Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/20/20
Area Forecast Discussion
National Weather Service La Crosse WI
445 PM CST Thu Nov 19 2020
.SHORT TERM...(This evening through Friday)
Issued at 227 PM CST Thu Nov 19 2020
A weak cold front was positioned along the Interstate 35 corridor
at 20Z with a slight decrease in temperature behind it. Further
northwest, a secondary cold front was seen across northern MN
extending to near the ND/SD border. Satellite indicated a sharp
low-cloud boundary just behind that front and stronger cold
advection push /per 925mb RAP analysis/. Overnight the colder air
will filter in as both fronts pass through. By morning, the model
consensus on the Dakotas low-cloud deck is around about I-94 to
I-90. Overall, Friday will be cooler as 925mb temperatures drop
about 10C from today...with northwest winds gusting to 20 mph.
.LONG TERM...(Friday night through Thursday)
Issued at 227 PM CST Thu Nov 19 2020
The cold front will bring a colder air mass into the region as a
longwave trough develops over the upper Midwest. Overall minor
weather expected now for the weekend, with precipitation chances
holding off until Sunday. There is fairly good agreement on a
moderate-strong 300-500mb Q-vector Convergence signal moving through
Sunday in the latest 19.12Z GEM/NAM/GFS/ECMWF. Mid-level lapse
rates are >7C/km - not too shabby. The low-level QG forcing is
rather meh however, and mainly focused north of the area.
Isentropic lift is very weak or nil in the low-levels as well.
Thus, it looks cloudy, and the deterministic models show a light
QPF signal. The 19.06Z GEFS means of 0.01-0.05" across the area
Sunday also confirm this signal. Around 50% of the 19.00Z ECMWF
ensemble family members show some light precipitation falling.
Thus, for now, have continued small precipitation chances for
rain/snow most areas and snow north of I-94. This may be a low
QPF, high precipitation chance event as it draws closer. No travel
impacts across WI are seen for the deer hunting weekend.
Monday through Thanksgiving...
A progressive pattern continues into this period and the wave
amplitude does increase across the CONUS. A stronger system still
looks like it will affect the area Monday night into Tuesday
night with precipitation. The 19.00Z ECMWF EPS ensemble suggests
an increase in both the mean amount and precipitating members
for this system, over the 18.12Z run. The mean is around 0.30" in
southern WI and northeast IA with amounts decreasing further
north. The 19.06Z EPS agrees well with the 00Z run. Temperature
profiles could result in accumulating snow before a change over to
rain. The GEFS 19.06Z is more aggressive, further north, and more
convective with the precipitation amounts with 0.75-1" means
across much of the area. Again, similar signals of mainly a rain
system, with some snow possible at onset. The GFS/GEFS seem too
aggressive with the initial wave and precipitation totals compared
to the family of solutions. This system will bear watching,
especially it is comes in Monday night with colder air still in
place - or the track shifts a bit south - as accumulating snow
would be possible.
Thanksgiving looks like a quiet day regionwide at this time.
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 445 PM CST Thu Nov 19 2020
Relatively low forecast confidence for this forecast cycle with
ceilings the primary challenge.
This evening expect VFR conditions with SCT-BKN mid/high clouds
and light winds becoming northwesterly behind a cold front. An
area of IFR/MVFR stratus across northern MN at this time is
expected to progress south and east behind a secondary surge of
cooler air tonight. There is potential for these clouds to reach
as far south as KRST/KLSE towards sunrise Friday with IFR/MVFR
conditions for at least a period during the morning. Given the
uncertainty in southward extent, opted not to include any MVFR
ceilings at this point, but this will be monitored for subsequent
updates. NW winds will gust to around 20 kts at times Friday
Area Forecast Discussion...Updated
National Weather Service Billings MT
836 PM MST Thu Nov 19 2020
Updated the forecast to bring wind speeds closer to observed
trends. Winds were still gusty over parts of the area at 03Z as
very steep lapse rates and virga allowed winds to mix down. As
airmass stabilizes overnight, expect gusts to wane in frequency. A
weak back door front was moving into the eastern zones given
pressure rises over NE MT and a wind shift to the N. Despite
echoes on radar, have seen no evidence of precipitation reaching
the ground, except for some recent light snow in KBZN. Left the
low PoPs alone to cover any precipitation that does reach the
ground especially as temp/dewpoint spreads lessen with time. Dry
forecast later tonight looked fine as airmass stabilizes. Some
stratus was observed over NE MT and some HRRR runs hinted at light
fog over E MT tonight. Since this has not occurred in the NE, will
not add fog to the forecast. Arthur
Tonight through Friday night...
