Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/30/16
Area Forecast Discussion
National Weather Service Caribou ME
911 PM EST Tue Nov 29 2016
.SYNOPSIS...
Low pressure will track across the region Tonight into Wednesday.
Another area of low pressure will move through Wednesday night
into Thursday.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
9:12 PM Update...A secondary low is forming in the Gulf of Maine
in the area of greatest pressure falls on the order of 5mb/3 hrs.
Steady precipitation is falling across the CWA, although there is
a sharp cutoff in the north with only very light snow falling in
parts of the Saint John Valley, and probably very little or no
snow out toward Estcourt Station. The precipitation type is a big
issue with all rain across the Downeast Region, and all snow as of
9 PM from Millinocket north to the Saint John Valley. The
correlation coefficient and spotter reports confirm that there is
a transition zone across southern Piscataquis County east into
northern Washington County where the snow has either mixed with or
changed to rain and freezing rain. Many reports have come in this
evening, but no reports of sleet. The snow versus rain and
freezing rain has been gradually advancing to the north this
evening, and will likely work north into parts of northern
Penobscot and southeast Aroostook County over the next couple of
hours. It still appears like the bulk of the steady precipitation
will be exiting the area to the east during the predawn hours (4-6
am). Made some adjustments mainly to the snowfall totals based on
all the observations this evening and latest radar and near term
model trends.
A winter storm watch was issued between updates for northern
Aroostook County for late Wednesday night into Thursday where 8 to
12 inches of snow is expected.
Previous discussion...
Winter Weather Advisories remain in place with the ice potential
moved a bit further n and snowfall amounts pulled back across the
western and central areas.
Sfc analysis showed cold air damming across the interior downeast
region beginning to weaken as the high retreats to the e. Low pres
apchg from the sw will move off the Maine coast and run across the
Gulf of Maine tonight. Precip was in the form of snow across the
far north and a mix of snow/freezing rain in the Central
Highlands per the webcams and obs. Frozen precip has now gone to
rain across the downeast and coast as dewpoints rise into the 30s.
Enhanced banding seen on the MRMS and radar coverage across the
northern areas indicative of heavier snow or even sleet as seen in
southern Piscataquis County. First round of precip to move through
this evening w/a good round of snow for northern areas mainly n of
HUL TO MLT line. Some portions of the Central Highlands could pick
up close to 0.20 inches of ice before ending later tonight. A second
round of precip to move across the downeast region w/the low w/up to
0.75 inches of rain by midnight. This is due to a good 50 kt jet
moving in from the ssw. As the low pulls away, the RAP and HRRR
indicate some wrap-around moisture in the form of snow occurring
back across northern Maine overnight before ending Wednesday
morning, which will add to the snow totals. Temps will warm for a
time overnight into the low and mid 30s.
Caution needs to heeded here as snowfall rates up to 1"/hr this
evening will lead to some quick snowfall amounts. Timing will be
key here. Decided to blend in WPC`s guidance this round yielding
5-8 inches across northern Maine w/in a 12+ timeframe. If
snowfall rates continue longer at the aforementioned rate, then
amounts will need to be raised which could tip things into the
warning criteria. Decided on 2-4 inches for the Central Highlands
w/an inch or less s of the Lincoln-Topsfield region.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/...
One area of low pressure will be moving away to the east on
Wednesday as another low begins to take shape near southern New
England. Between the two, we will remain cloudy with some spotty
showers, or flurries across the north. Precipitation from the new
low will begin to spread across the area from southwest to northeast
Wednesday evening, as rain Downeast and then snow across the north.
Snow over the north and rain Downeast will continue into early
Thursday morning. Boundary layer thicknesses are indicating a bit of
sleet and freezing rain may mix in over some central areas,
especially across the central highlands. As the low center tracks
along the coast precipitation should taper off to rain showers
Downeast around mid to late morning Thursday then taper off as snow
showers over the north by early Thursday afternoon. Thursday night
into Friday will then remain cloudy with some scattered rain and
snow showers over the north and a partly to mostly cloudy sky
Downeast as the upper trough slowly moves across the north and
dissipates.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
A trof both at the surface and aloft will linger across the
area Friday night through Saturday with the chance of a few snow
showers, mainly across northern and central areas. The trof will
begin to move off to the east Saturday night and Sunday with
partly cloudy skies and dry conditions expected. High pressure
will begin to move east on Monday. Another system may bring a few
snow showers by Tuesday. Temperatures through the period are
generally expected to remain below normal for this time of year.
&&
.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
NEAR TERM: mostly LIFR to IFR overnight. Have added in some sly
wind shear at the Downeast terminals for late this evening.
Conditions will mostly improve to MVFR by late morning or early
afternoon Wed.
SHORT TERM: Conditions will lower to IFR from south
to north Wednesday evening then remain IFR into early Thursday
morning. Conditions may improve to MVFR then VFR Downeast Thursday
afternoon but will likely remain MVFR across the north. MVFR
conditions over the north and VFR to MVFR conditions Downeast are
likely Thursday night through Friday.
&&
.MARINE...
NEAR TERM: the wind continues to increase this evening with the SCA
for the intra coastal waters looking good for the overnight
w/sustained winds of 20 kts or so and gusts to 25 kts. Gales
remain up for the outer waters as winds of 25-30 kts could easily
gust to 35 kts as a 45-50 kt jet from 925-850 mbs moves over the
waters late this evening.
SHORT TERM: A gale for the offshore waters and SCA for
the intracoastal waters may be needed for east winds ahead of low
pressure Wednesday night. Winds may diminish for a period of time
Thursday, then increase to SCA in west winds Thursday night before
diminishing again on Friday.
&&
.CAR WATCHES/WARNINGS/ADVISORIES...
ME...Winter Weather Advisory until 4 AM EST Wednesday for
MEZ001>006-010-011-031-032.
Winter Storm Watch from late Wednesday night through Thursday
afternoon for MEZ001-002.
MARINE...Small Craft Advisory until 7 AM EST Wednesday for ANZ052.
Gale Warning until 2 AM EST Wednesday for ANZ050-051.
&&
$$
Near Term...CB/Hewitt
Short Term...Bloomer
Long Term...Duda
Aviation...CB/Hewitt/Bloomer
Marine...CB/Hewitt/Bloomer
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
932 PM EST Tue Nov 29 2016
.SYNOPSIS...
Deep moisture will return from the west along an approaching cold
front tonight through Wednesday. The front will move east of the
area Wednesday night and dry high pressure will set up Thursday
through Saturday. Moisture will return Sunday into Monday ahead of
another developing low pressure system to the west.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
As of 930 PM EST...Did a quick update to adjust PoPs to latest radar
trends. The 02z SPC mesoanalysis page shows a tongue of 500 J/kg of
MUCAPE extending from the west into the Upstate. This may be helping
the improving isentropic lift to produce a band of shower lifting NE
this evening. An isolated rumble of thunder cannot be ruled out as
this activity crosses the area, but severe storms are not expected.
The activity out to the west associated with the next cold front
will take its time shifting east, with rain entering the Smokies
around 9-10 AM. Temps/dewpts/winds are on track.
As of 700 PM EST...A weak frontal boundary was analyzed roughly
along the I-85 corridor and has stalled. Isentropic lift is already
ramping up along the front, with the radar showing weak returns
increasing in coverage across northern GA into the western Upstate.
The high-res models agree on a round of showers lifting NE thru the
area this evening. Earlier runs of the HRRR showed rather robust
simulated reflectivity. And the NAM and GFS do show as much as 500
J/kg of MUCAPE across the area this evening. So if the forcing can
tap into some of that instby, an isolated tstm cannot be ruled out.
Will keep a mention of slght chc for thunder with the PoPs tonight.
Temps will hold nearly steady or fall only slightly overnight under
clouds and LLVL WAA.
For Wednesday, A potent vorticity maximum will rotate thru the base
of a broad, long-wave trough and lift NE thru the TN/OH Valleys.
This energy will be accompanied by a strong upper jet and associated
upper divergence atop the region. Another cold front will approach
from the west, and be accompanied by a solid band of precip over the
TN Valley to the central Gulf Coast. The CAMs hint at a potential
quasi-linear convective system approaching the NC mountains around
midday, but generally have that fall apart. The GFS has almost no
CAPE across the area in front of that line, while the NAM does have
pocket of about 400-600 J/kg of MUCAPE across the Upper Savannah
Valley. Of course, if anything relatively deep can set up, shear
will be more than adequate to keep things organized Wed aftn. So the
Day 2 Marginal Risk for severe weather looks good. The other issue
is gusty winds, as another SWLY LLJ traverses the area ahead of the
front late tonight thru Wed aftn. A wind advisory is in effect for
most of the NC mountains from midnight tonight thru Wed aftn.
Temperatures will run well above normal.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 200 pm EST Tuesday: We`ll see some lingering precip across the
area at the start of the period, generally between 00-06z Thursday,
but the front will be rapidly exiting the area as the upper low
pushes east across southern Canada and the occluded surface low and
front lift northeast. Southwest flow aloft continues over the area
at the start of the period with modified surface high pressure
sliding east across the Southern Plains and beginning to ridge into
the Southeast. The biggest sensible weather impact for Thursday will
be the markedly cooler temperatures behind the front...a good 10
degrees colder than highs tomorrow...but still a little above
seasonal normals. The CAA will continue on Friday as a shortwave
passes across the area early in the day, with highs another handful
of degrees cooler still and below seasonal normals. Continued dry.
Meanwhile a strong system will deepen over the Desert Southwest,
inducing downstream ridging over the Plains that will be beat back
down by a shortwave diving out of Canada into the northern Plains.
This will be our main weather-maker for the extended.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 215 pm EST Tuesday: Ah, the extended. This has been quite the
puzzle and more than a little frustrating for the last few days but
the good news is that the ECMWF has actually done a flip with the
12z run and is lining up really well with the GFS, which was the
preferred model yesterday. So what we have now is that the northern
Plains shortwave will slide east, while the Desert Southwest (well,
more like northwest Mexico) upper low continues to remain cutoff,
spinning in place, to affect us toward the very end of the period.
The first wave of moisture will lift into the Southern Plains late
Saturday and spread east overnight and into Sunday. The shortwave
moving through the Ohio Valley will act to suppress moisture to the
south, with some low-end QPF (but high pops) at least spreading into
our GA/SC zones during the day on Sunday. There may be some moisture
attendant with the shortwave itself to affect the northern mountains
and with the cold air in place, continued the mention of rain/snow
mix or snow depending on temperature, but with such low QPF over the
mountains would not expect much. Temperatures will be held well
below normal on Sunday.
Monday into Tuesday, both models have a surface high pressure
crossing the Appalachians and ridging down the Eastern Seaboard,
though the ECMWF is centered much farther north in more of a
classical CAD with the GFS more of a hybrid CAD (with some associated
QPF already across the area again Monday night. With this, the
former upper low will lift northeast and be absorbed by another
trough pushing into the west coast, with a rapid response in
downstream ridging over the Appalachians Monday night, with a
corresponding increase in temperatures on Tuesday as the warm front
lifts north ahead of the trough. At this point, the GFS is a little
faster with lifting the warm frontal precip across the Carolinas,
but the overall pattern is fairly similar. For now have kept chance
pops through Tuesday before the system exits late in the period, and
of course we`ll refine this through time. And it`s that time of
year, so right now we`re looking at at least some mix or snow in the
northern mountains each night. WPC snow probabilities for the
extended are low but non-zero across western NC.
&&
.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
At KCLT and elsewhere: A weak front has lain over the area, just
south of the piedmont TAF sites. Another wave is developing to the
west, and will produce increasing moist SWLY low-level flow tonight.
Another front will bring another band of showers and possibly a few
TSTMS on Wednesday. In the meantime, cigs are expected to lower back
to IFR or possibly LIFR overnight, then start to improve with the
arrival of precip from the west Wednesday morning. The high-res
models agree on a round of showers lifting from the SW this evening
across the area. So will mention -SHRA at all sites with possibly
some vsby restrictions. There may be enuf instability for isolated
TS overnight, but confidence is too low to mention in any of the
TAFs at this time. South to southwest winds will remain generally in
the 5-10 kt range overnight, then increase and become gusty by
around 14z. There may be some LLWS concerns before daybreak,
especially at KCLT, where the LLJ only 1000-2000 ft AGL will
increase to around 40 kts before deeper mixing commences.
Outlook: Dry air start to filter in behind a passing cold front
Wednesday evening, with dry high pressure returning for Thursday
thru Saturday.
Confidence Table...
02-08Z 08-14Z 14-20Z 20-00Z
KCLT High 87% Med 61% High 81% Med 68%
KGSP High 87% Med 73% High 80% Med 63%
KAVL Med 75% High 91% Med 66% High 81%
KHKY Med 73% Low 54% Med 79% Med 79%
KGMU High 93% High 83% Med 79% Med 63%
KAND Med 77% Med 69% High 88% Med 63%
The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables and ensemble forecasts
are available at the following link:
www.weather.gov/gsp/aviation
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...Wind Advisory until 7 PM EST Wednesday for NCZ033-048>053-058-
059-062>064-505.
SC...None.
&&
$$
SYNOPSIS...HG
NEAR TERM...ARK/JAT
SHORT TERM...TDP
LONG TERM...TDP
AVIATION...ARK
Area Forecast Discussion
National Weather Service Houston/Galveston TX
907 PM CST Tue Nov 29 2016
.DISCUSSION...
Based on radar fine lines, the cold front was located from near
KJAS in east TX to KLVJ (Pearland) and then SW to KBYY (Bay City).
The front appears to be moving fairly slowly, maybe 5 mph. Latest
HRRR model trends have the front pushing off the coast after
06z/midnight and then accelerating south. Radar still shows a few
lines of showers/storms in the Gulf but remain rather weak due to
capping aloft evident by ACARS soundings as well as the 00Z CRP
sounding. CRP sounding had temps of 10C at 700mb, 20C at 850mb.
Surface obs also showed a few isolate areas of fog developing
south of the front. Mainly visibility has dropped to around 3 to
5 miles along the coast and just off shore. The front should erode
the fog the next couple of hours. We are certainly not expecting
dense fog to quickly form like last night.
Main changes to the forecast were to just update for on going
trends with the front pushing south. Minimum temps may not be
quite as cool along the coast since it will take some time for
cold air advection to take place.
As for this coming weekend, I think the previous discussion covers
the potential rain event. Despite some model differences, I`ll
sum up by saying "It gonna rain".
Overpeck
&&
.PREV DISCUSSION... /ISSUED 535 PM CST Tue Nov 29 2016/
AVIATION...
For most sites, dry air on northwest flow should keep fog from
being an issue tonight. However, with a boundary stalled just
inland of the Gulf shore, this seems unlikely at GLS, which
should see some fog develop before gusty northwest winds on a cold
front blast dry air in. Went with MVFR conditions now, on chance
that stalled boundary drifts southward this evening, but potential
for IFR definitely exists and may be cause for later amendments.
Other challenge will be how and when winds get gusty as cold front
works through. In collaboration with the CWSU, agree on bringing
in gustier winds a little after winds just off the surface
increase. Along with that, the narrow band of clouds near the
coast should also depart the area.
PREV DISCUSSION... /ISSUED 408 PM CST Tue Nov 29 2016/
DISCUSSION...
The frontal boundary responsible for thunderstorms across parts
of the Brazos Valley and Piney Woods earlier this morning as it
lifted north is now sagging south across the region this
afternoon. Surface analysis shows this boundary snaked from Edna
to Katy to Dayton, with satellite imagery showing enhanced cumulus
developing along the boundary. Despite this, convection this
afternoon has been largely limited as warm air advection at 850
and 700 MB has resulted in a strengthening cap across the Houston
metro. Low level warm air advection today has also resulted in a
few locations reaching or setting record high temperatures, with
Houston Intercontinental having reached at least 84 degrees as of
4 PM (which would exceed the record of 83 set in 2006).
Cannot rule out a few showers developing underneath this cap as
the boundary slowly sags towards the coast this afternoon, with
scattered showers and thunderstorms blossoming over the coastal
waters and extreme southeastern counties this evening as a
secondary cold front across North and Central Texas sweeps off the
coast this evening and tonight. May see a few of the storms across
the coastal waters become strong to marginally severe, but this
activity will continue to move into the northern Gulf and away
from the Upper Texas coast with the associated front. Until the
cold front moves off the coast tonight and ushers in drier air,
may see some patchy fog across the bays and nearshore waters with
warm, moist air pooled right along the coast. Otherwise, expect
overnight lows in the low 40s to mid 50s.
Surface high pressure building into the region in the wake of
tonight`s front will result in dry, cooler weather for the region
on Wednesday and Thursday. Elevated north winds (15-20 MPH) and
relative humidity values falling to near 25 percent during the
afternoon tomorrow will result in elevated fire weather conditions
for most inland areas tomorrow afternoon, but decreasing winds on
Thursday will help limit overall fire weather concerns. Expect
highs Wednesday and Thursday to be in the 60s with lows ranging
from the upper 30s across the extreme northern counties to mid 50s
along the coast.
Attention then turns to the upcoming weekend as energy from an
upper trough approaching from the west cuts off over northern
Mexico. Surface high pressure shifting into the southeastern US on
Friday will allow moisture to begin surging into the region, aided
by the development of a coastal trough along the Middle Texas
coast. Southwest flow aloft combined with enhanced low level
convergence from the coastal trough will result in periods of
showers and thunderstorms across Southeast Texas in the Saturday
through Monday timeframe. With precipitable water values climbing
to near 1.7 inches along the coast, have increasing concerns for
heavy rain to impact parts of the Upper Texas coast. Medium range
guidance has come into better agreement on the overall upper
pattern evolution, but still offers different timing on when the
upper low will lift across Texas and placements on the coastal
trough that develops (which would affect which areas see the
heaviest rain). Regardless, this weekend looks cool, wet, and one
to watch for heavy rain impacting parts of the Upper Texas coast.
Huffman
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 46 65 40 66 45 / 0 0 0 0 0
Houston (IAH) 54 67 42 67 46 / 10 0 0 0 0
Galveston (GLS) 61 68 54 65 58 / 20 0 0 0 0
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION from 6 AM CST Wednesday
through Wednesday morning for the following zones: Coastal
waters from Freeport to the Matagorda Ship Channel out 20
NM...Coastal waters from High Island to Freeport out 20
NM...Matagorda Bay.
Small Craft Advisory from 6 AM to noon CST Wednesday for the
following zones: Waters from Freeport to the Matagorda Ship
Channel from 20 to 60 NM...Waters from High Island to
Freeport from 20 to 60 NM.
&&
$$
Discussion...39
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1026 PM EST Tue Nov 29 2016
.UPDATE...
Issued at 1026 PM EST TUE NOV 29 2016
Convection continues to blossom and fill in across the TN valley.
