Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/06/17
Area Forecast Discussion
National Weather Service La Crosse WI
506 PM CST Sun Nov 5 2017
.SHORT TERM...(This evening through Monday night)
Issued at 212 PM CST Sun Nov 5 2017
20Z surface analysis shows a cold front has moved across the
forecast area and into central WI. Remaining showers from earlier
have also moved out of the area. Temperatures will fall through
the rest of the afternoon into the evening with breezy northwest
winds.
Primary forecast challenge for the rest of the night will
be cloud trends. Unfortunately, model derived synthetic satellite
imagery is no help as it shows most of MN into the Dakotas should
already be clear whereas these areas are still covered in low
stratus. 0.5 km RAP RH fields are much more pessimistic, with
clouds hanging tough through the evening and then finally starting
to break up overnight. Will follow this scenario given current
observational trends, but additional adjustments are likely.
Clouds or lack thereof will have a huge impact on temperatures
tonight. Most areas will drop into the 20s, but if prolonged
clearing does materialize, low 20s and possibly even some teens
are possible in favored cold spots.
Despite surface high pressure building across the forecast area
Monday, expect increasing mid-high clouds ahead of the next wave
aloft. High temperatures will only top out in the mid 30s to near
40 degrees with a light north wind. Still watching the potential
for some light snow mainly across Clark/Taylor counties Monday
night as an area of enhanced mid-level frontogenesis streaks
across the area with a quick moving 500 hPa short-wave. That said,
exact placement of this forcing and degree of moisture is still
somewhat in question, so confidence in seeing accumulating snow is
rather low.
.LONG TERM...(Tuesday through Sunday)
Issued at 212 PM CST Sun Nov 5 2017
Outside of a dry cold frontal passage Wednesday night into
Thursday, the rest of the week looks quiet with surface high
pressure dominating the regional weather pattern. In addition,
broad troughing aloft will keep the area on the cool side with
daily highs mainly in the 30s. Nighttime lows will depend on
clouds, but each night is likely to drop at least into the 20s.
Teens are not out of the question, however, especially Tuesday
night when clear skies are expected.
For Friday into the weekend, the 12Z operational GFS has moved
toward the colder ECMWF solution. That said, ensembles of
temperature from from both models vary widely, so forecast
confidence is low. A model consensus keeps highs mainly in the mid
30s to low 40s with lows in the 20s. The next best chance for
precipitation will be Saturday into Sunday as an Eastern Pacific
short-wave drops south from Canada and across the Upper Midwest.
The GFS is much more robust with its QPF compared to the drier
ECMWF/GEM, and given the temperature considerations above, it`s
far too early to provide much detail.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 506 PM CST Sun Nov 5 2017
MVFR stratus will become scattered after midnight tonight,
expected in the 6-8Z timeframe at KRST and in the 10-12Z timeframe
at KLSE. VFR conditions are then expected the rest of the TAF
period. Plan on an increase in mid level clouds through the day on
Monday with cloud bases around 10kft.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...Rogers
LONG TERM...Rogers
AVIATION...Wetenkamp
Area Forecast Discussion
National Weather Service Cheyenne WY
418 PM MST Sun Nov 5 2017
.SHORT TERM...(This evening through Monday)
Issued at 140 PM MST Sun Nov 5 2017
Surface front has been wobbling back and forth over the Wyoming
plains today. Currently this front is seen on surface analysis
stretching roughly from Pine Bluffs to just west of Casper. Most
precipitation has remained south of the area today with the
exception being the mountains and adjacent foothill areas such as
Arlington where light snow has been reported most of the day. The
mountains have continued to pick up some impressive snowfall
totals according to SNOTEL reports with as much as 25 inches over
the higher elevations of the aptly named Snowy Range. While snow
was accumulating near Arlington, road and surface temps were
marginal and there have been little in the way of travel impacts
so elected to keep them out of an advisory at this time.
As the southern stream jet over CO shifts a bit further north
tonight, weak isentropic upglide will develop over the shallow
cold airmass over the plains. Expect light precipitation to
redevelop over eastern WY this evening and spread into the
Panhandle into the overnight hours. Surface temps have warmed into
the upper 30s this afternoon but dewpoints remain in the mid 20s
over the Panhandle. Could see rain mix with snow or even some
freezing rain for a time late tonight with the best chance for
freezing precip being area from Alliance to Chadron. Amounts
should be light so think impacts will be minimal as temperatures
will be marginal at or just below freezing. Moist westerly flow
aloft and some weak mid level frontogenesis will keep snow going
over the mountains tonight with additional 4 inches or so of
accumulation likely .
For Monday through Tuesday, attention turns to the mid level vort
max now seen on WV imagery over WA. This feature will sag slowly
southeast and be located over NW WY by Monday night. A strong
reinforcing cold front will drop rapidly south over the plains
Monday afternoon and stall over CO by Monday night. A deepening
cold airmass and developing westerly overrunning will set the
stage for a period of accumulating snowfall along and east of the
Laramie Range with the heaviest amounts falling along the I-80
corridor from the summit to the Cheyenne area and east to Kimball.
While nothing looks particularly heavy, a period of light to
moderate snow lasting around 12 hrs should be enough to produce
amounts in the 4 to 6 inch range with locally heavier amounts.
Elected to hold off on a watch for now as widespread 6 inch
amounts do not look likely at this time. One concerning factor is
the persistent band of low to mid level frontogenesis that
appears to set up for most of Monday night along the CO/WY/NE
border on the NAM. Should this materialize, a period of heavier
snowfall may be possible. Winter headlines will likely be needed
by Monday morning for this system as amounts come into better
focus.
.LONG TERM...(Monday night through Sunday)
Issued at 140 PM MST Sun Nov 5 2017
Shortwave ridging will build over the Rockies on Wednesday leading
to a warming trend for the mid week time frame. Models disagree
with the evolution of the next trough forecast to move into the
Pacific NW on Thursday with the GFS being more aggressive in
breaking down the ridging and driving a strong cold front through
the area on Saturday while the EC dampens the system and keeps it
to our north. Overall should see a trend more towards some
unsettled weather as we get towards the weekend with perhaps some
mountain snow by Saturday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 402 PM MST Sun Nov 5 2017
Low confidence forecast for the 00Z TAF package this afternoon.
Latest HRRR guidance not doing to well representing current
conditions. Did bring down ceilings at KCYS as winds shift a
little more southeast this evening. There will be a lift in
conditions as winds shift more westerly towards 06Z. Will continue
to monitor and update TAFs as needed.
&&
.FIRE WEATHER...
Issued at 140 PM MST Sun Nov 5 2017
Cool temperatures and recent precipitation should preclude much in
the way of fire weather concerns through early this week. Dry and
slightly warmer conditions will return by mid week.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Storm Warning until 5 PM MST Monday for WYZ112-114.