Winds will increase from Harlowton to Big Timber to Livingston
with gusts up to 45 mph. Winds will also increase on the plains
with gusts to 35 mph, decreasing after sunset. Shower activity
will remain over counties along the ND border through early
evening before diminishing. Any rain that does fall will remain
light. Snow showers will occur over the mountains but amounts
will remain light with the highest peaks seeing 1-2 additional
Friday will remain drier with wind from Harlowton to Big Timber
to Livingston. Winds will gust to 40 mph but those winds are
expected early and will diminish during the afternoon.
Low temperatures tonight will drop into the 20s, warming into the
40s for Friday. Friday night will be slightly cooler with
temperatures west of Big Timber dropping into the teens and areas
east dropping into the 20s.
Saturday through Thursday...
Mainly dry conditions will persist through the extended forecast
period, with the exception of mountain snow. Expect to see mainly
seasonal temperatures throughout the extended period.
Upper level ridging will build into the region following a fairly
quick moving, weak cold front crossing the region Saturday.
Expect no precip with this system, but a brief period of gusty NW
winds, with gusts around 25 mph, are expected. The ridging will
prevail through Sunday, and shift east Monday morning. Monday and
Tuesday will see increasing SW Pacific flow, bringing rain/snow
chances for the western mountains. There is some potential for
isolated showers into lower elevations southwest of Billings
Monday night, as the trough crosses the region. That said, best
potential for appreciable precip will be over higher terrain, as
most of the energy is progged to shift south of the CWA. Shortwave
ridging progged to build in for Tuesday evening/night, before yet
another shortwave moves through the region on Wednesday. This
shortwave will bringing more mountain snow, but little chance into
the lower elevations through Thursday.
The bigger concern through the extended period is wind potential,
as the Pacific flow strengthens early next week. The pattern
suggests a few days of gusty winds in the foothills for the
middle of next week, but uncertainty remains. We will continue to
to watch model trends in the coming days for a better read on
An unstable upper level disturbance continues to bring isolated
showers this evening to eastern routes and high terrain, with
local MVFR. Mountains will be frequently obscured in snow showers.
West winds continue to gust 30-40 knots along the western
foothills, and 20-30 knots further east. Shower activity is
expected to end by late evening, and VFR will prevail tonight.
.PRELIMINARY POINT TEMP/POPS...
Fri Sat Sun Mon Tue Wed Thu
BIL 028/046 026/046 024/045 027/046 027/046 031/046 026/042
10/U 00/U 00/U 00/E 10/N 11/B 11/B
LVM 024/041 019/041 018/044 023/042 022/043 026/040 021/038
20/N 00/U 00/U 01/N 10/N 23/W 21/N
HDN 026/048 021/047 021/049 021/047 023/048 026/048 024/044
10/U 00/U 00/U 00/E 10/U 11/B 21/B
MLS 026/045 023/045 022/045 021/043 023/045 026/047 024/041
20/U 00/B 00/U 00/E 00/U 00/B 00/B
4BQ 028/045 023/046 023/046 022/046 024/046 026/048 025/042
20/U 00/U 00/U 00/B 00/U 00/B 11/B
BHK 023/042 023/044 020/043 020/042 021/042 026/046 022/039
10/U 00/U 00/U 00/B 00/U 00/N 00/B
SHR 021/043 016/045 017/046 019/047 019/046 023/048 021/040
10/U 00/U 00/U 00/B 10/U 11/B 21/B
Area Forecast Discussion
National Weather Service Glasgow MT
150 PM MST Thu Nov 19 2020
A backdoor cold front and snowpack made it hard for many locations
along and north of Highway 2 today to mix out. Low clouds also
helped to keep these locations close to the freezing mark while
areas to the south reached the 40s to near 50.
Canadian surface high will nose into the area tonight providing a
cooler night especially where skies are clear with light winds and
some snowcover. RAP and CMC suggesting temperatures fall to near
zero in north-central Phillips and Valley counties by Friday
The surface high will drift into the northern Plains Friday with a
weak front bringing in clouds early Saturday.
Mainly dry and seasonably cool conditions will continue into the
Thanksgiving holiday. Cold front early Wednesday looks to bring
just wind and cooler airmass from the Prairie provinces into
IFR clouds/visibility will linger across the area tonight as a
shallow cold airmass settles in.
WINDS: Look for light NW winds tonight to become Light and
Variable Friday morning. TFJ
Area Forecast Discussion
National Weather Service Hanford CA
430 PM PST Thu Nov 19 2020
...UPDATED AIR QUALITY SECTION...
Cool, near seasonal highs are expected to occur for the
next seven days. A disturbance will pass through the area on
Monday, which could provide the Sierra Nevada with a slight chance
of precipitation. Otherwise, expect the rest of Central
California to remain dry for the next seven days.
