Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/11/18
Area Forecast Discussion
National Weather Service Albany NY
946 PM EST Wed Jan 10 2018
.SYNOPSIS...
An approaching warm front will bring some patchy light freezing
rain tonight, mainly across the southern Adirondacks and Mohawk
Valley region. A brief break in the precipitation is expected
Thursday, before an approaching frontal system from the west
brings periods of rain Thursday night into Friday. As colder
air filters in from the north, rain will gradually change to
sleet and freezing rain late Friday night into Saturday morning,
before ending as some snow later Saturday. Cold and windy
conditions will continue for Sunday.
&&
.NEAR TERM /THROUGH THURSDAY/...
As of 930 PM EST...Precipitation was fairly light moving through
the Mohawk Valley where temperatures were hovering near the
freezing mark. Mesonet observations were into the 20s across the
Dacks and Glens Falls area, however, temperatures were holding
nearly steady elsewhere. Additional showers were evolving around
the SYR-UCA-RME-ART areas which will translate east the next
couple of hours where a coating of ice is expected as wet bulb
processes commence. Did redo the hourly temperatures a bit per
the observations and latest HRRR/RAP 2m temperatures and
dewpoints. Remainder of the forecast looks in good shape at this
time as the 00Z guidance is arriving...
Prev Disc... Mid and high level clouds
will overspread the area late this afternoon and early this
evening ahead of a band of isentropic lift associated with a
warm front approaching from the west. Models including the
latest HRRR are in good agreement that some light precipitation
will break out along the warm front this evening over the Mohawk
Valley and southern Adirondacks with precipitation amounts
generally less than 0.10 inches. Temperatures will be tricky; we
expect a few degree drop around sunset late this afternoon then
temperatures will likely drop another degree or two with
evaporational cooling with the onset of any precipitation later
this evening. This should allow for temperatures to be near or
just below freezing over the northern half of our forecast area
when the precipitation is falling later this evening. The result
will be a little freezing rain over the Mohawk Valley, upper
Hudson Valley and southern Adirondacks this evening into the
overnight hours with ice accumulations of less than a tenth of
an inch. Even if temperatures nudge just above freezing
overnight the very cold ground surface conditions could still
allow for some glazing on untreated surfaces. Based on this we
have gone with a winter weather advisory for a light coating of
freezing rain in NY from the Mohawk Valley northward. Farther
south and east any spotty light glazing should be covered by a
special weather statement. The area from the Catskills east to
NW Connecticut should remain dry tonight with wintry
precipitation passing by to the north.
Most of the precipitation will be north and east of the area
by Thursday morning. Temperatures will climb to the warmest
levels since before Christmas with many locations getting above
40 by afternoon, although cold air may hold tough for awhile
north of the Capital District.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
A slow moving cold front will gradually approach from the Great
Lakes region Thursday night into Friday. Increasing low/mid
level moisture and convergence will promote an increasing chance
for rain later Thursday night, with periods of rain expected
Friday. Moisture should become plentiful, as a combination of
low level Gulf and Atlantic inflow, some of which becomes
entrained from the system off the Florida coast. Rain may become
heavy at times, especially late Thursday night into Friday
morning. A quick one half to one inch of rainfall is possible
during this time. In addition, strengthening southeast to south
winds will bring milder air into the region, especially across
higher elevations. Expect high temperatures to reach the
lower/mid 50s for many areas south and east of Albany, and upper
40s to lower 50s to the north and west, coolest within the
Mohawk Valley region and possibly upper Hudson Valley.
For Friday night into Saturday, the frontal system will slowly
being to settle south and east. Models suggest that shallow
arctic air seeps southward in valley areas first, before
gradually deepening Saturday morning. In addition, another wave
of low pressure will be tracking northward along the frontal
boundary, triggering another surge of moderate to briefly heavy
precipitation. Will have to watch this situation extremely
closely, as there is an increasing potential for freezing rain
for several hours across much of the Hudson River Valley north
of Albany, into the Mohawk Valley region, and adjacent to the CT
River in SE VT. In these areas, there is a possibility of one
quarter of an inch or more of ice accretion before precipitation
transitions to mainly sleet Saturday morning, and snow by early
Saturday afternoon. Across southern areas, mainly rain is
expected, although can not rule out a period of freezing
rain/sleet before precipitation tapers off later Saturday
morning or early Saturday afternoon. Temperatures should fall
into the 20s for most areas near and north of the Mohawk River
by daybreak Saturday, if not even colder, with 30s to lower 40s
to the south. Temperatures should fall during Saturday into the
teens and 20s by sunset.
