Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/13/18
Area Forecast Discussion
National Weather Service Burlington VT
911 PM EST Fri Jan 12 2018
.SYNOPSIS...
Today`s record warmth will be short-lived as a strong cold front
across the St. Lawrence Valley late this afternoon moves steadily
southeastward across the region this evening and overnight.
Temperatures will very rapidly fall below freezing with passage of
the front. Meanwhile, a developing low pressure system will track
northeastward along the frontal boundary, bringing heavy mixed
wintry precipitation to the region tonight through Saturday morning.
Periods of heavy snow and sleet are expected, with localized ice
accumulations up to a quarter inch across south-central Vermont.
Difficult and icy travel conditions are expected areawide,
especially late tonight and Saturday morning. Conditions will trend
colder and drier for Sunday and Monday. There is a chance for
additional snowfall Tuesday into Wednesday of next week.
&&
.NEAR TERM /THROUGH SATURDAY NIGHT/...
As of 911 PM EST Friday...Minor changes to the previous
forecast for the late evening update, mainly to attempt to match
temperature and ptype trends. I say attempt because I`ve been
chasing temps/ptype for the past 3 hours as conditions remain
very changeable. Last few runs of the HRRR have a had a good
handle on the thermal profile though with the sub-freezing air
at the surface-925mb ahead of 850mb but aloft temps are catching
up with snow being reported from KSLK westward, sleet at
KPBG/KFSO, and still rain eastward. Changeover to snow still
looks on track for the northern Champlain Valley in the 1-3AM
timeframe, central Vermont a couple hours later, and not until
closer to 8AM for southern Vermont. In the hours preceding the
snow, a mix of rain, sleet and snow is all possible. Total snow
and ice accumulations still appear to be on track, but I expect
them to be widely variable by the time the storm wraps up
tomorrow afternoon.
Previous Discussion...Very dynamic weather pattern in place
with near record to record warm temperatures / dewpoints/ and
precipitable water values across the North Country this
afternoon. High of 61F thus far at BTV, with a few locations
63-64F across wrn VT. In addition to the warm temperatures,
dewpoints have reached the mid 50s. Along with gusty south winds
and patchy fog, this has quickly eroded almost all of the
existing snowpack at lower elevations, with significant loses at
higher elevations per webcams (high of 53F at the Mt. Mansfield
summit). Additional light to moderate rainfall into this
evening and runoff will maintain the threat of river and ice jam
flooding through tonight. Flood watch continues thru 12Z
Saturday. Please refer to ongoing flood warnings for additional
details.
Next issue is the moderate to heavy mixed precipitation moving in
during tonight. Sfc cold front with an extreme low-level temperature
gradient was shifting sewd into the St. Lawrence Valley at 20Z.
Temperatures will drop 10-20 deg / 2hr with the frontal passage, and
will gradually be transitioning to mixed wintry precipitation by 22Z
at KMSS, and by 01-02Z around BTV with N-NW wind shift. We`ll be
seeing a "flash freeze" situation tonight, where temperatures dive
sharply below freezing and any standing water will quickly freeze on
roads and sidewalks. Will make for increasingly icy road sfc
conditions from NW-SE as cold air sweeps in, even beneath the
falling snow/sleet overnight.
We`ve been monitoring the vigorous mid-level shortwave trough across
the Tennessee river valley...which will shift newd along the frontal
zone during the overnight hours. Excellent warm conveyor belt across
nrn FL/GA/SC (1.8" PW values) will contribute to strong moisture
advection and lift back across the frontal zone late tonight into
Saturday morning, as the frontal zone bisects VT from SW-NE during
the predawn hrs. Combined with frontogenetic forcing, should see
periods of heavy mixed wintry precipitation, especially 06-15Z
Saturday.
No changes to the ongoing winter weather headlines, with Winter
Storm Warnings across nrn NY into central/nrn VT, and Winter Weather
Advisories for Rutland/Windsor/Orange counties. Will see freezing
rain of brief duration across nrn NY and the nrn Champlain Vly (1-2
hrs), followed by sleet and snow. Snow will be of longest duration
across nrn NY where favorably cold thermal profiles arrive first.
Have 6-10" snowfall across nrn NY, with localized amts to 12"
possible. Greater mixing with sleet in the Champlain Valley and n-
central VT supports 4-8" snow/sleet, with a few spots maybe up to
10" along the intl border area in nwrn VT. South and east of a line
from St. Johnsbury to Montpelier to Rutland, looking for more
freezing rain (around 0.25" possible) and reduced snow/sleet
accumulations of 2-4" with the prolonged icing. May see isolated
power outages with the freezing rain across central/s-central VT,
but overall ice loading not sufficient for widespread power issues
based on current indications. Will also see strong north winds of 15-
30 mph develop across the Champlain Valley with low-level channeling
of colder air filtering into the valley overnight. Strongest winds
will be near the srn end of Lake Champlain, where valley narrows
considerably.
As surface frontal wave low pulls away across the Gulf of Maine,
we`ll see lingering trowal/comma head snowfall across the
Adirondacks and nrn VT through about 16-18Z, before exiting quickly
to the north and east. Thus, should see snow winding down by early
afternoon with some improvement to travel conditions later in the
day along with partial clearing late afternoon into Saturday night.
Temperatures will be sharply colder, with lows in the single digits
across nrn NY and teens across VT, except low 20s far southeast.
