Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/08/17

Area Forecast Discussion...UPDATED

National Weather Service Aberdeen SD

 731 PM CDT Fri Apr 7 2017


UPDATE Issued at 621 PM CDT Fri Apr 7 2017

Will allow the wind advisory to expire at 7pm. Winds continue to
slowly diminish, but there are still a few sites reaching avisory
criteria.

UPDATE Issued at 558 PM CDT Fri Apr 7 2017

Cancelled the RFW a little early this evening. RH was only meeting
criteria as winds diminished to 15 to 20 mph. No sites within the
warned area were meeting criteria this evening. Gusty winds will
linger across the east through the evening, but are expected to
slowly diminish after sunset.

&&

.SHORT TERM...(This Evening through Saturday)
Issued at 334 PM CDT Fri Apr 7 2017

Forecast challenges continue to swirl around fire weather conditions
heading into the first of the weekend.

Currently, under a mostly sunny sky, temperatures are warming
through the 60s and 70s and breezy to rather windy southerly
winds continue. A Wind Advisory remains in effect across
northeast South Dakota until 7 PM CDT for sustained winds around
30 mph and gusts up to 45 mph.

Also, a Red Flag Warning continues until 8 PM CDT this evening
across Fire Weather Zones 267 and 270 due to a combination of much
above normal warm temperatures, very dry air and breezy south-
southwesterly surface winds. Very dry conditions and above normal
warmth will stick around through Saturday out ahead of a cold
front`s passage. The cold front will push its way across the region
late tonight through Saturday afternoon. Expect elevated fire
weather conditions again Saturday afternoon along and ahead of this
frontal passage. When the front shifts winds to northwesterly, there
is the potential for some preliminary strong gustiness, before
conditions settle down to just breezy northwest winds for a few
hours. The airmass behind this frontal passage will gradually cool
things down during the second half of the weekend. Relative Humidity
values will recover some as well. Along with the precipitation
chances later in the period, these cooler/higher moisture conditions
will considerably reduce grassland fire danger indices.

The airmass tonight and Saturday will remain warm and dry. Winds
will continue from a south-southwesterly direction but not as
strong, except up on and in the lee of the Prairie Coteau where
breezy conditions are possible. The aforementioned cold frontal
passage on Saturday should be a dry frontal passage, and initially
could pack a bit of wind gustiness punch post-frontal, especially
over north central South Dakota. Earlier in the day a few iterations
of the RAP model`s 0.5km wind progs had increased to between 45 and
50 knots in a slim north/south corridor running right behind the
fropa/wind-shift. The latest RAP output from 19Z appears to have
backed down to more like 35 to 40 knots immediately post-frontal.
This may be something to closely monitor for the rest of the evening
and overnight (strength of initial post-frontal wind gusts).

.LONG TERM...(Saturday Night through Friday)
Issued at 334 PM CDT Fri Apr 7 2017

A pronounced low pressure system will slowly cross the region
Saturday night through Monday evening. WAA showers and thunderstorms
are possible Saturday night/Sunday morning, depending on the
location of the LLJ. Weather conditions Sunday and Monday will be
rather interesting and complicated. The GFS suggests the upper level
trough will become slightly negatively tilted with clearing,
destabilizing conditions possible by midday. If this occurs, then
there is the potential for a few stronger storms Sunday afternoon.
Otherwise, colder air will begin to move into north-central and
western SD Sunday evening through Monday morning with PCPN gradually
changing over to all snow. Snowfall amounts of 1-3 inches will be
possible in north-central SD. Pcpn will slowly end from west to east
on Monday as the storm system pushes east.

Dry conditions will not last long as another storm system will cross
the region Tuesday night through Wednesday with additional showers
and thunderstorms expected. Of note, the GFS is the faster model
solution and brings this system through before 12Z Wednesday.
Thursday and Friday should be dry as upper level ridging builds into
the region.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday Evening)
Issued at 621 PM CDT Fri Apr 7 2017

VFR conditions are expected through the period. Gusty southerly
winds will diminish tonight and shift to the northwest on Saturday
behind a front.


