Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/14/20
Area Forecast Discussion
National Weather Service Charleston SC
1054 PM EST Thu Feb 13 2020
Cooler high pressure will prevail through through Saturday
night. A series of upper disturbances will move through from
Sunday into the middle of next week.
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Intermittent ana-frontal light rains will continue overnight,
aided by large scale forcing from the nearby 120-40 kt upper
jet moving into the Southeast. Additional rain amounts will be
limited however, given that much of the rain is falling from a
mid level cloud deck. We have 30-50% PoP south and east, with
20-30% chances north and west.
Both the HREF and the HRRR show a short wave arriving from the
southwest closer to daybreak, and this supports higher PoP than
we now have over areas near the coast and south of I-16 in
Georgia. We will monitor for this possibility.
A post-frontal trough will slide southward overnight as winds
veer to the northwest and north, and this will allow for cold
advection to overspread the region. This will be tempered
somewhat by considerable cloud cover, but we still anticipate
low temps that are at least 25-35F colder than it was during the
.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
The cold front should be well offshore by daybreak Friday.
However, continued upper shortwave energy across coastal areas
and lingering low-level moisture could allow for scattered
showers to persist along the coast through mid-morning. Skies
should then clear by early afternoon across most or all of the
area. A considerably colder airmass will settle over the area
with high temps in the upper 50s to lower 60s.
Cold high pressure will remain over the area through Saturday,
then it will shift off the coast Saturday night into Sunday.
Moisture will increase substantially on Sunday as a result of
return flow. Upper shortwave energy will result in coastal
trough development late Saturday night, with increasing clouds
and scattered showers on Sunday.
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Generally low confidence through the period. A longwave trough
should push offshore Sunday night followed by high pressure
Monday. Increasing moisture and additional shortwave energy
could bring scattered showers starting Monday night and
continuing through much of the rest of the period as a cold
front eventually moves through. Cannot rule out a few
thunderstorms if instability can develop. Temperatures will
likely be above normal until possibly Thursday if the cold
front moves through beforehand.
.AVIATION /04Z FRIDAY THROUGH TUESDAY/...
Very intermittent light rains will continue behind the a cold
front overnight, and maybe even into the early morning on
Friday. While a brief period of MVFR ceilings could occur, VFR
conditions look to prevail. The bulk of Friday will be rainfree,
and as drier air works it`s way in, skies will become clear at
both terminals during the afternoon.
Extended Aviation Outlook: Restrictions possible Saturday night
through Sunday as a coastal trough affects the area. Brief
restrictions then possible Monday night and Tuesday as an upper
disturbance moves through.
Tonight: Small Craft Advisories are in place for the Charleston
County Atlantic waters and the Georgia waters beyond 20 nm.
Winds begin the night westerly at no more than 10 or 15 kt,
then veer around to the NW behind the cold front by 1 am. Cold
air advection behind a post-frontal trough will allow for winds
to clock around to the N or N-NE with increasing speeds late.
Conditions will be close to advisory levels on the other marine
waters, but the current thinking is that it`ll fall just shy.
Small Craft Advisory conditions expected to continue through
midday Friday over the Charleston nearshore waters and through
Saturday evening in the offshore GA waters.
Record high minimums for Feb 13:
MARINE...Small Craft Advisory until 6 AM EST Sunday for AMZ374.
Small Craft Advisory until noon EST Friday for AMZ350.
Area Forecast Discussion
National Weather Service Cleveland OH
1002 PM EST Thu Feb 13 2020
An Arctic cold front will move southeast across the area this
evening. Arctic high pressure from the northern Great Plains
region builds in on Friday and Friday night before moving off to
the east on Saturday. A cold front associated with a low over
southern Ontario/Quebec moves across the area on Sunday.
.NEAR TERM /THROUGH FRIDAY NIGHT/...
Temperatures are definitely getting cold enough for lake effect
snow to develop. The DTX 00Z sounding came in with H8
temperatures of -16C. We just need winds to align better to get
more organized lake effect snow bands. For much of tonight these
bands will remain disorganized and therefore limit their
potential. Toward morning we may see some better organization,
but questions remain on band placement and then the degree of
dry air being entrained. Upstream dewpoints are below 0. It will
definitely be a fluffy snow. So no confidence yet to make any
changes with the Advisory. Geauga may be questionable. Erie has
at least had decent snow this evening. HRRR and RAP show a Huron
connected band affecting more of Ashtabula into Crawford during
the second half of tonight. There are multiple bands off of
Huron now, but it will not be until after midnight sometime
before there is less shear. Therefore, no significant change
was made to the forecast. Previous discussion follows.
An Arctic cold front is approaching the lakeshore from the north
and is clearly visible on the CLE radar this afternoon. We have
noticed in the last hour or so an uptick with organization of a
burst of heavier snow associated along the front which will be
arriving into the Cleveland metro area around the evening rush
hour. Temperatures will fall through the 20s with the passage
of the front and any moisture on roadways may flash freeze this
evening. High res near term models are in good agreement with
this narrow band of snow moving across most of the area through
early evening. We will have to monitor any potential for a snow
squall along the front with visibilities dropping to 1/2 of a
mile and gusty winds.