Temperatures rise just a few degrees on Saturday, and then we`ll see
lows of -5 to -15F Saturday Night, and locally near -20F for Saranac
Lake (KSLK).
&&
.SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/...
As of 346 PM EST Friday...Strong 1040 mb high pressure will
moves slowly across the area Sunday while a weak short wave trof
aloft moves by without any fanfare. So Sunday looks to be
mostly sunny and quite cold with highs from the lower single
numbers in the north to low teens in southeast VT. Mainly clear
skies and calm winds Sunday night will allow temps to fall to 10
to 20 below with a few outliers either side of that.
&&
.LONG TERM /MONDAY THROUGH FRIDAY/...
As of 346 PM EST Friday...A very active long term forecast
period is in store with a deepening long wave trof over the
CONUS. Models start out in reasonable agreement with the trof
closing off as it moves southeast across the great lakes with
ridging aloft over our region and high pressure persists at the
surface. However, the evolution of the trof and surface low
pressure is quite different as it approaches the northeast US
Wed-Thu. GFS/CMC has a positive tilt trof with the surface low
out to sea east of the mid-Atlantic coast while the ECMWF
develops a new closed low off the mid-Atlantic coast and the
surface low right up the coast toward New England and into the
Gulf of ME. Result is rather low confidence in the Wed-Fri time
frame so for now keeping snow showers in the forecast through
that period regardless as one way or another the upper trof
should bring a chance of precip. Temperatures start out on the
cold side Monday with high pressure but return closer to
seasonable levels for the rest of the week.
&&
.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
Through 00Z Sunday...IFR/MVFR through the next 24 hours as
steady rain transitions to mixed precipitation and/or all snow
as temperatures drop sharply. Winds trending north/northwesterly
and modestly gusty from 15 to 25 kts, abating by Saturday
afternoon. Higher coverage of snow to occur at northern NY
terminals of KMSS and KSLK, with a longer period of mixed
precipitation at KPBG and moreso at Vermont terminals before the
change to snow later tonight. Steadier snows then taper off by
late morning into the afternoon hours on Saturday as CIGS
gradually improve.
Outlook...
Saturday Night: VFR. NO SIG WX.
Sunday: VFR. NO SIG WX.
Sunday Night: VFR. NO SIG WX.
Martin Luther King Jr Day: VFR. NO SIG WX.
Monday Night: Mainly VFR, with local MVFR possible. Chance SHSN.
Tuesday: Mainly MVFR, with local IFR possible. Chance SHSN.
Tuesday Night: Mainly MVFR, with areas VFR possible. Chance SHSN.
Wednesday: Mainly MVFR, with areas VFR possible. Chance SN.
&&
.HYDROLOGY...
Flood watch has been issued from 12z Today to 12z Saturday for
the combination of snow melt, rainfall, and ice jams causing
localized flooding on area streams and rivers.
The greatest threat for ice jam or main steam flooding includes
but not limited to the following rivers: the Ausable, Mad,
Missisquoi, and Lamoille Rivers, along with the Otter Creek.
Continued concern for isolated ice jams - mainly today into
tonight from a 36-48hr period of above freezing temps with max
temps into the 50s. River ice breakup will not be widespread,
but it appears that the mild temperatures will exist long enough
to get some river ice movement across the North Country. Thus,
rivers will need to be watched during this time frame.
We are anticipating accumulated thawing degree hours between
400-500 by this evening, with temperatures today in the upper
40s to mid 50s, before a cold frontal passage this evening.
Preliminary ice thickness reports/estimates indicate most rivers
have ice less than a foot thick, with some of the northern
waterways having ice perhaps as much as 18 inches thick in
spots. As a general rule, river rises of 2-3x the ice thickness
is needed to breakup river ice. Given potential QPF 0.50-1.50"
and snowpack SWE 2-4 inches, there is certainly some threat of
getting river rises on the order of 2-4 feet, with crests most
likely this evening. If river ice movement does occur, issues
may linger into Saturday, even as temperatures drop back below
freezing behind the cold front. Persons with interests along
rivers should continue to monitor this developing situation.
&&
.CLIMATE...
Record Highs for January 12th:
Burlington, VT......55F.....1980. (New Record: 61F so far today)
Montpelier,VT.......53F.....2017.
St. Johnsbury, VT...54F.....1980.
Massena, VT.........50F.....2017. (New Record: 57F so far today)
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...Flood Watch until 7 AM EST Saturday for VTZ001>012-016>019.
Winter Storm Warning until 4 PM EST Saturday for VTZ001>009-
016>018.
Winter Weather Advisory until 4 PM EST Saturday for VTZ010>012-
019.
NY...Flood Watch until 7 AM EST Saturday for NYZ026>031-034-035-087.
Winter Storm Warning until 4 PM EST Saturday for NYZ026>031-
034-035-087.
&&
$$
SYNOPSIS...Banacos
NEAR TERM...Banacos/Lahiff
SHORT TERM...Sisson
LONG TERM...Sisson
AVIATION...JMG
HYDROLOGY...Banacos/Hastings/Taber
CLIMATE...Banacos
Area Forecast Discussion
National Weather Service State College PA
515 PM EST Fri Jan 12 2018
.SYNOPSIS...
