Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/02/20
Area Forecast Discussion
National Weather Service Bismarck ND
1020 PM CDT Wed Apr 1 2020
.UPDATE...
Issued at 1020 PM CDT Wed Apr 1 2020
We`ve upgraded far south central ND to a Winter Storm Warning in
respect to the rapidly-maturing heavy snow band centered across
western SD as of 03 UTC. Guidance remains quite dispersive with
the placement of this band overnight, but extrapolation suggests
it will reach an axis centered on Logan and McIntosh Counties.
Convective elements in south central SD also appear likely to
merge with the frontogenetically-driven mesoscale band and will
likely yield 1" per hour snowfall rates in a narrow axis which
should reach into south central ND after midnight CDT. Recent RAP
cycles and the 00 UTC NAM best-reflect recent trends, so we chose
to weight the overnight forecast closer to them, which resulted in
increased PoPs as far north as Bismarck/Mandan before 12 UTC. We
also sped up the start time of the Winter Weather Advisory from
Bowman and Hettinger to Bismarck/Mandan to 3 am CDT based on the
observed trends. Note however that this is an evolving scenario,
and a tight gradient in snowfall amounts is possible with this
initial band, so confidence in forecast details is still modest
outside of far south central ND. Pending later observational
trends, the Winter Storm Warning may need to be extended further
northeast into Stutsman and surrounding counties, as well.
UPDATE Issued at 712 PM CDT Wed Apr 1 2020
Quick update to let the Winter Weather Advisory in the northwest
and far north central expire as scheduled at 00 UTC in line with
the latest observational trends.
UPDATE Issued at 538 PM CDT Wed Apr 1 2020
We increased PoPs for predominantly snow across central ND through
about 03 UTC with this update to reflect ongoing radar and surface
observation trends. Namely, convectively-enhanced snow showers are
persisting in the post-frontal regime, particularly where midlevel
lapse rates exceed 7 C/km and where RAP-based soundings show non-
zero, though weak MUCAPE aloft. Precipitation is being aided by
midlevel frontogenesis as well. Guidance suggests midlevel lapse
rates will become more stable by mid evening as the post-frontal
air mass cools further, and the initial frontogenesis will also
weaken.
Otherwise, no changes to headlines or the rest of the forecast are
being made at this time, though we fully expect to let the Winter
Weather Advisory in northwest and far north central ND to expire
as scheduled at 00 UTC. We`ll be monitoring mesoscale trends from
SD into far south central ND closely later this evening to assess
how the next round of potential banded precipitation may evolve
overnight.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 220 PM CDT Wed Apr 1 2020
As an upper level shortwave continues to rotate north and east,
snow across the north will continue to taper off through the
evening. Further south, expect some rain and snow showers to
persist through the afternoon and into the evening, potentially
mixed with some light freezing rain and/or sleet. As the snow has
continued to diminish, we elected to go ahead and convert the
Winter Storm Warning across the far northwest to an Advisory. With
light snow still lingering in these areas, will keep the Advisory
going for now.
After a brief lull in activity, another shortwave rotates around
the base of a western trough into south central North Dakota
tonight. Precipitation across the far south central and southern
James River Valley will likely start as rain, transitioning to a
wintry mix of rain, freezing rain, and snow, and then eventually
to all snow. At times on Thursday, snow may mix with freezing
drizzle across the southern James River Valley as forecast
soundings suggest the loss of ice aloft periodically.
Yet another wave rounds the base of the trough into southwestern
and south central North Dakota during the late morning hours on
Thursday, spreading accumulating snow across portions of the
southwest and much of the central. When all is said and done, 4 to
6 inches of snow is likely across the James River Valley with ice
accumulations of up to a tenth of an inch. Further west and north
(including the Bismarck/Mandan area), confidence is increasing in
accumulations reaching the 3 to 5 inch range. Because of this, we
have elected to expand the Winter Weather Advisory area west and
north, although we will not begin the Advisory in these areas
until 12z on Thursday. The only other change was to up the start
time of the Advisory over the James River Valley to 03z Thursday
as guidance has come better in line regarding onset timing. Expect
cold temperatures on Thursday with highs in the 20s.
