Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/24/19
Area Forecast Discussion
National Weather Service La Crosse WI
930 PM CST Mon Dec 23 2019
.SHORT TERM...(This evening through Tuesday)
Issued at 155 PM CST Mon Dec 23 2019
At 1 PM, under broken high clouds temperatures ranged from the mid
30s to mid 40s. These clouds were streaming along a weak frontal
boundary located over northern Iowa and northern Illinois.
For tonight and Christmas Eve, the front will move gradually north
as a warm front. With relatively dry air aloft, not anticipating
any precipitation with this front. The RAP is generating low
clouds and fog on Tuesday morning. Since the models have been
tending to over do this, opted just to mention some patchy fog for
now. With the 925 mb temperatures looking far too cold west of
the Mississippi River for tonight on Christmas Eve, opted to go
more with a blend of the GFS and ECMWF.
.LONG TERM...(Tuesday night through Monday)
Issued at 155 PM CST Mon Dec 23 2019
Upper level ridging will begin to push off to the east Tuesday night
into Wednesday as an upper level trough begins to work into the
western CONUS. This will leave the forecast area under southwest
flow with the general idea being that various bits energy slide
through and bring precipitation chances through the weekend. In
addition, temperatures will be remaining above normal, with highs
generally in the 30s and 40s, though a slight cool down will be seen
for the weekend.
The first precipitation chances will arrive by the early morning
hours on Christmas in the form of light drizzle or perhaps some
freezing drizzle depending on surface temperatures. Model soundings
indicate that saturation of the low levels looks to be fairly
shallow (less than 1 km) for much of the day, but would think the
forcing from the wave would be enough to lead to at least some
patchy light drizzle at times. The next wave comes Wednesday night
into Thursday, with a surface low passing by to the west and north.
Model soundings do indicate a deeper saturated layer across the area
with this particular wave, so chances for accumulating precipitation
would be higher than on Wednesday, with the highest chances closer
to the passing low. As far as type, still looks like liquid with
lack of in-cloud ice across the area. In addition, most of the area
should see lows above freezing Thursday morning, so not anticipating
much, if anything, in the way of ice accumulation, though will need
to keep an eye on the favored cold spots in central Wisconsin.
Surface high pressure will provide a break in the precipitation for
at least Friday, but model solutions diverge quite a bit going into
the weekend. The general idea is that a closed low over the desert
southwest will eject northeastward into the area, with various bits
of weaker northern stream shortwave energy moving in out of Canada.
Models differ greatly on the timing of these features, especially
the ejection of the low. Should the closed low phase with some of
the northern stream energy, a stronger system would impact the area
(e.g. 23.12Z GFS and several GEFS members). Bottom line, it looks
like we should see at least some precipitation from the low, but
confidence remains low in when, what type, and how much. Beyond
that, the overall trend looks to be cooler as upper level troughing
.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 930 PM CST Mon Dec 23 2019
Cigs: main forecast challenge is if mvfr/ifr cigs will impact the
TAF sites, along with potential for period of MVFR BR. All the
models saturate the near sfc layer along/north of a northward moving
warm front - with consensus generally favoring north of I-90 (more
in the I-94 corridor). For now, will stick this trend, keeping just
a high VFR cig. Will monitor trends closely and adjust as needed.
If this scenario holds, likely stay VFR for cigs until Wed as low
pressure system slides into the region and warm front edges back
WX/vsby: some fog progged to develop in light wind region across WI
later tonight. Could see some BR too in areas that still have snow
cover, thanks to melting, although winds are expected to be on the
increase this evening, which could limit that potential.
Winds: winds will become southeast later this evening with some
increase in the speeds. A bit more shift south on Tue, and some
decrease as pressure gradient slackens.
Issued at 155 PM CST Mon Dec 23 2019
It continues to look like Christmas Eve and Day will be among the 10
warmest. The following are the warmest Christmas Eves and Days for
La Crosse and Rochester.