All areas may be susceptible to a flash freeze situation
Saturday afternoon/evening, as any lingering unfrozen water
on ground surfaces potentially quickly freezes with temps
rapidly plunging into the teens/20s, if not lower in some areas.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
A return to colder temperatures for the remainder of the weekend in
the wake of the storm as we return toward below normal temperatures
once again. There will remain a couple of weak short wave troughs to
migrate through the northeast with a slight chance for snow showers
for the remainder of the weekend.
A period of tranquil weather is in the forecast for later Sunday
night into Monday as a narrow ridge of high pressure and short wave
ridging returns for dry weather but still remain chilly as per the
ensemble MOS shows little variability in the temperature forecast
which keeps it cold with highs mainly into the teens and 20s
throughout the region.
Next PV Anomaly and mid level jet max approaches Monday night from
the Ohio Valley into Tuesday where a period of light snow with weak
isentropic lift along with a weak surface reflection developing
along the I95 corridor or along the mid-Atlantic coastline. The
ECMWF is the most aggressive while the GFS is the most progressive
with minimal impacts.
Temperatures through the period will average below normal throughout
the county warning area.
&&
.AVIATION /03Z THURSDAY THROUGH MONDAY/...
CIGS are thickening and lowering, especially north of KPOU, as
band of precipitation was approaching from the northern I81
corridor. Scattered light showers of rain or freezing rain are
possible tonight after 00z at GFL/ALB/PSF as the warm front
moves across the area, with cigs lowering to MVFR. Thursday will
be dry but mostly cloudy with cigs mainly 3-5 kft. Winds will
be mostly from the south at less than 10 kts today through
tonight, then south-southwest at 5 to 10 kts on Thursday. LLWS
will be an issue as we will continue to mention in the TAFs at
this time for the tonight period.
Outlook...
Thursday Night: High Operational Impact. Definite RA.
Friday: High Operational Impact. Definite RA.
Friday Night: High Operational Impact. Definite RA...FZRA...SLEET.
Saturday: High Operational Impact. Definite SN...FZRA...SLEET.
Saturday Night: No Operational Impact. NO SIG WX.
Sunday: No Operational Impact. NO SIG WX.
Sunday Night: No Operational Impact. NO SIG WX.
Martin Luther King Jr Day: No Operational Impact. NO SIG WX.
&&
.HYDROLOGY...
Based off temperature analysis, river and lake ice is estimated
between 7 and 15 inches thick. As a storm system approaches
from the west, some light freezing rain is expected tonight,
although amounts will generally be light, mainly under a tenth
of an inch of liquid equivalent.
For Thursday into Friday, temperatures will rise above normal
with periods of rain expected for Thursday night into Friday.
The steadiest/heaviest precip is expected on Friday morning,
where locally moderate to heavy rainfall is possible.
Precipitation will continue into Friday night and Saturday
morning, but should start to changeover to a wintry mix or snow
from north to south before ending during the day Saturday. In
total, about 1.50 to 2.50 inches of precipitation is expected
across the area, with the heaviest amounts in southeastern
areas.
The combination of rainfall and snow melt due to the milder
temperatures will allow for river and stream levels to
increase. This increased flows should allow some river ice to
break up and potentially lead to some ice jams and possible ice
jam flooding. In addition, the heavy rainfall may lead to minor
flooding of urban and low lying areas, especially where snow
and ice block drainage. The MMEFS suggest that there even is the
potential for some flooding on main stem rivers, depending on
how warm temps get and just how much rainfall occurs.
Based on these factors, a Flood Watch has been issued for all of
eastern NY and adjacent western New England. Runoff should
start to slow down during the day Saturday into Saturday night
as temps quickly fall and precip ends.
Colder and drier weather is expected for Sunday into early
next week.
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...Flood Watch from late Thursday night through Saturday
afternoon for CTZ001-013.
NY...Flood Watch from late Thursday night through Saturday
afternoon for NYZ032-033-038>043-047>054-058>061-063>066-
082>084.
Winter Weather Advisory until 7 AM EST Thursday for NYZ032-033-
038>043-048>050-082>084.
MA...Flood Watch from late Thursday night through Saturday
afternoon for MAZ001-025.
