Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/01/17
Area Forecast Discussion
National Weather Service Duluth MN
544 PM CST Tue Jan 31 2017
Issued at 543 PM CST Tue Jan 31 2017
Moderate to heavy snow showers were moving through portions of the
Northland. The latest radar showed the snow showers from near
Floodwood south through Hinckley to near Pine City. They were
moving quickly southeast and will be capable of producing a quick
half to inch of snow in a 15 to 30 minute period. These snow
showers should diminish by late evening as they progress through
.SHORT TERM...(This evening through Wednesday)
Issued at 328 PM CST Tue Jan 31 2017
Scattered snow showers across the Northland today but while the
flakes are big, accumulation has been fairly light per spotter
reports and webcams. Arctic air is on our doorstep up north, with a
line of clearing to spread from north so south overnight tonight
leading to falling temperatures. Mostly sunny with the first below-
normal day in more than two weeks on Wednesday.
On the synoptic scale an arctic front sits across southern Canada
with a weak low over Ontario north of Lake Superior. High pressure
to the west will build in as the arctic front dives south across the
upper Midwest tonight into Wednesday resulting in falling
temperatures. Winds are expected to remain steady at 5-10mph with
some gusts to 20mph possible early in the evening. Late tonight
winds are the big forecast challenge today: if we remain mixed
temperatures will fall, but only to a few degrees below zero across
north-central Minnesota. However, if winds go calm late tonight,
even if just for a few hours, with clear skies and high pressure
building in temperatures could plummet to -15 in some areas. Kept
with the previous forecast trend of going colder than most guidance
to account for this possibility. The line of clearing is already
running a bit faster than modeled per visible satellite, and the
RAP/HRRR have picked up on this well with RAP depicting lows -15 to
zero in northern MN tonight. So, forecast should be considered a
middle-ground with the possibility for slightly warmer or much
colder temperatures overnight tonight. Since temperatures will only
plummet if winds go calm, wind chills are not a concern tonight.
There may be a period of lake effect snow showers along the south
shore overnight, but as the drier air moves in from the north lake
effect snow showers should come to an end towards Wednesday morning.
Little accumulation expected, with around 1 to 2 inches possible.
Wednesday will be sunny but cold with winds blowing at 10-15 mph and
gusts to near 25 mph, causing it to feel even colder. Highs in the
single digits above zero to mid teens, with the gusty winds making
it feel more like zero to 15 below during the afternoon.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 328 PM CST Tue Jan 31 2017
Arctic air will continue to settle into the Northland from
Wednesday night into the end of the work week as cyclonic upper
level flow will firmly establish itself across the Great Lakes
region. It will generally be dry for the last half of the work
week, although there could be some lake effect snow showers across
the south shore at times. For the most part, it looks like the
focus would be a bit east of Iron county and the Gogebic Range in
NW WI, but there will be some opportunities for a little better
wind direction. In all, amounts are expected to be light. The
upper level pattern will transition to a more westerly flow by 12Z
Saturday, as a shortwave and surface low pressure system
approaches the CWA from the west. While there are some model
differences between the long range models, the consensus is that
we will see a swath of snow spread eastward across the region
Saturday, with light snow lingering into Sunday morning. There
should be at least a couple inches of snow for much of the region,
although amounts look to be too much in question as of this time
given model differences. Snow showers will linger into Monday as
well with westerly upper level flow continuing. Highs will range
from the single digits and teens on Thursday, to the teens and 20s
by the weekend. Overnight lows will range from the single digits
below zero from Wednesday night into Friday night, but then rise
into the single digits and teens for most of the area by the
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 543 PM CST Tue Jan 31 2017
A shortwave and Arctic front will move through the region tonight
and produce moderate to heavy snow showers through late evening
over mainly the southeast half of the Northland including most of
northern Wisconsin. Conditions will mostly be VFR/MVFR but will
drop to LIFR in the heavy snow showers. Clearing was occurring
over parts of northwest Ontario and Manitoba and this will
continue southeast overnight into Wednesday producing VFR
conditions at all TAF sites. A period of gusty winds will also be
possible overnight as the Arctic front moves through.
.PRELIMINARY POINT TEMPS/POPS...
