Divide.


Petersen/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

- Heavy precipitation across portions of the Cascades, Sun-Tue,
Nov 17-Nov 19.
- Heavy rain across portions of the Pacific Northwest, Sat-Sun,
Nov 16-Nov 17.
- Heavy rain across portions of the Mid-Atlantic, Fri-Sat, Nov
15-Nov 16.
- Flooding occurring or imminent across portions of the Northern
Plains.
- High winds across portions of the Southeast, the Mid-Atlantic,
and the Northeast, Sat-Mon, Nov 16-Nov 18.
- Much below normal temperatures across portions of the
Mississippi Valley, the Central/Southern Appalachians, the
Tennessee Valley, the Great Lakes, the Mid-Atlantic, the
Southeast, the Southern Plains, and the Ohio Valley, Fri, Nov 15.
- Much below normal temperatures across portions of the Northeast,
the Central Appalachians, the Middle Mississippi Valley, the
Mid-Atlantic, the Southeast, the Great Lakes, and the Ohio Valley,
Sat, Nov 16.

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