La Crosse - Christmas Eve High Temperatures
1) 61F in 1889
2) 52F in 1893
52F in 1888
52F in 1877
5) 48F in 1881
6) 46F in 1940
46F in 1936
8) 44F in 1953
9) 43F in 2006
43F in 1963
La Crosse - Christmas Day High Temperatures
1) 55F in 1936
2) 54F in 1881
3) 46F in 1982
4) 45F in 1940
45F in 1912
6) 44F in 1928
44F in 1922
44F in 1877
10) 42F in 2014
42F in 2011
42F in 1953
42F in 1874
Rochester - Christmas Eve High Temperatures
1) 41F in 1953
2) 40F in 2011
40F in 2006
40F in 1957
40F in 1955
40F in 1940
7) 39F in 1936
39F in 1913
38F in 1908
Rochester - Christmas Day High Temperatures
1) 50F in 1936
2) 42F in 1928
3) 41F in 2011
41F in 1959
5) 40F in 1940
6) 39F in 1999
39F in 1994
39F in 1953
39F in 1943
10) 38F in 2016
38F in 1963
38F in 1954
38F in 1949
Area Forecast Discussion
National Weather Service Caribou ME
915 PM EST Mon Dec 23 2019
A cold front will push off the Downeast coast by around midnight
tonight. High pressure will build down from the northwest
Tuesday into Tuesday night then slide south of the region
Wednesday. A cold front will cross the area Wednesday night
followed by high pressure Thursday into Thursday night. A warm
front will lift across the region Friday followed by high
.NEAR TERM /THROUGH TUESDAY/...
9:15 PM Update: The cold front just came through Frenchville at
the top of the hour with a snow shower, wind shift into the
northwest, and a brief gust of wind to 40 mph. The cold front
will push off the Downeast coast late this evening. The best
chance of showers with the front will be across northern and
central Aroostook County, and it is unlikely that any showers
will make it south of Baxter State Park. The wind will pick up
and a colder air mass will follow, but not dramatically so. By
daybreak, lows will be in the teens across the Saint John Valley
to the mid to upper 20s along the coast. Made some minor
adjustments based on the latest observations and radar trends.
The cold front is expected to push through the region tonight
w/CAA. The GEM and HRRR do show some bands of precip across the
northern 1/2 of the CWA through late evening. The 12z UA showed
a jets streak of 45-50 kts in the 850-700mb layer across the
Ontario region this morning. Given the wsw flow aloft, this
feature looks like it will move across northern New England this
evening which will aid in shear. The NAM and RAP soundings
support strong shear of 40+ kts at 0-6km through late evening.
So, gusty winds near 30 mph are possible. The best moisture
appears to be limited below 700 mbs. There will be enough
forcing to support some activity w/rain-snow showers going over
to just snow showers by evening. Gusty winds could even reduce
vsbys through midnight in some areas across the northern
locales. Temps overnight will continue above normal.
Looks to be a windy day for Christmas Eve and much colder as NW winds
take hold and gradient remains tight, but it looks like there
will be a good deal of sunshine. Stayed close to the midnight
crew`s thinking of 10-20 mph sustained winds w/gusts to 30 mph.
Liked also the idea of some patchy blowing snow across parts of
the n due to fresh snow cover. Daytime temps will be back to
near normal readings.
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
A longwave ridge covers much of the country and will dominate the
weather pattern for the rest of the week. This will mean occasional
shortwaves sliding over the ridge and bringing weak fronts down from
the northwest followed by high pressure systems. Otherwise, mainly
dry weather will persist.
High pressure will build down from the northwest Tuesday night
bringing a mostly clear evening with a light northwesterly breeze.
This will be followed by some cloudiness, mostly over the north,
late at night with a weak front. Christmas Day Wednesday will be
mostly cloudy north and partly cloudy Downeast as a weak frontal
boundary slips in from the northwest. High pressure sliding into
Quebec will then push a weak cold front south across the area
Wednesday night bringing clearing and only moderately cooler air in
from the north. The high will bring sunshine Thursday. However, a
weak frontal boundary nearby to the southwest may bring some high
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
High pressure will slide south of the area Thursday night. A return
flow behind the high coupled with a weak occlusion ahead of a low
tracking into western Quebec will bring cloudiness into the area.
