Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/20/24
Area Forecast Discussion
National Weather Service Bismarck ND
945 PM CDT Tue Mar 19 2024
.KEY MESSAGES...
- High chances (90 percent) for accumulating snow Wednesday
afternoon through Thursday evening.
- Highest snow amounts Wednesday afternoon through Thursday
evening generally expected from Williston to Bismarck and
Jamestown to Oakes, North Dakota.
- Medium to high chances for more impactful winter weather this
weekend, especially southern North Dakota.
&&
.UPDATE...
Issued at 945 PM CDT Tue Mar 19 2024
No major changes were needed at this time. Low to mid level
clouds have begun to diminish at this time, while winds have
continued to weaken. The forecast remains on track.
.UPDATE...
Issued at 645 PM CDT Tue Mar 19 2024
The forecast remains on track at this time. Northerly winds with
occasional gusts have begun to diminish, and are anticipated to
begin to turn toward the northeast through the evening. The
occasional band of thicker low to mid level clouds continue to
push southward across the forecast area.
&&
.DISCUSSION...
Issued at 358 PM CDT Tue Mar 19 2024
Western and central North Dakota currently sits under the
influence of northwest flow aloft with a ridge axis parked over
the Pacific Northwest. A surface cold front crossed the state
from north to south last night and this morning and is now
located over South Dakota. This will mean colder lows tonight,
ranging from near zero in the vicinity of the Turtle Mountains,
to the lower 20s southwest. An extended period of below to well
below normal temperatures will then start in earnest on
Wednesday when highs will only in the mid 20s to mid 30s.
By Wednesday afternoon, a surface low will start to deepen over
eastern Wyoming with an inverted trough/pseudo warm front
extending northeast into western North Dakota. A weak initial
wave will interact with this surface boundary, leading to some
light banded snow Wednesday afternoon and night, eventually
extending from around Williston to Bismarck and Jamestown to
Oakes. For this initial warm air advection snow, models are
suggesting pretty strong mid level frontogensis but the
synoptic forcing remains fairly meager. Thus, for this first
round of snow will mainly see light to moderate rates leading to
a broad 1 to 2 inches or so.
By Thursday afternoon, the surface low will continue to deepen
as it moves near the western South Dakota/Nebraska border. Once
again we will see another area of strong mid level frontogenesis
develop and spread somewhere into central or southern North
Dakota. A stronger upper level wave will also move into the
region with better synoptic forcing than the previous impulse.
While the frontogenesis will outrun the synoptic forcing
slightly, there should be enough overlap for some potentially
more significant banding. Additionally, the dendritic growth
zone should be deep along the band with strong omega in the
layer. This will likely lead to some moderate to heavy snowfall
rates somewhere across the central or south. All in all, it
appears that a broad swath of 2 to 5 inches with isolated
higher amounts (total accumulations Wednesday afternoon through
Thursday evening) will be possible wherever the band sets up.
Looking at NBM probabilities, the chance for 4 inches or more
ranges from 60 to 90 percent from near Williston, south to
around Dickinson, over Bismarck and Jamestown, and down to the
south central and southeast North Dakota/South Dakota border.
Increasing that threshold to 6 inches, probabilities max out (40
to 70 percent) generally from Dickinson to Bismarck and in the
James River Valley south of Jamestown. Exact placement still
remains rather uncertain as the NAM and RAP are coming in quite
a bit further north. It is important to note that these models
have shown a clear northern bias with regards to banded snow
setups in the past, however. A Winter Weather Advisory will
likely be needed for this threat eventually, but given the track
uncertainty, we will issue an SPS for now and future shifts can
reevaluate. Snow should move out to the southeast Thursday
night.