VT...Flood Watch from late Thursday night through Saturday
afternoon for VTZ013>015.
&&
$$
SYNOPSIS...Frugis/KL
NEAR TERM...MSE/BGM
SHORT TERM...KL
LONG TERM...BGM
AVIATION...MSE/BGM
HYDROLOGY...MSE/Frugis/KL
Area Forecast Discussion
National Weather Service Caribou ME
1039 PM EST Wed Jan 10 2018
.SYNOPSIS...
High pressure will move east tonight. A warm front will slowly
cross the region later Thursday into Thursday night. A strong
cold front will cross the area Friday night through early
Saturday with low pressure moving along the front Saturday.
&&
.NEAR TERM /THROUGH THURSDAY/...
1030 PM Update...
The latest radar loop showed some light precip moving into far
northern and western areas. Most of this was aloft, but some of
the higher returns edging into western Piscataquis County could
be some light snow or sleet. Decided to adjust the timing of the
light snow and mixed precip per the radar. NAM and RAP soundings
as well as the KCAR sounding showed dry below 8k ft but the
column is expected to thicken and lower overnight w/precip
reaching the surface. Kept the Winter Weather Advisory going
into Thursday morning w/the exception of the coast. Temps have
leveled off and are beginning to rise and will continue to do so
overnight into Thursday. A light icing threat is expected
w/this first batch of light precip.
Previous Discussion...
Precipitation will break out after midnight. There is a strong
punch of warm advection in the H850 to H700 layer which means
sleet and freezing rain should be the dominant p-types rather
than light snow. Most of the precipitation will end early
Thursday morning and the amounts will be just a few hundredths
of an inch. The timing affects the morning commute across the
forecast area and will maintain the Winter Weather Advisory. Did
not include the coastal zones as temperatures will be above
freezing most of the night as southerly winds increase, but it`s
still possible the light rain could freeze on cold surfaces
further inland in these zones. Tonight`s lows will occur this
evening...followed by steady to rising temperatures all night.
Temperatures will continue to slowly rise all day tomorrow into
the evening such that Thursday`s high will be at the end of the
afternoon. Measurable precip will end Thursday morning, but the
saturated low levels may generate some drizzle through the day
as the frontal inversion and cloud bases lower. Temperatures
will rise above freezing across the forecast area by late
morning and creep towards the upper 30s and lower 40s by late
afternoon. As dew points rise above the freezing mark in the
afternoon, fog will develop and likely thicken by sunset. A
Dense Fog Advisory will be a consideration by evening.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
A return flow of warmer air will persist across the region
Thursday night in advance of an approaching cold front.
Temperatures will be near steady or slowly rise Thursday night.
Rain chances will begin to increase later Thursday night. The
cold front will approach northwest Maine later Friday. A
disturbance will also lift across the region Friday with an
area of rain. The cold front will begin to cross the region
Friday night, though how rapidly this occurs is still uncertain.
Rain will persist in advance of the cold front. However,
temperatures will rapidly fall in the wake of the cold front.
Precipitation will transition to a wintry mix across much of the
forecast area inland from the coast Friday night, with mostly
snow across northwest areas late Friday night. The transition
to a wintry mix should reach interior Downeast areas late Friday
night. The cold front will move offshore Saturday while an area
of low pressure moves along the front with another area of
precipitation. Precipitation will transition increasingly
toward snow across northern areas Saturday with accumulations
of snow, sleet and ice expected. The transition to a wintry mix
will reach the coast early Saturday. A wintry mix of sleet,
freezing rain and snow is then expected to persist Downeast
through the remainder of the morning and afternoon. Uncertainty
still exists regarding exact precipitation amounts and types
later Friday night into Saturday. High temperatures will occur
early Saturday then fall through the afternoon. With warm
moist air across the snowpack, areas of fog will also develop
Thursday night then persist into Friday night in advance of the
cold front.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
The low will exit across the maritimes Saturday night with
decreasing snow chances north and decreasing mixed
precipitation chances Downeast. High pressure will build toward
the region Sunday with decreasing clouds, along with a chance of
snow showers across mostly the north and mountains. High
pressure then builds across the region Monday with partly sunny
skies. Low pressure could approach from the west later Tuesday
with increasing clouds and a chance of snow late. The low should
then track south of the region Wednesday with a chance of snow
or snow showers, particularly Downeast. Temperatures should be
at near normal levels Sunday, with below normal level
temperatures expected Monday through Wednesday.