NE...None.
&&
$$
SHORT TERM...DEL
LONG TERM...DEL
AVIATION...GCC
FIRE WEATHER...DEL
Area Forecast Discussion
National Weather Service Quad Cities IA IL
616 PM CST Sun Nov 5 2017
...AVIATION UPDATE...
.SYNOPSIS...
Issued at 221 PM CST Sun Nov 5 2017
The main cold front extended from southern lower MI southwest across
northern IN into central IL and eastern MO this afternoon. Showers
and thunderstorms were widespread along this axis, while further
north, the back edge of a narrow SW to NW band of rain over northern
IL was about to exit McDonough county. The rest of the forecast area
was blanketed by cloud cover. Increasing northwest winds were
bringing a reinforcement of cold air advection, with temperatures
ranging from around 40 northwest to lower 50s in pockets that had
seen some brief thin spots in the overcast earlier this afternoon.
Cold high pressure centered over the Dakotas, where midday
temperatures were in the only 20s, will continue to settle eastward
tonight into Monday, supplying a seasonably cold airmass over the
forecast area.
&&
.SHORT TERM...(This Evening through Monday)
ISSUED AT 221 PM CST Sun Nov 5 2017
Main challenges center around cloud cover and temperatures. Visible
satellite animations this afternoon showed a back edge to one layer
of low clouds over northern and western IA, with a more diurnal-
looking stratocu layer on its heels spilling south out of MN.
Continued diurnal erosion of this latter deck should lead to at
least partial clearing over the western and northwest half of the
forecast area this evening. This will be followed by advancing mid
and high clouds seen over NEB linked to the next mid level impulse
in the zonal flow aloft. The net result will be partly to mostly
cloudy skies this evening, then mostly cloudy late tonight into
Monday when additional mid level impulses and moisture progress over
the area. Even with questionable cloud cover, continued cold air
advection will advance temperatures currently in the 20s over
southern MN southeast into at least the northern half of the
forecast area by morning, while the south may hold in the lower 30s.
Monday, limited sunshine and north to northeast surface winds will
result in another day of below normal temperatures. Stayed close to
forecast model blend highs which looked reasonable holding
highs from around 40 north to the mid 40s in the far south.
.LONG TERM...(Monday Night through Sunday)
ISSUED AT 221 PM CST Sun Nov 5 2017
Below normal temperatures through the week with considerable
uncertainty next weekend.
Quiet, dry, and cool conditions will be seen Monday night through
Wednesday with the storm tracks well north and south of the area.
Wednesday night on...
The quiet, dry, and cool conditions will continue Wednesday night
through Friday. A cold front will move through the area Wednesday
night/Thursday but forcing is weak to non-existent with very limited
moisture. Attention then turns to next weekend.
As mentioned earlier there is considerable uncertainty as to what
will happen next weekend. The flow aloft is fast and near-zonal
across much of the northern hemisphere. This situation results in
below average model performance as the models have trouble with the
movement of storm systems. The global models are showing this with
very poor run-to-run continuity and shifting the potential storm
track by several hundred miles with each run.
Based on Dprog/dt of the individual global models, there seems to be
an agreement developing that Friday night will be mainly dry. This
trend looks reasonable as all models show high pressure from the
Great Lakes to the Gulf Coast through mid-day Friday.
Starting Saturday, the disagreements between the global models
increase. The ECMWF keeps the area dry Saturday with the system
arriving Saturday night into Sunday. The GFS has the system arriving
Saturday afternoon and continuing into Sunday. The CMC global has
the system moving through the area Saturday and Saturday night.
Right now the model consensus has chance pops Saturday, likely pops
Saturday night, and slight chance to chance pops on Sunday. The
possibility does exist that a part or much of Saturday could be dry.
Where the storm tracks will be important for precipitation type. The
CMC global shifted the system north by 500 miles with the 00z/05 run
resulting in a ptype of mainly rain. The 12z/05 CMC global run
shifted the system 400 miles south yielding a ptype of mainly snow.
The GFS has gone from a storm with mainly rain, 00z/05 run; to a
storm with mainly snow, 06z/05 run; to the 12z/05 run of a storm
with ptype being mainly rain or perhaps a rain/snow mix. The ECMWF
runs has shown somewhat less variability from run to run with a
ptype of rain or a rain/snow mix.
Initially, there will be plenty of dry, cool air over the area. Thus
the atmosphere will saturate from the top down. When this occurs,
the overall atmospheric column cools. Thus the precipitation may
start out as rain and quickly go to a mix or all snow during the
night before going back to a mix or all rain again.
Given the current timing differences with the global models, the
model consensus has snow Saturday morning that goes to all rain in
the afternoon. A rain/snow mix going to potentially all snow
Saturday night before going back to a mix and then all rain on
Sunday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday Evening)
ISSUED AT 605 PM CST Sun Nov 5 2017
Confidence in overnight cloud trends remains low. Have kept MVFR
ceilings around into the early morning hours at all sites but KCID
and will re-evaluate through the evening. The RAP 925mb RH prog
seems to be modeling the current clouds well and delays clearing
until after 10z Monday. Mid level clouds will then be on the
increase overnight into Monday morning.
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
SYNOPSIS...Sheets
SHORT TERM...Sheets
LONG TERM...08
AVIATION...RP Kinney
Area Forecast Discussion
National Weather Service Peachtree City GA
944 PM EST Sun Nov 5 2017
.UPDATE...
High pressure ridge still entrenched across the CWFA this evening.
Main forecast issue will be when/if the low level cloudiness will
overspread the area. Stratus deck is noted across SC/W NC and is
slowly spreading SW. Do think areas in the NE will have the best
chances for widespread low level stratus. Total coverage will
depend upon when a wind shift to the SW will occur. The hi-res
models are not in good agreement as to when this wind shift will
occur...the RAP is a lot sooner than the HRRR. If the wind shift
occurs earlier than anticipated, then stratus/fog coverage will be
a lot less in the metro ATL area.
&&
.PREV DISCUSSION... /Issued 641 PM EST Sun Nov 5 2017/
PREV DISCUSSION... /Issued 241 PM EST Sun Nov 5 2017/
SHORT TERM /Today through Monday Night/... No major concerns in
the short term period. 12Z model guidance in very good agreement
with little change from previous runs. Max temps today and monday
will continue near record values (see CLIMATE section below).
Widespread fog with patchy dense fog again likely tonight. Will
likely issue at least Special Wx Statement later tonight.
Thunderstorms likely to develop north of the state late tonight
but as convective remnants weaken a few showers could drift into
the far northern areas after 3am Monday with clouds and isolated
showers lingering thru midday. Repeat scenario likely early
Tuesday morning as overnight convection drifts into far northern
GA again. Severe storms unlikely either night but instability and
vertical wind shear a little more favorable Monday night.