Some patchy light snow is possible in western areas late at night.
The occlusion/warm front will lift across the area Friday bringing
some light snow, changing to light rain from south to north but
possibly remaining all snow over the far north. A cold front will
follow Friday night followed by a breezy and moderately cooler day
on Saturday with a mostly cloudy sky north and partly cloudy
Downeast. Winds will diminish Saturday night. A storm system
approaching late Sunday into Sunday night may bring snow north and
snow to rain Downeast.
.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
NEAR TERM: Mostly MVFR at the northern terminals tonight and
into Tuesday morning, but brief LIFR in any snow showers until
around midnight. Conditions will improve to VFR Tuesday
afternoon. VFR expected at the Downeast terminals. A gusty NW
wind will follow a cold frontal passage tonight with wind gusts
to 30 knots. LLWS is expected from KPQI northward tonight.
For Tuesday, VFR but windy w/gusty NW winds 10-20kt.
Tuesday night: VFR. Light NW wind.
Wed: VFR, possibly lowering to MVFR north. Light and variable wind.
Wed night: VFR. Light N wind.
Thu: VFR. Light N to NE wind.
Thu night: VFR, possibly becoming MVFR late. Light S wind.
Fri: IFR in low clouds, light snow/rain. Light SW wind.
NEAR TERM: SCA was extended into Tuesday afternoon as the NW
gradient looks like it will hold on a bit longer w/the CAA.
Sustained SSW winds are expected to shift to the WNW winds
15-20 kts later this evening into tonight with frequent gusts to
30 knots and a few gusts to 35 knots possible across the outer
Stayed close to the local wave guidance showing seas topping
out at 4-5 ft on Tuesday w/highest seas across the outer zones.
SHORT TERM: A SCA may be needed early Tuesday night for winds
gusting up to 25 kt. NW winds may again approach SCA on Thu.
Otherwise, winds should be below SCA most of the coming week.
MARINE...Small Craft Advisory until 4 PM EST Tuesday for ANZ050>052.
AREA FORECAST DISCUSSION
National Weather Service Wilmington OH
946 PM EST Mon Dec 23 2019
A weak cold front will drop south into the upper and middle Ohio
Valley tonight. The front will stall on Tuesday before lifting
northeast as a warm front by Tuesday night. A mid level ridge
will then continue the warm temperatures into Christmas Day.
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
The forecast is complicated tonight in terms of the potential
for fog and/or low stratus development.
Skies are currently clear across our region. A weak cold front
is forecast to move south into our northern forecast area
overnight, laying out northwest to southeast. Although there
will continue to be some high level clouds spilling into the
region from the northwest, models continue to suggest the
potential for fog and/or low stratus. In fact, model soundings
suggest that the fog and/or low stratus would be confined to the
first couple hundred feet of the surface. Will continue with
the development of areas of fog tonight over the northern two-
thirds forecast area. For points along and south of the Ohio
River, fog should be more confined to the river valleys. The HWO
has already been updated to reflect this current thinking.
As has been the case the last few nights, forecasting low
temperatures continues to be tough. Believe most lows will
range from the upper 20s to the lower 30s, but some values
slightly below or slightly above this range may occur as well.
.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
Areas of fog will gradually lift during the morning hours, with
skies becoming mostly sunny to partly cloudy by afternoon.
Aforementioned weak boundary will have stall across our area on
Tuesday. It will be a little cooler across the north with still
warm readings across the south. Highs will range from the upper
40s north to the lower 60s south.
For Tuesday night, a mid level ridge will build into the Ohio
Valley. This will push the weak front to the northeast as a warm
front. Some high clouds are expected at this time. Overnight
lows will range from near 30 in the far east to mid 30s
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Period starts Christmas day with anomalous 500 mb heights over 5700
meters associated with a broad upper ridge. This pattern will
provide dry weather through Wednesday as surface high pressure moves
east. A weak front swinging south from Great Lakes low pressure on
Thursday is likely to suffer from a lack of upper support and deep
moisture under the persistent ridge aloft, allowing dry conditions
to continue. Even as heights aloft decrease slightly in response to
trough activity in Southern Canada, the return of surface high
pressure will probably result in dry weather on Friday as well.
