Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/13/21
Area Forecast Discussion
National Weather Service Denver/Boulder CO
822 PM MST Fri Mar 12 2021
.UPDATE...
Issued at 821 PM MST Fri Mar 12 2021
Satellite pictures are showing Stratus covering most of the CWA up
to the continental divide. Observations and web cameras are
showing fairly dense fog over about the eastern half of the CWA.
There is little to precipitation falling at this time.
I will lower the pops for the rest of this evening based of
reality. Will add fog to the eastern half of the plains as well.
Will leave highlights going as is with this update.
&&
.SHORT TERM...(This evening through Saturday)
Issued at 350 PM MST Fri Mar 12 2021
Tonight, the closed upper low over southern NV is expected to
shift slowly eastward along the central UT/AZ border by 12z
Saturday. A strong southerly flow aloft will be over CO with a
120+ kt upper jet rounding the base of the trough and spreading
northward across Colorado. It looks like the forecast area will be
under the left exit region of the jet by 12z Saturday, with
increasing QG ascent in the mid and upper levels. In the
mountains, light precipitation the form of freezing drizzle and
light snow will transition over the moderate to heavy snow late
tonight and Saturday. Across the northeast plains, no change this
evening with a persistent east-southeasterly winds keeping a deck
of low clouds in place. Drier air above 700 mb will continue
until around 09z, with the moisture increasing aloft as a deeper
east-southeasterly flow develops in the mid and upper levels.
Overall expected areas of drizzle, freezing drizzle and fog until
late tonight for the urban corridor and northeast plains, then a
transition to light snow Saturday morning.
On Saturday, ECMWF has the closed upper low over southwestern CO by
00z Sunday. A moderate to strong qg ascent will be over north-
central and northeast CO on Saturday with the low level winds
transitioning from southeast in the morning to east-northeast in the
afternoon. Main concern involves the amount of snow generated by
the models over the northeast plains, east of a line from around
Fort Morgan to Limon. The HRRR spreads a convective area of showers
with some embedded thunderstorm potential over southeastern CO at
14z then lifts it north/northwestward into the northeast plains and
urban corridor by 18z. There may be a brief break from the heavier
showers after 21z if a dry slot develops behind this first wave.
We upgraded the Winter Storm Watch for zones 42, 44 and 45, to a
Winter Storm Warnings, but go with Winter Weather Advisories for
zones 46, 48 and 49. Some other advisories were added in the high
valleys as well the the Gore/Park Range. As the easterly upslope
deepens through the afternoon, snowfall in and adjacent to the
Front Range will increase as well.
.LONG TERM...(Saturday night through Friday)
Issued at 350 PM MST Fri Mar 12 2021
...POWERFUL WINTER STORM WILL CONTINUE TO IMPACT THE AREA THROUGH
SUNDAY...
Despite some of the wild gyrations we`ve seen in model guidance,
the overall plan with this storm is still the same. In fact, the
latest EC and GEM ensemble data suggest about the same evolution,
if not slightly higher totals, than previous runs. The EC ensemble
average is now up slightly to about 1.8" liquid equivalent for
Denver, the GEM remains at ~2.4", while the GEFS was down to about
1.8", following the lead of the wildly erratic GFS. The bottom
line is that the value of the ensemble data is huge in this storm,
and we`ll be keeping the forecast relatively unchanged at this
point and favoring the EC ensemble blend.
This storm has everything going for it, including infusion of rich
Gulf of Mexico moisture, a pronounced TROWAL, a persistent period
of moderate to strong QG lift, long duration, and strong upslope
as long as the 500 mb low tracks across east central/southeast
Colorado. So far, most model averages (not the 12Z NAM and GFS) are
still sticking with the upper low tracking from near the Four
Corners into southeast Colorado, putting northeast Colorado in a
very favorable area for strong lift, upslope, and heavy snowfall.
We`ve overall kept the forecast relatively unchanged for this
event with 14 to 24 inches for the I-25 Urban Corridor, with
locally heavier amounts possible toward Boulder and Golden
depending on exact track and evolution of the storm, of course.
Foothills should see 2 to 4 foot totals with the heaviest favoring
Larimer County. Again, any slight change in track could result in
much higher/lower amounts. The 10-90% snowfall graphics represent
this uncertainty well, with bottom end (10th percentile) 10"
amounts along the I-25 Corridor but the 90th percentile showing
amounts near 30". Foothills areas go as high as several feet in
the 90th percentile, or worst case scenario!
If the storm does end up moving farther north, perhaps related to
the massive warm air advection and latent heat release, then we
would see a dry slot working northward across our forecast area
Saturday night into Sunday. That would result in much less
snowfall, but the confidence of this happening is quite low at
this time and mainly only observed in the NAM and 12Z operational
GFS. Just for fun and for stark contrast, the 18Z GFS is right
back to the older and almost runaway solution of a historic
snowstorm for at least the northern portions of the Front Range.