SNELSON
LONG TERM /Tuesday through Saturday/... The extended forecast
begins with temperatures well above average on Tuesday with a cold
front slowly working its way southward by midweek. Rain chances
will increase notably by Wednesday in association with the
incoming cold front and upper energy. Rain also will linger longer
through Thursday than earlier indicated as a strong upper system
passes through the area, so PoPs were raised into the likely range
through the day Thursday. Drier air finally will work into the
area by Friday into Saturday. Please refer to the previous long-
term forecast below for further detail.
RW
PREV LONG TERM DISCUSSION...
/Issued 409 AM EST Sun Nov 5 2017/
LONG TERM /Monday Night through Saturday/...
Long range period begins with front remaining just north of
forecast area into Tuesday. The surface front will start to move
slowly through the area on Wednesday as a shortwave drops across
the southern plains. By Thursday, the short wave moves across the
Gulf Coast States and models in agreement moving the front south
and east although there are some discrepancies, GFS shows a weaker
shortwave and more progressive with the surface feature.. Models
hold differences as high pressure builds into New England for
next weekend. GFS brining upper level wave further south,
increasing clouds on Saturday, but overall should end the week
with drier and cooler conditions.
Temperatures will continue to run warmer than normal until the
front brings cooler air across the area starting on Wednesday.
Thursday will bring an even more noticeable difference and
although temperatures start to moderate on Friday guidance still
advertising just below normal for this time of year.
Atwell
CLIMATE...
Records for 11-05
Max Temperature Min Temperature
Station High Low High Low
------- ---------- ---------- ---------- ----------
KAHN 82 2003 47 1995 68 2003 29 1967
KATL 82 1948 45 1995 68 2003 26 1991
KCSG 85 1946 50 1995 70 2003 26 1952
1909
KMCN 86 2003 47 1995 68 1948 24 1991
1959
Records for 11-06
Max Temperature Min Temperature
Station High Low High Low
------- ---------- ---------- ---------- ----------
KAHN 82 2003 47 1951 66 2003 26 1962
1948 1884
KATL 78 1994 46 1967 66 2015 24 1976
1986 2003
1938
KCSG 86 1909 52 1967 70 2003 27 1976
KMCN 85 2003 51 1967 68 2015 26 1991
2003 1976
AVIATION...
00Z Update...
Main forecast issue for the TAF period will be the potential for
IFR/LIFR cigs. No change in airmass from last night and do expect
abundant moisture in the lowest levels. However, the one thing
that may be different is that the winds are expected to go over to
the SW side around 12Z. If the winds go to the SW side a little
earlier than anticipated, then LIFR/IFR cigs may be more sct than
bkn. Regardless, due to the SW winds, cigs should improve a bit
faster during the mid to late morning than they did today.
//ATL Confidence...00Z Update...
Low to med confidence on cigs. Otherwise, med to high confidence
remaining elements.
&&
.PRELIMINARY POINT TEMPS/POPS...
Athens 58 79 61 78 / 10 5 10 30
Atlanta 60 78 62 77 / 10 5 10 30
Blairsville 56 70 56 70 / 10 20 30 60
Cartersville 59 76 62 75 / 10 20 20 40
Columbus 60 83 62 81 / 5 0 5 10
Gainesville 58 75 61 74 / 10 10 20 40
Macon 58 83 60 82 / 5 0 5 10
Rome 60 76 62 75 / 10 20 30 50
Peachtree City 57 80 60 78 / 10 5 10 20
Vidalia 60 84 61 84 / 5 0 0 5
&&
.FFC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
439 PM MST Sun Nov 5 2017
.SHORT TERM...(Tonight through Monday night)
Issued at 320 PM MST Sun Nov 5 2017
Going into this storm, the big question was temperatures and how
far south they would reach. The polar front jet remains to our
north where the cold front remains while the subtropical jet is
over our CWA. West to southwesterly flow continues to keep
temperatures very warm especially for our central mountains. Local
reports, webcams, and observations show very little in the way of
any snow accumulation for that area over the past 24 hours. The
NAM and GFS continue to paint some preciptation through Monday
morning while the RAP and HRRR show almost no precipitation. As
those models are doing pretty well with the current scenario, see
no reason to doubt them over the next 12 to 24 hours. With that,
and after a quick discussion with Pueblo, went ahead and
cancelled the advisories for the central mountains. Will they get
more snow? Believe they will, but nothing that will cause much in
the way of impacts. The northern mountains, on the other hand, are
doing quite well with the Tower SNOTEL reporting over 20 inches
while webcams in the mountains of Steamboat Springs show almost 8
inches. More snow is expected as temperatures in that region are
hovering around freezing and cross sections show more available
moisture. For the remainder of today, the central and southern
valleys will remain dry, maybe an odd sprinkle here or there,
while the northern valleys have better chances for precipitation.
The northern mountains will continue snowing, with occasional
breaks, the central mountains will see some off and on snow as
well while the San Juans remain mostly dry except right around
Wolf Creek Pass which may see more pronounced snowfall thanks to
favorable orographics.
Monday, more of the same as southwesterly flow continues. The NAM
and GFS start picking up more precip for the southern and central
mountains Monday morning through about 3PM and should be watched. As
mentioned above, the HRRR and RAP do show some very light precip
but nothing as widespread or intense as the NAM or GFS. Even so,
later shifts should keep an eye on short range models to see if
they start following suit. Areas west of the mountains will see a
day very similar to today...some clouds, some gusty winds, and a
few sprinkles.
.LONG TERM...(Tuesday through Sunday)
Issued at 320 PM MST Sun Nov 5 2017
By Tuesday, the cold front finally starts moving into our area.
This, thanks to the upper level trough that`s supporting the
surface cold front. As this starts to occur, the subtropical jet
will be elongated from well off the Pacific, streaming overhead,
and reaching as far east as the Tennessee Valley. This means that
available moisture should increase and precipitable water does
show a marginal increase down south. This matches up with
precipitation increasing for areas south of I-70 Tuesday afternoon
and then increasing as the cold front pushes southward. This rain
and snow looks to continue through daybreak Wednesday morning.
Some banding may set up which may allow some heavier snowfall to
occur. Will have to see how later model runs handle this
development.