Signs of change come Saturday ahead of low pressure developing to
the southwest. Rain will be possible by Saturday evening near a
front extending ahead of the low. Rain will become likely Saturday
night and Sunday morning, with rain chances continuing through
Monday as the slow moving low moves to the Mississippi River. Rain
chances will generally be greater in southern locations closer to
the main body of moisture and forcing, while snow may mix in
northern locations on Monday where colder temperatures will be
Well above normal temperatures will be evident under the slow to
evolve pattern. Highs Wednesday and Thursday are expected to be in
the mid and upper 50s. Readings are forecast to retreat a few
degrees Friday through Sunday under increasing clouds and precip,
with highs ranging from the upper 40s to mid 50s. Cold advection may
result in highs falling to the 40s Monday, still above normal.
.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
Complicated forecast tonight in terms of fog and/or low stratus
Latest RAP and GLAMP guidance continues to suggest that fog
and/or very low stratus will develop along and behind a weak
cold front that is poised to drop south into the northern parts
of the region tonight. As such have added fog to the northern
terminals as visibilities may lower to 1 mile or less with
ceilings around 200 feet. There could even be some patchy dense
fog. Elsewhere, have limited the fog potential to the river
valleys (along and south of the Ohio River). Thus, all
terminals, except for KCVG, have IFR/LIFR conditions forecast
late tonight. Again, there is the potential for some patchy
On Tuesday, aforementioned weak front will stall across the
region. Fog and/or low stratus will slowly lift through the
morning hours due to heating. We should return to VFR conditions
between 16Z and 18Z.
OUTLOOK...MVFR/IFR ceilings and MVFR visibilities possible
Wednesday night into Thursday night. MVFR ceilings and
visibilities possible on Saturday.
Area Forecast Discussion
National Weather Service Indianapolis IN
937 PM EST Mon Dec 23 2019
The AVIATION Section has been updated below.
Issued at 148 PM EST Mon Dec 23 2019
Dry and Mild weather is expected for much of this Holiday week
ahead. High pressure over Missouri and Indiana is expected to
continue to maintain its influence over Indiana through the end
of the work week as it slowly moves to the east coast.
The next best chance for rain will be Saturday and Sunday as a
Frontal system is expected to arrive in the region.
.NEAR TERM /Tonight/...
Issued at 148 PM EST Mon Dec 23 2019
Surface analysis early this afternoon shows high pressure in place
from Ohio...across Indiana to Missouri and Oklahoma. Low pressure
and cyclonic flow was found across the southeastern states.
GOES16 shows clear skies across Indiana along with a diminishing
snowpack along the I-70 corridor. Temps were rising through the
upper 50s and dewpoints were climbing through the 30s.
Aloft...water vapor showed strong ridging in place across the
plains states with lee side subsidence across Indiana. Plentiful
tropical moisture was streaming aloft across the western United
Models remain in good agreement tonight keeping strong high
pressure aloft as the ridge axis aloft is expected to advect
eastward across Indiana. Forecast soundings and Time heights again
show a dry column with subsidence. Thus mostly clear skies will be
be expected. RAP and NAM show dewpoint depressions falling to 1C
or less overnight...thus some patchy fog cannot be ruled out late
tonight and early Tuesday. Will stick close to the blends on
.SHORT TERM /Tuesday through Thursday/...
Issued at 148 PM EST Mon Dec 23 2019
Models through Thursday continue to show the strong ridge axis
aloft slowly making a progression toward the east coast On
Thursday. This results in strong High pressure settling across the
east coast for much of the middle part of the week. As for
Indiana...warm southwest flow develops develops on the backside of
the high. This has a two fold effect...first pumping warm air into
the ohio valley...but also steering any weather making systems
well north of Indiana into the upper midwest and western Great
Lakes. Forecast soundings across the forecast area through
Thursday remain dry with ongoing subsidence.Time heights also show
a very dry column with subsidence. Thus will trend toward mostly
sunny days and mostly clear nights through Thursday. Given the
warm SW flow will trend temps at or above the NBM.
