Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/02/21
AREA FORECAST DISCUSSION
National Weather Service Albany NY
1009 PM EST Mon Feb 1 2021
.SYNOPSIS...
A coastal storm will bring a heavy snowfall and blustery
conditions to eastern New York and western New England tonight into
Tuesday. The storm will be slow to exit our region as light snow and
snow showers are expected Tuesday night into Wednesday evening.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
Winter Storm Warning: Dutchess, Ulster and Litchfield Counties
until 4 pm Tuesday
Winter Storm Warning: Eastern Catskills, Capital District,
Mohawk Valley, Schoharie Valley, Helderbergs, northern and
central Taconics, northern mid Hudson Valley, Hamilton and
northern Warren Counties, southern VT and the Berkshires until 7
pm Tuesday
Winter Weather Advisory: Washington, northern Saratoga, northern
Herkimer and southeast Warren counties until 7 pm Tuesday
As of 1005 PM EST...Nor`easter is around 995 hPa based on the
latest RAP MSLP analysis and is east/southeast of southern NJ
slowly drifting to the east to northeast. The dry slot in the
water vapor imagery has punched into eastern CT and RI. The ALY
forecast area continues to be in the comma head of the cyclone
with an intense mesoscale snow band due to the strong low-level
/mid-level FGEN yielding 1-3" per hr snow rates across the
eastern Catskills, northern mid Hudson Valley, central and
northern Taconics, the eastern Capital Region and southern VT.
The snow shield has finally expanded into the west-central
Mohawk Valley, Saratoga Region, and the KGFL area. These
locations should see the snow continue to pivot in as the band
lifts north/northwest. Some downsloping off the south-central
Greens may continue to shadow the snow amounts some off the
upper Hudson Valley as the anomalous easterly H8500 LLJ jet
impacts the region which can be seen nicely on the KENX VWP.
Strong upslope continues across the eastern Catskills and
Helderbergs with the band as snow totals up to 17.0" have come
in from Tannersville. The latest hourly snow depth change from
the NYS Mesonet was 2.7"!. Many locations have received 10-16"
in the mid Hudson Valley, southern Taconics, southern Berkshires
and Litchfield County Connecticut. An additional 2-4" is
possible in the mid Hudson Valley/Litchfield County CT before
the snow diminishes with the Pivoting band per the CSTAR
research. The eastern Catskills could get additional around
8-12" and some snow totals may reach 24-30". Spotty higher
amounts. The Capital Region may get another 3-6" with amounts
of 2-6" coming in so far, as totals in the 6-12" are possible
still. Southern VT in the Berkshires will be in the 8-18" range
with the lower amounts in the valley areas of VT.
The headlines still look good, as the snow continues to pivot
into the central-western Mohawk Valley with 6-12" possible. The
eastern Adirondacks could still get 6-10" overnight with 4-8"
amounts in the Upper Hudson Valley.
Snowfall ratios will generally be near climatology (10-13:1) as
per coordination with WPC WWD/QPF branches, there may be a
minimum just north of the Capital Region and into Glens Falls
and Washington County. Then into the Dacks and Catskills,
expectations are additional upslope enhancement so the current
headlines look good at this time. Lows generally into the 20s.
Wind gusts of 25-35 mph will continues with those higher values
into the higher terrain. This will result in some blowing and
drifting of the snow into the morning.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY/...
The upper low over West Virginia will eventually catch up the
near quasi-stationary surface low just to the east of coastal NJ
into Tuesday. Deformation/TROWAL axis appears to be setting up
over western areas or near I81 corridor as additional episodic
light snow/snow showers evolve to the east. As drier air is
expected aloft, some mix may occur to the southeast of Albany,
however, not enough confidence at this time per the HREF
probabilities. Temperatures Tuesday afternoon appear anomalously
high on the GFS-MOS as we followed more closely to the NBM/MET
guidance.
Tuesday night, a pivotal deformation band is expected somewhere
over eastern upstate NY. However, vertically stacked low just
off the Jersey Shore will become occluded so additional light
snow and/or snow showers with upslope areas susceptible for
additional light snow accumulations. Winds will remain
problematic as well with some blowing and drifting of the snow
with mixing layer heights still expected to be at or above 2k
feet where 30+kts reside. Overnight lows into the teens and
lower half of the 20s.
Wednesday, a slow transitional day is expected as either the
upper low lingers over Cape Cod or moves northeastward into the
Gulf of Maine. This will determine where the deformation axis of
snow will persist or impact. As some upslope areas are expected
to still experience some additional snow per the Froude number
less than 0.5, we will also need to watch the potential for
Mohawk-Hudson convergence that could evolve through the day.
Additional QPF appears to be at or below two-tenths of an inch
as snow ratios will be near climatology. High temperatures into
the lower 30s for the Hudson River Valley and mostly 20s
elsewhere.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
The upper-level low will slowly push eastward out of the area
Wednesday night with any lingering snow showers ending. Partial
clearing is expected as well along with a decrease in wind speeds.
Low temperatures will dip into the teens to lower 20s.
Thursday is shaping up to be a rather nice day as upper-level
ridging and surface high pressure builds overhead. A dry day is
expected under a partly to mostly sunny sky. High temperatures will
range from the mid-20s in the higher elevations to the 30s in the
valleys.
The next system will move across our region late Thursday night
through Friday. The track of the low will be across the Great Lakes
into Hudson Bay. The track along with mild enough air in the
boundary layer will support a rain/snow mix across some valley areas
with mostly all snow across the higher terrain. Lows Thursday night
will be mainly in the teens with highs Friday mostly in the 30s.