We will see a break in measurable precipitation on Friday (some
flurries could be floating around) but highs will still be well
below normal in the 20s. Our attention then turns to the weekend
system. Precipitation chances will increase again by late
Friday night as another surface low deepens over eastern Wyoming
before kicking out somewhere into the central or northern
Plains by Sunday. Northwest flow aloft will gradually
transition to southwest flow aloft as a progressive ridge axis
crosses the state from west to east Saturday night. Snow will
spread across the state from west to east late Friday night,
potentially hanging around until Monday afternoon. The heaviest
period of snow currently looks to be Saturday evening through
Sunday afternoon. While it is still too far out to get specific
about totals, significant accumulations are possible. The latest
NBM 48-hour snow probabilities maximize the best chances for at
least 8 inches generally along and south of the Highway 200
corridor in the 50 to 80 percent range. Increasing the threshold
to 12 inches, probabilities here range from around 20 to 50
percent. That being said, the wave that will be the culprit for
the weekend snow is currently still located way over in the
central Pacific. Thus, we still have quite a ways to go before
we converge on the correct solution and there has been a bit of
an eastern and southern trend in recent runs. It should also be
noted that there are still plenty of various ensemble members
that bring little to no snowfall to western and central North
Dakota. Long story short, keep up to date with the latest
forecast as we move through the week and into the weekend. There
is still plenty of time for some significant changes.
&&
.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 945 PM CDT Tue Mar 19 2024
The 00Z TAF period will generally observe VFR conditions at all
terminals, though KJMS and KMOT may briefly experience MVFR
ceilings at the start. A possible exception to this may be the
intrusion of MVFR to IFR ceilings with potential visibility
reductions at the western terminals of KXWA and KDIK as a system
supporting snow moves in from late Wednesday afternoon, with
more widespread impacts anticipated beyond the end of the TAF
period. Winds will generally diminish through the TAF period and
veer toward the east.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Adam
DISCUSSION...ZH
AVIATION...Adam
Area Forecast Discussion
National Weather Service Burlington VT
1015 PM EDT Tue Mar 19 2024
.SYNOPSIS...
Snow showers develop overnight tonight, becoming scattered to
numerous with embedded snow squalls during the day on
Wednesday. The convective snow showers and gusty winds could
lead to hazardous travel. A strong cold front overnight
Wednesday will lead to sub-freezing daytime high temperatures
on Thursday and Friday. A late season winter storm may impact
the region this weekend, but plenty of forecast uncertainty
remains.
&&
.NEAR TERM /THROUGH WEDNESDAY NIGHT/...
As of 1006 PM EDT Tuesday...Fcst in good shape this evening as
snow showers continue across northern NY and slowly moving
toward parts of VT. Did bump temps up several degrees overnight,
especially CPV with clouds and southerly winds.
New guidance is pretty impressive with dynamics associated with
digging mid/upper lvl trof and developing instability during the
aftn hours on Weds. RAP soundings show very steep dry adiabatic
lapse rates thru 500mb acrs central/southern VT on Weds aftn, as
cooling aloft with trof occurs. Progged 500mb temps drop to
near -37C, while bl temps warm to near 4C/40F in the CPV. This
instability and dynamics, combined with some mid lvl moisture wl
be enough to produce numerous areas of convective precip on
Weds, with a mix of snow/graupel likely, even with sfc temps
near 40F. Sharp drop in sfc vis is likely in the heaviest
convective elements and given sounding profiles, would not be
surprised for a few lightning strikes, especially
central/southern and portions of eastern VT. Deep mixing
profiles should produce localized gusts 25 to 35 mph in the
heavier downdraft. As s/w energy exits our cwa by 00z, precip wl
become trrn focused under moderately strong 850mb to 925mb caa
on Weds night. Bottom line activity should result in additional
snowfall for the mtns over the next 12 to 36 hours.