Some patchy fog formed earlier this morning in the valley portion
of Kern County, and mixed out by late morning. In the northern
portion of the San Joaquin Valley, a stream of high clouds is
currently passing through and will continue to do so for the rest
of the day, eventually getting the central and south valley
tonight. In terms of fog tonight, the latest HRRR isn`t showing
much fog -- perhaps the incoming upper cloud cover will help avoid
a fog event. Anyways, expect near normal temperatures today,
meaning highs in the mid 60s. Afternoon highs are expected to drop
in the low 60s as a couple of embedded disturbances pass through
the region this weekend. Highs in the low 60s are a couple
degrees below average. Morning lows by Saturday will be on the
cool side, likely in the low to mid 30s.
By late Sunday/early Monday, an upper level low will approach the
forecast area. This low is likely to be moisture-starved, but
could trigger a shower or two over the Sierra Nevada by Monday
afternoon. Weak upper ridging is forecast by Tuesday and
Wednesday, but it won`t be enough to move the temperature forecast
much. Expect low 60s for afternoon highs to continue next week,
including Thanksgiving Day. Dry weather is likely to continue for
most of the forecast area in the foreseeable future.
MVFR visibility due to mist is possible in San Joaquin Valley
from 08z Friday to 16z Friday. Otherwise, VFR conditions will
prevail for the next 24 ours across the Central California
.AIR QUALITY ISSUES...
On Friday November 20 2020...Fireplace/Wood Stove Burning Status
is: No Burning Unless Registered in Fresno and Kern Counties.
Further information is available at Valleyair.org
The level of certainty for days 1 and 2 is high.
The level of certainty for days 3 through 7 is medium.
Certainty levels include low...medium...and high. Please visit
www.weather.gov/hnx/certainty.html for additional information
an/or to provide feedback.
AREA FORECAST DISCUSSION
National Weather Service Wilmington OH
940 PM EST Thu Nov 19 2020
A weak cold front will cross through the region from northwest
to southeast Friday night, with some light rain showers and
sprinkles expected ahead of it beginning as early as late
Friday. The front will have crossed south of the Ohio River by
early Saturday. High pressure in the Upper Midwest will track
east through the Great Lakes Saturday, changing winds over the
region from north to northeast.
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Between high pressure over eastern North Carolina and low
pressure over James Bay, the Great Lakes and northern Ohio
Valley remain impacted by a tight pressure gradient, with a
weaker gradient in the middle Ohio Valley and closer to the
Appalachians. As with last night, this is creating a scenario
where winds in the northwest ILN CWA (near and north/west of
Dayton) are remaining somewhat stiff -- with 30-35 MPH gusts
still occurring at times. Winds in the southeast ILN CWA, on the
other hand, are very weak. The going wind forecast is in fairly
good shape to capture this, but this scenario will have an
impact on temperatures tonight as well. The temperature gradient
was sharpened in this forecast update, reflecting a slight
increase in the NW, and a slight decrease in the SE.
One other interesting feature tonight is the robust swath of
altocumulus clouds that developed over Indiana and NW Ohio, and
is now drifting east across the northern sections of the ILN
forecast area. Wilmington is too far south to perfectly sample
the environment in which these clouds have formed, but the 00Z
KILN sounding captured some very steep lapse rates (albeit with
fairly dry air) in the 700mb-500mb layer. HRRR model soundings
for Lima OH (KAOH) suggest similar steep lapse rates, but also
with more sufficient moisture for clouds. 700mb model plots
(NAM/GFS) suggest theta-e advection as well. While these clouds
are also showing up as cellular-looking echoes on KILN/KIWX/KCLE
radar, the extremely dry air in the lowest 10kft means it will
be very unlikely for anything to reach the ground.
Previous discussion >
Gusty winds will become more of a strong sustained 10-20 mph
overnight as the low level jet moves away from the region to the
northeast, but the axis of the weakening jet pushes into the
CWA. Temperatures will stay up overnight with this wind, only
dropping to near 50 in the northwest and mid 40s in the east and
High cloud cover will thicken and lower as moisture gets
squeezed ahead of the approaching front tonight.
.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
In continued southwest flow ahead of the front, moisture and
subsequent cloud cover will increase through the day. Any
chances of rain outside of a passing late day sprinkle should
hold off through the daytime period as the mid levels remain
fairly dry. Highs will range from 60-65.
The threat for shower activity will increase in the evening and
overnight, with models showing a more southerly track to the
rain footprint than earlier forecast. Have shifted best chances
to the south and feel that scattered light rain showers and
passing sprinkles should have pops limited to just a chance.
This may need to be bumped up later but the only driving force
is the increased moisture in deep southwest flow being undercut
by the surface cold front. Very little shortwave energy is
noted. The surface front and exiting low level jet seem to be
the driving force for this part of the forecast.
Better chances for rain reside along the Ohio River, with little
if any precip expected along and near the I-70 corridor in the
northern half of CWA. None of the models are suggesting any more
than a tenth of an inch at best, continuing into the extended
.LONG TERM /SATURDAY THROUGH THURSDAY/...