Some lake-effect snow showers will be possible in the wake of this
system for Friday night and Saturday before another storm system may
approach Sunday into Monday. The evolution of this system will be
highly dependent on the interaction between northern and southern
stream pieces of upper-level energy, which are highly uncertain this
far out. High temperatures over the weekend will be in the 20s and
30s and in the teens and 20s on Monday. Lows each night mainly in
the single digits and/or teens.
&&
.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
The peak of the winter storm impacts with respect to
accumulating snow and low vsby expected to occur 00-06Z. During
this timeframe, LIFR vsby will be common at KPOU/KPSF/KALB with
heavy snow (1/4SM vsby or less) possible at times. Snowfall
rates of 1-2 inches per hour are possible. KGFL, on the
periphery of the storm, has yet to see snow and it may be toward
closer to 02Z before cigs/vsby fall to IFR.
The heaviest snow is expected to shift out of KALB/KPOU/KPSF after
06Z, but IFR vsby expected to prevail at all terminals with a
mixture of snow and blowing snow. Downsloping winds may briefly
result in improving cigs/vsby at KALB/KPSF/KGFL, although confidence
is low on this scenario. Snow showers expected to become more spotty
during the day Tuesday as a midlevel dry slot kicks in, with
conditions improving to MVFR, but light accumulations will likely
continue.
Winds will be from the north (except northeast at KPSF) at 10-15 kt
with gusts of 20-25 kt at times through the TAF period. Low level
wind shear conditions are forecast at KPSF through 12Z Tuesday with
45-50 kt winds at 2kft AGL.
Outlook...
Tuesday Night: High Operational Impact. Likely SN.
Wednesday: Moderate Operational Impact. Breezy. Chance of SHSN.
Wednesday Night: No Operational Impact. NO SIG WX.
Thursday: No Operational Impact. NO SIG WX.
Thursday Night: Low Operational Impact. Slight Chance of SN.
Friday: Moderate Operational Impact. Likely RA...SN.
Friday Night: Low Operational Impact. Slight Chance of SN.
Saturday: No Operational Impact. NO SIG WX.
&&
.HYDROLOGY...
No widespread hydrological issues are expected for the week.
A coastal storm will bring accumulating snowfall to the area
into Tuesday. The storm will be slow to move away from the
region so intermittent light snow is expected Tuesday night into
Wednesday.
Temperatures will be seasonable cold for early February into
mid week where ice has built up on rivers and streams, then
temperatures are expected to moderate by the end of the week
which may result in some snow melt. A low pressure system will
impact the region by the end of the week bringing snow and rain
to the area.
For details on specific area rivers and lakes, including
observed and forecast river stages and lake elevations, please
visit the Advanced Hydrologic Prediction Service /AHPS/ graphs
on our website.
&&
.ALY WATCHES/WARNINGS/ADVISORIES...
CT...Winter Storm Warning until 4 PM EST Tuesday for CTZ001-013.
NY...Winter Storm Warning until 7 PM EST Tuesday for NYZ033-038>040-
042-047>054-058>061-063-082.
Winter Storm Warning until 4 PM EST Tuesday for NYZ064>066.
Winter Weather Advisory until 7 PM EST Tuesday for NYZ032-041-
043-083-084.
MA...Winter Storm Warning until 7 PM EST Tuesday for MAZ001-025.
VT...Winter Storm Warning until 7 PM EST Tuesday for VTZ013>015.
&&
$$
SYNOPSIS...BGM/Wasula
NEAR TERM...BGM/Wasula
SHORT TERM...BGM
LONG TERM...Rathbun
AVIATION...Thompson
HYDROLOGY...IAA/BGM
Area Forecast Discussion
National Weather Service La Crosse WI
955 PM CST Mon Feb 1 2021
.SHORT TERM...(Tonight and Wednesday)
Issued at 200 PM CST Mon Feb 1 2021
Clouds the main forecast concern for the next few days with stubborn
low level deck holding across the region. RAP/NAM doing the best job
with the low saturation currently - matching up fairly well with
fog/stratus vsby satellite imagery. How quickly the clouds will
break up ahead of approaching sfc high is the main question.
The NAM slowly erodes the western edge of the deck through the
night, holding it along the mississippi river by 12z. The gradually
dissipation continues through the day as sfc high moves overhead. The
RAP is not as aggressive, nothing really getting into a lot of
clearing til later in the day Tue. Mostly, this is in line with when
the upper level trough axis starts to press in from the west.
Confidence not high in how this plays out, but will lean toward
holding clouds longer - more reasonable for setup/time of the year.
If you are a groundhog believer - hold out hope those low clouds do
stick around for no shadow and an earlier spring.
As for temps, the relatively mild start to Feb will continue into
mid week with highs mostly in the lower 30s (normals in the upper
20s).
.LONG TERM...(Wednesday night through Monday)
Issued at 200 PM CST Mon Feb 1 2021
WINTER STORM: Wed night-Thu night ******************
Upper level shortwave still on track to drop from western Canada,
across the northern plains, and through the Upper Mississippi River
Valley Thu/Thu night. EC/GFS are a bit more south and elongated with
this feature now, and bit more punchy. 01.12z NAM a tad faster than
the GFS/EC but packs a similar punch. Debatable as to whether there
is some influence from bits of energy in the southern stream of the
upper level flow. In addition, some hints of 300 mb jet support on
Thu, with some QG convergence in the 700:300 mb layer leading the
shortwave across the region. Good frontogenetic forcing along the
associated cold front, with hints at secondary banding in the
600:700mb layer post the front (deformation region). Confident that
widespread pcpn will occur, with questions on amounts and ptype.