A very sharp cold front will push gradually southeast across
Central Pennsylvania today and tonight. A developing wave of
low pressure on the front will track across southeast Pa late
tonight. A deep upper level trough will swing through the region
this weekend into the middle of next week, then lift out by the
end of next week.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Numerous near-short term forecast POP/weather/temp and precip
type grids were heavily weighted twd the latest - 18Z RAP model
which concurs nicely with the very sharp sfc cold front
extending from near KBFD to just east of KFKL and KPIT at 1930Z.
Extremely sharp temp drops of 25+ deg F (from the low 60s to
the mid 30s) were occurring within just 2 hours of its passage.
As an example...KAGC is currently 62F while KPIT is down to
34F. The front is expected to be just west of the I99/rt 15
corridor north of KIPT around 23Z today. Little change in timing
or precip type and its transition to FZRA -> PL and Snow has
been made following a multi model blend of high res data and
Meso/SREF/GEFS guidance.
Snowfall totals were modified only slightly and remain a general
1-2 inches below WPC amounts as it appears there could be a
slightly more prolonged period of -fzra and sleet before a
changeover to snow this evening across the NW mtns, and tonight
elsewhere.
Prev Disc for late today through tonight...
It`s our understanding that roads crews will not be focused on,
since the significant (and in some parts of Western PA - Heavy)
rain overnight/this morning, and around an additional 0.50 inch
of QPF before the changeover, would be washed off and
ineffective in this particular high impact winter weather event.
The sharp drop in temp after the cold fropa and continued
precip in the form of signif sleet and/or fzra rain across the
central valleys, and sleet to several inches or more of snow
across the NW mtns late today and tonight, will lead to a
CLASSIC FLASH FREEZE case with very hazardous travel conditions
developing quickly.
Showery/mild weather will remain across much of the Susq Valley
for the rest of the day.
Deep southerly flow ahead of approaching cold front will
continue to flood the region with unseasonably mild air late
this afternoon/early this evening, with temps from the upper 50s
near the Allegheny front to the mid 60s over the southeast
portion of the forecast area.
Latest models continue to indicate a ptype changeover to mixed
precip across northwest Pa this evening, as low level cold air
undercuts deep/moist southerly flow in advance of shortwave
lifting up the Appalachians. As surface low tracks across
southeast Pa late tonight, confidence is high for a few to
several hour period of heavy snow across northwest Pa in
association with fgen forcing within thermally direct jet
entrance region of a 150+ kt upper jet situated across srn
Ontario and Lake Erie. Model Blend and WPC Guidance continues to
support a high confidence of 6-9 inches across Warren/Mckean
counties, with a few hours of 1 inch/hour rates likely around
midnight.
The heavy snow will be preceded by a transition from rain to
wintry mix which will shift to the southeast with time. The
shallow cold air will initially undercut the warm/moist air with
a significant icing zone possible over parts of Central PA
before changing to snow as cold air deepens through the column.
Based on model soundings and WPC guidance, believe fzra will be
fairly short-lived with sleet a more predominant ptype before
eventual change to snow early Sat morning. A very messy start
to the weekend for sure, with a glaze of ice and coating of
snow/sleet possible as far southeast as the Lower Susq Valley.
Mins temps by morning will likely vary from the single digits
across the NW mtns (with wind chills in the single digits below
zero) to near 30F in the far SE.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
Expect any lingering light snow/flurries to taper off by late
Saturday morning, as upper level shortwave and associated
surface low lifts rapidly northeast of PA. An additional
coating to 1.5 inches of snow is all that should occur between
12-15Z Saturday, and that will be almost exclusively confined
across the mtns North and NE of KIPT.
Much colder air will continue to pour into the state on
a gusty north-northwest flow in the wake of this system
Saturday. SREF plumes indicate very little rise from early AM
temps and highs only in the teens over the NW Mtns to low 30s
across the southeast counties. Dry, arctic air and low inversion
heights should limit lake effect activity to mainly just
flurries across the western mountains Saturday afternoon and
night.
Main concern will be low wchills Sat night. Current indications
are for apparent temps close to advisory levels over the
northern mountains Sat night.
&&
.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
Saturday night and Sunday will be cold and windy post-storm as
strong high pressure builds in from the GLAKS. Monday will start
quiet but a clipper spreads light snow into the area Monday
night and Tuesday followed by cold and dry conditions into
Thursday. Monday night`s clipper could be accompanied by
squalls. Pattern may amplify again by next weekend with milder
flow ahead of vigorous shortwave and storm ejecting from the
Rockies to the Upper Midwest Sat-Sun with strong FROPA possible
over PA on Monday.
&&
.AVIATION /22Z FRIDAY THROUGH WEDNESDAY/...
Periods of rain along with MVFR to IFR restrictions and gusty
south winds are continuing to move into the region with the
heaviest bands through the western half of PA. The latest radar
is showing some mixed precipitation through at PIT and BFD is a
little above freezing. So there will be a changeover to a
wintry mix over the next few hours. Precipitation will mix to
snow from northwest to southeast this evening. Latest models
have the 02Z in the NW to 12Z through the SE. Winds will shift
abruptly from south/southeast to northwest with the passage of a
strong cold front. LLWS everywhere prior to the cfropa.
Low ceilings and reduced visibilities expected to persist
overnight and into Saturday as well as gusty N-NW winds, with
improving weather for late Saturday.
Outlook...
Sat...AM rain/low cigs poss east. AM snow/ice poss central/west.
