Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/24/17
Area Forecast Discussion
National Weather Service Burlington VT
1042 PM EST Mon Jan 23 2017
A wintry mix of precipitation will overspread the North Country
after midnight tonight and become heavy at times during the
Tuesday Morning commute. An extremely hazardous Tuesday Morning
commute is anticipated with the icy roads and poor
visibilities. A plowable snow and sleet accumulation is
likely...along with some ice. Improving weather with above
normal temperatures return by Wednesday.
.NEAR TERM /THROUGH TUESDAY NIGHT/...
As of 1033 PM EST Monday...Latest trends across e-central NY and
s-central VT show sleet as the predominant precipitation type.
With slow-moving closed mid-level circulation across the mid-
atlantic states, getting plenty of atlantic moisture and above
freezing temps aloft moving in on ely 850mb flow of 50-55kts per
RAP at 03Z across central New England. The 00Z NAM is in line
with observational trends, showing predominantly sleet across
much of our region as precipitation develops and intensifies
during the pre- dawn hours. It`s rare to get a predominantly
"sleet storm", but that appears to be the case given expected
thermal profiles, along with pockets of freezing rain during
Tuesday morning (especially central/ern VT). Impacts on the
morning commute will likely be significant, with moderate to
heavy sleet, with pockets of freezing rain expected resulting in
icy and hazardous roadways and sidewalks. All in all, no
significant changes needed to the forecast attm. Have adjusted
onset timing to be a bit quicker, with precipitation
(predominantly sleet) underway at SLK/RUT/LEB/VSF and spreading
nwd at 0330Z. Anticipate sleet into BTV by 05Z. Heaviest mixed
precipitation rates generally 08-14Z most locations.
Previous discussion...A complex and extremely difficult
forecast with regards to thermal profiles and associated precip
types. Complex thermal profiles have started with Whiteface down
to 19F and Mansfield at 21F...while BTV is 36F. We have taken a
conservative approach in the snow accumulation
department...with a general 2 to 6 inches of snow/sleet
expected...along with some ice accumulation...especially
eastern/central VT...including the Northeast Kingdom. We also
have to watch low level cold air bleeding down the CPV on north
winds...resulting in more freezing rain. Our thinking is
generally between one and two tenths of an inch of ice...with
some isolated higher amounts in central/eastern VT.
Winter weather advisory continues from 7 PM tonight until 10 PM
Tuesday for our entire forecast area. The most intense part of
the storm with the highest precip rates will occur right during
the Tuesday Morning commute (4 AM to 9 AM)...making for an
extremely hazardous morning commute.
Water vapor shows well defined closed cyclonic circulation over
central NC...with a tremendous feed of deep Atlantic moisture
advecting into the NE CONUS/Mid Atlantic. IR sat pic shows a classic
mature cyclone with well defined warm conveyor and strong upper
level divergence pattern with embedded dry slot over eastern NC.
This circulation will slowly move northeast with surface low pres
tracking from eastern NC to Cape Cod by 00z Weds. Overall models in
excellent agreement with tracking of surface low pres...along with
showing deeply negative mid/upper level trof lifting northeast...but
weakening through time. This weakening mid/upper level
feature...along with limited low level cold air advection will
minimize backside bonus snow potential on Tuesday Night.
NAM/GFS show band of very strong lift/fgen forcing with strong 700
to 500mb vorticity advection lifting from south to north across our
cwa between 2 AM and 10 AM tuesday. Helping to enhance deep layer
lift and low level moisture advection will be nose of 45 to 55 knot
easterly 850mb jet and anticyclonic curved 250mb jet over eastern
Big question does this strong lift/upper vertical velocities
cool the column just enough to support snow or does the low level
easterly jet advect warm nose of 4 to 6C air into our region and
support a mix of sleet and freezing rain. Still plenty of
uncertainty with regards to low level thermal profiles with latest
12z GFS supporting a mostly snow event...while NAM/ECMWF is a mix of
sleet/freezing rain...while GEM is in the middle. For example the
NAM Bufkit at BTV at 10z shows 5C at 5000 feet associated with
southeast wind of 40 knots....while temps at 2000 feet are -6C with
low level north/northeast winds draining down the CPV.
Meanwhile...same time period GFS shows isothermal layer near 0C from
4500 to 7500 feet with -6C between 1500 and 3500 feet...supporting
more snow. Based on complexity of thermal profiles and
uncertainty...have gone conservative with snow and utilized a model
blend of NAM/BTV4km/GFS/ECWMF to determine precip type and
associated snow/ice amounts. This supports a mix of snow/sleet with
areas of freezing rain...thinking during the heaviest precip rates
mostly snow will occur...with some sleet. As warm layer becomes
better established on Tuesday and low level cold air bleeds down the
CPV/CT River Valley profiles support more of a freezing rain
threat...with more snow/sleet across Northern NY where warm nose is
limited. However...boundary layer temps are just marginally cold
enough...so ice accumulation is uncertain at this time...especially
CPV where temps today are in the mid/upper 30s. Given downslope
easterly flow...would not be surprised if temps warm into the
mid/upper 30s from Mt Holly to East Middlebury to Underhill to
support some rain on Tuesday Afternoon.
Expecting a break in the heavier precip by mid-morning into early
afternoon...before next round of light to moderate mix
rain/sleet and freezing rain develops on late Tues
Afternoon/Evening...as closed system lifts northeast. Timing of
this secondary surge of precip could impact the evening commute
with another round of light wintry mix slowly changing back to
snow showers from west to east toward midnight...as profiles
Bottom line for snow/sleet accumulation is generally 2 to 6 inches
with some higher amounts possible Dacks/SLV and parts of the
southeast upslope region of the Green Mountains. Ice accumulations
of a trace to 0.10 of an inch CPV...with 1 to 2 tenths of an
inch possible across central/eastern VT...including the
Northeast Kingdom. The heavy wet snow/low ratios and freezing
rain will probably lead to some power outages.
Overall storm total qpf will range between 0.50 and 1.0 with highest
values along the se upslope regions of the Green Mountains from
Ludlow to Mansfield and another stripe along the eastern Dacks.