Looks like a quick hitter though, with the bulk of accumulations
coming in a 12 hour window at any particular location.
PTYPE: strong warming ahead of the system, with 850 mb +1 to 3 C.
West-east running x-sections and Bufkit soundings show fairly
uniform warming to the sfc though - which suggests more of a
rain/snow question rather than a warm layer/melting-partial melting
and freezing rain-sleet question. Not ruling out a short period of
wintry mix at this time though - a lot of finer details to sort out
as we near Thu. In addition, NAM bufkit soundings suggest there
could be a short window of freezing drizzle preceding the heart of
the storm (lack of ice in the cloud). Again, something else to
consider but not clear cut yet.
SNOW AMOUNTS: latest COBB output and various GEFS Plumes and EC
ensemble data all favoring amounts from 1-3", 2-4" with minimal if
any icing (at this time). Looks like a reasonable place to start.
DGZ generally under 100 mb with little threat for inch per hour
rates at this time.
WINDS: tight pressure gradient post the cold front will ramp up the
winds for Thu afternoon/night. GFS the more robust of the models at
this time, suggesting wind gusts punching north of 40 mph. EC
ensembles trending closer to 30 while the NAM is a touch less. Could
be a significant factor with a threat for blowing/drifting snow -
dependent on how just much snow falls - and how wet it is.
HEADLINES: think Winter Weather Advisories could/will be needed for
that mix of accumulating snow, blowing and drifting, along with some
wintry mix for good measure. Despite potentially low end amounts of
snow for headlines, the variety of impactful winter weather would
certainly suffice.
BITTER COLD: Sat-Early Next Week *******************
GFS/EC have been in good agreement with dropping a slug of arctic
air southward from Canada down across the upper mississippi river
valley this weekend, hanging around into the start of the new work
week.
The GFS had been the more robust of the models, suggesting -30 C 850
mb air would work this far south. Previous EC runs were not as
aggressive, but they have been trending this way, with latest
deterministic going as cold at -32 C at 850 mb. Good support from
ensemble members in both models, although the deterministic GFS
continues to be the coldest of all its members. Still, -20 F and
colder lows gaining more support, especially for Mon morning.
Depending on timing of other features, winds will also be a factor,
Suspect wind chill advisories will be needed for some locations Sun-
Tue, with values dropping into the lower 30s below zero possible (if
not probable).
&&
.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 955 PM CST Mon Feb 1 2021
IFR to LIFR ceilings are expected through Tuesday morning at KRST,
with MVFR ceilings at KLSE. Some improvement to ceilings is
possible by afternoon at both TAF sites.
Surface high pressure ridge continues to push into the area tonight,
bringing light northerly winds and relatively quiet weather.
However, MVFR/IFR stratus continues to remain trapped under a low-
level temperature inversion, with plenty of additional stratus
upstream. Guidance has continued to trend later with the break up of
these clouds Tuesday, though there are still hints that it might try
to break apart by afternoon as the surface ridge axis passes
overhead and winds turn to southeasterly. That said, there are quite
a few clouds on the back side of the ridge at present, so confidence
is low that this will occur and will continue to maintain MVFR
stratus through the afternoon. There are signals that fog may
develop Tuesday evening/night in the southerly flow behind the
departing ridge, but opted not to include this in the TAFs until
confidence increases.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...Rieck
LONG TERM....Rieck
AVIATION...Lee
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
949 PM CST Mon Feb 1 2021
.UPDATE...
Issued at 945 PM CST Mon Feb 1 2021
Dense Fog Advisory appears on track, though there are some
interesting trends from the HRRR regarding the timing of improving
conditions Tue AM.
Dense fog is in place across all but the far W and S tiers of
counties, but GOES-16 night RGB and area METARs shows steady
expansion over past few hrs, so even these areas should get in on
the "action" by midnight. Expect widespread 1/4 to 1/2 mile
visibility thru at least midnight. After midnight, exact details
become a bit more unclear, esp w/ regards to S extent of fog, due
to recent trends from the HRRR. Starting with the 22Z run, and
continuing in subsequent runs since then, the HRRR has been
bringing an end to the dense fog from S to N much sooner, perhaps
even as far N as Hwy 6 by dawn per latest runs. However, with fog
still expanding and no real change in sfc conditions (i.e. wind
speed/dir) expected overnight, not sure I buy this trend just yet.
The gap in stratus/fog noted just E of Hwy 81 has been filling
over past 30-90 min, and the HRRR is not adequately picking up on
this. Also, other data like RAP, SREF, new 00Z HREF, and EXPHRRR,
all keep dense fog conditions in place across all but far S/SE
through at least mid- morning. Thus, not making any changes to
headline, but will brief incoming mid shift on latest HRRR trends.
&&
.DISCUSSION...(This evening through Monday)
Issued at 507 PM CST Mon Feb 1 2021
General overview of the entire 7-day forecast:
Apologize for the later discussion, as today has admittedly been
a challenge trying to juggle/assess focus short-term dense fog
concern, mid-term wintry precipitation concerns (mainly Wed night-
Thurs), and long-term (mainly weekend) cold air concerns including
perhaps our very first true flirtation with Advisory /near-
Advisory wind chills this season, at least within northern parts
of the CWA.
