Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/31/16
Area Forecast Discussion
National Weather Service Albany NY
1021 PM EST Fri Dec 30 2016
.SYNOPSIS...
High pressure will build in tonight but lake effect snow bands
will continue overnight. A quick moving low pressure system will
bring more snow to the area Saturday and Saturday night with a
moderate snowfall expected for the western Adirondacks. High
pressure will bring fair weather to the area on Sunday before an
approaching low pressure system will bring some wintry
precipitation to the area Monday into Tuesday.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Lake Effect Snow Advisory for the western Mohawk Valley extended
until 5 am.
As of 1021 PM...Weather radar loop shows main lake effect snow
band affecting our area is clipping southern herkimer County and
extending into Schoharie, Greene, Columbia and Berkshire Counties.
The band appears to be slowly lifting northward towards the
advisory area. Latest HRRR has band moving northward and
continuing until around 08Z so extended the LES advisory until 5
AM. Some areas in Schoharie, Greene and western Albany Counties
may pick up a total of 2-3 inches of snow from this band as it has
been persistent and only slowly moving northward.
Outside of lake effect bands, clouds have broken or cleared. Temperatures
are mostly in the 20s with teens across the western adirondacks to
around 30 in far southern Ulster, Dutchess and Litchfield Counties.
KENX VAD wind profile still shows 10-25 kts in the boundary layer
so gusty winds are gradually diminishing. Winds will diminish more
overnight.
Overnight lows will run from near 10 degrees across the highest
terrain of the western Adirondacks to the lower 20s in Hudson
Valley from the Poughkeepsie area up into the Capital District and
into northwestern Connecticut.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/...
Winter Weather Advisory for a moderate snowfall has been issued
for 10 am Saturday until 6 am Sunday as quick moving clipper
system brings another round of snow to the region.
The surface ridge will quickly shift off the coast Saturday and
the weak upper ridging will flatten as a short wave trough/clipper
system quickly from the Great Lakes region. Guidance is in good
agreement with the timing of the system. Used a blended approach
to handle the QPF. Initial should get some light snow due to warm
air advection as the warm front approaches with better and more
widespread snowfall as the associated low level jet moves in. The
highest QPF totals are expected closer to the low across the
northwest portion of the forecast area. Have issued a Winter
Weather Advisory for snow for the western Adirondacks for 4 to 8
inches of snowfall with lighter amounts expected as you head to
the southeast with 1-2 inches for the Capital District and little
if any in the mid Hudson Valley. The snow will wind down Saturday
night with the passage of the short wave trough its associated
cold front.
Higher pressure at the surface and aloft will build in on Sunday
and Sunday night with a return to fair weather.
&&
.LONG TERM /MONDAY THROUGH FRIDAY/...
Monday into Tuesday...upper level ridge is over the Eastern
Seaboard, while a negatively-tilted trough moves into the central
part of the US. The northern portion of this trough looks to result
in strong cyclogenesis over the Upper Midwest, while the southern
portion ejects toward the eastern seaboard. With the dominant low-
level cyclone over the Upper Midwest, warm midlevel air will spread
across the Eastern US. Isentropic lift will increase Monday, but
will be pretty weak initially, so only chance PoPs are in place. The
lift looks to increase Monday night into Tuesday, with good model
consensus, so likely PoPs are in place for that time period.
It appears that p-type will be an issue with this system. A
rather strong high will be in place over Maine Monday, and will only
slowly retreat Monday night and Tuesday. Models are indicating
good southerly surface flow does not kick in until Tuesday at the
earliest. With cold low temperatures expected Sunday night, this
raises the prospects of the cold air being slow to scour out locally,
and we may be more reliant on top-down processes to warm things up at
the surface. Have lowered temperatures from superblend for this
package. Best indication for p-type is a light mixture of snow and
sleet initially Monday, then becoming rain/freezing rain as midlevel
warm air advection results in melting aloft late Monday/Monday night.
Expecting plain rain by some time Tuesday with precip tapering off by
Tuesday night. Fairly good model agreement with the large-scale
players in this system, but low confidence on the details as would be
expected with a system still four days out. Will continue to mention
freezing rain potential in HWO.
Potentially mild day Wednesday as dry slot pushes in. Cold advection
kicks in Wednesday night/Thursday with temps back toward normal by
the end of the week. Possibly some lake-effect snow showers Thursday.
&&
.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
Much of the overnight will see VFR conditions at the TAF sites
with the exception being the occasional snow shower which may
drop conditions to MVFR at KALB and KPSF overnight tonight.
A fast moving low pressure system will bring some light snow to
all the TAF sites except KPOU on Saturday. Snow should begin
between 17 and 23Z Saturday. MVFR/IFR conditions in snow expected
at KGFL, KALB and KPSF.
Blustery conditions will continue this evening, with westerly
winds gusting to near 30 knots at times at KALB/KPSF. Winds will
gradually decrease later this evening to 8-14 kts and then to 3-7
kts late tonight. Winds shift to the south and increase to 10-20kts
Saturday morning.
Outlook...
Saturday Night: Moderate Operational Impact. Likely SN.
New Years Day: No Operational Impact. NO SIG WX.
Sunday Night: No Operational Impact. NO SIG WX.
Monday: Moderate Operational Impact. Chance of RA...SN...SLEET.
Monday Night: Moderate Operational Impact. Likely RA...FZRA.
Tuesday: High Operational Impact. Likely RA.
Tuesday Night: Moderate Operational Impact. Chance of RA.
Wednesday: Moderate Operational Impact. Chance of RA.
&&
.HYDROLOGY...
Active weather pattern continues. Lake effect and upslope snows
wind down tonight. Looking at light to moderate snowfall Saturday
and Saturday night as clipper system approaches and moves across
the region. Fair weather returns for Sunday and Sunday night as
high pressure builds in. However, another round of wintry
precipitation expected including a period of freezing rain Monday
night eventually changing over to plains rain Tuesday as a low
pressure system passing well to out northwest across the Great
Lakes region.