Expect some shadowing along the western slopes from near
Rutland/Danby to North Underhill and over the Northeast Kingdom.
Given winds expect terrain to impact qpf amounts for this system.
Qpf ranges from 0.25 to 0.75 across the western dacks/slv...as
moisture depth is less.
Wind threat is minimal and relatively small area along the western
slopes from Danby/Rutland to East Middlebury...with isolated gusts
to 30/35 mph possible. Mixing is limited as strongest winds occur
when precip rates are the strongest.
Temps cool into the mid/upper 20s to lower 30s tonight and warm
upper 20s to mid 30s...warmest along the western slopes.
.SHORT TERM /WEDNESDAY THROUGH THURSDAY/...
As of 332 PM EST Monday...By Wednesday morning aforementioned
low pressure will be over the Gulf of Maine and Nova Scotia,
with deep layer moisture rapidly shifting northeast of the BTV
CWA through the day. Could see some lingering snow showers
across the high peaks in the morning, but by mid-day weak
mid/upper level ridging briefly builds in so expect to see some
afternoon sun, especially across central and southern areas.
Highs will continue to run well above normal in the 30s.
Break in active weather is very short as another deep mid/upper
level trough over the central CONUS begins to shift eastward
Wednesday night, with surface low pressure over the Great Lakes
Wednesday shifting northeast in the Ottawa/St. Lawrence Valley.
Favorable southwesterly flow combined with increasing low/mid
level moisture will enhance precipitation potential downwind of
Lake Ontario and points northeastward into northern New York,
the northern Champlain Valley and north-central Vermont through
the night with boundary layer temps supporting mainly snow
except a rain/snow mix across southern portions of St. Lawrence
county. As the boundary layer warms further Thursday,
precipitation becomes more mixed area-wide until the low pulls
east of the area Thursday afternoon and cold air advection
develops on increasingly northwest flow. Overall not looking for
a lot of QPF through the period, so snow amounts will generally
be a dusting to perhaps 2 inches, and locally up to 2-4" across
the high peaks.
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 332 PM EST Monday...Long term period for Thursday night
through the weekend highlights a broad upper trough across the
majority of the CONUS with no big systems on the horizon, rather
daily chances for light precipitation especially across the
high peaks. Temperatures return to more seasonal values though
still slightly above normal with highs mainly in the 20s and
lows in the teens which supports mainly snow as the dominant
ptype for anything that does fall. Best chances look to be
Thursday night through Sunday as we remain under cyclonic
northwesterly flow with light snow accumulating along the higher
peaks, followed by drier conditions for Sunday into Monday.
.AVIATION /04Z Tuesday THROUGH Saturday/...
Through 00z Wednesday..VFR overall to start the period with KRUT
being the exception with MVFR ceilings. Conditions will deteriorate
rapidly to a mix of low MVFR/IFR as wintry precip moves in
overnight after 07Z. The forecast trend continues to show the
precip moving in late overnight between 03-06z in southern
Vermont and between 09-12z across central and northern Vermont
and across Northern New York. Expect a variety of precip types
with a mix of rain/snow/sleet and freezing rain possible.
Additionally with the icing layers just off the surface
conditions could be dicey with icing in the low levels of the
atmosphere. An easterly low level jet is expected to create
gusty winds at RUT and also cause issues with low level
turbulence and wind shear due to the speed differences from the
ground to 2500-3000 feet agl. Winds overall will also be
northeasterly at 05-10 knots for most of the period.
Outlook 00z Wednesday through Saturday...
00z Wednesday - 12z Wednesday: MVFR/IFR trending towards
VFR/MVFR as the wintry precip tapers off Tuesday evening.
12z Wednesday - 12z Thursday: VFR with skies becoming cloudy
12z Thursday onwards: Generally VFR with on and off chances of
MVFR in periods of rain and snow showers.
VT...Winter Weather Advisory until 10 PM EST Tuesday for VTZ001>012-
NY...Winter Weather Advisory until 10 PM EST Tuesday for NYZ026>031-
Area Forecast Discussion
National Weather Service Buffalo NY
1026 PM EST Mon Jan 23 2017
Strong low pressure off the Mid Atlantic will move northeast along
the east coast into Tuesday bringing widespread precipitation to
the region. Rain will spread northward across the entire area
before mixing with and then changing over to snow overnight with
portions of central and north central New York receiving
significant snow accumulations. Weak high pressure will then cross
the region Tuesday night into the first part of Wednesday before
low pressure slides north of the region Wednesday night into
Thursday dragging a cold front through the area. Colder air behind
the front will slowly filter into the region into this weekend
with lake effect snows increasing east of the Lower Great Lakes.
.NEAR TERM /THROUGH TUESDAY/...
...Accumulating wet snow to impact a portion of western and north
central New York through Tuesday...
Latest water vapor imagery showing a large storm system over eastern
North Carolina. This feature will slowly churn northward along the
Mid Atlantic coast tonight, while a highly anomalous easterly flow
in the low levels will pump a wealth of Atlantic moisture back
across our region. The moisture will be lifted by a combination of
divergent upper level flow, significant height falls and some weak
H925-70 frontogenetic forcing. While this will virtually guarantee
that all areas will pick up some precipitation, the challenging
portion of the forecast will deal with both precipitation type and
Latest regional radar imagery showing the leading edge of
precipitation has finally worked its way into the Southern Tier and
nearing the Finger lakes. Precipitation type so far across the
western Southern Tier still rain, with a mix developing east
across the Elmira/Ithaca/Binghamton area. Colder air will
continue to feed in from the northeast and a gradual transition
over to snow/sleet is still expected. Latest HRRR seems to have a
decent handle on current trends. It is not overly impressive
across the western half of the area tonight, suggesting a gradual
diminishing trend to the precipitation and showing a greater
precipitation focus up across eastern portions of the area. Will
maintain current headlines as we have in place and continue to
monitor trends. Latest HRRR continuing to suggest the potential
for decent snows of upwards of 6 inches across the Finger Lakes
into the North Country, but probably falling shy of this west of
the Finger Lakes.