That`s exactly why we won`t get caught up in any individual model
runs at this point, and haven`t for the past several days.
Whatever the case, almost all of northeast and north central
Colorado should be prepared for a major winter storm. Travel may
become impossible due to the depth of accumulating snow across the
foothills and I-25 Corridor. Scattered power outages will be
possible as well.
The far eastern plains (roughly along/east of Sterling to Fort
Morgan to Limon line) may certainly see enough warm advection for
a mix of rain and snow, and mostly rain out near Julesburg. We`ve
made appropriate highlight changes to those areas, dropping the
Winter Storm Watch altogether of the far northeast corner.
Advisories border that to the west, with Warnings continuing for
the rest of the plains and Front Range. With sufficient dynamics
and possible northerly flow and not as strong of downslope later
in the event, we`ve added the high mountain valleys and non-Front
Range mountains to an Advisory as well. Winds on the plains do not
look strong enough for blizzard conditions, but areas of blowing
snow still expected Sunday as winds increase to gusts 30-35 mph in
most areas.
This storm should slowly wind down Sunday night with decreasing
snow. Some light snow may linger across the plains into Monday.
Then another short wave drops southeast into the Central Rockies
and exhibits the Fujiwhara effect, actually rotating around the
other. This second one should be able to produce additional
snowfall. Temperatures should return closer to normal with drier
conditions by the latter half of next week.
&&
.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 821 PM MST Fri Mar 12 2021
Southeasterly low level winds have been in place at DIA since 00Z.
Models keep these going much of the night. They are progged to
become more easterly by 12Z. They continue easterly until about
18Z, then become more northerly. As far as ceilings go, BKN-
OVC040-050, then BKN-OVC015-030 after 07Z. By 12Z ceiling should
be under OVC010 and continue that way for much of the weekend.
Will hold off on the hydro and photometers until around 12Z. Will
go with 1SM -SN BR from about 11Z onward. The moderate to heavy
snow will likely not get going until mid/late Saturday afternoon.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 5 AM MST Saturday to 1 AM MDT
Monday for COZ030>032-037.
Winter Storm Warning from midnight MST tonight to 6 AM MDT
Monday for COZ033>036.
Winter Storm Warning from 5 AM MST Saturday to 6 AM MDT Monday
for COZ038>045.
Winter Weather Advisory from midnight MST tonight to 6 AM MDT
Monday for COZ046-048-049.
&&
$$
UPDATE.......RJK
SHORT TERM...Cooper
LONG TERM....Barjenbruch
AVIATION.....RJK
Area Forecast Discussion
National Weather Service Caribou ME
915 PM EST Fri Mar 12 2021
.SYNOPSIS...
An Arctic cold front will cross the area overnight with high
pressure ridging across the region on Saturday. Upper level
disturbances are expected to move across the region Sunday into
Monday, followed by high pressure on Tuesday which moves east of
the area Wednesday.
&&
.NEAR TERM /THROUGH SATURDAY/...
9:15 PM Update: Cooler air is filtering into the area this
evening. Certainly not colder, as Frenchville is still 32F at 9 PM,
which is above the average high for this time of year. A much
stronger push of modified arctic air will sweep across the FA
overnight. The front looks to be accompanied by scattered snow
showers, especially from the Central Highlands and across parts
of the Downeast Region including possibly Bangor. Based on
upstream radars which show the snow showers from northern NY
State and into southwest Maine have issued a heads up special
weather statement for late this evening and overnight across
several of our southern zones. The front will likely be
accompanied by a rapid intensification of the wind, which at
least for now has become quite light across our southern zones,
and has diminished significantly in the north. Wind gusts to 40
mph will be possible behind this front later tonight and into
Saturday. Made some modifications to the forecasts elements for
the remainder of the night based on the current and expected
conditions.
Previous discussion:
WNW winds will gradually drop off this evening as some weak
ridging moves in, but this will be short lived as a cold front
moves into the region from Quebec. This front will be bringing
increasing clouds along w/some CAA. Some snow showers are
expected to set up this evening and push across the region. The
NAM and RAP point to some intense activity setting up across the
Maine Central Highlands and Downeast region later in the evening
through early Saturday morning. The activity then pushes off
the coast by daybreak. The SNSQ Parameter indicates some high
numbers across these areas as does the sounding data showing
CAPE of 40+ joules and steep low/mid level lapse rates. This
would point to snow squall potential. Given this, decided to
increase the pops across the aforementioned areas and carried
the potential down to the coast. At the start, temps will be
warm enough for rain showers, but w/the CAA arriving, rain will
go over to snow w/the potential for a quick inch of accumulation
and possible slippery conditions. There will be an area moving
across far northern areas(toward the northern border), but not
as intense as the activity to the s. Winds will also increase
w/the CAA hitting and the pres gradient tightening. Will address
the snow squall potential in the Hazardous Weather Outlook.
