Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/15/18
AREA FORECAST DISCUSSION
National Weather Service Eureka CA
332 PM PST Wed Nov 14 2018
.SYNOPSIS...The very dry late fall continues with mild afternoons
and chilly nights. Areas of smoke and haze will mix with a few
high clouds, dimming the otherwise sunny skies. Dry weather will
persist through the weekend while rain chances improve toward
.DISCUSSION...The RBG Cloud Phase Distinction product off of GOES
16 has been especially useful the past few days to display the
differences between the mix of high and mid-level clouds,
localized coastal stratus, and layers of smoke across northwest
California. The smoke aloft and high clouds have clearly thinned
or cleared out across much of northwest California, but smoke and
haze has settled in closer to the surface, with poorer air quality
along some of the valleys and especially the north coast compared
to yesterday. Unfortunately while a passing trough has helped
clear the layers of smoke aloft and allow for more daytime heating
across inland areas, boundary layer winds remain very light. HRRR
smoke modeling points toward some subtle improvement, so latest
thinking is that the air quality may improve slightly and should
not become any worse. However, surface winds still look very light
on Thursday, with the stronger northerly gradient staying
offshore, so expect some smoke and haze to continue to hang
around, especially the farther south one is from the Oregon
The other short-term questions will be stratus along the coast,
and any need for frost advisories tonight. With some warmer
temperatures and somewhat higher dewpoints along the coastal
plain,in areas that are still officially in the growing season,
slightly milder lows should be expected tonight, so have held off
on any frost advisories. Meanwhile stratus has shown up along
portions of the immediate Mendocino coast, while the north coast
is still `clear`. Some hi-res guidance points toward shallow fog
potential late tonight, particularly around Humboldt Bay, but
expect that it will be fairly localized and short-lived heading
into Thursday morning given the latest trends. Thursday night into
Friday morning may offer more of a potential for coastal
cloudiness from Cape Mendocino to Crescent City. Otherwise,
sunny albeit hazy skies should continue into the weekend across
our region. Temperatures will vary little through the weekend,
with highs continued in the mid 60s to low 70s inland, and upper
50s to low 60s at the coast. A wetter pattern may finally arrive
late next week, though some model guidance hints at enough of a
threat that we have a slight chance of rain in the forecast
starting on Tuesday. /AAD
.AVIATION...Lingering smoke from distant wildfires continues to
slightly obscure visibilities at most area terminals today, although
generally only to around 4 miles at worst. Gradual improvement in
that regard can be expected overnight tonight and Thursday as
northerly winds increase. Otherwise, low stratus has remained
offshore as of late afternoon and terminals are generally
Late tonight, there are indications that very shallow low stratus
and fog may develop along the immediate coast, potentially impacting
both ACV and CEC. Given the extremely shallow nature of the moist
marine layer, confidence is very low regarding this development.
Flight categories along the coast will likely be boom or bust
overnight and tomorrow morning, either remaining clear and VFR
(lingering smoke notwithstanding), or tanking to LIFR with
potentially 1/4 mile visibilities in the areas that fog develops.
Skies should clear tomorrow afternoon, but higher confidence
exists that more will develop tomorrow night. /BRC
.MARINE...While moderate northerly winds will develop across the
offshore waters overnight (with light southerlies along the
immediate coast due to a flow reversal), the more impactful
development will be the arrival of a building westerly swell
Thursday morning. While the aforementioned northerlies may push
wave heights to a steep 6 or 7 feet overnight, the building swell
tomorrow morning will cause seas to climb to around 11 or 12 feet.
These conditions will last Thursday morning through generally
Friday morning, and wave heights will gradually subside Friday.
For the remainder of the weekend and through mid week, generally
light and somewhat variable winds will prevail, and seas will remain
dominated by a modest northwest swell. There are some indications
that stronger southerlies and additional northwest swells may arrive
later in the week, but confidence is very low beyond mid-week. /BRC
NORTHWEST CALIFORNIA COASTAL WATERS...Small Craft Advisory from 4 AM
Thursday to 4 AM PST Friday for PZZ470-475.
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Area Forecast Discussion
National Weather Service Indianapolis IN
944 PM EST Wed Nov 14 2018
The NEAR TERM and AVIATION sections have been updated below.
Issued at 349 PM EST Wed Nov 14 2018
Dry weather will continue for a few more hours, but moisture is
quickly building into the southern portions of central Indiana as
a low pressure system moves closer to the Tennessee Valley. The
system will bring wintry precipitation to all of central Indiana
tonight into tomorrow. Snow and ice accumulations will make the
Thursday morning commute hazardous. The system will then exit
Thursday evening, and dry conditions will then prevail into the
weekend. At that point, a cold front will bring the next chance
for light snow and rain showers over the weekend.
.NEAR TERM /Rest of Tonight through Thursday Evening/...
Issued at 944 PM EST Wed Nov 14 2018
Added more sleet to the forecast this evening as reports come in of
predominantly sleet across the south. Some snow and light
rain/freezing rain is also falling. Tweaked PoPs but the overall
trend looks good, as the initial edge of radar echoes isn`t reaching
the ground due to the dry low levels.
Warm surge of air aloft still looks to impact the southeast forecast
area the most per the latest RUC analysis and forecast. Thus for now
have made no significant changes to ice/snow amounts. Will continue
to monitor closely.
Previous discussion follows...
Current water vapor satellite shows an area of low pressure
rotation over southern MO/northern AR, which will be the focus of
the near and short term periods. The imagery also shows an influx
of moisture into southern Indiana. So, the dry conditions will
only continue through the evening hours before the air column
becomes saturated and precipitation starts falling.
Depending on how quickly the lower levels saturate and the exact
start time of the precipitation will make a big difference in
precipitation type with this system. Initially, there could be
some light snow showers if the lower levels are able to saturate
before Thu 00Z. But, if precipitation starts any later than that,
precipitation could quickly change to a wintry mix of snow, sleet,
and freezing rain as forecast soundings trend toward a warm nose
in the mid levels. By midnight though, that wintry mix should be
the predominant precipitation type through Thursday morning. As
temperatures warm even further through the day on Thursday,
freezing rain and rain will become the prevailing precipitation
types through the remainder of the storm system.