For details on specific area rivers and lakes,
including observed and forecast river stages and lake elevations,
please visit the Advanced Hydrologic Prediction Service /AHPS/
graphs on our website.
&&
.ALY WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...Winter Weather Advisory from 10 AM Saturday to 6 AM EST Sunday
for NYZ032-033.
Lake Effect Snow Advisory until 5 AM EST Saturday for NYZ038.
MA...None.
VT...None.
&&
$$
SYNOPSIS...SND
NEAR TERM...SND
SHORT TERM...IAA
LONG TERM...Thompson
AVIATION...11/Thompson
HYDROLOGY...IAA
Area Forecast Discussion
National Weather Service Goodland KS
700 PM MST Fri Dec 30 2016
.SHORT TERM...(This afternoon through Saturday)
Issued at 1122 AM MST Fri Dec 30 2016
18z water vapor imagery and RAP analysis indicated broad ridging
ongoing across the plains with area of mountain induced cirrus
forming across northeast Colorado. Approaching short trough was
just crossing the Canadian border with corresponding sfc front in
the Dakotas.
Very warm temperatures will continue through the afternoon hours
and may see a site or two near record values given how fast a few
locations warmed...but think strong inversion has already mixed
out which may level off additional warming.
Cold front will sweep across the area and while winds above the
surface will increase with its passage...front appears to be
rather shallow initially with strong inversion limiting momentum
transfer. Temps will be 20-25 degrees cooler tomorrow than today.
There may be a small window for fog development across eastern
Colorado around sunrise should winds decouple completely...but at
this time chances are fairly low for significant fog development.
.LONG TERM...(Saturday night through Friday)
Issued at 117 PM MST Fri Dec 30 2016
An extended cold outbreak looks to be on tap for this period as a
deep trough digs into the western CONUS early in the week then
slowly moves across the remainder of the CONUS. Low level moisture
return ahead of the system in the shallow cold air may result in
some freezing fog/light freezing rain Sunday night/Monday morning.
Soundings look most favorable in the northeast part of the area
around McCook. The very cold air will begin to spill into the area
Monday night and remain entrenched through the end of the week.
There will be a chance for light snow Wednesday and Thursday as
the upper trough axis swings through. Given the very cold air
mass, would expect a dry snow with high liquid to snow ratios.
This may boost snow amounts close to advisory criteria. However,
it looks like a low end event at this time with not much in the
way of wind either.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 430 PM MST Fri Dec 30 2016
For KGLD and KMCK, vfr conditions through the period. For KGLD
winds quickly veer to the northwest then north in the 02z-06z
timeframe at speeds around 11kts as a cold front moves through.
This continues through 18z before winds start to back to the west
then southwest at speeds under 10kts. For KMCK light northwest
winds at taf issuance expected to continue through 19z then back
to the west and southwest at similar speeds (around 6kts) for the
rest of the period.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
SHORT TERM...JRM
LONG TERM...024
AVIATION...99
Area Forecast Discussion
National Weather Service Grand Rapids MI
941 PM EST Fri Dec 30 2016
LATEST UPDATE...
Marine
.SYNOPSIS...
Issued at 316 PM EST Fri Dec 30 2016
Light snow accumulations are expected through the US-10 corridor
late this evening into Saturday morning. Otherwise, the rest of
the weekend looks pretty quiet with highs in the 30s. A strong
storm system early next week will bring some decent rainfall to
Lower Michigan, followed by a return of arctic air and lake effect
snow by Tuesday night/Wednesday.
&&
.SHORT TERM...(This evening through Sunday night)
Issued at 316 PM EST Fri Dec 30 2016
Light snow accumulations are expected across the northern forecast
area tonight, mainly north of a Pentwater to Mt. Pleasant line. New
snowfall of 1 to 2 inches is expected along US-10. Heavier snowfall
is forecast further north across Northern Lower Michigan.
An Alberta Clipper is forecast to track from northern Wisconsin into
the UP overnight. Strong warm advection ahead of the low will result
in light snow breaking out across the far northern forecast area.
Strong southwest flow in the low levels will actually result in
surface temperature gradually rising after midnight, so low
temperatures will occur this evening.
Highs on Saturday will warm into the mid and upper 30s. Will feature
relatively low PoPs across much of the area on Saturday as the cold
front pushes through, but moisture will be limited. The rest of the
weekend looks quiet with dry weather expected through late Sunday
evening. Saturday night lows will be in the 20-25 range. Lower
Michigan will finally get some sun to kick off 2017 with highs in
the mid to upper 30s.
.LONG TERM...(Monday through Friday)
Issued at 316 PM EST Fri Dec 30 2016
Sfc low tracks from Southern Plains into western Great Lakes on
Monday and Tuesday. Cold air is eroded pretty quickly so it doesn`t
appear that freezing rain is a threat at this time. The cold air
returns on the back side of the storm by Tuesday night and
Wednesday with lake effect snow showers for the rest of the week.
The lake effect snows should be persistent but perhaps not heavy as
inversion heights are generally around 5 to 8 kft. We will have to
watch the Thursday to Friday period closely as Gulf moisture streams
northward and phasing of the northern and southern streams is
possible. Although the current operational runs are suppressed
with the trough until it reaches the Atlantic coast, it would not
take much more amplification for it to bring some synoptic snows
to Lower Michigan.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 624 PM EST Fri Dec 30 2016
For the most part I expect VFR conditions through tonight into
mid morning Saturday as the precipitation from the system passing
north of here will keep that precipitation (snow) well north of
the GRR TAF sites tonight. The strong southwest winds have already
blown out the low level moisture so no threat for low celling
either. However winds will be near 50 knots as close as 2000 above
the ground so I put low level wind shear after 06z for that.