Bad sledding weather on Christmas eve as warm temps should
eliminate snow cover across the area by then.
.LONG TERM /Thursday night through Monday/...
Issued at 315 PM EST Mon Dec 23 2019
Upper ridging will keep dry conditions and above normal
temperatures in the forecast through Friday night. On Saturday,
though, the upper ridge axis moves off to the east and a
southwesterly flow pattern sets up over central Indiana. This will
allow shortwaves to move through the upper flow bringing rain
chances across the area Saturday through Monday, along with a
surface frontal system. Timing/location and strength of the upper
low vary greatly in the different ensemble solutions and thus will
keep the high chance PoPs from the NBM for Saturday and even some
likelies for the southern half or so for Saturday night as this is
the most consistent timing/placement for rain showing up in the
different ensemble members. Could see a decent drop in
temperatures near the end of the long term, but this keeps being
advertised around day 7 and continues getting pushed back so still
low confidence on any cold air making its way here in the next
seven days. Should this come to fruition, though, there may be a
mix of rain and snow possible come late Sunday night/Monday
.AVIATION /Updated for 240300z IND TAF Issuance/...
Issued at 935 PM EST Mon Dec 23 2019
No changes made to previous forecast. High pressure will allow
winds to remain calm or light and variable overnight. Sfc temps
already below cross over temps and with increased Tds expect fog
to develop overnight.
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Morristown TN
1040 PM EST Mon Dec 23 2019
No changes are needed to the forecast this evening. High clouds
are clearing out, and with this clearing will come a potential for
fog development, if winds can drop to calm. This may happen in
some spots so patchy fog should cover it well.
00Z TAF DISCUSSION.
Mid to high level clouds currently over the area are expected to
gradually scatter and clear out overnight. This should allow for
some cooling that may lead to some fog development in some areas.
The question regarding fog density will be how much winds drop off
to calm. The TAFs will have MVFR vis at TRI and TYS early in the
morning, but no fog at CHA where wind is more likely to stay above
calm. The rest of the day will be VFR.
/ISSUED 249 PM EST Mon Dec 23 2019/
SHORT TERM (Tonight and Tomorrow)...
Current water vapor imagery and RAP upper air analysis indicate a
closed low centered near the Florida Panhandle with moisture
advecting northwards across the Carolinas. At the surface, low
pressure is centered just off the Georgia coast with high pressure
across the Mid-Atlantic. Diminishing radar returns have featured
throughout the morning into the early afternoon, Due to this,
decreased PoPs some in the near-term with the majority of the area
currently dry. Low-level cloud cover is decreasing across the area
but still seeing plenty of high-clouds with mid to upper level
moisture wrapping around the upper low. These high clouds will
continue to diminish this evening into the overnight as the upper
low continues to track to the east.
The overall pattern features a broad ridge across the eastern 2/3rd;s
of the country and there will be no cold air advection as the upper
low departs to the east. Model soundings indicate that low-level
moisture will remain elevated tonight with skies clearing and light
winds. Therefore, patchy fog will be possible across the area. Lows
tonight will remain mild in the low to mid 40s for most locations.
Upper level heights will increase tomorrow into the 576-580 dm range
as the low shifts eastward. PW values will drop down into the 0.3-
0.5 inch range. These values are in the 25th-50th percentile for
late December. Overall, model soundings support mostly sunny skies
with temperatures warming into the low to mid 60s for most locations.
LONG TERM (Tuesday Night through Monday)...
We begin with a very strong ridge bringing warm and humid conditions
for Christmas Eve night and Christmas Day. This warmth will continue
all the way through the upcoming weekend, with high temps in the 60s
from Christmas Day through the weekend, and daily average temps
running 15 degrees above normal.