Quick look at the current/recent weather scene as of 430 PM:
What a big contrast in weather today from much of
western/southwestern CWA which saw quite a bit of sunshine (at
least earlier before high clouds increased) and temps reaching
well into the 30s/40s, versus much of our central/eastern counties
that remained "socked in" under low stratus an/or fog essentially
all day with temps not escaping the 20s. In fact, not only did
some places not only never let go of fog in general, but they
essentially never even let go of DENSE fog, which even in winter
is fairly rare to keep around through the entire daylight cycle.
In the mid-upper levels, you`d never know we had tricky issues
going on down low, because all looks quiet locally thanks to broad
ridging dominating the western CONUS, other than the
aforementioned high cirrus spilling over the top (that half our
CWA can`t even see anyway because of all the low stuff/grunge).
Wind-wise, no big issues as afternoon breezes have picked up to
only around 10 MPH from the south-southeast.
Now looking ahead forecast-wise and briefly covering things in
mainly chronological order...
This evening-Tuesday daytime (how widespread is dense fog?):
Clearly fog (technically freezing fog) and how dense it becomes is
the paramount issue. In short, have the entire CWA in a Dense Fog
Advisory through Noon Tuesday, with eastern areas (which have been
in one throughout the day) just continuing on via extension- in-
time, while western areas will officially kick in at 9 PM (for
now, but would not be surprised to see some spots need put in
effect a bit sooner depending on trends as night falls). While
not all areas will see truly dense fog through the ENTIRE run of
the valid Advisory, felt that enough areas would see fog issues
for enough time to justify the Advisory and let later shifts
possibly drop some areas and/or cancel sooner if necessary. But if
the latest HRRR is onto anything (and it seemed to perform fairly
well last night-today) then most of our CWA will probably get
"socked in" at some point overnight into Tues AM, with perhaps our
far southwestern counties (Rooks/Osborne) perhaps being among the
"least-justified" to be in a long-fuse Advisory compared to other
areas. Time will tell, but odds are high that more of the CWA
experiences dense to near-dense fog overnight than those areas
that do not. Low temps mainly somewhere in the 20s, as clouds of
varying heights should keep places from dropping as cold as last
night. Tuesday daytime will surely be another battle with fog and
how quickly it dissipates, and like today not even sure the noon
expiration time will necessarily cut it, especially near/north of
I-80. Daytime high temps are a challenge, and if anything were
nudged down slightly (maybe not enough), but for now aiming most
of the CWA mid-upper 30s with some 40s around the far
southern/western fringes.
Tues night-Wednesday:
Did not get "cute" with details, but blanketed the evening through
mid-morning hours with a generic "areas of fog". Based on early
HRRR visibility progs though, dense fog should not be as pervasive
as tonight, and could in theory improve from southwest-to-
northeast as the night wears on and breezes turn a bit more
southwesterly. Plenty of uncertainty here though, and we really
need to take fog "one night at a time". Temp-wise, Wednesday will
"try" to be the overall-warmest day of the week, but so much will
depend on cloud trends and obviously the incessant cooling effect
of lingering snow cover. For now though, have northern areas
climbing to around 40 and far southern/southwest areas around 50.
Wednesday night-Thursday:
Did not dive into details much here, but the bottom line is that
chances are increasing for a quick hit of wintry weather, mainly
in the midnight-noon time frame. While this BY NO MEANS looks like
the "major winter storm" that it appeared in "model fantasyland"
about 4-5 days ago, various models (ECMWF/GFS/NAM) are
increasingly keying in on a quick-hit of initially mixed precip
(anywhere from rain/light freezing rain/sleet) quickly
transitioning to snow before ending from northwest to southeast.
PoPs have been raised a bit (perhaps not enough) and now have
around 1" of snow accumulation potential north of I-80, with
lesser amounts farther south (especially KS). The bottom line is
that this may not be a "zero impact" event despite limited
amounts, as there could be a period of blowing snow thanks to
northwesterly gusts 30+ MPH, and we could be looking at a "flash
freeze" of any liquid precip that falls early on in the event.
Definitely a period to keep an eye on despite the quick-hitting
nature of it. High temps Thursday only aimed upper 20s to low 30s
most areas, so surely colder than Wednesday.
Friday:
Fairly high confidence in a dry day here although could foresee
some flurries around in the presence of weak west- northwest flow
waves. At least for now, forecast reflects a slight "warm up" back
into the 30s most areas/40s south and west.
Saturday-Sunday:
Plenty of time for details to change, but another trough diving
down across the central CONUS looks to bring our coldest air of
the winter so far, with highs currently aimed mainly teens to low
20s and lows single digits both above/below zero. Saturday night
could feature our first true chance for Wind Chill Advisory values
around -20, especially north. Forecast is currently mostly dry,
but some slight snow chances are now in for Saturday which might
need increased per especially latest ECMWF.
Monday:
CONSIDERABLE uncertainty at this time range, but perhaps a slight
modification in temps with highs trying to get back in the 20s
most areas/30s southwest. Also dry for now, but with west-
northwest flow around at least some "sneaky" flurries/light snow
chances cannot be ruled out.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Wednesday)
Issued at 550 PM CST Mon Feb 1 2021
Significant wx: Around 18 hrs of IFR/LIFR VSBYs and CIGs
Tonight: Conditions never improved much at GRI and latest obs and
satellite show fog/stratus already worsening and expanding W. So
GRI is likely beginning what looks to be about 18 hrs of 1/4sm and
CIGs around 200 ft or less. EAR is currently on the edge, but with
the expansion to the W this eve, expect rapidly deteriorating
conditions to LIFR over the next 1-3 hrs. Wind will be lgt out of
the SE for both sites. Confidence: High.