Once the cold front comes through in the 15z time frame Saturday, there
looks to be enough lift and moisture for some lake effect snow
showers. Winds will be strong enough for the snow showers to each
all TAF sites. This brief event should end just beyond 00z Sunday.
&&
.MARINE...
Issued at 941 PM EST Fri Dec 30 2016
There seems to be some question as to just how strong the winds
will get in our southern near short tonight. I checked using
BUFKIT with the NAM...RAP and HRRR for MKG...LWA and SBN. It
seems questionable that we would actually get gales. So, I
dropped the gale headline in favor of a Small Craft Advisory
through Saturday afternoon.
&&
.HYDROLOGY...
Issued at 1010 AM EST Fri Dec 30 2016
Flood advisories continue at Ionia and Maple Rapids. Ionia is
slowly receding, while Maple Rapids is near its crest 0.9 feet
above bankfull and will begin a slow recession also. The next
weather impact on the rivers will be rain totaling about a third
of an inch on Monday. This may prolong the amount of time the
Maple River spends above bankfull. River forecast points such as
Ionia and Hastings will be below bankfull prior to the rain but
still running higher than normal, so they will have to be
monitored. Beyond that, colder than normal air will settle in
starting on Wednesday, so concerns will shift toward river ice
redevelopment.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Small Craft Advisory until 7 PM EST Saturday for LMZ844>849.
&&
$$
SYNOPSIS...EBW
SHORT TERM...EBW
LONG TERM...Ostuno
AVIATION...WDM
HYDROLOGY...CAS
MARINE...WDM
Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
817 PM CST Fri Dec 30 2016
.UPDATE...
Issued at 815 PM CST Fri Dec 30 2016
Went ahead and updated the forecast this evening to account for
the latest observational trends. First change was to raise min
temps a bit tonight, as southerly surface winds will stay up
ahead of an approaching front and clouds begin to thicken up
towards Saturday morning. Also lowered dewpoints quite a bit as
latest obs continue to show scant low-level moisture with
dewpoints in the low teens to the low 20s. Given this dry near-
surface airmass, think any precipitation is going to struggle to
saturate all the way to ground level. Latest NAM and HRRR guidance
seem to support this thinking, thus have lowered pops for late
tonight into Saturday morning.
KD
&&
.SHORT TERM... (Through Late Saturday Afternoon)
Issued at 254 PM CST Fri Dec 30 2016
Surface low ahead of a sharp shortwave will move rapidly across the
western Great Lakes on Saturday. Trailing cold front will approach
Central MO by around 12Z Saturday. To the south, a sprawling
surface high across the Gulf Coast will finally move eastward
tonight and allow some return flow from the Gulf of Mexico, but
this will only be for a relatively brief time before the cold
front approaches. Any precipitation late tonight into Saturday
will likely be limited to the far southeastern CWA generally
southeast of an Ellington...to Farmington...to Salem line. Even
though a few snowflakes may mix in with the rain at the onset with
initially dry air at low levels, the thermal profile should limit
any possibility of a significant period of rain/snow as the
atmosphere will be too warm. Both lows and highs should be 10 to
15 degrees above normal tonight and Saturday over all but the far
northern CWA where post-frontal afternoon temperatures will likely
remain steady in the mid to upper 30s.
Browning
.LONG TERM... (Saturday Night through Next Friday)
Issued at 254 PM CST Fri Dec 30 2016
(Saturday night into Monday)
Main forecast challenge is the timing of precipitation early next
week.
Saturday night and Sunday still looks mainly dry as both the GFS and
ECMWF show a shortwave ridge moving across Missouri and Illinois.
Rain chances will increase on Sunday night as weak low level
moisture convergence increase beneath increasing ascent ahead of a
upper trough over the central Plains. Will keep likely PoPs on
Monday as this trough moves across the area.
SREF ensemble mean temperatures are in decent agreement and
generally followed for temperature trends.
(Tuesday through Friday)
GFS and ECMWF are in decent agreement that a strong cold front will
pass through the area late Monday night into early Tuesday which
will bring below normal temperatures for mid-late next week. There
may still be some light precipitation lingering along the front on
Tuesday. While zonal upper flow will initially set up behind the
front on Tuesday, both models are showing a large upper trough
moving southward out of Canada into the Midwest by late next week.
Ahead of the large trough, a weak shortwave will move out of the
Central Plain across Missouri and Illinois bringing a slight chance
of snow by Wednesday night and Thursday. By Wednesday into Friday,
GFS ensemble mean temperatures are showing highs only in the 20s
which is supported by 850 temperatures in the -10 to -20C range.
Britt
&&
.AVIATION... (For the 00z TAFs through 00z Saturday Evening)
Issued at 522 PM CST Fri Dec 30 2016
VFR conditions will persist through the TAF period, but there will
be some terminal impacts due to low-level wind shear. Low-level
wind shear will develop tonight at all sites as winds around 2,000
feet increase to 40-45 knots. SSW surface winds will stay up
around 10-13 knots overnight, but will become more gusty early
Saturday morning ahead of a surface cold front. VFR cigs will
develop ahead of the front late tonight into Saturday morning,
and a stray shower around the STL sites cannot be completely ruled
out. The front will move through all sites by early Saturday
afternoon, bringing a wind shift to the WNW and clearing skies.
SPECIFICS FOR KSTL:
Main terminal impact will be wind shear tonight as winds around
2,000 feet increase to 40-45 knots. SSW surface winds will
increase early Saturday morning ahead of a cold front which will
move through by early Saturday afternoon. VFR cigs around FL050
will increase ahead of the front, and a stray shower cannot be
ruled out Saturday morning. Winds will shift to the WNW behind the
front Saturday afternoon as skies begin to slowly clear.
KD
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&
$$
WFO LSX
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
607 PM CST Fri Dec 30 2016
.UPDATE...