Due to the increase in warmer air aloft, snowfall totals have been
reduced a bit and ice accumulations have been increased. So,
latest snow totals are now trending toward less than an inch
across the southeastern third of the forecast area to 1 to 1.5
inches over most of the area, and up to 3 inches across the far
western counties. Meanwhile, ice accumulations are now trending
closer to a tenth of an inch across the southeast quadrant, then
gradually decreasing northwestward.
As the system pushes east/northeastward on Thursday,
precipitation chances will diminish from west to east with the
western counties dry by Thu 23Z. Elsewhere, light rain and
freezing rain will linger across the eastern counties until Fri
06Z. After that, precipitation should be out of the entire
.SHORT TERM /Thursday Night through Saturday/...
Issued at 349 PM EST Wed Nov 14 2018
After Fri 06Z, the aforementioned system will quickly move off to
the northeast U.S. and dry conditions will return for most of the
short term period. In addition, weak warm advection will bump
daytime highs up a bit on Friday and Saturday into the upper 30s
(north)to low to mid 40s (central and south).
Saturday, precipitation chances will start increasing again from
the northwest as a cold front approaches central Indiana.
Precipitation will initially start as rain, then transition to
snow, but accumulations will be minimal.
.LONG TERM /Saturday night through Wednesday/...
Issued at 255 PM EST Wed Nov 14 2018
The extended timeframe begins with the forecast area under the
influence of a broad upper trough aloft and a frontal boundary at
850mb across the northern portion of central Indiana. The main
weather- maker during the extended portion of the timeframe rest
with the approach of an upper trough rotating through the broad
upper cyclonic flow. The GFS swings the effects of this system
through a bit faster than the ECMWF solution. Because of this
disagreement, decided to stick close to the regional
initialization blend which trended toward the slower ECMWF
solution. A slight chance for snow across the northern half of the
area is in place to start the timeframe. Then precipitation
chances increase and overspread the region during the day on
Sunday into Sunday evening...with precipitation coming to an end
from northwest to southeast Sunday night. Snow to start gives way
to rain over much of the area on Sunday as temperatures warm. The
northwest portion of central Indiana looks to see rain mix with
snow Sunday afternoon before much of the area returns to all snow
Sunday evening. If any accumulations were to occur...they look to
Monday looks to be the coolest day of the extended with highs from
the middle 30s to near 40 degrees. Then a gradual warming trend
takes root with highs on Wednesday from the lower 40s north to
near 50 degrees south.
.AVIATION (Discussion for the 150300Z TAF Update)...
Issued at 944 PM EST Wed Nov 14 2018
Lowered the ceiling (still VFR) to reflect current trends. Also
brought in some light sleet earlier based on latest observations and
Previous discussion follows...
Poor flying conditions are expected to develop by overnight and will
persist through Thursday. A wintry mix will fall overnight into
Precipitation should take a while to reach the ground at the TAF
sites this evening with a dry low level atmosphere. Precipitation
will fall overnight into the early daylight hours of Thursday, then
Looks like warm air aloft will create a mix of freezing rain and
sleet overnight at KIND/KBMG, with mainly snow/sleet at the other
sites. Confidence remains low at the moment on timing of when sleet
or freezing rain will be predominant, so put them both in all night
Colder air working in Thursday morning should allow precipitation to
change to all snow, then perhaps to rain as temperatures warm up
later in the morning.
Winter Weather Advisory through 7 PM EST Thursday for INZ021-028>031-
Area Forecast Discussion
National Weather Service Northern Indiana
608 PM EST Wed Nov 14 2018
Issued at 401 PM EST Wed Nov 14 2018
Clouds will continue to spread over the region ahead of an
incoming area of low pressure. Clouds will provide some insulation
overnight to promote lows in the upper 20s. Snow spreads in from
the south early Thursday morning, which can result in some
slippery travel conditions for the morning commute. Through
Thursday, freezing rain and sleet can mix in at times as
temperatures warm above freezing. Precipitation comes to an end
Thursday night. For the extended forecast, below normal
temperatures and couple of weak passing disturbances will be
.SHORT TERM...(This Evening through Thursday)
Issued at 318 PM EST Wed Nov 14 2018
Latest water vapor imagery and RUC analysis depicting deep closed
low over Arkansas this afternoon. Surface analysis showing
inverted trof associated with upper low extending from the eastern
gulf coast up into the Tennessee valley while high pressure was
still centered over the southern great lakes. Upper low expected
to lift northeast into southern Illinois tonight which will have
main surge of low level WAA displaced east of our area. Resulting
forecast soundings suggesting isothermal layer near 0C in the low
levels which will complicate precip type. Northern edge of precip
will reach the southern CWA after midnight tonight and begin as
primarily snow as good surface based cold layer initially should
have any partial melting changing back over to snow...with just a
possible mix with sleet. Surface temperatures expected to hover at
or slightly above freezing during the daytime hours and road
surface model indicating temperatures in mid-upper 30s and diurnal
timing would also trend surface temperatures more above freezing
as the event unfolds Thursday so plan for now is to hold off on
any headlines. Upper low slides east along the Ohio valley
Thursday afternoon leaving deformation axis moving across our area
and will have snow/rain chances continuing through the end of the
.LONG TERM...(Thursday Night through Wednesday)
Issued at 318 PM EST Wed Nov 14 2018
System quickly exits to the east Thursday night and despite
lingering cyclonic flow winds expected to maintain a southerly
component to the westerly flow and limit any lake effect potential
for our area. Surface ridge axis will extend from the gulf coast
up through the Ohio valley and provide quiet weather for Friday.
Pattern flattens somewhat and brings a couple of weak systems
through region over the weekend. Generally quiet weather pattern
beginning next week with temperatures continuing well below
.AVIATION...(For the 00Z TAFS through 00Z Thursday Evening)
Issued at 601 PM EST Wed Nov 14 2018
VFR conditions through 10Z - KFWA and 14Z - KSBN. Cigs lower
quickly after that time as the northern edge of the system
overspreads the region. As precipitation forms and increases in
coverage...visby will drop as well to between 1 and 3 miles.