DLH 4 12 -4 10 / 40 0 0 0
INL -8 8 -7 6 / 20 0 0 0
BRD 3 13 -1 12 / 30 0 0 0
HYR 11 15 -2 12 / 50 0 0 10
ASX 13 17 2 13 / 40 10 10 10
Area Forecast Discussion
National Weather Service Green Bay WI
548 PM CST Tue Jan 31 2017
Updated aviation portion for 00Z TAF issuance
and new information added to update section
Issued at 540 PM CST Tue Jan 31 2017
A cluster of intense snow showers will move through central
Wisconsin early this evening. Some of the instability generating
the snow showers resulted from surface heating in an area where
breaks developed in the overcast, so the snow showers will
probably diminish as they head east. However, still expect
localized visibilities well below 1/4SM and a very quick inch or
two of snow in the strongest snow showers. KEAU reported 1/4SM
TSSN a short time ago. The snow showers will mainly affect areas
from ISW-STE-PCZ-ATW-MTW southward. Will re-issue the SPS to
highlight what will likely be a sudden onset to very hazardous
.SHORT TERM...Tonight and Wednesday
Issued at 223 PM CST Tue Jan 31 2017
The latest rap analysis and satellite/radar imagery show low
pressure sliding east over eastern New York, and an associated
trough curving northwest from this low across northern Lake Michigan
to Lake Superior. Light to moderate snowfall with this trough and
also a shortwave located over northeast Wisconsin has finally exited
north-central WI, and the back edge is entering the Fox Valley. Snow
showers of a more scattered variety are moving southeast over
northern Minnesota and western Wisconsin, associated with additional
shortwave impulses. Some of the more intense snow showers could
reach Wood and Waushara counties late this afternoon into early
this evening and drop a quick half inch or inch of snow. Forecast
concerns in the short term include snow shower chances followed
Tonight...Cyclonic flow will remain present through the evening,
with weak shortwave energy passing overhead. These impulses will
likely provide scattered snow showers and flurries through midnight
or early overnight under cloudy conditions. Central and north-
central WI could see up to an additional inch of fluff. Drier air
tries to push in from the west overnight, but with flow off Lake
Superior and a weak surface trough positioned over the Upper
Peninsula, think it will be tough to see clearing take place
across northern WI. Better chances of at least partial clearing
should occur over central and east- central WI late tonight with
the added help of downsloping. Lows mainly falling into the teens
except with a few 20s along the Lake.
Wednesday...That surface trough over the Upper Peninsula will weaken
as it drops south into northern Wisconsin during the morning hours.
Scattered snow showers could accompany this trough over the far
north and will keep a small chance through midday. Areas where
clouds scattered overnight will likely see clouds build again by
late morning as models depict steep low level lapse rates developing
with heating of the day. Wouldnt be surprised to see a few
flurries, but moisture depth does not look deep enough at this time.
Some clearing could return from west to east by late afternoon with
another surge of dry air. Highs ranging from the middle teens in
the far north to the middle 20s in the south.
.LONG TERM...Wednesday Night Through Tuesday
Issued at 223 PM CST Tue Jan 31 2017
Broad area of low pressure over the Hudson Bay and Quebec keeps
Wisconsin in west/northwest flow through the end of the work week.
This sets up a quiet and dry weather pattern with the main focus
on colder temperatures and wind chills. As the low moves east and
weakens this weekend, this allows for a more active setup across
Wisconsin and the focus turns to a couple of weather system to
affect the area.
With high pressure building in Wednesday night drier air will
allow for mostly clear skies and below normal temperatures
through Friday. Winds Wednesday night into Thursday look to back
to the west, keeping the lake effect snow potential north of the
Wisconsin/Michigan border. However, would still expect more clouds
in north-central Wisconsin. With the broad area of low pressure
still situated to the northeast, will see a slight increase in the
pressure gradient as high pressure builds in. While winds don`t
look too impressive, the colder air will be much more noticeable
with this wind. Coldest time looks to be Friday morning with lows
in central and north-central Wisconsin in the -5 to -10 degree
range. This time period will need watching, but right now wind
chill values should stay above criteria, with the coldest
readings between -15 to -20 Friday morning in central and north-
central Wisconsin. Northeast and east- central Wisconsin will not
feel quiet as cold with wind chills of about -10 to -15.
On Saturday, winds shift to the south and we start to see warming
temperatures. Also expect to see increasing clouds ahead of our
next system. Surface low accompanied by mid- level trough and WAA
look to bring a round a snow to the area in the Saturday afternoon
through early Sunday time frame. Models consistently show this
system passing through the area, however run-to-run consistency on
timing and available moisture varies. In the last three runs the
GFS has changed from 0.02" to 0.06" to 0.23" of liquid over Green
Bay for this event. Due to these differences it is still too early
to determine best timing and snowfall amounts.