Previous discussion below:
Tonight, southerly winds kick in, leading to a relatively mild
night. This would also be the first astronomical spring night of
2024 as astronomical winter ends at 1106 PM EDT. A warm front
will be lifting northwards into our region overnight, and bring
with it some warm advection snow. The forcing overall looks
rather unimpressive, so it would be in the form of a broken line
of snow showers. Temperatures will be rather marginal, mainly
in the upper 20s to low 30s, with mid 30s possible across the
Champlain valley. Generally, up to an inch of snow could fall
across the Champlain Valley, with 1-3 inches overnight across
our northern NY zones and spine of the Greens. There is a low
probability of southern St Lawrence, Franklin and Essex county
in NY seeing 4 inches overnight, but given the relative
unimpressive warm frontal dynamics, we opted against hoisting
any Winter Weather Advisory.
Then heading into the day tomorrow, a potent piece of northern
stream shortwave energy will trigger another round of convective
snow showers and even a few embedded snow squalls. Snowfall
accumulations look to be topographically driven and elevation
dependent. Strong cold air advection will result in lapse rates of
over 8.5C/km up to 800mb as well as 50-100 J/kg of surface based
CAPE. Indeed, the SLU snow squall parameter indicates good
probability of snow squalls across our region, with somewhat higher
odds across the Adirondacks and Northeast Kingdom. However, just
about anywhere across North Country could see a few convective snow
showers. Given the overall dynamics, the most probable mode of these
showers would be popcorn or cellular in nature, rather than
quasilinear in organization. This also means that while there should
be scattered to numerous showers accompanied by gusty 25-30 mph
winds, the snow squall threat is somewhat lower. Temperatures should
also climb into the 40s across the Champlain Valley as well as
southern and portions of eastern Vermont. If the wrap around cold
air is delayed, it is possible that St Lawrence valley could also
reach the low 40s. In other words, the convective snow showers could
be mixed with graupel and even rain at times, although dynamical
cooling from wet bulbing should keep the hydrometeor more frozen
than liquid. Nonetheless, across the valley locales, unless there is
a more intense cell, roadways should generally be wet.
Therefore during the day on Wednesday, most of the accumulations
should be confined to the terrain mainly above 1000 ft elevation as
925mb temperatures remain in the 0 to -2C range. So expect minimal
accumulation, with the best chance for a quick coating of roadways
during a heavier snow shower or embedded squall in the valley
locales. It would be a different story, however, across the
typically favored upslope areas of the Adirondacks and spine of the
Greens, where upwards of 4 inches could accumulate. These areas
would also have the best chance of seeing localized 35 to 40 mph
gusts. High temperatures top out in the low to mid 40s across
the valleys and mid to upper 30s across the higher terrain.
Towards the afternoon hours, there would likely be a time where
drier weather prevails and the sun could even make a return. The
several hours of drying also does greatly reduce the likelihood
of flash freeze as sub- freezing temperatures only arrive after
sundown for most locations. Afternoon temperatures might need
to be adjusted upward while PoPs and sky cover would need to be
lowered if that is the case.
It does get more interesting overnight Wednesday as cold air
advection continues. 925mb temperatures fall sharply into the -7 to -
10C range, allowing it cold enough for snow to accumulate even down
to the valley. However, the jet dynamics remain northern stream
dominated, with minimal southern stream connection. The result is
continued bouts of convective snow showers overnight Wednesday. A
feature that bears watching is the 700mb low potentially closing
off, which would lead to more impressive widespread snowfall amounts
of over 4 inches rather than being orographically driven. However,
the current suite of global deterministic guidance shows the low
closing to our east, which would favor the best snow across Maine.
And if we were to examine ensemble guidance, there remains little to
no indication that the upper low will actually close off, so the
most likely solution remains a terrain dependent snowfall event,
with minor accumulations across the valleys. If the upper low does
close off as some deterministic guidance are suggesting, then
Northeast Kingdom could see higher amounts. But until more evidence
presents itself, that is a low probability outcome.
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY/...