The greatest challenge will be timing the transition from
snow/sleet/rain. With the warm layer overrunning the near to sub
freezing surface temperatures expect that there will be a period
of sleet and possibly freezing rain during the early morning
12-16Z...especially at KFWA. The warm air will surge north and
shift eastward throughout the day and this will favor a rain/snow
mix for KFWA. KSBN expected to remain cold enough to keep
precipitation all snow for most of the day.
Easterly winds will pick up during the day...especially KFWA and
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Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
906 PM CST Wed Nov 14 2018
906 PM CST
No big changes planned for the forecast this evening. Current
forecast has large deformation shield of snow spreading north into
our southern CWA late tonight then marching slowly north through
our CWA Thursday morning. Weakening forcing and the encountering
of dry air suggest that this precip should be on a weakening
trend as it lifts north of I-80. Secondarily, several models have
been keying in on a developing mid level f-gen band supporting a
developing band of precip (mostly snow) midday through late
afternoon Thursday over portions of northeast IL. Confidence in
this mesoscale feature developing isn`t terribly high as there is
a great deal of variability among the models. The 00z NAM is in
the camp with much weaker F-gen band and subsequently no
measurable precip in the afternoon and very little precip making
it north of I-80. There are still reliable models (the 00z GEM &
HiResARW) that still develop this f-gen driven band of precip,
though both of those models are a bit farther north than earlier
runs. Given the uncertainty, made no changes to tomorrow`s
pops/wx, though if the drier models like the NAM pan out then our
pops are significantly overdone tomorrow afternoon.
Only other change was to bump up sky cover a bit tonight near the
lake where some lake effect stratocumulus has developed and has
been spreading inland a bit. Shouldn`t be a big deal, but does
warrant a slight increase in sky cover.
121 PM CST
Short term forecast focus centers around a round of accumulating
snowfall late tonight into Thursday, with some uncertainty as to
how far the precip shield will get, where any potential snow bands
will set up in the afternoon, along with precipitation type/icing
concerns mainly late tonight into early Thursday.
High pressure is in place across the area this afternoon, making
for seasonally cold but dry conditions. There is some lake induced
stratocumulus cloud near lakefront areas, but low level flow will
turn around to the southeast/south which should limit the inland
extent of these clouds. Our next feature of interest is the
closed upper level low across the Arklatex region. With the cold
air in place, this low will bring significant accumulating
snowfall downstate. The upper low will spread to the mid
Mississippi Valley in downstate IL tonight, and then spread east
through the Ohio valley on Thursday. This track will favor areas
south for precipitation, but there is a nice trowal-like feature
that will setup out ahead of this system. There is a decent
precipitable water axis that will setup in the southeast lower
Guidance is still suggesting a surge of precipitation later
tonight into Thursday morning, though a weakening trend is noted
as the precip shield spreads farther north. Blended forecast
soundings suggest p-type should be mostly snow in our area, but
there is a a narrow corridor across Benton/Newton/Jasper, possibly
into Ford/Iroquois that could have some mixed precip per the RAP
The NAM/GFS/EC are all less aggressive with this warm nose, thus
will hold off on any advisory for light icing given confidence
issues, but something for the evening shift to monitor.
There are then hints that some additional snow bands will form in
the later morning/early afternoon, possibly over portions of the
Chicago area. This timing is not favorable for pavement
accumulation, as surface temperatures should be above freezing,
and outside the main band rain could mix in. But under the main
band column cooling would support all snow should a single band
set up, and some grassy accums would be possible. Low confidence
on the exact placement of this.
For our southern areas, Forecast amounts have not changed a whole
lot from previous ones, but the daytime precipitation does
appear to be more localized and tied to the deformation zone.
Still advertising a 1-3" type wet snow for some areas.
121 PM CST
Thursday night through Wednesday...
Following Thursdsay`s system, the upper level flow will shift back
to northwesterly. The current system across the Pacific Northwest
will follow an active upper jet and quickly cruise into the area
Thursday night. The main moisture axis/surface feature will pass
across northern and central Lake Michigan. There is a sharp upper
trough, and along the nose of the jet we could see some very
light precip during this time frame, but feel like most areas will
remain dry. If there is some precip, it could actually be freezing
drizzle given a nice wave and a deepening low level moisture field,
but limited deeper moisture. This does appear more likely north
of our area, but something to watch. There will also be some
breezy southwest to west winds out ahead of the low.
The more active wave will follow on the heels of this one as the
northwest flow strengthens, and a stronger upper trough gets
carved out across Hudson Bay. This feature will bring cold/arctic
frontal boundary back southward, bringing a reinforcing shot of
cold air, along with the chance for snow Saturday morning. There
are several factors going for quick hitting snow chances in the
region during this time. The first being a strengthening upper jet
just north of the area, a tightening frontal boundary, and a low
amplitude shortwave. The frontal signal is strongest while the
upper forcing is still modest, but the frontogenetic signal is
strong enough to suggest a round of light snow can be expected.
Models are still mixed as to how far south the frontal zone will
be, but the most likely time period would be Saturday morning.
Snow amounts would not be high given the fast moving nature of the
upper wave, but brief moderate rates would be possible where the
frontal zone is strongest. There is a chance for some lake effect
snow in the afternoon/early evening, but confidence is still low
Cold and dry conditions follow, but there are hints of a small
warmup at some point next week.
For the 00Z TAFs...