Following this system the winds will need watching for potential
lake effect snow showers over far north- central Wisconsin through
Sunday. Models have also been showing a weak front pass through
Monday which could bring some very light snow or flurries,
primarily to the north. Moisture still looks limited for this so
kept the mention out of the forecast for now.
Early next week, long range models show a potent system bringing
precipitation to the forecast area beginning Tuesday. Temperatures,
moisture profiles, and corresponding precipitation types could be
a concern with this system. It`s still too early to pin down
details and would expect those to get sorted out in the coming
.AVIATION...for 00Z TAF Issuance
Issued at 540 PM CST Tue Jan 31 2017
There will be considerable cloudiness for about the first half of
the TAF period, with bases varying between VFR and MVFR. A small
area of intense SHSN will pass across central WI, generally south
of the TAF sites. The SHSN could result in brief periods of near
zero visibility. Conditions will tend to improve during the latter
part of the period, though some MFVR ceilings will still be
possible at times.
Area Forecast Discussion
National Weather Service Houston/Galveston TX
905 PM CST Tue Jan 31 2017
At 8 PM, weak low pressure was located near Lubbock with high
pressure over the north central Gulf. Skies remain clear with
temperatures in the upper 50`s to lower 60`s. Surface dew pts have
increased from the past several nights and are now in the
mid/upper 50`s south and upper 40`s north. With clear skies and
relatively light winds, feel there is some potential for fog
tongiht. That said, the KHGX VWP shows 20-25 kts at 1000 feet so
there might be just enough mixing to create low cigs instead of
fog. The SREF has backed off a bit in fog potential tonight and
the HRRR not too aggressive with fog potential either. Current
fcst already contains fog so no changes needed there. Min temp
forecast also looks on target so no changes there. Fcst soundings
a bit more aggressive with cloud cover on Wednesday so beefed up
sky grids a bit. 43
January is coming to a close and it was a warm month. Houston
(Bush) had its 7th warmest January, Hobby had it`s 3rd warmest and
Galveston had it`s 4th warmest January on record. College Station
had it`s 9th warmest January. Average temps were between 5.5 and
7.5 degrees above normal. Galveston only received 0.89 inches of
rain which was the 14th driest January on record. 43
.PREV DISCUSSION... /ISSUED 542 PM CST Tue Jan 31 2017/
A smoke plume from a prescribed burn over eastern Brazoria County
was showing up quite well on radar and was moving over KHGX at
5:30 PM. There is an outside chance the plume could affect
aviation operations at KHOU if the plume drifts northward and
lowers to MVFR levels. Would expect the plume to move out of the
area before the nighttime low-level inversion sets up.
Otherwise, shallow ground fog is expected to form between 06Z and
12Z at or near most of the sites tonight and Wednesday morning.
Model soundings were also indicating MVFR ceilings should form
by around 15Z. Ceilings should lift with good chances of the
ceilings then scattering out by around 18Z. Winds will then become
breezy at most locations inland of the coast.
PREV DISCUSSION... /ISSUED 323 PM CST Tue Jan 31 2017/
Perhaps the main story of the coming week will be the above normal
temperatures, as other aspects of the forecast do not appear to be
terribly impactful. Fog will be possible for at least the next
couple of nights, and chances for showers (and perhaps an isolated
thunderstorm) will come onto the scene from Thursday morning and
continue, at least sporadically, into early next week.
Rest of today through Wednesday night...
Temperatures are tracking relatively close to the forecast today
under mostly sunny skies - only the beginnings of some cloud
streets appear near the coast on satellite (and out the window!).
Expect the fair skies to continue through tonight, and expect some
fog to develop as winds more southerly than southwesterly increase
moisture content across the area. However, winds don`t look to go
totally calm as we lie between high pressure to the east and a
weak, developing surface low over the Panhandle by tomorrow
morning. This will help promote some vertical mixing, and should
(keyword: should) mitigate the severity of any fog that does
Looking for more of the same tomorrow, with high temperatures even
a few degrees higher, as the onshore flow will boost dewpoints and
give us a higher floor to work from with warmer low temperatures.
A subtle upper trough does look to bring in some high clouds,
which could keep things from getting too wild in the the
temperature department, but precip potential Wednesday should
still be virtually nil. Looking into Wednesday night, there will
be potential for fog again, though that may lift to low stratus,
as well. For now, went conservatively and placed fog in the grids.
Thursday through Sunday...