For Saturday, any leftover snow showers will be exiting by
morning w/some partial clearing into the early afternoon. Clouds
will set back up again by the afternoon w/another Arctic front
apchg from the w. Stayed close to the midnight crews assessment
of bringing the mention of snow showers into wrn areas by later
in the afternoon. It will be quite breezy as winds increase to
15-25 mph w/some higher gusts. NW winds early in the day could
allow for some streamers coming off the St. Lawrence w/the
strong temperature differential noted by the NAM and GFS. The
ECMWF hinted at this as well. Daytime temps will be below
normal.
&&
.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY/...
Snow squalls and wind chill a factor Sunday and Monday. Not
something immediately considered after a couple days of temps
well above normal.
An arctic front will pass over the area Sunday afternoon,
bringing with it more gusty winds and the likelihood of snow
squalls to much of the northern and eastern Maine I-95 corridor.
Temperatures on Sun look to peak during the morning/noon hours,
rising just above freezing across the Bangor Region, Downeast,
and Penobscot Valley, before beginning a downswing in the
afternoon as cold air advects into the region.
The cold air layer is deep, allowing excellent mixing in the
lower levels. This will allow frequent gusts up to 30 mph
through the afternoon. Lapse rates here continue to impress w/
8-10 c/km through the low levels. Given the moisture profile,
snow squalls become a concern for Sunday afternoon and evening.
Not only will the added convergence and instability create the
chance for these heavier snow showers to cause rapid changes in
visibility, roadways may be damp/warm from recent abv zero
temps. Snow falling on top and refreezing may create patchy
slick spots on the roadways. If a strong, consistent band of
showers forms, up to an inch or two of accumulation will be
possible.
Current hires convective models that reach into this period
highlight two notable zones for squall potential; one from the
North Woods through Millinocket and into Interior Downeast, the
other across the northern Aroostook cities. Both are higher
travel areas of eastern Maine, harboring I95 and Rt 1. That
said, squalls tend to be scattered in nature, and the breadth of
the passing front will keep the populated area of the Bangor
Region mentioned as well. More confidence will come with
consistency in these patterns.
Moisture dwindles into the late evening and overnight hours, but
the well mixed lower levels remain. The area will likely remain
gusty overnight through Monday as well, potentially causing a
blowing snow concern with any freshly fallen snow from the
showers. High pres passing south of the region will allow the
crashing temperatures Sunday to continue Sunday night, falling
below zero across the north and single digits to the south. With
the persistent winds, wind chills in the north could reach
advisory criteria (-20F) during Mon morning, and remaining below
zero for a bulk of the afternoon.
&&
.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Pressure gradient over Maine will begin to slacken into Tuesday
as high pres exits the New England coast. Temperatures rebound
slightly, towards normal. The day begins sunny, becoming cloudy
in the afternoon. Low pres makes a run off the Mid-Atlantic
overnight, tracking NE. The ECMWF and GEM have kept this system
off the Maine coast, but GFS and GEFS has a bit of QPF reaching
Downeast and the coast in the afternoon. Kept chances low at
this point given this discrepancy. The next system later in the
week holds more potential for ME impacts.
This system for the Thurs Night/Fri time frame brings a low
across the Ohio Valley, toeing the Michigan and IN/OH border,
through PA, and off into the east coast waters. It then makes a
drive up NE near the Gulf of Maine. EPS members keep many
options on the table, as does the GEFS. While the track above
seems to be favored by deterministic modes, there remains the
possibility the parent low is pulled north into Quebec for an
overrunning event as coastal redevelopment takes place. Main
takeaway is the potential for a system later next week, but
details concerning precip types will be improved on as
confidence increases. Overall, temperatures do take a warmer
turn through mid-week.
&&
.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
NEAR TERM: VFR late this evening through Saturday with possible
brief IFR late tonight in any snow showers, especially at KBGR
and possibly KBHB. A strong west wind has diminished late this
evening, but will pick up again late tonight to 15 to 25 knots
with gusts to 35 knots possible.
SHORT TERM:
Sat night-VFR, becoming MVFR at FVE, CAR, PQI, HUL, after
midnight with -SHSN. West winds.
Sunday MVFR. Gusty NW winds, up to 30 kt towards BHB/BGR. IFR
vis possible in SHSN through the afternoon.