Fortunately, most of the organized cells are having a hard time
maintaining their integrity as they make their way north. Eastern
Kentucky remains stable at the surface and the latest meso-
analysis has only meager MU CAPE values just to our south. Despite
the low level jet ramping up overnight, it is unlikely that storms
will be organized enough to take full advantage of this jet and
overcome the stable surface layer. As such, have downplayed the
severe threat for the rest of the overnight and have only
mentioned some strong wind gusts still possible. Freshened up the
hourly pops through tomorrow based on the latest higher resolution
model trends. This yielded slightly less QPF for the Bluegrass, and
perhaps a touch more across portions of the Cumberland Valley, as
some training of storms will be possible closer to dawn. Updates
have been sent.
UPDATE Issued at 722 PM EST TUE NOV 29 2016
Convection has commenced in earnest down in the deep south. Dew
points across eastern Kentucky are currently running from the low
to mid 40s across most locations. Thicker cirrus will advect in
from the southwest through this evening; however, some of the
cooler valleys have taken advantage of the drier low level air and
nearly calm winds. Temperatures have dropped into the lower 50s,
so have allowed for a few upper 40s as a possibility, before
thicker cloud cover moves in and allows for a rise later on. The
last few runs of the HRRR have held pops off until closer to 04
or 05z. Given the drier air in place, am inclined to agree with
the slower arrival and have reflected this in the pop timing.
Updates have been sent.
&&
.SHORT TERM...(This evening through Wednesday night)
Issued at 437 PM EST TUE NOV 29 2016
A strong upper level low is in place across MN this afternoon, with
deep longwave troughing across much of the central conus. A strong
ridge is also in place across the southern Gulf of Mexico. The
difference between these two systems is producing strong pressure
gradients, especially across the southern Mississippi and Ohio River
valleys. Meanwhile, a strong surface low pressure feature is in
place across Minnesota as well, in conjunction with the upper level
low. This surface low has two cold fronts protruding southeastward.
The first of these cold fronts is now east of the region, having
impacted us last night, however the secondary cold front is gaining
strength as it pushes eastward toward the Ohio River Valley
overnight. Strong southerly flow is in place, with winds expected to
continue increasing as the cold front nears.
Moisture will also be on the increase ahead of the front this
evening and through the overnight. Given the latest sounding
profiles, this increase in moisture and WAA is still strong support
for elevated instability just ahead of the front, with elevated
thunderstorms possible generally between 3 and 6z across our western
CWA. Some of the heavier rain showers could result in the mixing
down of strong winds aloft, so damaging winds cannot be ruled out.
Surface based instability will begin increasing after midnight as a
meso-low quickly pushes eastward ahead of the front and into the
region as well. This will result in higher winds transferring to the
surface, and a good potential for scattered thunderstorms across the
area. Latest forecasts soundings show highest winds transferring to
the surface between 6 and 12Z, so it won`t be hard for high to
damaging wind gusts to occur. The largest threat, as outlined by SPC
in their slight risk area, will be along I75 and points westward in
our CWA. However, this does not rule out the isolated potential for
damaging winds elsewhere either.
Also based on the sounding profiles, the storms will likely pass
over as a QLCS, in line form. Given this type of profile, with the
very strong winds, and impressive low level sheer, an isolated spin
up tornado cannot be ruled out along the front of the line.
The actual cold front will continue eastward across the CWA through
just after 18Z, before it exits to our east. Rain, chances for
thunderstorms, and potentially gusty winds will continue through the
day Wednesday, though the damaging wind threat and tornado threat
will diminish as a low level inversion sets up. Still the potential
that some gusty winds could make it to the surface in the heaviest
showers and thunderstorms. In better news, this system will bring
with it a good shot of Gulf moisture and soaking rains. Almost the
entire CWA is expected to see an inch of rain or more from tonight
through tomorrow evening, with some locations across the southwest
possibly topping 1.5 inches. This will hopefully help with
any ongoing drought concerns, as well as any ongoing wildfires.
Rain chances will finally taper off through tomorrow evening as the
cold front continues to exit east of the region and high pressure
starts to take hold. By this point the upper level low and the
surface low pressure system will be moving across the Great Lakes
region, with northerly flow on the back side makings its way into
the Ohio River Valley. This will result in much cooler overnight
temps compared to tonight, much closer to seasonal norms.
.LONG TERM...(Thursday through Tuesday)
Issued at 438 PM EST TUE NOV 29 2016
The period is expected to begin with an area of broad troughing
across much of the CONUS and southern Canada with ridges over the
Atlantic and Eastern Pacific. At the sfc, a slow pressure system is
expected to be tracking through Quebec and the Northeastern CONUS
with the trailing cold front moving off the eastern seaboard at that
time with sfc high pressure nosing into the area. A mid level low
over the Great Lakes with associated shortwave trough south into
the Lower OH Valley is also expected early in the period.
Thu through Friday, the closed low is expected to meander into
Eastern Canada while a shortwave initially over the Norther Rockies
moves south to the Four Corners region and closes off. The 12Z model
runs seem to be in better agreement in handling this with a slower
and generally less consolidate system. Height rises are expected
over the OH Valley especially on Friday with sfc high pressure
settling across the area.
Late Friday through Sunday, a series of northern stream shortwaves
are expected to move from the Rockies/Northern Plains east to the
Great Lakes and OH Valley with the strongest of these nearing the
Mid Valley and Lower OH Valley late Saturday night. This pattern
would lead to a sfc wave moving across the southern states with
inverted trough north into the area on Sunday with chances for
mainly light precipitation. At the same time, the closed low is
expected to dig further south into Northern Mexico from the Four
Corners and then track across Northern Mexico. During this period,
lowered pops compared to the Superblend for Saturday into Saturday
night as it was biased up by the 0Z ECMWF run and did not reflect
the model consensus with the upper air pattern/closed low with the
12Z runs and past few GFS runs.
High pressure is then expected to bring a lull in precip chances for
late Sunday or Sunday night into most of Monday. However, rain
chances should return with the potential for another wetter system
with more Gulf of Mexico moisture possibly getting involved as the
closed weakens, opens up, and interacts with a trough moving across
the Canadian Maritimes and Western CONUS. At the surface, a low
pressure system should develop over TX or the Western Gulf of Mexico
region and track toward the Lower OH Valley Monday into Tuesday.
As for sensible weather, plenty of moisture is expected to remain
near 850 mb and below to start the period with potential for
diurnally driven cu and or lingering stratocu. This and cold 850 mb
temperatures should lead to below normal highs Thu into Friday, but
diurnal ranges will be a bit limited. Clouds should thicken and
lower late Saturday night into Sunday with light preciptation
possible. Depending on how quickly the lower levels saturate a rain
and snow mix might be possible early on Sunday. However, the better
chance of preciptation with this system will hold off until during
the day on Sunday when the atmosphere will have moderated further
and precipitation should fall as rain. As already noted, Sunday
night and Monday should be mainly dry although there will be some
passing mid and high clouds from time to time. Monday night into
Tuesday rain chances will return with the surface low moving into
the Lower OH Valley region.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
ISSUED AT 722 PM EST TUE NOV 29 2016
An area of low pressure will track towards the area overnight into
Wednesday morning, bringing widespread rainfall and scattered
thunderstorms. Ceilings will gradually lower from southwest to
northeast through 06z, with precipitation breaking out west of
I-75 first. Have held onto VFR for all sites, with deteriorating
conditions expected between 06 and 12z. Ceilings and visibilities
will fall to MVFR, and even IFR at times, within heavier showers
or thunderstorms. South to southeast winds will average at 5 to 10
kts; however a strong low level jet will allow for ample wind
shear from approximately 05z through 14z. Precipitation will
diminish from west to east Wednesday afternoon, with improving
conditions towards the end of the period. South winds will also
shift to the southwest during the day on Wednesday, and could
become gusty at times in the afternoon.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...GEOGERIAN
SHORT TERM...JMW
LONG TERM...JP
AVIATION...GEOGERIAN
Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
851 PM CST Tue Nov 29 2016
.DISCUSSION...See updated information for land areas below.
&&
.UPDATE...Upper air map analysis this evening shows a large and vigorous,
positive tilt upper level storm system over the nation`s heartland.
East of the long-wave trof an active high level flow aloft is
positioned from the western Gulf to the east coast. A complex surface
pressure pattern exists with a quasi-stationary frontal zone draped
from the Appalachians to the TX coast. West of this boundary, another
frontal boundary was advancing southeast out of the southern plains.
Despite the presence of an anomalously deep moist profile along the
Gulf coast (precipitable water values 1.3 to 1.5 inches ranging from
160 to 190% of normal) southeast of these boundaries, current
soundings indicate a rather pronounced warm nose in the mid levels
between 700 and 750MB. This has been acting as a cap and keeping
radar activity minimal this evening. Appears showers and storms will
stay isolated to low end scattered in coverage through the remainder
of the evening along and west of I-65. Moving into the pre-dawn hours
Wednesday AM, a squall line of storms is forecast to organize and
move east over the Lower Mississippi River Valley.
The greatest severe weather threat appears to remain to our
northwest across central and northern Mississippi where an enhanced
to moderate risk zone is outlined by the storm prediction center.
This is where the best dynamics and instability will reside for
organized and more widespread severe storms. The latest high
resolution HRRR solutions bring the leading edge of the convective
line into interior southeast MS shortly before daybreak Wednesday.
Projecting forward in time, forecasters maintain a consistent message
on timing the line across the I-65 corridor between 9 AM and 1 PM
before exiting east of the area by 3 PM. The primary risk of severe
thunderstorms will be across southeast Mississippi and west of I-65
in southwest Alabama Wednesday morning with the greatest threat being
damaging straight-line winds. /10
&&
.PREV DISCUSSION... /issued 558 PM CST Tue Nov 29 2016/
DISCUSSION...See updated information for marine areas and aviation
discussion below.
MARINE...Even though a moderate to strong onshore flow exists,
there have been reports of fog, which is of advective type, over
Mobile Bay. Considering reports and port visibilities down to near 3
statute miles, have made an update to Mobile Bay portion of the marine
zones to mention fog tonight. Small craft caution wording for area
bays and sounds will continue, while advisories remain in place over
the open Gulf waters. /10
AVIATION...
00Z issuance...A steady stream of clouds, of multiple bases,
continues to move from the Texas coast, east northeast into the
southeast US atop a stationary frontal zone. MVFR bases this evening
over the central Gulf coast, lowers to IFR levels. VSBY lowers to
MVFR categories, potentially IFR at times overnight along with
passage of isolated to scattered shra. Timing of next convective band
over the terminals forecast by and shortly after daybreak Wed with
strong convective wind gusts and vsby lowering to LIFR categories in
+TSRA. South winds 9 to 14 knots with occasional higher gusts
between 20 and 25 knots overnight. /10
PREV DISCUSSION... /issued 432 PM CST Tue Nov 29 2016/
NEAR TERM /Now Through Wednesday/...The upstream cold front remains
stalled across the central plains in the deep layer southwest flow
pattern due to a strongly positive tilt upper trough from the
northern plains into the southwestern states. This front will
finally get a kick start tonight as an upper shortwave rotating into
the southern plains ejects eastward. As the forcing with the
shortwave interacts with the front and a moist and unstable
environment over the Lower Mississippi River Valley, expect showers
and thunderstorms to break out this afternoon and evening and
congeal into a squall line late this evening which will move east
overnight. Across our area, gusty southerly winds will continue
tonight which will maintain high surf and dangerous rip currents at
the beaches.
We expect isolated to scattered showers and thunderstorms to
increase in coverage especially across western zones this evening.
The greatest severe weather threat will remain to our northwest
across central and northern Mississippi where an Enhanced Risk zone
is outlined. This is where the best dynamics and instability will
reside. The line of showers and thunderstorms will enter southeast
Mississippi between 5-9 AM and to the I-65 corridor between 9 AM and
1 PM before exiting east of the area by 3 PM. The best jet dynamics
will be pulling away to the north through this time frame and
instability levels will again be rather weak. Therefore the primary
risk of severe thunderstorms will be across southeast Mississippi
and west of I-65 in southwest Alabama Wednesday morning with the
greatest threat being damaging straightline winds.
A cooler and drier airmass will follow in the wake of the front
through the day on Wednesday with gradual clearing from northwest to
southeast by late afternoon. Highs will be in the mid and upper 60s
across northwest areas to mid 70s across the southeast. 13/JC
SHORT TERM /Wednesday night Through Friday night/...Surface high
pressure will move west to east across the region throughout the
short term period. Mostly clear skies and no rain is expected.
Nighttime lows in the 30s inland and lower 40s near the coast through
the period. Highs in the low to mid 60s each day. 12/DS
LONG TERM /Saturday Through Tuesday/...An unsettled weather pattern
returns to the area over the weekend and into the early part of next
week. Widespread rains become quite possible as an overrunning event
sets up over the weekend. Rainfall totals during the long term period
could approach 2 to 3 inches in some areas, but severe convective weather
is not anticipated. Daytime highs early in the period ranging from
upper 50s inland to mid 60s coast...slowly moderating to upper 60s
inland and lower 70s coastal by Tuesday. Nighttime lows ranging from
low/mid 40s interior to low/mid 50s coastal through the period. 12/DS
MARINE...Winds and seas will increase again tonight into Wednesday
as a cold front approaches from the west. The cold front moves
through the marine area Wednesday afternoon with a moderate to
strong northerly flow in its wake with seas up to near 9 feet well
offshore. A Small Craft Advisory is in effect for the Gulf waters
until 1 pm Wednesday. Scattered to numerous showers and thunderstorms
can be expected late tonight into Wednesday with some strong to
possibly severe with locally higher seas expected near storms. 13/JC
&&
.MOB WATCHES/WARNINGS/ADVISORIES...
AL...High Rip Current Risk through late Wednesday night for ALZ265-
266.
High Surf Advisory until 1 PM CST Wednesday for ALZ265-266.
FL...High Rip Current Risk through late Wednesday night for FLZ202-
204-206.
High Surf Advisory until 1 PM CST Wednesday for FLZ202-204-206.
MS...None.
GM...Small Craft Advisory until 6 PM CST Wednesday for GMZ650-655-670-
675.
&&
$$
This product is also available on the web at:
http://weather.gov/mob
Area Forecast Discussion...UPDATED
National Weather Service Marquette MI
957 PM EST Tue Nov 29 2016
.UPDATE...
Issued at 956 PM EST TUE NOV 29 2016
Forecast for rest of tonight and again later Wed aftn into Wed
evening still on track. Did make a few changes to Wed morning
forecast across central Upper Michigan. Any light rain/snow this
evening should continue to fade away/end as weak shortwave lifts to
north of Lk Superior. Attn for Wed morning is on shortwave currently
producing light rain over southern MN. One of many shortwaves
wrapping around large trough aloft centered over MN.
As that southern MN wave lifts to the northeast late tonight,
associated sfc trough heads across WI and becomes more closed off as
a sfc low while lifting northward across Lk Michigan on Wed morning.
Forcing features both aloft and at the sfc and perhaps also on
western fringe of forcing that is producing the light rain showers
lifting across lower MI this evening should all combine to generate
batch of light rain showers developing over central cwa on Wed
morning, possibly mixed with snow over higher terrain of west and
north central cwa based on wetbulb zero heights 500-1000 ft agl. 18z
NAM first showed this idea and was joined recently by the HRRR and
RAP and now the 00z NAM. Any snow should be minimal with warm ground
temps and light precip intensity. Since interior east will have shot
at getting cold tonight with no clouds overhead attm, if the precip
that moves in toward 12z/7 am ET starts out as rain, it is feasible
that there could be a non-zero risk of light icing first couple
hours. Current road temps there per MDOT are in the lower 30s. This
would be the one area that the light precip coming in around daybreak
could have an impact. Will pass this concern along to mid shift.
As Wed wears on, best chances of rain/snow should set up over
western cwa with cold air advection occurring on the west side of
sfc low that will be lifting to somewhere vcnty of Munising by early
Wed aftn. Blended the changes made for the morning into the forecast
for the aftn which still looked fine attm.
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 404 PM EST TUE NOV 29 2016
WV imagery and RAP analysis indicated a closed mid/upper level low
over cntrl MN. At the surface, an elongated trough or occluded front
extended from cntrl MN through nrn Lake Superior. An area of mixed
rain and snow over cntrl Upper Michigan supported by 850-700mb fgen
was gradually diminishing as the stronger forcing lifts to the
northeast.
Tonight, Models suggest that 850-500 drying will spread across the
area. With levels also drying out, expect the remaining light pcpn
to end early this evening leaving mostly cloudy skies. continued
weak CAA will drop min readings into the upper 20s inland west to
the mid and upper 30s east.
Wednesday, As the mid level low wobbles into WI the low level trough
is expected to develop over srn or southeastern Lake Superior. 850
mb temps around -2C will provide enough instability (lake temps
around 7C) with the deeper moisture and 700 mb temps to around -11c
for an increase in lake enhanced pcpn into the west half during the
afternoon as winds become nrly. However, there is uncertainty with
how the mesoscale features will evolve and affect pcpn intensity.
Wet-bulb zero heights support mainly snow over the inland west but
a mix of rain and snow closer to the lakes.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 249 PM EST TUE NOV 29 2016
With little potential for significant conditions through the rest of
the week and considerable uncertainty next week, did not make
significant changes to blended initialization. Spent majority of
shift time performing AWIPS fixes.
Without being too specific (see forecast for specific expectations),
the low currently W of the area will move E of the CWA by Wed night
and will meander over Quebec through Fri. The airmass will be cool
enough for some lake enhancement in the N-NW winds behind the
system, so expect off and on precip into Sat, with the best coverage
closer to Lake Superior. Ptype will depend largely on near-SFC
temps, so the best chances for snow will be at night and also over
the higher terrain of the W. Due to only expecting light precip and
with relatively warm SFC temps (at least during the day), only light
snowfall amounts are expected through Sat.
Still looking at a significant pattern change possible 10-14 days
out, with more active weather possible starting later next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 650 PM EST TUE NOV 29 2016
Low level moisture wrapping into Upper Michigan from the sw ahead of
low pressure over MN will maintain mainly MVFR cigs through much of
tonight at IWD and CMX. At SAW expect marginal MVFR cigs to possibly
scatter out late tonight leading to possible light fog development
toward sunrise on Wed. On Wed, conditions will begin deteriorate at
IWD and CMX as rain and snow increases in the aftn and evening as the
low crosses Upper Michigan and drags a sfc trough over Lk Superior
and northern Upper Michigan. Could see vsby down to IFR at times,
especially on Wed evening as ptype becomes mainly snow and coverage
and intensity ramps up. At SAW on Wed, expect cigs to lower to IFR
later morning into the aftn and evening as winds turn to the north
off Lk Superior. Any rain/snow showers at SAW should be light and
isolated into Wed evening.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 404 PM EST TUE NOV 29 2016
The low pressure system will linger over the western Great Lakes
into Wednesday. However the pressure gradient is not expected to be
as tight and should allow winds to diminish below 25kt by tonight.