Low pressure will continue to eject northeastward Thursday with
gusty northwesterly winds and strong cold air advection expected
through Thursday night. Snow chances will be diminishing Thursday
except for the northern Green Mountains where flow will keep some
lighter accumulations ongoing into Thursday night. Gradients begin
to weaken overnight, but breezes will likely continue into Friday as
high pressure ridging tracks over the North Country. Temperatures
and wind chills will be the most notable weather parameters with
values struggling to get to the freezing mark Thursday before
tanking overnight under continued cold air advection. Friday morning
will be frigid with wind chill values ranging from -10 to +5 across
the North Country. While northerly flow continues to weaken Friday,
temperatures will generally remain below freezing except towards
southern Vermont where some spots will reach the mid 30s. Flow
Friday will switch southwesterly late in the day with clouds
increasing.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Main story for the weekend is the potential for a potent storm
system to move through, or just south of, the region. This system
will bring more accumulating snow, but the amounts remain
questionable and dependent on timing and degree of phasing of
northern stream and southern stream troughs. Ensembles and
deterministic models are coalescing on the idea that these troughs will
phase, but the trend has been for a more eastward trajectory of this
phasing. Of note, will be decreasing SLR through the weekend likely
resulting int a wetter character of snow as a mid-Atlantic low
becomes moves northeastward bringing relative warm air advection.
Ensembles are showing widespread probabilities of 50-80% chance of
snowfall amounts greater than 3 inches for much of the North
Country, but chances drop sharply for 6 inches or more outside some
of the higher terrain. As such, potential exists for a late season
winter storm to bring slick conditions and possibly a period of wet,
heavy snow.
Another round of decent cold air advection will likely follow in the
wake of this system keeping temperatures below seasonal averages at
least through Sunday night. Heading into the work week, model
signals favor amplification of the upstream trough over central US
and downstream offshore high pressure. This pattern would result in
another warming trend above seasonal averages as early as Tuesday.
&&
.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
Through 00Z Thursday...A mix of flight conditions this
evening, with most terminals VFR with the exception of KMSS and
KSLK with MVFR and IFR conditions respectively. Snow showers
have begun across northern New York, bringing reduced
visibilities generally between 3 to 5 SM and some lower
ceilings and these showers will gradually move east into Vermont
overnight, with MVFR conditions expected across most terminals.
KSLK will have the best chances for IFR tonight, although
localized IFR will be possible within any snow showers. After
12Z, improvement is expected with lifting ceilings. Winds
overnight will generally be less than 10 knots from the west,
increasing after 12Z and becoming gusty around 15Z.
Outlook...
Wednesday Night: VFR. Chance SHSN.
Thursday: VFR. Slight chance SHSN.
Thursday Night: VFR. NO SIG WX.
Friday: VFR. NO SIG WX.
Friday Night: Mainly VFR, with local MVFR and IFR possible.
Likely SN.
Saturday: Mainly MVFR, with local VFR possible. Chance SN, Chance
RA.
Saturday Night: Mainly VFR, with local MVFR possible. Slight
chance SHSN.
Sunday: VFR. NO SIG WX.
&&
.EQUIPMENT...
The ASOS at KMPV, Knapp State Airport in Berlin, remains down
to an FAA comms line issue. Time of return to service is
unknown at this time.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...None.
&&
$$
SYNOPSIS...Chai
NEAR TERM...Chai/Taber
SHORT TERM...Boyd
LONG TERM...Boyd
AVIATION...Kremer
EQUIPMENT...Hastings
Area Forecast Discussion
National Weather Service Northern Indiana
715 PM EDT Tue Mar 19 2024
.KEY MESSAGES...
- Dry and seasonable through Thursday, although still breezy
on Wednesday. Gusts 25 to 35 mph possible.
- Several hard freezes likely this week. Coldest night of the
next 7days will be Wednesday with lows in the upper teens to
low 20s.
- Next chance for rain and snow showers during the day Friday
ahead of a cold front.
- Dry and seasonable weekend. Upper 50s to low 60s Monday with
additional chances for rain.
&&
.DISCUSSION...