Sunday Night MVFR early, becoming VFR. Gusty NW winds continue.
Mon-Tue...VFR. NW 5-15kts and gusty Mon becoming WSW 5kts Tue.
Wed...VFR, light SW winds. -RA/-SN possible at BGR/BHB.
&&
.MARINE...
NEAR TERM: A gale Warning remains in place for overnight into
Sat.
SW winds 15 kt will become W late this evening and then NW by
early Sat morning, and increase to 15-20 kts w/gusts to 25 kt.
The winds are expected to increase further after midnight to
25-35 kt w/gust to 40 kt by daybreak. Seas 4-5 ft this evening
will subside through tonight.
Sat...Seas will kick back up again reaching heights of 5-6 ft.
NW winds 25 to 35 kt w/gusts to 40 kt.
SHORT TERM:
SCA winds increasing towards Gale, up to 40 kt, Sunday
afternoon through Monday for the coastal waters. Winds slacken
to SCA Monday night, and below 25 kt Tuesday morning. Conditions
subside below SCA levels Tuesday.
Wave heights will also be elevated through this period, peaking
3 to 7 ft on the coastal waters Monday, falling to 2 to 3 ft by
Tues morning.
&&
.HYDROLOGY...
Ice movement and some river/stream rises did occur across the
region, especially along the Piscataquis and Penobscot River
basins Friday. No flooding issues were reported. There looks to
be a slowing of the movement looking at the latest trends of
the gages. Further cooling will slow things up into the weekend.
&&
.CAR WATCHES/WARNINGS/ADVISORIES...
ME...None.
MARINE...Gale Warning from 3 AM to 1 PM EST Saturday for ANZ050>052.
&&
$$
Near Term...CB/Hewitt
Short Term...Cornwell
Long Term...Cornwell
Aviation...CB/Hewitt/Cornwell
Marine...CB/Hewitt/Cornwell
Hydrology...Hewitt
Area Forecast Discussion
National Weather Service Gray ME
1005 PM EST Fri Mar 12 2021
.SYNOPSIS...
Much colder air will enter the region tonight as high pressure
builds towards New England from the Midwest. This system will
continue to build east Saturday and Saturday night with
temperatures remaining well below normal for this time of the
year. Another strong cold front will cross our region late
Saturday night and Sunday morning, bringing more cold air into
the region and the possibility of snow showers. Cold, Canadian
high pressure will then build into New England on Monday and
Tuesday of next week. Low pressure will then exit the Central
Plains during the midweek period before bringing a mix of rain
and snow to the Northeast late in the week.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
10 PM Update...Just a few minor adjustments to PoPs and winds
based on latest observational data as well as the last couple of
runs of the HRRR which seems to be handling the rain/snow
showers and squalls quite well. The most intense snow showers
and squalls may very well occur between 05z and 08z as a vort
max centered near Drummondville, Quebec (clearly visible on
Canadian radar) drops south into the mountains. Snow accums
during the period may be as much as 3" in some spots in our
mountainous zones. The HRRR seems to be handling this fairly
well this evening. Not quite sure how far south the heavier
precip will make it but it`s not out the question that portions
of central and southern ME will catch some of the activity while
it`s weakening late tonight.
As far as the wind advisory goes, have shortened the end time
to 15z Saturday morning as soundings and other sources of data
do not support advisory criteria gusts of 40 kt past that point.
Previously...
630 PM Update...Little change to the going forecast at this
time. Gusts are starting to pick up at this time as cold front
approaches. Also seeing some snow showers in the Whites via
webcam, with a few rain showers on the valley floors.
Showery/squally weather is expected to continue this evening in
the the mountains with perhaps a couple making it to the
foothills and farther east. Not thinking there will be any
impact at lower elevations as it`s still very warm.
Previously...
This afternoon, visible satellite shows sunny skies across the
region with temperatures in the upper-40s (mountains) to around
60 (southern New Hampshire). These pleasant, spring-like
conditions come to an end for the time being later this evening
as a cold front crosses with Arctic origins. The most
significant impact with this cold fropa will be strong, gusty
winds as lapse rates steepen and the PGF tightens with the
passing wave. Wind gusts 40-45 mph will be common for central
and southern New Hampshire into southwest Maine, aided by
downsloping off the White and Western Maine Mountains. As the
temperature inversion above the mixed layer lowers... around
and just after midnight or so, in the wake of the cold front...
winds will peak; although isolated, I do expect some wind gusts
to approach 60 mph in the immediate downsloping regions of the
mountains but without coverage to upgrade to a warning. Instead,
opted to pull back the start time of the extant wind advisory
to 01Z to better time the product with the frontal passage.
