Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/06/17
Area Forecast Discussion
National Weather Service Denver/Boulder CO
853 PM MST Thu Jan 5 2017
.UPDATE...
Issued at 853 PM MST Thu Jan 5 2017
The bulk of the storm is heading south with only light snow
remaining over the central mountains. Will allow the Winter
Weather Advisory to expire with conditions improving.
High cloud cover is hanging on slightly longer than expected as
the system slides south. This may affect how cold temperatures get
overnight. But with several more hours still left in the night,
will anticipate the drier air pushing south to clear skies and
allow temps to plummet. Current wind chill readings are already in
the -10 to -25 degree range over the northeast plains, so will
allow the Wind Chill Advisory to continue.
&&
.SHORT TERM...(This evening through Friday)
Issued at 310 PM MST Thu Jan 5 2017
Snowfall has generally wrapped up acrs the northern two-thirds of
the forecast area at this time. Can see on satellite a sharp edge
to the cloud shield along the Wyoming/Colorado border. However
cooling cloud tops and a widening area of light to moderate
snowfall over west central CO was occurring in the vicinity of
weak mid level vort maxima indicated by the RAP and NAM. They show
this feature and this precip tracking east-southeast clipping the
swrn corner of the fcst area late this afternoon and early
evening. Additional snow accumulations will range anywhere from
2-6 inches over the higher terrain in Summit and Park counties by
mid evening. Will change the winter storm warning for mtn zone 34
to a winter weather advisories as snowfall rates should stay more
in the light to moderate side...but will extend this until 9 PM.
Out on the plains...northwest winds of 7-15 kts and temperatures
from 5 below to 15 below will prompt the issuance of a wind chill
advisory tonight. Advisory will cover zones 042...044...048-052.
Closer in the Front Range...winds will be nearly calm overnight.
So will refrain from issuing a wind chill advisory here even with
temperatures falling well below zero overnight. Lastly clearing
skies from north to south will allow temperatures to slide well
below zero. Coldest temperatures will be found along the South
Platte River just below Denver and in the high mountain valleys
where readings could fall below 20 below zero overnight.
On Friday...much drier conditions and warmer temperatures are in
store as an upper ridge builds in from the west. Daytime highs
15-25 degrees warmer under clear to partly cloudy skies.
.LONG TERM...(Friday night through Thursday)
Issued at 310 PM MST Thu Jan 5 2017
Clear skies and light winds will lead to another cold night
tonight, though not as cold as Thursday night. An upper level
ridge will build over the Central Rockies this weekend. After a
cool Saturday, Sunday will be warmer. The warm air advection is
expected to produce clouds and perhaps a little mountain snow
Saturday night and sunday. If any snow occurs, it is expected to
be light.
A strong Pacific system will move onto the California coast Sunday
night and Monday. A strong jet will transport moisture inland.
Snow is expected to start Monday in the mountains and may become
heavy at times. A downslope flow will keep areas east of the
mountains dry and mild. Highs Monday may reach 60 in the Denver
area.
The Pacific system will move across the region early Tuesday.
Expect snow to continue in the mountains. A cold front is expected
to bring gusty winds Tuesday along with cooler, but still mild
temperatures.
A west to southwest flow aloft is expected to persist Wednesday
and Thursday. Pacific moisture will continue to be transported
into the region and will keep fairly high pops in the mountains.
For the Front Range and eastern plains, a downslope flow is
expected to continue to bring dry and mild conditions.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 853 PM MST Thu Jan 5 2017
Snow has pushed south and ceilings will continue to improve from
north to south tonight, though at a slower rate than expected.
Ceilings are expected to remain above 10000 feet. Eventually skies
will clear, resulting in a very cold night. Winds will remain
light, less than 10 knots.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
Wind Chill Advisory until 9 AM MST Friday for COZ042-044-048>051.
&&
$$
UPDATE...Kriederman
SHORT TERM...Baker
LONG TERM...Meier
AVIATION...Kriederman
Area Forecast Discussion...UPDATED
National Weather Service BROWNSVILLE TX
929 PM CST Thu Jan 5 2017
.DISCUSSION...Made a few, relatively minor, grid updates for the
rest of the overnight period. Updated winds with short-term
consensus blend, which seems to match up a bit better with obs and
neighboring office. Cut back on PoP`s through midnight, as front
has yet to generate much precip to our north. Added drizzle to the
weather mix after 09Z.
&&
.DISCUSSION...Updated for latest marine discussion below.
&&
.MARINE...Updated winds and gusts as mentioned above. Went ahead
and extended Small Craft Advisories for all of the Lower Texas
Coastal Waters through 12Z Saturday morning, as confidence is high
in adverse marine conditions continuing at least that long due to
tonight`s cold front and a reinforcing northerly surge on Friday
night. Still looks marginal for some gale-force gusts over the
Gulf on Friday night into early Saturday. Mentioned this
possibility in the advisory product but will hold off on a Gale
Watch at this time.
&&
.PREV DISCUSSION... /issued 555 PM CST Thu Jan 5 2017/
DISCUSSION...Updated for latest aviation discussion below.
AVIATION...Kept trend of previous set of TAF`s largely intact,
with just a few tweaks made. VFR conditions exist across the
flying area for the moment, but this will change within the next
few hours as a strong cold front impinges on the RGV. Winds back
to NE ahead of the front, but never really lay down, so potential
for fog looks a bit less; this is borne out in the MOS guidance.
Expect visibility to remain generally MVFR, and locally on the
lower end of this category in a band of rain showers expected to
develop just ahead of the front. Ceilings still expected to
deteriorate to IFR overnight, though.
Bumped up the arrival of the front proper by an hour at each of
the terminals, per latest RAP and HRRR model runs. Frontal passage
will bring gusty northerly winds...strongest at HRL. Periods of
light drizzle are also likely behind the front through at least
the morning hours of Friday. Guidance points toward ceilings
lifting back to MVFR Friday afternoon. This would appear
consistent with the lower-dewpoint values (along with colder
temperatures) moving in as the day progresses.
PREV DISCUSSION... /issued 255 PM CST Thu Jan 5 2017/
SHORT TERM (Tonight through Friday Night): Big story remains the
approach and passage of a strong cold front tonight. Guidance in
fairly good agreement this afternoon, with the front pushing through
the northern ranchlands and brush country around midnight and
through Brownsville before sunrise. Ahead of the front, light winds
and pooling of moisture may lead to the development of patchy fog,
primarily across the lower and mid Valley. Behind the front strong
northerly winds will develop, with the strongest winds occurring
along the coast and over the coastal waters. Temperatures will fall
quickly as the colder air surges into the region, with daily highs
occurring at midnight. By daybreak, temperatures will be in the lower
40s across the northern counties and temperatures will be falling
into the mid to upper 40s across the Valley. A wide diurnal range is
not expected during the day, with temperatures falling slowly or
holding steady. Light rain and drizzle will develop ahead of the
front and linger through the day.
Friday night, surface high pressure builds across north Texas
sending a reinforcing surge of drier and colder air across the
region. Have nudged temperatures down a degree or two Friday night
with model guidance trending cooler. This introduces freezing
temperatures across portions of Jim Hogg, Brooks, and Zapata
counties for several hours. A freeze warning may be needed for these
counties beginning early Saturday morning. Winds kick back up Friday
night with this reinforcing surge and the combination of the winds
and cold temperatures will lead to wind chill values in the 20s area
wide by sunrise. A Wind Chill Advisory will likely be necessary for
all of the CWA starting early Saturday morning as well. As the drier
air moves in, rain chances will taper off from west to east.