VFR conditions through early Thursday morning with light, mainly
easterly, winds. During the morning Thursday, some snow, possibly
mixed with rain, is expected attempt to move north into the
Chicago metro area terminals. However, low level dry air, could
impede the northward progress some. There are a handful of high
resolution forecast models that suggest a narrow, but more intense
band of snow could develop right over the Chicago area late
Thursday morning into Thursday afternoon. Confidence in whether
the band materializes is not terribly high, and subsequently if it
does, where it will impact becomes a question. Given the
uncertainties, felt the previous TAF nicely conveyed the forecast
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Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
924 PM EST Wed Nov 14 2018
High pressure will build over New England overnight as an area
of low pressure develops over the Tennessee Valley. Another
area of low pressure will develop along the Carolina coast early
Thursday and move north towards Long Island Thursday night,
while the high pressure center moves offshore. Another area of
high pressure will build in from the Ohio Valley over the
weekend. A cold front will likely approach from the Great Lakes
early next week.
.NEAR TERM /THROUGH THURSDAY/...
At 02Z, regional radar mosaic shows reflectivity returns in
southern and southwest VA, with 02Z surface obs shows unknown
precip (aka likley IP) in southwest VA at Hillsville KHLX.
Across our CWA, surface winds have begun to veer, showing cold
air damming beginning to setup. This will initiate, and then
reinforce, cold air below the inversion which is evident at
around H85 on this evening`s 00Z KIAD sounding. Very cold air
associated with the surface high (-10C 925mb at KALY) which attm
is building into New England, will continue to drain down the
northeast corridor and then get locked in place east of the
eastern continental divide.
This sets up a solid mixed winter p-type event along and west
of the Blue Ridge, where Winter Storm Warnings are already in
place, denoting much higher confidence of at least a moderate,
potentially high impact event in these warned locations.
However, east of the Blue Ridge, there is less confidence of
winter p-type, with the influences of the Chesapeake Bay and
Atlantic, particularly east of Intestate 95. The NWP-progged
upward motion and cold air aloft tomorrow morning is an area of
concern, as vertical displacement of this colder air aloft with
large UVV as evidenced by every NWP model tomorrow morning could
promote a longer period of frozen precipitation tomorrow
morning in the I-95 corridor, including Baltimore and Washington
DC Metro Areas. Fortunately, Winter Weather Advisories are
posted in these areas as well, and the only updates I have made
to the forecast is bring the snow/sleet accumulations further
east with around 0.5" accumulations early tomorrow morning in
the metro areas, and up to 1-2 inches in the northwest suburbs
Loudoun/West Montgomery/Howard/N Balt.
The reasonable, 23Z HRRR p-type diagnostic has precip moving in
around daybreak in DC Metro, starting off as sleet and rain,
then changing over to snow/sleet for several hours tomorrow
morning. The same scenario exists for the Baltimore Metro, but
holding off until 7-9 am start time. The model then shifts
everything to rain early in the afternoon in this region. With
the road temps forecasts aoa freezing, this should inhibit
accumulations on road surfaces, unless the magnitude of the
precipitation can overcome the above freezing road temps. This
would be the reasonable worse case scenario, and even with this
scenario, modeled road temps rise aoa 40F early afternoon in the
Balt/Wash corridor. Bottom line attm is that it is likely that
freezing and frozen will impact the Thursday morning rush hour,
and while it likely won`t cause accumulation on road surfaces,
it will be the first winter precip of the season and contribute
to some shock and awe.
West of the Blue Ridge, confidence is much higher for an
extended 24-hour freezing/frozen p-type event lasting through
Thursday night. Difficult to come up with high confidence
specifics as to the mix/magnitude of p-type west of Blue Ridge,
but the 90 percentile for freezing rain has well over 0.5
inches there, approaching 1.0 inch glaze accumulation in the
central Shenandoah Valley and surrounding terrain. I have higher
confidence with higher elevations aoa 2kft, as a major freezing
rain event could be unfolding tomorrow along Skyline Drive and
the eastern Continental Divide, including the Spruce Knob
I also have concerns about moderate-to-heavy rainfall on
Tuesday leading to isolated flooding due to rapid runoff, as
vegetation has been killed off by freeze over the past couple of
weeks. Areas most prone for runoff flooding will be southern
MD, Prince Georges County/Upper Marlboro, and Anne Arundel.
.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
A second low will develop over North Carolina on Thursday and
strengthen through the day as it moves northeast under a coupled
upper level jet. Meanwhile, an upper low will push northeast
toward us from the south-central US. High pressure over New
England will keep damming of cold air going over the western
portions of the forecast area, while some cold air erosion looks
likely east of the Blue Ridge by afternoon. Thus, have
sleet/rain along and east of I-95 transitioning to plain rain
through the day, with snow/sleet/freezing rain between the Blue
Ridge and I-95 changing to sleet/freezing rain and then rain
very late. From the Blue Ridge west, cold air likely gets stuck,
so am keeping temps at or below freezing all day with
snow/sleet/freezing rain transitioning mainly to sleet/freezing
rain. Potential for significant snow and ice exists given the
favorable synoptic set-up for cold air and heavy precipitation.
Caveats to this solution include prolonged periods of sleet, the
fact that heavy freezing rain is less efficient at accreting,
and that much of the precipitation will fall while there is
solar insolation. However, within the warned area, it is
important to note that hazardous/wintry precipitation will be
falling most of the day and into the evening with temperatures
near or below freezing. Given the antecedent warm conditions,
accumulations will likely be greater on grassy and elevated
surfaces, as well as any areas which are typically shaded.
Even where precip is mainly rain, the hazard of heavy rain and
potential flooding will exist. See the hydro section below for
The surface low quickly lifts northeast Thursday evening, with a
mid-level dry slot working in around the low to our west.
Therefore precipitation will likely turn to light rain/drizzle,
(freezing drizzle where surface temperatures remain AOB 32).
Later in the evening and overnight, wraparound moisture
associated with the passing upper low will bring a final shot of
precipitation, which would initially be rain/freezing rain, but
could end as a period of snow. Any accumulating snow is most
likely over the mountains. Temps will likely be fairly steady
Friday into Friday night, the system heads further away and we
have a comparatively mild westerly flow settling across the
region. Temps will actually be noticeably milder on Friday after
the clouds break, with highs in the mid 40s to lower 50s. Lows
return near or below freezing Friday night with high pressure in
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
The long term period will start out with a weak ridge of high
pressure at the surface and zonal flow aloft. This will lead to
mostly sunny skies on Saturday, with temperatures maxing out in the
upper 40s to near 50. Cloudier, but still dry conditions are
forecast for Sunday, with temperatures once again reaching into the
upper 40s to around 50.