&&
.AVIATION /03Z THURSDAY THROUGH MONDAY/...
NEAR TERM: VFR conditions will prevail through this evening
with the possible exception of BHB where some MVFR cigs are
expected. LLWS will develop tonight. Late tonight, all terminals
will become MVFR due to cigs and vis in freezing rain/drizzle.
The freezing rain and drizzle will end Thursday morning across
the area, but IFR cigs will take its place. VLIFR cigs are
possible by late afternoon with drizzle.
SHORT TERM: IFR/LIFR, with occasional VLIFR, conditions are
expected Thursday night into Saturday. MVFR/IFR conditions are
expected Saturday night. Occasional MVFR conditions are
expected across the region Sunday, particularly across the north
and mountains. VFR conditions are expected across the region
Monday. Precipitation will be in the form of rain Thursday night
into Friday. A wintry mix will then begin to transition to snow
across northern areas Friday night, with a wintry mix starting
to develop late Downeast. Snow or a wintry mix is expected
across northern areas Saturday, with a wintry mix Downeast. Fog
will also be a concern Thursday night into early Saturday.
&&
.MARINE...
NEAR TERM: Will extend the SCA through Thursday night. Have some
concerns about near gale conditions tonight, but will reference
a few gusts to 35 kts for tonight and early Thursday morning
rather than upgrading the headline. There is decent mixing over
the waters until Thursday afternoon when the stability sets in
and fog begins to materialize.
SHORT TERM: Gale conditions are possible Friday. Otherwise,
small craft advisory conditions are expected Thursday night then
again Friday night/Saturday. Visibilities will be reduced in
rain and fog Thursday night through early Saturday, with a
wintry mix expected later Saturday.
&&
.CAR WATCHES/WARNINGS/ADVISORIES...
ME...Winter Weather Advisory until noon EST Thursday for MEZ001>006-
010-011-015>017-031-032.
MARINE...Small Craft Advisory until 7 AM EST Friday for ANZ050>052.
&&
$$
Near Term...Hewitt
Area Forecast Discussion
National Weather Service Charleston SC
1006 PM EST Wed Jan 10 2018
.SYNOPSIS...
A coastal trough will shift inland tonight and Thursday. A cold
front will move through Friday afternoon and evening, followed
by a secondary front Saturday night. Cool high pressure will
settle over the area Sunday through much of next week.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Opted to nudge overnight temperatures up a degree or two for
most areas per going trends. The rest of the forecast is on
track.
Weak isentropic lift is occurring across the offshore coastal
trough and atop the inland high pressure wedge this evening.
This is supporting some very light showers and patchy drizzle
for some spots. The strongest lift is currently situated off
the Florida east coast where more substantial shower activity is
occurring. The northern fringe of this area of lift will move
into Southeast Georgia overnight bringing a slightly better
chance for measurable rainfall. Readjusted the axis of highest
pops (up to 40%) into Southeast Georgia for this reason. The
risk for some patchy fog and drizzle will continue through the
night, but dense fog appears unlikely. Lows from the mid 50s
north to upper 50s south look on track.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/...
High pressure will linger east of the Northeast states on
Thursday. Meanwhile, a closed upper low over eastern Florida
will lift northwest as it merges with an approaching longwave
trough. As a result, the coastal trough over our waters will
shift inland late Thursday morning. Moist, isentropic ascent
will overspread the forecast area from the southeast during the
day. The strongest forcing and moisture advection will be over
inland SC/GA on Thursday, shifting into interior SC late
Thursday afternoon through Thursday night. This is where we have
the highest PoPs. Despite extensive cloud cover throughout the
day, strong low-level warm advection is expected to push
Thursday high temperatures into the low 70s. Fog is expected
Thursday night, likely due to stratus build-down.
The upper longwave trough will weaken and lift northeast as it
approaches the Eastern U.S. on Friday. An associated surface low
will shift into western NC while a cold front approaches the
local area. With surface temps rising into the mid 70s and
dewpoints in the mid 60s, model data indicates the potential for
marginal surface-based CAPE during the afternoon. Fairly
widespread showers expected to move in during the afternoon,
sweeping through the area Friday evening. We maintained mention
of a slight chance for thunderstorms as well.
Cold, dry air advection will occur Friday night into Saturday.
Highs on Saturday will be considerably cooler than Friday in the
50s.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
Models are in fairly good agreement in the long term period. High
pressure will build into the region on Sunday and persist into early
next week. A weak cold front could cross the area on Tuesday.