.LONG TERM...(Thursday night through Wednesday)
Issued at 220 PM CDT Wed Apr 1 2020
Snow will begin to diminish to the east late Thursday night into Friday
morning as the main vort lobe finally pushes out of western and central
North Dakota. A subtle upper ridge moves in Friday afternoon
which will lead to subsidence and widespread clearing. The ridging
will also start to slowly moderate temperatures again after a
chilly morning, mainly in the teens. Friday will see highs in the
30s, and we will see highs this time frame back into the 40s
again through the rest of the weekend. A progressive pattern
continues and various weak waves will bring chances of light rain
and/or snow through Sunday night, but details and exact timing
remain unclear at this time.
A more substantial warm-up comes back into the forecast by the
beginning of the next work week with widespread highs in the 50s
and 60s by Tuesday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 712 PM CDT Wed Apr 1 2020
MVFR ceilings will gradually improve to VFR from west to east this
evening through 06Z with KJMS possibly remaining MVFR (with brief
periods of IFR) overnight, though this is less certain.
Conditions deteriorate for the far south-central and James River
Valley, including KJMS, early Thursday morning with chances for
snow. Periods of heavier snow could drop KJMS cigs/vsby to IFR in
the 12-18Z time frame. Gusty northwest winds continue for all of
western/central North Dakota through the TAF period.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 7 AM CDT /6 AM MDT/ Thursday to 7
AM CDT /6 AM MDT/ Friday for NDZ005-012-013-019>023.
Winter Weather Advisory until 7 AM CDT /6 AM MDT/ Friday for
NDZ025-036-037-045-048-051.
Winter Weather Advisory from 3 AM CDT /2 AM MDT/ Thursday to 7
AM CDT /6 AM MDT/ Friday for NDZ034-035-041>044.
Winter Storm Warning until 7 AM CDT Friday for NDZ046-047-050.
&&
$$
UPDATE...CJS
SHORT TERM...ZH
LONG TERM...ZH
AVIATION...AE
Area Forecast Discussion
National Weather Service Cheyenne WY
926 PM MDT Wed Apr 1 2020
.UPDATE...
Issued at 922 PM MDT Wed Apr 1 2020
Minor updates to this evenings forecast as temperatures really
falling rather quickly across our northern zones. Douglas down to
21 degrees and Chadron 26. Dropped temperatures several degrees
for overnight lows. Do feel rest of forecast is on track. DOuglas
had some pretty heavy snowfall up there with WYDOT webcams showing
snow covered roads there and at Natural Bridge. Updates have been
sent.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 323 PM MDT Wed Apr 1 2020
A few showers popping up across southeastern Wyoming and the
western Nebraska Panhandle this afternoon ahead of a strong cold
front, now draped across northwest Wyoming. Some of these showers
may produce lightning and strong gusty downdraft winds with
soundings showing an inverted-V profile and CAPE of 200 to 500
J/kg mainly along a Cheyenne to Scottsbluff line and to the south.
It`s possible that may also see pea-sized hail in the mix this
afternoon, however, inverted-V profiles are conducive to melting
in the lower levels. And to the north of this line, clouds and
virga have likely led to a moistened layer that may stymie any
thunderstorm activity this afternoon.
The cold front to the northwest will slowly make its way
southeast, supported by a favorable synoptic setup that will
increase frontal forcing and banded precipitation ahead of and
along the front. Hi-Res models seem to have a strong grip on the
forecast, thus the forecast is strongly skewed towards the HRRR
and NAMNest models. Both of these models have strong bands of
precipitation moving into Niobrara, Converse and Carbon Counties
this evening with snow falling heavily along these bands. Heaviest
snow amounts will fall across Niobrara and Converse Counties this
evening and continue through early Thursday morning, with snow
continuing behind the bands over the course of the day. To the
south across Carbon County, bands of heavy snow will form around
midnight and continue to impact the county, and northern Albany
County, through the early afternoon, again continuing to snow
behind the snowbands.