By Thursday morning, the aforementioned weak surface low looks to
open up into an inverted trough, as it weakly makes its way
towards the coast. At first, a passing midlevel trough/vort max
may help boost rain chances, but afterwards things look to be
supported more by surface convergence as the pattern aloft goes
zonal. Without much troughing, and with southwesterly flow at
700/850, not expecting a ton of (or any) instability and stout
capping, so I`m really focusing on showers as the predominant
result of slight chance/chance PoPs. However, forecast soundings
do show very slim CAPE profiles, so if the capping can be
overcome, I can`t entirely rule out an isolated thunderstorm here
or there. Otherwise, without much significant troughing, would
expect the above normal temperatures to continue, and winds to
stay onshore. Basically, as long as you stay dry this weekend, it
will likely be gorgeous weather.
Zonal flow looks to start the week, but by Tuesday both the GFS
and Euro show a more potent midlevel trough digging into the
Rockies, with lee cyclogenesis over Colorado following. This low
will eject into the Great Lakes, draping a cold front into the
southern Plains towards midweek. Right now, the Euro does this a
bit faster, with the front arriving in SE Texas late Tuesday
night into Wednesday morning, while the GFS rolls through
Wednesday morning into early Wednesday afternoon. For now, the
main forcing with this low looks to be far to our north, with only
light showers developing this far south on the front. But, for
what it`s worth, the GFS trended noticeably stronger with the
upper trough, so it may be something to watch in the coming days.
Not a lot of changes with the marine forecast with this latest
package. Light to moderate onshore winds will prevail tonight
and likely persist the next few days. This flow pattern combined
with increased low-level moisture could help in the possible
development of sea fog by late Weds afternoon/night.
Models are keeping with a weak cold front on Friday but at this time
SE TX looks to remain on the very tail end of it. As such a shift to
light east winds may be the best we get out of it, but this could be
helpful in limiting issues with sea fog. Otherwise, fog could remain
a continuing problem through the weekend. 41
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 54 78 58 71 54 / 0 10 10 20 20
Houston (IAH) 57 78 61 75 58 / 0 10 10 30 10
Galveston (GLS) 60 72 62 69 60 / 0 10 10 20 10
Area Forecast Discussion
National Weather Service Mount Holly NJ
946 PM EST Tue Jan 31 2017
Low pressure will consolidate south of Long Island this evening,
then track to the south and east of Cape Cod overnight. A cold
front is forecast to cross our area later Wednesday. High
pressure builds into the Ohio Valley Thursday, then across our
area late Friday and Saturday before shifting offshore. Low
pressure may then track across our area later Sunday into early
Monday, with high pressure following for Tuesday.
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
930 pm update: Tricky overnight forecast continues, with
stubborn snow showers continuing to glance our northern CWA
occasionally and a complex surface pattern being handled quite
poorly by short-term/high-res guidance.
Regarding the former, decided to raise PoPs north of I-78
through late tonight and increase snow accumulations in the
southern Poconos and adjacent Sussex County, NJ. Not expecting
more than a tenth of an inch or so in these areas, but still
enough to cause some travel problems on area roads when a snow
shower moves through.
Regarding the latter, temperatures and winds continue to be a
challenge with the hourly grids, as the southern CWA is quickly
reaching forecast lows with calm winds and only partial/high
cloud cover in place. May even see some patchy fog in favored
locations in S NJ tonight. Meanwhile, the northern CWA has
temperatures holding fairly steady, except for the Mount Pocono
area, where a slow climb has been observed. Low confidence in
low temperature forecast tonight, but with increased cloud cover
expected later, thinking temperatures will not fall much
farther in most locations. Meanwhile, winds are generally calm
at this time, but guidance is insisting upon light westerly flow
setting up overnight -- not buying it based on the near-
negligible progression of the wind shift observed this evening
in central PA. Think this will require the push of the upstream
system moving through the area tomorrow.
630 pm update: Latest surface analysis indicates a rather
complex scenario across the CWA this evening. Several boundaries
are traversing the area and are wreaking havoc with most
sensible weather element forecasts this evening. The first
boundary is an increasingly ill-defined warm front draped just
north of the Mason-Dixon Line. Meanwhile, a north-south boundary
is developing on the east side of Chesapeake Bay as nocturnal
cooling commences in the partial clearing occurring in Delmarva.