On Tuesday...the vertically stacked storm will be nearly stationary
off the New Jersey coast. Winds aloft will back in the process...and
this will encourage stronger cold advection that will send the whole
column to below freezing. Any mixed precipitation in the morning
will then change to just snow. The most significant accumulating
snow will be during the early morning...then as we work through the
midday and afternoon...substantially weaker forcing and gradual
drying in the mid levels will lead to a tapering off of the snowfall
from west to east. Additional snowfall on Tuesday will range from an
inch or so over the far western counties to about three inches
across the North Country.
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
The middle portion of the week will be the transition period back to
a more typical winter pattern. Low pressure in the Gulf of Maine
Tuesday night will gradually giveway to a ridge of high pressure
which will extend from the Southeastern states into Western New
York. There may be some lingering snow showers across eastern
portions of the cwa from the departing low with little if any
accumulation. Otherwise, it will be dry with lows ranging from the
mid 20s to lower 30s.
Wednesday will start with a narrow ridge across the region and low
pressure developing near Lake Michigan. 12Z model consensus is
slower with this system, with precipitation expected to mainly hold
off until Wednesday afternoon. The southerly flow will warm areas
south of Lake Ontario into the lower to mid 40s resulting in mostly
rain showers. It will be cooler east of Lake Ontario where some snow
is possible even though any accumulations will be light.
The surface low is forecast to track into Southern Ontario Wednesday
night, with an increasing southwesterly flow. Late Wednesday night
and early Thursday morning it will be windy northeast of the lakes.
The track of the low is favorable for strong winds, however the
system is weakening as it passes by suggesting wind gusts in the 45
Otherwise, the system will bring several rounds of precipitation to
the area, with the surface low, upper level trough, and enhanced by
upsloping as the flow becomes WSW on Thursday. Precipitation amounts
should generally be light Wednesday night into Thursday, with the
greatest amounts east of the lakes. Temperatures will gradually cool
with the passage of the mid-level trough, with higher elevations
changing to snow late Wednesday night, and a mix of rain and snow
during the day Thursday. Modest accumulations of a few inches are
possible on the Tug Hill and across higher terrain in the Western
Southern Tier. Amounts should be held down due to the marginally
cold enough temperatures aloft.
By Thursday evening, consensus 850mb temperatures are about -8C,
which is cold enough for all precipitation to change to snow.
Temperatures aloft Thursday night will result in only marginal lake
induced instability, but the flow will be quite moist with upstream
lakes providing some extra moisture. Also, the westerly flow is
favorable for banding and upsloping. Off Lake Ontario, expect lake
snows to focus on the Tug Hill or just south into Northern Cayuga
and Wayne county. Off Lake Erie, suspect that the Chautauqua ridge
will funnel winds with a WSW flow at times. Lake snows should focus
on the Western Southern Tier and may extend into the Boston Hills.
Expect the lower resolution model guidance available during this
timeframe does not resolve this funneling and is too far south with
its QPF. Moderate snow accumulations are possible off both lakes on
Thursday night. This is the start of what looks to be an active
period for lake effect snow, potentially requiring lake effect
headlines as forecast confidence increases.
.LONG TERM /FRIDAY THROUGH MONDAY/...
A return to winter this period as the upper air pattern becomes
amplified...allowing for cold air that has been building across the
arctic to be tapped into and drawn southward across the Great Lakes
region. This cold air will not be extreme, but will be cold enough
to yield a lake response off the Eastern Great Lakes. The current
storm system over the eastern US will linger over eastern Canada
next week, this in response to a building surface ridge near
Greenland. Meanwhile an upper level ridge will also build across
western NOAM and this will result in northwest flow across central
Canada and down across the Great Lakes region this forecast period.
For the Friday through Monday time period our region will remain
active, with several shortwave troughs refreshing a cold airmass
over the region...an airmass that will become cold enough to support
lake effect snow. The shortwaves will alter the low level wind field
through the period, allowing the lake effect bands to
oscillate...but a general northwest flow will make the Southern
Tier/Ski Country as well as SE and E of Lake Ontario prime real
estate for accumulating lake snows...that could become significant.
Temperatures at 850 hPa will average -10 to -13C below zero Friday
through Sunday supporting lake effect snow off lakes that are around
+2C (Erie) and +5-6C (Ontario). Lake induced equilibrium levels will
rise to around 10K feet and with the shortwaves bringing increased
synoptic moisture lake effect snow bands could become fairly strong.
By Monday temperatures will drop to around -13 to -16C over the
region, bringing perhaps the chilliest day this period. An upper
level ridge will near the region Monday night, and this feature will
likely end the lake effect snow through Monday night.
Air temperatures just above normal Friday, will fall to near normal
Saturday-Sunday and then below normal Monday.
.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
A storm system moving up the east coast will bring a period of rain,
changing over to snow tonight into Tuesday. Some sleet and
freezing rain is likely during the transition to snow. After the
precipitation transitions over to snow overnight expect IFR/LIFR
conditions at all terminals through Tuesday afternoon. The
exception may be at KJHW, where vsby may come up as snow tapers
off very late in the period, however IFR/LIFR cigs will hang in.
The heaviest snow will fall across central and north central NY,
where vsbys down to a mile and possibly lower can be expected.
Tuesday night...Areas of MVFR/IFR with wet snow.
Wednesday and Thursday...VFR/MVFR with a chance of rain and snow.
Friday...VFR/MVFR with a chance of snow showers.
Saturday...VFR/MVFR with a chance of snow showers.
A deep storm system off the Mid Atlantic coast will combine with
high pressure over northern Quebec to produce a fairly strong east
to northeast flow across Lake Ontario overnight into Tuesday. This
will make it quite choppy for the nearshore waters west of Mexico
Bay, so a small craft advisory will remain in effect for those
areas. A small craft advisory also remains in effect tonight for
the Lower Niagara River. A weaker surface pressure gradient will
be found over Lake Erie.