Sun...No sig wx expected.
Mon...PM light snow poss west. PM low cigs poss east.
Tue...Morning snow ending. Becoming VFR south and east,
lingering snow showers and restrictions over the mountains.
&&
.HYDROLOGY...
A mild surge in temperatures combined with 1-3 inches of rain
from Thursday afternoon through late Friday will produce
significant rises on rivers and streams with the potential for
ice jams and low- lying flooding. Streamflows are currently low,
but many waterways are choked with ice. The greatest risk of
flooding is in the Watch area over north- central PA where
snowmelt will be a contributing factor today.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Saturday evening for PAZ004>006-010>012-
017>019-037-041-042-045-046-049>053.
Winter Weather Advisory until 10 AM EST Saturday for PAZ012-
017>019-024>027-033-037-041-042-045-046-049>053.
Winter Weather Advisory from midnight tonight to 10 AM EST
Saturday for PAZ028-034>036-056>059-063>066.
Winter Storm Warning until 10 AM EST Saturday for PAZ006-010-
011.
Winter Storm Warning until 10 AM EST Saturday for PAZ004-005.
&&
$$
SYNOPSIS...Lambert
NEAR TERM...Lambert
SHORT TERM...Fitzgerald/Lambert
LONG TERM...Ross/DeVoir/RXR
AVIATION...Lambert/Ceru
HYDROLOGY...
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
916 PM EST Fri Jan 12 2018
.SYNOPSIS...
A cold front will sweep east across the area tonight, with gradually
drier and colder high pressure settling in from the north through
the weekend. Another cold front will cross the region Tuesday
through Tuesday night, ushering in even colder air from mid to late
next week.
&&
.NEAR TERM /THROUGH SATURDAY/...
900 PM EST Update...No major changes needed to the fcst grids. Light
precip still exiting the far ern zones and linger across the NC
mtns. Snow showers will begin to develop along the wrn mtns with no
sigfnt accums thru the next update.
630 PM EST Update...Made some tweaks to PoPs and temps/tds as the
pattern remains quickly progressive. On-going stream flood conds
across ern Transylvania County will persist overnight...however no
new areas will be under the gun for any hydro concerns.
As of 225 PM: Low pressure is approaching the Appalachian chain
from the west, along a cold front extending from Quebec to the
central Gulf Coast. Preceding this front, a plume of moisture
is bringing a broad area of showers to the western Carolinas and
Georgia within the warm sector of the system. Up to a couple hundred
joules of SBCAPE has developed in our eastern and southern zones,
with effective bulk shear of 40 to 50 kt thanks to the very deep
trough to our west. Accordingly 0-3km bulk shear is in excess of
100 m2/s2 in some of the same area. We have been anticipating a
small severe threat in these portions of our CWFA, and we have
not yet written off that possibility late this afternoon. RAP/HRRR
suggest as 850mb jet moves over the Piedmont later this afternoon,
the more vigorous activity now over SE GA and the SC Midlands
will track NE, possibly developing QLCS features. The threat is
greatest between 21z and 00z, per HRRR and HREF. In particular,
the latest HRRR depicts some streaks of elevated updraft helicity
moving through the southern I-77 corridor, which agrees with
current radar trends. Lightning has been basically nonexistent
within today`s upstream activity so thunder mention is extremely
limited in the fcst.
Following the departure of the aforementioned precip, low level
moisture will linger over the NC mountains for some time. Cold
advection will get underway up there in the 00-03z timeframe;
while some dynamic forcing will still be in play with the upper
low skirting by just to the northwest, the turn to NW winds will
be the primary source of lift. Models differ as to how the cold
advection affects low-level temperatures; namely the NAM depicts the
low levels cooling much more quickly than the layer above the PBL,
which leads it to produce a warm nose that the RAP and especially
GFS don`t show. Accordingly, the NAM suggests a brief period of
wintry mix in some areas instead of a clean rain-snow transition
like we would typically see in NW flow. This seems improbable
overall, but a brief mention of FZRA was included (per Bourgouin
p-type technique) further away from the spine of the mtns, where
the warmer air is most likely to still be in place. However this
does not result in more than a trace of ice. Overall the moisture
is fairly shallow and winds are not particularly impressive despite
the strength of the front. Thus snow amounts are not expected to
exceed an inch except in the highest elevations of the Smokies. We
will issue an SPS to cover the small threat that black ice will
occur where roads remain wet as the subfreezing temps return
overnight. Gusty winds and falling dewpoints may be enough to dry
the roads. With downsloping, mixing and initially moist conditions,
most of the Piedmont looks to remain above freezing overnight.
The northwest flow snowfall should peak in the early morning, though
the setup suggests at least flurries will linger through most of
the day in the favored areas. Gusty winds will continue through
the day but still look unlikely to reach advisory criteria. Max
temps will be at or below freezing in the mountains, and mainly
in the 40s in the Piedmont.
&&
.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
As of 235 PM EST Friday: Guidance showing a relatively tranquil yet
cold short term Sunday and Monday. Winds will diminish Saturday
night as high pressure builds in from the north behind the departing
cold front. The high remains ridged into the area from the north on
Monday. The air mass associated with the high is cold with lows
around 10 degrees below normal both nights. Highs Sunday will be 10
to 15 degrees below normal then rise a few degrees on Monday. Wind
chill values will drop to around zero across the higher elevations
Saturday night but will be warmer Sunday night with less wind.