The remainder of the long-term period brings some ridging and then
more zonal flow for the area. Little precipitation is expected
while temperatures should run near normal Tuesday and Wednesday
before creeping upwards for the rest of the week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 439 PM MST Sun Nov 5 2017
Bands of cumulus and showers continue to stream over the region
late today. Shower intensity and coverage dimishing toward sunset
and don`t expect much of an impact from them at TAF sites
overnight. KASE and KEGE will have them in the vicinity. Gusty
southwest winds will drop off for most places, but won`t be
surprised to see occasional mixing overnight at higher sites. Kept
a period of LLWS in for KASE to account for stronger winds blowing
over the nearby ridgetops. Generally VFR conditions will rule,
but occasional ceilings below ILS breakpoints are possible from
KRIL to KASE and KEGE.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Winter Storm Warning until 6 PM MST Monday for COZ004-013.
UT...None.
&&
$$
SHORT TERM...TGR
LONG TERM...TGR
AVIATION...BM
Area Forecast Discussion
National Weather Service Green Bay WI
528 PM CST Sun Nov 5 2017
Updated aviation portion for 00Z TAF issuance
.SHORT TERM...Tonight and Monday
Issued at 122 PM CST Sun Nov 5 2017
The latest RAP analysis and satellite/radar imagery show a cold
front exiting the region over Lower Michigan, while high pressure
extends southeast across the northern Plains. Cloud cover remains
widespread from North Dakota into western Wisconsin despite high
pressure building east. Some of the higher resolution models
indicate clearing taking place from southwest to northeast across
northern WI. Satellite has not shown this trend starting however,
so have increased sky cover to mostly cloudy for the rest of the
afternoon. Cloud trends are the main forecast concern in this
part of the forecast.
Tonight...High pressure over the northern Plains will be building
southeast into the state. The airmass is pretty dry above the
inversion, but the concern is that the ample cloud cover present
across the region becomes trapped beneath the inversion, making
it difficult for clearing to take place. Models are fairly
aggressive with the clearing tonight. However, trended toward the
statistical guidance, which delays the clearing until mid to late
evening in the east and overnight in north-central WI. Temps may
not fall as much as previously thought due to the clouds, so
increased them a degree or two.
Monday...A few scattered clouds may linger across north-central WI
early in the morning. Otherwise, shortwave energy will be moving
across the northern Plains and northern Mississippi Valley over
the course of the day. Mid and high clouds will be increasing from
mid morning through the afternoon, but any precip should remain
well west of the region. Highs ranging through the 30s.
.LONG TERM...Monday Night Through Sunday
Issued at 122 PM CST Sun Nov 5 2017
Fairly zonal flow for the first half of the week supports a
colder than normal regime with a few periods of light snow.
A reinforcing cold front Monday night into Tuesday with an upper
jet let and weak short wave will provide a period of light snow
to mainly northern Wisconsin. Northwest flow behind the front
will provide a brief period of lake effect snow showers across
the far north before the surface high pressure region dominates
through mid week.
A northern stream shortwave is progged to dip into the northern
Great Lakes Wednesday night into Thursday while a frontal system
develops over the Northern Plains into the western Great Lakes
region. While saturation at the onset will be an issue for
precipitation start time, progs have diverted to an even colder
pattern, with the ECMWF 850 mb temperatures falling as low
-16 C Thursday night. The GFS is not as cold but is also latching
onto this colder trend.
Model timing of another system for next weekend is not consistent
yet, but if the very cold air intrusion late this week pans out,
precipitation type for next weekend could be mainly snow for all
locations.
Long range runs suggest a moderating trend with temps after next
weekend.
&&
.AVIATION...for 00Z TAF Issuance
Issued at 525 PM CST Sun Nov 5 2017
Cloud trends are the main aviation forecast issue this evening.
Guidance is pretty aggressive in clearing the clouds, but
satellite images show an expansive low cloud deck still across the
region. Suspect the models are too fast with the clearing, so
slowed it down with the 00Z TAF issuance. Bases/ceilings will also
probably be lower than indicated by the guidance.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM.....MPC
LONG TERM......TDH
AVIATION.......Skowronski
Area Forecast Discussion
National Weather Service North Platte NE
508 PM CST Sun Nov 5 2017
.SHORT TERM...(This evening through Monday)
Issued at 332 PM CST Sun Nov 5 2017
The forecast through Monday afternoon concerns a subtle shortwave
crossing the northern Plains, with precipitation type being the main
challenge. As of 21z, a broad shield of altostratus spanned Wyoming
and Nebraska as H85 easterlies provided moisture and upslope flow.
Sfc dew point depressions were around 20F across the region,
indicative of low level dry air.
Gradually increase PoP this evening from west (panhandle) northeast
to cover much of the Sandhills. Mid level fgen intensifies across
southern SoDak after 00z, and forecast soundings suggest the
strongest lift (centered around 600hpa) generally 03z-06z. Once the
column saturates, ice initiation is likely with temps aloft cooler
than -10C aloft. Since the highest PoP occur at night, sfc temps
will keep falling into the 20s, so expect -SN as the main ptype.
However, some runs of the HRRR and RAP, as well as the 12z NAM
suggest the potential for FZRA in the panhandle. The LBF 12z RAOB
measured a warm nose of 4C at 750mb. Forecast soundings keep the
warm intrusion past 06z Monday, but the depth and magnitude has been
inconsistent. Nevertheless, introduced FZRA/SN invof KAIA.
Confidence is fairly low in the coverage and intensity of the FZRA,
precluding any ice amounts in the official forecast. In the main
band of precip, dynamic cooling should keep the temp profile cold
enough for all snow. Southern Sheridan and Cherry counties continue
to be pegged for the highest amounts (up to one inch). Used SLR
around 11:1, which is near climo for November. Snow rates could be
locally enhanced as there`s a hint of slantwise instability in X-
sections, along with a brief period of theta-E folding. Across SW
Neb, kept mention of flurries as broad/weak isentropic upglide
coincides with decent low/mid level moisture.
Another concern is patchy fog Monday morning due to continued
shallow layer of moisture and relatively light southeast sfc winds.
SREF shows highest probability in the panhandle, so constrained
mention to west of Hwy 61.
For temperatures, made little change to tonight`s lows, but dropped
Monday highs slightly. Despite weak WAA at H85 (roughly 3C in 24
hrs), expanse of clouds and timing of precip (both the AM and the
next round in the PM) will limit temps.