Once the Arctic front blows through the area this evening, the
Arctic airmass moving over the unfrozen waters of Lake Erie will
ignite lake effect snow showers and potentially a few lake
effect snow squalls. The orientation of te wind from the north
or northwest will also bring down a Lake Huron fetch which the
high-res models indicate that particular lake effect band will
move to Erie County PA or Ashtabula County area tonight. The
high res models all show a few lake effect bands tonight
through Friday morning but there is medium confidence on exactly
where the bands will be favored and they also will be moving
around as the low level shifts. A few models pick up on a snow
band for the areas west of the CLE metro area and a few show
that band east of the metro. But in general we are expecting 1
to 3 inches possible across much of the primary and maybe
secondary Snowbelt through the morning. We tried to highlight
the areas that have the greatest potential of 3 to 5 inches of
lake effect snow in the Winter Weather Advisory for Geauga and
Erie County PA. This advisory may need to be adjusted or
expanded if the Lake Effect Snow becomes better organized or
The Arctic high pressure settles in later on Friday into Friday
night. This will allow the surface flow to become weaker and
shift to a westerly or even southwesterly flow by Friday
evening. We expect much of the lake effect snow showers to come
to an end by late Friday morning or midday. Despite clearing
skies on Friday, temperatures will struggle to get out of the
teens during the day. Wind chills will be below zero for both
Friday morning and Friday night. Actual air temperatures both
tonight and Friday night will likely be in the single digits
aware from the lakeshore and urban areas.
.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
Fair weather is still expected on Saturday as high pressure at the
surface and aloft exits to the east and a trough at the surface and
aloft approaches from the Upper Midwest and Upper Great Lakes. A
southerly flow veering to west-southwesterly with height will result
in warm air advection and contribute to afternoon highs reaching the
lower to mid 30`s. Saturday night through Sunday evening, the trough
at the surface and aloft will gradually traverse our CWA from west
to east, with a weak accompanying cold front sweeping through Sunday
evening. Simultaneously, light and isolated snow and/or rain showers
are possible. High pressure at the surface and aloft should then
build from the west during the predawn hours of Monday morning,
allowing fair weather to return. Saturday night low temperatures
should reach the mid 20`s to lower 30`s, while Sunday afternoon
highs are forecast to reach the upper 30`s to lower 40`s. Sunday
night should be a touch cooler, with lows in the 20`s for the whole
.LONG TERM /MONDAY THROUGH THURSDAY/...
High pressure at the surface and aloft begins exiting our CWA to the
east as a surface low develops from the Central Plains toward the
Upper Midwest on Monday. Isentropic lift tapping into Gulf of Mexico
moisture should allow snow and/or rain showers to affect most of our
CWA. Afternoon high temperatures should reach the upper 30`s to mid
40`s. Isentropic lift and associated rain and/or snow showers
continue Monday night as the surface low perhaps tracks from the
Upper Midwest toward the Upper Great Lakes and the accompanying warm
front sweeps north across our CWA. Aloft, the parent trough should
begin settling over the Northern Great Plains and begin approaching
our CWA. Monday night`s lows should mainly reach the mid to upper
The longwave trough continues overspreading our region from the
Northern Great Plains and Upper Midwest on Tuesday, while the
attendant surface low may track from the Upper Great Lakes to
southern Quebec, allowing the trailing cold front to sweep east over
our CWA. Additional periods of primarily rain are expected, with
high temperatures forecast to reach the mid 40`s to lower 50`s prior
to the cold frontal passage.
Tuesday night through Wednesday night, an expansive surface high
pressure ridge builds from the west. Aloft, the longwave trough
should continue moving eastward over our CWA through Wednesday and
should then be followed by a longwave high pressure ridge building
from the west Wednesday night. This pattern will cause precipitation
chances to decrease over much of our CWA. However, lake effect snows
could target the snowbelt Tuesday night through Wednesday night as
colder air settles over Lake Erie and our region. Tuesday night lows
should reach the 20`s, while Wednesday afternoon highs should mainly
reach the lower to mid 30`s. Wednesday night should be colder, with
lows in the teens to lower 20`s. Fair weather should return to the
whole CWA on Thursday as high pressure at the surface and aloft
continues building over the region. Thursday afternoon`s highs
should reach the mid 20`s to lower 30`s.
.AVIATION /00Z Friday THROUGH Tuesday/...
Areas of snow will still be in the vicinity of the terminals
this evening and early overnight as there is an upper trough yet
to pass. The most intense snow right along the cold front will
affect YNG/CAK at the start of the TAF period/00Z for a very
brief time. After that snow will be between 1 1/2 miles and 5
miles. Toward morning, areal coverage will decrease and snow
showers will be more lake effect oriented and therefore more hit
or miss for CLE/CAK/YNG/ERI through Friday morning. Keep
ceilings MVFR through the TAF, but could be some holes/breaks in
the overcast as is seen upstream across MI. Low confidence in
timing and how long those breaks would hold. Best chance would
be for TOl as the others should fill in with lake stratus. Winds
will be 10 to 15 knots from the northwest early this evening and
then weaken overnight and shift more westerly for Friday.