LONG TERM (Saturday through Thursday): The cold arctic air
entrenched over the south central United States Saturday will
modify and retreat northward Sunday as surface high pressure
across the Southern Plains moves eastward. Temperatures will be
cold Saturday as a result and the threat of freezing temps will
continue Sat night especially across the northern ranchlands
before a weak coastal trough develops offshore the lower Texas
coast Sat night into Sunday. Overrunning conditions will continue
to provide light rain across the coastal sections of the CWA
Saturday into Sunday as a result. An onshore flow will return
early next week and temperatures will gradually warm Sunday into
Monday with above normal temperatures returning Tuesday as a
frontal system develops across the central U.S. and moves
eastward. Warm air advection will continue through the rest of the
forecast period with a weak cold front moving into south central
TX and washing out Wednesday.
MARINE:
Now through Friday Night: A strong cold front is expected to surge
across the lower Texas coastal waters tonight, bringing strong
northerly winds and quickly building seas. A Small Craft Advisory
has been issued for the Laguna Madre and the near and offshore Gulf
waters and is in effect starting late tonight. Surface high pressure
building in over north Texas Friday night into early Saturday will
send a secondary surge of strong northerly winds across the region.
Sustained winds of around 25 knots are possible along with gale
force gusts and a gale warning may be needed for the Gulf waters.
Saturday through Tuesday...Strong north winds will prevail across
the coastal waters Saturday as the pressure gradient remains
strong across the western Gulf of Mexico. Small craft advisory conditions...with
possible gusts to near gale...will continue Saturday before the
winds and eventually seas diminish Sat night into Sunday as high
pressure across Texas moves eastward. Winds will veer to the
northeast Sat night and east Sunday before veering to the
southeast Monday as the surface ridge across the eastern United
States continues to move eastward and low pressure develops on the
lee side of the Rockies. Light to moderate southeast winds Monday
will veer to the south and increase Tuesday as the pressure
gradient increases across the lower Texas coast.
&&
.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...Small Craft Advisory for winds until 6 AM CST Saturday for
GMZ130-132-135.
Small Craft Advisory until 6 AM CST Saturday for GMZ150-155-170-
175.
&&
$$
This product is also available on the web at:
HTTP://WEATHER.GOV/RGV
53-Schroeder...Short-term/Marine
66...Long-term
Area Forecast Discussion
National Weather Service Hastings NE
525 PM CST Thu Jan 5 2017
.SHORT TERM...(This evening through Friday)
Issued at 150 PM CST Thu Jan 5 2017
Light snow across north central Kansas gradually tapered off
this morning, leaving dry conditions the rest of the day. When
all said and done storm total snow amounts have ranged from 1 to 4
inches across our area. An upper trough axis responsible for
generating the snow was working across the plains bringing
another surge of cold air. A 1032mb surface high pressure system
will settle in tonight, reinforcing the cold airmass and allowing
for a frigid night.
With high temperatures just in the single digits and teens today and
good radiating conditions tonight under the influence of the surface
ridge, look for temperatures to plummet well below zero overnight.
Model guidance has trended colder with lows and believe the colder
temperatures are the way to go with the bitter cold airmass in
place and new snowcover. Have followed closer to the RAP for lows
which are even colder than MOS with lows in the -5 to -15 range.
These temperatures combined with any wind at all will produce
wind chill values of -15 to -25 degrees and have expanded the wind
chill advisory across our entire cwa.
Although still cold, Friday will begin to see a slight moderation
in temperatures as the surface ridge axis slides southeast into
the southern plains states and heights begin to rise aloft as the
eastern trough begins to depart and upper ridging expands east of
the Rockies. The airmass moderates roughly 10C from today to Friday
and despite the snow on the ground, temperatures should rise near
or into the 20s in the slightly warmer airmass.
.LONG TERM...(Friday night through Thursday)
Issued at 150 PM CST Thu Jan 5 2017
Overall the extended models are in decent agreement with a dry
weather forecast over the weekend, with the next chance for
precipitation arriving in the Monday night/early Tuesday time
frame.
Saturday will see some cold air backing in from the northeast
associated with a strong 1045mb surface high building south from the
Upper Midwest Region along the Missouri River. There will be a
gradient in temperatures from northeast to southwest in this
thermal trough.
By Sunday, the airmass will be noticeably warmer with mid level
temperatures warming another 6C ahead of an approaching cold frontal
boundary. Temperatures should be near or in the 30s for highs and it
is shaping up to be a good snow melt day. The boundary which moves
in Sunday night is progged to stall and lift back to the north as
a warm front on Monday. Monday temperatures should be some of the
warmest of the next several days, tempered only by snowmelt/snow
on the ground.
A mid level shortwave trough and frontal passage Monday night may
generate a quick shot of light precipitation. The extended models
diverge more so for the middle/latter part of the workweek with the
strength and timing of another progressive trough and didn`t deviate
from ensembles. In a progressive pattern we will see varying
periods of warm air advection/cold air advection with readings
fairly seasonal or above.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Friday evening)
Issued at 525 PM CST Thu Jan 5 2017
VFR conditions expected to prevail. Winds will be light and
northwesterly becoming westerly towards morning and southwesterly
by afternoon Friday. Skies will be clear to mostly clear
throughout the period.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...Wind Chill Advisory until 10 AM CST Friday for NEZ039>041-
046>049-060>064-072>077-082>087.
KS...Wind Chill Advisory until 10 AM CST Friday for KSZ005>007-
017>019.
&&
$$
SHORT TERM...Fay
LONG TERM...Fay
AVIATION...Billings Wright
Area Forecast Discussion...UPDATED
National Weather Service Grand Junction CO
902 PM MST Thu Jan 5 2017
.UPDATE...
Issued at 901 PM MST Thu Jan 5 2017
Let the winter weather advisory for the Grand Valley (COZ006)
expire at 9 pm as the threat for significant accumulations has
ended. Very light snowfall remains in spots with the heavier
activity shifting southward. Anticipate very little if any
additional accumulations here.
Added southeast Utah (UTZ022) and the lower elevations of
southwest Colorado below 6500 feet (COZ021-022) to a winter
weather advisory through 09Z (2 am MST) as the cold front has
finally moved south of the area changing rain over to snow.
Expect 2 to 4 inches of snow in these advisory areas. A Winter
Storm Warning still remains for the southwest Colorado valleys
above 6500 feet, where higher amounts are anticipated. Adjusted
temperatures through that period into Friday morning as well to
fit current trends. The HRRR and GFS are both agreeing on the band
of heavier precipitation across the southern valleys through about
midnight but could be some lingering snow beyond this with the NAM
a little slower than the other models. Heavy rain and
thunderstorms were evident earlier this evening at Blanding,
Cortez and south of Durango with some reports of small hail.
Temperatures were hovering around 35 degrees with rain as the
precip type before changing over to snow as the convective element
helped to drive snow levels down as well as temperatures, with
readings around 32-33 in southwest Colorado and now 28 in
Blanding, Utah. Now that the cold air has arrived, any
precipitation should be all snow with maybe still a mix in extreme
southeast Utah before switching over. Forcing is great enough for
some heavier bands of precipitation through early Friday morning.