A cold front will progress through the area on Monday as a
vigorous shortwave trough traverses the Great Lakes Region.
With the main forcing for ascent associated with the trough
displaced well to our north and limited moisture ahead of the
cold front, any precipitation is expected to be light and mainly
confined to upslope favored areas to the west of the Blue
Ridge. High pressure will move back in for Tuesday, resulting in
quiet weather conditions and below normal temperatures with
highs in the 40s.
.AVIATION /02Z THURSDAY THROUGH MONDAY/...
Clouds will lower as precipitation arrives late tonight towards
dawn for the major terminals. Mainly rain expected at DCA
(though there could be a period of sleet and snow), with more
of a mix of rain/ice/snow at the other terminals. MRB is likely
to be the snowiest and iciest, though temperatures could persist
very close to freezing at CHO, BWI, and IAD into the midday to
afternoon hours. Cigs and vis also likely to be significantly
restricted on Thursday (IFR to LIFR), even where it is just
plain rain. Low level wind is possible, although the surface
gradient may preclude it from reaching criteria.
Conditions improve later Friday night with VFR returning Friday
as the system pulls away. Conditions continue VFR Friday night.
VFR conditions are expected through the weekend into early next
An increase in winds overnight as low pressure develops and approaches
from the southwest. Therefore, a Small Craft Advisory remains
in effect for the middle Bay and lower Potomac. Winds shift more
northeasterly Thursday and increase potentially to 35 knots,
with gales now up for the central Bay. As the low passes
overhead Thursday evening, there will likely be a lull in the
winds, but they will increase again as the low pulls away, so
have left the headlines in effect. A Gale Warning could
potentially be needed for all waters by Friday morning. Rain and
fog, perhaps also some sleet, are hazards Thursday as well,
though the weather will clear on Friday. Winds will gradually
subside by Friday night as high pressure moves in.
SCA level winds may be possible very early Saturday morning before
winds relax as high pressure moves overhead.
A plume of 1.5+ inch PWs will be advecting toward the Mid-
Atlantic Thursday on an anomalously strong 850 hPa easterly jet.
Though PWs likely stay around 1-1.25 directly overhead, the
very strong low-level moisture advection coupled with strong
mid and upper jet dynamics will result in widespread moderate to
heavy precipitation. In the I-95 corridor where precipitation
is expected to fall as mainly liquid (and where 6-hr FFG is less
than 1.5 inches), some isolated minor areal flooding instances
could arise. Generally 1-2" QPF seems likely, but will be spread
out over a long duration. Latest MMEFS/NWM forecasts have
trended downward for streams and rivers, but some poor drainage
flooding is certainly possible, especially where leaves are
blocking storm drains.
Increasing onshore flow overnight into Thursday ahead of an
approaching coastal low will cause tidal anomalies to increase.
Although tides will be near astronomical minimums, minor
flooding is still possible for at least some areas along the
tidal Potomac River and western shore of the Chesapeake Bay.
Here are the current rankings for wettest year on record
(through November 13th):
Washington DC area (DCA)
1. 61.33 inches (1889)
2. 60.83 inches (2003)
3. 60.09 inches (1878)
4. 58.17 inches (1886)
5. 57.54 inches (1948)
6. 57.38 inches (2018)
7. 54.29 inches (1937)
Weather records for the Washington DC area have been kept at
what is now Ronald Reagan Washington National Airport (DCA)
since 1945. Precipitation records observed downtown extend the
period of record back to 1871.
Baltimore MD area (BWI)
1. 62.66 inches (2003)
2. 62.35 inches (1889)
3. 61.68 inches (2018)
4. 58.98 inches (1979)
Weather records for the Baltimore MD area have been kept at
what is now Baltimore-Washington International Thurgood Marshall
Airport (BWI) since 1950. Precipitation records observed
downtown extend the period of record back to 1871.
Dulles VA area (IAD)
1. 65.67 inches (2003)
2. 59.05 inches (1972)
3. 58.09 inches (1996)
4. 57.65 inches (2018)
5. 55.43 inches (1979)
Weather records have been kept at what is now Washington Dulles
International Airport (IAD) since 1960.
NOTE: All climate data are considered preliminary until
reviewed by the National Centers for Environmental Information
DC...Winter Weather Advisory from 4 AM to 1 PM EST Thursday for
MD...Winter Storm Warning from 4 AM Thursday to 4 AM EST Friday for
Winter Weather Advisory from 4 AM to 1 PM EST Thursday for
Winter Weather Advisory from 4 AM to 4 PM EST Thursday for
Winter Weather Advisory from 7 AM to 4 PM EST Thursday for
VA...Winter Storm Warning from 1 AM Thursday to 1 AM EST Friday for
Winter Storm Warning from 4 AM Thursday to 4 AM EST Friday for
Winter Weather Advisory from 1 AM to noon EST Thursday for
Winter Weather Advisory from 4 AM to 1 PM EST Thursday for
Winter Weather Advisory from 4 AM to 4 PM EST Thursday for
WV...Winter Storm Warning from 4 AM Thursday to 4 AM EST Friday for
MARINE...Small Craft Advisory from midnight tonight to noon EST
Thursday for ANZ532-540-542.
Gale Warning from noon Thursday to 6 AM EST Friday for
Small Craft Advisory from noon Thursday to 6 AM EST Friday for
Small Craft Advisory until noon EST Thursday for ANZ533-534-
Small Craft Advisory from midnight tonight to 6 AM EST Friday
Small Craft Advisory from 6 AM Thursday to 6 AM EST Friday for
Area Forecast Discussion
National Weather Service San Francisco Bay Area
329 PM PST Wed Nov 14 2018
.SYNOPSIS...Smoke and haze continue to impact much of the Bay Area
while dry and seasonable weather persists elsewhere. No big
changes in the weather through the end of the work week with some
signs of less smoke and slightly cooler temperatures over the
weekend. Dry conditions persist at least through Tuesday with
possible pattern change by the middle of next week.
