Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/19/19
Area Forecast Discussion
National Weather Service La Crosse WI
454 PM CST Wed Dec 18 2019
.SHORT TERM...(This evening through Thursday)
Issued at 237 PM CST Wed Dec 18 2019
Fairly quiet weather is expected in the short term, with the main
forecasting challenge being cloud potential overnight. Afternoon
surface analysis showed a ridge of high pressure centered over
Wisconsin. Temperatures were below normal, with many areas in the
single digits or low teens. Mid to high level clouds were streaming
southeastward across the area, with clearing noted across western
portions of the area.
As the high continues to slide east tonight, winds will turn
southerly with warm air advection kicking in. This will likely help
to limit how far temperatures fall this evening, even as clearing
works east. While the overall atmospheric profile looks pretty dry
still this afternoon, some guidance is hinting at enough moistening
in a narrow chunk of the low levels late tonight/early Thursday
morning to produce low clouds or even patchy fog. With dry air in
place and winds staying up for a portion of the night, confidence is
not high in the extent of clouds or whether patchy fog will occur,
but it will have to be monitored.
Thursday looks much warmer than today, as cold air aloft scoots east
of the area allowing highs to reach the 20s and 30s. Other than the
aforementioned possibility of morning clouds, there could be some
partly cloudy skies/sunshine for a while Thursday under mid-level
ridging before high clouds begin to fill back in.
.LONG TERM...(Thursday night through Wednesday)
Issued at 237 PM CST Wed Dec 18 2019
Mid-level ridge moves east of the region Thu N/Fri, pushed off by
fairly strong pv-anomaly passing through the Northern Plains.
NAM/GFS/ECMWF/GEM all showing surface cyclogenesis over MN by Friday
morning with warm air advection/isentropic upglide taking place
across our area. This system gets quickly shunted northeast of the
area by Friday evening. Could see a brief bout of freezing drizzle
in the morning mainly north of our forecast area where better
saturation from forcing takes place. For now, will keep a dry
forecast going but will definitely keep a close eye on how far
south/possibly into our area this freezing potential gets.
Otherwise, plan on highs Friday pushing well into the 30s, maybe
even a few lower 40s across portions of far northeast IA/southwest
WI in snow-free areas.
The weekend into early next week looks quiet and mild as mid-level
ridging dominates the central CONUS. Temperatures look to be some 10
degrees above normal with highs in the 30s/40s and lows in the mid
20s/lower 30s.
Deepening southwest flow aloft/digging trough out west will start
sending moisture/chance of precipitation toward the area Tuesday
night/Christmas Day. ECMWF would keep our area dry through Christmas
with ridging holding in place whereas the GFS would bring an area
low pressure/chance of rain through the region. Will go with model
consensus for now which yields low-end chances. Otherwise, remaining
above normal temperature-wise with highs Christmas Day in the
30s/lower 40s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 454 PM CST Wed Dec 18 2019
Southwest low level flow was developing across the area as an area
of high pressure was moving into the Ohio River Valley. Both the
18.18Z NAM and 18.21Z RAP show an area of higher relative humidity
at 925 mb over western Minnesota and Iowa and move this
east/northeast while expanding it through the overnight hours as
it moves across the local area. Right now, there are no clouds
associated with this moisture and the suggestion in the hi-res
meso-models and forecast soundings is that clouds will form in
this moisture field overnight resulting in a MVFR ceiling.
However, confidence is not high in this scenario and will continue
the trend from the previous forecast of showing some scattered
lower clouds but no ceiling.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...Lee
LONG TERM...DAS
AVIATION...04
Area Forecast Discussion
National Weather Service North Platte NE
540 PM CST Wed Dec 18 2019
.SHORT TERM...(This evening through Thursday night)
Issued at 248 PM CST Wed Dec 18 2019
Near term concerns revolve around temperatures the next few days.