The aforementioned storm system will push north along the New
England coast later Tuesday and Tuesday night, while a ridge will
advance from the Upper Great Lakes. This will promote relatively
light winds and negligible waves on the Lower Great Lakes through
the middle of the week.
NY...Winter Weather Advisory until 7 PM EST Tuesday for NYZ007.
Winter Storm Warning until 7 PM EST Tuesday for NYZ005-006-008.
Winter Storm Warning until 10 AM EST Tuesday for NYZ004-013-
Winter Weather Advisory until 10 AM EST Tuesday for NYZ003-011-
MARINE...Small Craft Advisory until 3 AM EST Tuesday for LOZ030.
Small Craft Advisory until 1 PM EST Tuesday for LOZ042-043.
Small Craft Advisory from 4 AM to 1 PM EST Tuesday for
Area Forecast Discussion
National Weather Service Cleveland OH
916 PM EST Mon Jan 23 2017
Low pressure near the North Carolina coast will move off shore
this evening and then track northeast along the coastline through
Tuesday night. To our west, high pressure in the central plains
will briefly ridge into the region on Tuesday. The next storm
system will move into the Central Great Lakes from the Plains on
Wednesday. A cold front will move through late Wednesday and
usher in colder air Thursday through the weekend.
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
Water vapor imagery shows bands of moisture rotating away from the
upper low along the coast. Have noted an uptick in rain in
northwest Ohio as one of these bands seems to be interacting with
the deformation axis. Although rain will be light, raised pops in
northwest Ohio. This band is expected to weaken with time but
also shift eastward overnight. Will continue with a mention of
light rain and drizzle for most of the area overnight. Have also
extended the chance of snow westward to include
Ashtabula/Trumbull/Mahoning Counties overnight with thermal
profiles that are marginal to support snow. Better chances are
over the higher terrain of NW PA but little to no accumulation
Previous discussion...Satellite shows breaks in the clouds near
KERI and across the eastern third of the lake but this should fill
in over the next several hours. Otherwise clouds will continue
through the night. Follow the HRRR forecast reflectivity trends
into the night showing the best rain chances remaining east third
as flow around the east coast low rotates moisture back into the
area. Will however continue with chance pops west half into the
night. Pops decrease overnight west to east as moisture finally
begins to pull out. There is some question as to ptype overnight.
The NAM continues to bring 850mb temps down to -1 to -2C late this
evening and then temps rise to 0 to -1C by morning. The GFS drops
just below 0C after 06z. Dont really think this is low enough to
put a lot of snow in the forecast so aside from a possible early
morning mix far NERN OH and NWRN PA probably in the higher
terrain...kept precip all rain. Low temps in the 30s.
.SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY NIGHT/...
Surface low should be off the New Jersey coast Tuesday morning
with a surface trough hanging west across the area. Moisture will
still be over the area but much of the forcing should be east.
Will begin with chance pops east as well as chance pops into the
area from the northwest along the trough axis. For the afternoon
expect mostly dry conditions under cloudy skies as the ridge
builds in from the west. The next storm system will move through
the central plains to the central Great Lakes Wednesday. There is
a very small chance that precip ahead of the associated warm front
moves into the western counties before dawn. Will have a slight
chance pop for the far west late Tuesday night. Otherwise rain
chances increase through the morning as a warm front/cold front
combination move across the area from the west. Will have chance
pops continuing through the afternoon. Any precip with the cold
front should move east of the area Wednesday evening however more
moisture moves in from the west overnight so will have chance to
likely pops. Thursday will continue chance pops most places and
likely pops in the snowbelt as lake enhancement likely occurs with
850mb temps down to -7C. Temps mild through Wednesday then they
drop back to near normal.
.LONG TERM /FRIDAY THROUGH MONDAY/...
Winter will have returned by friday with the airmass likely to
slowly get colder each day thru sunday. Lake effect snow showers
should occur each day but look to try and come to an end by monday
evening. Weak upper systems rotating se thru the area may also lead
to a little snow shower activity for other areas also.
No one day appears to have real heavy snowfall but in a cumulative
sense, areas in the snowbelt will likely start to see some
significant total accumulations by monday. Temps look to be about
normal friday then trend to be a little below normal for sunday and
.AVIATION /00Z Tuesday THROUGH Saturday/...
Widespread IFR/LIFR conditions will spread over entire forecast
area and linger through the overnight as low pressure...off the SE
coast...moves north. conditions will slowly improve from the west
Tuesday afternoon as high pressure moves across the upper Ohio
OUTLOOK...Non-VFR Wednesday into Friday. Rain on Wednesday will
give way to snow Wednesday night. The synoptic snow will end from
the west Thursday afternoon. Then...lake effect snow will develop
in the snowbelt east of Cleveland and continue into Friday.
NE winds with marginal sca conditions for the middle of the lake
will settle down later tonight into tue as a ridge of high pressure
shifts east across the lake. A strong low will move ne across mi
pulling a strong cold front across lake erie wednesday. South winds
should increase to 15 to 25 knots ahead of the cold front shifting
to wsw then west with frontal passage wed and increasing to 30 knots
with a possibility of 35 knot gales. Winds and waves should
gradually diminish some thu into fri as the strong low shifts
further ne away from the lakes.
Area Forecast Discussion
National Weather Service GLASGOW MT
815 PM MST Mon Jan 23 2017
.SHORT TERM...for northeast Montana...tonight through Wed...
Update: The going forecast is in good shape. The only tweak made
was to end the freezing rain advisory for Dawson, Prairie, and
Wibaux counties. Radar returns there are tapering off, a
development which is in good agreement with the HRRR forecast
model. The MDT road report also shows only minimal impacts from
any freezing rain that did fall. The remainder of the forecast was
left alone, as on and off light snow will be commonplace through
the overnight hours. Gilchrist
Previous discussion: Small mesoscale system moved east across
mainly the central zones this afternoon with snow spreading east
into Roosevelt county. further south, precipitation fell as
Freezing Drizzle from north of Circle to Sidney. This area was
moving south and models have been consistent on keeping it going
for a few hours in Dawson, Prairie and Wibaux counties.