.DISCUSSION...as of 2:56 PM PST Wednesday...Smoke from the Camp
Fire continues to be one of the main impacts on Bay Area weather.
Satellite showed another belch of smoke this morning that has
worked its way down the Sac Valley and into the Bay Area.
Gradients show a half millibar offshore from Sac to SFO with east
winds blowing in the Delta and bringing the smoke westward into
the Bay Area. Visibility is now less than a mile in Livermore with
the East Bay indicating some of the poorest visibility. Hazy
skies continue elsewhere with afternoon highs generally in the 60s
with 70s for the Central Coast. Very dry conditions continue this
afternoon with many sites reporting humidity values in the single
digits including usually wet spots such as Big Sur coming in at
Day over day changes in the large scale weather remain minor with
daytime highs in the 60s and 70s with fairly cool overnight lows
from the mid 30s to mid 40s through the end of the work week.
Million dollar question is how active the Camp Fire will burn the
next few days. As was shown today with lighter winds and even
light offshore flow the smoke will tend to drift towards the Bay
Area until we get a shift in the large scale weather patterns.
That may occur by this weekend as an upper low approaches the
Southern California coast and some type of southerly flow may help
to keep any smoke to our east. It should be noted that latest
trends build a ridge over northeast California over the weekend
that will keep warm and dry weather up there with a fairly strong
low level inversion likely in place, not ideal for smoke
Long range forecast details regarding any rainfall next week
continues to be watched. The 12 and 18z gfs deterministic runs
have been discouraging and gone completely dry. Need to note that
the ensembles still show a trough along the west coast Weds
through Friday of next week. The ecmwf has a weak front on Weds
and a second stronger storm by about next Friday. This is all
still 7-10 days out so confidence remains low on details as we
anxiously await a pattern shift. Until then mild and dry weather
for at least another 6 days.
.AVIATION...As of 03:29 PM PST Wednesday...For 00Z TAFs. Much of
the area continues to see reduced visibilities to MVFR, with
isolated instances of IFR, due to smoke. Generally poor vis is
expected to continue with slant range visibility issues persisting
through the period. Light winds will continue through the period
Vicinity of KSFO...MVFR vis due to smoke with generally light
winds. Slant range vis issues expected to persist. Latest HRRR
smoke forecast does not suggest much change in smoke conditions
through at least tonight.
SFO Bridge Approach...Similar to terminal.
Monterey Bay Terminals...VFR prevailing with periods of reduced
vis to MVFR due to smoke.
.MARINE...as of 02:26 PM PST Wednesday...Predominately light north
to northwest winds across the waters through the end of the work
week. Locally breezy winds will exist near coastal gaps and
favored coastal jet areas. Light mixed swell today with a new
northwest swell arriving tomorrow.
PUBLIC FORECAST: RWW
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Area Forecast Discussion
National Weather Service Paducah KY
611 PM CST Wed Nov 14 2018
Issued at 611 PM CST Wed Nov 14 2018
Updated aviation discussion for 00Z TAFs.
.SHORT TERM...(Tonight through Friday night)
Issued at 302 PM CST Wed Nov 14 2018
Current Winter Storm Warning and Advisories remain in effect "as
is" at this time.
Current GOES-E Satellite Imagery showing a well developed closed
upper low near El Dorado Arkansas, with significant deformation
aloft to the north and east. Even though temperatures over
Arkansas range from upper 20s to lower 30s from north to south
across the state, widespread observations of snow is being
reported at this time, suggesting most of the layer aloft is at or
below freezing at this time.
Deeper layer moisture and lift advecting northward from northern
Mississippi into West Tennessee are within a zone of enhanced
lift, as depicted by the latest preferred RAP numerical model
guidance. This zone is in a decent area for seeder-feeder ice
nucleation and will continue to work into the Purchase/Pennyrile
region of west Kentucky through Sunset. As the mid-upper level low
continues to work along eastern Arkansas between 6 pm to 8 pm, we
could see an increase in snowfall intensity and lowered
visibilities (1-2 statute miles) over southeast Missouri/Purchase
area of west Kentucky, into extreme southern Illinois. Do not
expect much recovery in temperatures the rest of the afternoon
and actually a drop to 1-2 degrees overnight into the upper 20s
over southern Illinois and southeast Missouri. Expect to see these
areas remain in snow most of the night.
For southwest Indiana and the Pennyrile region of West Kentucky,
a drop in moisture in the ice nucleation layer, along with warm
advection ahead of the low will make for a sharp west to east
gradient for snow versus wintry mix then to rain. At this point in
time, the zone of wintry mix (sleet/freezing rain/snow) will be
along a Cadiz to Henderson Kentucky line, with a transition to
rain near an Owensboro to Elkton Kentucky line.
The best forcing overnight will shift toward northern section of
southern Illinois, with higher precipitation amounts expected
there through at least 5 am CST. Anticipate the best snow
accumulations between 10 pm and 4 am tonight further north into
Could see a significant loss of moisture for any further snow and
sleet production through the mid-morning hours on Thursday as the
upper low moves close to Mount Vernon, IL by 6 am. May still see
some deformation snow over northwest sections of southwest
Illinois and southeast Missouri through at least 8 am. This should
reduce the overall precipitation over the WFO PAH forecast area,
with some mix possible.
Needless to say, it will be a little tricky overnight, as any
mesoscale banding in the vicinity of upper low may enhance wintry
precipitation amounts. Evening and overnight crews will monitor
for any adjustments in amounts and locations.
Should see some recovery on temperatures into the 40s on Friday,
with some slight reduction over areas with deeper snow cover still
on the ground.
.LONG TERM...(Saturday through Wednesday)
Issued at 302 pm CST Wed Nov 14 2018
Currently the only pcpn forecast in the extended forecast period was
a post-cold-frontal event mainly Sun afternoon through Sun night,
driven by mid level shortwave energy moving out of the northern
Rockies. The medium range models were in reasonable agreement with
the timing of the event, though the 12Z GFS seemed at least 12 hours
ahead of the 00Z ECMWF/12Z CMC with the passage of the surface wedge
of cold air, thus making it a colder solution overall. The
initialization blend ended up with a fairly early cold fropa on Sat,
so it fits for now.