Issued at 607 PM CST Fri Dec 30 2016
Updated the grids/forecast to include scattered flurries around
and to the east and south of the Twin Cities for this evening.
RAP analysis is showing a rather strong band of mid level
frontogenesis stretching W-E across the Twin Cities. This feature
moves rather quickly to the SE this evening. The 12Z NSSL WRF
picked up on this quite nicely and has the light snow/flurries out
of the local area by 04z.
&&
.SHORT TERM...(This evening through Saturday)
Issued at 350 PM CST Fri Dec 30 2016
Clipper currently just north of Minot will track through Fargo and
to the north of Green Bay tonight. We are within the warm sector of
the system and with cloud heights only down to 8k feet, we have done
very little to modify the dry layer of air below 600mb on this
mornings 12z KMPX sounding. Although many of the deterministic
models continue to spit out some light snow this evening in western
WI, think this is overdone given the dry air and we preferred a mix
of rapid updating hi-res models (RAP/HRRR/HopWRF), which looks to
have a better handle on the extent of the dry air. In fact, our best
chance for snow will likely come on the backside of the system. As
winds turn to the northwest and we get into strong CAA advection.
We`ll see the return of low stratus as well. Forecast soundings show
steep lapse rates developing up to about 825mb, with the top of the
cloud layer cooling into DGZ. This should create a shield of snow
showers and flurries following the backside of the low tonight
through the middle of Saturday morning north of I-94.
For temperatures, being in the warm sector, we have been a few
degrees warmer today than we were predicting overnight and we should
see a swath of highs in the mid 30s in SW MN downwind of the Buffalo
Ridge. Favored the warmer guidance for lows tonight, which just
means a slower push of cold air behind the low. The cold trough will
be working across the upper MS Valley Saturday, so highs near to
slightly below normal look good.
.LONG TERM...(Saturday night through Friday)
Issued at 350 PM CST Fri Dec 30 2016
The big weather story in the long term remains the system coming
through Monday and Tuesday. There is substantial model
disagreement between the GFS and other numerical guidance. Hopefully
we get some better consensus over the next 24 hours. The 12z GFS
is a far western (warm) outlier. There is reasonable agreement
between the Canadian/NAM/ECMWF with a low track that is roughly
Kansas City to Chicago. That certainly would suggest snow, but it
also means we`re sort of on the outside of the heaviest QPF that
would fall across IA, far southeast MN and southern WI (although
the ECMWF still has a solid 0.50" locally). The GFS sounding has
rain/sleet/snow with its far western track. We introduced a wintry
mix for a time across eastern MN and western WI to account for
some temperature uncertainty in the forecast - because even the
solutions that are farther east suggest that it will be a warmer
boundary layer when the snow is falling and it will be close to
the rain/snow transition. The upper pattern is fairly complex
with the jet evolving from split flow to a positively tilted
trough and strengthening southern stream. This transition happens
on Sunday, so by tomorrow we hope the GFS/ECMWF will come more in
line. We should note that although the GEFS also shows the
rain/mix potential, overall more of its solutions are a bit
cooler than the 12z operational run.
As mentioned in previous discussions, Arctic air arrives by the
middle of the week and should last through next weekend. This
cold shot doesn`t look quite as cold as what we experienced in
mid December, but it appears to have more staying power and is
reinforced by a couple passing cold fronts over the first couple
weeks in January.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 607 PM CST Fri Dec 30 2016
Two issues tonight. the first is strong mid level forcing
currently stretching from the Twin Cities to Eau Claire. This
feature is helping to promote some -SN to the west and north of
KMSP at TAF issuance. The forcing moves rather quickly southeast
this evening so the thought was to include some -SN in the
KRNH...KMSP and KEAU TAFS for the first 3 hours. The second issue
is a low pressure system over northern MN moving southeast. This
feature will bring widespread snow to areas north of the TAF
sites. However, when we transition to the backside of the low
during the early morning hours, northwest winds will be on the
increase along with MVFR ceilings spreading southeast. These have
been handled well in the TAFS and only minor changes were made.
A ridge of high pressure will spread from west to east Saturday
afternoon bringing VFR conditions to the area. SE winds early
tonight 10 knots or less, veering NW overnight with speeds 12-15
knots with gusts 20-25 knots. Winds slowly diminishing Saturday
afternoon and backing to the SW by evening.
KMSP...Added some -SN through 03z with a few sites north of the
airfield indicating flurries. Otherwise, MVFR ceilings late
tonight and Saturday morning with clearing during the afternoon.
Winds similar to those described above.
/OUTLOOK FOR KMSP/
Sun...VFR. Wind S 5-10 kts.
Mon...MVFR/IFR. Wintry Mix likely. Wind NE 5-10 kts
Tue...MVFR chc IFR. Chance -SN. Wind NW 10-20 kts.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
&&
$$
UPDATE...RAH
SHORT TERM...MPG
LONG TERM...CLF
AVIATION...RAH
Area Forecast Discussion
National Weather Service Marquette MI
627 PM EST Fri Dec 30 2016
.SHORT TERM...(This evening through Saturday)
Issued at 403 PM EST FRI DEC 30 2016
Water vapor imagery and RAP analysis show shortwave ridging shifting
over the Upper Great Lakes ahead of the next shortwave of interest
moving across southern Manitoba/ne ND. Radar imagery shows a nice
band of snow streaking ese with that feature, extending from
southern Manitoba ese across northern MN. Some obs have indicated
vis as low as 1/2sm in the snow. Closer to home, les has been
winding down quickly this aftn with arrival of sfc high pres ridge
axis and inversions falling to around 4kft.
Diminishing les over the ne fcst area will shift offshore around 00z
as high pres ridge axis shifts past the area. Attention, then
quickly turns to the upstream shortwave, which should already be
spreading snow into western Upper MI by 00z. Deep layer forcing per
qvectors is still fcst to be quite strong as is isentropic ascent.