&&
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
As of 305 PM EST Friday: Guidance in general agreement through the
medium range. Upper low over the Great Lakes Monday night opens up
and moves east on Tuesday as a short wave digs into the MS Valley.
This short wave closes off an upper low and moves it near the VA/NC
border Wednesday then to our east Wednesday night. At the surface,
ridge of high pressure moves east of the area as a cold front moves
toward the spine of the Appalachians Monday night and into the
mountains Tuesday. The front moves east of the area Tuesday night
but a trough of low pressure forms in the wake of a surface wave
developing along the front. This trough forms near the Savannah
River Tuesday night and moves north across the area Wednesday. The
guidance shows an H85 low forming in the lee of the mountains as
well with quite a bit of moisture. The southerly H85 flow develops
isentropic lift and some frontogenesis creating enough lift for
precip to develop. There could even be some weak instability
Wednesday helping kick off shower activity. The temps behind this
front are very cold, H85 temps 2 standard deviations below normal on
the GEFS mean, which would help the precip change to snow for much
of the area. The GEFS mean shows a good chance of precip developing
with accumulating snow, generally 2 inches or less, with this
system. Since the GFS, GEFS mean, and the ECMWF are all in decent
agreement, have gone with low chance PoP for the forecast area
Wednesday. Despite the agreement, there is still quite a bit of
uncertainty with this forecast as all these elements have to come
together at the right time for this scenario to develop. Temps
increase Tuesday ahead of the front before falling well below normal
for Wednesday behind it.
Temps remain well below normal for Thursday with drying conditions
as the cold air mass in place. Temps warm to near normal for Friday
as the air mass quickly moderates and heights rise.
&&
.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
At KCLT and elsewhere: Lingering -shra will persist over the
terminals with limited restrictions remaining thru 03z. Mainly MVFR
CIGS/VSBY outside the NC mtns. Dry air will work in overnight and
clouds will begin to scatter out most locales. Good gust potential
beginning arnd midnight mtn valleys and near daybreak elsewhere as
the p/grad tightens along with some measure of llvl CAA. No sigfnt
VSBY concerns are had with sfc winds keeping things mixed. VFR conds
will persist thru the day Saturday with only FEW/SCT mid to upper
clouds.
Outlook: VFR and cold conditions are expected to prevail through
early next week.
Confidence Table...
02-08Z 08-14Z 14-20Z 20-00Z
KCLT Med 73% High 93% High 100% High 100%
KGSP High 80% High 100% High 100% High 100%
KAVL Med 72% High 92% High 100% High 100%
KHKY High 92% High 98% High 100% High 100%
KGMU High 93% High 100% High 100% High 100%
KAND High 97% High 100% High 100% High 100%
The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables and ensemble forecasts
are available at the following link:
www.weather.gov/gsp/aviation
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.
&&
$$
SYNOPSIS...HG
NEAR TERM...SBK/Wimberley
SHORT TERM...RWH
LONG TERM...RWH
AVIATION...SBK
Area Forecast Discussion
National Weather Service Indianapolis IN
950 PM EST Fri Jan 12 2018
.UPDATE...
The AVIATION Section has been updated below.
&&
.SYNOPSIS...
Issued at 228 PM EST Fri Jan 12 2018
Snow will come to an end this evening across central Indiana as a
Low Pressure exits the area. Cold...Arctic high pressure over the
upper midwest will then build across Central Indiana and the Ohio
valley through the weekend...bringing very cold but dry winter
weather.
A quick moving Low pressure system is then expected to push in to
the Western Great lakes on Sunday night....pushing a cold front
across Indiana on Monday. This will bring another round of snow
to central Indiana.
Yet another arctic will arrive across Central Indiana on Tuesday.
This will continue the dry and cold weather for much of the next
work week.
&&
.NEAR TERM /Tonight/...
Issued at 228 PM EST Fri Jan 12 2018
Surface Analysis early this afternoon shows lows pressure over
West Virginia...with a cold front stretching from Western New
York...SW along the Appalachian Mountains to NW Georgia. Water
Vapor shows an upper low over Western Kentucky...pivoting
northeast...still providing southerly flow aloft to Central
Indiana. Radar shows snow showers overspreading Central Indiana
stretching in a band from Vincennes and Terre Haute east to a
Winchester-Greensburg line. Current band across the area suggests
a deformation zone like configuration...and accumulating snows
will be expected the next several hours as the band slowly edges
eastward. Ongoing Snow will continue to impact the evening rush
hours. Cold northerly surface flow was in place across Central
Indiana...with temps in the middle 20s flowing across the forecast
area.
GFS and NAM suggest the upper low will continue to slide eastward
this afternoon and tonight...and the southerly flow aloft of
moisture will be lost as it is diverted to the east. This will
bring an end to the precipitation across Central Indiana shortly
after 00Z. HRRR is in pretty good agreement wit this...sliding the
back edge of the precip to the southeastern counties by 00Z.
Forecast soundings show dry air arriving within the column near
00Z and impressive drying and subsidence arriving by 03Z as the
flow aloft shifts to the north on the backside of the upper
system. Thus will keeps some snow chances through the afternoon
and early evening across the area...but best chances will be
across the southeast as the system departs. Will try and trend
toward a dry forecast by midnight as the dry air previously
mentioned will be well in place.