Issued at 631 PM EDT Tue Mar 19 2024
A tight pressure gradient ahead of an approaching cold front has
made for a breezy first day of spring! Wind gusts have been between
35-40 mph in most locations, with a few isolated 45-50 mph gusts at
the typical gusty spots (mainly along the lakeshore and in Fort
Wayne, Lima, and Van Wert). Wind gusts will diminish after sunset
down to 15-20 mph. No precipitation is expected as the cold front
passes through overnight but it will be chilly once again.
Overnight, lows drop to between 28 to 32 degrees (coldest in far
southern Lower Michigan); not everyone will experience a hard
freeze.
For Wednesday, another seasonable and windy day is in store. Gusty
winds today have been able to help transport cooler, drier air
towards the surface, and the same is expected on Wednesday. The RAP
and the HRRR (and most of the hi-res models) have done a good job
today accounting this deep mixing, so I used these models in the
wind gust forecast for Wednesday. Thinking winds will again be
breezy Wednesday with gusts 25 to 35 mph, and isolated 40+ mph gusts
will be possible as well. There will be substantial radiational
cooling Wednesday night as winds diminish and cloud cover
dissipates overnight. The NBM isn`t taking this into account but
previous pattern recognition tells me that it`ll be a few
degrees colder Wednesday night than what we`ve been forecasting
the past few days. Lowered low temperatures Wednesday night down
to the upper teens to low 20s.
Thursday night through Saturday night, hard freezes will be likely
once again. The counties with the best chances for several hard
freezes in a row will be southern Lower Michigan and far northern
Indiana (mainly along and north of I-80/I-90). Flowers and fruit
trees have started to bloom this week (especially in north-central
Indiana) as a result of recent early spring warmth. Although the
highest susceptibly is further south and west of our forecast area,
it wouldn`t be a bad idea to be cautious. Be sure to cover up or
bring any sensitive vegetation indoors, if possible, as will be
susceptible to the cold nights ahead.
Rain/snow chances arrive late Thursday night after sunset and
persist and into Friday ahead of a cold front. Depending on how cold
temperatures are Thursday night as the system arrives, precipitation
may start as snow before changing over to all rain during the day
Friday. As for the weekend, long range model guidance keeps a dry
and seasonable both days. Will stick with the NBM blend regarding
temperatures over the weekend, which has with highs in the low to
mid 40s. By Monday, warmer (highs in the upper 50s to low 60s) with
another chance for rain as another cold front sweeps though.
&&
.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 710 PM EDT Tue Mar 19 2024
Winds will begin to gradually relax by 00Z-01Z before another
cold front moves through late overnight into early Wednesday
morning. After the front passes through, winds shift more
northwesterly and will increase in speeds, becoming gusty again
by mid- morning Wed. Gusts to around 30kts will be the primary
concern as we expect VFR ceilings and visibilities through the
the TAF period.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...Small Craft Advisory until 2 AM EDT Thursday for LMZ043-046.
&&
$$
DISCUSSION...Johnson
AVIATION...Norman
Area Forecast Discussion
National Weather Service Phoenix AZ
508 PM MST Tue Mar 19 2024
.UPDATE...Updated 00Z Aviation Discussion.
&&
.SYNOPSIS...
A slow moving low pressure system will result in the redevelopment
of scattered showers and thunderstorms this afternoon and evening,
mainly over the high terrain of southcentral AZ. This feature will
finally exit the area on Wednesday resulting in a return of dry and
tranquil conditions across the region. Upper level ridging will
build over the Desert Southwest through the remainder of this week,
resulting in much warmer temperatures with highs reaching the mid
80s across the lower deserts. Another weather system will arrive on
late this weekend into early next week, bringing cooler and
potentially wet weather to our area.
&&
.DISCUSSION...
A stagnant rex block pattern remains in place over the Western CONUS
with a ridge of high pressure centered over the Intermountain
West and a persistent upper low over the Desert Southwest. This
low has been responsible for shower and thunderstorm activity over
the past several days and we are seeing the redevelopment of
showers again this afternoon. Current radar trends show this
activity mainly confined to the higher elevations of Maricopa and
Gila counties, but a few showers have been trying to develop over
the lower deserts where there is ample instability available.