.LONG TERM...(Monday night through Sunday)
Issued at 332 PM CST Sun Nov 5 2017
The overall synoptic pattern to start off the long term would be
characterized as zonal with a few embedded shortwaves in the mean
flow. The strongest of such will continue to dive south into the
Great Basin and eventually central Rockies on Tuesday. Extending
east from the wave is an area of channelized vorticity well into the
Great Lakes. This wave and area of vorticity will combine with
favorable upper level dynamics to produce an area of precipitation
mainly targeting southwest and south central portions of the CWA
Monday night and into Tuesday. Temperatures will be supportive
enough for a changeover to snow Monday evening with the potential of
1-2 inches of accumulations west of Highway 61 through Deuel and
Garden Counties. Will continue likely wording there with lesser
chances to the north and east. Will need to monitor thermal
profiles with this system. The models backed off on a warm nose
which would have brought some freezing ptype to the region. As of
the 12z runs, the favored ptype is rain changing to snow, but will
still monitor. Otherwise the system will continue to drop south and
east across the southern plains with a continued period of zonal or
near zonal flow aloft atop west central Nebraska. Temperatures will
be cold in post frontal conditions through Wednesday, but moderate
each day to wrap up the work week. Highs in the 30s will transition
to the lower 50s by weeks end with lows mainly in the 20s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 500 PM CST Sun Nov 5 2017
Latest surface plot shows VFR conditions across western and north
central NEB. Upstream, lower ceilings (as low as MVFR) and areas
of light rain were present in the southwest and central
Panhandle. Ceilings will lower across the eastern Panhandle and
the Sandhills this evening, mainly to MVFR or low-end VFR (less
than 7 kft). Ceilings will then continue to deteriorate overnight
across northern NEB and into far southwest NEB. Of which, the next
shot of precipitation is expected to develop/move in mid-late
evening across northern Panhandle into northwest NEB-Cherry
county. Impacts to the KVTN are anticipated, specifically
visibility reduction down to MVFR possible. Precip is expected to
be short-lived and move across northern Nebraska overnight. Snow
is expected to be the primary precip type. However, a wintry mix
or freezing precip cannot be ruled out in parts of the eastern
Panhandle, especially early on. Conditions should improve to VFR
across the area by mid morning.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...Snively
LONG TERM...Jacobs
AVIATION...ET
Area Forecast Discussion
National Weather Service Mobile AL
532 PM CST Sun Nov 5 2017
.DISCUSSION...Updated for latest aviation discussion below.
&&
.AVIATION...
06/00Z issuance...Primarily a VFR forecast through much of the period,
but conditions deteriorate somewhat overnight and into the early morning
hours Monday with development of areas of fog and low ceilings. Expect
visibility to gradually reduce to IFR at many locations by late evening
into early predawn hours Monday, with areas of LIFR to VLIFR vsbys/cigs
in low clouds & fog developing by around 06/06Z and continuing through
around 06/13-15Z Monday. Surface winds light and variable overnight,
then southeast to south 5 to 10 knots on Monday. 12/DS
&&
.PREV DISCUSSION... /issued 410 PM CST Sun Nov 5 2017/
NEAR TERM /Now Through Monday/...A broad zonal mid level flow
pattern prevails across our region this afternoon to the north of a
ridge of high pressure extending from the Gulf of Mexico through
northern Florida and southern Georgia. A surface ridge of high
pressure also extends from the Eastern Seaboard through the
southeastern states and the adjacent Gulf of Mexico. Partly sunny
and warm conditions are the rule over our region this afternoon with
temperatures in the upper 70s to lower 80s and light southerly
winds.
Little change to the overall pattern is expected across our area
through Monday afternoon. The upper level ridge of high pressure
will continue to stretch from the Gulf of Mexico through the Florida
peninsula and adjacent western Atlantic Ocean, while the surface
ridge axis continues to extend from the Eastern Seaboard through the
Gulf of Mexico tonight, before becoming more centered over the
northern Gulf by Monday afternoon. Little in the way of deep layer
moisture will be available over our area underneath the continued
zonal flow pattern aloft, so will maintain the dry forecast into
Monday afternoon. The primary weather impact of concern will be
another round of dense fog which is expected to initially develop
near the coast late this evening before spreading north/northeast
with time over inland areas overnight into early Monday morning.
SREF fog probabilities, along with consensus from the NAM-12, WRF-
ARW, and the past few runs of the HRRR lend confidence that areas of
dense fog will especially impact areas generally along and southeast
of a Wiggins, MS to Grove Hill, AL to Luverne, AL line where we have
decided to issue a Dense Fog Advisory from midnight tonight through
9 A.M. Monday morning. Probabilities for dense fog were a little
lower over far northwestern and northern areas, but would not be
surprised if later shifts need to expand across these remaining
locations later tonight if confidence increases. For now we just
mentioned more of a patchy dense fog potential in Perry, Wayne,
Choctaw, and Wilcox counties. Fog should dissipate by mid Monday
morning. Lows tonight should range from the upper 50s to lower 60s
again inland, and in the mid 60s near the immediate coast and
beaches. Expect partly to mostly cloudy skies Monday afternoon with
highs once again ranging in the lower to mid 80s inland and in the
upper 70s to around 80 near the coast. /21
SHORT TERM /Monday night Through Wednesday night/...
By late Monday, surface ridge over the central Gulf Coast allows for
very light wind conditions leading into the overnight hours. These
winds when coupled with dew points over 60F should permit
significant fog development overnight leading into the morning
Tuesday. Overall zonal upper level jet-max moves into the central
Mississippi River Valley Tuesday with the surface boundary near the
Alabama/Tennessee boarder. An embedded surface low near the
border has a trailing cold front that will help nudge the boundary
south throughout the day. Yet, the boundary remains far enough to
our north that no rain is expected Tuesday allowing max temps to
reach the upper 70s/low 80s. Another night of fog should again be
possible early Wednesday morning. The limiting factor being
whether or not the increasing mid to upper level cloudiness will
allow temps to fall to the dew point thresholds. Regardless
temperatures overnight Tuesday should be in the low 60s.
Upper level jet and surface cold front continue to sag south towards
the coast Wednesday. The increasing moisture in the mid-levels
should push PWAT values locally to near 1.6 inches. The northern
most counties will be the most effected by this rain and some of
these counties could see rain through the day and into mid Thursday.
DJ/17
LONG TERM /Thursday Through Sunday/...
The development and progression of a shortwave trough in southeast
Oklahoma is the main area of focus for Thursday. As this trough
deepens and dives south in the early to late morning hours Thursday
expect to see heavy rain for much of central and southern Alabama.
By the afternoon, there could be areas east of I-65 that may be able
to develop strong storms as CAPE values will be over 1000 J/kg.
However west of I-65 where most of the precipitation is expected
to develop, models are showing limited instability ahead of the
main trough axis. The good news is by the evening Thursday a re-
enforcing cold front will push south through the forecast area drying
out southern Alabama through the weekend. Temperatures Thursday
night into early Friday morning will fall into the low 50s with
some areas inland seeing upper 40s.