Given the ongoing Cold air advection and the fresh snow...will
trend lows overnight at or below the forecast builder blend.
&&
.SHORT TERM /Saturday through Monday/...
Issued at 228 PM EST Fri Jan 12 2018
Quiet weather will be anticipated on Saturday through Sunday. The
GFS and NAM show mainly a cold NW flow...slowly transitioning to
westerly through Sunday. Little in the way of upper support will
be pushing across the area through Sunday. Meanwhile at the
surface...High pressure looks to remain in place across the
area...slowly progressing east of Indiana by late Sunday. During
this time forecast soundings and time height show a dry column
with subsidence...which should be expected given the dry...polar
air mass. Thus will trend toward Partly clouds and trend temps at
or below the forecast builder blend through Sunday.
On Sunday night and Monday...the GFS Shows a strong wave aloft
over the Northern Plains poised to push southeast into the Ohio
Valley. Models suggest an associated well organized surface low
and cold front arriving in Central Indiana on Monday. Return flow
on the backside of the departing high should allow some limited
moisture return...however given the cold air mass...large amounts
of moisture will not be needed for snowfall. Forecast soundings
show a saturated column as the cold front approaches and passes
on Sunday Night and Monday with excellent saturation within the
-10C to -20C layer. Thus confidence is high for an accumulating
snow as this system passes...however we would not be surprised
to see slight changes to the timing in the next few models runs.
Nonetheless will include high pops for snow on Sunday
night...particularly after midnight...and on Monday.
&&
.LONG TERM /Monday Night Through Friday/...
Issued at 235 PM EST Fri Jan 12 2018
Models are close enough that the model blend initialization
was accepted for most items.
Much of the long term will be dominated by upper troughing across
the eastern USA. The north to northwest flow will allow Arctic air
to move into the area. Snow cover refreshed by the Monday system
will aid in bringing temperatures down.
By the end of the long term, temperatures will moderate as upper
flow relaxes and becomes more zonal.
Some lingering snow may continue in the east Monday evening. A few
lake enhanced snow showers may make it into the far northwest around
Tuesday. Otherwise the long term will be dry.
&&
.AVIATION /Discussion for the 13/03Z TAF Update/...
Issued at 949 PM EST Fri Jan 12 2018
Update...
Increased winds at KIND and extended MVFR conditions through Sat
07Z.
Previous Discussion...
MVFR conditions with a few lingering snow showers will continue
through Sat 03Z. After that, VFR should become the prevailing
flight category for the remainder of the TAF period. The main
threat will be the strong northerly winds. Sustained speeds will
range between 17 to 22 kts with gusts up to 31 kts through Sat
11Z.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 10 PM EST this evening for INZ021-
028>031-035>049-051>057-060.
Winter Storm Warning until 10 PM EST this evening for INZ061>065-
067>072.
&&
$$
SYNOPSIS...Puma
NEAR TERM...Puma
SHORT TERM...Puma
LONG TERM...50
AVIATION...TDUD
Area Forecast Discussion
National Weather Service Pueblo CO
510 PM MST Fri Jan 12 2018
.UPDATE...
Issued at 510 PM MST Fri Jan 12 2018
Updated to end winter weather advisory across the central
mountains.
&&
.SHORT TERM...(This evening through Saturday)
Issued at 307 PM MST Fri Jan 12 2018
Currently...
Front moving across the region at 2 pm this afternoon. Boundary was
just south of the US50 corridor and was continuing southward. A line
of showers was noted over the plains, mainly from near KLIC
southeastward to just north of Holly CO. A few virga/very light rain
showers were noted over a few other areas of the plains. Snow
showers were noted over the mountains, especially the central mtns
and the Pikes Peak region.
Rest of today and into tonight...
The main band of showers over the plains will continue to move
southeast and should be out of the region by sunset. However HRRR
shows some other light showers will be possible over most of the
region until at least late evening. These showers are not expected
to amount to much. Over the central mountains snow showers will last
into early evening before dissipating.
Gusty winds over the plains will decrease after sunset.
Temps tonight will be on the cold side with mainly tens across the
plains, with the coldest air over the far eastern plains and the
warmest temps (aoa 20F) just east of the southern mtns. San Luis
valley will be in the single digits along with most mtn locations.
Tomorrow...
Temps will be pretty seasonable tomorrow across the region with 40s
across all of the plains, with generally partly to mostly sunny
skies, with a few more clouds over the plains. It will be dry, with
the exception of some snow showers over the northern sections of the
central mtns. Winds will be light an diurnally driven over the
plains with modest winds over the central mtns.
.LONG TERM...(Saturday night through Friday)
Issued at 307 PM MST Fri Jan 12 2018
Saturday night-Sunday...Models remain consistent with keeping
moderate northwest flow aloft across the region, with another
embedded wave translating across the Upper Midwest Saturday night.
This wave looks to be too far east to bring any precipitation,
though the moderate northwest flow develops lee troughing across the
plains, allowing for the the shallow cool airmass across eastern
Colorado to scour out from west to east Saturday night. The shallow
cool airmass mixes out completely across the eastern plains on
Sunday, with highs warming back into the 50s across the lower
elevations, and mainly in the 30s and 40s across the higher terrain.