Additionally, a weakening wind shift exists to the north of
Chesapeake Bay just west of the CWA. Winds favor a light E/NE
direction north of the warm front, are nearly calm south of the
warm front and east of Chesapeake Bay, and more W/SW west of
the boundary to the north of Chesapeake Bay. Temperatures are
similarly messy, with rapid cooling occurring in S NJ and
Delmarva with favorable partial clearing and nearly calm winds
and holding steady north of the warm front in the thicker
clouds. Owing to the developing surface low south of Long Island
this evening, think it is going to be very tough for the E/NE
flow regime north of the warm front to retreat northward
tonight. Short-range models are handling these regimes poorly,
particularly the northward retreat of cool near-surface air.
With little guidance of value, grids are mainly being adjusted
based on current trends, extrapolation, and subjective (read: my
completely manual) bias correction to the most reasonable
guidance available. Expect multiple updates this evening as all
of this plays out.
Another problem is the lingering precipitation in SE PA and NW
NJ, with most hi-res guidance too far north with the southern
fringe of the precipitation this evening. Based on current radar
trends, suspect at least a slight chance of precipitation exists
through midnight generally north of I-78, with most
precipitation falling as snow in the southern Poconos. May see a
little sleet or light rain/sprinkles mix in with the snow in
the Lehigh Valley as well. Not expecting much additional
accumulation, but even a dusting can make travel difficult,
especially overnight...so this will be something we will be
monitoring closely this evening.
Previous discussion below...
A clipper system continues to move through the northern Mid-Atlantic
and Northeast states this afternoon. The primary surface low to our
northwest (over western NY) is weakening as a secondary low develops
off the NJ coast (near the system`s triple point). The coastal low
will move quickly to the east-northeast toward Nantucket this
evening, then hook northward into the Gulf of Maine overnight. A
weak cold front with this system will likely dissipate before it
ever makes it to our region.
The position of the warm front was just to the south and east of I-
95/NJ Turnpike at 3 PM this afternoon and clearly evident from
surface observations. In the warm sector south of the front,
temperatures are in the mid/upper 40- (even a few 50s in Delmarva)
with a breezy SW winds. Observations situated to the north of the
boundary range from the mid 20s to the mid 30s (even teens at KMPO)
with a light E or NE wind.
PoPs were lowered in earlier updates today for this afternoon as the
organized synoptic lift from this system has already shifted
downstream of the area. In wake of the steadier snow locations in E
PA and C/N NJ saw this morning, scattered showers have developed
along and east of the Delaware Valley this afternoon. Forcing for
this activity looks to be provided by weak low-level convergence
near the warm front in addition to DPVA ahead of a shortwave trough
in the low-/mid-levels. HRRR soundings also indicate weak elevated
instability rooted above the warm nose at 850 mb. Snow grains, ice
pellets, and rain have been reported with this activity. Once these
showers move off the coast by sunset, there should be little in the
way of precip tonight. However, kept in low chances for snow showers
N/W of the Fall Line for this evening (HRRR has been consistent in
showing isolated showers developing toward RDG-ABE-MPO early this
evening) and slight chance PoPs for the southern Poconos overnight.
Forecast temperatures N and W of I-95 were a bit tricky for tonight
as they won`t follow a typical diurnal curve . Low temperatures in
these locations will likely occur this evening before the warm front
moves through. A SW wind in wake of the fropa will be accompanied by
a rise in temperatures.
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
930 pm update: Made some changes to the short term forecast.
Made subtle increases in PoPs for Delmarva and adjacent far
southern NJ tomorrow afternoon based on latest RAP/WRF
simulations. Based on other operational guidance (e.g.,
GFS/CMC), these PoPs may need to be extended into Wednesday
night as well, but refrained from doing so for now.
Additionally, forecast soundings suggest marginal but sufficient
convective lift for showery precipitation in SE PA/N NJ. Given
closer proximity to the shortwave trough moving through N PA and
southern New England tomorrow, expect at least isolated showers
(likely snow in the southern Poconos and adjacent higher
elevations of Sussex County, NJ) in these areas. Latest HRRR is
strongly suggestive of this scenario playing out by early
afternoon. Expanded slight chance PoPs south/east toward the
Fall Line and may even affect portions of the I-95 corridor
(though here temps will be warm enough for rain).
630 pm update: Based on the latest ensemble/high-resolution
guidance, thinking that at least isolated showers are a decent
bet tomorrow across the area. Will be looking closely at this
time range and may make some adjustments to PoPs in the short
term period for the 930 pm update.
Previous discussion below...