Northerly winds to near 30 knots may develop Thursday as the slow
moving trough moves to the east of Lake Superior into Quebec. High
pressure will then build into the area into Saturday with winds
below 20 knots.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
UPDATE...JLA
SHORT TERM...JLB
LONG TERM...Titus
AVIATION...JLA
MARINE...JLB
Area Forecast Discussion
National Weather Service Paducah KY
932 PM CST Tue Nov 29 2016
.UPDATE...
Issued at 932 PM CST Tue Nov 29 2016
Only minor changes made to reduce areal coverage of thunderstorms
in the far southeast section of the West Kentucky Pennyrile region
during the late evening and overnight and to shift higher
measurable PoP coverage further to the east.
Severe threat is quite limited within the WFO PAH CWA at this
time, in line with SPC`s shift eastward with the Slight risk from
the local CWA.
Otherwise, no significant changes to tonight`s forecast.
UPDATE Issued at 552 PM CST Tue Nov 29 2016
The AVIATION section has been updated for the 00Z TAF issuance.
&&
.SHORT TERM...(Tonight through Thursday night)
Issued at 304 PM CST Tue Nov 29 2016
After a brief respite from the rain today, a cold front, which is
just to our west, will cross the region tonight. Ahead of the front,
weak ripples of energy in the southwest flow aloft will tap into
enough moisture to produce overrunning precipitation mainly over the
southeastern sections of the CWA, mainly west KY up into possibly
southwest IN. While some sprinkles could occur prior to 00Z tonight,
most of the heavier QPF will likely occur after 00Z with the
heaviest rain falling over the southern Pennyrile region.
Models are not in agreement with QPF amounts with the HRRR and GFS
indicating fairly low QPF and the NAM indicating a pretty good
amount of rain from the lakes region eastward, since it is
indicating a sfc low developing along the front to our south that
moves northeast into central KY by 09Z Wed. Definitely think the
best chances for heavier QPF will be from Calloway County KY up
through Muhlenberg County KY and areas south and east of there with
lighter amounts northwestward. In fact, if the NAM is correct parts
of southern Christian county and most of Todd county could see
upwards of a half inch or more.
Instability is hard to come by with this event but the best chance
for thunder will be over parts of west KY, namely from the lakes
region eastward (southern Pennyrile region). Better chances for
severe will be to our east and south, as outlined in the latest SPC
Day 1 outlook, but cannot rule out a strong storm in the far
southeastern areas, especially this evening. Will have to keep a
close eye on extreme southern portions of the Pennyrile region of
west KY. Convection is already ongoing in southern AR and MS heading
north northeast.
In the wake of this system, we will have a pretty tight pressure
gradient in place so breezy conditions will result on Wed. In
addition, clouds will be returning for parts of the area as main
upper trough moves overhead. However, sfc high pressure will
eventually build into the area which will mean dry but cooler
weather will be with us from Wednesday through the end of the
period.
.LONG TERM...(Friday through Tuesday)
Issued at 304 PM CST Tue Nov 29 2016
Most interesting part of the long term will come Saturday night.
Confidence is lagging somewhat, but it looks like some locations
may experience the first very light wintry type precip of the
season. However, no real impacts are anticipated at this time.
Chilly high pressure will be settling in over the region to start
the period on Friday into Saturday, with dry conditions and temps
down close to normal for this time of year. The high will scoot
off to the east Saturday night/Sunday as a weak short wave and
associated trof of low pressure at the surface push east toward
the mid MS River/lower OH Valley regions.
There could be enough isentropic lift generated to produce an
area of light precip later Saturday night into Sunday morning.
While only light rain is expected over far southern portions of
the region (closer to the AR/TN borders), temperatures in the
lower to mid 30s over the remainder of the region could result in
some very light snow, or a rain/snow mix, if the light precip
does not evaporate before reaching the ground. Nonetheless, ground
temps will bed relatively warm, and would mitigate any impacts.
So, some may wake Sunday AM to witness a few flakes of snow, but
that should be the extend of it unless a stronger wave manages to
form as we get closer to the weekend.
After a brief break in precip chances Sunday night/Monday, a
stronger, southern branch system may form toward the end of the
long term over the Southern Plains and then eject northeast word
the region later Monday afternoon or Monday night. ECMWF is much
more potent than the operational GFS with this system, but either
way, conditions will have warmed enough for an all rain event.
&&
.AVIATION...
Issued at 552 PM CST Tue Nov 29 2016
A surface trough lurking just west of the region will eventually
push eastward through the TAF sites late tonight. Initial
southerly winds will veer to the southwest and then west northwest
wind with the frontal passage. There is some uncertainty in the
wind forecast due to the possibility of a deeper surface low
riding northeast from west TN into central KY later tonight. This
seems to be a long shot at this time, so will stick with the more
traditional cold frontal wind forecast tonight.
There could be a few sprinkles over KOWB this evening, but any
significant precipitation is likely to remain well south of the
TAF sites and possibly even Ft Campbell.
As a stacked low pressure center pushes east to our north
Wednesday, surface winds should back to west southwest and
increase with gusts aob 20kts. An area of stratocu at 4-6kt is
likely to spread southeast through the region later in the
afternoon. A brief ceiling condition cannot be ruled out.
&&
.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...None.
IN...None.
KY...None.
&&
$$
UPDATE...Smith
SHORT TERM...GM
LONG TERM...CW
AVIATION...DRS
Area Forecast Discussion
National Weather Service Raleigh NC
942 PM EST Tue Nov 29 2016
.SYNOPSIS...A cold front will cross the area late Wednesday through
early Thursday. Behind the front, high pressure will build into the
region over the remainder of the week.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
As of 942 PM Tuesday...
Central NC is currently in a forcing lull as we wait for the next
shortwave trough(currently over the Southern Plains)to rotate newd
through the base of the synoptic upper trough that will move slowly
eastward into Central US. As such, with weak WAA in the continued
deep swly flow the primary forcing mechanism overnight, rain chances
will be pretty limited, with only isolated showers expected.
Probably the biggest question overnight is whether we will see areas
of dense fog develop across the western piedmont as is indicated by
some of the NCAR and HRRR guidance. While the moisture profile is
supportive, it appears that there should be a sufficient pressure
gradient to keep sustained winds at least in the 5 to 10 kt range
which should mitigate the potential for widespread fog.
Mild overnight lows in the 60s.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
As of 300 PM Tuesday...
A series of shortwave perturbations will help amplify the longwave
trough over the Midwest and enhance the line of pre-frontal
convection over western NC on Wednesday. Given the slow progression
of the convection as the parent upper low re-develops over the
eastern Great Lakes/southeast Canada, Wednesday could remain dry for
much of central NC. Strong southerly flow will continue to usher
warm moist air into the area (highs in the low to mid 70s), however
the persistent mid-level dry air will remain in place until the
convection moves in. The majority of the rain is expected to occur
after 7 PM and will be quick hitting, moving from the NW (Triad) to
the SE (NC coast) by early Thursday morning. Rainfall totals will
likely be highest in the NW and lowest in the southeast ranging from
quarter of an inch to an inch. The cold front will also progress
eastward through Central NC overnight. As a result of the current
fropa timing, lows should bottom out in the mid 40s to upper 50s
given that the winds will remain in the 5-10 mph range. The low-mid
level flow will be rather strong ahead of the front and could result
in fairly strong wind gusts, however instability, even during peak
heating, is low and decreases prior to the arrival of the convective
line. Central NC is in a marginal risk for Wednesday, however if
thunderstorms are able to become strong/severe, the main threat
would be isolated damaging wind, though the confidence is low at
this time.
&&
.LONG TERM /THURSDAY THROUGH TUESDAY/...
As of 315 PM Tuesday...
Expect a return to more seasonable temperatures behind the cold
front, though highs Thursday may still be in the mid 60s across the
southeast, as surface high pressure builds into and over the region.
Highs will be mainly in the low to mid 50s through the weekend and
lows in the low to mid 30s should prevail into early next week.
Though westerly winds may remain a bit breezy on Thursday, the
pressure gradient should slacken as the high builds in from the
west. The result will be a trend toward clear skies and light
winds through Friday Night.
The big forecast problem continues to be how the next weather system
evolves. The models are coming into slightly better agreement,
trending toward each other. Generally, an upper level low cuts off
over the southwest U.S on Saturday. It gets absorbed into the next
trough as it amplifies over the Rockies. The resultant shortwave
energy will help precip develop over the Midwest as it impinges on
the upper level ridge. Though the amplitude, speed, and timing of
this system are still highly uncertain, expect precipitation chances
to increase Sunday into early next week, though for now it appears
the surface high may hold over the region through the weekend.
&&
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
As of 740 PM Tuesday...
24 Hour TAF Period: A moist southerly low level flow will continue
tonight into Wednesday in advance of a cold front. Patchy MVFR cigs
this evening will fill in and lower tonight with low end MVFR/IFR
cigs expected by early Wednesday morning areawide, with possibly
some LIFR cigs and reduced visbys around daybreak. Cigs are expected
to slowly lift on Wednesday, with winds increasing out of the
south/southwest. By mid Wednesday afternoon expect generally VFR
conditions at KRDU/KFAY/KRWI with wind gusts of up to 30 to 35 mph
possible. Further west, a band of showers associated with the
approaching cold front will move into KINT/KGSO on Wednesday
afternoon, with winds gusts of up to 30 to 35 mph as well and cigs
possibly lingering in the high end MVFR range or low end VFR.
Outlook: The cold front will approach the area late Wednesday
triggering an additional band of convection during the late
afternoon and evening with showers and perhaps a thunderstorm
resulting in some restrictions. High pressure with fair weather is
expected for thursday into Saturday. A storm system will approach
the region for Sunday with a period of adverse aviation conditions.
&&
.CLIMATE...
Record high minimums for 11/29
RDU 62 1934
FAY 66 1990
GSO 57 1957
Record highs for 11/30
RDU 77 2006
FAY 80 1927
GSO 74 1991
Record high minimums for 11/30
RDU 62 1934
FAY 62 2001
GSO 62 1934
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...KDS
NEAR TERM...CBL
SHORT TERM...KCP
LONG TERM...KCP
AVIATION...BSD/BLAES
CLIMATE...RAH
Area Forecast Discussion
National Weather Service Birmingham AL
111 AM CST Wed Nov 30 2016
.UPDATE...
MESOSCALE UPDATE.
&&
.SHORT TERM...
Today and Tonight.
The 06Z BMX sounding indicates an unusually unstable air mass for
this time of day/year with SBCAPE of 1400 J/kg and MLCAPE of 730
J/kg. This combined with 0-1 shear of 33 kts, 0-6 shear of 64 kts,
and effective SRH of 300 m2/s2 will maintain a threat of tornadoes
throughout tonight and during the day on Wednesday as well.
Lifting of the dry layer aloft will also result in release of
potential instability and continue to steepen the mid-level lapse
rates. The strong shear and lack of strong upper- level forcing
has kept a true squall line from forming, with the convective line
extending from Louisiana to north AL remaining cellular in nature.
The HRRR indicates that this will continue. Both discrete
supercells ahead of the line and embedded supercells within the
line will continue to pose a threat for tornadoes. The tornado
watch was recently expanded to include Bibb, Jefferson, and Blount
counties, with a good chance of an additional watch beyond the
current 5AM expiration time including the areas further southeast. The
severe threat will continue to push southeastward, reaching the
I-20 corridor between about 3 and 6 AM and the I-85 corridor
between 8 AM and noon, exiting the farthest southeast counties
between 1 and 3 PM. Drier and cooler air will move in behind the
front this afternoon and evening.
32/Davis
.LONG TERM...
Thursday through Tuesday.
With this storm system to our east on Thursday, we will be back into
the high pressure realm for a couple of days, but no worries, the
dry spell will only last into the first half of the weekend. By
Friday afternoon a disturbance will begin to slide northward out of
the Gulf of Mexico and move into Louisiana by Saturday morning. This
disturbance will slide along and ahead of a cold front, working into
the western portion of Central Alabama by Saturday afternoon and
overspread the area during the day Sunday. Will have to monitor the
northward trends of the 60+ dewpoints as we get into Sunday
afternoon and Sunday evening. The 00Z GFS is indicating some mid 60s
in the southeast late Sunday afternoon, while the 12Z Euro keeps
dewpoints below 60 the entire time. However the 00Z Euro now brings
60+ dewpoints into the entire forecast area by Sunday evening, therefore
bringing a risk of severe weather into the area Sunday through
Monday evening. The dilemma here is the overall pattern. While we
remain in a very progressive pattern the GFS hangs the mid level
low back into the Four Corners area while the Euro now keeps the
trough moving and brings a potentially strong vort max into the
area by Monday morning. Will re-evaluate this tomorrow night and
see what if any additional changes need to be made.
We will remain fairly wet for the rest of the forecast as well as a
second trough and showers and storms move into the area Wednesday
night into Thursday. Again some differences in the overall timing
and strength will preclude any mention of severe with this system as
well, but there could be a small window here as well.
16
&&
.AVIATION...
06Z TAF Discussion.
Biggest update again for this TAF issuance is slowing down the
TSRA timing across Central AL. The warm front has moved through
the area already, giving us some gusty south winds. Some spotty
showers are beginning to develop across the area, but coverage is
currently limited. Have left mention of VCSH beginning in a few
hours (07z-09z) to account for this, though these showers could
be very light. The main line of storms has slowed somewhat. Latest
models show the line entering our northwestern counties around 9z,
but not reaching BHM area until 12z before moving east-southeast
through the morning hours. Along this line, TSRA conditions can be
expected, with lowered visibilities during periods of heavy rain.
Northwesterly flow follows behind the line tomorrow with VFR
conditions.
25/Owen
&&
.FIRE WEATHER...
Showers and storms, some severe, will remain in the area through
this afternoon. Drier air should move into the area on Thursday and
Friday but moisture returns Saturday with another round of showers
expected Sunday through Tuesday. A third storm system will work into
the area by next Wednesday. So an overall wet pattern will be in
place for the next next 7 to 10 days.
16
&&
.PRELIMINARY POINT TEMPS/POPS...
Gadsden 68 35 56 31 56 / 90 10 10 0 0
Anniston 69 38 58 33 58 / 100 10 10 0 0
Birmingham 67 39 58 34 58 / 80 0 10 0 0
Tuscaloosa 67 37 59 33 60 / 70 0 10 0 0
Calera 69 38 58 34 59 / 100 10 10 0 0
Auburn 70 42 60 37 59 / 100 10 10 0 0
Montgomery 73 40 62 35 62 / 100 10 10 0 0
Troy 72 41 62 36 61 / 100 10 10 0 0
&&
.BMX WATCHES/WARNINGS/ADVISORIES/...
None.
&&
$$
Area Forecast Discussion
National Weather Service Houston/Galveston TX
1122 PM CST Tue Nov 29 2016
.AVIATION...
The boundary near the coast has moved much more slowly than
expected this evening, resulting in much more significant impacts
from fog and low ceilings than anticipated as far inland as
Hobby. However, the boundary appears to have finally moved off the
coast, and at least modest improvements are being seen across the
area, even GLS. Though GLS still needs some cleanup for vsby at
the outset of the TAF, most sites will be VFR with a focus on
trying to hit trends in wind as a reinforcing front sweeps through
the area this morning, with winds expected to settle by the end of
the period.
Luchs
&&
.PREV DISCUSSION... /ISSUED 907 PM CST Tue Nov 29 2016/
DISCUSSION...
Based on radar fine lines, the cold front was located from near
KJAS in east TX to KLVJ (Pearland) and then SW to KBYY (Bay City).
The front appears to be moving fairly slowly, maybe 5 mph. Latest
HRRR model trends have the front pushing off the coast after
06z/midnight and then accelerating south. Radar still shows a few
lines of showers/storms in the Gulf but remain rather weak due to
capping aloft evident by ACARS soundings as well as the 00Z CRP
sounding. CRP sounding had temps of 10C at 700mb, 20C at 850mb.
Surface obs also showed a few isolate areas of fog developing
south of the front. Mainly visibility has dropped to around 3 to
5 miles along the coast and just off shore. The front should erode
the fog the next couple of hours. We are certainly not expecting
dense fog to quickly form like last night.
Main changes to the forecast were to just update for on going
trends with the front pushing south. Minimum temps may not be
quite as cool along the coast since it will take some time for
cold air advection to take place.
As for this coming weekend, I think the previous discussion covers
the potential rain event. Despite some model differences, I`ll
sum up by saying "It gonna rain".
Overpeck
PREV DISCUSSION... /ISSUED 535 PM CST Tue Nov 29 2016/
AVIATION...
For most sites, dry air on northwest flow should keep fog from
being an issue tonight. However, with a boundary stalled just
inland of the Gulf shore, this seems unlikely at GLS, which
should see some fog develop before gusty northwest winds on a cold
front blast dry air in. Went with MVFR conditions now, on chance
that stalled boundary drifts southward this evening, but potential
for IFR definitely exists and may be cause for later amendments.
Other challenge will be how and when winds get gusty as cold front
works through. In collaboration with the CWSU, agree on bringing
in gustier winds a little after winds just off the surface
increase. Along with that, the narrow band of clouds near the
coast should also depart the area.
PREV DISCUSSION... /ISSUED 408 PM CST Tue Nov 29 2016/
DISCUSSION...
The frontal boundary responsible for thunderstorms across parts
of the Brazos Valley and Piney Woods earlier this morning as it
lifted north is now sagging south across the region this
afternoon. Surface analysis shows this boundary snaked from Edna
to Katy to Dayton, with satellite imagery showing enhanced cumulus
developing along the boundary. Despite this, convection this
afternoon has been largely limited as warm air advection at 850
and 700 MB has resulted in a strengthening cap across the Houston
metro. Low level warm air advection today has also resulted in a
few locations reaching or setting record high temperatures, with
Houston Intercontinental having reached at least 84 degrees as of
4 PM (which would exceed the record of 83 set in 2006).
Cannot rule out a few showers developing underneath this cap as
the boundary slowly sags towards the coast this afternoon, with
scattered showers and thunderstorms blossoming over the coastal
waters and extreme southeastern counties this evening as a
secondary cold front across North and Central Texas sweeps off the
coast this evening and tonight. May see a few of the storms across
the coastal waters become strong to marginally severe, but this
activity will continue to move into the northern Gulf and away
from the Upper Texas coast with the associated front. Until the
cold front moves off the coast tonight and ushers in drier air,
may see some patchy fog across the bays and nearshore waters with
warm, moist air pooled right along the coast. Otherwise, expect
overnight lows in the low 40s to mid 50s.