H5 flow will be quasi-zonal to begin the period, with a
Canadian cyclone swinging a cold front through the fa Saturday
morning. Nearly overcast conditions are to be expected
throughout the day as the front is will stall out just south of
the Ohio River. The frontal boundary could produce some
scattered light rain, but lack of deep layer moisture and weak
isentropic lift will inhibit any long-lived or widespread
development of rain. Kept only 20-30% PoPs in the grids for
Saturday, but any pcpn appears to be more likely during the
morning hours and further south near the stalled front.
Beginning Saturday night, a warm front will begin to lift into
the Ohio Valley region with a low pressure system tracking
northward through the Midwest. A surge of higher RH values with
the southerly flow, combined with the east-west oriented frontal
boundary will lead to more widespread rain showers late
Saturday night through Sunday across a broader area. Thus, have
continued the trend of likely PoPs in the grids throughout the
day on Sunday. GEFS and ECMWF plumes generally keep QPF values
below 0.75" for this event, which seems reasonable with PWATs
only in the 0.5"-1.0" range.
The low pressure will quickly eject to the northeast Sunday
night, leaving a decreasing trend in PoPs from west to east as
we progress through the overnight hours. Removed any lingering
precip chances in the blend after 12z Monday as the system will
be fairly progressive. Could see a few snow flurries on the tail
end of the system exiting late Sunday night, but no measurable
snow expected. Surface high pressure under an H5 ridge will
begin to propogate across the Midwest region. This should keep
temperatures near seasonal on Monday.
A relatively progressive pattern appears to be in store for
next week with the meandering jet stream flow. By Tuesday, a s/w
trough will begin to move into the region and provide
increasing clouds, cooler temperatures and a trend towards high
PoPs as we head into Tuesday night and Wednesday. This trough
and associated surface low pressure will shift towards the
northeast by Thursday, allowing for another high pressure system
to develop and dry us out again. Temperatures appear to be on
track for near or just below seasonal values for both Wednesday
.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
SSW winds will continue to diminish this evening, with gusts
becoming less common after 02Z, though a few gusts to near 20kts
may still occur at KDAY overnight. LLWS will also remain in
place for all TAF sites.
Tomorrow, winds will increase slightly, with gusts to around 20
knots possible at all TAF sites from around 14Z-21Z. Clouds will
also begin to thicken, with MVFR ceilings moving in after 20Z.
Precipitation appears likely to hold off until after 00Z, but
some rain may impact the Cincinnati TAF sites just after that
OUTLOOK...Occasional MVFR ceilings are possible through Sunday
Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
722 PM EST Thu Nov 19 2020
Latest RAP model has mid/upper ridging across the south-central
and southeastern states and the Gulf of Mexico through most of
Fri. Weak troughiness in the Atlantic will drift in toward the
Bahamas during Fri. At the surface an axis of high pressure
resides from the Atlantic to the Deep South and spills down across
the Gulf and FL...with a gradient of about 7 millibars from the
GA line to the Florida Keys this evening. The high pressure begins
to ease Fri and allows the gradient to relax some.
The air mass continues stable and generally dry...although
forecast PWAT vales of less than 1 inch this evening will increase
slightly Fri...to 1 inch and just above. This will be enough to
support a few more clouds compared to today. In addition this
moisture along with the mid/upper troughiness near the Bahamas
could support scattered showers...but mainly confined to the FL
east coast. Temperatures will run above normal by 2 to 3 degrees.
Forecasts look good with no updates planned.
20/00Z TAF cycle. VFR. FEW to BKN SC. NE winds 08-11KT overnight
then ENE 10-13KT with gusts to 20KT AFT 16Z
AS noted in the discussion above the gradient remains tight over
night with small craft advisory conditions for most of the marine
zones. Winds begin to slacken early Fri but are expected to be
near or at exercise caution levels throughout the weekend.
.Preliminary Point Temps/PoPs...
TPA 64 82 66 82 / 0 0 0 0
FMY 64 82 65 82 / 0 0 0 10
GIF 63 81 65 81 / 0 0 0 10
SRQ 64 82 67 82 / 0 0 0 0
BKV 59 80 62 81 / 0 0 0 0
SPG 67 79 68 80 / 0 0 0 0
Gulf waters...Small Craft Advisory until 4 AM EST Friday for Coastal waters
from Bonita Beach to Englewood FL out 20 NM-Coastal waters
from Englewood to Tarpon Springs FL out 20 NM-Waters from
Bonita Beach to Englewood FL out 20 to 60 NM-Waters from
Englewood to Tarpon Springs FL out 20 to 60 NM-Waters from
Tarpon Springs to Suwannee River FL out 20 to 60 NM.