UPDATE Issued at 556 PM MST Thu Jan 5 2017
Added mention of isolated thunderstorms across southeast Utah and
southwest Colorado valleys as the convective element is very much
in play along the cold front boundary. The last few scans of
visible satellite showed some convective cloud tops in this area
with gravity waves across the central portions of western Colorado
and eastern Utah. Snow is tapering off to a light snow in Moab and
Grand Junction with the heaviest snow shifting towards areas south
of Delta and Montrose. IR satellite is showing some banding
moving into southeast Utah, which matches up well with the HRRR
model. This banding quickly shifts south towards the southeast
Utah and southwest Colorado valleys along the southern border with
Arizona and New Mexico for some enhanced precipitation.
Temperatures are the concern in the southern valleys, as the cold
front looks to be currently hanging over the southwest San Juans
and Abajos and not quite making it into the southern valleys.
Temperatures are still in the upper 30s in Blanding, Utah and
Durango with mid 40s in Cortez. Temperatures are expected to fall
in the southern valleys with this frontal push between 7 pm and 9
pm and quickly drive southward over the border between 10 pm and
11 pm. Expect to see some heavy bursts of rain changing over to
snow with some isolated thunder through 10 pm for the southern
valleys. Thinking the timing of the cold air with the
precipitation will limit significant accumulations over southeast
Utah but will keep an eye on this area this evening. Also will
continue to keep an eye on the southwest Colorado valleys, where
better snow accumulation will fall above 6500 feet, but
warmer temperatures and timing of cold air with precipitation will
be an issue for areas below 6500 feet. Areas north and along the
front in the central and southern mountains, especially the San
Juans and Abajos, should see the heaviest snowfall this evening in
the much colder air mass in proximity of the stronger jet aloft.
&&
.SHORT TERM...(Tonight through Friday night)
Issued at 402 PM MST Thu Jan 5 2017
This multi-day winter storm continues to plague parts of eastern
Utah and western Colorado. Forecast challenge has continued to be
the latitude of the cold front vs forecast models. Current
satellite and short term models indicate snow will continue over
the I-70 corridor of eastern Utah and western Colorado through at
least 6 or 7pm this evening. Forecast models indicating strong
convergence zone across the southern San Juans and Bluff to
Durango to Pagosa Springs developing tonight between 8pm and
midnight. This means heavy snow rates and/or rain rates if below
5500 ft. Decided to cancel advisories for below 6500 ft in
thinking most precip will be ahead of the below freezing air.
These locations between 5500 and 6500 ft may still see some light
snow accumulations but not 2 to 6 inches as we were expecting
before this front slowed down. Snow will lighten up after 2am
Friday morning but light snow still possible in the southwestern
CO and central CO mountains through about 8am Friday. Skies will
quickly clear out and temperatures will substantially drop. Did
put wind chill warning out for NW CO for tonight through Friday
morning for wind chills 25 to 35 below zero. Other locations will
see below zero wind chills but remain above advisory and warning
criteria. Bundle up!
.LONG TERM...(Saturday through Thursday)
Issued at 402 PM MST Thu Jan 5 2017
Ridging builds in Friday and Saturday for a short break before
moisture substantially increases again from the Pacific on
Sunday. The next big storm in the eastern Utah and western
Colorado high country is progged to move in on Monday with a
potential transition to snow in many areas on Tuesday. No long
break is expected in the weather for the next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 440 PM MST Thu Jan 5 2017
A strong winter storm continues to pass through the heart of
Eastern Utah and Western Colorado, resulting in heavy snow in the
mountains with moderate snow in the valleys. Visibility is being
reduced by this moderate to heavy snow with IFR to LIFR conditions
possible at a majority of the terminals through at least midnight.
Conditions will improve greatly tomorrow morning as the storm
system exits the area and a cold dry airmass settles in.
Forecast confidence is moderate to high.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Winter Weather Advisory until 2 AM MST Friday for COZ021.
Winter Weather Advisory until 5 AM MST Friday for COZ011-020.
Winter Storm Warning until 5 AM MST Friday for COZ009-010-
012>014-017>019-021>023.
Winter Weather Advisory until 3 AM MST Friday for COZ022.
Wind Chill Warning until 5 AM MST Friday for COZ001.
Winter Storm Warning until midnight MST tonight for COZ007-008.
UT...Winter Weather Advisory until 2 AM MST Friday for UTZ022.
Winter Weather Advisory until 5 AM MST Friday for UTZ028.
&&
$$
UPDATE...MDA
SHORT TERM...JAM
LONG TERM...JAM
AVIATION...Larry
Area Forecast Discussion
National Weather Service Goodland KS
635 PM MST Thu Jan 5 2017
.UPDATE...
Issued at 626 PM MST Thu Jan 5 2017
&&
.SHORT TERM...(This evening through Friday)
Issued at 200 PM MST Thu Jan 5 2017
Early afternoon WV imagery and RAP upper level analysis shows a
trough across the Northern Plains digging southward into the
Central High Plains. A plume of moisture extends across the
Central Rockies over our CWA. At the surface 1027mb high pressure
is building south and the southern extent of this is over much of
our CWA.
Tonight-Friday: Temperatures are trending a bit cooler this
evening with persistent CAA into the region. Lowered overnight
lows one to three degrees as a result; however, these lows will be
dependent upon cloud cover. High temperatures Friday could be
complicated by lingering snow pack despite arctic high pressure
moving east of our CWA and sunny skies prevailing. Slight
adjustments downward were made mainly in our north (where 3-5"
amounts occurred). Locations in our north may struggle to reach
20F.
Regarding Wind Chill Advisory tonight-Friday morning: Arctic high
pressure will continue to slide south over our region. This will
combine with lingering snow pack and clearing skies to provide
ideal radiational conditions for locations north of I-70. I
trended overnight lows down with this in mind, but limited changes
south of I-70 as mid to high clouds could provide enough
insulation to limit cooling. Locations in the south will likely
still see lows drop to near zero if not below despite clouds.
Upgraded the advisory to a warning in the northwest counties based
on the latest obs and hi-res data trends. We should see at least
a few hours of ideal radiational conditions combined with 7 to 11
knot winds to allow wind chills to fall into the 25 to 30 below
zero range. I also added Gove and Logan to the advisory area based
on recent obs and trends.
.LONG TERM...(Friday night through Thursday)
Issued at 1220 PM MST Thu Jan 5 2017
Friday night through Saturday night...high cloudiness moves in from
the west Saturday ahead of an approaching upper level ridge of high
pressure. These high clouds increase in coverage Saturday night. Low
temperatures Friday night a few degrees either side of zero. High
temperatures Saturday in the mid 20s to low 30s. Low temperatures
Saturday night in the single digits above zero.
Sunday...should see a break in the clouds during the morning before
increasing from the west late in the day. A decrease is then
expected overnight. High temperatures in the mid 30s east, mid 40s
west. Low temperatures in the low to mid 20s.
Monday...upper level ridge axis moves across the area during the day
with some weak troughiness during the night. High temperatures warm
into the mid 40s east to low/mid 50s west. Low temperatures in the
mid 20s to low 30s.
Tuesday...cooler temperatures expected with decreasing cloudiness
from west to east in the afternoon. Maybe some high clouds in the
west during the night. Afternoon temperatures in the mid 40s to
around 50 with lows in the upper teens to low 20s.
Wednesday...forecast area under near zonal flow aloft with some high
clouds possible. Afternoon temperatures again in the mid 40s to
around 50/low 50s with lows in the low to mid teens.
Thursday...dry forecast expected with a general near zonal flow and
some mid and/or high cloudiness possible. High temperatures similar
to Tuesday and Wednesday with lows in the low to mid teens.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 427 PM MST Thu Jan 5 2017
VFR conditions will continue through the evening and overnight at
both TAF sites. Winds will gradually shift from northwesterly to
southwesterly remaining less than 10 knots through the overnight
hours at both sites.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...Wind Chill Warning until 10 AM CST Friday for KSZ001.