Otherwise, quiet weather is expected from now through the weekend as
the area falls under the influence of shortwave ridging in a split-
flow pattern before transitioning to high-amplitude northerly flow
for the start of the weekend as additional ridging approaches
from the west. Ridging overhead at the present moment is centered
over the Texas Panhandle and will be kicked out by an approaching
shortwave trough currently moving onshore southern California with
it moving across the Rockies and onto the southern Plains late
tomorrow. Ridge axis will pass late tonight into early Thursday
with low-level winds backing to the southwest in response. Winds
never really go light tonight with h85 flow increase from midnight
to sunrise on Thursday, limiting any concerns for fog Thursday
morning. Given recent snowmelt and forecast lows, however, cannot
rule out some patchy fog developing for portions of western
Nebraska. Favored locations would be low-lying areas shielded from
winds like river valleys. Crossover temperatures further support
this thought with some hi-res guidance such as the NAM and NAM
Nest painting lowered visibilities across the area but the RAP and
HRRR aren`t overly optimistic and the SREF only shows 40% or less
probabilities. Will leave out of the forecast for now but pass on
the subsequent shifts to monitor overnight. Have had a stretch of
mornings where low temperature forecasts have not been cold
enough and given non-zero snow depth across much of the area have
lower temperatures tonight as a result with values generally in
the teens and low teens for some.
Thursday is a tricky forecast regarding high temperatures. Will see
the day start with southerly-southwesterly flow in the low-levels
and similar if not slightly warmer h85 temperatures. In addition, a
weak surface cool front associated with northern stream system will
move into the area and push through during peak heating of the day.
This may help lead to a degree or two of warming thanks to
compressional heating but lingering snow and a slow rise to
temperatures seen Wednesday makes the temperature forecast medium
confidence at best. Thinking tomorrow is a good day for beating our
stretch of cooler than expected temperatures and so have increased
daytime highs slightly with values generally in the 40s to near 50
across the far southern tier of counties. Winds will shift from
southwest to west-northwest during the daytime as the frontal
boundary pushes through but fropa is expected to be dry as little in
the way of appreciable moisture is available. Temperatures Thursday
night will be similar if not slightly warmer than Wednesday night as
values fall into the teens to low 20s.
.LONG TERM...(Friday through Wednesday)
Issued at 248 PM CST Wed Dec 18 2019
Beginning 12z Friday. Little in the way of sensible weather is
expected Friday through the start of the holiday week. Mid-level
height rises begin during the daytime on Friday and persist through
the weekend right into late Sunday night. Dry conditions will
continue with temperatures climbing to well-above normal values for
late December. Normal highs for this time of year are generally in
the mid to upper 30s with forecast highs generally reaching the 50s
for all locations. Some NWP guidance even hints at locations hitting
60+ degrees at least Sunday if not Saturday and Sunday, but will
hold off on forecasting near record territory for the time being but
look for these temperatures to increase should there be any trend.
Thereafter guidance begins to diverge and the forecast becomes more
murky. Modest height falls will begin by Monday locally, however,
without any large impulse of energy/lift we should expect to see dry
conditions continue Monday and right on into Christmas Eve on
Tuesday. This will be about as favorable a scenario for little if
any travel impacts prior to the holiday itself we`ve seen in recent
years but attention turns quickly to what various ensemble solutions
and global deterministic models have hinted at for the past 24-48
hours. A deep trough will move onshore southern California late
Tuesday night and get caught up in the southwest flow which will
steer it onto the central Plains sometime in the late Tuesday into
Wednesday timeframe. This trough will look to take on more of a
negative tilt open wave as it passes through our region. Model
discrepancies abound which is putting it modestly but general
thinking is that precipitation chances will be on the increase
towards mid-week and Christmas Day. These aforementioned
discrepancies greatly limit confidence in precipitation type and
timing and as a result, what impacts may occur. Consider this
forecast very low confidence at the present time but just know that
those with travel plans for the Holiday anywhere in the Central
Plains post-Christmas will need to monitor the forecast between now
and then to potentially adjust plans as necessary. Worth mentioning
again this is a low confidence forecast and impacts to the local
area are far from guaranteed so stay tuned. Beyond that, the pattern
looks to remain fairly active as additional troughing in the west
will allow more disturbances move into the area and bring more shots
at precipitation.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 538 PM CST Wed Dec 18 2019
Over the next 24 hours, scattered high clouds will track across
western and north central Nebraska with ceilings around 25000 FT
AGL. Ceilings will fall to 20000 FT AGL Thursday afternoon.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...Jurgensen
LONG TERM...Jurgensen
AVIATION...Buttler
Area Forecast Discussion
National Weather Service Paducah KY
111 PM CST Wed Dec 18 2019
.SHORT TERM...(Tonight through Friday night)
Issued at 110 PM CST Wed Dec 18 2019
Low clouds across the area should diminish in coverage through the
afternoon and possibly early evening (for west KY). We had to rely
fairly heavily on prior runs of the HRRR and Daytime Snow/Fog GOES-
16 imagery to time the slow decrease in clouds.