Tuesday: Model data is in pretty good agreement that any
meaningful improvement to conditions will probably not occur until
close to midday. That`s when at least VSBYs should improve to
around 1-2sm, though CIGs will remain LIFR for a few more hrs.
Perhaps further improvement arrives by late aftn (best chc at
EAR), but exactly how far the fog/stratus errodes remains
uncertain. It`s possible both sites could see another round of
issues Tue eve-night. Confidence: Medium
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...Dense Fog Advisory until noon CST Tuesday for NEZ039>041-046>049-
060>064-072>077-082>087.
KS...Dense Fog Advisory until noon CST Tuesday for KSZ005>007-017>019.
&&
$$
UPDATE...Thies
DISCUSSION...Pfannkuch
AVIATION...Thies
Area Forecast Discussion
National Weather Service Jacksonville FL
900 PM EST Mon Feb 1 2021
...COLD AND BLUSTERY TONIGHT WITH WINDS CHILLS IN THE 20S TOMORROW
MORNING...
...GALE FORCE GUSTS OVER THE COASTAL WATERS...
.UPDATE...
A strong pressure gradient continued this evening between a
strong surface low offshore of New England and a ridge settling
southward across the Mid-West. Aloft, an upper level trough was
still deepening along the US Atlantic Coast, which will continue
to deepen the surface low near New England and keep a cold, breezy
weather regime in place across the local area through Tuesday.
Cloudy skies will continue tonight with wind gusts 15-20 mph well
inland to 25-35 mph at times near the Atlantic coast due to about
a 4-5 mb pressure gradient in place.
The combination of a cold low level airmass funneling over the
local area and strong winds will create wind chills in the 20s
tomorrow morning, which meets wind chill criteria across NE
Florida where a wind chill advisory remains in effect. Recent
guidance trended a tad warmer with lows tonight due to lingering
clouds with minimum temps ranging in the lower 30s inland to
mid/upper 30s toward the coast. A few inland locations across SE
GA (west of Highway 301) and NE FL including the Suwannee River
Valley may briefly reach freezing around sunrise.
Cloud cover will gradually break up through early afternoon after
sunrise Tue, with more peaks of sunshine Tue afternoon but a
continuation of gusty NW winds and below normal temps with highs
only in the 50s (upper 40s for max temps possible for some areas near
Altamaha River basin). A more widespread light inland freeze is
expected Tue night with less wind and a deeper depth of cold air
across the area.
&&
.MARINE...
Gusts to gale force will impact the coastal waters tonight through
Tuesday. Adjust combined seas down by 1 ft this evening in the
forecast based on obs with offshore flow, otherwise forecast on
track.
Rip Currents: Moderate risk.
&&
.PREV DISCUSSION [633 PM EST]...
.NEAR TERM [Tonight through Tuesday]...Strong cold air advection
continues as intense low pressure off the NJ coast continues to
deepen. A tight pressure gradient will continue the gusty northwest
winds overnight. Strong winds will combine with temperatures in
the low/mid 30s tonight to produce wind chill temperatures in the
mid 20s. Have issued a wind chill advisory for all of ne Fl as
criteria(25F) will be reached late tonight and early Tuesday
morning. A light freeze is possible in se Ga...with temperatures
in the mid 30s across ne Fl. Low wraparound clouds will continue
over the area tonight with models showing clearing skies Tuesday
morning. Blustery conditions will continue on Tuesday with highs
only reaching the lower 50s.
.SHORT TERM [Tuesday night through Thursday night]...Tuesday night
will be another cold night with winds staying up as the pressure
gradient remains tight. A light brief freeze will be possible
over se Ga and inland NE Fl but will hold off on a freeze watch
as freezing temperatures and duration will be marginal. Winds
chills will again drop into the 20s. Dry and cold conditions again
for Wednesday as nw winds start to ease with below normal temperatures.
Winds will drop off Wednesday night allowing for good radiational
cooling. Frost and a light inland freeze expected as surface high
pressure settles over the area. Thursday will see a warming trend
as the high shifts to our se and winds become sw. Temperatures
will return to normal levels.
.LONG TERM [Friday Through Monday]...Models in much better
agreement during the extended period showing a cold front with
rain and possibly thunder Friday and Saturday. Clearing for
Sunday and Monday as high pressure builds in from the nw with a
drier and colder airmass.
.AVIATION...
[Through 00Z Wednesday]
Low stratus with bases 3-4 kft covered the terminals this evening
under brisk NW winds 12-15 kts with consistent gusts near 25 kts.
Potential for MVFR restrictions tonight at all terminals as
stratus deck lowers with airmass cooling under continued gusty NW
winds. Favored HRRR and NBM guidance based on better initialization
with low stratus deck and both models advertised gradual improvement
in low clouds at SSI by 12z with improvement southward toward
JAX/VQQ/CRG through 14z then GNV/SGJ through 16z as drier air
trails passage of 925-850 mb troughs. Prevailing VFR conditions
are expected by 18z under a continuation of blustery NW winds near
15 kts with gusts near 25 kts. Winds will gradually decouple into
tomorrow evening under VFR conditions.
.FIRE WEATHER...Cold and breezy conditions will continue through
Wednesday. Dispersions will be high on Tuesday and minimum RH
values will be near critical values Wednesday afternoon.
&&
.PRELIMINARY POINT TEMPS/POPS...