&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&

$$

UPDATE...Wise
SHORT TERM...Dorn
LONG TERM...SD
AVIATION...Wise




Area Forecast Discussion

National Weather Service Cheyenne WY

 926 PM MDT Fri Apr 7 2017

.UPDATE...
Issued at 914 PM MDT Fri Apr 7 2017

We have decided to leave the high wind warning for Arlington and
the Laramie in tact during the next 18hrs. Latest low level water
vapor imagery is showing some shortwave energy moving northeast
out of Utah with pretty good mountain wave activity in its wake.
The models are also hinting at a 50-55kt of 700mb jet energy
moving through southern Wyoming late tonight into tomorrow
morning. Otherwise, it looks like a fairly quiet night. Latest
HRRR is showing a decent shot of some convection developing in in
Carbon County late tomorrow afternoon into tomorrow evening. Not
much cape is associated with this convection, but there is a lot
of strong winds aloft which may cause some showers and isolated
thunderstorms with some strong winds.

UPDATE Issued at 700 PM MDT Fri Apr 7 2017

We did lower wind speeds a bit tonight except in the wind prone
area of Arlington where the high wind warning remains in effect.
The models are showing the local height gradients weakening
with the thicker cloud cover continuing to stream across the area.
This may limit the potential to reach high wind criteria. We will
leave the warning in effect for now, and see how the trends go

&&

.SHORT TERM...(This evening through Sunday)
Issued at 212 PM MDT Fri Apr 7 2017

Tonight...Southwest flow aloft strengthens as a weak cold front also
passes west to east across our counties. Although 700 height
differences from Craig to Casper are not all that impressive this
evening, the models prog 50 knots of wind at 700 mb and with current
gusts of 40 to 50 mph in the Arlington area, would not be surprised
at all to see some gusts exceed 60 mph tonight, thus have upgraded
the Arlington zone to a high wind warning starting at 6 pm. Quite
mild overnight with nearly all low temperatures in the 40s due to
decent mixing.

Saturday...Strong southwest flow aloft continues and with progged
low and mid level winds, felt confident enough to upgrade to a high
wind warning for the Laramie Valley and Laramie. Continued mild
temperatures, especially east of Interstate 25 with downslope
warming despite cloud cover. Enough low and mid level moisture to
aid in the production of scattered afternoon showers west of a
Douglas to Laramie line.

Saturday night...Next powerful negatively tilted shortwave trough
aloft moves into western Wyoming with a strong cold front entering
our western counties after midnight. Shower chances will continue
west of a Douglas to Laramie line along the cold front and
baroclinic band, otherwise dry. Not as mild as Friday night.

Sunday...Powerhouse closed low aloft moves to northeast Wyoming in
the afternoon with strong cold air advection across our counties.
Based on the strength of the low and mid level gradients, some
locations across southeast Wyoming will likely be near or exceed
high wind criteria, though felt it would be most prudent to hold off
on high wind watches with the expected high winds at Arlington and
Laramie tonight and Saturday. Considerably cooler with strong cold
advection in the wake of the cold front. Wraparound showers most
common north of a Laramie to Chadron line closer to the deeper
moisture associated with the closed low aloft.

.LONG TERM...(Sunday night through Friday)
Issued at 212 PM MDT Fri Apr 7 2017

We will keep chance PoPs for scattered snow and rain showers going
across the northern zones and out west in the mountains Sunday
night into Monday, then we maintain a dry period Tuesday through
Thursday as GFS and ECMWF keep most shortwave energy to our north.
We will bring in some small PoPs towards late next week as the
upper flow goes southwesterly and we see the potential for
increased shortwave activity ejecting northeast from a larger
trough moving onshore in California.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 542 PM MDT Fri Apr 7 2017

VFR conditions are expected across the area tonight and tomorrow,
with gusty winds continuing to be the main issue. Winds will begin
to drop off over the next 1-2 hours for sites east of the Laramie
Range. KRWL and KLAR will continue to have gusts around 30kts
overnight. Tomorrow afternoon, gusts ranging from 25 to 35 kts are
expected, across all sites. High to mid level clouds will
continue to hang over southeast Wyoming and western Nebraska
tonight and tomorrow.


&&

.FIRE WEATHER...
Issued at 212 PM MDT Fri Apr 7 2017

Red flag warning continues until early this evening along and
east of Interstate 25 for gusty winds and low humidities. Slightly
higher humidities the next several days will limit fire weather
concerns.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...High Wind Warning from 6 AM to 6 PM MDT Saturday for WYZ115.

     High Wind Warning until 6 PM MDT Saturday for WYZ110.