Overall, the period looks to be dry with temperatures a bit cooler
than normal.
&&
.AVIATION /03Z THURSDAY THROUGH MONDAY/...
Primary concern:
* cigs
Similar to last night, it appears guidance is being too
aggressive in the development of widespread IFR and LIFR cigs
tonight. Generally favored the RAP soundings, which keep the
axis of deeper moisture situated across Southeast Georgia
through daybreak. Will show low-end VFR cigs prevailing at KCHS
with just a TEMPO group for MVFR cigs roughly 11-14z. At KSAV,
the risk for sub-VFR cigs will be higher. Will show prevailing
MVFR through about 10z with MVFR cigs prevailing 10-14z with a
return to VFR thereafter. Could see a brief period of IFR just
before sunrise, so a TEMPO group will be included for high-end
IFR cigs (but above alternate minimums) 11-14z.
Extended Aviation Outlook: Flight restrictions likely Thursday
through Saturday morning due to low ceilings and restricted
visibilities.
&&
.MARINE...
Tonight: Winds will remain elevated a tad given the pressure
gradient between high pressure to the north and weak low
pressure to the south. Seas have been running a bit above
guidance and so we have raised Advisories for the southern SC
waters and northern GA waters as a result of 6+ ft seas, mainly
comprised of swells.
Thursday through Monday: Persistent southeast winds on Thursday
will weaken slightly as directions turn to the south and the
coastal trough shifts inland. However, strengthening southerly
winds expected on Friday ahead of a cold front. Winds will turn
offshore late Friday night but remain fairly strong into
Saturday as cold air advection occurs over the waters and high
pressure builds in. Small Craft Advisories continue for all
waters except Charleston Harbor into Thursday night, then linger
for the Charleston County near shore waters and GA offshore
waters through much of Saturday due to higher seas.
All waters expected to be advisory-free by Saturday night. High
pressure will build into the region the remainder of the
weekend and persist into early next week.
Sea fog: Conditions will become favorable for sea fog as a warm and
moist airmass develops over the abnormally cold shelf waters. Sea
fog could develop as early as late tonight and then persist
into Friday. Marine Dense Fog Advisories may eventually be needed.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...Small Craft Advisory until midnight EST Thursday night for
AMZ352.
Small Craft Advisory until 7 PM EST Saturday for AMZ374.
Small Craft Advisory until 4 PM EST Saturday for AMZ350.
Small Craft Advisory until 4 PM EST Thursday for AMZ354.
&&
$$
Area Forecast Discussion
National Weather Service State College PA
1007 PM EST Wed Jan 10 2018
.SYNOPSIS...
High pressure will drift east and off the New England coast
overnight. A frontal system will approach by Friday and move
through the region early Saturday. Very cold air will return to
the area for the weekend lasting into at least the beginning of
next week.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
The HRRR shows just the chance of a light shower or some drizzle
over the north, mainly later tonight through sunrise, with the
remainder of the CWA staying dry under slowly increasing clouds.
Some breaks in the clouds over the eastern half of the CWA, and
winds becoming generally light from the south or SE tonight
will allow temps to dip to around freezing for a low.
Across the higher terrain of NW PA and the Laurels, a light to
moderate southerly breeze should combine with the clouds to
keep temps several degrees warmer than our eastern zones.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/...
a better surge of moisture and rapidly deepening cloud deck
pushes NE into the region later Thurs afternoon and evening.
Will maintain POPs AOB 30 pct for the most part during the day
Thursday, with the best chance for a few hundredths of an inch
of light rain occurring near and to the North and West of KBFD.
Temps should rise nicely under the influence of south to SE
flow and strengthening low to mid level WAA. The cooler air near
the surface air may be tough to get rid of (especially in the
eastern valleys). However, 925mb temps do climb to near +10C.
So, we need to keep a sharp eye out for any periods of enhanced
vertical mixing, which would lead to a big bust (being too
cool) on temps.
Max temps are predominately in the mid to upper 40s, though the
higher terrain near and to the west of route 219 could see the
mercury jump at least into the low 50s.
&&
.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
*Localized risk for poor drainage and ice jam flooding into the
weekend
*Late-week storm to bring mixed precipitation with heavy
snow/significant ice threat focused over NW Pennsylvania
*New shot of arctic air behind the late week storm will
support below normal temperatures into early next week
Ensemble guidance shows H5 heights building over much of the
Eastern U.S supporting January thaw/mild spell through Friday.