Accumulations should be about .01-.03, enough to make untreated
roads and sidewalks slippery. A Freezing Rain Advisory is in
effect until 8 pm.
Elsewhere, system exits into North Dakota this evening. Cold Air
Advection takes places as cold air mass moves in from
Alberta/Sask. A couple of upper low, one over central Canada, the
second one is moving through the western states. Both upper lows
will merge Wednesday with the upper flow over northeast Montana
becoming northerly then. Another batch of moisture in this flow
will move through Wednesday with temperature profiles showing all
snow. Little if any accumulation is expected, so chance pops look
good for now.
Temperatures will cool for the central and eastern zones to
slightly below normal levels. TFJ
.LONG TERM...Wed night through Mon...
The long term forecast remains in excellent shape as described
below. Upper ridging will provide mainly dry weather conditions
for the end of the week and starting off the weekend before a
Pacific shortwave knocks down the ridge late in the weekend into
early next week with a return to colder temperatures to follow
that system. Maliawco
Previous Long Term Discussion...
Canadian high pressure moves across the region on Thursday with
midweek snow shower ending and cooler temperatures. Upper ridge
then pushes over the Rockies for drier weather through the end of
As a Pacific shortwave pushes into the top of the ridge over the
weekend, with warm Alberta chinook will spread south into
Montana. By early next week, cooler temperatures and the chance
for snow will return with a cold front as the Pacific shortwave
slides into the prairies. Ebert
MVFR CIGS and VFR VSBYS will prevail tonight for most locations
while LIFR ceilings linger longer over KGDV as the snowfall
gradually ends from north to south through the overnight hours.
Amendments may be needed from time to time.
Area Forecast Discussion
National Weather Service Pocatello ID
212 PM MST Mon Jan 23 2017
.SHORT TERM...Tonight through Wednesday. Complicated system
overhead currently. As indicated by models and satellite imagery,
broad upper trough remains in place over western US. Main
circulation over Pacific Ocean appears to be filling in while
circulation over OR/CA/NV has strengthened. Expect the upper low
center to reform over ID this afternoon and evening. In addition,
surface low currently located over Great Salt Lake expected to
gradually shift E/NE. Combination of these features puts much of
SE ID in cross hairs for elevated snow through tonight.
Accumulations this morning were higher than originally expected,
with snowfall rates meeting or exceeding inch/hour. Short range
models, particularly HRRR and RAP continue to show redevelopment
of moderate to heavy band of snow this evening into the overnight.
The difference between the two is where the band will be located.
Both favor orographic enhancement along the I-86 corridor between
Pocatello and Burley, but RAP slightly further west than HRRR.
Regardless, model spread including GFS, NAM, NAM experimental,
NSSL-WRF, etc all favor higher snow amounts through tonight with
8-16 inch totals somewhere between Pocatello and Burley with a
slightly smaller bullseye between Idaho Falls and the INL.
Operational NAM and GFS slightly lower in the 6-10 inch range, and
have tempered forecast snow amounts with those values. The
positioning of the low is likely to have the greatest impact with
respect to direction of the winds and orographic forcing. Have
upgraded all advisories to warnings for tonight especially
regarding potential impact for evening and morning commutes
regardless of snow amounts. Confidence remains relatively high for
timing of the bands but moderate on placement and amounts.
Complicating factor is strengthening of the winds in the
Burley/Oakley area, and in the north along the MT border. Have
left blowing snow in the forecast overnight for these areas where
winds are expected to gust over 20kts.
Upper low shifts into Plains states during the day Tuesday.
Remaining pattern Tuesday through Wednesday includes northerly
flow stacking moisture into SE highlands. Gradually cooling
temperatures increase snow ratios but deep moisture shifts east
with the low. Have kept chance precip most higher elevations near
the WY and UT borders, otherwise chances decrease toward the NW
central mountains. Increasing snow ratios will complicate matters,
but QPF amounts decrease so each 24 hour period should have
relatively low snow amounts. DMH
.LONG TERM...Wednesday night through next Monday. Development of
upper ridge is consistent in long-term models through much of the
period. We will have enough upslope component in the 850-700mb layer
to trigger some light snowfall over the Caribou Highlands and Upper
Snake Highlands. An east-west oriented trough will slide down out of
Canada on Friday, cutting off the upslope component and producing
some drying. Thus will keep PoPs low Friday through Monday. With the
passage of the upper trough, and a northerly flow in its wake,
expect to see temperatures coming below normal. Hinsberger
.AVIATION...Pessimistic TAFs for the 18Z package for most of the
terminals. Radar trends show two distinct areas of snow in play for
southeast Idaho. The first is currently over KPIH and dropping
visibility as low as 1/2 mile. The second is still over KBOI and
models show this area surging eastward this evening. NAM and BUFKIT
soundings suggest heavy and prolonged QPF associated with the second
wave lasting through 18Z. Snow could become heavy enough to
temporarily drop KBYI, KPIH, and KIDA below minimums. Additionally,
winds are expected to increase this afternoon/evening as the second
band of snow approaches southeast Idaho. Hinsberger
.HYDROLOGY...After discussion with Custer Emergency Management,
the areal flood advisory will be continued for one more day. There
has been some improvement in conditions, but concerns have shifted
to future snow melt. Therefore it has been advised that we allow
the advisory to expire tomorrow. DMH
Winter Storm Warning until 6 AM MST Tuesday for IDZ017-020>025.
Area Forecast Discussion
National Weather Service Phoenix AZ
855 PM MST Mon Jan 23 2017
The last in the recent series of Pacific storm systems will move
through the area tonight and Tuesday. The threat for rain and
mountain snow showers are forecast to linger over central and
eastern Arizona through late tonight, otherwise clearing from the
west to east is expected. A much colder and drier air-mass is
forecast to settle over the region Tuesday through Thursday,
resulting in some of the coldest low temperatures of the season
Wednesday and Thursday mornings. Mostly clear skies and slightly
warmer temperatures will return next Friday and the weekend.
As expected, the colder front that brought locally heavy rain to
parts of SE CA as now moving across South-Central AZ at this hour.