Wind Chill Advisory until 9 AM MST /10 AM CST/ Friday for
KSZ002>004-013>016-027>029.
CO...Wind Chill Warning until 9 AM MST Friday for COZ090-091.
Wind Chill Advisory until 9 AM MST Friday for COZ092.
NE...Wind Chill Warning until 9 AM MST /10 AM CST/ Friday for
NEZ079>081.
&&
$$
UPDATE...TL
SHORT TERM...DR
LONG TERM...99
AVIATION...TL
Area Forecast Discussion
National Weather Service Houston/Galveston TX
845 PM CST Thu Jan 5 2017
.DISCUSSION...
Latest observations show cold front almost to the Upper Texas
Coast. Behind the front temperatures have dropped into the 40s
with the freezing line over north Texas. Based on water vapor
imagery the next strong jet streak is coming into the Great Basin.
This is the system that will bring snow to the Southern Plains and
across to the SE U.S/Carolinas. Looking at latest HRRR model
trends and objective analyses, look for isentropic lift to begin
to increase at 295K between 925-850mb. Frontogenesis in 925-850mb
increases late Friday but by this time moisture will be rather
limited for any precip. The best chances for rain/drizzle will be
starting later tonight through much of the the morning Friday.
Subsidence will increase along with drying late Friday as 850mb
front pushes into the Gulf of Mexico. Since both frontogenetic
lift and large scale quasi-geostropic ascent will be weakening
Friday night, there is no longer a mention of any frozen
precipitation.
IF there was an opportunity for frozen precipitation, it would be
Friday morning for MAYBE a couple of hours from say 5am to 8am
across areas from College Station to Huntsville. Model soundings
indicate isentropic lift and a saturated layer from 925mb up to
750mb with a sub freezing layer from surface up to 875mb. So there
is a solid 3500ft sub freezing layer only that the near surface up
to 2000 feet is dry as surface dewpoints drop into the low 20s.
Thermodynamic web bulb processes could support an ice
pellet/sleet or two but there would have to be a lot of
evaporation to cool and moisten this layer. Surface temps will
only be 29-32F so may be hard to get cold enough surfaces for even
freezing rain/drizzle. There is very low confidence in these
processes happening. So much so that mention of frozen precip will
not be in the forecast. The only other adjustments to the forecast
were for temperatures trends and keeping with obs and short range
guidance. It does look like Saturday morning will be quite cold
with low temperatures in the 20s for most areas.
Overpeck
&&
.PREV DISCUSSION... /ISSUED 539 PM CST Thu Jan 5 2017/
AVIATION...
Ahead of the cold front passing through the area right now,
conditions have improved to MVFR. In the immediate vicinity of the
front is a brief area of clearing, which is currently affecting
our northern sites, and should for no more than the next few
hours. Already see signs of ceilings right around 3k feet, give or
take a few hundred feet filling in this area of clearing, so only
give tempo improvement as there is expectation for this area of
clearing to continue to erode through the evening. Behind this
cleared out area are more MVFR ceilings, and so the entire area
returns to that overnight and into tomorrow.
Through this period, blustery winds out of the north will
continue. Potential for drizzle or light showers from DWH
coastward returns either very late tonight or tomorrow. Another
concern tomorrow will be a layer of saturated air from about
1500-4000 feet with temperatures a little below freezing -
conditions ripe for supercooled water droplets, and could
potentially cause light riming issues. There may start to be some
scattering of clouds right at the end of IAH`s extended period at
07/06Z, but confidence is not yet high enough on that timing to
include for the sake of a couple hours at most.
Luchs
PREV DISCUSSION... /ISSUED 400 PM CST Thu Jan 5 2017/
DISCUSSION...
A cold front will continue to push through SE Texas this
afternoon with some isolated light rain showers continuing generally
south of Hwy 59. Breezy offshore winds at the surface will usher
in a much cooler air mass in the wake of this front. Overnight
tonight and into Friday, strong SW flow at around 850mb will
create some isentropic lift over a shallow cold layer, bringing
light stratiform rain/drizzle over much of the area. Some of our
far northwestern counties will likely drop below freezing around
sunrise on Friday, but no precipitation is expected that far north
and west during that time. By the time the isentropic lift brings
showers/drizzle into the Brazos Valley on Friday, temperatures
should have had the chance to warm into the mid 30s. If the
showers do make it far enough northward while surface temperatures
are below freezing, some wintry precip may be possible (although
very unlikely). The strong NW winds bringing in the cold, dry air
mass at the surface may cause some of the precip to evaporate
before it reaches the ground. Even if any wintry precip does
manage to occur, no accumulation is expected. No wintry
precipitation has been included in our grids as we think a rain
shower/drizzle combination is the most likely outcome.
After Friday, isentropic lift is lost and the air mass dries out
considerable. The weekend will be cold and dry, with temperatures
warming quickly at the beginning of next week with strong
southwesterly low level flow overhead. Another cold front is
forecast to approach SE Texas around midweek next week but may or
may not even make it off the coast. 11
MARINE...
The passage of a cold front off the upper Texas coastline this
evening will usher in strong offshore winds that will persist
through Saturday. All water Small Craft Advisory level winds will
commence this evening and last through Friday evening...weakening
over the bays to Cautions and remaining Advisory over the Gulf
Friday night through Saturday morning. Much colder air over warmer
waters will likely allow flags to remain hoisted over the far
offshore waters until Sunday afternoon. Bays and seas will quickly
respond through the overnight hours...rough bay conditions late
tonight through Saturday morning with elevated seas to near an
average 7 feet nearshore...10 feet offshore...through the day Friday
and into Saturday.
Tides are currently within a few inches of a foot above normal.
Levels will likely flip to be around a foot or slightly more below
normal through Friday. A forecast more easterly component to the
offshore flow will likely minimize the threat for low water issues
within the local upper reaches of our bays...ship channels and
inlets. 31
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 30 37 24 42 25 / 10 10 10 0 0
Houston (IAH) 37 40 28 44 28 / 30 30 20 0 0
Galveston (GLS) 44 45 34 45 37 / 40 40 20 10 0
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...Small Craft Advisory until 6 PM CST Friday for the following
zones: Galveston Bay...Matagorda Bay.
SMALL CRAFT SHOULD EXERCISE CAUTION from Friday evening through
Saturday morning for the following zones: Galveston Bay...
Matagorda Bay.
Small Craft Advisory until noon CST Saturday for the following
zones: Coastal waters from Freeport to the Matagorda Ship
Channel out 20 NM...Coastal waters from High Island to
Freeport out 20 NM...Waters from Freeport to the Matagorda
Ship Channel from 20 to 60 NM...Waters from High Island to
Freeport from 20 to 60 NM.
&&
$$
Discussion...39
Area Forecast Discussion...UPDATED
National Weather Service Huntsville AL
935 PM CST Thu Jan 5 2017
.NEAR TERM...(Tonight)
Issued at 935 PM CST Thu Jan 5 2017
Cold surface high pressure sprawled over the central High Plains,
continued to bring colder air across the Deep South. A frontal
boundary denoting the leading edge this surge extended across
western VA/NC to central GA, then meandering to the Mississippi
Delta. Earlier high temperatures across the Tennessee Valley in the
upper 30s/low 40s continued to cool - now ranging in the low/mid 30
and northerly winds of 5-10 mph. Around the region, no weather of
consequence locally was occurring as of this writing, but there were
reports of light snow over portions of middle and eastern TN. Our
local profiler also indicated precip possibly falling, but was
evaporating or sublimating before reaching the surface.