AMG 32 51 30 53 28 / 0 0 0 0 0
SSI 36 53 33 54 35 / 0 0 0 0 0
JAX 35 53 33 56 33 / 0 0 0 0 0
SGJ 36 53 35 56 36 / 0 0 0 0 0
GNV 33 53 32 57 29 / 0 0 0 0 0
OCF 34 55 32 59 30 / 0 0 0 0 0
&&
.JAX WATCHES/WARNINGS/ADVISORIES...
FL...Wind Chill Advisory from 4 AM to 9 AM EST Tuesday for Baker-
Bradford-Central Marion-Clay-Coastal Duval-Coastal Flagler-
Coastal Nassau-Coastal St. Johns-Eastern Alachua-Eastern
Marion-Gilchrist-Hamilton-Inland Duval-Inland Flagler-
Inland Nassau-Inland St. Johns-Northern Columbia-Putnam-
Southern Columbia-Suwannee-Union-Western Alachua-Western
Marion.
GA...None.
AM...Small Craft Advisory from 4 AM to 11 AM EST Wednesday for Waters
from Altamaha Sound GA to Fernandina Beach FL from 20 to 60
NM-Waters from Fernandina Beach to St. Augustine FL from 20
to 60 NM-Waters from St. Augustine to Flagler Beach FL from
20 to 60 NM.
Gale Warning until 4 AM EST Wednesday for Waters from Altamaha
Sound GA to Fernandina Beach FL from 20 to 60 NM-Waters
from Fernandina Beach to St. Augustine FL from 20 to 60 NM-
Waters from St. Augustine to Flagler Beach FL from 20 to 60
NM.
Small Craft Advisory until 8 AM EST Wednesday for Coastal waters
from Altamaha Sound to Fernandina Beach FL out 20 NM-
Coastal waters from Fernandina Beach to St. Augustine FL
out 20 NM-Coastal waters from St. Augustine to Flagler
Beach FL out 20 NM.
&&
Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
933 PM CST Mon Feb 1 2021
.UPDATE...
Issued at 933 PM CST Mon Feb 1 2021
A dense fog advisory is in place across parts of swrn and ncntl
Nebraska overnight. Although conditions are okay right now,
dry air and weak winds aloft, strong radiational cooling and
reasonable moisture at the low levels should be favorable for the
formation of dense fog.
The fog forecast follows the short term model blend which is
consistent with most of the rapid refresh and mesoscale fog
forecasting models.
&&
.SHORT TERM...(This evening through Tuesday night)
Issued at 215 PM CST Mon Feb 1 2021
Concern tonight is again the potential for fog. Stratus deck is
slowly eroding to the east, but slower than the models anticipated
and areas of fog continue along the immediate edge of the stratus
from Boyd south through Wheeler county. Time lagged HRRR and RAP
slowly work the stratus and fog back to the west tonight. This seems
reasonable as south winds advect warmer and relatively moist air
northward from KS across remaining snowpack. We`ll have to again
watch for the possibility of dense fog on the immediate west edge of
the stratus, much like we saw this morning. Will pass this concern
along to the incoming evening shift.
A leeward surface trough will begin to deepen Tuesday from southwest
SD to eastern CO. South winds will continue across much of the
Central Plains to the east of the surface trough. The combination of
south winds and remaining snowpack will likely help the lower
stratus deck and fog to linger through much of the morning, then
slowly erode to the east during the afternoon. Feel that areas
around Butte/O`Neill/Bartlett won`t see much clearing with clouds
possibly lingering all day. Will adjust temperatures accordingly for
those areas. For areas across western Nebraska where snowpack has
eroded expect a very mild day. H85 temps approach 12C across far
western Nebraska, and should see highs reach into the lower 60s and
mid 60s where no snow cover exists.
.LONG TERM...(Wednesday through Monday)
Issued at 215 PM CST Mon Feb 1 2021
On Wednesday, a potent shortwave trough will be digging into the
northern Rockies. Surface low pressure will deepen across eastern CO
ahead of this feature, with an inverted surface trough extending
northeast from the low into western Nebraska and central SD. Lift
associated with the shortwave will overspread the area Wednesday
night. Meanwhile the surface low will migrate eastward across KS
with a strong cold front moving southeast through the area. The GFS
and ECMWF have been fairly consistent in developing an FGEN enhanced
band of precipitation (post frontal) across portions of western and
north central Nebraska. The NAM appears to showing signs of this too
in the latest run. Will continue to monitor the model trends, as any
snowfall will be accompanied by strong north winds.
The next concern will be this weekend. The operational models and
ensemble data has been advertising the coldest air of the season
to arrive. Broad northwest flow will be in place across the region
during this time. A shortwave will move southeast within the flow
which will be accompanied by a strong Arctic cold front. There is
some potential for at least light snow with this feature, with
some model soundings showing favorable snow growth potential and
at least some light accumulation. Falling temperatures and strong
north winds can also be expected Friday night into Saturday
morning with the arrival of the front. Ensemble mean averages low
temperatures right near zero across Holt and Boyd counties
Saturday night/early Sunday morning. Many members are below zero
and so are both the operational GFS and ECMWF. Right now the
forecast is for lows to drop below zero with the coldest about -6F
or so. Wind chills will be even colder, with readings approaching
advisory criteria. A strong 1035mb (per ECMWF) will be centered
across the area Sunday, then shifting east Sunday night. Return
southerly flow should help to moderate lows Sunday night slightly,
but reading still likely dropping to near zero across
Boyd/Holt/Wheeler counties. Cold weather will linger into at
least the first few days of next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 530 PM CST Mon Feb 1 2021
There is a good chance the IFR/LIFR in fog/stratus across cntl
Neb this evening will spread west to KLBF tonight and last until
late morning Tuesday. IFR/LIFR is likely 05z tonight -21z Tuesday
affecting areas along and east of highway 83.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 11 AM CST Tuesday for NEZ010-027>029-
037-038-059-070-071.