Southern stream shortwave emerging from split-flow trough over
the Central U.S. will lead to surface low development over the
southern Plains into the Lower MS Valley on Thursday. This low
and attendant frontal system will strengthen as it lifts
northeastward along/east of the Appalachians across the
northern Mid-Atlantic states to the New England coast Friday
and Saturday. By the end of the weekend, troughing will once
again be established across the Eastern U.S. with shot of
arctic air supporting below average temperatures into early
next week.
Winter weather details associated with the late week storm
system are starting to come into focus. Issued winter storm
watch for Warren and McKean Counties given increasing risk for
significant/heavy snow and ice Friday night into Saturday. Thermal
profiles will be the key to the forecast concerning ptypes
which will dictate how much snow/ice falls. Arctic air will
continue to wrap southeast and undercut the warm layer aloft,
which will foster precipitation northwest of the low track to
transition from rain to freezing rain, then to a period of sleet
and ultimately snow as the cold air deepens through the column.
Anticipate a ptype transition to progress southeast with time
with a period of ice then snow advancing to the I-81 corridor by
Saturday afternoon. Temperatures should drop below freezing
rather quickly which raises the concern for rapid freeze-ups on
untreated surfaces. Minimum wind chills will drop into the
positive and negative single digits Saturday night into Sunday.
A drastic temperature swing is expected with temperatures
falling 40-50 degrees between Friday`s highs and Sunday night`s
lows.
Cold but tranquil weather to start next week with some light
snow possible into Tuesday with weak clipper type system.
&&
.AVIATION /03Z THURSDAY THROUGH MONDAY/...
A bkn-ovc shield of VFR to MVFR Stratocu (topped by some alto
cu) will continue to drift east acrs the commonwealth overnight.
MVFR will continue at BFD overnight. Overall, looking at mainly
dry conditions. Perhaps some patchy light drizzle tonight and
thursday...mainly across the northern and western mtns of the
state.
LLWS was included at KBFD late tonight through at least 18Z
Thursday as the eastern edge of a swrly Low-Level jet of 40-45
kts moves over NW PA.
As moisture drifts from the southeast, conditions will continue
to degrade late Thursday afternoon and through Thursday evening.
This will drop cigs and vsbys from the Southeastern TAF sites
and spreading westward. This will bring MVFR to IFR cigs and
vsbys Thursday night into tomorrow.
Outlook...
Thu night...Period of rain/low cigs likely.
Fri...Periods of rain/low cigs possible. A change to freezing
rain or sleet is likely across the NW Mtns of PA late Friday,
then Sleet and Snow Friday night.
Sat...Rain/low cigs possible across the Susq Valley. Mixed
precip or snow (with IFR to LIFR Cigs and Vsbys) tapering off
by the early afternoon.
Sat night and Sunday...Windy and much colder with areas of IFR
cigs and vsbys in frequent snow showers across the NW mtns and
Laurel Highlands (KJST to KBFD), and more brief IFR to MVFR in
isolated to sctd snow showers elsewhere.
Monday...VFR with morning sunshine followed by increasing
afternoon clouds.
&&
.HYDROLOGY...
A brief January thaw with mild temperatures is expected through
Friday. Despite low streamflow levels, the warm surge combined
with melting snow and periods of rain will support a localized
risk for poor drainage and ice jam flooding through the weekend.
Another shot of arctic air with very cold temperatures may
reinforce ice jams into early next week.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
Winter Storm Watch from Friday afternoon through Saturday
afternoon for PAZ004-005.
&&
$$
SYNOPSIS...La Corte
NEAR TERM...La Corte
SHORT TERM...Dangelo
LONG TERM...Steinbugl
AVIATION...Lambert/Ceru
HYDROLOGY...
Area Forecast Discussion
National Weather Service Des Moines IA
943 PM CST Wed Jan 10 2018
.UPDATE...