Anticipate steady north winds over Central Gulf Coast in the wake
of the frontal passage Friday as temperatures struggle to rise
above 70 for most of the area. After sundown with clear skies
temperatures will be dip once again into the low 50s. Dry and cool
conditions continue for Saturday. Yet, winds are expected to
begin to veer throughout the day as a mid-level trough and
associated surface low in central Kansas begin to influence the
local wind field. The development of this trough will be the next
area of focus for the region late into the weekend. DJ/17
MARINE...A surface ridge of high pressure will remain in place over
the local marine area into the early part of this week. Patchy fog
may re-develop late tonight into early Monday morning over inland
bays and sounds, and we will need to monitor closely for any
potential Marine Fog Advisories. Otherwise, light onshore flow
generally prevails during the afternoon and evening, with light west
to northwest flow developing late at night into the early morning
hours through early Wednesday. Flow becomes more westerly Wednesday
afternoon and evening ahead of the next approaching cold front. The
front now looks to pass across the marine area Thursday with
increasing offshore flow in its wake through Thursday night and
Friday morning. Rain showers and possibly a few thunderstorms will
increase in coverage with the passing front Thursday. /21
&&
.MOB WATCHES/WARNINGS/ADVISORIES...
AL...Dense Fog Advisory from midnight tonight to 9 AM CST Monday for
ALZ052-053-055>060-261>266.
FL...Dense Fog Advisory from midnight tonight to 9 AM CST Monday for
FLZ201>206.
MS...Dense Fog Advisory from midnight tonight to 9 AM CST Monday for
MSZ076-078-079.
GM...None.
&&
$$
This product is also available on the web at:
http://weather.gov/mob
Area Forecast Discussion
National Weather Service Marquette MI
640 PM EST Sun Nov 5 2017
.SHORT TERM...(This evening through Monday)
Issued at 343 PM EST SUN NOV 5 2017
Water vapor imagery and RAP analysis show a broad trof encompassing
the Pacific NW to the Great Lakes. Shortwave that was over southern
Saskatchewan 24hrs ago is now over northern Ontario. Associated cold
front and -shra have cleared the fcst area. However, a small area of
post frontal -shra has been passing across n central Upper MI over
the last couple of hrs. Gusty wnw winds have developed in the wake
of the front with a couple of the high obs platforms on Lake
Superior gusting to around gale force. Over land, KCMX has reported
the highest gust at 41mph.
Ongoing CAA will drop 850mb temps down to -10 to -12C tonight,
providing a lake-850mb delta-T of at least 17C. While this is more
than sufficient for LES, incoming dry air mass, inverted-V temp/dwpt
profile in the boundary layer and shallow cloud depth per fcst
soundings, and large scale anticyclonic flow suggest LES will
struggle, especially so off western Lake Superior due to more
pronounced inverted-v profile and shorter fetch for lake
modification. Longer fetch into the ne fcst area under nw flow
provides better potential of some -shsn to develop into that area.
Still, expect LES to struggle. For now, nothing more than isold
-shsn mention will be included in the fcst for the wnw to nw flow
lake effect snowbelts. May not be much more than flurries for much
of the time. Clouds will largely dominate tonight, but areas that
see downsloping under a nw wind may break out to partly cloudy.
Expect min temps mostly in the 20s with around 30F along Lake
Superior. If winds back sufficiently over the far w before sunrise
to lose the upslope wind off Lake Superior, allowing clouds to
break, temps may slip blo 20F toward the MI/WI stateline.
Continued backing of winds on Mon as sfc high pres ridges across
WI/Lwr MI will shift whatever LES there is toward the n. This
backing of winds should favor a convergence zone lifting n from n
central Upper MI, and this may support a little greater coverage of
-shsn streaming into the ne fcst area for a time on Mon. Still,
don`t expect anything more than a dusting of snow. Away from lake
effect cloudiness, expect a partly cloudy day. High will generally
be in the 30s across the board.
.LONG TERM...(Monday night through Sunday)
Issued at 252 PM EST SUN NOV 5 2017
The main forecast highlights: Chances for lake effect snow early,
mainly in the west to northwest wind snowbelts, with below normal
temperatures for this time of year. Monday night into Tuesday, we
could see light snow across the interior portions of Upper Michigan
as shortwave energy tracks across the Upper Great Lakes. Towards the
end of the week, the attention turns towards the potential for the
coldest air of the season thus far, with winter-like temperatures
possible Thursday/Friday and lake effect snow. These winter-like
temperatures do look rather transient and should only last for about
24 hours, as warm air advection will return northward across the
Western Great Lakes ahead of another approaching shortwave this
weekend.
Monday night through Tuesday: The upper-level pattern will shift a
bit more northwesterly as a shortwave digs south across southern
Ontario Monday night. The main trough axis however is progged to
become elongated across the northern Plains with a stream of
vorticity progged to track across the region during the overnight
hours. This will foster chances for snow across the area and the
onset of lake effect snow as cold air advection increases
immediately behind the main trough axis. Overall, at this time any
accumulating snow across the interior should remain light Monday
night. Near Lake Superior, primarily in the northwest wind
snowbelts, lake effect snow is expected to increase in coverage
through the overnight hours. It does look possible that a few
dominant bands of lake effect snow may develop across the east near
the shores of Lake Superior as surface troughing should allow for
increased low-level convergence. Throughout the day on Tuesday,
850mb flow will become more westerly and push any lingering lake
effect snow showers into the west wind snowbelts. Across the east,
snow may begin to transition over to rain/snow mix as temperatures
warm above freezing. Tuesday night drier air will advect across the
region as surface ridging tries to push northward across Upper
Michigan, this should allow lake effect snow to diminish in the west
wind snowbelts, if not dissipate all together.
Wednesday: A weak surface trough associated with a strengthening area
of low pressure across the Hudson Bay will push east-southeast
across Upper Michigan. Convergence along this frontal boundary does
not look impressive, but given the westerly winds regime and cooler
temperatures filtering in behind the surface trough, expect lake
effect snow to develop primarily in the west wind snowbelts during
the day.
Wednesday night through Friday: As two large, slowing moving cutoff
lows begin to break down the upper-level pattern will become more
progressive and active across the region. Overall, there is still
some uncertainty in how temperatures and precipitation chances will
evolve; however, the models have come into better agreement with the
overall trends. We`re still looking at a brief shot of colder,
arctic, air but the arrival of this air mass will depend on the
strength of the trough and its associated surface features. The
Canadian is far more robust with this system and would favor a
chance for precipitation Wednesday night into Thursday with the
colder air arriving during the day on Thursday -- this would favor
lingering lake effect snow in the north wind snowbelts through a
good portion of the day Thursday into Friday. The GFS is much slower
and weaker with the upper-level trough and would favor the arrival
of the associated low pressure system and colder air mass Thursday
night through Friday -- this would favor better precipitation
chances Thursday night with lingering lake effect snow in the north
wind snowbelts through Friday night. The recently ECMWF solution
falls in between the two. Given the uncertainty in the arrival of
this colder air mass, either Thursday or Friday will be the
coldest/snowiest day of the week as afternoon highs may struggle to
climb into the mid to upper 20s across much of the area and lake
effect snow impacts the north wind snowbelts. The combination of
brisk northerly winds and ample cold air advection will make it feel
like temperatures have fallen into the single digits in some
locations Thursday night.