Light to moderate shower activity ahead of the front has dropped up
to 1/3 inch of rain over much of lower elevation areas of northern
Maricopa County, with up to 0.75 of an inch falling over the higher
terrain north and east of Phoenix. A final push of shower activity
is now moving through the region as the sfc cold front moves
through. Perhaps another 0.05 to 0.20 inch of rain could fall over
the lower deserts of south-central AZ before the rain ends for good
later this evening, as indicated on latest HRRR and 3km NAM model
output. Rain and snow showers will likely linger into Tuesday
morning over southern Gila County and the higher terrain of extreme
northern and eastern Maricopa County. A few inches of snow is still
expected above 6000 feet tonight and early Tuesday, with flakes
falling as low as 4000 feet. As far as the short-term forecast is
concerned, other than some adjustments to the hourly
temp/dewpoint/wind grids to better reflect current trends, inherited
forecasts are still looking good.
Clearing skies are expected tonight, but with lingering showers
forecast over the higher mountains east of Phoenix on Tuesday, namely
southern Gila County zone 24.
Tuesday through Thursday...
A much colder and drier airmass is forecast to settle over the
region Tuesday through Thursday following Mondays cold front.
This incoming airmass is the coldest so far this season, and
although not extremely cold, will be enough to drop minimum
temperatures on the lower deserts into the low to mid 30s,
possibly 28 degrees both Wednesday and Thursday mornings. Mostly
clear skies area also forecast, again with the exception of a few
lingering snow showers over the mountains east of Phoenix Tuesday
Friday through Monday...
Dry northerly flow aloft will continue to keep temperatures below
normal through the period. With mostly clear skies, night-time
temperatures on the deserts will also remain below normal, from the
middle 30s to middle 40s.
South-Central Arizona including KPHX, KIWA,and KSDL:
Modest cold front moving through metro Phoenix as of 21Z with
isolated to scattered showers and variable ceilings ranging from 4-
7 kft MSL. Higher mountains obscured. Anticipate higher ceilings and
a temporary cessation of shower activity roughly between 22Z-02Z
over the lower elevations (no break for higher terrain). Then,
scattered to numerous light showers redevelop for a few hours
(bases 5-7 kft MSL) followed by clearing after 06Z-07Z (lingering
until about 10Z over higher terrain). Surface winds will favor
westerly directions through about 10Z before trending southeast.
Southeast California/Southwest Arizona including KIPL and KBLH:
Isolated showers will continue through 03Z with areas of ceilings 6-
8 kft MSL and localized 5-7 kft MSL before clearing. Southwest and
west winds with gusts to 30 kts will continue until about 02Z-03Z
Aviation discussion not updated for amended TAFs.
Wednesday through Sunday: Weakened but broad and dry troughing will
settle over the west Wednesday keeping flow aloft westerly with low
level winds north to northwesterly but rather light. Quasi-zonal
flow will develop into the region as high pressure attempts to build
into the west and various shortwave systems ride over the ridge
flow. Temperatures initially will be well below normal but will
gradually warm during the five day period, becoming near seasonal
seasonal normal by Sunday. Humidity values will start highly
elevated with minimum RH values 30-45 percent, gradually drying
during the week and lowering into the mid to upper teens by the
weekend. One stronger storm system passing through the Four Corners
during the late week/early weekend will produce enhanced easterly
surface flow over the Mogollon Rim and northerly flow down the
Colorado River Valley, introducing breeziness and periodic gustiness
from the north and northeast for the districts.
.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.
AZ...Winter Weather Advisory above 6000 feet until 5 AM MST
Tuesday for AZZ024.
Visit us on Facebook...Twitter...and at weather.gov/phoenix
Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
755 PM EST Mon Jan 23 2017
01z water vapor and H4 RAP analysis show the deep/sharp
trough the moved through the southeastern states Sunday and
Sunday night pivoting up the eastern seaboard...and driving
a strong nor`easter low pressure system across the mid-
atlantic/Northeastern states overnight. In the wake of this
system...heights are quickly rising over the Florida
peninsula and eastern Gulf of Mexico as we transition
quickly to upper level ridging that will control our weather
through the middle of the week.
00Z KTBW sounding profile shows the atmosphere over our
heads has dried out considerably during the past 12-18
hours...with a PW value down down to around 0.7". A sharp
subsidence inversion is located around 850mb...with very dry
air/large dewpoint depression through the remainder of the
column. Still seeing some lower level moisture trapped below
this level arriving with the strong NW winds off the Gulf of
Mexico...but this moisture will also be drying out overnight
and Tuesday morning.
At the surface...The pressure gradient is still quite tight
across the region between the aforementioned low along the
eastern seaboard and high pressure over the western Gulf.
However this gradient across the peninsula and eastern Gulf
will be weakening steadily overnight...dropping from about
9mb currently...to roughly 4mb by daybreak. This drop in
gradient and loss of any CAA will really allow winds to
diminish and become less gusty during the next 12 hours.
We had seen some passing showers through the afternoon hours
driven by the CAA over the gulf...coupled with the very
impressive vorticity aloft associated with the passing
trough. Our area is now under a region of strong NVA...and
shallower moisture...which as cut off the shower development
over the eastern Gulf. Our forecast for the remainder of the
overnight and into Tuesday is now a dry one.
With the inclement weather and windy conditions exiting the
forecast...we can settle in for a much quieter day
Tuesday...highlighted by lighter winds...plenty of
sunshine...and seasonable temperatures.
Have a great Monday night everyone!
.AVIATION (24/00 through 25/00Z)...
A breezy day has turned into a breezy evening.
However...winds will be subsiding for all terminals through
the overnight and becoming less gusty. More typical 8-12kt
winds can be expected for much of the day Tuesday. Generally
VFR conditions this evening with a few patches of MVFR
stratocu moving in from the Gulf. The BKN stratocu should
end by 06Z...with prevailing VFR for the remainder of the
TAF period as skies clear during the late night and morning
Conditions still quite rough across the eastern Gulf this
evening. The Gale watch has expired...however high end small
craft advisory conditions are still exist. Wind and waves
will gradually be subsiding through the overnight hours.