Surface high pressure building into the region in the wake of
tonight`s front will result in dry, cooler weather for the region
on Wednesday and Thursday. Elevated north winds (15-20 MPH) and
relative humidity values falling to near 25 percent during the
afternoon tomorrow will result in elevated fire weather conditions
for most inland areas tomorrow afternoon, but decreasing winds on
Thursday will help limit overall fire weather concerns. Expect
highs Wednesday and Thursday to be in the 60s with lows ranging
from the upper 30s across the extreme northern counties to mid 50s
along the coast.
Attention then turns to the upcoming weekend as energy from an
upper trough approaching from the west cuts off over northern
Mexico. Surface high pressure shifting into the southeastern US on
Friday will allow moisture to begin surging into the region, aided
by the development of a coastal trough along the Middle Texas
coast. Southwest flow aloft combined with enhanced low level
convergence from the coastal trough will result in periods of
showers and thunderstorms across Southeast Texas in the Saturday
through Monday timeframe. With precipitable water values climbing
to near 1.7 inches along the coast, have increasing concerns for
heavy rain to impact parts of the Upper Texas coast. Medium range
guidance has come into better agreement on the overall upper
pattern evolution, but still offers different timing on when the
upper low will lift across Texas and placements on the coastal
trough that develops (which would affect which areas see the
heaviest rain). Regardless, this weekend looks cool, wet, and one
to watch for heavy rain impacting parts of the Upper Texas coast.
Huffman
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 46 65 40 66 45 / 0 0 0 0 0
Houston (IAH) 54 67 42 67 46 / 10 0 0 0 0
Galveston (GLS) 61 68 54 65 58 / 20 0 0 0 0
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION from 6 AM CST Wednesday
through Wednesday morning for the following zones: Coastal
waters from Freeport to the Matagorda Ship Channel out 20
NM...Coastal waters from High Island to Freeport out 20
NM...Matagorda Bay.
Small Craft Advisory from 6 AM to noon CST Wednesday for the
following zones: Waters from Freeport to the Matagorda Ship
Channel from 20 to 60 NM...Waters from High Island to
Freeport from 20 to 60 NM.
&&
$$
Discussion...39
Aviation/Marine...25
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
359 AM EST Wed Nov 30 2016
.SYNOPSIS...
Low pressure over the upper Great Lakes will track into eastern
Canada tonight. An associated cold front night will push through
the Mid Atlantic late tonight. High pressure will return to the
region Friday and Saturday. Low pressure will track to the west of the
region Sunday night. High pressure returns Monday.
&&
.NEAR TERM /TODAY/...
As of 3 am, persistent vertically stacked/occluded low with 997mb
surface low centered over the Twin Cities of MN. Longwave trough
axis is ejecting onto the southern Great Plains. Weak surface flow
and moisture from rain yesterday caused areas of dense radiation fog
to develop. Dense Fog Advisory is in effect until 7 am for most
of the CWA (Srn MD and Potomac Highlands are exception). Thick
clouds are spreading NE across the and have reached the Blue
Ridge. There are fewer 1/4SM reports west of the Blue Ridge now,
but will need to keep the advisory at least for now. NErn sections
of the CWA stand the best chance to have an extension to the fog
advisory.
Showers and isolated thunderstorms area spreading north from SWrn VA.
RAP has some MUCAPE where current lightning is, but not in the SWrn
section of the LWX CWA, so only rain/showers will continue to be
forecast for the morning.
Instability is expected to develop SE of the main slug of rainfall
by midday with negative LI`s at 18Z according to the 00Z GFS. A
marginal risk is in effect across the area with the strong low level
jet potentially mixing down with the strongest activity. Furthermore,
discrete super cells are possible east of I-95 (most likely for
southern MD). Hence a 2 percent tornado risk. Expect locally heavy
rain with QPF generally half inch with locally one or more inches.
&&
.SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/...
The longwave trough axis currently over the southern Great Plains
will reach the mid-Atlantic by sunrise Thursday. An associated cold
front will cross the area tonight, clearing out rain.
Gusty west wind up to 30 mph both Thursday and Friday with little
upslope snow. Maxima mid to upper 50s in dry air advection Thursday
and five or so degrees less Friday after continued cold air
advection..
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
High pressure will reside over the east coast Saturday. With the
upper level flow in a zonal pattern temperatures will be right
around climo norms for the beginning of Dec - near 50. Radiational
cooling will allow temps to fall to around or slightly below the
freezing Saturday night.
Last night the models had some differences regarding the Sunday
forecast but these seem in better line today. An open short wave
is expected to track to our NW while high pressure moves into the
Atlantic. There`ll be a chance of rain during the afternoon in the
central Shenandoah Valley..with the moisture tracking north Sunday
night. We are presently forecasting mixed precipitation west of
I-95...but confidence is low with regard to the frozen precip.
The high moving away means that cold air will not be held to our
north which is essential..especially in a marginal situation like
this. Lows expected to be in the lower to mid 30s.
High pressure returns for Monday. Highs near 50. Monday night lows
in the lower 30s.
&&
.AVIATION /07Z WEDNESDAY THROUGH SUNDAY/...
Areas of dense fog with LIFR cigs across the central Mid-Atlantic
early this morning will slowly lift/diminish as clouds and rain
spread northeast across the area through sunrise. However, IFR conds
expected to prevail into the afternoon as potentially gusty showers
cross the area continues. Isolated thunder risk this afternoon and
evening, particularly southeast of DC. South winds increase by midday
with gusts into the 20 kt range.
Cold front crosses the area after midnight tonight with a shift to
west winds. Gusts in 25 kt range Friday and Saturday with VFR conds.
VFR conditions Saturday into the at least the first part of
Sunday. Clouds are expected to increase Sunday night with a chance
for precipitation.
&&
.MARINE...
Just like yesterday, south winds increase today as rain overspreads
the area through the morning. Gusty showers and isolated
thunderstorms may trigger special marine warnings, particularly in
the afternoon.
A cold front crosses the area tonight with a shift to west winds
after midnight. West winds mix down through Thursday with gusts
around 25 knots across the waters. SCA through Thursday for now and
is likely again both Friday and Saturday.
SCA level wind gusts possible Saturday. No problems foreseen
Sunday.
&&
.COASTAL FLOOD...
Southerly flow continues on the water today ahead of a cold front
that will cross late tonight. Winds will generally be 15 knots
gusting 20 knots which would not cause much of a surge and the
forecast is for water levels to remain a few inches below minor
flood thresholds for the preferred high tide this afternoon and
evening. However, stronger winds may mix down as showers and isolated
thunderstorms cross this afternoon. A stronger surge could occur with
this activity, perhaps raising levels to minor coastal flood levels.
New moon is today.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Dense Fog Advisory until 7 AM EST this morning for DCZ001.
MD...Dense Fog Advisory until 7 AM EST this morning for MDZ003>006-
011-013-014-016-502>508.
VA...Dense Fog Advisory until 7 AM EST this morning for VAZ025>031-
036>040-050>057-501>508.
WV...Dense Fog Advisory until 7 AM EST this morning for WVZ050>053-
055-502-504>506.
MARINE...Small Craft Advisory until 6 PM EST Thursday for ANZ530>532-
535-538>540.
Small Craft Advisory until 6 PM EST Thursday for ANZ533-534-
536-537-541>543.
&&
$$
PRODUCTS...BAJ/WOODY!
Area Forecast Discussion
National Weather Service Mobile AL
1058 PM CST Tue Nov 29 2016
.DISCUSSION...Updated for latest aviation discussion below.
&&
.AVIATION...
06Z issuance...A steady stream of clouds, of multiple bases,
continues to move from the Texas coast, east northeast into the
southeast US atop a stationary frontal zone. IFR to MVFR cig bases
forecast with VSBY generally at mvfr categories. isolated to
scattered shra lifting northward overnight. Timing of next
convective band over the terminals forecast after daybreak Wed with
strong convective wind gusts and vsby lowering to LIFR categories in
+TSRA. South winds 9 to 14 knots with occasional higher gusts between
20 and 25 knots overnight. /10
&&
.PREV DISCUSSION... /issued 851 PM CST Tue Nov 29 2016/
DISCUSSION...See updated information for land areas below.
UPDATE...Upper air map analysis this evening shows a large and vigorous,
positive tilt upper level storm system over the nation`s heartland.
East of the long-wave trof an active high level flow aloft is
positioned from the western Gulf to the east coast. A complex surface
pressure pattern exists with a quasi-stationary frontal zone draped
from the Appalachians to the TX coast. West of this boundary, another
frontal boundary was advancing southeast out of the southern plains.
Despite the presence of an anomalously deep moist profile along the
Gulf coast (precipitable water values 1.3 to 1.5 inches ranging from
160 to 190% of normal) southeast of these boundaries, current
soundings indicate a rather pronounced warm nose in the mid levels
between 700 and 750MB. This has been acting as a cap and keeping
radar activity minimal this evening. Appears showers and storms will
stay isolated to low end scattered in coverage through the remainder
of the evening along and west of I-65. Moving into the pre-dawn hours
Wednesday AM, a squall line of storms is forecast to organize and
move east over the Lower Mississippi River Valley.
The greatest severe weather threat appears to remain to our
northwest across central and northern Mississippi where an enhanced
to moderate risk zone is outlined by the storm prediction center.
This is where the best dynamics and instability will reside for
organized and more widespread severe storms. The latest high
resolution HRRR solutions bring the leading edge of the convective
line into interior southeast MS shortly before daybreak Wednesday.
Projecting forward in time, forecasters maintain a consistent message
on timing the line across the I-65 corridor between 9 AM and 1 PM
before exiting east of the area by 3 PM. The primary risk of severe
thunderstorms will be across southeast Mississippi and west of I-65
in southwest Alabama Wednesday morning with the greatest threat being
damaging straight-line winds. /10
PREV DISCUSSION... /issued 558 PM CST Tue Nov 29 2016/
DISCUSSION...See updated information for marine areas and aviation
discussion below.
MARINE...Even though a moderate to strong onshore flow exists,
there have been reports of fog, which is of advective type, over
Mobile Bay. Considering reports and port visibilities down to near 3
statute miles, have made an update to Mobile Bay portion of the marine
zones to mention fog tonight. Small craft caution wording for area
bays and sounds will continue, while advisories remain in place over
the open Gulf waters. /10
AVIATION...
00Z issuance...A steady stream of clouds, of multiple bases,
continues to move from the Texas coast, east northeast into the
southeast US atop a stationary frontal zone. MVFR bases this evening
over the central Gulf coast, lowers to IFR levels. VSBY lowers to
MVFR categories, potentially IFR at times overnight along with
passage of isolated to scattered shra. Timing of next convective band
over the terminals forecast by and shortly after daybreak Wed with
strong convective wind gusts and vsby lowering to LIFR categories in
+TSRA. South winds 9 to 14 knots with occasional higher gusts
between 20 and 25 knots overnight. /10
PREV DISCUSSION... /issued 432 PM CST Tue Nov 29 2016/
NEAR TERM /Now Through Wednesday/...The upstream cold front remains
stalled across the central plains in the deep layer southwest flow
pattern due to a strongly positive tilt upper trough from the
northern plains into the southwestern states. This front will
finally get a kick start tonight as an upper shortwave rotating into
the southern plains ejects eastward. As the forcing with the
shortwave interacts with the front and a moist and unstable
environment over the Lower Mississippi River Valley, expect showers
and thunderstorms to break out this afternoon and evening and
congeal into a squall line late this evening which will move east
overnight. Across our area, gusty southerly winds will continue
tonight which will maintain high surf and dangerous rip currents at
the beaches.
We expect isolated to scattered showers and thunderstorms to
increase in coverage especially across western zones this evening.
The greatest severe weather threat will remain to our northwest
across central and northern Mississippi where an Enhanced Risk zone
is outlined. This is where the best dynamics and instability will
reside. The line of showers and thunderstorms will enter southeast
Mississippi between 5-9 AM and to the I-65 corridor between 9 AM and
1 PM before exiting east of the area by 3 PM. The best jet dynamics
will be pulling away to the north through this time frame and
instability levels will again be rather weak. Therefore the primary
risk of severe thunderstorms will be across southeast Mississippi
and west of I-65 in southwest Alabama Wednesday morning with the
greatest threat being damaging straightline winds.
A cooler and drier airmass will follow in the wake of the front
through the day on Wednesday with gradual clearing from northwest to
southeast by late afternoon. Highs will be in the mid and upper 60s
across northwest areas to mid 70s across the southeast. 13/JC
SHORT TERM /Wednesday night Through Friday night/...Surface high
pressure will move west to east across the region throughout the
short term period. Mostly clear skies and no rain is expected.
Nighttime lows in the 30s inland and lower 40s near the coast through
the period. Highs in the low to mid 60s each day. 12/DS
LONG TERM /Saturday Through Tuesday/...An unsettled weather pattern
returns to the area over the weekend and into the early part of next
week. Widespread rains become quite possible as an overrunning event
sets up over the weekend. Rainfall totals during the long term period
could approach 2 to 3 inches in some areas, but severe convective weather
is not anticipated. Daytime highs early in the period ranging from
upper 50s inland to mid 60s coast...slowly moderating to upper 60s
inland and lower 70s coastal by Tuesday. Nighttime lows ranging from
low/mid 40s interior to low/mid 50s coastal through the period. 12/DS
MARINE...Winds and seas will increase again tonight into Wednesday
as a cold front approaches from the west. The cold front moves
through the marine area Wednesday afternoon with a moderate to
strong northerly flow in its wake with seas up to near 9 feet well
offshore. A Small Craft Advisory is in effect for the Gulf waters
until 1 pm Wednesday. Scattered to numerous showers and thunderstorms
can be expected late tonight into Wednesday with some strong to
possibly severe with locally higher seas expected near storms. 13/JC
&&
.MOB WATCHES/WARNINGS/ADVISORIES...
AL...High Rip Current Risk through late Wednesday night for ALZ265-
266.
High Surf Advisory until 1 PM CST Wednesday for ALZ265-266.
FL...High Rip Current Risk through late Wednesday night for FLZ202-
204-206.
High Surf Advisory until 1 PM CST Wednesday for FLZ202-204-206.
MS...None.
GM...Small Craft Advisory until 6 PM CST Wednesday for GMZ650-655-670-
675.
&&
$$
This product is also available on the web at:
http://weather.gov/mob
Area Forecast Discussion
National Weather Service Blacksburg VA
452 AM EST Wed Nov 30 2016
.SYNOPSIS...
A cold front slides east to the mountains this afternoon, and east
of the piedmont this evening. High pressure will track from the
lower Mississippi Valley Thursday to the Southern Appalachians
Friday morning. Expect drier and cooler weather for the end of
the week.
&&
.NEAR TERM /THROUGH TONIGHT/...
As of 340 am EST Wednesday...
Radar has been pretty active this morning, with elevated instability
leading to thunderstorms moving across the New River Valley/Mountain
Empire and Alleghany Highlands, as well as portions of the piedmont.
The latest RAP showed this elevated instability lingering into mid
morning. There will be a break in the showers across the southeast
CWA with main axis of lift and moisture transport staying with the
front and upper dynamics across the TN Valley into the Central
Appalachians. Therefore will have higher pops in the mountains this
morning then models shift the axis east into the piedmont by late
afternoon.
There is a decent amount of lift and wind energy to give most of
not all the forecast area a good rain. Unstable air is limited by
clouds and showers but with increase in the jet should be enough
dynamical forcing to string some thunder in the forecast, especially
in the foothills/piedmont. The Storm Prediction Center shows our
eastern 2/3rds of the forecast area in a marginal risk, mainly
concerned about winds mixing down with line of showers and isolated
storms. Will mention this in the HWO, but more along/east of the
Blue Ridge as think the west will be stable enough to keep stronger
winds from mixing down past 4000 ft. Some of the higher terrain this
morning could see some gusts to 45 mph, although not enough to have
a wind advisory.
Temperatures despite the clouds and showers will warm into the lower
to mid 70s east to mid to upper 60s west.
Tonight, the front moves east of the forecast area by midnight with
showers ending. There will be clearing skies as we head into late
tonight in the east while upslope keeps clouds in the mountains,
with slight chance of showers over western Greenbrier County. Colder
air will star to track in overnight west of the Blue Ridge with lows
in the upper 30s to lower 40s, while the foothills/piedmont slide
into the mid 40s to around 50.
There will be a gradient behind the front tonight but 8h winds are
around 30 kts or less, so winds should be under 30 mph in the gust
dept, except possible gusts to 35 mpg across the Alleghany
Highlands, higher ridges.
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
As of 400 AM EST Wednesday...
The final and most significant short wave of the slowly filling eastern
U.S. low will be exiting to the east at the beginning of this period.
The pattern will transition back to a cooler/seasonal pattern.
Upslope trajectories are not overly favorable, generally a WSW-W
flow across the Alleghanys. This in combination with the lifting
out/filling upper low and the gradual return to southwest flow
aloft does not lead to a very favorable setup for snow. In
general, the GFS is the only model indicating much threat for any
upslope rain/snow showers. Will hold onto some slight chance
-SHSN across western Greenbrier through Thu morning, then drop.
For Friday, there is a very weak clipper evident along the bottom
of the departing upper low. This may induce a brief period of snow
showers across the northern Alleghanys again, mainly north of the
RNK CWA, but again the GFS remains one of the few models to depict
any QPF with this feature as far south as western Greenbrier. Will
carry a low slight chance pop to account for this feature. Both
events are barely worth mentioning from my analysis.
Otherwise, the main story this period will be much cooler
temperatures. 850mb temps will fall back below 0C across most of
the CWA during the day Thu and remain in this range well into the
weekend, bottoming out Saturday in the -6C range north to around
0C south. Temperatures will trend back toward seasonal levels with
lows in the 20s and 30s and highs in the 40s and 50s, colder
mountains.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 430 AM EST Wednesday...
The focus during this period will be on a southern latitude system
originating from a closed upper low over Mexico. There remain
significant differences in how this system will evolve with the
GFS still slow to bring the parent system out of Mexico, but now
on board with what the ECMWF has been showing for several days,
namely a northern stream system traversing the region Sunday into
Monday. Models have been trending toward a weaker closed low and
greater potential for northern stream energy to pick up the system
sooner, thus forecast trends lean toward the faster ECMWF
solution. These changes will result in chance pops being
introduced in the southwest part of the CWA Saturday night/early
Sunday, increasing to likely Sunday, but then decreasing quicker
back to chance or less by Monday.
P-type may be a concern early Sunday with surface temps hovering
in the 29F to 32F range and 850mb temps struggling to rise above
zero. This would especially be true for areas where the
precipitation arrives late Saturday night/early Sunday. At any
rate, especially per ECMWF, warm air will begin to surge northward
during the day changing any frozen/freezing precipitation to
liquid. The caveat may be the potential for an "in-situ" wedge to
develop and keep the threat for winter precipitation in the area
longer, quite common at this time of year, and something the
models are poor at resolving.