This upcoming weekend: The above mentioned upper-level trough will
continue to lift northeast of the region. This will allow high
pressure to track across the region during the first half of the
weekend and lingering lake effect to shut down. Temperatures will
rebound into the 30s as warm air advection/return flow develops
across the region ahead of a shortwave progged to eject out of the
intermountain west later in the weekend. Once the better synoptic
forcing arrive later in the weekend, chances will increase for
widespread light snow.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 636 PM EST SUN NOV 5 2017
Influx of drier air in the wake of a cold frontal passage will
allow MVFR cigs at KIWD/KCMX/KSAW to improve to VFR this late
tonight into Monday morning. VFR conditions will then continue
thru the end of the fcst period. Winds will continue to be gusty
at KCMX where gusts to around 25kt are expected. &&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 343 PM EST SUN NOV 5 2017
In the wake of a cold front and ahead of high pres over the Northern
Plains, wnw to nw winds of 20-30kt will generally prevail across
Lake Superior tonight. Some gale force gusts to 35kt are possible
during the evening over the e half of Lake Superior. Winds will
remain mostly in the 20-30kt range Mon into Mon night. While there
may be a brief period of lighter winds for part of Tue, winds will
quickly increae back to at least 20-30kt Tuesday night ahead of a
sfc trof dropping se toward Lake Superior. Gales will be possible.
Under a weakening pres gradient, winds will diminish Wed aftn/night,
possibly to under 20kt. Another passing low pres trof will increase
winds on Thu with a period of gales possible in its wake Thu night.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...Rolfson
LONG TERM...Ritzman
AVIATION...Voss
MARINE...Rolfson
Area Forecast Discussion
National Weather Service Nashville TN
714 PM CST Sun Nov 5 2017
.UPDATE...
FOR EVENING DISCUSSION.
&&
.DISCUSSION...
Latest regional mosaic radar imagery shows a line of showers and
thunderstorms has formed along the cold front to our northwest,
and currently stretches from west of Poplar Bluff, Missouri
northeastward to just northwest of Evansville, Indiana. A few
showers have also recently formed out ahead of the line. All of
this activity is forming just west of a CAPE axis of 500-1500
J/Kg located generally along the Ohio River. Latest HRRR model
along with 18Z guidance are in excellent agreement taking this
line of storms southeast into Stewart County around 05Z, then
continuing southeast across Middle Tennessee overnight while
weakening as they outrun the main instability axis. Based on the
latest guidance, have lowered pops significantly through mid
evening, then ramp up precip chances to near 100 percent from
northwest to southeast overnight. Made some other minor tweaks to
grids and zones based on latest obs but nothing significant.
Areas along and north of I-40 remain in a marginal risk for some
severe storms tonight, but convection to our northwest has
remained sub-severe so far this evening and it is appearing
unlikely we will see much if any strong or severe storms in our
neck of the woods due to the much lower CAPE and shear in place
here. Nevertheless, cannot rule out a strong storm or two with
damaging winds and possibly some hail, mainly in far northwest
Middle Tennessee counties where instability is highest.
&&
.AVIATION...
00Z TAF DISCUSSION.
At 23Z the cold front stretched from Farmington...MO to
Pickneyville...IL...to Bloomington...IN. It is moving southeast
and will move into middle TN /KCKV/ around 0630Z and reach KCSV
around 10Z. It will bring showers and thunderstorms with it...some
possible strong. Isolated showers will persist behind the front.
Conditions around the TAF sites are VFR now but will become MVFR
and finally IFR.
For CKV expect MVFR for ceilings to start around 03Z and IFR
around 10Z and hopefully going back to MVFR around 17Z. It will
also be IFR in and around thunderstorms.
For BNA and MQY MVFR for ceilings should start around 06-07Z and
IFR around 13Z and hopefully back to MVFR around 18Z. Once again
it will be IFR in and around thunderstorms.
For CSV it will become MVFR for ceilings around 06Z and stay that
way through the end of the TAF period. It will also drop to IFR in
and around thunderstorms.
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION......Shamburger
AVIATION........12
Area Forecast Discussion
National Weather Service Mount Holly NJ
829 PM EST Sun Nov 5 2017
.SYNOPSIS...
A cold front will move through the region tomorrow. High pressure
will build into the Northeast behind the cold front as it sags
southward into the Southeast. Waves of low pressure will develop
along the front and move northeast off the coast of the Carolinas
through much of the week. A strong cold front will sweep across the
Eastern Seaboard late this week, with the coldest air of the season
so far left in its wake.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
High pressure well to the NE will continue to produce an onshore
flow tonight across our area. A continuation of low clouds and
perhaps a scattered shower (mostly north) can be expected in this
pattern. It will remain mild and humid overnight with lows only
dropping into the mid 50s (north) and closer to 60 across Delmarva
and metro Philadelphia. Winds will be mostly E or SE this evening,
but then switch around to S or SW by dawn. Breaks in the clouds
this evening have allowed patchy fog to form over parts of New
Jersey. This fog should linger into overnight before the focus
in fog shifts further northwest closer to the warm front and
moister environment. The latest HRRR and RAP model runs do
continue to bring isolated showers through most of the region,
which is reflected in the latest update.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
There will be plenty of clouds across the area Monday morning. Winds
will increase as the cold front to the west approaches. Showers will
be moving in across the wrn counties early, then they will spread
eastward through the day. Pops are generally in the low categorical
range in most areas. It will (likely) be the mildest day of the week
with highs in the 60s (north) and low 70s (south/east) before the
front arrives. Winds will be mostly SW at 10 to 15 mph during the
morning, and then shift to W or NW by evening. There is a small
chc for a tstm with the front, but overall we will just have
slgt chc or chc pops for that at best.
&&
.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
Unusually poor model agreement continues in the long term. A
very low-confidence forecast, to say the least.
Model disagreement starts right from the get-go, with the 12Z
NAM showing that Tuesday may be fairly wet across most of the
area (but particularly along/south of I-76). The 12Z GFS is
farther south, and the 12Z ECMWF splits the difference. However,
its QPF is on the higher side (though not as high as the NAM).
The CMC has also trended a bit north and a bit slower as well.
WPC noted some question marks regarding the progression of a
positively-tilted trough moving through the central U.S. during
this period and its influence on downstream surface waves, and
until these uncertainties are resolved, expect fairly large
swings model run to model run with QPF placement/magnitudes.
Notably, the just-now-arriving 18Z NAM continues its bullish QPF
(1-2 inches Tuesday and Tuesday night) but considerably farther
south (Delmarva versus SE PA and central NJ in 12Z NAM).