With the high pressure at the surface...a strong zonal flow continued
east of Rex-type blocking off of the west coast. Within this flow
over parts of 4-Corners region, some thunder was noted. Upper level
energy associated with this convection, and other weak disturbances
are forecast to move across the region during the overnight and
Friday, and keep chances of wintry weather in the forecast. A more
significant area of low pressure is also expected to form across the
northern Gulf later Friday and move northeastward towards the
Atlantic coast during the weekend. This forecast area will be in
between this southern system and weaker upper level disturbances
passing by.
Night-time temperatures will continue cooling, falling below freezing
by the late evening with subfreezing temperatures expected areawide
overnight and for much of Fri. The challenging part is the when and
where light snow will fall. Given subfreezing temperatures, snow
(especially if it persists) could start accumulating, especially on
elevated surfaces. New NAM output was on dry trend for the area until
late Fri AM, when it picks up on the western disturbances and brings
precip across the area - especially north of the TN River. The HRRR
and the RAP were hinting at precip developing before daybreak over
the forecast area. Given the above (subfreezing temperatures plus
wintry precip), will keep the Winter Weather Advisory as is for now.
.SHORT TERM...(Friday through Saturday)
Issued at 316 PM CST Thu Jan 5 2017
With the upper wave beginning to traverse ewd over the region late Fri
morning, light snow is xpcted to increase across srn mid TN into nw
AL, as mid/upper forcing develops with the approaching shrtwv.
Moisture depth near/above H85 is also xpcted to increase out of the
w during the day Fri. With all of the temp profiles below the zero
degree line, light snow should continue through the day as the upper
shrtwv continues to translate ewd. Light accumulations around 1 inch
are possible from the afternoon hrs into the evening period, with
locally higher amounts possible in the elevated terrain. Some of this
moisture/light snow may develop from the s as a low pressure system
moves ewd across the nrn/ern Gulf region. However, most of this
energy looks to remain just s of the local area. A Winter Weather
Advisory has been issued starting Fri afternoon and continuing
through the evening period. Any lingering light snow should then
taper off from the w late Fri night, as drier mid level air begins to
spread into the area.
Very cold conditions are xpcted to remain in place heading into the
weekend period, with wind chill readings Sat morning in the single
digits. Afternoon temps may struggle to reach the freezing mark on
Sat, with highs only around 30F. Skies will at least start to clear
as the weekend progresses, as a large dome of high pressure out of
the Plains states builds ewd into the TN/OH Valley regions going into
the new week.
.LONG TERM...(Saturday night through Wednesday)
Issued at 316 PM CST Thu Jan 5 2017
Synoptic pattern will transition to quite a progressive and active
one beginning early next week. Large cold dome of high pressure
will drift southeast through the central Appalachians Sunday into
Monday. After a very cold Sunday and Monday morning in the teens and
20s, a rapid warmup is anticipated Monday into Tuesday as southwest
surface-850 mb flow develops. The next in a series of upper level
impulses will cut east through the southern Plains Monday and into
the lower MS and TN valleys by Tuesday night into Wednesday. Ample
QG-dynamical support, moisture transport and increasing convective
instability (especially elevated), will yield an organized linear
MCS along the front. Model fields suggest a rather lengthy period
of trailing stratiform precipitation as well into Wednesday morning.
Will go with likely POP Tue Night into Wed from west to east. The
longer term pattern more than hints at a rather mild period beyond
day 7 as amplification of the southeast coastline ridge and
southwest U.S. trough take place.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 545 PM CST Thu Jan 5 2017
VFR weather should continue through early Fri AM across the
Tennessee Valley. An approach of several upper air systems, and
increase in lower level moisture values will bring a slight chance
of precipitation to the region - mainly from the predawn into much
of Fri. Precip placement per forecast models was a hit/miss affair
for the period, therefore kept a formal -SN mention out of the TAFs.
That being said, a few flurries remain possible across the area
during the period. Better snow chances are expected on Fri afternoon
as deeper moisture and stronger lift is realized, but chances still
too low for inclusion in TAF. Did lower CIG values to MVFR,
especially at KMSL; the terminal is closer to a passing system.
&&
.HUN WATCHES/WARNINGS/ADVISORIES...
AL...Winter Weather Advisory from 3 PM Friday to 3 AM CST Saturday for
ALZ006>010-016.
Winter Weather Advisory from noon Friday to midnight CST Friday
night for ALZ001>005.
TN...Winter Weather Advisory from noon Friday to midnight CST Friday
night for TNZ076-096-097.
&&
$$
NEAR TERM...RSB
SHORT TERM...09
LONG TERM...17
AVIATION...RSB
For more information please visit our website
at weather.gov/huntsville.
Area Forecast Discussion
National Weather Service Jacksonville FL
837 PM EST Thu Jan 5 2017
.UPDATE...
Forecast on track with fairly quiet conditions as weak High
pressure ridge remains in place while upper level winds push a few
mid/high clouds across the region overnight. Enough radiational
cooling into the mid/upper 40s may provide enough crossover below
afternoon Td`s to produce some patchy fog with vsbys in the 1-5
mile range mainly across NE FL, while even some of the Hi-Res HRRR
models are suggesting some locally dense fog across the Suwannee
River Valley of North Florida, but this will be dependent on how
much mid/upper level cloud cover occurs towards morning as more
cloud cover will hinder cooling and fog formation. On Friday still
expect mid/high clouds to slowly thicken and lower with only low
rain chances pushing into inland SE GA and the Suwannee River
Valley during the mid-late afternoon hours while the rest of the
region remains dry. Cloud cover may remain thin enough to allow
for some insolation to push Max Temps into the lower/middle 70s
across NE FL while only 60s are expected across SE GA.
&&
.AVIATION...
Still expect mainly VFR tonight until around 09z, when enough
surface cooling should occur to trigger MVFR vsbys in FOG in the
3-5 mile range except for SSI, some lower vsbys possible at the
NE FL TAF sites but not confident enough to forecast any IFR vsbys
yet. Any AM fog should disperse by 14Z still leaving just
scattered low clouds and broken high clouds through most of the
day with light winds.
&&
.MARINE...
Offshore flow at 10 to 15 knots will continue tonight with seas
2-4 ft will become SELY later on Friday. No headlines expected
until big wind increases expected this weekend.
Rip Currents: Low Risk.
&&
.PRELIMINARY POINT TEMPS/POPS...
AMG 46 62 41 46 / 0 30 90 50
SSI 51 63 45 50 / 0 10 80 70
JAX 49 70 47 51 / 0 10 90 60
SGJ 50 70 54 59 / 0 10 90 70
GNV 48 73 49 55 / 0 10 90 60
OCF 49 75 53 59 / 0 10 80 70
&&
.JAX WATCHES/WARNINGS/ADVISORIES...
FL...None.
GA...None.
AM...None.
&&
$$
Hess/Guillet/Corless
Area Forecast Discussion
National Weather Service Omaha/Valley NE
511 PM CST Thu Jan 5 2017
.SHORT TERM...(tonight through Sunday)
Issued at 305 PM CST Thu Jan 5 2017
Temperatures over the next few days, in conjunction with wind chill
values, will provide the main forecast challenges in this period.