Sunday night-Tuesday...Models are coming into better agreement of a
stronger wave embedded within the northwest flow aloft translating
across the Rockies Sunday night and Monday. Wave sends a strong
backdoor cold front across eastern Colorado late Sunday night,
which backs up across the eastern Mountains through late Monday
morning. Models are indicating some light precipitation spreading
from east to west across the eastern plains, with model soundings
indicating the potential for light freezing drizzle across the
plains early Monday morning, before colder air works into the area
with any freezing precipitation quickly changing to light snow
and flurries Monday mid morning and afternoon. Some light and
fluffy snow accumulations will be possible along and west of the
I-25 corridor through the day Monday. Highs in the 30s early
Monday morning across the plains will cool through the rest of the
morning and afternoon, as easterly upslope flow increases through
the day. Further west, dry weather with at to slightly below
normal temperatures is expected on Monday, though can`t rule out
some light snow and flurries across the Central Mountains, with
the northwest orographic flow.
Northwest flow aloft moderates Monday night and Tuesday, with any
snow/flurries across the mountains diminishing into Monday evening.
With the cold airmass in place, overnight lows to be on the chilly
side, in the single digits and teens areawide. Dry conditions and
moderating temperatures expected for Tuesday.
Wednesday-Friday...Some differences in the longer range models
continue, though EC and GFS generally agree of another embedded wave
digging across the Rockies on Wedensday, though continue to differ
on strength of the system. At any rate, system looks to mainly
affect the higher terrain along and west of the ContDvd, with
blended pops introducing slight chances of snow in the Wednesday and
Wednesday night timeframe, with temperatures at to slightly above
seasonal levels. Warmer and drier conditions expected on Thursday
with short wave ridging across the region, which gives way to
increasing southwest flow aloft across the area on Friday, as
another progressive system takes aim on the Rockies for Friday
and into early next weekend.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 307 PM MST Fri Jan 12 2018
VFR conditions are anticipated during the next 24 hours at all 3 taf
sites, KPUB, KALS and KCOS. The only exception may be some occnl low
cigs this evening at KCOS and guidance products show some low clouds
developing between ~03 and ~06 UTC. Gusty winds this afternoon will
decrease after sunset. Winds will be light tonight with diurnally
driven light winds tomorrow.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...MW
SHORT TERM...HODANISH
LONG TERM...MW
AVIATION...HODANISH
Area Forecast Discussion
National Weather Service San Diego CA
738 PM PST Fri Jan 12 2018
.SYNOPSIS...
Areas of dense fog will affect the immediate coast tonight, but is
forecast to slowly improve from north to south overnight. High
pressure aloft will bring warm and dry weather through the long
weekend. Offshore flow will produce areas of gusty northeast
winds in foothills and adjacent valleys. Fair weather will
continue next week as flow turns back onshore. Late next week a
trough of low pressure will bring strong onshore winds to the
mountains and deserts Thursday night and Friday, and also our next
chance of showers.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
...Update...
The warm up commenced in full force today with highs in the 60s in
the mountains, high desert, and immediate coast and well into the
70s to near 80F degrees elsewhere. Lake Elsinore hit 81F degrees.
It will warm even further this weekend, especially west of the
mountains where 80s are forecast away from the coast.
Fog continues to impact portions of the immediate coast,
especially San Diego County. Most locales have visibility above 1
mile, but there are patches of 1/4 mile or less visibility. The
trend overnight will be for gradual clearing of the fog from
north to south as offshore flow spreads to the coast. However,
latest HRRR model run shows that clearing may not occur until dawn
for the southern San Diego coast. Clearing will occur much sooner
across Orange County and northern San Diego County. Have expanded
in time the fog/sky grids, following the aforementioned trend.
Offshore winds have picked up as expected and are gusty through
narrow areas that are typically prone to Santa Anas (through and
below passes and along coastal slopes) with gusts in the 30-40 mph
range. Models show little increase overnight and winds remaining
localized. See previous discussion below for further forecast
details.
...Previous Discussion (Issued at 132 PM PST Fri Jan 12 2018)...
Areas of dense fog along the immediate coast have been
persistent, as reported by much of OC and Camp Pendleton, but
patchier in San Diego County. Fog will continue, dense in some
areas, along the immediate coast probably through the evening. But
an offshore trend in pressure gradients are forecast to push fog
away from the coast overnight. High pressure aloft will peak this
long weekend and will bring us more fair and warm weather,
although with some high clouds to add texture to the sky. An
offshore surface pressure gradient sets up this evening and
northerly breezes will get started below the Cajon Pass. As the
offshore flow evolves Saturday, those winds will push through all
mountain passes and foothills into some valleys and continue all
day. Top wind gusts should be late morning Saturday and could
reach 40+ mph at the most favored locations. Top valley gusts
could top 30 mph. These winds diminish somewhat late Saturday and
a weaker version will continue through Sunday morning.
Temperatures will get a boost from this offshore flow Saturday and
Sunday, and will top out in the 80s for inland coastal areas and
valleys. As the offshore flow relaxes on the holiday, temps will
back off a few degrees in the coastal basin. A shortwave trough is
forecast to move through northern California Tuesday, which will
increase the onshore flow some and continue the cooling trend each
day next week. By Thursday night, a Pacific trough of low
pressure sags down the West Coast, promising strong onshore winds
mainly for mountains, deserts, and coastal waters. There is also a
chance of rain and mountain snow. Right now it doesn`t look super
wet, and the best chance appears to be early Friday.