&&
$$
UPDATE...CDC
SHORT TERM...Taylor
LONG TERM...Taylor
AVIATION...CDC
Area Forecast Discussion
National Weather Service Louisville KY
852 PM EST Mon Feb 1 2021
.Forecast Update...
Issued at 852 PM EST Mon Feb 1 2021
Radar remains mostly quiet this hour, but there are some very light
reflectivities (< 10 dBZ) east of I-65 from eastern Jefferson
County east to Franklin County and south toward Taylor County.
Because saturation in the DGZ decreases west of I-75, any precip
reaching the ground could be a freezing mist or brief freezing
drizzle. RAP soundings at SDF do show the moist layer up to -9 or -
10 C, so flurries are possible as well. Think that a fast moving mid-
level impulse diving SSE (currently near the IL/IN border) is
responsible for sufficient lift to produce very light precip. For
most, this is likely no more than a mist. But given current
temperatures, some very light icing is possible on elevated objects.
The primary precip shield is pushing south across northern KY this
evening and will continue to spread into the Bluegrass Region. This
is a slight western bulge in deep moisture extending up through the
DGZ pivoting south across the eastern half of KY. This light snow
will continue to move south across KY through the early morning
hours of Tue, with wintry impacts most likely near and east of the
US-127 corridor. The snow should push almost due south, perhaps
pushing slightly SSE with time given prevailing NNW flow over KY. As
it stands, the westernmost part of the Winter Weather Advisory
should not see much more than flurries. A light coating seems more
likely further east, so plan on dropping a row of counties from
Washington CO south through Monroe Co.
The eastern CWA, especially near and east of US-127, could see
quickly deteriorating roads tonight with only light snowfall
accumulations. Temperatures are currently in the upper 20s and will
slowly fall through the 20s overnight. Some roads could remain slick
during the Tue AM commute.
&&
.Short Term...(This evening through Tuesday)
Issued at 310 PM EST Mon Feb 1 2021
After a morning of light snow showers that dropped 1-2 inches across
the region, KLVX radar is quiet across most of the CWA this
afternoon. Latest sfc analysis places the primary sfc low just off
the coast of Delaware, with a secondary low over Ohio/West Virginia.
Regional mosaic radar reveals the secondary sfc circulation nicely
as returns wrap around the circulation over Ohio/West Virginia.
While radar is quiet now for most of the LMK CWA, still expecting to
see some backbuilding of light snow showers this evening over the
Bluegrass and Cumberland regions. Official LEX snowfall for today is
up to 2 inches, and with another round of snow for tonight, could
see an additional 0.5-1.0 inch accumulation for the LEX area and
surrounding counties. Based on the latest snow accumulation
guidance, have decided to trim a few counties off the current Winter
Weather Advisory that appear to be too far west for any additional
impactful snow amounts. After coordinating with JKL/OHX, have also
decided to extend the Advisory through 06z tonight. CAMs suggest our
eastern CWA won`t see much precip until closer to 00z this evening
as another wave of energy spins around the vertically stacked low.
Precip chances exit the eastern CWA by early tomorrow morning, but
clouds will hold on for areas along the I-65 corridor. Additional
snowfall on top of what we received earlier today could recover
roads and create slick spots again. Rural roads could be difficult
to travel on if left untreated, and any compacted snow could freeze
over tonight.
Several models, such as the RAP, HRRR, NAM, and HREF, pick up on
possibly seeing some lake effect flurries travel from the southern
tip of Lake Michigan, down the I-65 corridor and into our region by
Tuesday mid-late morning. With the large stacked low off to our
east, deep NNW flow and a stream of vorticity extending from the
Great Lakes down to Kentucky could be enough to get some flurries
despite dry air aloft working in. Skycover guidance from numerous
models have picked up on this trend in recent runs and are
consistent enough to see a swath of cloud cover over the I-65 area
and central KY. It will be interesting to see how this plays out,
and would not be surprised to see some flurries tomorrow. For now,
not enough confidence to include in the forecast given the amount of
dry air advecting in with NW flow, but just worth a mention.
Temps for tonight will drop to the low-mid 20s with NW winds of 10
to mph and occasional gusts of 20 to 25 mph. Tomorrow`s temps will
be similar to today and struggle to get to the mid 30s with
continuous NW flow.
.Long Term...(Tuesday night through Monday)
Issued at 321 PM EST Mon Feb 1 2021
Tuesday night, surface high pressure and upper ridging, centered
over the Plains, begin pushing the system over New England out into
the Atlantic. A few lake effect flurries could try to hold into the
night, but by Wednesday morning, skies are expected to begin
clearing from the west. Clear skies will cover the CWA by around
noon, but the sunny weather will be short lived.
Thursday begins under cloudy skies as a surface low begins moving
east across the Great Lakes with a cold front in tow. The cold front
brings in the next round of precipitation, and with the cool morning
temperatures, a wintry mix is likely. The change over to all rain is
expected by midday. Precipitation is expected to end Friday morning.
Again with morning lows, a light wintry mix is possible where
precipitation remains.
On Friday, behind the front, a weak surface high passes through the
region. This will likely allow sunshine to peek through the clouds
before a frigid weekend.