A secondary impact will be snow shower and even some snow
squall activity with the front. Snow squall parameter continues
to indicate a strong possibility of snow squalls over the
mountains later this evening... and Froude suggests a few of
these may stream out of the mountains and impact the foothills
into the Mid-Coast region later on, around midnight or so. While
temperatures will still take time to lower overnight, squalls
would be intense enough to fall as snow and cause at least
visibility issues. Don`t think there would be the intensity or
longevity to produce significant travel impacts outside of the
mountains thanks to warm temperatures and pavement today.
Speaking of temperatures... lows tonight bottom out in the teens
north to the 20s elsewhere. Upslope snow showers over the
mountains taper off by dawn as low-level ridging works in.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
Although the day starts fairly windy, the PGF gradually relaxes
Saturday through Saturday night as Canadian maritime low
pressure pulls away to the northeast. Thus wind gusts early in
the day will eventually taper down to 20 kts or so by the end of
the day (as the environment will remain well-mixed)... and turn
to a light westerly to northwesterly breeze overnight. Clearing
skies and offshore winds will allow temperatures to rise to
around 30 across the north to the mid-40s over the south and
coastal plain, which is around normal and much cooler than what
we`ve experienced these past couple days. Given the mixing
conditions, leaned on raw model output for temperatures
overnight with lows in the teens (north) to the mid-20s over the
south and coastal plain.
&&
.LONG TERM /SUNDAY THROUGH FRIDAY/...
Another shot of Arctic air will enter the region Sunday
afternoon with the passage of a strong frontal system. Snow
showers will develop over the favorable upslope regions of the
northern mountains. Enough instability and the presence of an
approaching upper level trough will allow for a few possible
squalls across the north. Some of this precipitation may make it
to the coastline later in the day.
Winds will increase during the day as mixing level become very
deep, in the 7,000 to 9,000 foot range. The northwesterly
gradient will continue to be strong Monday night as the upper
level trough exits to our east. Windy conditions combined with
air temperatures below zero in the north to the single numbers
in the south will allow for wind chill values below zero in all
sections by morning.
Windy and cold conditions will continue on Monday. Temperatures
will be well below normal for this time of the year with mostly
teens and 20s for daytime highs which is below NBM guidance.
Relatively quiet conditions are expected during the midweek
period with moderating temperatures and no precipitation. Some
of the guidance suggests a weak upper level trough will approach
the region Tuesday night into Wednesday morning along with some
broadly diffuse warm air advection. However, this trough may
become sheared as it approaches New England.
Models remain in relatively good agreement with a system
approaching the Northeast late in the week. European model
ensembles suggest this system will be forced through the Gulf of
Maine as cold air begins to settle southwards and into our
region. This system does begin to shear out with time as it
crosses the region. In any case, went above NBM pops late in
the week and model consensus gradually improved with time.
&&
.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
Short Term...Gusty winds remain the primary aviation impact
with westerly gusts around 25 kts this afternoon escalating to
as high as 35-40 kts for most terminals overnight as a cold
front crosses and winds back toward the northwest. No LLWS is
expected due to sustained winds at the surface. Winds continue
to gust out of the northwest tomorrow, gradually tapering
through the day from around 30 kts early to around 20 kts later
before diminishing to a light breeze Saturday night. A period of
MVFR ceilings is likely late tonight with -SHSN at KHIE before
lifting back to VFR during the day Saturday.
Long Term...Winds increase once again Sunday night into Monday
with more scattered snow showers, primarily in the north. Mainly
VFR conditions outside the mountains. VFR conditions continue
for much of the week before low pressure brings a mix of rain
and snow to the region late in the week.
&&
.MARINE...
Short Term...A strong cold front blasts through the waters
tonight with a period of gale force winds to around 40-45 kts.
Winds will gradually diminish on Saturday to SCA levels.
Long Term...Moderate to strong west to northwest winds expected
through the first part of next week as high pressure to our
west keeps a flow of cold air out of Canada into New England.
Winds likely increase back into the gale range on Sunday into
Monday as the next round of colder air moves in. With
temperatures taking a tumble there`s actually a likelihood of
freezing spray Sunday night into Monday and this may warrant an
advisory. Winds diminish Monday night into Tuesday as high
pressure moves by. Winds increase late in the week with as low
pressure approaches New England.
&&
.CLIMATE...
Colder air will move into the region tonight. By early next
week we could challenge record low temperatures. The coldest
temperatures are will likely settle over the region Tuesday
morning. Here`s a look at the record lows for that day.
Tuesday, March 16, 2021
REC LOW PROB OF BREAKING
PORTLAND 5 in 1956 Low chance of breaking record
CONCORD 0 in 1869 Low chance of breaking record
AUGUSTA 4 in 1956 Low chance of breaking record
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Wind Advisory until 10 AM EST Saturday for MEZ012-013-018>020-
023>025-033.