Yet another clipper system embedded in an active northern jet stream
will pass through the Great Lakes region and Northeast states on
Wednesday. The forcing from this system looks to be mainly confined
to the north of our CWA. However, a cold front approaching from the
NW may be accompanied by isolated to perhaps scattered showers
develop across eastern PA and NW NJ during the afternoon. Similar to
what we saw yesterday, forecast soundings indicate steep lapse rates
and marginal instability (50-100 J/kg of MUCAPE), which is enough to
fuel the convective activity. Temperatures tomorrow afternoon will
be warmer than yesterday thought, so the potential for localized
snowfall accumulation would be confined to the higher elevations in
NE PA and NW NJ.
Highs range from the mid 30s in the Poconos to mid/upper 40s along
and E of I-95. A few locations in mid Delmarva and SE NJ has a
decent shot at reaching 50F.
.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
Synoptic Setup...A closed low centered near Hudson Bay Wednesday
night and Thursday will maintain a trough into the Northeast. This
looks to shift around a bit through Friday with the southern extent
of the trough potentially relaxing and allowing the flow to turn
more zonal. A cold front moves through late Wednesday, then ridging
in the interior West allows for strong high pressure in the Midwest
to expand east-southeastward into the weekend. This should allow a
colder northwesterly flow to occur, with the center of the surface
high forecast to move over our area later Saturday. The evolution of
the flow aloft over the weekend and early next week is less certain,
as there is quite the variability in the model/ensemble guidance.
There may end up being to much energy in the West, which allows more
zonal flow to even ridging in the East. We used a model blend for
Wednesday night through Friday, then blended in the 12z WPC Guidance
thereafter. Some adjustments were then made following additional
collaboration with our neighboring offices.
For Wednesday night and Thursday...An expansive upper level trough
centered near Hudson Bay will maintain the southern portion of the
trough across the Northeast and into the Mid Atlantic. A cold front
will shift east of our area to start Wednesday night with perhaps a
few snow showers mainly across the far north early. There is plenty
of channelized vorticity forecast to be moving through the flow
across our northern areas, and this may keep the cloud cover in
place for some areas longer. Surface high pressure will build
southeastward from the Northern Plains Thursday with increasing
northwesterly flow across our region. This combined with cooling may
allow for some lake effect snow showers to reach down to the Pocono
region. Otherwise, this time frame is anticipated to be dry.
For Friday and Saturday...A more pronounced short wave looks to dive
southeastward from the Great Lakes later Friday. This is reflected
at the surface by a trough which should cross our area later Friday,
with additional cold air advection in its wake. There does not
appear to be much in the way of forcing or additional moisture to
produce precipitation, other than perhaps some flurries or snow
showers nearing the Poconos with any possible lake effect
connection. High pressure is forecast to slowly build into the Mid
Atlantic during Saturday, however a tight pressure gradient coupled
with cold air advection may lead to a blustery Friday. The winds
then subside later Saturday as the center of high pressure arrives.
For Sunday through Tuesday...The flow may end up turning mostly
zonal during much of this time frame as significant energy moves
across the Western states. There however is quite a bit of
uncertainty with the overall flow regime as a stronger short wave
traversing the southern stream could lead to trough amplification in
the East at some point. Looks like much of the guidance has backed
away from this possibility, with now a weak system moving through
later Sunday. It appears that there may be so much energy out West
that the downstream flow remains zonal to even some ridging. We will
keep just some low chance Pops in for later Sunday and Sunday night
given the uncertainty with the details as the larger scale features
need to be resolved. As of now, low pressure and an associated cold
front moves through later Sunday, then high pressure builds in later
Monday into Tuesday. It is possible that early next week could offer
a significant warm up if a strong trough develops well to our west,
which would result in plenty of southerly flow and warm air
advection overspreading the East (at least for a time).
.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.
00Z update: General VFR conditions anticipated through tomorrow,
although conditions may flirt with MVFR at KRDG and KABE during
the day. Given the expected winds tomorrow and residual dry air
aloft, suspect it will be difficult for ceilings to lower to
MVFR, even within/near isolated showers that may develop. Winds
tonight will be rather chaotic, but should remain at or below 8
kts. Winds are forecast to increase and become gusty after
sunrise tomorrow with directions mostly from the west and gusts
approaching 20 kts.
Wednesday night and Thursday...VFR overall. West-northwest winds
less than 10 knots Wednesday night, then increasing to near 15 knots
Thursday with gusts up to 25 knots (diminishing Thursday night).
Friday and Saturday...VFR as high pressure gradually arrives.
Northwesterly winds near 15 knots with gusts up to 25 knots
Friday, then diminishing some Friday night into Saturday.