Consistent with recent days model runs, specific humidity up to
2g/kg is avbl around 700mb, suggesting potential for a widespread 2-
4 inches of snow to the n of sfc warm front under band of fgen
during a roughly 6-9hrs of forcing. Advection of steep mid level
lapse rates of 7+C/KM into the backside of the pcpn area may lead to
some convective elements within the snow. 850mb temps of -8 to
-10C will also support lake enhancement off Lake Michigan into the
se fcst area. Majority of models indicate winds may be backed enough
for a time to even bring lake enhancement into Menominee county. So,
the area near Lake Michigan will see the most snowfall from this
event, probably upwards of 6 inches. A few spots may exceed warning
threshold of 6in/12hr. Will be something to monitor. There could
even be a little lake enhancement off Lake Superior into the
Keweenaw for a time tonight under shallow ese winds. Snow will
diminish w to e late tonight into Sat morning. Winter wx advys have
been issued for the entire fcst area tonight.
Fcst for Sat has some issues and potential surprises. Sfc low pres
associated with shortwave will be situated somewhere over w or
central Upper MI at 12z with indications of sharp sfc trof
developing northwestward over Lake Superior. With 850mb temps of -10
to -12C, sharp convergence and deep moisture, band of mdt to hvy
snow could certainly develop along trof and impact the western fcst
area. Based on wind fields/convergence, area around KIWD is a
concern early in the morning and then the Keweenaw morning through
early aftn. A number of high res models point toward the Keweenaw as
the area of greatest potential impact. So for now, opted to run
tonight`s advy thru 21z for Keweenaw County. Not out of the question
that some areas could see very hvy snow for a time. As mdt/hvy snow
along trof shifts se, it will begin to diminish in the aftn as
increasing large scale subsidence overspreads the area. However,
portions of northern and eastern Marquette County and western Alger
County could see a burst of snow in the aftn.
.LONG TERM...(Saturday night through Friday)
Issued at 329 PM EST FRI DEC 30 2016
Models suggest that a mid/upper level ridge building from the
northeast Pacific into Alaska will result in pattern amplification
across the CONUS with a trough over the wrn CONUS expanding eastward
through the week. The pattern will also favor the intrusion of
another very cold arctic airmass by midweek that may linger through
next weekend. Temperatures near or above normal into Tuesday will
drop below normal with LES increasing for nw to wnw snowbelts.
Sat night through Sun night, LES will shift offshore under backing
winds and diminish w-e Sat night as the high pres ridge moves through
the area. 850mb temps climbing to around -5C on Sun will bring
moderating temps after a cold early morning with light winds and
partial clearing under the passing sfc high pres ridge. Although the
sfc high pres is fcst to build into New England Sun night, enough
low level dry air will persist under the sfc ridge axis extending
back into the Upper Lakes to maintain dry conditions through the
night. More mid/high clouds will result in a warmer night.
Monday-Tuesday, The models suggest that a low pressure wave will
lift northeast from the plains to the western Great Lakes. However,
the 06z/12z GFS remained significantly stronger and farther west
(sfc low over northern MN at 12z Tue compared to nrn Lake Huron)
than the 00z/12z ECMWF/ECENS, GEM, and UKMET. So, the forecast leaned
more toward the non NCEP models, per WPC. Nevertheless, there still
may enough of a warm layer into the se cwa to support mixed pcpn,
including sleet and freezing rain along with the snow. ECMWF/GEM QPF
into the 0.50-0.75 inch range suggest potential for heavy snow. As
the low departs significant lake effect or lake enhanced snow for n
to nw flow favored areas will also be possible with 850 mb temps
falling to -15C and a shortwave trough moving through.
Wednesday-Friday, Once the low moves farther e on Wed, long duration
les off Lake Superior will persist with 850 mb temps dropping to -20
to -25C late in the week. Locations affected each day will depend on
daily wind directions with nw winds only gradually backing to wnw or
w by Thursday and Friday. However, the Keweenaw will see the most
persistent LES. Eastern shoreline areas may also get into some of the
heavier LES accumulation.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 627 PM EST FRI DEC 30 2016
Next disturbance and associated area of snow will quickly reach the
area tonight, leading to period of IFR at all terminals.
Some improvement is expected overnight as main snow area departs,
but will likely see IFR cigs set in, which may linger for much of
Sat morning. Conditions will improve Sat afternoon at all sites as
snow moves out.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 329 PM EST FRI DEC 30 2016
As a clipper system moves across Upper Michigan, southeast winds
will increase to around 30 knots from west to east across Lake
Superior before diminishing in speed briefly and veering to the
northeast behind the surface trough and increasing again to 30 knots
over north central Lake Superior. With a ridge building into the
Great Lakes, winds will diminish Saturday night into Sunday.
Northeast winds are expected to increase to 30 knots Monday night
and back to northerly Tuesday as a low pressures system lifts toward
from the plains through the region.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Winter Weather Advisory from 10 PM this evening to 10 AM EST
Saturday for MIZ006-007-014-085.
Winter Weather Advisory until 7 AM EST Saturday for MIZ003>005.
Winter Weather Advisory until 4 AM EST /3 AM CST/ Saturday for
MIZ002-009>011-084.
Winter Weather Advisory from 10 PM EST /9 PM CST/ this evening
to 7 AM EST /6 AM CST/ Saturday for MIZ012-013.
Winter Weather Advisory until 4 PM EST Saturday for MIZ001.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...Rolfson
LONG TERM...JLB
AVIATION...07
MARINE...JLB
Area Forecast Discussion
National Weather Service Norman OK
525 PM CST Fri Dec 30 2016
.AVIATION...