Over the last 3 runs of the GFS, a Canadian Clipper riding along
northwest flow pushes a cold front through the CWA. This is
something to watch. Blended temperatures on Saturday reach to either
side of 40, but if this clipper materializes, believe much cooler
temperatures are possible. Global guidance continues to push
temperatures lower for Sunday and with high pressure and clear skies
Monday morning, it looks even colder. Single digits are possible
(maybe even lower), but for the lowest temperatures, snow would need
to be on the ground. The GFS has its clipper system, and the Euro
brings precip to the CWA a little later. They both show
precipitation and cooler temperatures, but the details remain out of
focus.
&&
.Aviation...(00Z TAF Issuance)
Issued at 656 PM EST Mon Feb 1 2021
All terminals initializing at MVFR to begin the TAF period, but
drier air advecting in from the north overnight may result in
variable conditions. Lake-effect clouds struggling to fill in over
portions of Indiana may cause HNB to SCT out and go VFR much quicker
than anticipated, so will monitor for necessary amendments. SDF
should see MVFR clouds SCT out after 05-06z and then return again
Tuesday afternoon along with flurries. LEX will see light snow
showers develop after 02z and persist through about 07z with an
additional coating expected. Vsby dropping into the MVFR range at
times is likely in the snow. Snow will wind down at LEX in the early
morning hours, with drier air improving conditions after 12z. Winds
will remain breezy through the period out of the NNW.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...Winter Weather Advisory until 1 AM EST /midnight CST/ Tuesday
for KYZ035>037-039>043-046>049-054>057-064>067-075>078-081-
082.
&&
$$
Update...EBW
Short Term...CJP
Long Term...KDW
Aviation...EBW
Area Forecast Discussion
National Weather Service Sacramento CA
243 PM PST Mon Feb 1 2021
.SYNOPSIS...
A winter storm will move across NorCal late tonight into
Wednesday with mountain travel impacts expected. Dry weather
should return by Thursday and continue through the weekend with
periods of increased north to east winds.
&&
.DISCUSSION...
Upper level trough is moving onshore this afternoon as seen on
visible satellite imagery, bringing the next winter storm to
impact interior NorCal. A few light showers have been occurring
throughout the day in the mountains and northern Sacramento ahead
of the main trough passage. The main moisture plume is currently
situated just moving into the CWA with precipitation moving over
the Coastal Range and into the western Valley. NAM 3k and HRRR
show widespread precipitation slowly moving north to south through
the area through the afternoon and evening hours. The heaviest
precipitation is expected tonight through tomorrow with light
showers lingering through Wednesday along the back side of the
trough.
Moderate to heavy mountain snow is expected tonight through
tomorrow. Around 8 to 18 inches of snow is forecast over the
Sierra through the storm. Models show snow remaining north of I-80
this evening, spreading to areas along and south of I-80 after
midnight. Snow levels will start out around 5000 to 6000 feet
today, falling to 4000 to 4500 feet by tomorrow behind the frontal
passage. SREF plumes and NBM continue to suggest around 3 to 8
inches of snow down to Blue Canyon at around 5200 feet. Winter
Storm Warning remains in effect from tonight through early
Wednesday morning.
HREF, NAM 3k, and HRRR indicate periods of moderate to heavy rain
possible along the cold front as is moves through the area this
evening through the overnight areas. HREF shows only small (10 to
15%) probability of rain rates over 0.5 inch an hour. Therefore,
debris flow impacts over burn scars are not expected, though can`t
rule out localized flooding or minor slides due to areas of
heavier precipitation.
Post-frontal scattered Valley showers are expected to continue
tomorrow. A slight chance of scattered thunderstorms is also
possible in the Sacramento Valley. HREF and NAM indicating CAPE
around 200-300 J/kg in the Valley, enough to potentially form a
few stronger cells. Main impact with any thunderstorm would be
small hail and brief heavy rain with maybe some lightning. HREF
indicates rainfall rates should be below 0.5 inch in an hour, so
burn scar impacts are also not expected at this time.
There are slight discrepancies between GEFS and Euro ENS on the
trough placement Wednesday. Euro ENS has the trough slightly
farther south which would bring light showers into the Valley
Wednesday. GEFS is a bit shallower which would leave shower
chances mainly in the mountains. Either way, additional
precipitation accumulations would be fairly light.
Dry weather returns Thursday as ensembles show the trough pushes
to the east and upper level ridging builds over the eastern
Pacific. Gusty north to east winds are possible as the ridge
builds, though they are not expected to be strong at this time.
-HEC
&&
.EXTENDED DISCUSSION (Friday THROUGH Monday)...
Ensemble guidance has continued to indicate high pressure over
the region will keep Northern California dry though the extended
forecast period. High temperatures will generally be a smidge
warmer than the seasonal averages for this time of year. The
warmest locations will be in the Northern Sacramento Valley with
highs reaching into the mid to upper 60s this weekend which is
about 5 to 10 degrees above normal for early February. Low
temperatures in the Valley will be a little cooler than normal for
this time of year with temperatures expected to be in the mid 30s
to low 40s. Upper foothill and mountain locations will have low
temperatures that are slightly warmer than normal. Locally breezy
north to east winds are also possible at times.
&&
.AVIATION...
VFR decreasing to MVFR with areas of IFR and LIFR possible with
passing shower activity. Snow levels around 4500-6000 feet.
Southerly surface winds generally under 15kts with gusts up to 25
possible.
&&
.STO WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning from 7 PM this evening to 6 AM PST
Wednesday for West Slope Northern Sierra Nevada-Western Plumas
County/Lassen Park.
&&
$$