NH...Wind Advisory until 10 AM EST Saturday for NHZ004-006-008>010-
012>015.
MARINE...Gale Warning until 2 PM EST Saturday for ANZ150>154.
&&
$$
NEAR TERM...Ekster
SHORT TERM...Casey
LONG TERM...Cannon
Area Forecast Discussion
National Weather Service Lincoln IL
712 PM CST Fri Mar 12 2021
.SYNOPSIS...
Issued at 712 PM CST Fri Mar 12 2021
Periods of light rain are possible tonight through early Saturday
morning southwest of a Jacksonville to Terre Haute line. Calm
weather is expected Saturday ahead of another longer period of
rain to end the weekend.
&&
.UPDATE...
Issued at 712 PM CST Fri Mar 12 2021
Evening sounding from our office shows a significant amount of dry
air below 10,000 feet, and this is apparent in the lesser amounts
of rain being reported at the surface. Even areas that are getting
rain in south central Illinois have ceilings around 10,000 feet,
so amounts are light thus far. Most recent high-res model runs
keep much of the rain south of our forecast area, though the RAP
and 3km NAM get some decent coverage into our area south of I-70
this evening. PoP`s have been updated to trim the rain chances
along the northern edges, now mainly focused on the area from
about Jacksonville to Terre Haute southward. Temperatures are
generally on track and did not require much change.
&&
.SHORT TERM...(This evening through Saturday)
ISSUED AT 318 PM CST Fri Mar 12 2021
Precip across MO will spread into parts of central and southeast
IL tonight but should remain south of a Canton to Paris line
through the period. This precip will not last long and slide
south during the late night and early morning hours of Saturday.
Then dry weather is expected during the day, Saturday. Temps will
again be on the cooler side tonight with mid 50s expected again
tomorrow.
&&
.LONG TERM...(Saturday night through Friday)
ISSUED AT 318 PM CST Fri Mar 12 2021
Precip associated with the big system coming out of the southwest
US will slowly move into the area late Saturday night.
Unfortunately there will be a lot of dry air to overcome across
the state. Most of the precip will really begin on Sunday but a
couple of the models do have some light precip for late Sat night
southwest of I-74. Precip will become likely during the day Sunday
and then definite rain expected on Sun night. The system is
somewhat progressive with the precip shield but rain will remain
over the area Sun night through Monday. Monday evening precip
diminishes to chances across the area, then decreases down to
slight chance for late Monday night. Across the northern parts of
the CWA, where the colder air aloft begins to move into the area,
some of the precip will be a mix of rain and snow. However, we
could lose ice crystals in the area as well, so light sleet and/or
light freezing rain has also been added to the grids. This system
could also produce some rumbles of thunder Monday afternoon and
Monday evening so added slight chance of thunderstorms in the
forecast for that time period.
After a dry period from Tue into Tue night, another weather system
will move across the area with more precip. Models have come into
better agreement with timing of this system, but there are
location differences. So chance pops for Wed through Thur looks
like a good forecast for now. Unfortunately, cooler air will still
be around and the precip could be a mix of rain and snow in parts
of the CWA.
Temps will be slightly below normal through the first part of the
extended period and then rise back to around normal for the last
half of the week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 513 PM CST Fri Mar 12 2021
VFR conditions expected through the period. Ceilings currently
around 10,000 feet from KSPI south, and lower ceilings expected to
remain further south as a dry northeast flow continues into
Saturday. Can`t rule out a few light rain showers near KSPI early
this evening, but think this should largely stay south.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Geelhart
SYNOPSIS...Geelhart
SHORT TERM...Auten
LONG TERM...Auten
AVIATION...Geelhart
Area Forecast Discussion
National Weather Service North Platte NE
536 PM CST Fri Mar 12 2021
.SHORT TERM...(This evening through Saturday night)
Issued at 324 PM CST Fri Mar 12 2021
The models are spread out with the location of the rain snow line.
The NAM indicates a snow level around 4000ft Saturday night which
lowers to 3500ft Sunday morning. The GFS, the warmest model,
suggests snow levels will remain at 5000ft or higher through Sunday
morning. This is related to the strength and direction of the low
level thermal advection. The forecast leans toward the NAM and
lowers snow levels Saturday night to around 4000ft. This would place
Sheridan county in a reasonably favorable zone for heavy snow by
around 06z Saturday night and marginally south and east of that area.
The atmosphere should moisten up this evening from south to north
as winds increase from the south and east below 700mb. Chance and
slight chance POPs are in place for light rain showers. The first
real round of good rain begins Saturday morning, moving up from
KS. A series of clusters of heavy rain showers should lift north
through wrn and ncntl Nebraska throughout the day Saturday and
Saturday night.