Residual wave action may however take until later Tuesday
morning to fall below advisory levels. Winds and wave will
continue to subside Tuesday afternoon into Tuesday night as
high pressure builds over the region.
.Prev Discussion... /issued 247 PM EST Mon Jan 23 2017/
SHORT TERM (Tonight-Tuesday)...
A strong low pressure system will move off the mid Atlantic coast
tonight and south of New England on Tuesday. The associated cold
front has moved well east of the Florida peninsula with strong west
to northwest winds in its wake across west central and southwest
Florida with gradient winds gusting 40 to 50 mph. The gradient will
begin to relax late this afternoon and tonight as the low pulls away
from the region. Cold air advection across the coastal waters is
creating low level instability over the eastern Gulf, and combined
with U/L forcing from an approaching 50H trough...scattered low top
showers have been developing over the coastal waters and advecting
onshore. As the U/L trough pushes east of the forecast area this
evening, large scale subsidence will move over the eastern Gulf and
Florida tonight bringing an end to the shower activity with skies
becoming mostly clear.
On Tuesday, high pressure surface and aloft will build over west
central and southwest Florida with mostly clear skies and
temperatures near climatic normals. Potential will likely
remain for high surf and strong rip currents at area beaches
on Tuesday as it will take time for seas to subside.
LONG TERM (Tuesday Night - Monday)...
Models remain in good agreement with overall synoptic scale features
during this time frame so a blend will be used. At the start of the
period mid level and surface ridging will be building over the area
with pleasant dry weather and much lighter winds expected through
By late Wednesday the high will shift east into the Atlantic as
another upper level trough and cold front approach from the west.
Sufficient moisture return ahead of this next front should support a
slight chance of showers (Pops 20 percent) across the Nature Coast
by late Wednesday night, with the showers then spreading south into
the central and southern portions of the forecast area during
Thursday and Thursday night as the front moves south through the
On Friday and continuing into the first part of the upcoming weekend
cooler and drier air will advect into the region in the wake of the
front with cool dry weather with below normal temperatures expected
as surface high pressure noses in from the northwest.
During the latter part of the weekend and into early next week
embedded shortwaves moving east across the Gulf within a very strong
(140+ knot) jet aloft aligned west to east across the southeastern
states and northern Gulf coast region combined with sufficient low
level moisture and additional upper level energy moving through the
base of the eastern U.S. upper trough over the southeastern states
will likely support a good deal of clouds and chances (Pops 30 to 40
percent) for showers across the region through the period. Slightly
above normal temperatures Wednesday into early Thursday will fall
back to below normal Friday through Monday as cooler air overspreads
.Preliminary Point Temps/PoPs...
TPA 57 71 56 74 / 0 0 0 0
FMY 58 77 56 77 / 0 0 0 0
GIF 51 73 51 78 / 0 0 0 0
SRQ 60 71 54 75 / 0 0 0 0
BKV 50 69 46 77 / 0 0 0 0
SPG 59 71 59 74 / 0 0 0 0
FL...Beach Hazards Statement until 10 PM EST this evening for
Coastal Manatee-Coastal Sarasota.
High Surf Advisory until 1 PM EST Tuesday for Coastal
Charlotte-Coastal Hillsborough-Coastal Lee-Coastal
High Rip Current Risk through Tuesday evening for Coastal
Charlotte-Coastal Hillsborough-Coastal Lee-Coastal
Gulf waters...Small Craft Advisory until 4 AM EST Tuesday for Charlotte
Harbor and Pine Island Sound-Coastal waters from
Bonita Beach to Englewood FL out 20 NM-Coastal waters
from Englewood to Tarpon Springs FL out 20 NM-Coastal
waters from Tarpon Springs to Suwannee River FL out
20 NM-Tampa Bay waters-Waters from Bonita Beach to
Englewood FL out 20 to 60 NM-Waters from Englewood to
Tarpon Springs FL out 20 to 60 NM-Waters from Tarpon
Springs to Suwannee River FL out 20 to 60 NM.
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
647 PM MST Mon Jan 23 2017
Issued at 640 PM MST Mon Jan 23 2017
00z KUNR sounding showed decent support for ST running up the
Black Hills and creating areas of fog, some FZFG. Support for FZDZ
is weak, but recent looks outside suggest there might be a bit
starting to fall with KUDX scans showing some shallow returns.
Have added FZFG/FZDZ to forecast along the eastern slopes of the
Black Hills and adjacent plains.
Upstream system looks quite vigorous on water vapour and should
provide excellent lift and kill FZDZ potential overnight as -SN
overspreads CWA. 00z RAP showing impressive totals by 19z Tuesday
along the WY/SD/NE border. Will continue to reassess and
collaborate with our friends at CYS.
.SHORT TERM...(This Evening Through Tuesday Night)
Issued at 154 PM MST Mon Jan 23 2017
Vigorous impulse and associated jet streak will shift quickly
east toward the region and support strong cyclogenesis over the
Plains tonight into Tuesday. FGEN/WAA response will support
widespread snow later tonight with periods of heavy snow across
the SE third Tues. Sfc pressure falls will support a tightening
pressure gradient in a CAA regime with increasing ll flow, esp in
the lee of the Black Hills where winds are expected to be
sustained at 25 to 30 with gusts to around 45 mph Tues. This will
support areas of blowing and drifting snow across much of the SD
LL easterly flow will support fog through much of the evening
over western SD, esp in the foothills region of the Black Hills.
UVM and WAA/FGEN will spread NE and support developing snow over
the far SW this evening, spread NE through the night. Long period
overlap of pos theta-e adv at the base of steep mid level lapse
rates centered in the DGZ will support a period of moderate to
heavy snowfall rates across scentral SD Tues, esp with a brief mid
level closed circulation. Potential CSI banding will also be an
issue over scentral SD further enhancing snowfall. Hence, this is
where the heaviest snowfall is expected with 6-10 inches likely,
some places could see around a foot easily, esp from Wanblee to
Winner. Snowfall amounts will drop to the west with adv criteria,
save for the northern Black Hills where some weak upslope
enhancement will support slightly higher totals around warning
criteria. Winds will be of concern on the SD plains, esp east and
south of the Black Hills where blowing and drifting snow will be a
concern. Given snow amounts and winds, have decided to upgrade
areas to a warning and issue an adv elsewhere.