Uncertainty continues for the remainder of the period as the GFS
still has the parent upper low coming out of Mexico and bringing
another swath of precipitation across the southeast/Mid-Atlantic
Monday into Tuesday, while the ECMWF has moved the entire system
out of the region, leaving dry weather in place beyond Monday
night. Have nudged the forecast toward the preferred ECMWF.
After a seasonably chilly/slightly below normal period through
the weekend, expect a return to milder temperatures early next
week as heights build aloft across the southeast U.S. in the wake
of the weekend storm system.
&&
.AVIATION /09Z WEDNESDAY THROUGH SUNDAY/...
As of 1145 PM EST Tuesday...
Expecting MVFR to IFR clouds to fill in over southwest Virginia,
northwest North Carolina and southeast West Virginia tonight. LIFR
fog developed at locations that had rain Tuesday afternoon and
stay cloud free longer. Winds will pick up overnight, especially
at higher elevations as the low level increases from the
southwest. Low confidence on the timing for when visibilities will
improve as fog erodes.
Area of upper diffluence that was providing lift for the showers
and thunderstorms over Mississippi and Tennessee will move into
the region late tonight. Guidance was in good agreement keeping
much of the area dry until after 06Z/1AM. Some warm air advection
also in the region tonight and Wednesday morning which will aide
in lift.
Next band of heavier showers and will cross the region from west
to east Wednesday afternoon allowing for widespread sub-VFR cigs
and vsbys until the front crosses Wednesday evening. Shallow
convection may enhance the winds. High confidence on the passage
of the front and associated moderate showers but lower confidence
on the exact timing.
Extended aviation discussion...
Improving conditions expected after the upper low and final short
wave move east of the area later Wednesday night. Conditions
should become VFR east of the Blue Ridge into the weekend.
Upslope clouds and potentially a weak clipper system could bring a
low chance of rain or snow showers into the western sites Thursday
and Friday along with lingering MVFR cigs before conditions
improve there as well over the weekend.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...JH/WP
NEAR TERM...WP
SHORT TERM...RAB
LONG TERM...RAB/RCS
AVIATION...AMS/JH
Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
311 AM EST Wed Nov 30 2016
.SYNOPSIS...
08Z water vapor and H4 RAP analysis continues to show a highly
amplified and rather complex upper level pattern in place over the
CONUS. To be honest...it would be very difficult to describe all the
features through text and not get confusing. So...for our local
forecast in the next couple of days...the main players include
longwave troughing covering the mid-section of the
country...northeastward through the Great Lakes into south-
central Canada...and upper ridging extending from the western
Caribbean to the Florida peninsula. The trough through the
central portion of the conus is anchored by a large cut-off low
spinning over the Dakotas/Minnesota. I actually wrote that exact
line last night in my AFD...because that upper low has moved
essentially nowhere in the past 24 hours. Toward the base of this
trough we find a strong lobe of shortwave energy ejecting eastward
over the southern Plains. This energy will move very rapidly and
cross the lower/middle MS valley into the TN/OH valley by this
evening. The energy will be forced northeastward in part by the
protective cover of the upper ridge over our heads...and this
protective ridge will generally prevent any substantial precip was
reaching our forecast area from this passing system. Will likely
see a few light showers...but will talk more about that in the
short term discussion below.
At the surface...Florida peninsula is resides within a deep and
moist southeast/south flow between a cold front slowly moving
through the deep south...and a large ridge of high pressure over
the western Atlantic. Temperatures are usually warm for the early
morning hours of the final day of November. Most observations are
in the mid/upper 60s...with quite a few lower 70s still showing
up. Generally speaking we will not see these temps fall more than
a couple more degrees before sunrise. Starting to see a few
pockets of fog develop in the normally prone spots across the
interior and mainly the Nature coast. A few dense spots are
possible for the early morning commute...especially along and
north of the I-4. Will continue to monitor...but currently not
anticipating coverage to require dense fog hazards/advisory this
morning.
&&
.Short Term (Today through Thursday)...
Today...Strong shortwave energy will move into the mid/lower MS
valley later this morning and then shear out rapidly to the
northeast around then northern periphery of the mid/upper ridge over
the Florida peninsula. An initially strong cold front will move into
AL/GA/FL panhandle later today...and then both slow down and become
less defined as it moves into the NE Gulf/Florida Big Bend region
this evening. Ahead of this front...the entire forecast area will
reside through today within the warm sector of this system...with
very low rain chances and well above normal temperatures. Very late
in the day (after 4PM) as the front begins to approach the FL Big
Bend...can not rule out a narrow broken line of light showers
getting close to Levy County. However...really not going to be big
deal in terms of rainfall or rainfall potential. The majority of the
upper level synoptic support for ascent will have lifted off with
the shortwave into the mid-atlantic states...with a marked decrease
in the upper level divergence associated with the northern stream
jet. Closer to the surface...what is initially shown by the
GFS/NAM/EC to be a healthy swath of moisture flux convergence along
the front over the Fl Panhandle and points north...weakens rapidly
after 18Z. Other than leftover subtle low level convergence along
the frontal boundary...there is little signal in the evolution of
the mass fields to suggest anything other than a decaying broken
line of showers reaching our northern Nature Coast zones toward dark
and into the later evening hours.
Temperatures for your Wednesday will be well above normal...with
many locations away from the immediate FL west coast rising into the
lower and even middle 80s. Dewpoints will also be on the high side
making it feel like its much earlier in the fall then the final day
of November. Along the immediate coast...and already southerly
onshore component is likely to veer a bit more during the afternoon
in response to the low level mass changes brought on by strong
terrestrial heating. This "sea-breeze" component will help to advect
the "cooler" low level air over the shelf waters onshore within a
perhaps a couple miles of the coast. Beyond a couple miles from
the water...this cooling influence is likely to virtually
disappear. The persistent southerly flow may result in some
locally stronger longshore currents / rip current zones as well.
Overall conditions do not warrant a rip current hazard headline
for today...but those that are considering an outing to the beach
should pay attention to the flags flying at their beach of choice.
Tonight...weak frontal boundary drops down into the Nature Coast/NE
Gulf during the overnight hours. Nothing changes from the evening in
terms of precip efficiency...and likely looking at just a narrow
broken line of showers dropping southward toward the I-4
corridor...forced mainly by weak 1000-700mb directional convergence.
Looking at cross-sectional analysis from I-4 northward...the
available moisture tonight is all below the 700mb layer...giving
more confidence to only light/weakly forced shower activity. Given
all the guidance...including the GEFS mean...do not anticipate
this isolated activity to reach the I-4 corridor/Tampa Bay area
until around dawn (if at all).
Thursday...One final shortwave trough migrating through the deep
south round the southern periphery of the deamplifying eastern
trough will provide the momentum push to finally propel the frontal
boundary into our southern zones...and then south of the FL
peninsula Thursday night. The stretching of the front along a
longitudinal axis by Thursday morning parallel to the deep layer
flow over the peninsula will transition the boundary from katafront
to an anafront configuration. Anafront configurations favor a band
of moisture/clouds lift along and even behind the surface boundary
location. Therefore...although some drier air will begin to filter
down into our northern zones at the surface during the day...it is
unlikely that we will see the defined clearing normally experienced
with passing cold fronts. The continued proximity of the frontal
boundary may still be enough to force a few isolated light
showers...especially with the onset of diurnal heating...nothing
that should ruin outdoor activities...and certainly not a drought
buster. Temperatures thursday again will be forecast into the lower
80s from the I-4 corridor southward (few degrees cooler at the
beaches)...with somewhat cooler air in the 70s behind the front for
the Nature coast zones. Temps may be held down north of I-4 by the
combination of beginning air mass change is potential for small wet-
bulbing effect from sprinkles within the anafrontal moisture band
falling into the drier air filtering in at the surface.
Lets talk sea-fog potential late today/tonight. The prediction of
sea-fog is very difficult. Its a subtle balance between sea surface
temperatures that can change since the last satellite estimate...and
dewpoint temperature that can be off in any forecast by a couple of
degrees at any location. The problem arises when one considers the
enormous economic impact that sea-fog can have on marine
operations...especially with regards to Tampa Bay. Looked very
closely at the current satellite SSTs along the entire coast and the
forecast dewpoints from many of the various reliable NWP members
later today into tonight. Generally...the dewpoint/SST difference
falls just under what is commonly considered to be favorable for sea-
fog. Like to see this difference 3-5+ degrees with a steady...but
not too strong breeze before getting really concerned. This event
simply does not meet these criteria with current guidance/obs. Best
chance would be up toward the coasts of Levy/Dixie counties where
SSTs are coolest...but leaning against a widespread event even up
there. For now...will leave mention out of the forecast...but
conditions will need to be monitored very closely later today into
the evening.
&&
.LONG TERM (Thursday night through next Wednesday)...
Period will begin with a strong U/L disturbance digging near the
four corners area with quasi-zonal flow from the southern Plains
to the mid Atlantic coast. A strong sub-tropical ridge will extend
across much of the Gulf of Mexico and over the Florida peninsula
and Caribbean. U/L energy will cut-off near Baja California over
the weekend while a S/W disturbance pushes across the
northern/central Plains. Next strong upstream disturbance will dig
over the Pacific northwest early next week which will open up the
cut-off low over Baja and ejecting it across the southern Plains.
The U/L energy will shear out and will push rapidly across the
Lower Mississippi Valley and southeast U.S. Monday night and
Tuesday. On Tuesday and Wednesday, the strong west coast
disturbance will dig through the inter- mountain west and southern
Plains. This will act to build the downstream ridge over Florida.
At the surface, a weak cold front will dissipate across the central
Florida peninsula Thursday night. Surface high pressure will build
over the southeast U.S. and Florida on Friday, and will move to the
mid Atlantic coast on Saturday. An area of low pressure will
develop over the Lower Mississippi Valley Saturday and will push
rapidly across the southeast U.S. Sunday and off the mid Atlantic
coast Sunday night. A trailing cold front will stall across the
northern Gulf coast and north Florida as it becomes parallel to the
U/L flow. A chance of showers will develop Sunday night and Monday
across west central Florida with highest pops over the northern
nature coast. Next upstream disturbance will push across the
southern Plains Monday night and will ride over the frontal boundary
across the northern Gulf of Mexico. This will induce an area of low
pressure to develop over the Lower Mississippi Valley. With quasi-
zonal U/L flow persisting across the southern U.S. the area of low
pressure will push across the southeastern states Tuesday and off
the mid Atlantic coast Tuesday night. Although the main U/L energy
and frontal boundary will remain north of the forecast area, deep
tropical moisture combined with weak instability across west central
and southwest Florida will create a chance of showers Tuesday and
Tuesday night. Temperatures will run near climatic normals Friday
and Saturday. As the U/L ridge builds over the forecast area and
boundary layer winds veer southeast, temperatures will climb 5 to 10
degrees above climatic normals Sunday through the middle of next
week.
&&
.AVIATION (30/06Z through 01/06Z)...
Guidance continues to suggest IFR cigs for most terminals in the
hours surrounding dawn. Statistical and ensemble guidance has been
far too aggressive past several night and have limited
restrictions to MVFR cigs between 09-13Z. Will monitor and update
as necessary. General VFR conditions with gusty southerly breeze
for most of the daylight hours of Wednesday. Greater potential for
IFR/MVFR cigs tonight into early Thursday morning...especially for
Tampa Bay Area/Sarasota terminals beginning by 04-06Z.
&&
.MARINE...
Elevated southeast to south winds to cautionary level at times
away from the coast continue this morning ahead of an approaching
cold front. Winds drop below cautionary levels tonight as the
front drops south into the northeast Gulf of Mexico. Cold front
will slowly settle southward during Thursday...shifting winds to
the north in its wake. Winds in the wake of the front will approach
cautionary levels at times through Friday night...especially away
from the immediate coast.
There is some potential for patchy sea fog tonight...especially
north of Tarpon Springs...however widespread dense sea fog is not
anticipated. A more detailed discussion about sea fog can be found
in the short term section above.
&&
.FIRE WEATHER...
Abundant low level moisture will keep relative humidity values
well above critical levels through Thursday. A weak cold front
will bring a chance for a few light showers tonight into Thursday
across mainly the I-4 corridor northward...however rainfall totals
should be on the light side. The front will slip south of the
region later Thursday/Thursday night allowing a cooler and drier
airmass to filter down from the north. Relative humidity values
may briefly drop below 35% across the Nature coast zones Friday
afternoon...however winds are light and ERC values are in the
20s...preventing the potential for red flag conditions.
&&
.Preliminary Point Temps/PoPs...
TPA 81 67 78 60 / 10 20 20 10
FMY 83 67 82 66 / 0 10 10 10
GIF 83 66 83 61 / 10 10 20 10
SRQ 79 67 78 62 / 0 10 20 10
BKV 82 66 77 55 / 10 20 30 10
SPG 79 67 77 63 / 10 20 20 10
&&
.TBW WATCHES/WARNINGS/ADVISORIES...
FL...Beach Hazards Statement through Thursday evening for
Coastal Sarasota.
Gulf waters...None.
&&
$$
SYNOPSIS/SHORT TERM/AVIATION/MARINE/FIRE WX...Mroczka
LONG TERM/DECISION SUPPORT...Oglesby
Area Forecast Discussion
National Weather Service Wakefield VA
1045 AM EST Wed Nov 30 2016
.SYNOPSIS...
A cold front will approach from the west today, then pushes across
the Mid Atlantic region tonight into Thursday morning. High
pressure slowly builds into the area Thursday through Sunday.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Late this morning, upper low pressure was located over MN/W, with
sfc low pressure cntrd over Lake Superior and nrn Lake Michigan. A
cold front extended fm the low swrd thru ern IN and wrn KY/TN.
Warm front and associated showers acrs portions of the area
earlier this morning, was moving N of the CWA late this morning.
Have adjusted Pops downward a bit acrs most of the area for this
aftn into early this evening, based on latest rdr trends, timing
of cold front pushing E, and HRRR reflectivity fcst. Southerly
winds and possible breaks in the clouds, will help temps climb
into the 70s over most of the region. Have slgt chc of thunder all
locations. The cold front will approach the extrm wrn counties by
early this evening.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY/...
The cold front pushes across the FA and off the coast tonight into
early Thu morning...w/ shras (isold tstms). Gusty winds and heavy
downpours a possibility with any tstms. Clearing out fm WNW to ESE
late Wed ngt into Thu morning...as WNW flow behind the front
ushers drier air into the region. Lows tonight fm the u40s-around
50F NW to the around 60F SE.
Dry/cooler wx expected Thu thru Fri...as W flow dominates the
area. Sfc hi pres gradually builds toward the region fm the WNW.
Generally mostly sunny both days...w/ highs Thu in the l-m60s...
highs Fri in the l-m50s. Lows Thu ngt fm the l-m30s to around 40F.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Cool high pressure is expected to be centered from the
Mississippi Valley through the Southeast Conus Friday night into
Saturday. High pressure builds over the Mid-Atlantic region
Saturday night into Sunday as a split flow pattern develops aloft,
with a srn stream system tracking along the Gulf Coast States, and
a nrn stream wave diving into the Upper Midwest. This will result
in dry conditions under a mainly clear sky, although high clouds
may increase by Sunday. Temperatures are expected to be slightly
below seasonal averages, but within -1 st dev. Forecast lows
Friday night and Saturday night range from the low 30s inland to
the mid/upper 30s along the coast, with highs Saturday/Sunday in
the upper 40s to low 50s. GFS/ECMWF keep the srn stream system
south of the region Sunday night into Monday. However, the ECMWF
is more aggressive with the nrn stream wave, but the net result
may be minimal with respect to sensible weather as the system will
be moisture starved. High pressure returns later Monday into
Monday night, with low pressure approaching from the west during
the Tuesday/Tuesday night timeframe. At this time the 29/12z GFS
is about 12hrs faster than the 29/12z ECMWF.
&&
.AVIATION /16Z WEDNESDAY THROUGH SUNDAY/...
LIFR/IFR (mainly cigs) inland w/ area of shras moving through
mainly NE portions of FA. Widespread LIFR/IFR conditions expected
until mid/late morning. Expect some breaks in the clouds by this
afternoon w/ conditions returning to VFR. Breezy again...w/ S
gusts around 25 to 30 kt. Cold front pushes across the region this
evening/tonight w/ shras and possible isold T. Sfc hi pres slowly
builds in through the end of the work week...resulting in VFR/fair
wx.
&&
.MARINE...
SCAs remain in effect for the coastal waters this morning. SCAs
begin for the Bay, rivers and sound at Noon.
A cold front is expected to push through the Ohio Valley
today and then push off the Mid-Atlantic Coast late tonight. The
wind will increase from the south at 15-25 kt by this afternoon
and continue into this evening. The wind then becomes westerly at
10-15kt (minimal CAA) behind the front late tonight into
Thursday. Waves will build to 3-4 ft on the Ches Bay with 5-7 ft
seas. A nw wind of 10-15kt/15-20kt ocean should prevail Friday
into Saturday as high pressure builds across the Southeast Conus
and low pressure persists over Atlantic Canada. High pressure
builds over the region Saturday night into Sunday. Seas subside
from 3-4ft to 2-3ft, with ~2ft waves in the Bay.
&&
.CLIMATE...
Well above normal temperatures are forecast Wednesday. Some
temperatures will approach record highs.
Records:
Richmond: 77 (1933)
Norfolk: 79 (2001)
Salisbury: 74 (1933)
Elizabeth City: 80 (2001)
Wallops Island: 74 (1991)
&&
.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...None.
NC...None.
VA...None.
MARINE...Small Craft Advisory until 1 AM EST Thursday for ANZ635>638.
Small Craft Advisory until 4 AM EST Thursday for ANZ630>634.
Small Craft Advisory until 6 AM EST Thursday for ANZ654-656-
658.
Small Craft Advisory until noon EST Thursday for ANZ650-652.
&&
$$
SYNOPSIS...ALB/TMG
NEAR TERM...ALB/TMG
SHORT TERM...ALB/TMG
LONG TERM...AJZ
AVIATION...ALB/SAM
MARINE...JDM
CLIMATE...AKQ
Area Forecast Discussion
National Weather Service Birmingham AL
540 AM CST Wed Nov 30 2016
.UPDATE...
For 12Z Aviation.
&&
.SHORT TERM...
Today and Tonight.
The 06Z BMX sounding indicates an unusually unstable air mass for
this time of day/year with SBCAPE of 1400 J/kg and MLCAPE of 730
J/kg. This combined with 0-1 shear of 33 kts, 0-6 shear of 64 kts,
and effective SRH of 300 m2/s2 will maintain a threat of tornadoes
throughout tonight and during the day on Wednesday as well.
Lifting of the dry layer aloft will also result in release of
potential instability and continue to steepen the mid-level lapse
rates. The strong shear and lack of strong upper- level forcing
has kept a true squall line from forming, with the convective line
extending from Louisiana to north AL remaining cellular in nature.