.OUTLOOK...Non-VFR possible at times Saturday night and Sunday with
mixed precipitation. Non-VFR possible again on Tuesday.
Low pressure pulls away from New England and the Canadian Maritimes
through tonight as it tracks east-northeast over Atlantic waters. An
Arctic front trailing this low sweeps south across Lake Erie this
afternoon. Behind the front, northwesterly winds increase to 15 to
20 knots over the entire lake and waves build to 3 to 5 feet in the
central basin. A Small Craft Advisory is in effect from 5 PM today
to 7 AM Friday for nearshore waters from Vermilion to Conneaut. As
colder air overspreads Lake Erie, some freezing spray is expected
amidst higher waves.
Conditions improve quickly on Friday as a large area of high
pressure builds east across the Eastern Great Lakes. The high shifts
to the east on Saturday with southerly to southwesterly winds
increasing to 15 to 25 knots ahead of the next low pressure system
that will pass north of the lakes. Winds may approach Small Craft
Advisory criteria, although the offshore flow will help keep the
larger waves on the outer fringes of the nearshore waters.
Conditions should improve gradually Sunday into Monday as the next
area of high pressure builds gradually eastward across the lake.
Monday night, winds should shift from southeasterly to southerly as
a warm front sweeps north over the lake and the parent low tracks
across the Upper Midwest and Upper Great Lakes. On Tuesday, a cold
front should sweep east across Lake Erie as the low tracks toward
Southern Quebec. Winds shift from southerly to westerly with the
cold frontal passage. Small Craft Advisory conditions may return on
Tuesday, especially east of The Islands.
OH...Winter Weather Advisory until 10 AM EST Friday for OHZ013.
PA...Winter Weather Advisory until 10 AM EST Friday for PAZ002.
MARINE...Small Craft Advisory until 7 AM EST Friday for LEZ145>148.
Area Forecast Discussion
National Weather Service Lubbock TX
459 PM CST Thu Feb 13 2020
Primary concern will be decreasing ceiling heights and visibility
reductions due to fog. In fact, there`s a risk that KLBB/KPVW may
drop to below minimums in freezing fog around sunrise Friday
morning. Indications are that things will be slow to improve
Friday morning though VFR should return by the afternoon.
.PREV DISCUSSION... /issued 223 PM CST Thu Feb 13 2020/
Low clouds have been holding on across the northwestern South
Plains and southern Rolling Plains behind the cold front that has
pushed across the region. Surface flow will remain out of the east
to southeast across the area through tonight into tomorrow
morning and model soundings show this, combined with weak
isentropic lift, will likely help produce patchy freezing fog or
low clouds across the Caprock for Friday morning. Will continue
mention of this possibility through the overnight hours but it may
need to be adjusted to start earlier and end later if some of the
higher-resolution model soundings are correct. Last couple of
NAM, HRRR, and RAP forecast soundings all show the potential for
low clouds and fog to linger across the Caprock through or past
noon Friday which could impact high temperature forecast as well.
Areas that have been under the clouds today have struggled to
climb above freezing, especially where snow remains across the
northwestern South Plains. This is the only area with a bit of
snow left so the impact may not be as great tomorrow across the
rest of the South Plains but it will need to be watched to see if
highs will need to be dropped for Friday.
We will finally see highs start to warm back into the 60s by
Saturday moderated a bit by a weak cold front that the 12Z model
runs now push into the southern third of the forecast area for the
first time. Previous runs have stalled the front across the
northern South Plains/Rolling Plains allowing the southern half of
the forecast area to warm close to 70 degrees so there is still a
bit of uncertainty with high temperatures on Saturday. By Sunday
and Monday, southwesterly flow aloft will develop with a
potentially breezy southwesterly surface wind developing each of
those days as well. That will boost highs to near 70 for Sunday
and Monday on the Caprock and mid to upper 70s for the Rolling
Forecast for Tuesday and beyond continues to focus on the
differences between the ECMWF and GFS. ECMWF brings a strong cold
front through the forecast area by Monday evening while the GFS
holds off until Tuesday morning. Next issue is the GFS increasing
precipitation coverage late Tuesday night into Wednesday morning
with the ECMWF holding off until Wednesday afternoon. Only
consistent elements between these two models is that we will see
cooler temperatures with highs in the 40s/50s for Tuesday and
colder for Wednesday and potentially Thursday. Otherwise, too many
differences to pinpoint when, where, and how much precipitation
will fall not to mention what the precipitation type will be. Will
keep mention of rain/snow mix for times temperatures are below
freezing and mostly rain through the daytime hours except for
Wednesday afternoon which will probably see the coldest highs for
the week with readings in the low to mid 30s on the caprock and
near 40 for the Rolling Plains. Also will keep PoPs just below
model blend for Tuesday into early Wednesday morning because of
the differences in timing between the two models, but then went
with the higher chance PoPs for Wednesday night into Thursday
which is when both GFS/ECMWF have the best agreement in coverage
across the region.