South winds will remain rather gusty much of the night before
decreasing ahead of a cold front that will move through taf sites
late tonight through Saturday morning. North winds will not be quite
as strong as wind speeds were today. Otherwise, VFR conditions to
continue with only some mid and high clouds expected.
30
&&
.PREV DISCUSSION... /ISSUED 505 PM CST Fri Dec 30 2016/
.UPDATE...
&&
.DISCUSSION...
We have updated the short term grids based on trends of RH values
late this afternoon, and for this evening/overnight based on the
latest short term model guidance. Spatial details of slightly higher
surface dew point plumes will be potentially important for
determining RH recovery overnight given the ongoing fires. Based on
LAPS analysis and expected trajectories, the RAP seems to have the
best handle on the current situation. HRRR is similar but slightly
too dry over western north Texas. Current thinking is the area of
higher dew points (low/mid 30s) over the southeast Texas Panhandle
extending barely into far northwest Oklahoma will continue to advect
northeast into the evening and this is where the greatest RH
recovery will occur. Further east across central Oklahoma, dew point
trends will probably be neutral and may even decrease some into the
evening (though probably not to the extent the HRRR depicts) as
drier air moves north. As temperatures cool, RH values should
rise above 40 percent at all locations except the far southeast
shortly after 9pm. Max RH values by morning may only be around 60
percent across the southeast half of the area. The plans are to
let the Red Flag Warning expire at 6pm as cooling occurs and RHs
begin to rise.
A lee surface low is expected to shift southeast into northwest
Oklahoma later tonight and southwesterly winds will not decrease
much through early tonight, but gustiness should subside just
after sunset. A surface trough/developing cold front will
progress through the northwest part of the state during the
morning. Pressure rises behind this front may be sufficient for
15- 20 knot sustained northerly winds immediately behind the
front.
BRB
&&
.PREV DISCUSSION... /issued 254 PM CST Fri Dec 30 2016/
DISCUSSION...
Although relative humidities are rising across our southwestern
counties we will--for now--retain the Red Flag Warning across our
entire forecast area. The evening shift will re-evaluate it, and
make any necessary revisions. In any case, the Warning is set to
expire at 6 pm.
A relatively minor cold front will move through Oklahoma and north
Texas overnight into Saturday, causing only minor changes in
temperature, but will shift winds to northerly and will provide
higher relative humidities.
A much stronger storm system will organize Sunday into Monday,
with its surface low deepening over the central High Plains. For
Oklahoma and north Texas, this will bring warmer and more humid
air back for a couple of days. There may be sufficient instability
for a few thunderstorms in the southeast parts of our forecast
area Sunday night and early Monday. If storms do develop, they
will be in an environment with quite a bit of low-level wind, and
could generate strong, maybe severe, wind gusts.
As this storm system`s center moves northeast, a cold front will
advance quickly southeast across the southern Plains. It will
likely cross Oklahoma from about midnight Monday night into
Tuesday afternoon. This will be the beginning of a much colder
period. Various reinforcements of the colder air will hold
temperatures about 10 to 20 degrees below the average for this
time of year.
While models disagree on details, it does appear fairly likely
that some moisture will be pushed over the cold surface air by
southwest winds aloft. This scenario can produce any type of
winter-style precipitation, and the exact type depends on the
temperature profile at the time. It is way too early to be able to
forecast the exact type, so our forecast is somewhat
oversimplified, and may change significantly before those days
actually arrive. At this points, it appears that precipitation
amounts will be relatively light, but if any of the precipitation
is freezing rain/drizzle, even light amounts can be dangerous.
&&
.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK 39 51 32 58 / 0 0 0 0
Hobart OK 37 50 29 57 / 0 0 10 0
Wichita Falls TX 43 56 33 64 / 0 0 10 10
Gage OK 31 46 24 57 / 0 0 0 0
Ponca City OK 35 47 27 54 / 0 0 0 10
Durant OK 45 62 43 64 / 10 10 10 20
&&
.OUN WATCHES/WARNINGS/ADVISORIES...
OK...Red Flag Warning until 6 PM CST this evening for OKZ004>048-
050>052.
TX...Red Flag Warning until 6 PM CST this evening for TXZ083>090.
&&
$$
12/30
Area Forecast Discussion
National Weather Service Phoenix AZ
605 PM MST Fri Dec 30 2016
.SYNOPSIS...
Periodically unsettled weather will affect the region through Sunday
as a result of two low pressure systems. The first will bring the
best chances for rain tonight into early Saturday while the second
colder system will move in Saturday night and early Sunday. Rain
will be likely Saturday night and Sunday morning with lingering
showers across eastern Arizona Sunday afternoon. Mostly dry but
continued cool and somewhat unsettled conditions are likely for much
of next week.
&&
.DISCUSSION...
A compact vorticty center was penetrating into inland California
early this evening, and moisture flux through the H7 layer was
spreading into western AZ faster than most models had previously
suggested. While vorticity advection was somewhat lagging this slug
of moisture, subtle H7 frontogentical forcing and isentropic ascent
around the 300K layer were supporting rather widespread light
showers through much of La Paz/western Maricopa counties. For the
most part, rainfall accumulations have been solidly in the 0.05-0.20
range. Accordingly, have substantially increase POPs in these areas
while also making some modest increases downstream as vorticity
forced ascent should better overspread central AZ and further help
midlevel showers develop later this evening.
&&
.PREVIOUS DISCUSSION...
/248 PM MST Fri Dec 30 2016/
Latest runs of the HRRR are not nearly as bullish with regard to the
potential for precipitation, while the local WRFs still suggest a
batch of scattered shower activity will move through overnight
albeit with less QPF than earlier projections. Forecast rain totals
have consequently been lowered slightly in the line with the latest
multi-model consensus. Although CAPE will certainly be lacking
overnight, sufficient instability associated with the cold pool
aloft could produce a few lightning strikes and thunder was
introduced in the forecast. Latest guidance also indicates that
showers will clear the lower deserts in the morning, but linger
across the higher terrain east of Phoenix into the afternoon.