The HRRR indicates that this will continue. Both discrete
supercells ahead of the line and embedded supercells within the
line will continue to pose a threat for tornadoes. The tornado
watch was recently expanded to include Bibb, Jefferson, and Blount
counties, with a good chance of an additional watch beyond the
current 5AM expiration time including the areas further southeast. The
severe threat will continue to push southeastward, reaching the
I-20 corridor between about 3 and 6 AM and the I-85 corridor
between 8 AM and noon, exiting the farthest southeast counties
between 1 and 3 PM. Drier and cooler air will move in behind the
front this afternoon and evening.
32/Davis
.LONG TERM...
Thursday through Tuesday.
With this storm system to our east on Thursday, we will be back into
the high pressure realm for a couple of days, but no worries, the
dry spell will only last into the first half of the weekend. By
Friday afternoon a disturbance will begin to slide northward out of
the Gulf of Mexico and move into Louisiana by Saturday morning. This
disturbance will slide along and ahead of a cold front, working into
the western portion of Central Alabama by Saturday afternoon and
overspread the area during the day Sunday. Will have to monitor the
northward trends of the 60+ dewpoints as we get into Sunday
afternoon and Sunday evening. The 00Z GFS is indicating some mid 60s
in the southeast late Sunday afternoon, while the 12Z Euro keeps
dewpoints below 60 the entire time. However the 00Z Euro now brings
60+ dewpoints into the entire forecast area by Sunday evening, therefore
bringing a risk of severe weather into the area Sunday through
Monday evening. The dilemma here is the overall pattern. While we
remain in a very progressive pattern the GFS hangs the mid level
low back into the Four Corners area while the Euro now keeps the
trough moving and brings a potentially strong vort max into the
area by Monday morning. Will re-evaluate this tomorrow night and
see what if any additional changes need to be made.
We will remain fairly wet for the rest of the forecast as well as a
second trough and showers and storms move into the area Wednesday
night into Thursday. Again some differences in the overall timing
and strength will preclude any mention of severe with this system as
well, but there could be a small window here as well.
16
&&
.AVIATION...
12Z TAF Discussion.
While we have been waiting on the line to finally push through the
area overnight, we finally are seeing the push. Tried to time out
the line of thunderstorms in the locations. Most areas will clear
out this afternoon as the system exits the region.
16
&&
.FIRE WEATHER...
Showers and storms, some severe, will remain in the area through
this afternoon. Drier air should move into the area on Thursday and
Friday but moisture returns Saturday with another round of showers
expected Sunday through Tuesday. A third storm system will work into
the area by next Wednesday. So an overall wet pattern will be in
place for the next next 7 to 10 days.
16
&&
.PRELIMINARY POINT TEMPS/POPS...
Gadsden 68 38 56 30 57 / 100 0 10 0 0
Anniston 69 39 58 32 59 / 100 0 10 0 0
Birmingham 67 39 58 33 59 / 100 0 10 0 0
Tuscaloosa 67 39 59 32 61 / 90 0 10 0 0
Calera 69 39 58 33 60 / 100 0 10 0 0
Auburn 70 42 60 36 60 / 100 10 10 0 0
Montgomery 73 41 62 34 63 / 100 0 10 0 0
Troy 72 43 62 35 62 / 100 10 10 0 0
&&
.BMX WATCHES/WARNINGS/ADVISORIES/...
None.
&&
$$
Area Forecast Discussion
National Weather Service Blacksburg VA
954 AM EST Wed Nov 30 2016
.SYNOPSIS...
A cold front slides east to the mountains this afternoon, and east
of the piedmont this evening. High pressure will track from the
lower Mississippi Valley Thursday to the Southern Appalachians
Friday morning. Expect drier and cooler weather for the end of
the week.
&&
.NEAR TERM /THROUGH TONIGHT/...
As of 950 am EST Wednesday...
Morning update will reflect lower chances of precipitation across
the southeast portion of the forecast area until the mid-afternoon
hours. This delay in arrival of the bulk of the precipitation
should allow for high temperatures to be a degree or two warmer in
this region. Latest radar trends show the ongoing precipitation
along or west of the crest of the Blue Ridge. Latest guidance does
well with matching the current returns with limited, if any,
coverage in the far southeast until the afternoon. No other
significant changes will be made at this time.
As of 340 am EST Wednesday...
Radar has been pretty active this morning, with elevated instability
leading to thunderstorms moving across the New River Valley/Mountain
Empire and Alleghany Highlands, as well as portions of the piedmont.
The latest RAP showed this elevated instability lingering into mid
morning. There will be a break in the showers across the southeast
CWA with main axis of lift and moisture transport staying with the
front and upper dynamics across the TN Valley into the Central
Appalachians. Therefore will have higher pops in the mountains this
morning then models shift the axis east into the piedmont by late
afternoon.
There is a decent amount of lift and wind energy to give most of
not all the forecast area a good rain. Unstable air is limited by
clouds and showers but with increase in the jet should be enough
dynamical forcing to string some thunder in the forecast, especially
in the foothills/piedmont. The Storm Prediction Center shows our
eastern 2/3rds of the forecast area in a marginal risk, mainly
concerned about winds mixing down with line of showers and isolated
storms. Will mention this in the HWO, but more along/east of the
Blue Ridge as think the west will be stable enough to keep stronger
winds from mixing down past 4000 ft. Some of the higher terrain this
morning could see some gusts to 45 mph, although not enough to have
a wind advisory.
Temperatures despite the clouds and showers will warm into the lower
to mid 70s east to mid to upper 60s west.
Tonight, the front moves east of the forecast area by midnight with
showers ending. There will be clearing skies as we head into late
tonight in the east while upslope keeps clouds in the mountains,
with slight chance of showers over western Greenbrier County. Colder
air will star to track in overnight west of the Blue Ridge with lows
in the upper 30s to lower 40s, while the foothills/piedmont slide
into the mid 40s to around 50.
There will be a gradient behind the front tonight but 8h winds are
around 30 kts or less, so winds should be under 30 mph in the gust
dept, except possible gusts to 35 mpg across the Alleghany
Highlands, higher ridges.
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
As of 400 AM EST Wednesday...
The final and most significant short wave of the slowly filling eastern
U.S. low will be exiting to the east at the beginning of this period.
The pattern will transition back to a cooler/seasonal pattern.
Upslope trajectories are not overly favorable, generally a WSW-W
flow across the Alleghanys. This in combination with the lifting
out/filling upper low and the gradual return to southwest flow
aloft does not lead to a very favorable setup for snow. In
general, the GFS is the only model indicating much threat for any
upslope rain/snow showers. Will hold onto some slight chance
-SHSN across western Greenbrier through Thu morning, then drop.
For Friday, there is a very weak clipper evident along the bottom
of the departing upper low. This may induce a brief period of snow
showers across the northern Alleghanys again, mainly north of the
RNK CWA, but again the GFS remains one of the few models to depict
any QPF with this feature as far south as western Greenbrier. Will
carry a low slight chance pop to account for this feature. Both
events are barely worth mentioning from my analysis.
Otherwise, the main story this period will be much cooler
temperatures. 850mb temps will fall back below 0C across most of
the CWA during the day Thu and remain in this range well into the
weekend, bottoming out Saturday in the -6C range north to around
0C south. Temperatures will trend back toward seasonal levels with
lows in the 20s and 30s and highs in the 40s and 50s, colder
mountains.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 430 AM EST Wednesday...
The focus during this period will be on a southern latitude system
originating from a closed upper low over Mexico. There remain
significant differences in how this system will evolve with the
GFS still slow to bring the parent system out of Mexico, but now
on board with what the ECMWF has been showing for several days,
namely a northern stream system traversing the region Sunday into
Monday. Models have been trending toward a weaker closed low and
greater potential for northern stream energy to pick up the system
sooner, thus forecast trends lean toward the faster ECMWF
solution. These changes will result in chance pops being
introduced in the southwest part of the CWA Saturday night/early
Sunday, increasing to likely Sunday, but then decreasing quicker
back to chance or less by Monday.
P-type may be a concern early Sunday with surface temps hovering
in the 29F to 32F range and 850mb temps struggling to rise above
zero. This would especially be true for areas where the
precipitation arrives late Saturday night/early Sunday. At any
rate, especially per ECMWF, warm air will begin to surge northward
during the day changing any frozen/freezing precipitation to
liquid. The caveat may be the potential for an "in-situ" wedge to
develop and keep the threat for winter precipitation in the area
longer, quite common at this time of year, and something the
models are poor at resolving.
Uncertainty continues for the remainder of the period as the GFS
still has the parent upper low coming out of Mexico and bringing
another swath of precipitation across the southeast/Mid-Atlantic
Monday into Tuesday, while the ECMWF has moved the entire system
out of the region, leaving dry weather in place beyond Monday
night. Have nudged the forecast toward the preferred ECMWF.
After a seasonably chilly/slightly below normal period through
the weekend, expect a return to milder temperatures early next
week as heights build aloft across the southeast U.S. in the wake
of the weekend storm system.
&&
.AVIATION /15Z WEDNESDAY THROUGH SUNDAY/...
As of 635 AM EST Wednesday...
Trying to zero in on the variably cigs/vsbys across the area,
which are more up and down east of the Alleghanys as showers are
intermittent. Appears enough mixing to take place through late
morning to eventually scour out the lower clouds and vsbys, but at
least until 14-15z will see IFR or lower at all sites. Steadier
showers will stay west of ROA/BCB through early afternoon then
spread east. Will see moderate showers at least in the mountains
this morning, then BCB/ROA in the 21-23z time frame and 22-00z
time frame LYH/DAN.
Model show cigs staying mostly MVFR or worse, but could see VFR at
times this afternoon in the piedmont/foothills.
Look for showers to end in BLF/LWB by 0z, and by 01-03z ROA east.
South to southwest winds will gust up to 20kts at times in the
mountains this morning, then winds shift to the west after fropa
this afternoon/evening from west to east.
As we head into the overnight skies will be stay bkn/ovc in the
mountains with MVFR to low end VFR expected while it clears out
from Roanoke, east. Winds should stay breezy especially in the
mountains and Roanoke tonight, with some gusts to 30 kts.
Extended aviation discussion...
VFR thru Saturday, with high pressure in control. Another storm
system enters the area the 2nd half of the weekend and should
bring more precip and lower cigs/vsbys.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...JH/WP
NEAR TERM...DS/WP
SHORT TERM...RAB
LONG TERM...RAB/RCS
AVIATION...AMS/WP
Area Forecast Discussion
National Weather Service Tallahassee FL
936 AM EST Wed Nov 30 2016
...Severe Weather Possible This Afternoon...
.UPDATE...
Based on this morning`s 12z data, the threat for severe weather
remains for this afternoon with the highest chances across the
western half of the area. Much of the previous discussion below
assessing that threat remains valid. We continue to watch with
great interest the approaching squall line in southern Alabama.
Low level moisture return ahead of it is impressive for this time
of year with dewpoints in the upper 60s to near 70 all the way up
through southeast Alabama. Perhaps this is being aided by the 1-2
degrees C above average Gulf of Mexico SSTs. The 12z soundings to
our west are pretty impressive with Birmingham observing around
1200 j/kg of SBCAPE, 0-1 km shear of 37 knots, and 0-6 km shear
of 77 knots. The New Orleans sounding was similar with SBCAPE
around 1500 j/kg and a strongly curved hodograph in the low
levels. Given that satellite imagery shows some breaks in the
cloud cover in our area ahead of the line, instability may rise to
at least 1000 j/kg through much of the western half of the area
this afternoon. In fact, the latest ensemble mean of CAM guidance
has values up to near 1400 j/kg in the Florida panhandle. There is
quite a bit of shear expected to be present with 0-6 km bulk shear
values over 50 knots and 0-1 km shear near 30 knots expected this
afternoon across the western half of the area according to the
RAP. The RAP also has 50 knot 850 mb flow translating across the
northwestern portion of the area from late this morning through
the afternoon hours. Given the observed shear in the Birmingham
and New Orleans sounding, the RAP seems believable.
Speaking of low level winds, given the breaks in the clouds, the
boundary layer will be well mixed today, and as the low level jet
translates across the area, it will become quite breezy this
afternoon. Based on the latest forecast soundings in BUFKIT, there
is the potential to see peak gusts near 35 knots across portions
of the area this afternoon outside of convection, mainly the
northern and western portions. As a result, a wind advisory has
been issued for those areas.
&&
.PREV DISCUSSION [559 AM EST]...
.NEAR TERM [Through Today]...
Low pressure system will track across the Great Lakes today with the
system pushing a strong cold front through the southeast. Already
are seeing a few light returns on radar indicating some light
rain/drizzle across the western portion of the CWA - expect the
coverage of light showers to increase this morning with scattered
showers and thunderstorms ahead of a main line of storms expected to
move through this afternoon/evening. Line of storms will move from
west to east across the forecast area and hi-res models show the
line along the western border around 17-19z.
Ahead of the front, southerly winds have brought plenty of moisture
to the area with Dewpoints across the western portion of the area
already in the 70s. A decent amount of CAPE for this time of year is
expected mid morning into the early afternoon across the western
half of the CWA. GFS shows values around 500-800 J/kg while some of
the high-res models are showing over 1000 J/kg. CAPE values trail
off for the late afternoon, but considering high shear, low CAPE
events, it`s still enough to continue the severe weather threat.
Plenty of shear with this event with 50-60kts deep layer shear, 20-
35kts low level shear and 0-1km helicity values of 150-250. All of
these severe values are best over the western half of the CWA and
given the setup could see severe storms with the best chances over
the western areas. SPC has the western areas in the slight risk of
severe storms, generally from Dawson, Georgia to Panama City, FL and
westward. The remainder of the CWA is a marginal risk. The most
likely timing of the severe storms will be late morning through the
afternoon. Given the higher shear values, combined with decent CAPE
values, a few tornadoes are possible today with the better chances
mainly west of Tallahassee. In addition to the tornado threat,
damaging winds will be possible, especially as the line of storms
moves through later today.
This is the first decent chance of severe weather for the CWA in
awhile and thus always a good reminder to review your severe weather
safety rules at ready.gov.
Aside from the severe weather threat today, winds will be elevated
and it will be noticeable breezy across the area. At this point
though, winds are forecast to remain below Wind Advisory criteria.
.SHORT TERM [Tonight Through Friday]...
By this evening, the cold front will stretch from southwest
Georgia southward to near Tallahassee. Instability should weaken
by this time, with CAPE generally less than 500 J/kg confined to
the south and east of the front. However, a strong low-mid level
jet will result in continued high shear values, with over 50 knots
of effective bulk shear and about 30 knots of 0-1 km shear near
Tallahassee. Low-level helicity values will also be quite high,
with 0-1 km helicity up to 200 m^2/s^2 near and southeast of the
front during the evening. As a result of the very low CAPE,
generally expect showers and only isolated thunderstorms along and
southeast of the front tonight. Due to the favorable shear and
helicity parameters, isolated shallow supercells cannot be ruled
out during the evening hours across the FL Big Bend and southwest
GA, although the tornado threat will definitely have diminished
by this time with very little instability remaining.
Expect temperatures to drop quickly behind the front, with
overnight lows ranging from the mid 40s in southeast AL to lower
60s across the eastern FL Big Bend region. A cool and dry airmass
will prevail in the wake of the front Thursday and Friday, with
highs in the mid-upper 60s each day under mostly clear skies.
.LONG TERM [Friday Night Through Wednesday]...
Dry conditions will persist through most of Saturday as deep layer
ridging remains in place across our area. Rain chances will
gradually increase from Saturday night through Monday, as easterly
flow becomes more southerly, and increased moisture from the Gulf
increases PWAT values above 1.5" from Sunday into Monday over much
of our area. There will not be much of a contribution from upper
level dynamics, as a strong jet will remain well to our north as
zonal flow or a broad upper ridge prevails. However, a warm front
will also move northward through the Gulf during this time, and
isentropic uplift to the north of this feature should enhance
rainfall potential. The front will weaken and become generally
stationary near our area on Tuesday and Wednesday, and with
continued ample moisture chances of rain will persist in our area.
Highs will be in the mid-upper 60s through the weekend, slightly
warming into the low-mid 70s next week. Lows in the 40s and lower
50s over the weekend will rise into the mid-upper 50s next week.
.AVIATION [Through 12Z Thursday]...
Mainly IFR to MVFR cigs across the TAF sites this morning with
mainly MVFR cigs continuing through the day. Winds will increase
this morning ahead of a cold front with gusts 20-30kts late
morning into the afternoon. Showers and isolated thunderstorms
will develop this morning and continue into the afternoon from TLH
to ABY and west. This will be ahead of a line of storms expected
to move through this afternoon and evening. Have included TSRA for
DHN and ECP for this afternoon and this may need to be extended
to the eastern TAF sites in future updates.
.MARINE...
A small craft advisory is in effect for our western zones through
this evening, as southerly winds will increase to 20 to 25 knots
ahead of the approaching cold front. Seas will increase to 5 to 7
feet with a few waves up to 9 feet well offshore in our western
zones, with 3 to 6 foot seas in our eastern zones. Elevated winds
and seas should continue through the weekend, with winds generally
from 15 to 20 knots and seas around 3 to 5 feet.
.FIRE WEATHER...
A cold front will move through the area tonight bringing rain to the
area today/tonight and strong winds to the area today. With the
increased moisture ahead of the front and higher RH values, this
will preclude need for Red Flag Warning, despite strong winds. High
dispersion values are expected today across the tri-state area.
Friday appears to be the driest day over the next week and given
current forecast, will need to watch RH values across Florida.
.HYDROLOGY...
While our area will receive some showers and isolated storms today
and more rain chances from Sunday into early next week, do not
expect rain will be heavy enough to cause any flooding at this
time. This is especially true considering the ongoing drought
conditions, which could see slight improvements as the active
pattern continues into next week.
&&
.PRELIMINARY POINT TEMPS/POPS...
Tallahassee 79 56 69 40 68 / 50 60 10 0 0
Panama City 77 53 66 46 66 / 90 50 10 0 0
Dothan 78 45 65 38 64 / 100 20 0 0 0
Albany 79 49 66 38 65 / 90 60 0 0 0
Valdosta 81 56 68 39 66 / 20 60 20 0 0
Cross City 80 62 71 41 69 / 10 60 30 10 0
Apalachicola 78 57 67 46 66 / 50 60 10 0 0
&&
.TAE WATCHES/WARNINGS/ADVISORIES...
FL...Wind Advisory until 7 PM EST /6 PM CST/ this evening for Calhoun-
Central Walton-Coastal Bay-Holmes-Inland Bay-Jackson-North
Walton-South Walton-Washington.
High Rip Current Risk through late tonight for Coastal Bay-
Coastal Franklin-Coastal Gulf-South Walton.