The NAM continues to indicate waves of elevated CAPE, generally less
than 500J/KG, and this should support isolated embedded thunderstorms
capable of small hail.
.LONG TERM...(Sunday through Friday)
Issued at 324 PM CST Fri Mar 12 2021
The GFS is pushing snow levels as high as 5000ft Saturday. This
is because the GFS has the strongest moisture and thermal
advections below h700mb pushing winds to 50kts or higher between
h850 and 700mb. WPC suggested this might be too strong and
suggested a solution closer to the ECM and NAM which shows winds a
bit weaker and snow levels around 4500ft Saturday which lower to
4000ft or below Saturday night and Sunday. The lower snow levels
in the ECM and NAM, around 3000ft, could be very problematic for
the Sandhills and nrn Nebraska Sunday and perhaps into Sunday
night. A prolific period of rain changing to heavy snow may
develop.
The delay in the onset of snow across wrn Nebraska noted by all
models is such that the winter weather highlights have been adjusted
as follows:
The Winter Storm Watch for Sheridan county is now in effect from
midnight Saturday through 12z Monday. Western Cherry county has been
added to this watch. The Winter Storm Watch for Garden and Deuel
counties has been downgraded to a Winter Weather Advisory for 3 to 5
inches of snow and also begins Saturday night and ends 12z Monday.
If the models continue to show rain changing to heavy snow across
the Sandhills Sunday, Winter Storm Watches or Warnings or Advisories
would likely be issued later tonight. These bulletins would cover
parts of the Sandhills possibly stretching as far east as highway 83
and as far south as highway 2.
The wind forecast is fairly similar to the previous forecast. A
check on the 500m AGL winds suggests 25 to 35 mph winds will develop
Sunday across the Sandhills and ncntl Nebraska. The guidance blend
is in place to capture these higher speeds.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 531 PM CST Fri Mar 12 2021
VFR conditions are expected this evening, then cigs will lower
after midnight creating MVFR conditions across north central and
western Nebraska. This will include both KVTN and KLBF terminals.
Rain will develop across western and southwest Nebraska early
Saturday, spreading slowly into north central Nebraska by Saturday
afternoon. Winds will generally be light overnight into tomorrow
morning, then increase to around 10 to 15 knots by Saturday
afternoon.
&&
.HYDROLOGY...
Issued at 324 PM CST Fri Mar 12 2021
The heavy rain, 2 to 3 inches, is still on track and there is
concern this rain may cause overland flooding across Custer county
and the Platte Valley where 3 and 6 hour flood guidance is
between 2 and 3 inches. The best guest on rain rates for this
system is 1/4 to 1/2 inch per hour. Model soundings suggest a
southerly storm motion of 25-50kt. This would require echo
training to accomplish flooding and the NAM and HRRR suggest the
potential for several waves of moderate to heavy rain Saturday
afternoon and Saturday night. Since this rain is expected fall
over a 24 to 36 hour period, the most likely outcome would be
minor overland flooding versus flash flooding.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
Winter Storm Watch from late Saturday night through Monday
morning for NEZ004-094.
Winter Weather Advisory from 11 PM MST Saturday to 6 AM MDT
Monday for NEZ022-056.
&&
$$
SHORT TERM...CDC
LONG TERM...CDC
AVIATION...Gomez
HYDROLOGY...CDC
Area Forecast Discussion
National Weather Service Newport/Morehead City NC
1004 PM EST Fri Mar 12 2021
.SYNOPSIS...
A weak cold front will push south through the area tonight and
early tomorrow. High pressure then builds in, though the cold
front will briefly move northward very close to the area Sunday.
By Sunday night, high pressure strengthens and remain over the
area through Monday. A weak area of low pressure is expected to
move across the area on Tuesday with a larger storm system
likely to impact the region into late week.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
As of 10 PM Friday...Cold front continues to work its way slowly
south into our region at late evening. Winds mostly SW across
the CWA, except for the far northern tier where they are
becoming more NW. Almost no precipitation associated with the
front at this point, the latest cycle of both the HRRR and 3km
NAM continues to show some patchy light showers developing,
primary over the southern tier near the coast overnight into
early Saturday morning. Any QPF will be very light. No changes
to the forecast temperatures by morning behind the front with
lows in the low/mid 50s in most areas.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
As of 3 PM Fri...Could see some lingering light showers across
the southern tier first thing in the morning, otherwise expect
dry and cooler conditions as high pressure builds in from the
north. Highs expected in the low to mid 60s inland and southern
sections but northeast onshore flow will keep temps in the 50s
across NE sections and the northern OBX will likely struggle to
reach 50.