NE...None.
&&

$$

UPDATE...REC
SHORT TERM...RUBIN
LONG TERM...JG
AVIATION...KC
FIRE WEATHER...RUBIN




Area Forecast Discussion...Updated

National Weather Service Saint Louis MO

 919 PM CDT Fri Apr 7 2017

.UPDATE...
Issued at 918 PM CDT Fri Apr 7 2017

Forecast still appears on track with only high clouds moving
across the area at mid evening. Latest surface analysis shows that
the ridge axis has moved into Illinois, and the RAP shows it
continuing to move east overnight. Latest indications are that
winds will pick up even in the eastern counties toward morning
which will lower the frost potential. Coldest lows will still
occur over the eastern counties where the current temperatures are
the coldest and the winds are the lowest compared to central MO
where winds will increase through the night.

Britt

&&

.SHORT TERM...  (Through Late Saturday Afternoon)
Issued at 210 PM CDT Fri Apr 7 2017

Not a lot of change thru the period from the prev forecast. Sfc
ridge continues to build ewd thru the region. Nwly winds will
gradually diminish this afternoon and evening and become sly as
the ridge axis passes. This is expected to allow temps to drop
fairly quickly this evening, then become steady. Temps across the
wrn half of the CWA may even rise somewhat late tonight as winds
begin to pick up.

This once again raises the question of frost potential for
tonight. Winds will eventually pick up from the south over ern
portions of the CWA and shud limit frost potential. Have used
temps that occurred over central MO this morning for the forecast
tonight over IL counties. The main difference is that IL has far
fewer low lying areas. With expected temps in the upper 30s and
dewpoints in the lower 30s, believe frost will be more difficult
to develop. Conditions are borderline across far ern counties, but
have held off issuing a headline attm.

Otherwise, with sly winds increasing on Sat and thermal ridge
pushing 10C to 12C 850mb temps into the area, expect temps to
reach the 70s.

Tilly

.LONG TERM...  (Saturday Night through Next Friday)
Issued at 323 PM CDT Fri Apr 7 2017

Temperatures on Sunday look quite warm due to the lingering
influence of the departing upper ridge axis, favorable southwest
winds at the surface, and mixing to near H9. Mixing does not look
as deep on Sunday compared to Saturday due to a stronger
temperature inversion between approximately H9-H85 on Sunday. Most
areas should reach the mid to upper 70s on Sunday, which is 10-15
degrees warmer than average.

SHRA/TSRA chances will increase on Sunday evening ahead of a low
pressure system, but the highest precipitation chances are on
Monday afternoon/evening associated with the passage of the
surface cold front and upper trough axis. Strong to severe
thunderstorms may be possible with this system given model
depictions of around 40kts of 0-6km shear.

Depending on the speed of the cold front, there may be a sharp
temperature gradient somewhere across the CWA on Monday
afternoon. Temperatures will be cooler on Tuesday within the
post-frontal air mass.

Dry weather is expected on Tuesday and Wednesday, but recent
model runs show much more disagreement (compared to 24hrs ago)
regarding a disturbance in either southern Canada or the northern
plains during this time period. This leads to lower confidence in
a dry forecast for Tuesday and Wednesday, especially if Monday`s
frontal boundary stalls in southern MO.

An upper ridge begins to build across the west-central CONUS towards
the end of the week. Model solutions depict a few weak disturbances
which attempt to undercut the ridge axis as well as a separate vort
max near the Great Lakes on the downstream side of the ridge. The
pattern resembles an omega blocking pattern on the GFS, but the
ECMWF shows a more slanted ridge axis. Precipitation chances late in
the week are tied to the evolution of these features, but there is
low confidence in the details because model solutions diverge
after 12z Thursday.

Kanofsky

&&

.AVIATION...  (For the 00z TAFs through 00z Saturday Evening)
Issued at 614 PM CDT Fri Apr 7 2017

Dry and VFR conditions are expected through the period. Winds will
turn out of the south after 06-12Z as high pressure moves off to
the east.

SPECIFICS FOR KSTL:  Dry and VFR conditions are expected through
the period. Winds will turn out of the south after 12Z as high
pressure moves off to the east.