&&
.AVIATION...
130230Z...COAST...SCT-BKN001-002 WITH VIS 1/4 TO 3 MILES ALONG THE
IMMEDIATE COAST SPREADING LOCALLY INLAND AND IMPACTING KCRQ...KSAN
AND KSNA THROUGH 08Z. AT 02Z...DENSE FOG WITH A VIS OF 1/4 MILE WAS
REPORTED AT KCRQ, WHILE THE VIS WAS 3 MILES AT KSAN AND 4 MILES AT
KSNA. LOW LEVEL EASTERLY WINDS LATER TONIGHT WILL SLOWLY PUSH THE
LOW CLOUDS AND DENSE FOG OFF THE COAST BETWEEN 06Z-12Z SATURDAY.
VALLEYS/MOUNTAINS/DESERTS...EAST TO NORTHEAST WIND GUSTS OF 25-35 KT
WILL DEVELOP ALONG COASTAL MOUNTAIN SLOPES INTO ADJACENT FOOTHILLS
TONIGHT THROUGH SAT MORNING WITH AREAS OF LLWS. SCT-BKN250 WITH
UNRESTRICTED VIS THROUGH SAT MORNING.
&&
.MARINE...
A MARINE WEATHER STATEMENT HAS BEEN UPDATED FOR DENSE FOG WITH
VISIBILITY 1 MILE OR LESS THROUGH LATE TONIGHT. DRY EASTERLY SURFACE
FLOW WILL GRADUALLY PUSH THE DENSE FOG FARTHER WEST EARLY SATURDAY
MORNING WITH IMPROVING VISIBILITIES. NO OTHER HAZARDOUS MARINE
WEATHER IS EXPECTED THROUGH SUNDAY.
SEAS WILL INCREASE TO 7-11 FEET MONDAY AND TUESDAY IN THE OUTER
WATERS FROM AN INCREASING LONG-PERIOD WNW SWELL.
&&
.BEACHES...
ELEVATED SURF AND STRONG RIP CURRENTS SATURDAY AND SUNDAY. EARLY
NEXT WEEK A NEW LONG PERIOD WNW SWELL (285 DEGREES AT 18 SECONDS)
WILL BRING HIGH SURF OF 6-9FT MONDAY THROUGH WEDNESDAY.
&&
.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.
&&
$$
PUBLIC...Gregoria (Update)/MM (Prev Discussion)
AVIATION/MARINE...Moede
...Update to aviation forecast discussion...
.SHORT TERM...(This evening through Saturday)
Issued at 347 PM CST Fri Jan 12 2018
Northwest flow continues aloft over the central and western CONUS
behind Thursday`s upper wave. Water vapor and IR imagery show a weak
wave moving into the central Plains today with sporadic light
radar returns and some trace to very light measured precipitation
in snowfall from northwest Kansas into northeast Nebraska. A
stronger and more persistent area was just west of the CWA at 20Z
though ceiling heights remain above 6000 ft AGL and northeast
winds under this layer behind the surface ridge along the Missouri
River will continue dry air entrainment into this area into the
early evening. NAM, GFS, and ECMWF are consistent with weak mid-
level frontogenesis weakening this evening and the RAP and HRRR
have been consistent in diminishing precip trends over the next
several hours, and a small PoP for measurable amounts should
suffice.
Weak low-level cold air advection continues through tonight, with
cloud cover with the weak wave slowly decreasing into midday
Saturday. With cloud cover persisting, have lows a touch warmer than
previous forecast, but single digits still expected with apparent
temps a few to several degrees below zero. Weak warm-air advection
develops Saturday afternoon, though the surface ridge remains to the
northeast for another cold day. Mid cloud returns in the afternoon
as a weak PV anomaly surges south out of western Canada.
.LONG TERM...(Saturday night through Friday)
Issued at 347 PM CST Fri Jan 12 2018
Models to differ with the speed and placement of the
aforementioned wave, but decent precip chances develop overnight
into Sunday morning as a narrow band of saturation moves through.
Lapse rates do increase and could support a few hours of light to
moderate snow with 1-2" snowfall potential as the column should
remain well below freezing for any mixed precip. This wave exits
by early Sunday evening, but attention will turn not far to the
northwest as a stronger wave comes south-southeast out of the
northern Plains with a potent cold front following. Another
narrow-in-time precip window moves across the area late Sunday
night into midday Monday as strong frontogenesis works through.
There are some differences in specifics at this range too, and a
stronger west wind around 850mb may be able to bring some mixed
precip in at precip onset as well as afternoon temps reach into
the 30s, but slightly higher precip/snowfall amounts seem in order
for this wave. Monday will likely be another day of early day
highs with temps falling into the single digits around sunset and
north-northwest winds continuing and Advisory- level wind chills
a good possibility from early Monday evening into midday Tuesday.
Conditions looking much less concerning for Wednesday into Friday as
the upper flow pattern shifts east and west to southwest flow
developing. There could be a shortwave passage around Thursday
though available moisture would likely be limited. South to
southwest surface winds may push temps to above normal levels next
Friday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 514 PM CST Fri Jan 12 2018
VFR conditions are expected through the taf period. The wind
speeds will become light and variable tomorrow afternoon as a
surface ridge slides across the area.
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...65
LONG TERM...65
AVIATION...Sanders