This light pcpn event may start out as a brief wintry mix Sun
morning in the far northwestern edge of the PAH forecast area.
Otherwise, rain can be expected during the day, moving in from
northwest to southeast. However, much of western KY may remain dry
during the daylight hours. By nightfall, as thicknesses continue to
drop behind a cold front, a transition from rain to snow is
expected, with a possible brief wintry mix in between. Snow amounts
of up to a couple of tenths are expected at this time.
In the wake of the aforementioned system, high surface pressure will
prevail under general northwesterly flow aloft. Unseasonably cool
temps are expected to continue with the coolest temps occurring on
Issued at 611 PM CST Wed Nov 14 2018
A very dynamic situation will keep conditions in flux over the
next 12 hours or so as an unseasonably strong early season low
moves across the region. Conditions will deteriorate quickly this
evening where they haven`t already, with MVFR/IFR conditions
persisting through the night. Mainly snow is expected across
western portions of the region (KCGI/KPAH). This may be mixed at
times with freezing rain or drizzle due to the loss of ice
nucleation. Further east (KEVV/KOWB), a mix of snow, sleet, and
freezing rain is expected. Precipitation should trend towards very
light snow on Thursday in the wrap-around on the back side of the
low. Winds will back from north/east tonight to west/southwest on
Thursday with the passage of the surface low.
IL...Winter Weather Advisory until 6 PM CST Thursday for ILZ076>078-
Winter Storm Warning until 6 PM CST Thursday for ILZ075-080-081-
MO...Winter Weather Advisory until 6 PM CST Thursday for MOZ100-
Winter Storm Warning until 6 PM CST Thursday for MOZ076-086-087.
IN...Winter Weather Advisory until 6 PM CST Thursday for INZ081-082-
KY...Winter Weather Advisory until 6 PM CST Thursday for KYZ001>022.
Area Forecast Discussion
National Weather Service Raleigh NC
1020 PM EST Wed Nov 14 2018
Cold high pressure will build across the Northeast tonight, while
ridging southward in the lee of the Appalachians. Meanwhile, a pair
of low pressure systems from the TN Valley to the northeastern Gulf
of Mexico will consolidate while tracking northeastward across the
Carolinas tonight, then rapidly deepen while tracking up the middle
Atlantic and New England coasts Thursday night and Friday.
.NEAR TERM /THROUGH EARLY THURSDAY/...
As of 1015 PM Wednesday...
...Flood Watch remains in effect through 700 PM Thursday...
There are three principle forecast concerns tonight and early Thu,
including 1) the already-headlined expectation of widespread,
soaking rain - and flooding, 2) the possibility of very light
freezing rain over the nw Piedmont, and 3) the probability of 35-45
kt wind gusts that may down trees in saturated soil early Thu.
Mid-upr low centered near the MO bootheel this evening will deepen
while tracking newd into srn IL by 12Z Thu, with strong and
perturbed mid-upr flow over the Southeast and middle Atlantic,
between the deepening low and a strong sub-tropical ridge over the w-
cntl N. Atlantic. In response, significant acceleration of low-mid
level flow, and associated strong 925-700 mb WAA and moisture
transport, will promote the development and nwd expansion of
widespread rain from both the current precipitation shield over the
Southeast, and another that will blossom nwd from off the Southeast
coast late tonight.
At the surface, 1036 mb high pressure centered over the lwr Great
Lakes and far sern Ontario will build across the Northeast, while
ridging swd through the middle Atlantic, Carolinas, and GA. The (dry
air) ridge axis --and minimum in surface dewpoints-- was analyzed at
02Z from ern PA sswwd across ern VA and nrn NC; and the models
indicate this feature will continue to migrate wwd across cntl NC
with an associated minimum in surface dewpoints in the upr 20s to
around freezing pivoting into the favored CAD region/over the nw
Piedmont, by 09Z. Observational trends support that data, as the
surface dewpoint at RWI and RDU has fallen five degrees in the past
five hours to 32 and 34 degrees, respectively, for example. This
cold, dry air advection, is being masked by the widespread light
rain/sprinkles that have been falling into it over the Carolinas and
VA during to the past 24 hours. This ridge will get squeezed over
wrn NC, as one cyclone analyzed at 02Z near CSV deepens while
tracking into the lwr OH Valley, and a pair of other lows on the
primary surface baroclinic zone from the nern GOM to just offshore
JAX, consolidate while tracking to near CHS by 12Z Thu.
Between the primary lows, there has been a gravity wave-like signal
across the Carolinas in model guidance for a couple of days now,
including most notably the NAM and HRRR today. Both show sharp
pressure perturbations migrating through the simulated MSLP field to
the nw of the consolidating coastal low, with associated max wind
gusts around 40 or so kts spreading across cntl NC between 10-18Z.
This surface trough and ongoing narrow precipitation band and sharp
convergence axis, evident for several hours in FFC data over wrn GA,
will be the one and area to watch for wave amplification and
manifestation of a strong pressure fall/rise couplet and
(isallobaric) surface wind response. In other words, if spurious
winds/gusts become evident over n-cntl GA and wrn SC become evident
by 06-09Z, then the likelihood of those traveling downstream in the
subsequent 6-9 hours would increase confidence in such an occurrence
of strong surface winds in cntl NC.
Regarding the freezing rain threat, guidance, including the 00Z NAM,
suggests the wet bulb freezing line will be draped from near HKY to
MTV, near and just nw of Forsyth Co. between 08-13Z, with resultant
surface temperatures hovering just above freezing over the nw
Piedmont. As previous shifts have astutely noted, the magnitude of
mid level warming characterized by 700-850 mb partial thickness
nearing 1590 or so meters, combined with a wet and relatively mild
mid-Nov ground, suggests very little freezing rain accrual
potential; and any that does occur, would be most likely to occur
(very lightly) in trees/power lines, with elevation away from the
surface and into the cold nose.