&&
.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
As of 245 AM Fri...The front returns north into southern NC
Sunday bringing additional scattered showers are possible. High
pressure then builds in Monday with mostly dry conditions
expected. Then, a period of unsettled weather is expected as
weak low pressure will move over the area Tuesday, with a larger
storm system moving into the region Wednesday and Thursday.
Saturday night and Sunday...High pressure rapidly builds
overhead early Saturday evening, calming winds across the area.
Mostly cloudy skies should persist overnight, however at least
some clearing is expected overnight across NE NC, and temps will
be coldest there, dropping into the upper 30s, whereas the rest
of the area remains in the low to mid 40s. High pressure will
get squeezed between two upper level troughs on Sunday, before
rebuilding stronger Sunday night. This weakness will allow for
the cold front to return north towards the area, but likely
remain southwest of the forecast area. However, additional
scattered showers are expected to break out near this front as
lift becomes enhanced by subtle upper level energy moving over
the region. Despite clouds and light showers temps should
rebound into the 60s.
Monday...High pressure will build in rapidly Monday morning,
allowing for dry conditions through the day. Strong northerly
winds and lower low level heights will act to limit temps to
the upper 40s to low 50s for highs.
Tuesday through Thursday...Though there have been some
improvements, models are still having trouble with a weak
surface low that will be moving over the forecast area in some
fashion Tuesday. The ECMWF has now become the most southern
solution keeping the low offshore, while the GFS moves the low
well to the north of the area and into southern VA, with the CMC
somewhere in the middle. Though this spread brings in moderate
uncertainty to the temperatures forecast, all models bring in a
decent period of rain to the region, and have increased PoPs to
high chance for Tuesday.
As this system moves offshore Tuesday night, a brief drier
period is likely through at least Wednesday morning. At that
point a stronger storm system is expected to move out of the
Deep South, bringing an extended period of rain Wednesday
afternoon through at least Thursday. There remains large spread
between the models for this system as well, but guidance can at
least agree that this low pressure should pass to the west
(maybe by a large margin), so above average temperatures are
likely despite the rain.
&&
.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
Short Term /through 00Z Sunday/...
As of 7 PM Friday...VFR conditions expected to prevail through
this TAF cycle. Weak cold front now moving into the far
northern and western portions of the CWA. Some very light
showers may occur with this system, but coverage will be very
sparse and should have no impact on aviation operations. SW
winds of 10-15 knots, become N overnight and some 15-20 knot
gusts are possible during the day on Saturday.
Long Term /Saturday night through Tuesday/...
As of 320 AM Fri...VFR conditions are expected through Monday,
though there`s a small chance for a period of sub-VFR conditions
as a weak front brings scattered rain showers to the area
Sunday afternoon. High pressure will build back in Sunday night
leading to VFR conditions through Monday. A weak area of low
pressure will likely bring periods of sub-VFR conditions on
Tuesday.
&&
.MARINE...
Short Term /through Saturday/...
As of 1005 PM Friday...Cold front over the far northern tier and
should works it way south overnight. Winds are currently S/SW
10-20 knots, but will veer around to N/NE through the overnight
hours as the front moves south. N/NE winds will surge around
15-25 kt Sat morning behind the front. The surge will be short-
lived with winds diminishing through the afternoon. Seas around
3-6 ft through tonight builds to 4-7 ft Saturday.
Long Term /Saturday night through Tuesday/...
As of 320 AM Fri...Winds Sat night will become light and
variable and then turn to the W on Sunday at 5-15 kts. Seas will
also subside overnight, becoming 2-4 ft Sunday. Another surge
of northerly winds are expected as high pressure rebuilds into
the area Sunday night, with small craft conditions possible.
Winds will be N 15-25 kts, with seas building to 5-7 ft, through
Monday morning. Later Monday, winds subside and turn to the
NE/E 10-15 kts, and then strengthen out of the south on Tuesday.
Seas briefly subside Monday night, and then build again on
Tuesday.
&&
.MHX WATCHES/WARNINGS/ADVISORIES...
NC...None.
MARINE...Small Craft Advisory from 6 AM to noon EST Saturday for AMZ131-
135-230-231.
Small Craft Advisory until midnight EST Saturday night for
AMZ152-154.
Small Craft Advisory until 6 PM EST Saturday for AMZ156.
Small Craft Advisory from 6 AM to 5 PM EST Saturday for AMZ150.
Small Craft Advisory from 6 AM to 6 PM EST Saturday for AMZ158.
&&
$$
SYNOPSIS...MHX
NEAR TERM...CTC
SHORT TERM...SK
LONG TERM...SGK
AVIATION...CTC/SGK/CEB
MARINE...CTC/SK/SGK