Sunday...Low confidence regarding details as a storm system may move
through. Therefore, MVFR or lower conditions could develop
especially later in the day and at night with some possible
930 pm update: SCA conditions (high seas) ongoing in the coastal
waters this evening. Latest guidance has slowed the trend in
increasing winds toward very late tonight and (more likely)
tomorrow. Reduced winds overnight accordingly, but still expect
SCA winds to materialize by tomorrow morning. Observed seas are
about 1-2 feet higher than forecast this evening, so raised
these through tomorrow morning as well. Previous discussion
Some changes were made to the SCA headlines. First, the SCA was
canceled for the DE Bay. After a breezy morning, winds in the Bay
have dropped off to below 20 kt. Next, the SCA for our northern most
zone (ANZ450) was pushed back until 11 PM this evening. Winds north
of a warm front are very light, which has kept seas in the 2-3 ft
range. Expect SCA conditions to begin overnight in the coastal
waters of C NJ.
Winds will turn more W-SW tonight and decrease from S to N in our
coastal waters. Expect winds to fall below 25 kt off S NJ and DE
early tonight but seas will still be elevated around 5 ft through
Wednesday morning. Winds look to pick up in our far northern zones
as a coastal low deepens over the Gulf of Maine. Gusts 25-30 kt are
likely to develop overnight tonight into Wednesday morning in our
northern waters (ANZ450/451).
Wednesday night...The conditions are expected to be below Small
Craft Advisory criteria.
Thursday through Saturday...Periods of Small Craft Advisory
conditions are expected, especially Thursday and then again Friday
afternoon through Saturday morning.
Sunday...While there is uncertainty with a possible storm system
arriving, the conditions are currently anticipated to be below
Barring any surprises these next 8 hours (4P to midnight)
Allentown`s temperatures today should average below normal, and
this will be the first below normal day since January 10.
PHL is probably going to average normal or just above, and Atlantic
City clearly above normal. PHL and ACY have not recorded a
below normal day since the 10th of the month (21 consecutive
days aoa normal).
PHL will have the 15th warmest January on record (POR 1874)
with a monthly average of 38.4 degrees, 5.4 degrees above the
normal of 33 degrees.
ACY will have the 19th warmest January (POR 1874) on record
with a 38.3 average or 5.3 degrees above the norm of 33.
ABE will have the 8th warmest January on record (POR 1922) with
about a 34.7 degree average or nearly 7 degrees above the
normal of 27.8 degrees.
Allentown was tied for 12th least snowy January on record with 2.1
MARINE...Small Craft Advisory until 1 PM EST Wednesday for ANZ452-453.
Small Craft Advisory until 6 PM EST Wednesday for ANZ450.
Small Craft Advisory until 6 PM EST Wednesday for ANZ451.
Small Craft Advisory until 7 AM EST Wednesday for ANZ454-455.
Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
709 PM EST Tue Jan 31 2017
00z water vapor and H4 RAP analysis show a continued benign
weather pattern for the Florida peninsula. Main northern
stream flow is removed well to our north...leaving a
generally zonal and dry mid/upper level flow across the
eastern Gulf of Mexico and FL peninsula.
The 01/00Z KTBW sounding profile continues to also sample a
very dry atmospheric column through the extent of the trop.
With this profile...skies will remain mostly clear through
the overnight...with just some passing thin cirrus from time
to time over the southern counties.
Although the ridge axis is over the region and winds...the
low level column has moderated a bit over the past 12-18
hours...and this will help keeps temps a bit warmer than
Monday night. Therefore...although it will be seasonable
cool tonight, we are not anticipating any potential for
frost, even across the interior northern counties. Beyond
tonight...temperatures will only continue to moderate slowly
Will likely see some patchy fog develop after 07-09Z
overnight...mainly to the north of the I-4 corridor. Most
statistical and deterministic guidance members agree on
this northern bias to fog potential. Generally
speaking...dense fog is not expected for most spots,
however, if any dense fog is going to develop, the most
likely locations will be Citrus/Levy counties. Will monitor
these zones closely late night.
Beyond minor edits, see little opportunity at this time to
improve the inherited forecast of dry conditions and
seasonable temperatures through the middle of week.
Have a great Tuesday evening everyone!
VFR conditions prevail through the rest of the evening
across west-central and southwest Florida, under mostly
clear skies and light winds. Patchy and shallow MVFR fog is
possible after 09Z...mainly for KLAL and KPGD, however, most
of the fog potential tonight will remain to the north of the
I-4 corridor. Any patchy fog is gone by 14Z Wednesday,
followed by prevailing VFR conditions and winds under 8
knots through the duration of the Wednesday daylight hours.