At the surface high pressure will move across the region tonight,
and set up to our east Thursday and Friday, allowing for modest
return flow. NW flow aloft will be replaced by s/wv ridge that will
move slowly east over the area, followed by SW flow ahead of
southern Plains low Friday.
With a generally dry airmass in place, no precipitation is
anticipated. Just an increase in clouds by Friday. Temperatures
tonight should fall quickly once the clouds are gone early on.
Temperatures will moderate into the mid to upper 40s Thursday and
Friday, with lows in the upper 20s to lower 30s.
.LONG TERM...(Saturday through Wednesday)
Issued at 110 PM CST Wed Dec 18 2019
From this weekend through Christmas Eve or so, the PAH forecast area
will be more or less under a ridge axis of high surface pressure,
roughly oriented southwest-northeast, which should keep the surface
winds in check and make it more difficult for measurable pcpn to
occur. Meanwhile, slack mid level flow in a larger scale split
pattern will initially prevail over us well to the north of a low
pressure system moving through the Gulf Coast states. There
continues to be the occasional hint that some measurable pcpn
associated with the system may creep just across the TN state line
over the weekend, whether it be the 12Z deterministic ECMWF or a few
GEFS members, but it is believed that model consensus continues to
be strong enough for a dry forecast over the weekend at this time.
Whatever cloudiness occurs should be most prevalent in the Pennyrile
region of KY.
By Mon, strong mid level ridging induced by a strongly amplified
shortwave in the western CONUS is forecast to dominate the country`s
midsection. These height rises should translate to afternoon surface
temps in the 50s for us, perhaps attaining 60 degrees near the TN
state line. Lows are forecast to be above freezing everywhere on Day
6 and Day 7. Just beyond the Day 7 period, deep moist southwesterly
flow may bring some showers back to the forecast, but for now,
Christmas Day (Wed) looks dry, mostly cloudy, and unseasonably
warm.
&&
.AVIATION...
Issued at 1119 AM CST Wed Dec 18 2019
Stratus lingers across much of the area at midday. Clearing was
working into southern IL and will make into southwest IN through
mid afternoon. It may take until the end of the day to shrink in
coverage over west KY into SEMO. Once the clouds go away, should
be mostly clear through Thursday. Light northwest winds will
become variable overnight, then south 5 to 10 kts Thursday.
&&
.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...None.
IN...None.
KY...None.