Further south and east of a Carbon-Converse-Niobrara line, the
forecast becomes a little more tricky as there will likely be an
extended period of mixed precipitation tonight and tomorrow
morning. This may lead to a light glaze to the north, and to the
south along the I-80 corridor, ice accumulations of up to a tenth
of an inch. Soundings indicate a low, moist and cold lower layer,
leading to mixed precipitation, freezing drizzle, ice
accumulation, and frozen thick fog, leading to a rime layer over
elevated surfaces tonight and tomorrow morning. As the dendritic
zone moistens, precipitation will transition to snow. This
transition will begin to the northwest of this mixed precip area
along the isentropic boundary as the cold air mass behind it
sinks further southeast. Chadron will transition earlier to snow
around sunrise; Scottsbluff and Cheyenne around noon Thursday, and
Sidney by mid- afternoon. Behind this boundary, expect snow
accumulation to continue, but to lessen over time, finally
tapering off from the northwest after midnight. Have placed
little weight on GFS/EC banding as the frontal passage occurs as
the NAM and all Hi-Res guidance shows banding breaking down once
the band makes it south of that aforementioned Carbon-Converse-
Niobrara line. Several Winter Storm Warnings and Advisories have
been issued to cover the threats expected with this system. Please
see their text for further details.
A few things of note: Snow amounts may be heavier across the I-80
Summit, the I-80 Arlington area, and across northern Platte and
Goshen Counties due to these bands and maybe an earlier transition
to snow as the dendritic zone saturates. Have conveyed these
concerns to the evening shift as they may need to be
upgraded/issued as we move into the event. Not expecting winds
greater that about 20 mph overt the course of the event, which
will lessen the blowing snow threat that usually gets us in
trouble across the roadways. Still, the banded snow will lead to
heavier snow rates, about 2-3 inches per 3 hour period, which will
lead to snow-packed roads and hazardous travel conditions.
Precipitation will have tapered off over the course of Thursday
night and Friday morning. But the cold air mass behind this system
will have filtered in for cold Friday morning temperatures
ranging from 5 to 15 degrees across the High Plains and adjacent
Mountain Terrain. Clear to partly cloudy skies Friday will allow
afternoon temperatures to warm into the 30s.
.LONG TERM...(Thursday night through Wednesday)
Issued at 323 PM MDT Wed Apr 1 2020
Overall a fairly quiet weather pattern expected with no major
system affecting the CWA. It will be warming up over the weekend
as the upper flow gradually turns southwesterly with just a few
showers possible over the higher mtns. The mild pattern should
persist into early next week as a weak upper ridge builds over the
area ahead of an upper low that will sink slowly southward off
the Cal coast. Weak impulses will rotate around this low and
across the area and bring some rain and snow showers to mainly
western parts of the CWA at times, with the best coverage looking
to be on Tuesday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 521 PM MDT Wed Apr 1 2020
Wyoming TAFS...VFR at Rawlins until 03Z, then IFR until 16Z, then
MVFR. Wind gusts to 25 knots from 03Z to 16Z.
VFR at Laramie until 06Z, then IFR until 18Z, then MVFR. Wind
gusts to 25 knots from 06Z to 13Z.
VFR at Cheyenne until 04Z, then IFR until 18Z, then MVFR. Wind
gusts to 32 knots until 04Z, then to 25 knots after 04Z.
Nebraska TAFS...MVFR at Chadron until 03Z, then IFR until 16Z,
then MVFR.
VFR at Alliance until 02Z, then MVFR until 04Z, then IFR until
18Z, then MVFR. Wind gusts to 37 knots until 02Z, then to 30 knots
after 02Z.
VFR at Scottsbluff until 04Z, then IFR until 18Z, then MVFR. Wind
gusts to 38 knots until 02Z, then to 28 knots after 02Z.
VFR at Sidney until 04Z, then MVFR until 06Z, then IFR until 18Z,
then MVFR. Wind gusts to 34 knots.
&&
.FIRE WEATHER...