Next shortwave trough, fast on the heels of the first one is
currently located off the Oregon coast. This system is comparable to
the first in terms of moisture transport but stronger in terms of
vorticity-forced ascent. Models have exhibited a discernible trend
towards a slower arrival and a slower exit. Highest forecast PoPs
were consequently shifted into the early and late morning Sunday for
much of the area.
This second and stronger "kicker" low will move southeast along the
California coast Saturday with the low center eventually moving into
far SE California Saturday evening. The low will bring 100m or more
of 500mb height falls into far SE California and far western AZ on
Saturday night along with an even more impressive mid level Q
convergence bullseye. UVV/RH cross-sections from the GFS depict 15-
20 ubar/s from the surface to over 500mb combined with a nearly
saturated column moving across far SE CA Saturday night. As such,
widespread showers of light to moderate rain will develop Saturday
night out west, and we have raised POPs to around 80 percent
accordingly. QPF values were also raised based on the dynamical
potential of the approaching low in conjunction with QPF forecasts
from WPC and the GFS/ECMWF.
GEFS ensemble members are in very good agreement through the weekend
with both lows and confidence in the expected weather pattern is
rather high at this time. Rainfall amounts from the southwest AZ
deserts into far SE California will range from one quarter inch to
one half inch. The widespread rains will spread east and into
Arizona during the day on Sunday as the upper low center swings by
along the AZ/Mexican border. At this time, we expect the weather to
come in the form of showers. However, thunder is not completely out
of the question but it appears a bit too stable to warrant
mentioning storms in the forecast at this time. Of course, we are
expecting much cooler high temperatures this weekend given the
influence of the cooler air mass and the considerable
clouds/widespread showers. High temps in the central deserts should
drop into the low to mid 60s Saturday and then into the upper 50s to
low 60s Sunday - well below seasonal normals.
For the early portion of next week - Monday into Tuesday - cooler
and unsettled conditions will remain in the weather picture as a
large area of low pressure develops over the western CONUS centered
north of Arizona. A moist westerly flow will set up across the area
with weak impulses moving quickly through the flow. Given the fact
the the boundary layer remains somewhat moist, we can expect a
persistent slight chance of showers both days over the lower Arizona
deserts with just single digit POPs into the far SE California
deserts. High temperatures remain in the low 60s for the most part
each day over the lower deserts under mostly cloudy skies.
For the latter portion of the extended, Wednesday into Thursday, we
can expect continued cool and somewhat unsettled conditions under
the influence of the large western CONUS upper trof. GEFS ensemble
members become very chaotic and differences develop between the
operational GFS and ECMWF with the GFS wetter and more aggressive
with more disturbances moving through the trof and across Arizona.
We will go with a middle ground and have our POP trends more or less
mirror the NAEFS POP trends, keeping single digit to slight chance
POPs in the forecast where the best precip threats remain over
higher terrain to the east of Phoenix.
A couple of additional mentions: at this time, we do not expect any
significant wind during this unsettled period. It will breezy at
times, but winds should remain well below advisory levels each day.
Also, snow levels remain rather high into early next week; and as
such, we don`t expect any snow issues during the periods of heaviest
QPF. Snow levels do fall well below 5000 feet later next week as
colder air continues to filter in from the northwest, but by then
precip chances are low and as such no snow issues.
&&
.AVIATION...
South-Central Arizona including KPHX, KIWA, and KSDL:
Showers will begin to affect the Phoenix terminal generally staring
in the 02-04Z time frame (somewhat earlier than previous thought),
and persisting into the overnight hours. Confidence is fairly good
that cigs will drop into a 5K-6K ft range with these rain bands.
There may be a brief period of MVFR vsby in any more moderate
showers, but not temporally persistent. Conditions should improve
into higher VFR conditions by late tonight.
Some showers may linger over the eastern parts of the terminal
footprint Saturday morning with clouds/mist leading to at least
partial mountain obscuration. Otherwise, cigs in a 4K-5K ft range
should redevelop Saturday afternoon with partial daytime heating.
Sfc winds will remain rather light, and be quite variable depending
on positioning of shower activity.
Southeast California/Southwest Arizona including KIPL and KBLH:
Showers will clear SE CA terminals by mid Friday evening with 8K-10K
ft cigs becoming more scattered overnight. Some early morning patchy
ground fog could be possible near sunrise, though confidence is far
too low to include in this TAF package. Otherwise, sfc winds will
favor a S/SW component ahead of the next weather system which will
affect these terminals Saturday night.
Aviation discussion not updated for amended TAFs.
&&
.FIRE WEATHER...
Sunday through Thursday:
The second and more potent weather system will make a swift exit to
the east, but lingering trough heights and still moist airmass will
allow for light shower potential over south-central AZ districts and
portions of the Rim/eastern AZ higher terrain through midweek. Much
cooler temperatures will prevail for much of the week, closer to or
below seasonal normals for a change. Unsettled storm pattern will
remain over the western U.S., allowing for cool temperatures and only
modest drying to settle into the districts by midweek. Winds speeds
overall will follow typical drainage and diurnal patterns while
remaining rather light and generally under 10mph.
&&
.SPOTTER INFORMATION STATEMENT...
Skywarn Radio Net activation is not expected this week.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&
$$
Visit us on Facebook...Twitter...and at weather.gov/phoenix
DISCUSSION...MO/Hirsch/CB
AVIATION...MO
FIRE WEATHER...Nolte
For frequently asked questions about the Area Forecast Discussion
visit...
http://weather.gov/saltlakecity/general/afd_faqs.php
Area Forecast Discussion
National Weather Service Tucson AZ
836 PM MST Fri Dec 30 2016
.SYNOPSIS...As the first in a pair of storm systems approaches the
area, valley rain showers and high peaks snow showers are expected
to develop through early Saturday morning. Then a second system will
bring more significant showers and mountain snow late Saturday night
into Sunday. Beyond that, cooler temperatures and a few showers are
possible through much of next week.