GA...Wind Advisory until 7 PM EST this evening for Baker-Ben Hill-
Calhoun-Clay-Colquitt-Decatur-Dougherty-Early-Grady-Irwin-
Lee-Miller-Mitchell-Quitman-Randolph-Seminole-Terrell-Tift-
Turner-Worth.
AL...Wind Advisory until 6 PM CST this evening for Coffee-Dale-Geneva-
Henry-Houston.
GM...Small Craft Advisory until 7 PM EST this evening for Coastal
waters from Apalachicola to Destin FL out 20 NM-Waters from
Apalachicola to Destin FL from 20 to 60 NM.
&&
$$
UPDATE...DVD
NEAR TERM...Fieux
SHORT TERM...Lahr
LONG TERM...Lahr
AVIATION...Fieux
MARINE...Lahr
FIRE WEATHER...Fieux
HYDROLOGY...Lahr
Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
657 AM EST Wed Nov 30 2016
.AVIATION...
Some MVFR ceilings will be possible later this morning once
daytime heating gets underway, otherwise general VFR conditions
with gusty southerly winds are expected for much of the daylight
hours today. A greater potential for MVFR/IFR ceilings exist
tonight into early Thursday morning, especially for Tampa Bay
Area/Sarasota terminals beginning by 04-06Z.
&&
.Prev Discussion... /issued 311 AM EST Wed Nov 30 2016/
SYNOPSIS...
08Z water vapor and H4 RAP analysis continues to show a highly
amplified and rather complex upper level pattern in place over the
CONUS. To be honest...it would be very difficult to describe all the
features through text and not get confusing. So...for our local
forecast in the next couple of days...the main players include
longwave troughing covering the mid-section of the
country...northeastward through the Great Lakes into south-
central Canada...and upper ridging extending from the western
Caribbean to the Florida peninsula. The trough through the
central portion of the conus is anchored by a large cut-off low
spinning over the Dakotas/Minnesota. I actually wrote that exact
line last night in my AFD...because that upper low has moved
essentially nowhere in the past 24 hours. Toward the base of this
trough we find a strong lobe of shortwave energy ejecting eastward
over the southern Plains. This energy will move very rapidly and
cross the lower/middle MS valley into the TN/OH valley by this
evening. The energy will be forced northeastward in part by the
protective cover of the upper ridge over our heads...and this
protective ridge will generally prevent any substantial precip was
reaching our forecast area from this passing system. Will likely
see a few light showers...but will talk more about that in the
short term discussion below.
At the surface...Florida peninsula is resides within a deep and
moist southeast/south flow between a cold front slowly moving
through the deep south...and a large ridge of high pressure over
the western Atlantic. Temperatures are usually warm for the early
morning hours of the final day of November. Most observations are
in the mid/upper 60s...with quite a few lower 70s still showing
up. Generally speaking we will not see these temps fall more than
a couple more degrees before sunrise. Starting to see a few
pockets of fog develop in the normally prone spots across the
interior and mainly the Nature coast. A few dense spots are
possible for the early morning commute...especially along and
north of the I-4. Will continue to monitor...but currently not
anticipating coverage to require dense fog hazards/advisory this
morning.
Short Term (Today through Thursday)...
Today...Strong shortwave energy will move into the mid/lower MS
valley later this morning and then shear out rapidly to the
northeast around then northern periphery of the mid/upper ridge over
the Florida peninsula. An initially strong cold front will move into
AL/GA/FL panhandle later today...and then both slow down and become
less defined as it moves into the NE Gulf/Florida Big Bend region
this evening. Ahead of this front...the entire forecast area will
reside through today within the warm sector of this system...with
very low rain chances and well above normal temperatures. Very late
in the day (after 4PM) as the front begins to approach the FL Big
Bend...can not rule out a narrow broken line of light showers
getting close to Levy County. However...really not going to be big
deal in terms of rainfall or rainfall potential. The majority of the
upper level synoptic support for ascent will have lifted off with
the shortwave into the mid-atlantic states...with a marked decrease
in the upper level divergence associated with the northern stream
jet. Closer to the surface...what is initially shown by the
GFS/NAM/EC to be a healthy swath of moisture flux convergence along
the front over the Fl Panhandle and points north...weakens rapidly
after 18Z. Other than leftover subtle low level convergence along
the frontal boundary...there is little signal in the evolution of
the mass fields to suggest anything other than a decaying broken
line of showers reaching our northern Nature Coast zones toward dark
and into the later evening hours.
Temperatures for your Wednesday will be well above normal...with
many locations away from the immediate FL west coast rising into the
lower and even middle 80s. Dewpoints will also be on the high side
making it feel like its much earlier in the fall then the final day
of November. Along the immediate coast...and already southerly
onshore component is likely to veer a bit more during the afternoon
in response to the low level mass changes brought on by strong
terrestrial heating. This "sea-breeze" component will help to advect
the "cooler" low level air over the shelf waters onshore within a
perhaps a couple miles of the coast. Beyond a couple miles from
the water...this cooling influence is likely to virtually
disappear. The persistent southerly flow may result in some
locally stronger longshore currents / rip current zones as well.
Overall conditions do not warrant a rip current hazard headline
for today...but those that are considering an outing to the beach
should pay attention to the flags flying at their beach of choice.
Tonight...weak frontal boundary drops down into the Nature Coast/NE
Gulf during the overnight hours. Nothing changes from the evening in
terms of precip efficiency...and likely looking at just a narrow
broken line of showers dropping southward toward the I-4
corridor...forced mainly by weak 1000-700mb directional convergence.
Looking at cross-sectional analysis from I-4 northward...the
available moisture tonight is all below the 700mb layer...giving
more confidence to only light/weakly forced shower activity. Given
all the guidance...including the GEFS mean...do not anticipate
this isolated activity to reach the I-4 corridor/Tampa Bay area
until around dawn (if at all).
Thursday...One final shortwave trough migrating through the deep
south round the southern periphery of the deamplifying eastern
trough will provide the momentum push to finally propel the frontal
boundary into our southern zones...and then south of the FL
peninsula Thursday night. The stretching of the front along a
longitudinal axis by Thursday morning parallel to the deep layer
flow over the peninsula will transition the boundary from katafront
to an anafront configuration. Anafront configurations favor a band
of moisture/clouds lift along and even behind the surface boundary
location. Therefore...although some drier air will begin to filter
down into our northern zones at the surface during the day...it is
unlikely that we will see the defined clearing normally experienced
with passing cold fronts. The continued proximity of the frontal
boundary may still be enough to force a few isolated light
showers...especially with the onset of diurnal heating...nothing
that should ruin outdoor activities...and certainly not a drought
buster. Temperatures thursday again will be forecast into the lower
80s from the I-4 corridor southward (few degrees cooler at the
beaches)...with somewhat cooler air in the 70s behind the front for
the Nature coast zones. Temps may be held down north of I-4 by the
combination of beginning air mass change is potential for small wet-
bulbing effect from sprinkles within the anafrontal moisture band
falling into the drier air filtering in at the surface.
Lets talk sea-fog potential late today/tonight. The prediction of
sea-fog is very difficult. Its a subtle balance between sea surface
temperatures that can change since the last satellite estimate...and
dewpoint temperature that can be off in any forecast by a couple of
degrees at any location. The problem arises when one considers the
enormous economic impact that sea-fog can have on marine
operations...especially with regards to Tampa Bay. Looked very
closely at the current satellite SSTs along the entire coast and the
forecast dewpoints from many of the various reliable NWP members
later today into tonight. Generally...the dewpoint/SST difference
falls just under what is commonly considered to be favorable for sea-
fog. Like to see this difference 3-5+ degrees with a steady...but
not too strong breeze before getting really concerned. This event
simply does not meet these criteria with current guidance/obs. Best
chance would be up toward the coasts of Levy/Dixie counties where
SSTs are coolest...but leaning against a widespread event even up
there. For now...will leave mention out of the forecast...but
conditions will need to be monitored very closely later today into
the evening.
LONG TERM (Thursday night through next Wednesday)...
Period will begin with a strong U/L disturbance digging near the
four corners area with quasi-zonal flow from the southern Plains
to the mid Atlantic coast. A strong sub-tropical ridge will extend
across much of the Gulf of Mexico and over the Florida peninsula
and Caribbean. U/L energy will cut-off near Baja California over
the weekend while a S/W disturbance pushes across the
northern/central Plains. Next strong upstream disturbance will dig
over the Pacific northwest early next week which will open up the
cut-off low over Baja and ejecting it across the southern Plains.
The U/L energy will shear out and will push rapidly across the
Lower Mississippi Valley and southeast U.S. Monday night and
Tuesday. On Tuesday and Wednesday, the strong west coast
disturbance will dig through the inter- mountain west and southern
Plains. This will act to build the downstream ridge over Florida.
At the surface, a weak cold front will dissipate across the central
Florida peninsula Thursday night. Surface high pressure will build
over the southeast U.S. and Florida on Friday, and will move to the
mid Atlantic coast on Saturday. An area of low pressure will
develop over the Lower Mississippi Valley Saturday and will push
rapidly across the southeast U.S. Sunday and off the mid Atlantic
coast Sunday night. A trailing cold front will stall across the
northern Gulf coast and north Florida as it becomes parallel to the
U/L flow. A chance of showers will develop Sunday night and Monday
across west central Florida with highest pops over the northern
nature coast. Next upstream disturbance will push across the
southern Plains Monday night and will ride over the frontal boundary
across the northern Gulf of Mexico. This will induce an area of low
pressure to develop over the Lower Mississippi Valley. With quasi-
zonal U/L flow persisting across the southern U.S. the area of low
pressure will push across the southeastern states Tuesday and off
the mid Atlantic coast Tuesday night. Although the main U/L energy
and frontal boundary will remain north of the forecast area, deep
tropical moisture combined with weak instability across west central
and southwest Florida will create a chance of showers Tuesday and
Tuesday night. Temperatures will run near climatic normals Friday
and Saturday. As the U/L ridge builds over the forecast area and
boundary layer winds veer southeast, temperatures will climb 5 to 10
degrees above climatic normals Sunday through the middle of next
week.
MARINE... Elevated southeast to south winds to cautionary level
at times away from the coast continue this morning ahead of an
approaching cold front. Winds drop below cautionary levels tonight
as the front drops south into the northeast Gulf of Mexico. Cold
front will slowly settle southward during Thursday...shifting
winds to the north in its wake. Winds in the wake of the front
will approach cautionary levels at times through Friday
night...especially away from the immediate coast.
There is some potential for patchy sea fog tonight...especially
north of Tarpon Springs...however widespread dense sea fog is not
anticipated. A more detailed discussion about sea fog can be found
in the short term section above.
FIRE WEATHER...
Abundant low level moisture will keep relative humidity values
well above critical levels through Thursday. A weak cold front
will bring a chance for a few light showers tonight into Thursday
across mainly the I-4 corridor northward...however rainfall totals
should be on the light side. The front will slip south of the
region later Thursday/Thursday night allowing a cooler and drier
airmass to filter down from the north. Relative humidity values
may briefly drop below 35% across the Nature coast zones Friday
afternoon...however winds are light and ERC values are in the
20s...preventing the potential for red flag conditions.
&&
.Preliminary Point Temps/PoPs...
TPA 82 67 78 60 / 10 20 20 10
FMY 85 67 82 66 / 0 10 10 10
GIF 85 66 83 61 / 10 10 20 10
SRQ 83 67 78 62 / 0 10 20 10
BKV 84 66 77 55 / 10 20 30 10
SPG 79 67 77 63 / 10 10 20 10
&&
.TBW WATCHES/WARNINGS/ADVISORIES...
FL...Beach Hazards Statement through Thursday evening for
Coastal Sarasota.
Gulf waters...None.
&&
$$
AVIATION...69/Close
PREV DISCUSSION...Mroczka & Oglesby
Area Forecast Discussion
National Weather Service Binghamton NY
247 PM EST Wed Nov 30 2016
.SYNOPSIS...
Rain will continue across the region tonight before drying out
during the day Thursday. Temperatures will be cooler Thursday with
a slow downward trend into the weekend. Rain showers will mix with
and change to snow later Friday and eventually become mostly snow
later in the weekend.
&&
.NEAR TERM /THROUGH THURSDAY/...
Main concerns in the near term remain centered around the ongoing
persistent rain over ne PA and se NY this afternoon into the
evening...with a secondary wave of convection expected to develop
over the Lake Erie/PA/NY/OH area early this evening and move east
through central NY/ne PA through the early overnight hours.
Conditions will be cooler and slightly drier on Thursday with
gusty west winds.
A robust supply of deep layer moisture from the south continues to
stream nwd into PA/NY this afternoon and interact with strong large-
scale lift as an upper trough approaches from the west to produce
widespread rain across much of ern PA and sern NY into New England.
This area of rain to the east will continue to slowly drift ewd this
evening...producing an additional 0.5 to 1 inch of rain from the
Poconos to the srn Catskills.
Areas further to the west...including the Finger Lakes...have missed
out once again on the significant rainfall today. However, there
may be another chance this evening and tonight to make up for
that. Latest visible satellite imagery shows some scattering of
clouds over far wrn NY...and the RAP meso-analysis indicates weak
elevated instability and steepening mid level lapse rates around
the Buffalo area. A cold front currently moving through MI/ern OH
will eventually catch up with this area of weak instability and
trigger convection into central NY and portions of n-central PA.
This area of convection will likely combine with the continuous
supply of moisture from the south for widespread rain
showers...and even a few embedded weak thunderstorms through the
evening hours. May see an additional 0.25 to 0.75 inch of rain
tonight over much of cntrl NY.
As the cold front advances ewd late tonight and Thur morning the
deep layer moisture will decrease markedly and mainly leave behind a
layer of low stratus in its wake. Mid level air will continue to
cool slowly through the day Thursday and combine with warm Lakes
Erie and Ontario...and relatively warm near-sfc temps to produce
downwind convective rain showers. 850mb temps around -3 to -5 deg C
will not be cold enough to generate significant precip...and
trajectories will be roughly 260 to 280 deg most of the day which
would tend more toward the Tug Hill area and wrn NY, possibly into
the Finger Lakes.
Temperatures tonight will fall only into the upper 30 to around
40...and have a hard time reaching much above 45 Thursday
afternoon as the cold air funnels in behind the cold front.
Winds will also continue to be a factor tonight with sustained south
winds around 10 to 20 mph this evening...shifting to the west by
Thur morning increasing to 20 mph with gust up to 30 mph Thur
afternoon.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
245 EST Update...
By Thursday night surface winds will become breezy out of the
southwest as the upper lvl low continues to stay parked over
western Quebec with near zonal flow prevailing over the region.
This pattern will continue through the night, advecting cold air
into the region, which will result in lake enhanced/orographic
lift showers over the region. The airmass will remain warm through
midnight. Precip will fall in the form as rain, but after
midnight the atmos should cool down enough that snow growth may be
possible within the higher terrain. The low-lvl mean flow across
the lakes will remain around 280 through 12Z Friday, thus, expect
more so a single band orientation, over the southern Tug Hill
Plateau. During the day on friday expect the mean flow to meander,
and the band the shift southward during the morning hours then
shift northward again early Friday afternoon.
A shortwave is expected to drop south over the region early Friday
evening, which will bring a chance for showers area wide across the
region. This shortwave Friday evening will allow for an even colder
airmass to funnel into the region. Precip type will be highly
dependent on sfc temps. Temps at or above 36 may see rain, while
temps that fall below this mark may see a mix of rain/snow or
completely transition over to snow. This pattern will continue
through Saturday, as CAA will be significant enough for lake effect
showers to continue across the region. Again, precip type will be
highly dependent sfc temp as well as elevation.
Temps will rise into the uppr 30s to low 40s Friday and Sat, and
fall into the low 30s during the overnight periods.
&&
.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
245 PM EST Update...
Little change to the extended forecast. Deep troughing over the
western CONUS is expected from Saturday evening through Wednesday
allowing multiple waves to move across the eastern CONUS creating a
chances for precip over the region for much of the period. Scattered
rain/snow showers will prevail starting Saturday night through mid
week as conditions are favorable. A brief period of high pressure
will build over the northeast during the mid-week but will
quickly diminish as the next system will pushes into the region.
The next system may arrive as early as Tuesday night. Confidence
is low on the timing on the next system, we may be dry for a
couple of days, but confidence increases with pops as we head
towards the weekend.
Temps during the extended forecast will be at or slightly above the
seasonal average.
&&
.AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
Ceilings have improved across the region early this afternoon, but
the next round of widespread rain is moving in from the
south...which will act to lowering ceilings through the afternoon.
IFR to lower-end MVFR restrictions expected initially this evening
with below alt min and LIFR conditions possible tonight.
Towards daybreak (07-11z), a cold front is expected to sweep
through the region. The passage of this boundary will bring an end
to the steadier rain and improvement back to high-end MVFR and VFR
for most terminal sites. Improving from south to north.
Surface winds will vary from SE-SW at 5-10 kt through most of
the period, shifting to W towards daybreak Thursday. Will see a
few gusts out of the west late Thursday morning 15 to 25 kt.
OUTLOOK...
Thursday afternoon and evening...Restrictions possible in
occasional showers, mainly at KSYR and KRME. Other terminal sites
will likely see VFR conditions.
Friday through Monday...Occasional restrictions in scattered
rain/snow showers, especially across central NY terminals.
&&
.BGM WATCHES/WARNINGS/ADVISORIES...
PA...None.
NY...None.
&&
$$
SYNOPSIS...BJT
NEAR TERM...BJT
SHORT TERM...KAH
LONG TERM...KAH
AVIATION...BJT/MLJ
Area Forecast Discussion
National Weather Service Wilmington NC
257 PM EST Wed Nov 30 2016
.SYNOPSIS...
Mild southerly breezes will continue through tonight as a cold
front approaches the Carolinas from the west. The front will
move offshore early Thursday morning. Canadian high pressure
will bring drier and cooler weather Thursday through Saturday.
Areas of low pressure developing along a front will bring clouds
and increasing rain chances the first half of next week.
&&
.NEAR TERM /THROUGH TONIGHT/...
As of 300 PM Wednesday...Strong southwesterly winds aloft
continue ahead of a large upper level-low that is still centered
over the northern Mississippi River valley of Minnesota and
Wisconsin. Water vapor imagery is showing the strong jet
rotating up the southeast side of the low with speed nearing 110
knots at 500 mb over the lower Mississippi River valley.
Most of the showers that formed on the convergence boundary this
morning have shifted off the coast with a scattered showers
developing back to the west over Columbus and Bladen counties. The
showers are expected to be isolated to scattered through the early
evening. The 17 UTC HRRR shows the convective line that is moving
across Georgia at this time will approach the western counties
around 7 PM, and will weaken as it moves across the county warning
area through the night. Also, the 12 UTC NAM, GFS and ECMWF all
show this strong line weakening as it moves across the region. The
chances for significant precipitation in our area are not looking as
good with this model cycle. The models are indicating the chances
of precipitation will extend to just after 12 UTC for southeast
South Carolina but earlier for the areas to the west.