Issued at 323 PM MDT Wed Apr 1 2020
Cold with a wintry mix expected through early Friday morning, with
little fire concerns through the short-term. Will begin a warming
trend over the weekend with temperatures reaching into the 50s
next week.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Weather Advisory until midnight MDT Thursday night for
WYZ116.
Winter Weather Advisory until 9 PM MDT Thursday for WYZ104>106-
109>111-113.
Winter Storm Warning until 9 PM MDT Thursday for WYZ101>103-112-
114.
Winter Weather Advisory from 6 AM to 9 PM MDT Thursday for
WYZ115.
NE...Winter Weather Advisory until midnight MDT Thursday night for
NEZ002-095.
&&
$$
UPDATE...GCC
SHORT TERM...AB
LONG TERM...RE
AVIATION...RUBIN
FIRE WEATHER...AB
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
943 PM CDT Wed Apr 1 2020
.UPDATE...
Issued at 940 PM CDT Wed Apr 1 2020
Based on observations and the HRRR`s faster movement with the cold
front, have sped up the passage of the front through the forecast
area. The hourly temperatures looked to be fairly good, although
I`m not sure if it`ll get quite that warm in the southeast. The
00z HRRR and even the 00z NAM show the front through the majority
of the forecast area by 18z Thursday. Mainly sped up the wind
forecast to show the frontal passage. Also included a bit more
coverage for drizzle late tonight/early Thursday. Think the chance
for drizzle as this front moves in tonight towards morning is
fairly good and tried to increase that potential after 9z.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 358 PM CDT Wed Apr 1 2020
The biggest issue in the short term involves a slow-moving, yet
strong cold front that will begin moving through our CWA perhaps
toward 05Z Thursday (midnight tonight), and will not clear our CWA
until perhaps 23Z Thursday (6pm Thursday). Timing of the front
through the tri-cities is shaping up to be roughly 7 am at Kearney
to around 9 am at Grand Island, and 10 am in Hastings, NE from
current best estimates from short-term numerical models. This will
probably mean a morning high in the lower 50s for the tri-cities,
before dropping like a rock through the afternoon into the 30s by
mid to late afternoon. NAM surface temperatures suggest that we
could start getting to freezing or below for places like Ord as
early as 1 pm Thursday. These times should not be taken as an
exact forecast, but rather as estimates by looking at latest
trends in short term and high resolution models. Our thinking will
almost surely change a bit as we get closer to Thursday/Thursday
night and we can tell more exactly where and how fast the cold
front seems to be moving.
Inverted and saturated low-level along with stubborn mid-level dry
air could create a bit of a headache for freezing drizzle potential
as surface temperatures drop below freezing during the afternoon and
evening from northwest to southeast. It appears that at least
elevated surfaces stand a good chance at a bit of ice accumulation
during this period. For the tri-cities, it appears this may start
occurring as early as 6-7 pm Thursday as cold air advection
ensues. Warm ground temperatures will probably resist a quick
freeze up initially, but even so, eventually ground temperatures
could start to get cool enough to allow perhaps a bit of icing on
roadways by overnight Thursday night before ending early Friday
morning as the surface high helps scour out our precipitation
chances. To add to the complexity, we could saturate mid-levels
from time to time to give us a few snowflakes added as well,
although it does not appear that this would be a big snow producer
in the post-frontal regime.
.LONG TERM...(Thursday night through Wednesday)
Issued at 358 PM CDT Wed Apr 1 2020
Overall synoptic pattern continues to be rather active, bringing
in multiple waves kicked out by a mean trough over the
northwestern CONUS. Temperatures could be a virtual roller coaster
over the course of the long term, starting out cold, turning much
warmer, and cooling at bit by the end by Wednesday.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Friday)
Issued at 634 PM CDT Wed Apr 1 2020
VFR conditions currently with breezy south winds will change by
the end of the forecast to IFR and breezy north winds.
Breezy south winds will decrease this evening as the sunsets and
they will remain light until the front moves through Thursday
morning into early afternoon at the terminals. The front will
change winds to the north and be breezy.