.Prev Discussion... /issued 209 PM EST Tue Jan 31 2017/
..Warming Trend Expected The Rest Of The Week...
SHORT TERM (Tonight - Wednesday)...
Zonal flow aloft along with high pressure at the surface will remain
over the forecast area through Wednesday. Dry stable conditions will
support clear skies through the period. With the surface ridge axis
becoming aligned from the western Atlantic west across the central
peninsula and into the eastern Gulf, the boundary layer flow will
become southeast to southwest from south to north across the
forecast area which will allow the cool dry air mass to slowly
modify leading to milder temperatures tonight compared to this
mornings, with lows falling in the lower to mid 40s across the
Nature Coast, mid to upper 40s central interior zones, and upper 40s
to around 50 south and along the coast.
Ample ground moisture coupled with the clear skies and light winds
will support some patchy fog development late tonight into early
Wednesday morning over interior locations, especially in the fog
prone area of the Nature Coast, and across southwest Florida and
will depict and include a mention of in the grids and zones.
On Wednesday another very pleasant dry day with ample sunshine is
expected. Temperatures with continue to warm with readings returning
to near seasonal level with highs topping out in the lower to mid
70s during the afternoon.
LONG TERM (Wednesday Night - Tuesday)...
Benign mild dry weather expected across the forecast area in the
mid/long range period.
A strong rex block will be located over the eastern Pacific...while
downstream of the block, U/L flow will be quasi-zonal across the
CONUS with a mean trough over the eastern U.S.
Strong southern stream flow will undercut the rex block across
California...merging with the northern stream U/L flow over the
central U.S. exiting off the mid Atlantic coast. Main flow will
remain north of the forecast area with southern extreme of westerly
flow across the Gulf of Mexico and Florida peninsula.
A weak U/L disturbance will move rapidly across the central U.S. on
Friday and off the mid Atlantic coast Friday night with an
associated cold front stalling across north Florida as it becomes
parallel to the U/L flow. Surface high pressure will hold over the
Florida peninsula Thursday and Friday with temperatures about 5
degrees above climatic normals each day. A reinforcing area of
Canadian high pressure will build north of the region Friday night
and Saturday with the Florida peninsula on the southern periphery.
Slightly cooler temperatures advect across the area...but will
only drop to near climatic normals.
High pressure will move over the western Atlantic on Sunday with
easterly boundary layer flow across the peninsula moderating
temperatures. Next slightly stronger U/L disturbance will push across
the Tennessee Valley Sunday and off the mid Atlantic coast Sunday
night. Associated cold front will also stall across north Florida as
it becomes parallel to the U/L flow.
High pressure will be centered over the Florida peninsula Sunday
night and Monday, and will move east of the Florida peninsula Monday
night and Tuesday with southeast boundary layer flow developing
across the forecast area. This will advect warm moist air back over
Upstream, a much stronger U/L disturbance is expected to move over
the central plains Monday night and Tuesday as an amplifying L/W
trough begins to take shape over the plains and the Rockies. A
strong area of low pressure is expected to develop along the lee
side of the Rockies and push across the mid Missouri valley.
Tranquil boating conditions will continue over the Gulf waters
tonight through the remainder of the week with light winds and
slight seas as high pressure remains in control, with a weak
pressure pattern supporting an onshore sea breeze component
developing along the coast each afternoon. During Friday night into
Saturday stronger surface high pressure building in over the mid
Atlantic coast will help to tighten the gradient some which will
lead to an elevated easterly flow with a period of exercise caution
possible Saturday and Saturday night, before winds diminish
again on Sunday as the gradient weakens and high pressure builds
in over the region.
A few hours of critically low humidity values below 35 percent
will be possible over central interior zones north into eastern
sections of the Nature Coast during Wednesday afternoon. Despite
the low humidity, low ERC values and sustained winds of less than
15 mph will preclude Red Flag conditions. A slow increase in low
level moisture is expected the remainder of the week with no other
fire weather issues expected.
.Preliminary Point Temps/PoPs...
TPA 51 72 56 75 / 0 0 0 0
FMY 49 77 57 80 / 0 0 0 0
GIF 47 75 52 78 / 0 0 0 0
SRQ 51 72 53 75 / 0 0 0 0
BKV 43 74 44 76 / 0 0 0 0
SPG 54 71 58 74 / 0 0 0 0