Water vapor satellite imagery in combination with recent RUC model
initializations indicated an elongated trough extending
west/southwest from a closed low over Quebec back into the
northern parts of Utah and California. There were several ripples
in the flow moving along in the fast zonal flow, but these should
stay to our south tonight and Friday. Surface analysis early this
afternoon showed cold high pressure in place across much of the
Plains. The high pressure will slide southeast and the pressure
gradient should relax compared to what it has been today. Some
clouds may linger into the evening, then diminish. Some flurries
are not out of the question, due to favorable temperatures in the
cloud layer for small ice crystal growth, but should not be
significant enough to mention at this time. Have gone with lows
ranging from around 3 below to 9 below zero, with the coldest
values generally from Albion and Columbus toward Lincoln and
Beatrice. Wind chill values in this area should also be around 20
below later tonight, so after coordinating with bordering
offices, will issue a wind chill advisory for the area generally
along and west of a line from Albion to Falls City.
Due to a cold start Friday morning, we only expect temperatures
to recover into the upper teens and lower 20s Friday afternoon.
Highs Saturday should again be mostly in the upper teens to lower
20s. On Sunday, increasing south/southwest low level flow should
help push highs into the upper 20s and lower 30s.
.LONG TERM...(Sunday night through Thursday)
Issued at 305 PM CST Thu Jan 5 2017
Blocking pattern with split mid tropospheric flow will be in place
at the start of this period. We should mostly be under the
influence of the southern stream energy, but model consensus drops
of by the mid part of next week. The 12Z runs of the GFS and ECMWF
are in reasonable agreement, but the Canadian model would allow
colder air to move in from the north.
A cold front should push into the area from the northwest Sunday
night, but then stalls as low pressure strengthens along the lee
slopes of the Rockies. Some precipitation, mainly light snow,
appears possible by Monday night as low pressure tracks from
eastern Colorado across Kansas and then to near the Illinois/
Iowa border by mid day Tuesday. Mixed precipitation seems possible
Tuesday morning as temperatures warm through mid day. The highest
snow chances at this time are across the northern and eastern
parts of the forecast area. There also appears to be some
potential for precipitation toward Friday of next week.
Highs from Monday through Thursday in our area look to be mainly
in the 30s, with lows in the teens and 20s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 509 PM CST Thu Jan 5 2017
A stratocu deck at about 2500-3500ft is breaking and moving
eastward, and VFR conditions are largely expected through the TAF
cycle. Would not rule out a flurry at any site for the next 1-2
hours, but any flurries would be very light and brief and would
not accumulate or cause restricted visibility. Northwest winds
will decrease to around 5-10mph tonight, backing to westerly and
then southwesterly through Friday.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Wind Chill Advisory from 11 PM this evening to 10 AM CST Friday
for NEZ030-042-050-065-066-068-078-088>093.
IA...None.
&&
$$
SHORT TERM...Miller
LONG TERM...Miller
AVIATION...Mayes
Area Forecast Discussion
National Weather Service Nashville TN
918 PM CST Thu Jan 5 2017
.UPDATE...
FOR EVENING DISCUSSION.
&&
.DISCUSSION...
Snowfall has moved out of the northern middle TN area. However, a
few snow flurries still remain across the Plateau. Some slick
spots on area roadways across northern middle TN have been
reported. Thus, will go ahead and allow the advisory to continue
until midnight.
Went ahead and issued an SPS for the entire middle TN area. This
product was issued to address the potential for more snowfall on
Friday. Latest Hrrr shows light snow reaching western areas toward
12z, with models in general agreement. But, there are differences
in the location of the mid level pva during the morning hours. The
nam spreads light snow across much of the mid state during the
morning while the gfs/euro lean more toward confining the moisture
across our southern areas.
So, mentioned accumulation in the SPS and included a dusting
north of i-40 with up to 1 inch being possible across southern
portions. The light snow may continue across the Plateau Friday
evening when an additional one half inch being possible.
Decided to refrain from a 2nd period, impact based advisory. Given
that the likelihood of an inch or more of snow lacks confidence. A
1st period impact based advisory seems more appropriate.
Nevertheless, the sps does stress accumulation potential across
the south beginning just after sunrise Friday morning.
&&
.AVIATION...
00Z TAF DISCUSSION.
CKV and BNA terminals should experience predominate light snow or
tempo light snow thru 06/02Z to 06/03Z respectively. Light snow
should begin at CSV by around 06/01Z. Despite light snowfall,
vsbys could fluctuate between VFR/MVFR at terminals. Light
snowfall potential could persist at CSV thru 06/22Z also. With
all this in mind, there will be some potential for icing on
surfaces as temps are expected to continue to be below freezing
sfc and aloft thru 06/24Z. A cold air advection sfc pattern and
moisture aloft streaming from the sw will continue to support VFR
ceilings at most locations thru at least 06/20Z, expect CSV where
MVFR ceilings could form between 06/07Z and 06/22Z.
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until midnight CST tonight FOR Cannon-
Cheatham-Clay-Cumberland-Davidson-De Kalb-Dickson-Fentress-
Grundy-Jackson-Macon-Montgomery-Overton-Pickett-Putnam-Robertson-
Rutherford-Smith-Sumner-Trousdale-Van Buren-Warren-White-
Williamson-Wilson.
&&
$$
DISCUSSION......21
AVIATION........31
Area Forecast Discussion
National Weather Service Pittsburgh PA
820 PM EST Thu Jan 5 2017
.SYNOPSIS...
A fast-moving system will spread snow across the region tonight,
with the highest accumulations expected south of I-70. Bitterly
cold conditions will continue through the weekend.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Between 6pm and 8pm, radar coverage of snow has rapidly
diminished, although automated surface observations show that
snow is still falling across much of the forecast area. Still,
surface visibilities indicate that snow intensity has dropped
overall. The HRRR has been the best model this evening with
snowfall trends, considering the RAP has looked similar to the
synoptic models which kept snow continuing in the forecast a few
hours longer than current observational trends. With the 8pm
update, the main change to the forecast was to drop pops and snow
totals a bit along the western half of the region, although the
decreases across the eastern half of the forecast were not as
great. In fact, the latest update may not have been aggressive
enough in dropping snowfall totals considering the current radar
trends. Did not make any changes to the advisories considering
snow continues to fall across nearly all locations under an
advisory.
It was noted earlier in previous discussions that the HRRR and
RAP were both very aggressive with clearing skies in Ohio counties
by sunrise. Some clearing is starting to make its way into Indiana
and northwest Ohio. If the clearing does make its way into eastern
Ohio counties, the combination of clearing and fresh snow cover
would result in colder overnight temperatures than are currently
in the forecast. Some model guidance indicates that the
possibility of a location dropping to zero cannot be ruled out.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
Cold upper trough will persist through the weekend but dry
advection should limit further snowfall accumulation outside of
terrain and counties adjacent to the lakes until Sunday. Model
guidance has been slowly trending northward with the advancement
of a low pressure, set to pass through the Carolinas Fri
night/Sat but as of now, it still appears this system will miss
us.
The core of the coldest air will be situated over the region on
Sunday as the trough amplifies with ridging from the west. During
this time frame, we may once again see a chance for scattered snow
showers as the winds shift more northwesterly before upper
ridging takes it`s place.
Temperatures will continue to trend well below average with fresh
snow pack and clear skies likely to support lows in the single
digits. With confidence continuing in the possibility of wind
chill values -10F in the ridges, have maintained the HWO mention.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Strong warm air advection is expected ahead of low pressure that
will emerge from the Plains on Tuesday. An initial wintry mix will
change to all rain later Tuesday into Tuesday night as temperatures
rise through Tuesday night ahead of an approaching cold front for
Wednesday. Rain with the cold front will end as snow showers
Wednesday night. Weak high pressure should bring a dry day for
Thursday.