Ceilings will decrease after 09-10z from MVFR to IFR around
sunrise. There is a chance for light rain or drizzle during the
morning hours, but confidence is not high on how this will develop
and have left the forecast dry for now. While I cannot guarantee
the forecast will stay dry, the best chance for preciptiation is
after the 24 hour valid period of these TAFs.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
UPDATE...Billings Wright
SHORT TERM...Heinlein
LONG TERM...Heinlein
AVIATION...Billings Wright
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
520 PM MDT Wed Apr 1 2020
.DISCUSSION...(This Evening Through Wednesday)
Issued at 232 PM MDT Wed Apr 1 2020
Deep NW CONUS upper trough and associated front side jet
continues to dig into the region as a potent cold front surges
south. Decent moisture advection south of the region will set the
stage for a period of moderate to heavy snow over parts of the
area, with concentrated FGEN expected to support a band of heavy
snow across a small subset of the region. LSA increasing across
the region as the upper jet noses east. This will continue to
support scattered showers over the SE half through the afternoon
with windy conds as the cold front shifts south. As the main upper
trough starts to shift closer the region. LSA will increase with
precip becoming more widespread. Main concern tonight will be an
expected area of concentrated FGEN. Hires models have been picking
up on this to some degree. However, given the strong cold frontal
surge ongoing across the region, prefer the NAM solution (as
opposed to the RAP HRRR) as to where the strongest concentrated
FGEN will develop. Both the 12Z and 18Z runs continues to display
a robust band from southern Weston county NE into central SD.
Snowfall amounts in the band will be intense for a period with
strong lift centered in the DGZ where steep mid level lapse rates
will be in place. Would not be surprised if there is some thunder
in this band given the intense nature of lift combined with steep
mid level lapse rates, With adjusted QPF for this concern, opted
to upgraded the adv for the area where the expected convective
band will develop. Winds dont look too bad, but given the
degree of CAA combined with expected snowfall, patchy to areas of
reduced vis and drifting can be expected. Further SE over scentral
SD, dry slotting will support freezing rain at times with little
to no snow accums. There will be the potential for a tenth or so
of ice accums, mainly on elevated sfcs. This system will begin
to exit the region tomorrow afternoon west-east with precip
ending. Clearing on the backside will set the stage for very cold
temps, esp in the west and over deeper snow cover. Temps there
could drop below zero. Semi-active but warmer flow in store after
Friday, with temps in the 50s and 60s again by early next week.
&&
.AVIATION...(For the 00Z TAFS Through 00Z Thursday Evening)
Issued At 510 PM MDT Wed Apr 1 2020
Conditions continue to deteriorate across the area with showers
and ISOLD TSRA over south west and south central SD. MVFR
conditions continue with IFR/LIFR conditions spreading across
northeastern WY, the BLKHLS and much of west this evening and
central/southern SD later tonight. This storm will bring
widespread, accumulating snow to the area with IFR and LIFR
conditions through midday Thursday. As the storm begins to move
out late Thursday, conditions will begin to improve slowly from
west to east.
&&
.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Winter Storm Warning until midnight MDT Thursday night for
SDZ024-028-029.
Winter Weather Advisory until 6 AM MDT Friday for SDZ043-044.
Winter Weather Advisory from 1 AM Thursday to 7 AM CDT Friday
for SDZ046-047-049.
Winter Weather Advisory until midnight MDT Thursday night for
SDZ027-030-041-042-074.
Winter Weather Advisory from 9 PM this evening to midnight MDT
Thursday night for SDZ001-002-012.
Winter Storm Warning until midnight MDT Thursday night for
SDZ013-014-025-026-031-032-072-073.
WY...Winter Storm Warning until midnight MDT Thursday night for
WYZ057.
Winter Weather Advisory from 9 PM this evening to midnight MDT
Thursday night for WYZ071.
Winter Storm Warning until 3 PM MDT Thursday for WYZ055-056-058.
Winter Weather Advisory until 3 PM MDT Thursday for WYZ054.
&&
$$
DISCUSSION...JC
AVIATION...MLS