The lows overnight will drop into the middle 50s west of Interstate
95 and lower 60s at the coast.
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
As of 300 PM Wednesday...This period will see the remainder of any
showers exiting the southeast North Carolina coast with high
pressure building in behind the cold front. This high pressure is
expected to continue through Friday night.
High temperatures are expect to only be in the upper 60s on Thursday
and with cold air advection behind the cold front highs on Friday
will only be around 60. Low temperatures on Thursday night will fall
into the upper 30s well inland to the lower to middle 40s at the
immediate coast line. On Friday night temperatures will drop into
the middle 30s well inland and 40 to 42 at the beaches.
&&
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
As of 300 PM Wednesday...A deep cutoff upper low across the
Baja peninsula will eject out into the southern stream flow
early next week, bringing rain chances to the Carolinas. However
the timing of this remains uncertain owing to extremely large
model differences between the slower GFS and faster ECMWF.
Forecasters at WPC have access to a great deal of data we don`t
at the local NWS level, and noted in their extended discussion
that the ECMWF ensembles resemble the GFS operational run and
its ensembles much more than they do the ECMWF operational run.
For this reason, we favor a GFS-centric forecast for the
extended period.
Surface high pressure and a low-amplitude upper level ridge
should keep Saturday dry. However by Sunday moisture should
begin increasing in advance of the big upper system ejecting out
of Mexico. While even the fast GFS doesn`t bring the trough to
our longitude until Tuesday, increasing flow of Gulf moisture in
the mid-levels should bring clouds and perhaps a little light
rain to the area Sunday afternoon or Sunday night. Rain chances
then develop again on Tuesday when I`ve increased rain chances
to 40-50 percent.
A northern stream trough which is shown in both the GFS and
ECMWF should roll east out of the Rockies during the middle of
next week and could begin to spread another risk of rain into
the area by late Wednesday.
&&
.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
As of 18Z...Area will remain in warm and moist air mass ahead of
cold front through this evening. Persistent fog along the coastal
terminals has broken up for the most part leaving IFR ceilings with
low stratus. Expect gusty southerly winds with some drier air mixing
down to produce mainly SCT to BKN lower ceilings through this
evening. A cold front will track across the TAF sites from west to
east overnight. This should produce a line of showers with gusty SW
to W winds. Have not included thunderstorms in TAFs due to timing of
frontal passing, but expect rapidly moving showers with some heavier
rain and stronger winds possible just ahead and along front from 02-
06z inland and 05-10z along the coast. Post fropa expect some brief
MVFR/IFR fog possible then showing trend of clearing with westerly
winds behind front up through end of TAF period.
Extended outlook...Expect VFR. Expect clouds and pcp back in
forecast by end of period with some MVFR/IFR conditions possible by
Monday.
&&
.MARINE...
NEAR TERM /THROUGH TONIGHT/...
As of 300 PM Wednesday...South winds of around 20 knots are
occurring over the waters this afternoon well ahead of cold
front that is located just west of Georgia to southern
Mississippi. As the front moves closer to the coastal waters the
winds will become southwest and increase to 20 to 25 knots with
higher gust. Seas are running between 4 and 6 feet from 20
miles offshore to the coast. Seas are expected to increase to 5
to 7 feet overnight. A small craft advisory will continue for
all the water through the night.
SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
As of 300 PM Wednesday...At sunrise the cold front will be
approaching the coastal waters and will move across the waters
during the morning. As the winds direction shifts behind the cold
front they will weaken, and the seas will diminish below small craft
conditions south of Little River around 7 AM and 10 AM north of
Little River.
By Thursday evening, the winds will shift from the west to the
northwest by Thursday evening, and remain north to northwest through
Friday night. Winds will relax to 10 knots by Friday and seas will
settle out around 2 to 3 feet during this time frame.
LONG TERM /SATURDAY THROUGH SUNDAY/...
As of 300 PM Wednesday...Canadian high pressure over the Mid-
Mississippi Valley will build east into the Carolinas early
Sunday, weakening slightly as the centers sits across the
interior of both states Sunday night. Moderate offshore breezes
Saturday should gradually die down Saturday night, but may get
reenergized Sunday night as a wave of low pressure begins to
take shape along the Georgia coast late.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...None.
MARINE...Small Craft Advisory until 7 AM EST Thursday for AMZ254-256.
Small Craft Advisory until 10 AM EST Thursday for AMZ250-252.
&&
$$
SYNOPSIS...TRA
NEAR TERM...DRH
SHORT TERM...DRH
LONG TERM...TRA
AVIATION...DRH
Area Forecast Discussion
National Weather Service Marquette MI
418 PM EST Wed Nov 30 2016
.SHORT TERM...(This evening through Thursday)
Issued at 417 PM EST WED NOV 30 2016
WV imagery and RAP analysis indicated a mid/upper level low over
northeast IA with troughing to the northeast through wrn Lake
Superior to James Bay. At the surface, a trough extended from wrn WI
to a developing low over se Lake Superior resulting in light winds
over most of Upper Michigan but increasing n to ne winds over west
and central Lake Superior. An area of pcpn (rain mixed with sleet)
that has lifted through n cntrl Upper Michigan into Lake Superior
and the Keweenaw was supported by 900-700 mb fgen and 285 isentropic
lift. Light lake enhanced pcpn has also slid into IWD as the low
level nrly flow edges eastward.
Tonight, expect the lake enhanced pcpn, rain changing to snow, to
expand over the wrn cwa for locations favored by nrly flow. Even
with only marginal instability (850/700 mb temps of -6C/-12C over 6C
lake surface) abundant upstream and deeper moisture along with
upslope flow will support snowfall amounts to around 2 inches. Wet-
bulb zero heights suggest that any pcpn developing over the east
half will be mainly rain.
Thursday, as the mid level low consolidates south of James Bay, the
sfc trough/low will also slide into Quebec, low level winds will
back to the southwest. Additional snowfall amounts to around 2
inches will be possible over mainly the Keweenaw and the Huron
Mountains(w of Big Bay to Herman). CAA will change the remaining
pcpn to snow over the east.
&&
.LONG TERM...(Thursday night through Wednesday)
Issued at 255 PM EST WED NOV 30 2016
During the beginning of the medium range period, a slowly weakening
cyc nw flow arnd a slowly departing closed lo in Quebec wl cause
some lk effect pcpn into Sat. Although a passing hi pres rdg wl
bring mainly dry wx for Sat into Sun, another shrtwv/lo pres trof
aprchg fm the w wl bring a return of some pcpn later on Sun. Expect
dry wx on Mon as the trailing hi pres rdg overspreads the area.
While the fcst wl include some pops much of the time during the
medium range, pcpn and any snow totals should be on the lgt side. A
more important lo pres lifting out of the wrn trof and toward the
wrn Great Lks next Tue/Wed may result in a more sngft pcpn event
then, but model differences on the fcst are too sgnft to pin down
any details attm. Overall temps into early next week wl run aoa
normal.
Thu ngt thru Fri ngt...Although the larger scale forcing to support
pcpn wl be waning as the closed lo over wrn Quebec at 00Z on Fri
weakens and drifts slowly to the e, leaving deep lyr qvector dvgc/
subsidence over the Upr Lks, a persistent albeit weakening cyc nw
flow in the presence of plentiful llvl mstr and h85 temps within a
few degrees of -6C /compared to Lk Sup water temps in the 7-8C
range/ wl support continued lk effect pcpn. This pcpn wl be in the
form of mainly snow over the interior w half, with more of a
rain/snow mix near the warming influence of the lakes. Bumped up
pops above the consensus fcst and into the likely range in the
upslope areas favored by the expected llvl flow. The incrsgly
negative larger scale dynamics...marginally chilly h85 temps...warm
ground temps and absence of a deep dgz sug snow accums wl be a few
inches at most thru this time even over the hier terrain of the w
half.
Sat/Sat ngt...Although a sfc hi pres rdg/acyc larger scale llvl flow
extending fm Ontario into the wrn Great Lks wl drift acrs Upr MI on
Sat, many of the models depict some lgt pcpn lingering along a lk
induced lo pres trof and under some persistent llvl mstr. On Sat
ngt, the llvl flow wl shift to the s after the hi pres rdg axis
moves to the e, ending any lingering pcpn except over Lk Sup and the
ern cwa downwind of Lk MI. Any snow accums during this time wl be
under an inch.
Sun/Sun ngt...Another shrtwv/lo pres trof embedded in the more zonal
flow alf is progged to impact the area during this time. Waa/hgt
falls/uvv ahead of this disturbance wl result in some pcpn arriving
w to e on Sun. Fcst llvl thermal fields sug the pcpn wl be a rain/
snow mix, with the ptype primarily snow over the interior w half.
But since mstr inflow is progged to be marginal and the shrtwv/lo
pres trof are progged to weaken with a larger scale tendency toward
a bldg upr rdg in the Plains, expect only lgt snow accums. The sly
flow ahead of the lo pres trof off Lk MI in the presence of h85
temps still arnd -6C may result in some lk enhancement of the mixed
pcpn there. The arrival of dnva/large scale subsidence in the wake
of the passing disturbance and ahead of upr rdg/sfc hi pres in the
Plains wl cause the pcpn to diminish w-e on Sun ngt. Since h85 temps
within the trailing airmass are progged to rise toward -4C by 12Z
Mon, no lk effect pcpn is expected in the wake of the passing/
weakening trof.
Mon thru Wed...Bldg upr rdg/sfc hi pres are fcst to drift into the
wrn Great Lks on Mon, resulting in dry wx and some warmer temps as
h85 temps rebound to near 2C. Expect a return of some pops on Tue as
some waa btwn the departing sfc hi pres rdg and a shrtwv/lo pres
moving newd out of a deep wrn trof overspreads the area. The longer
range models show some sgnft differences in the evolution/track of
the sfc lo pres for next Wed that would support either rain or a
surge of colder air and some lk effect snow showers. Considering the
sgnft uncertainties, made no changes to the consensus fcst.
&&
.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1255 PM EST WED NOV 30 2016
Conditions will begin deteriorate at IWD and CMX with increasing
rain and snow showers this afternon and evening as low pressure
moves through Upper Michigan. The more concentrated area of rain and
snow showers over the west will change over to mainly snow. VFR to
MVFR conditions will give way to MVFR to IFR conditions in the
afternoon through the overnight hours at IWD and CMX. Visibility may
also drop into the IFR range with the snow. SAW will stay VFR to MVFR
through the rest of the day and drop to MVFR tonight into Thursday
morning with minimal chances of reduced visibility as the
precipitation should remain in the form of rain into the late
afternoon hours.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 417 PM EST WED NOV 30 2016
Low pressure will linger over the western Great Lakes through
Thursday. However the pressure gradient is not expected to be as
tight with remaining below 25 knots. Northerly winds to near 30
knots are expected to develop tonight into Thursday as the slow
moving trough moves to the east of Lake Superior into Quebec. High
pressure will then build into the area into Saturday with winds
below 20 knots.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...JLB
LONG TERM...KC
AVIATION...JLB
MARINE...JLB
Area Forecast Discussion
National Weather Service New York NY
310 PM EST Wed Nov 30 2016
.SYNOPSIS...
A frontal system will move across the area tonight followed
by high pressure Thursday. A series of weak cold troughs will
pass through the region late week into the beginning of the
weekend. High pressure briefly builds in Saturday night into
Sunday...then a low pressure system may impact the area Sunday
night into Monday.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Models remain in good agreement with handling of complex surface
features tonight. Aloft, closed low moves slowly east tonight across
the Great Lakes region, with shortwave energy pivoting around the
low, traversing across the northeast, steering these surface
features.
Speaking of the surface features, a warm front just to the south
will approach, and track very close to Long Island, NYC metro. Low
pressure moves east, just north of NY state as triple point low
likely passes across our NW zones into New England after
midnight. A cold front passes from west to east after midnight
as well.
Through the evening, looks like period of rain and drizzle will
prevail, and cannot rule out a rumble or two of thunder as weak
instability and available Pot energy aloft clips southern half of
the area. Plenty of lift aloft in WAA will result in good coverage
of rain, likely becoming more convective in nature as the triple
point low and front approach.
Expect showers, possible thunder, although latest HRRR backing off
on potential line of convection ahead of the front, to move across
the area after midnight. Winds will be a challenge, but easterly
flow turns toward the southeast, then west/southwest overnight.
Interior locations may back to the NW as they stay on the cool
side of the warm front.
With plenty of clouds, moisture and rain, temperatures will hold
steady or fall slightly tonight, possibly falling a few additional
degrees late as the showers end, and winds turn to the west.
Through the evening, fog is possible ahead of the warm front,
although may be more of a stratus event, except east of NYC metro.
where winds are lighter, could see patchy dense fog prior to the
cold front.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
Dry weather returns this time frame as upper low remains well to the
north, and two surface lows will be located well to the north as
well. Secondary low, that initially moves nearby as triple point low
near the coast intensifies as it tracks toward the Canadian
Maritimes. Fairly tight w/nw pressure gradient remains in place
behind this system as high pressure builds well to the west.
CAA is noted, but downslope flow and a lag in the cold air allows
for above normal readings during the day per mos and model blend.
Winds persist thursday night, which should preclude radiational
cooling from occurring.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Forecast models in good agreement to end the week and start the
weekend, with troughing over the region as a closed low north
of the region lifts into southern Ontario/Quebec.
Expect generally dry...cool...and breezy conditions Friday thru Sat
in persistent deep WNW flow. A couple of weak shortwaves/surface
troughs moving through the region may trigger some isolated
sprinkles (and/or flurries nw of NYC) Fri afternoon through Sat.
Conditions remain generally quiet with seasonable conditions heading
into Sunday as high pressure builds over the region.
There are significant differences in models Sunday night and Monday
with the handling of the late weekend/early next week eastward
evolution of a deep Western US trough. The main difference is
whether the base of the trough closing off into Northern Mexico this
weekend...travels with the parent northern stream shortwave or gets
left behind. The implication being...a phased eastward moving trough
would bring potential for a southern low and significant precip
tracking up the east coast for Sun Night into early next week.
Meanwhile...the latter detached scenario would just bring another
weak trough through the region with perhaps some light precip.
Either scenario is in play. Based on the complex interaction...may
continue to see flip-flop of operation models and considerable
spread in ensembles for this time frame for the next few days. As a
result, this portion of the forecast will remain unchanged and with
low chance POPs in the forecast.
Dry weather is expected on Tuesday, with another low chance for
rain on Wednesday as another weak low approaches.
&&
.AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
A warm front moves through early this evening, followed by a cold
front late tonight. Flight category forecasts will vary widely among
all area terminals as the warm front passes through the region.
Mainly IFR and possible LIFR is expected this evening and overnight.
Areas of rain and drizzle will persist ahead of the cold front.
While confidence remains low...isolated thunder is still possible
right ahead and along the cold front overnight after 04z.
E winds ahead of the warm front will shift to the SE-SW early this
evening as the front moves north. S-SW gusts to 25 KT likely
tonight. Stronger gusts possible in any convective showers overnight
as a low level jet passes through. Low level wind shear likely for
JFK/LGA and points east starting this evening.
NY Metro Enhanced Aviation Weather Support...
Detailed information, including hourly TAF wind component forecasts,
can be found at: http:/www.weather.gov/zny/n90
KJFK TAF Comments: IFR expected until 08z but amendments likely due
to variability and timing of frontal passages. Wind gusts forecast
may be off by 1 or 2 hours.
KLGA TAF Comments: IFR expected until 08z but amendments likely due
to variability and timing of frontal passages. Wind gusts forecast
may be off by 1 or 2 hours.
KEWR TAF Comments: IFR expected until 08z but amendments likely due
to variability and timing of frontal passages. Wind gusts forecast
may be off by 1 or 2 hours.
KTEB TAF Comments: IFR expected until 08z but amendments likely due
to variability and timing of frontal passages. Wind gusts forecast
may be off by 1 or 2 hours.
KHPN TAF Comments: IFR expected until 08z but amendments likely due
to variability and timing of frontal passages. Wind gusts forecast
may be off by 1 or 2 hours.
KISP TAF Comments: IFR expected until 09z but amendments likely due
to variability and timing of frontal passages. Wind gusts forecast
may be off by 1 or 2 hours.
.OUTLOOK FOR 20Z THURSDAY THROUGH MONDAY...
.Thursday...VFR. West gusts 20-25 KT.
.Friday...VFR. West gusts around 20 KT.
.Saturday...VFR. NW gusts 20-25 KT.
.Sunday...VFR.
.Monday...VFR...possibly lower depending on the track of low
pressure to the south.
&&
.MARINE...
Patchy to areas of fog will likely form into this evening as a warm
front approaches. High dew point air advecting northward over mid 50
degree water should allow this fog to form. Extent of the fog
remains in question however, and increase winds may hinder this
development.
Easterly winds increase ahead of a warm front early tonight, then
diminish as the front draws near. SCA remain in effect for the ocean
waters, but will include the Long Island Sound and Peconic and
Gardiners Bays as east flow picks up to 20 to 25 kt before
diminishing.
Winds will shift around to the west after midnight as a cold front
moves through. Expect these westerly winds to increase, and SCA
conditions are anticipated across all waters Thursday afternoon
through Thursday night. Winds over the ocean waters remain elevated
per wave watch III and nearshore wave prediction system.
SCA conditions for sea and wind gusts will remain likely on the
ocean waters through Saturday in a tight gradient between Canadian
Maritimes low and Central/Southern US high. On the non-ocean waters,
marginal sca gusts possible during this period...particularly on LI
sound.
With high pressure building back into the region Sat Night into
Sun...a return to sub-sca conditions would be expected. The sub-SCA
conditions are expected into early next week.
&&
.HYDROLOGY...
An additional half inch to 1.5 inches is expected through tonight.
Heaviest amounts are expected to occur across extreme northern New
Jersey, and the lower Hudson valley of New York.
The main threat is urban and poor drainage flooding, with a low prob
of flash flash flooding with any training convection. In addition,
quick responding streams, such as the Rahway at Springfield and the
Hohokus Brook, could approach or just barely exceed bank full. The
overall flood potential is not widespread enough to warrant a flood
watch.
No significant precipitation expected Midweek through Sunday.
Potential for significant precip returns Sunday night into
Monday...but low predictability at this point.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory from 6 AM Thursday to 6 AM EST Friday for
ANZ338-345.
Small Craft Advisory until 6 AM EST Friday for ANZ330-335-340-
350-353-355.
&&
$$
SYNOPSIS...BC/PW
NEAR TERM...PW
SHORT TERM...PW
LONG TERM...BC
AVIATION...IRD
MARINE...BC/PW
HYDROLOGY...BC/PW