Strength of the NAM/CMC surface features and resultant QPF has
me worried, though the pattern is more favorable to weaker
phenomena (generally zonal flow). PoPs/QPF were a blend of the
operational models, but weighted toward the middle-ground
solutions of the GFS (dry) and ECMWF (wetter). I did incorporate
the NAM/CMC as well, given the uncertainty with timing and storm
totals. This may end up being a much more significant
precipitation event than Monday`s action, but confidence is
extremely low on the details at this point.
With cold frontal passage Monday and Monday night, temperatures
will be considerably colder on Tuesday and Wednesday, with highs
near to slightly below seasonal averages. Some inherent lack of
confidence should be assumed given the uncertainty with
precipitation coverage/timing.
Aforementioned trough in the central U.S. makes its move east
Thursday, kicked by a potent northern-stream vort max in the
Upper Midwest. Timing discrepancies remain with this trough, but
these differences have lowered during the past 24 hours of
simulations. It looks like the strongest large-scale lift and
low-level focus (i.e., the cold front) will be south of the
region by this point, and the flow is progressive enough to keep
any developing surface lows fast-moving and mostly away from the
area. There are, however, some hints at some sparse
precipitation coverage farther north between the southern-stream
and northern-stream systems. As such, needed to keep some PoPs
for the region Wednesday and Thursday, but these gradually lower
with time. The CMC looks quite bullish with rain during this
period, but I could not discount it entirely owing to the
potential phasing of the two systems. Nevertheless, the farther
south depictions of the GFS/ECMWF leave me skeptical regarding
much if any precipitation Wednesday night and Thursday.
Generally kept slight-chance PoPs for this time frame.
Temperatures on Thursday so far look similar to Tuesday and
Wednesday.
The bottom falls out on Friday (give-or-take), as the northern-
stream trough sends an arctic front surging southeastward. GFS
has finally caught on to the ECMWF "cold"-wagon, but timing
discrepancies in frontal passage are severe, with the GFS
(unusually) on the slow side. MEX-MOS for Philly has 62 Friday;
EC-MOS has 50. Similar discrepancies exist Friday night, but by
Saturday, both are embracing the cold. Suspect a hard freeze is
in store at least one of the two nights (Friday night or
Saturday night), and no doubt this will be the coldest air of
the season so far. Mentioned this in the HWO (given potential
for frost/freeze products for locations still in the growing
season).
There are hints of a fairly potent system developing late in the
forecast period (Sunday into early next week), with the GFS
developing a strong low off the Carolina coast Monday morning
with widespread precip in the Mid-Atlantic and the ECMWF a
little bit weaker (but the 00Z run had a stronger/slower/farther
west system). Meanwhile, the CMC has nothing near the intensity
of either. For now, enough of a risk for some mention of PoPs
Sunday, with some moderation in temperatures by this point.
&&
.AVIATION /01Z MONDAY THROUGH FRIDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.
Overnight:
A lot of uncertainty in this period of the TAF forecast. Right
now ceilings are highly variable in many locations from the TAF
sites near I-95 and points southeast. Enough clearing is even
present for fog formation at KACY and KMIV. The general trend of
lowering ceilings through the remainder of the evening into the
overnight is reflected though suspect it will continue to be a
indirect route to get there. A little more certainty is
beginning to evolve for a period of IFR ceilings at most TAF
sites for a few just before sunrise. Fog has the potential to
develop overnight at the remainder of the TAF sites as well
overnight.
Monday: Probably VFR/MVFR until the showers associated with the
cold front arrive. Timing is likely to be closer to 15Z for KRDG
and closer to 20-21Z for KACY.
OUTLOOK...
Monday night: Conditions may improve to VFR with winds generally
north 5 to 15 kts. However, there are indications that another
system will move in late in the night, with sub-VFR conditions
returning, especially south of KPHL, where a chance of showers may
persist. Confidence very low.
Tuesday and Tuesday night: A chance of rain, especially near and
south of KPHL, with sub-VFR conditions possible. North to northeast
winds 5 to 15 kts. Confidence well below average.
Wednesday: Residual sub-VFR conditions possible early with rain
gradually ending, but conditions may improve to VFR by late morning
or afternoon. Northeast winds 5 to 15 kts. Confidence well below
average.
Wednesday night and Thursday: Mainly VFR with light northeast
winds. Confidence below average.
Thursday night and Friday: Winds becoming northwest as a cold front
moves through the area. Winds may be gusty Friday afternoon.
Conditions mainly VFR. Confidence average.
&&
.MARINE...
Winds will remain relaxed this evening, but then increase
overnight as the next cold front approaches from the W. Given
seas have fallen below five feet in the southern waters we
allowed the SCA to expire for the Delaware and southern New
Jersey coastal waters, Seas will linger around five feet
further north where an SCA is still in effect.
OUTLOOK...
Monday night through Wednesday: Seas may hover around advisory
thresholds through the period. Northeast winds may gust to around 25
kts late Monday night after a cold front moves through the Atlantic
waters. Northeast winds may again approach advisory levels late
Tuesday night and Wednesday as well. A chance of rain through the
period, but especially Tuesday afternoon and night.
Wednesday night through Friday: Conditions generally below advisory
levels. There is a slight chance of showers Wednesday night and
Thursday, but this period is more likely to be generally fair.
&&
.TIDES/COASTAL FLOODING...
No new advisory issuances today.
Todays morning early afternoon tides were unexpectedly even higher
than the modeled departures. We`re going to run a positive bias on
the surge through Wednesday, knowing that tomorrow may end up a
little less of a positive departure than we`re modeling but we`re
trying to get back on target with our forecast tonight.
The Monday high tide cycles should remain just below minor threshold.
Tuesday and Wednesdays late morning midday high tide cycles will be
different as onshore flow develops, possibly enhanced by one or
two waves of weak low pressure scooting seaward from a latitude
somewhere to our south (off the VA/NC coast). As of now we`re
expecting the need to issue advisories for one or both of those
tide cycles, at least for Ocean County southward to the DE
Atlantic waters of Sussex County DE and a bit up into lower DE
Bay.
Thursday late morning may also present a close call for minor flood
tidal inundation flooding ,but maximum daily astronomical tides
are slowly decreasing and so the threat should decrease
Thursday, barring an unforeseen gale.
So as of now...we`re monitoring departures for the next 36 hours...
but not issuing any new advisories today.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory until 7 AM EST Monday for ANZ450>452.
&&
$$
Synopsis...CMS
Near Term...Gaines/O`Hara
Short Term...O`Hara
Long Term...CMS
Aviation...CMS/Gaines
Marine...CMS/Gaines/O`Hara
Tides/Coastal Flooding...