Snow will quickly tapper off Tues eve from west to east, although
blowing snow will be an issue through much of the night, thus the
reason for the longer duration of the warning/adv through Tue
night on the SD plains.
.LONG TERM...(Wednesday Through Monday)
Issued at 154 PM MST Mon Jan 23 2017
Low pressure moves quickly away from the region by
Wednesday morning. However, the broad upper trough will remain
across the region Wednesday, with a chance for mostly upslope snow
showers over far northeast WY and the northern Black Hills area
through Wednesday into Thursday as upper level energy slides through
the area. Temperatures will be below average Wednesday and Thursday.
The upper trough will move out of the area toward the end of the
week with a ridge building over the western CONUS. Some moderation
to temperatures is expected through the weekend along with dry
.AVIATION...(For the 00Z TAFS Through 00Z Tuesday Evening)
Issued At 413 PM MST Mon Jan 23 2017
Deck of IFR ST from far southeast MT to eastern slopes of the
Black Hills to central SD will sink south/southwest tonight
creating areas LIFR ST/FG. A storm system over UT will spread
deteriorating conditions across the rest of the CWA tonight with
-SN developing late evening and continuing through the period as
it spreads east. Widespread IFR conditions with areas LIFR
expected Tuesday due to SN. Gusty winds on the SD plains will
produce areas BLSN.
SD...Winter Storm Warning from 11 PM this evening to 11 PM MST
Tuesday for SDZ024.
Winter Storm Warning from 2 AM MST /3 AM CST/ Tuesday to 5 AM
MST /6 AM CST/ Wednesday for SDZ032-043-044-046-047-049.
Winter Storm Warning from 11 PM this evening to 5 AM MST
Wednesday for SDZ027-030-031-041-042-073.
Winter Weather Advisory from 11 PM this evening to 11 PM MST
Tuesday for SDZ029.
Winter Weather Advisory from 2 AM Tuesday to 5 AM MST Wednesday
Winter Weather Advisory from 11 PM this evening to 5 AM MST
Wednesday for SDZ025-026-028-072-074.
WY...Winter Storm Warning from 11 PM this evening to 11 PM MST
Tuesday for WYZ057.
Winter Weather Advisory from 11 PM this evening to 11 PM MST
Tuesday for WYZ055-056-058.
Winter Weather Advisory from 2 AM Tuesday to 5 AM MST Wednesday
Area Forecast Discussion
National Weather Service Las Vegas NV
238 PM PST Mon Jan 23 2017
.SYNOPSIS...Scattered to numerous rain showers and snow showers
will dissipate overnight Isolated snow showers are possible over the
higher terrain Tuesday. Drier, cool and locally breezy conditions
are then in store for Wednesday and beyond.
.SHORT TERM...Through Tuesday night...
Plan is to let the current Winter Weather, Wind and Flood products
run there course through 4 pm. Looking at snow rates and wind speeds
diminishing quickly this evening.
Instability showers along with a few embedded thunderstorms under
cold air aloft will last into the evening before dissipating
overnight. Current radar data shows a broken line of showers from SW
Utah west toward Beatty. 18z guidance and latest 20Z HRRR still
insisting this broken line of showers will move southeast out of
Lincoln/Nye Counties across Clark/northern Mohave Counties this
evening and into the overnight hours.
Region will lie under a broad cyclonic flow on Tuesday with isolated
instability showers developing primarily over the higher terrain of
Mohave, Clark, Lincoln Counties as well as the Southern Sierra.
.LONG TERM...Wednesday through Monday. Looks like an essentially dry
forecast through the period except for slight chances of showers on
the higher terrain along the northern fringes of our CWA Thursday
afternoon and Thursday night. The main concern looks like strong
north winds down the Colorado River Valley Friday through Sunday. A
trough digging down the east side of the West Coast ridge is
forecast to swing southward through our area Friday, with a strong
surface high pressure system building over the Great Basin in its
wake. This will increase surface pressure gradients to 10-14 mb from
Ely to Needles, suggesting strong northerly winds down the Colorado
River Valley at least Friday and Saturday, and perhaps beyond.
Otherwise, temperatures should remain below normal areawide at least
through Saturday, with models disagreeing whether or not to warm
things up Sunday or Monday.
.AVIATION...For McCarran...Showers look like they will stay
confined to the higher terrain west of the valley which will obscure
the higher terrain. There are indications of a line of showers
moving from north to south across the valley between 7 pm this
evening and 2 am Tuesday morning. Moderate confidence in that
occurring so mentioning VCSH during that time. Cigs should remain
above 6 kft this afternoon and overnight but could lower to 4 kft if
showers materialize. Southwest winds around 20 knots and gusting 30
knots into early evening before speeds start decreasing. Wind
direction could swing to a northwest direction with any showers
this evening and hold from the northwest through Tuesday.
For the rest of southern Nevada...northwest Arizona...and southeast
California...Scattered to numerous showers are expected today
into this evening mainly over Mohave County and southeast California
with mountains frequently obscured. Cigs 4-6 kft will be common
dropping to 2-3 kft at times. Southwest winds 15-25 knots gusting 30-
45 knots decreasing this evening and becoming west to northwest
overnight through Tuesday. Any residual shower activity on Tuesday
will be confined to the higher terrain of southern Nevada, northwest
Arizona and the southern Sierra.
.Climate... Bishop, CA has so far (including today) received 5.23
inches of rain. The normal yearly total is 5.18 inches. This marks
the first climate station in the United States that has surpassed
their entire annual precipitation total. This is also the second
wettest January on record behind the 8.93 inches that fell in
Bishop has also recorded more rainfall this year then the yearly
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
rain or snow amounts through this evening as a storm moves through
For more forecast information...see us on our webpage:
http://weather.gov/lasvegas or follow us on Facebook and Twitter