Lastly, a few elevated rumbles of thunder may occur between 12-15Z
Thu, for weakly unstable parcels rooted above the very stable
.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
As of 320 PM Wednesday...
Thursday and Thursday night: The widespread rain will continue
through midday/early afternoon, becoming moderate to heavy at times
as the coastal low tracks inland, up coastal NC. Some elevated
thunder across the far eastern zones is also possible, as the NAM
hints at 500 J/KG of MUCAPE east of I-95. Otherwise, any surface
base convection should remain east of the surface low, along the
immediate coast. Precipitation will then begin to taper off to
drizzle Thursday afternoon and evening as drying aloft overtakes the
area from the SW.
Expect a very sharp NW-SE temp gradient with the cold air damming
entrenched across the NW Piedmont, resulting in very little rise in
temps on Thursday, while eastern areas will experience modest
warming in proximity to the coastal low. Highs ranging from
mid/upper 30s NW to upper 50s/lower 60s SE. Cold dry air advection
in the wake of the low lifting up the Mid-Atlantic coast will lead
to clearing overnight. Lows in the upper 20s/near 30 NW to mid/upper
Hydro/: With soils already saturated, along with area river and and
streams already in flood, another round of widespread heavy rainfall
of 1 to 2 inches will result in a heightened risk for additional
flooding across central NC tonight through Thursday.
By Friday morning, the upper-level low will continues to shift
northeastward along the Atlantic Coast, with a period of more zonal
flow aloft taking over. This will allow cooler air to advect into
the area in the low`s wake, with a downsloping
westerly/northwesterly wind helping to dry out the area. This will
allow for gradually clearing skies and afternoon temperatures
warming slowly into low to mid 50s. Overnight lows will settle again
to near freezing across the north, with mid 30s prevailing across
the coastal plain and sandhills.
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
As of 320 PM Wednesday...
SFC high pressure will build into the Mid Atlantic over the weekend
as a slightly more progressive troughing regime begins to take shape
late in the weekend. This will allow for a mostly dry sfc FROPA on
Monday. With the area of subsidence in place, overnight lows will
remain well below normal, while high temperatures will actually
moderate slightly in the wake of the system. Expect highs generally
in the 50s each afternoon with overnight temperatures dipping into
the mid 30s across central NC through early next week. A reinforcing
cold front may bring a better push of cold air and perhaps a few
clouds into the region early on Monday, however, uncertainty remains
in place in reference to overall timing and strength of this system.
.AVIATION /00Z THURSDAY THROUGH MONDAY/...
As of 730 PM Wednesday...
Dry air around 900 MB continues this evening with weak returns
mainly across the western half of the CWA (towards KINT and
KGSO). Rain will continue to spread into the region from the
southwest this evening with widespread rain moving in after
midnight. Ceilings will also fall below VFR around 8z if not
earlier. Forecast soundings on the GFS and NAM show a time frame
of more around 6z. Ceilings will then continue to further
collapse to LIFR. Visibilities will also quickly fall down into
IFR and potentially LIFR as heavier pockets of rain move
overhead. Also in the morning hours, some freezing rain will be
possible as forecast soundings show thermodynamic cooling
occurring (mainly between 5 and 7 AM).
Temperatures will rise above freezing everywhere (if any sub
32 degrees ends up occurring). Ceilings and visibilities will
remain down through the TAF issuance though. During the day,
widespread precipitation will continue and not come to an end
until the afternoon hours. Winds will also be gusty with gusts
up to 30 kts possible.
Outlook: Gusty NW winds can be expected Friday, with VFR
Flood Watch through Thursday evening for NCZ007>011-021>028-
Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
800 PM EST Wed Nov 14 2018
A cold front moving southeast through the Florida Panhandle
and eastern Gulf of Mexico is on track to push south into
the Florida Peninsula overnight, with a robust squall line
positioned ahead of the front, just now entering the
coastal waters early this evening. Scattered to numerous
thunderstorms are developing over the Florida Peninsula
ahead of this storm, and are continuing to lift north
through the forecast area this evening. Storms were a bit
slower in developing this afternoon than were previously
forecast, and HRRR and other short range models are showing
a the squall line breaking apart as it approaches the coast
overnight. As a result, the rain forecast for the overnight
hours was dialed back slightly from what was previously
Otherwise, the forecast looks on track, and no significant
changes were needed for the evening update.
Scattered showers and thunderstorms will continue to move
north through the area overnight, causing periods of
MVFR-IFR conditions. Widespread MVFR ceilings will spread
across the area overnight as a cold front passes south into
the area. On Thursday, periods of MVFR ceilings will
continue throughout much of the day under breezy northwest
Showers and thunderstorms will continue and winds will
increase overnight as a strong cold front pushes southeast
into the coastal waters. Winds are expected to reach
advisory levels offshore overnight, and cautionary levels
nearshore. Winds will turn to the northwest and then north
behind the front tonight and Thursday, and will hold around
cautionary levels. Winds will gradually subside Friday
through the upcoming weekend as high pressure builds in from
.Preliminary Point Temps/PoPs...
TPA 68 70 50 67 / 50 20 0 0
FMY 71 77 55 72 / 40 20 0 0
GIF 68 73 46 68 / 40 20 0 0
SRQ 69 72 54 69 / 40 20 0 0
BKV 66 67 42 66 / 60 20 0 0
SPG 69 70 54 67 / 50 20 0 0
FL...High Rip Current Risk from 5 AM EST Thursday through
Thursday evening for Coastal Charlotte-Coastal
Hillsborough-Coastal Lee-Coastal Manatee-Coastal
Gulf waters...Small Craft Advisory from 11 PM this evening to 5 PM EST
Thursday for Waters from Bonita Beach to Englewood FL
out 20 to 60 NM-Waters from Englewood to Tarpon
Springs FL out 20 to 60 NM-Waters from Tarpon Springs
to Suwannee River FL out 20 to 60 NM.