&&
.AVIATION /01Z FRIDAY THROUGH TUESDAY/...
Visibilities as of 01Z may be the lowest that terminals will drop
to for the rest of the night, as the general trend of radar is for
snow intensity to decrease. Visibilities are already returning to
VFR across Ohio, and this trend should continue overnight. Any
chance for LIFR/VLIFR visibilities in heavier snow is dropping
rapidly, with MGW the most likely site for heavier snow. While
LBE/MGW may hold onto MVFR ceilings into Friday morning, think the
rest of local airports should return to VFR conditions by sunrise.
.OUTLOOK...
Scattered restrictions in snow showers are possible in cold
northwest flow Saturday into Sunday.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...Winter Weather Advisory until 7 AM EST Friday FOR MDZ001.
OH...Winter Weather Advisory until 3 AM EST Friday FOR OHZ057>059-
068-069.
PA...Winter Weather Advisory until 7 AM EST Friday FOR PAZ031-
073>076.
WV...Winter Weather Advisory until 7 AM EST Friday FOR WVZ012-021-
509>514.
Winter Weather Advisory until 3 AM EST Friday FOR WVZ003-004.
&&
$$
Area Forecast Discussion
National Weather Service Mount Holly NJ
920 PM EST Thu Jan 5 2017
.SYNOPSIS...
An area of low pressure will develop along the mid-atlantic
coastline tonight and will move out to sea on Friday. Another area
of low pressure will form in the eastern Gulf of Mexico on Friday
and move northeastward staying offshore on Saturday. High pressure
will build into the region on Sunday and move east of the region
by Tuesday. On the backside of the high, a warm front will move
through the region late Tuesday into Wednesday. This will be
followed by a cold frontal passage later in the week.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
An area of light to locally moderate snow has developed over parts
of SE PA and is moving into west-central NJ. Light accumulations
are possible during this time. Once this first wave moves through
the region, there may be a slight break before a secondary wave
develops and moves through the region after midnight.
Latest HRRR shows a swath of 2-3" snow from across SE PA through
central NJ, pretty much in line with where the Winter Weather
Advisory is in effect. Could be some spotty areas that pick up 4".
Will go ahead and bump up snowfall totals by a few hundredths of
an inch or so. For the most part, the difference in the forecast
will be negligible, but some areas, especially north of I-78, that
previously mentioned around 1 inch may be bumped up to 1-2". No
plans to expand the Winter Weather Advisory at this time as snow
totals in those areas are still below Advisory criteria. The fly
in the ointment is that a few bands of snow could impact Sussex
county in DE, and they could come close to WWA criteria.
Low pressure continues to develop off the Mid-Atlantic coast
tonight and will lift away from the region towards daybreak
Friday.
The snow will quickly end from west to east between about 2-4 AM
in our western most zones and 4-6 AM in our eastern zones.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/...
The offshore low will continue to deepen on Friday as it moves
northeastward and well off the Mid-Atlantic coast. Any lingering
light snow or flurries should be over before sunrise. With
temperatures in the 20s, untreated roads will likely remain slippery
for the start of the morning rush even after the snow has ended.
Breaks in the lower clouds will develop from west to east as the
flow turns northwest behind the offshore low and advects drier air
into the region. Variable cloudiness is expected tomorrow as the
area will still be affected by mid and high clouds toward the based
of the upper trough. There will also be additional stratocu
development during peak heating. High temperatures range from the
20s in the higher terrain of northeastern PA and northwestern NJ to
the mid 30s along and east of I-95.
&&
.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
Friday night through Saturday night:
Several inches of accumulating snowfall likely for coastal areas
on Saturday with a sharp cutoff further northwest...
Winter Storm Watch for Atlantic, Cape May New Jersey and Sussex
Delware for early Saturday morning through the day Saturday.
An area of low pressure will be developing in the Eastern Gulf of
Mexico and move northeast and be located off the southeast coast
Friday night. Modeling today has trended the low pressure track
closer to the coast. One factor toward this appears to be a stronger
shortwave over the Tennessee Valley on Friday. The 500 mb trough
over the past 24 hours has trended deeper on the GFS and slightly
deeper on the ECMWF, also indicators of a track trend NW.
A typical trend in modeling a day or so before a coastal low is to
move the track even more northwestward. However, this trend may not
occur for a few reasons.
1. Based on a strong high pressure system building into New
England.
2. Limited spacing between the two waves that would result in more
confluence and a lower probability for amplification.
3. A limited amount of ridging along the east coast. For the most
part the pattern has been for a strong mid-level ridge along the
east coast which does not look to be present in this case.
A very tight cutoff will be present between those that see
accumulating snow and no snow at all, perhaps even a partly sunny
day NW of Philly. Model resolution is likely to course with the
cutoff in this case as well. Ensemble trends have basically followed
the respective operational models the last few days.
Temperatures will be cold as well with CAA continuing into the region.
Likely a couple of degrees under MET/MAV guidance for highs and
lows. lingering snow cover from Friday also factored in toward the
slightly colder forecast.
For QPF, used a blend of the NAM, SREF ECMWF and WPC guidance to
account for any additional shift northwestward but not in a position
to go too far northwest given the factors mentioned above.
Snow growth looks favorable on the soundings in the -10 to 20C
range along with some lift present as well. With temperatures in the
20`s, ratios should be around 15:1. Not likely to be any higher
since this is a coastal low.
Snow amounts (Saturday only)
Georgetown 4-6
Dover 2-4 Atlantic City 4-6
Millville 2-4
Easton 2-4
Ocean County NJ 2-4
Wilmington and Philadelphia 1 or less
Mount Holly 1-2
Cape May 4-6
Any shift the storm track in the next 24 hours could have a high
impact on the forecasted totals. Uncertainty is still present
given how little track changes can lead to a wide range of
snowfall. The cutoff is likely going to be sharper than indicated.
Sunday and Sunday night : High pressure will build into the region
resulting in clearing conditions. Another cold day with highs in the
20`s and lows in the 10`s or colder for the Southern Poconos. Likely
colder than MET/MAV in areas that get snow cover.
A cold surface high (1040+ mb) moves onto the East Coast Monday. The
surface pressure gradient will relax in this regime (i.e., winds
should lower significantly Monday). Temperatures will remain cold,
with highs near or below freezing in much of the area.
By Tuesday, a shortwave trough will eject from a nearly-stationary
upper low off the Pacific Northwest Coast into the northern plains.
Downstream ridging will occur in much of the eastern U.S., with
strong low-level warm air advection serving to amplify the ridge. A
baroclinic zone will become established roughly from the Upper
Midwest southeastward to near the Mason-Dixon Line Tuesday lifting
northward gradually through Wednesday. However, remnant cold near-
surface air will be slow to modify in this regime. With strong
isentropic ascent atop a shallow layer of cold air, developing
precipitation late Tuesday into early Wednesday morning may start
off as a wintry mix. As sustained warm air advection continues into
Wednesday, transition to liquid should occur from south to north.
Temperatures will warm rapidly Tuesday and Wednesday, generally
around ten degrees per day, with increasing clouds as large-scale
lift increases. Precipitation should move out of the region
Wednesday night as the trough axis swings by and upstream descent
moves into the area. However, given that the origin of this system
is from the Pacific, little cooling is expected Thursday.