&&
$$
SHORT TERM...08
LONG TERM...DB
AVIATION...08
Area Forecast Discussion
National Weather Service Pocatello ID
145 PM MST Wed Dec 18 2019
.SHORT TERM...Tonight through Saturday. Early afternoon satellite
imagery was showing a weak upper trough lifting NE across the region
this afternoon with very little in the way of sensible weather
impacts noted across SE Idaho. Further upstream, a very moist west
flow/Atmospheric River was advancing east through the Pacific toward
the Oregon/Washington coast. Numerical models continue to show the
brunt of the Atmospheric River impacting Washington, Oregon and the
Idaho panhandle and with each successive model run showing less and
less impact on the CNTRL mountains. Storm total accumulations for
Thursday and Friday currently fall below advisory levels for the Sun
Valley and Sawtooth region and thus no highlights are planned for
this forecast cycle. For Friday night into Saturday, a ridge expands
northward through Wyoming into ERN Montana as the next Pacific
trough takes shape off the NW coast with mostly dry conditions
anticipated across SE Idaho. The main moisture plume extends from
NRN California north-northwestward ahead of the trough into the
Canadian Rockies, however there may be enough advance moisture to
squeeze out a shower or two over the CNTRL mountains. For now the
National Blend of Models was dry and we have trended in that
direction until we see a change. With the onset of unsettled
conditions over the next several days, temperatures are expected to
warm through climatological norms and the going forecast reflects
this current thinking. Huston
.LONG TERM...SATURDAY NIGHT THROUGH CHRISTMAS DAY. Strong consensus
continues among the long-range models that SE Idaho will reside on
the western edge of (yet still under the influence of) a longwave
ridge of high pressure through Sun, with dry conditions. With a SW
flow throughout the atmospheric column ahead of our next trough,
temps will moderate into the upper 30s/low 40s, about 10-15 degrees
above climatological norms for this time of year. Forecast
confidence remains high for Sun.
The ridge is still forecast to more definitively move east starting
Mon, allowing longwave troughing to become established across much
of the western half of the US, signaling a return to a more active
weather pattern for our region. Indeed we waste no time, as a
shortwave ejects NE across the northern Rockies Mon/Mon night, while
a stronger shortwave or even weak closed low pressure center works
SE down the Pacific coast, rounds the base of the trough across
southern CA, and then tracks NE across NV/UT/WY Tues into Christmas
Day. The GFS/ECMWF/Canadian all differ a bit with respect to
strength of both features, and how to handle potential messy
interactions between them in the form of timing and placement of
various rounds of precip. Thus, confidence in the details remains
quite low from Mon into Christmas Day. Overall trends over these 3
days favor temps cooling a few degrees each day back closer to
seasonal norms (highs topping out in the 30s by Christmas Day), and
at least a chance of (largely snow) showers each day just about
anywhere, highest as usual in the mntns vs. the Snake Plain. We took
NBM guidance for PoPs, increased them by about 5-7%, and
broadbrushed them a bit more from Mon eve onward to account for the
low confidence/model differences and ensure we keep a mention of
snow showers in the forecast. As far as SE Idaho seeing a white
Christmas, overall chances aren`t bad at all with the cooling temps,
active large-scale pattern, and a couple systems/features to play
with. Stay tuned and jolly! - KSmith
&&
.AVIATION...Quiet and low-impact conditions for aviation are
expected for the next 24 hours or so, with VFR cigs/vsbys and high
forecast confidence through tonight. Some BKN to almost OVC high-
level cloud cover continues to drift across the region this
afternoon. This should thin out a bit tonight, with the focus then
shifting to increasing mid-level clouds working in from the west as
a dry shortwave trough works across the region, especially after 10-
13z or so depending on the terminal. We massaged this into the TAFs
as a BKN deck using mostly NAM time-heights and HRRR guidance...the
12z MAV/MET suite seems perhaps a bit too aggressive (shoving decks
down below VFR tomorrow for some sites) compared to the rest of our
preferred guidance, so we avoided that for now. For several days now
models have also trended a little drier for our area with regards to
the atmospheric river of moisture forecast to hit the Central Idaho
Mountains, with the bulk of that flow perhaps now directed further
north toward the panhandle of Idaho. We still can`t rule out a few
snow showers getting into our CWA Thurs afternoon through Fri
afternoon (mostly just beyond the end of the current 18z TAF
period), but the activity may be fairly hit-and-miss, and confidence
is low on impacts to any given terminal. For now, we initiate VCSH
at KSUN after 10z tonight and will monitor forecast trends
especially among the high-res guidance, but even here there may not
be a ton of activity making into the Wood River Valley. Still, cigs
could drop into MVFR starting Thurs afternoon. - KSmith
&&
.PIH WATCHES/WARNINGS/ADVISORIES...None.
&&
$$