Models still differ on the departure of the ridge. The Canadian and
ECMWF are in agreement on a slower progression of a closed H5 low
over the southern Rockies this weekend, while the GFS now opens the
low and lifts it into the north plains. The slow approach means that
rain chances for Saturday are now mostly in the slight chance range,
with much better chances Sunday among all three models. Chance of
precip will continue on Monday. On Monday, the ECMWF brings the
closed low through the southeastern states similar to today`s
feature, while the GFS has us in the tail end of northwesterly
upslope pops as its H5 low moves through New York. No matter which
of those two solutions, both end precip here during Tuesday. As the
H5 trough/low make it near our area Monday, temperatures will
finally cool off, with highs down into the 50s.
Area Forecast Discussion
National Weather Service Pocatello ID
240 PM MST Mon Dec 23 2019
.SHORT TERM...Today through Wednesday or Christmas night...The
models have continued to show a chance of light to moderate
moisture tonight through tomorrow, Christmas Eve. The first surge
of moisture will be tonight in southerly flow. This will lend to
upslope flow over the southern Central mountains, Lost River
Range, and Arco desert where 2 to 4 inches in valleys with 4 to 6
inches (with locally higher amounts) in the mountains. A special
weather statement is in place for these areas. For the
Beaverhead/Lemhi Highlands and the Centennial/Island Park areas
look for higher amounts, around 3 to 6 inches for valleys and 6
to 10 inches for mountain areas. A winter weather advisory is in
place for these two zones/areas. For the Eastern Magic Valley and
the Snake river plain, there is low confidence in the forecast.
Currently we are expecting a trace of snow up to 1/2 inch for
these areas, primarily tonight into early morning. There is a
slight chance some of these area may get freezing rain but model
forecasts show this as a very low probability. The southern/eastern
portions of the Snake River plain and Eastern Magic valley are
expected to quickly warm up with southerly downslope winds
turning any precipitation into rain or a rain snow mix by early to
mid tomorrow morning.
The precipitation shifts more to our southern and eastern areas
by late morning into the afternoon on Christmas eve. Snow levels
will rise to around 5000 feet in the afternoon, particularly for
our southern, southeast and eastern areas. Also, along the I-86
corridor expect downslope winds to continue, which will favor
precipitation falling as rain or, at least, a rain/snow mix.
Expect 1 to 4 inches of snow for the Southern Highlands and
Southeast Highlands from late morning through early evening on
Christmas Eve. Temperatures will be 4 to 8 degrees above normal
with the overall southerly flow on Christmas Eve.
For Christmas Eve night and Christmas Day, precipitation will
be mainly along the Montana Divide/Wyoming/Utah borders, in
general, along/east of I-15. Expect all snow as colder air
arrives. Additional snowfall in these areas will be around a trace
to up to 2 inches for mountain areas. Expect near normal to
slightly below normal temperatures on Christmas day. Wyatt
.LONG TERM...Thu through next Mon night. ECMWF and GFS are in
very good agreement about this being a dry period. Once the storm in
the near term passes to the east, there is a period on Fri with
northwesterly flow that the eastern highlands and southern highlands
could get some light upslope precipitation. The other thing this
airflow will do is bring in bitter cold Canadian air, so once skies
clear Thu, expect single digit overnight lows for even the Snake
River plain, and stagnant air by Sun as high pressure arrives
directly overhead. This will lead to fog and stratus issues, and
potentially air quality issues. While the northwest flow may be
breezy on Thu/Fri in portions of the forecast area, it should
quickly calm down. Giant low off the southern CA coast will be
keeping all Pacific moisture in the southern tier.
.AVIATION...Bands of precipitation are already moving through south
central Idaho and also some development in the northeast corner.
This forecast is difficult because the region is in the warm sector
of the current storm and will be flirting with the temperatures
rising at night and hanging right around freezing. If it stays
below, as some MOS guidance believes, then KPIH and KIDA will be in
SN ; if above, it maybe only RA. This will make a huge difference in
VSBY and CIG. Southerly flow should also put KPIH and KBYI in a
precipiation shadow, and may have better CIG and VSBY than forecast.
However, HRRR guidance indicates that surface wind will be in
opposition to the upper level southerly flow, from the northeast.
KSUN and KDIJ will likely stay with SN and will likely be closed at
times Tue morning.
Winter Weather Advisory from 2 AM to 5 PM MST Tuesday for IDZ066-