Latest RAP derived ML CAPE values are around 300-500 J/kg and
lapse rates are now exceeding 7 deg C/km in southcentral AZ. This
environment will be conducive for a few stronger thunderstorms
over the next few hrs with the main threats being small hail and
gusty winds. If convection becomes organized enough north of the
Phoenix Metro, we may see an outflow boundary push south through
the valley this evening with wind gusts around 20-25 kts possible.
Showers and storms should dissipate after sunset leading to
tranquil conditions overnight. Low temperatures will again be
slightly below normal tonight mainly in the upper 40s to lower 50s
across the region.
Heading into Wednesday, low pressure aloft will continue to slide
ewd into NM. A trailing shrtwv trough will sweep across northern AZ
Wednesday afternoon which should provide just enough instability
and lift for additional shower development across the AZ high
country, mainly over the Mogollon Rim, but a few showers may be
possible in N Maricopa or S Gila Counties. Temperatures on
Wednesday will be slightly warmer than today, especially across
SE California and SW AZ where highs are expected to reach the low
to mid 80s. Upper level ridging will then build over the region
on Thursday and Friday, promoting above normal temperatures and
dry conditions. Highs both days are expected to top out in the low
to mid 80s across the lower deserts. There is even a 40-50%
chance of highs reaching 90 degrees in the Imperial Valley by
Thursday afternoon. These warm temperatures will result in a minor
heat risk for the most most vulnerable.
By this weekend, we will begin to see a transition in the upper
level pattern from ridging aloft to troughing over the western
CONUS. Saturday will feature continued above normal temperatures
with breezy conditions developing across SE California due to a
strengthening 500-700 hpa jet. Highs will be around 5 degrees
above normal in southcentral AZ which will still be under the
influence of the upper ridge. Ensembles are in good agreement that
troughing will return to the region on Sunday. Depending on the
strength and depth of this trough, we could see the return of
unsettled weather and cooler temperatures across portions of
southcentral AZ. Rain chances are still very uncertain at this
time. NBM is depicting low end PoPs <25% for E Maricopa and S
Gila Counties beginning Sunday and lasting into early next week,
but this will likely change in the coming days. What is more
certain is the arrival of cooler temperatures Sunday into early
next week with highs only expected to reach the low to mid 70s.
Details about this next system will become more apparent in
subsequent shifts.
&&
.AVIATION...Updated at 0005Z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
An outflow has moved through the Phoenix Metro causing the winds
to shift and are now out of the N/NE, with gusts mainly around
20-25 kt. Gusts should subside over the next couple of hours, but
NE`rly winds will remain. Winds will go light and variable late
this evening through the overnight hours, but may predominately be
out of the E. Winds are anticipated to do their typical westerly
switch once again tomorrow afternoon. FEW-SCT clouds with bases
aoa 9 kft will start to lift and scatter out with only high clouds
expected through the overnight and morning hours. FEW-SCT clouds
with bases aoa 9 kft are expected once again tomorrow afternoon.
Southeast California/Southwest Arizona including KIPL and KBLH:
No major weather issues will exist through Wednesday early evening
with a few periodic cloud decks above 8K ft AGL. Extended time
frames with light and variable winds will be common, though in
general W/NW directions will be favored.
&&
.FIRE WEATHER...
Low pressure will continue to promote chances for showers and storms
across the higher terrain areas of the eastern districts, with very
slight chances of an isolated shower or thunderstorm around enhanced
terrain features of the western districts. Winds outside of any
thunderstorm activity will be light with occasional afternoon
breeziness. MinRH values over the next few days will remain above 20-
25% before decreasing later this week as high pressure sets in.
Temperatures will hover right around normal today before quickly
warming to above seasonal normals during the latter portion of the
week.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&
$$
DISCUSSION...Salerno
AVIATION...Berislavich/18
FIRE WEATHER...RW