&&
.DISCUSSION...
Quite a variety of conditions across the region this evening as very
isolated showers developed and moved through Tuscon shortly after
sunset. While the majority of the metro didn`t see any rain
whatsoever, some locations saw anywhere from a few sprinkles to a
third of an inch. Radar mosaic as of 0330Z continued to indicate
isolated showers north and east of Tucson along with some additional
showers moving into far western Pima Co. These western showers were
associated with an upper low/trough that was slowly making its way
inland and was located over the lower Colorado River.
Incoming 00Z model guidance continues to suggest that showers will
develop across the area late tonight as the upper trough traverses
the state and based upon observational trends to the north and west,
this seems to be playing out as expected. The normally reliable HRRR
is much less enthused about precip chances as the trough moves
through Tucson and points east, but nearly every other available
convective allowing model suggests scattered showers across the
region. As such, I will retain the inherited PoPs and only make
slight adjustments near Ajo where rain will likely be wrapping up
sooner than later. Otherwise the forecast for the rest of the night
looks in decent shape with no significant revisions necessary.
&&
.AVIATION...Valid through 01/06Z.
A bit of a break across the area as of 0330Z however showers will
develop after 06Z with occasional periods of showers affecting TUS
and OLS. Chances at DUG are a bit less. Conditions will improve a
bit during the daytime hours but 5-8kft cigs are likely to hang on
throughout the day at all sites. The previously mentioned system
progged to arrive late Saturday will likely not affect any of the
TAF sites until early Sunday morning, thus it`s too early to
introduce any precip into the forecast. Could be some late day
breeziness across the area, but aviation impacts should be minimal.
Aviation discussion not updated for TAF amendments.
&&
.FIRE WEATHER...An approaching weather system will spread showers
across the region tonight with an outside chance of lightning strike
or two. After a break in the showers Saturday afternoon and the first
2/3rds of Saturday night a second system will spread showers and
mountain snows across the area late Saturday night into Sunday. The
snow level with this system will generally be above 6000 ft with the
bulk of the snow above 7000 ft. Mostly dry weather with seasonable
temperatures is expected Monday through Wednesday. Then there is a
potential for colder air to invade the area late in the week. Other
than a SW breeze Saturday and Sunday no significant winds expected.
&&
.PREV DISCUSSION...
Dry weather continues across most of AZ early this
afternoon with plenty of cloud cover limiting the rise in
temperatures. The first of a pair of storms to affect the region is
just now moving onshore in the vicinity of Los Angeles with a band
of showers entering far western AZ. This entire system will translate
eastward pushing into western NM late Saturday morning. Showers will
develop eastward later this evening...reaching the Tucson metro area
before midnight and the eastern part of Cochise county several hours
before dawn. SPC has us in the Day 1 (12Z-12z) chance of
thunderstorms and looking at the model data there is a small chance
with the system as it rolls across tonight with rather low capes.
Convective allowing high res models indicate there is some potential.
With all that I added a slight chance of storms to the forecast for
tonight. With rather high snow levels and unimpressive QPF would only
expect a few inches of snow across the highest peaks about 8000 ft on
up with 1-4 inches Sky Islands and a bit more over the White
mountains 3-6 inches.
Once this system pushes east early Saturday we will have a relative
break later Saturday until the early morning hours Sunday. With
shortwave ridging passing overhead I dropped pops back to basically
chance mountains and slight chance valleys. With the amount of
moisture we will have available and some low level instability can`t
rule out a shower or two especially north, they will just be rather
limited.
The second system continues to be modeled rather consistently with
the GFS tracking just a tiny bit further south. Precipitation from
this system is expected to hold off till well after the celebrated
midnight hour passes and I adjusted the forecast to account for
that. Basically this is looking like a somewhat weaker version of
the strong frontal system that passed through last week with a bit
more moisture. Based on current timing the associated front should
pass Ajo around dawn, Tucson around 11 am and the eastern border near
sunset with a decent temperature drop following. High temp in tucson
could be around 10-11 am.
The bigger story with this system is the precipitation and the lower
snow levels, that is if the QPF forecast works out and that is
problematic. Model QPF solutions have a very large spread and recent
SREF plumes have dropped back a bit. I tweaked a bit here and there
to account for the above timing/POP thoughts and we remain a bit on
the higher side of median at the moment. Some concern we may be bit
high. With that said going with the idea of 0.10-0.50 inches of rain
in the valleys and 0.75-1.25 liquid equivalent for the mountains
which would be good for the 6-12 inches of snow we have forecast
above 7000 feet for Sunday for the southern mountains and a bit less
over the Whites.
The bulk of the precipitation will fall a few hours either side of
the front and mountain snowfall near the time of the frontal passage
could fall at the rate of 2-4 inches per hour for short periods of
time. Held off on an advisory headline at this time to avoid
confusion with tonights system and earlier mentioned QPF concern.
This system will quickly move east Sunday evening with showers coming
to an end and cooler temperatures settling in.
For the Monday through Wednesday time period a large mass of very
cold arctic air will settle over the northern part of the west and
central part of the country leaving our area in some decent westerly
flow aloft that is a bit moist. hard to rule out a few light showers
or mountain flurries through this time frame so have slight chance
POPs running mainly northern areas. Temperatures near or slightly
below seasonal averages.
Interest then turns toward the end of next week where there is
some potential for some of that cold air to spill south over our
area. Long range models trending in that direction for Thursday
through Friday for a short shot of colder temperatures.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
PUBLIC...Leins/Cerniglia
AVIATION....Leins
FIRE WEATHER...Cerniglia
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