Thereafter, a clipper-type system looks to move into the Northeast,
which looks to be the next opportunity for colder air to invade the
area just beyond the forecast period.
&&
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.
Bands of snow will continue to overspread the terminals tonight
with IFR/LIFR conditions in the heavier and more persistent bands
of snow. Outside of those bands, generally VFR, although MVFR CIGs
possible. The heaviest bands of snow will develop after midnight
tonight.
Snow begins to taper off prior to daybreak, and conditions lift to
VFR through Friday morning.
LGT/VRB winds will become NW 5-10 KT towards daybreak Friday, and
then NW winds 5-10 KT remain in place through the TAF period.
OUTLOOK...
Friday night and Saturday: Northerly winds around 10 knots with
gusts as highs as 20 knots. VFR for KABE and KRDG. However, snow
will move northeastward for the other TAF sites from KPHL east. the
cutoff of snow or not seeing snow is still highly uncertain.
Saturday night through Sunday night: VFR. Northwest winds 10-20
knots with gusts 25-30 knots Sunday afternoon.
Monday and Monday night...VFR conditions, generally light winds, and
increasing mid and high clouds during the afternoon and evening
hours. High confidence.
Tuesday...Generally overcast conditions expected with increasing
chances of precipitation by late afternoon and evening, especially
in eastern Pennsylvania and northeast Maryland. Primarily VFR
expected, but conditions are expected to deteriorate Tuesday evening
as precipitation breaks out. Medium confidence.
&&
.MARINE...
W-SW winds 10-15 KT with gusts up to 20 KT. Winds should stay
below SCA criteria, but it will be close.
Winds turn out of the N as a coastal low tracks to our southeast
towards daybreak Friday, and then will become NW during the day
Friday. Winds will continue to range from 10-20 KT. A few gusts
could approach SCA criteria on Friday but held off on a headline
due to low confidence that we`ll reach criteria.
OUTLOOK...
Friday night and Saturday: Northerly winds around 10 knots with
gusts as highs as 20 knots. VFR for KABE and KRDG. However, snow
will move northeastward for the other TAF sites from KPHL east. the
cutoff of snow or not seeing snow is still highly uncertain.
Saturday night through Sunday night: VFR. Northwest winds 10-20
knots with gusts 25-30 knots Sunday afternoon. Gale gusts
possible.
Monday through Tuesday...Sub-advisory conditions expected, but seas
will gradually increase as a long-duration southerly fetch commences
early next week.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Winter Weather Advisory until 6 AM EST Friday for PAZ070-071-
101-102-104-106.
NJ...Winter Weather Advisory until 6 AM EST Friday for NJZ012>027.
Winter Storm Watch from late Friday night through Saturday
afternoon for NJZ022>025.
DE...Winter Weather Advisory until 6 AM EST Friday for DEZ001.
Winter Storm Watch from late Friday night through Saturday
afternoon for DEZ003-004.
MD...Winter Weather Advisory until 6 AM EST Friday for MDZ008-012.
MARINE...None.
&&
$$
Synopsis...Gaines
Near Term...Klein/MPS
Short Term...Klein
Long Term...Gaines
Aviation...Gaines/Klein/MPS
Marine...Gorse/Klein
Area Forecast Discussion
National Weather Service Charleston WV
948 PM EST Thu Jan 5 2017
.SYNOPSIS...
Snow producing system exits tonight. Even colder temps for this
weekend. Another cold front expected by mid next week.
&&
.NEAR TERM /THROUGH FRIDAY/...
As of 945 PM Thursday...
Reduced PoPs towards morning as HRRR has the system moving through
fairly quickly, but didn`t go as fast as the HRRR due to the
western edge of radar echos in a re-development cycle. Speaking of
that, a fairly heavy band of thick dendritic snowfall making its
way through the heart of our forecast area extending in a line from
Clarksburg to Logan, WV. Expect 1 inch/hour or more rates from
this band. It will move into the mountains over the next several
hours.
As of 645 PM Thursday...
No big changes, but have tried to highlight the threat of roads
freezing as the sun sets. Travel should be rather slick tonight.
As of 215 PM Thursday...
No major changes to the current system affecting the area with the
exception of lowering temperatures over the far southern zones.
Rounds of snow expected to continue through the late evening and
early overnight, before the snow exits northwest to southeast.
Hardest hit areas have been coal fields into the Tug Fork Valley
where the more persistent snow has fallen. Even the lighter
amounts thus far have caused all kinds of travel/road issues
across the CWA.
The next deformation zone will be quick to follow from the
southwest, grazing the southwest VA and far southern WV counties
heading into Friday evening. Models have become more aggressive
with the northward extent of this system, which has been much
further to our south in previous runs. Therefore, have introduced
POPs after 20Z Friday, which will increase going into the short
term/Friday night.
Temperatures will not come above freezing anywhere across the area
during the near term forecast.
&&
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
As of 245 PM Thursday...
Arctic air settles over the region on Friday, remaining through the
weekend. A southern storm may graze the eastern counties Friday
night into Saturday, but previous models have kept the storm to the
south and east, so confidence is low. With an upslope flow and
patches of low level moisture, some snow flurries are also possible
at times...mainly in the mountains.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
As of 245 PM Thursday...
A high pressure system will move over the area on Monday.
Another system will provide a warm front on Tuesday, followed by a
cold front on Wednesday. Depending on the timing of the warm front,
a wintry mix could occur with the initial precipitation.
&&
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
As of 945 PM Thursday...
IFR snow in the prevailing conditions will dominate the aviation
forecast through at least 05Z Friday. Long lasting improvements
are not likely until the snow exits tonight - likely in the 05-07z
timeframe. All locations improve to MVFR or VFR by the end of the
forecast period.
FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 00Z SATURDAY...
FORECAST CONFIDENCE: High for ifr in snow. Medium for snow timing.
ALTERNATE SCENARIOS: Timing of snow could still be quicker than
forecast. Conditions may drop to IFR faster than currently
forecast. Conditions may improve earlier tomorrow morning.
EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY
OF WFO FORECAST TO AVAILABLE MODEL INFORMATION:
H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS.
L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
DATE FRI 01/06/17
UTC 1HRLY 03 04 05 06 07 08 09 10 11 12 13 14
EST 1HRLY 22 23 00 01 02 03 04 05 06 07 08 09
CRW CONSISTENCY L L L L L M M M M M M L
HTS CONSISTENCY L L H M M M M M H H H L
BKW CONSISTENCY L L L L L L L L H M M M
EKN CONSISTENCY L L L L L L L L L L L L
PKB CONSISTENCY L L M L M M H H H H H L
CKB CONSISTENCY L L L L L L L M M M M L
AFTER 00Z SATURDAY...
IFR possible in snow Friday night into Saturday in the mountains.
&&
.RLX WATCHES/WARNINGS/ADVISORIES...
WV...Winter Weather Advisory until 6 AM EST Friday for WVZ005>008-
013>020-024>034-039-040-515>526.
Winter Weather Advisory until 3 AM EST Friday for WVZ009>011.
OH...Winter Weather Advisory until 6 AM EST Friday for OHZ083-
085>087.
Winter Weather Advisory until 3 AM EST Friday for OHZ066-067-
075-076-084.
KY...Winter Weather Advisory until 6 AM EST Friday for KYZ101>103-
105.
VA...Winter Weather Advisory until 6 AM EST Friday for VAZ003-004.
&&
$$
SYNOPSIS...RPY/JW/26
NEAR TERM...JW/26
SHORT TERM...RPY
LONG TERM...RPY
AVIATION...JW