Britt

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&

$$

WFO LSX




Area Forecast Discussion

National Weather Service Pocatello ID

 137 PM MDT Fri Apr 7 2017

.SHORT TERM...Tonight through Sunday. Clouds and showers continue
over a good chunk of eastern Idaho this afternoon. Most of the
activity is along and behind the first front/windshift which
appears to be pushing into the Magic Valley as of 1pm. Expect
showers to continue increasing from west to east through early
evening. We`ve seen a couple of storms already and where we can
maximize instability, we will likely see more isolated
thunderstorms. Expect locally heavy rain or mountain snow along
with small hail and gusty winds over 45mph. The overall pattern
has been breezy today but not enough to trigger a Wind Advisory
but that could change between now and midnight. That boundary
pushes into the eastern highlands and stalls/washes out there
overnight. That area will see the best chance of rain and snow,
with less shower activity to the northwest for a few hours. Snow
levels drop to around 6000-6500ft in most areas. We will see a
pocket of snow levels down to valley floors across the southeast
corner, where heavier precipitation is expected. This will allow
for rain or a mix to change to all snow. Wet and slushy
accumulations are forecast even at those valley floor locations
like Soda Springs, Grace and Montpelier. Showers will gradually
increase areawide tomorrow as the main storm and stronger cold
front arrives in the afternoon from the west. The GFS shows less
of this front vs the other models so we discounted its forecast to
some degree. Expect more thunderstorms tomorrow. These storms may
end up a little stronger but still not necessarily severe.
However, we proved a few days ago...all it takes is one to change
that. Snow levels drop to valley floors by tomorrow evening.
Behind tomorrow`s front it will be windy. The question is WHEN the
winds behind the front develop. Some data shows that occurring
late in the afternoon and extending all the way into Saturday
night, will other data shows them holding off until Saturday
night. For now, we will NOT issue a Wind Advisory. By Sunday
morning, most of the precipitation (SNOW) will be confined to the
central mountains and eastern highlands. There is some hint of a
convergence band shift across the Snake Plain anywhere from
Pocatello northward. We did include a better chance across the
Plain in these areas until that becomes more clear. IF we see this
band form, that will be any real chance of seeing measurable snow
across the Snake Plain. We are only talking about an inch or so at
most. Road temperatures may cool off enough for a few hours to
create slushy conditions.

The WINTER WEATHER ADVISORY will continue for the southeast
highlands as we are expecting up to 8" (perhaps locally higher)
at/above pass level and up to 3" for some valley locations.
Slushy/slick roads are possible. We will also continue with a SPS
advertising some snow for the central mountains and Upper Snake
Highlands especially tomorrow night and Sunday. We could see up to
5" down to around 6500ft with locally higher amounts well above
pass level.  Keyes


.LONG TERM...Sunday night through Friday. Main concern early on is a
short wave ejecting out of the mean upper trough in the Pacific.
This is set to impact the Central Mountains late Monday morning,
expanding south and eastward to the rest of the forecast area by
Monday afternoon/evening. It appears to be a fast-moving wave, thus
precip amounts will be fairly light. Ridging will begin to set up on
Tuesday leading to drier conditions, but warm air advection
Wednesday may help trigger some precip, though the GFS has
downscaled coverage of precip over the past couple runs. The ECMWF
remains dry for Wednesday, and does so through Thursday night. Both
models project a deeply amplified pattern late in the week with
strong southerly flow continuing into Friday. The GFS is slightly
faster in advancing precip into the area Thursday night while the
ECMWF holds off until around mid-day Friday. Temps should be above
normal Wednesday and Thursday as a result of the amplifying
southerly flow and concomitant warm-air advection. Hinsberger

&&

.AVIATION...Active pattern through the forecast period as synoptic
lift increases as a cold front pushes through this afternoon. Winds
should remain strong through this evening, especially along the
front. Currently downslope flow is keeping low levels dry, and
little precip is reaching the ground at KPIH, KIDA and KBYI. GFS and
NAM depict heavy banded precip occurring along and behind the cold
front. HRRR also suggests heavy banded precip this evening, but
placement will be hard to pin down. Frontal forcing and instability
will drive some convection this afternoon, but no severe activity is
anticipated at the terminals today. Ceilings will likely drop to
MVFR in the heaviest rain, and may drop to IFR. LIFR cannot be ruled
out, especially at KSUN. Hinsberger

&&

.HYDROLOGY...The FLOOD WARNING for the Portneuf at Pocatello
continues and is still expected to rise to just above Moderate
flood stage over the weekend. Based on the latest forecast and
expected rain/snow, we re-issued the FLOOD WARNING for the Bear
River at the Wyoming border. That should rise above flood stage
sometime Sunday. Again, it all depends on the placement of heavier
precipitation (which might be downstream of there) but it probably
won`t take much. The FLOOD ADVISORY for southeast Bear Lake
County remains in place as well. We`ll need to watch flows below
Magic Dam once again as new rain and snowmelt could lead to flows
peaking again around 5500cfs, which would produce more flooding
between the dam and ID-75. Keyes


&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 6 PM this evening to 6 AM MDT
Sunday for IDZ023-025.

&&

$$