Issued at 937 PM CST Wed Jan 10 2018
Have adjusted max snow axis and made some minor headline changes
to account for persistent south and east shift in heavy snow axis
as depicted by 18z and new 00z guidance. Confidence remains low
however even as the event nears with a fairly wide range in model
spread. The latest NMM core suite of the NAM, NAMNest and HRW-
NMM are all fairly similar placing the max axis along a
Greenfield/Boone/Charles City line. However the unsettling 02z RAP
and HRRR runs are even more aggressive than that, going to the
southeast Des moines metro with the axis. Thus the evening update
is hopefully headed in the right direction with a few warning
counties added to better fit the 4 inch snow amount as mentioned
below and attempt to blend into adjacent offices for a consistent
WWA map. Although amounts have dimnished on the NW side of the
warning, 2 to 4 inch amounts may still occur with considerable
blowing and drifting and significant travel impacts. Further
changes in amounts and headlines with the midnight packages may
very well occur too, hopefully with better model consensus.
&&
.SHORT TERM.../Tonight through Thursday/
Issued at 410 PM CST Wed Jan 10 2018
The primary forecast challenge remains the winter storm that
will impact the area late tonight into Thursday. Areas of fog
will continue over northern Iowa through this evening with then
the lowest visibilities due to fog will be situated just ahead of
the surface cold front as it moves southeast into Iowa.
Visibilities may drop near to below one quarter mile at times. As
of now, an SPS likely will be able to handle the situation if
visibilities do drop.
An area of low pressure continues to organize and deepen over
southeast Colorado this afternoon as a vigorous short wave/PV
anomaly moves across Arizona and New Mexico. This system will
eject northeast tonight through Texas and Oklahoma and be over
eastern Kansas by 12z Thursday. A surface low pressure will
accompany the system as it lifts north through eastern Iowa. A
deformation band of snow will develop along the western edge of
the low pressure track late tonight into Thursday morning. This
deformation band will have strong forcing through the dendritic
layer with higher snow ratios of 12-15 to 1 expected and snowfall
rates exceeding 1 inch per hour at times. Expecting a band of 4 to
6 inches of snow, which could potentially become higher should
the deformation band maintain a steady position. General trends
continues to be a more easterly from near Mason City southwest
through Audubon. In addition, a strong push of Arctic air will
arrive as a cold front sweeps through the state. This boundary
will bring strong northwest winds of 20 to 30 mph with gusts
approaching 35 to 40 mph. A strong inversion above 900 mb will
limit the overall mixing potential with peak mixed layer winds in
the low to mid 30s kts. The strong cold advection will enhance the
momentum transfer of winds so much of this should be realized at
the surface. A brief period of stronger pressure gradient and
higher pressure rises will move east through Iowa between 09-18z
and may enhance winds further. At this time, expect significant
blowing and drifting of snow that may create significant travel
impact but conditions should remain below blizzard criteria. Have
upgraded a large portion of the watch to Winter Storm warning
based on expected impacts and generally outlined an area with 4+
inches of snow combined with the winds. The snow will diminish
during the afternoon though low level temperatures will drop
within the dendritic layer by the afternoon and may keep light
snow going.
Finally, warm temperatures in the 30s to 40s ahead of the
precipitation may cause wet conditions initially as precipitation
begins as rain or a wintry mix before transitioning to snow in
addition to snow melting until pavement temperatures lower. The
arrival of the Arctic air with temperatures falling into the teens
by mid morning will cause flash freezing of any wet surfaces and
may cause very icy conditions. Due to the flash freeze potential
and expected wintry mix over central Iowa, have added a Winter
Weather Advisory along the southeast periphery of the warning. An
additional expansion to the southeast maybe required should an
icing potential develop. Finally, wind chills will fall to near 20
below zero over northern Iowa by the afternoon then expand south
to near Highway 30 overnight. Likely will need wind chill
headlines once the current headlines expire.
.LONG TERM.../Thursday night through Wednesday/
Issued at 410 PM CST Wed Jan 10 2018
Cold temperatures will persist through much of the forecast period
as strong northerly flow continues through at least Tuesday. This
will lead to several periods with wind chills dropping to 20 below
zero or less each night. Two strong short waves to watch arrive
Friday night and Sunday afternoon and night. Light snow is
possible with the Friday night system and at this time looks to
have minimal impact. The Sunday/Sunday night system may have a
bigger impact as a stronger system arrives. This system will
feature a deep dendritic layer from near the surface to around 13
kft. This system may produce a widespread 1 to 3 inches of snow.
In addition gusty northwest winds may produce additional impacts.
&&
.AVIATION.../For the 00Z TAFS through 00Z Thursday evening/
Issued at 554 PM CST Wed Jan 10 2018
VFR conditions had lifted northward to essentially Interstate 80
by 00z but MVFR to LIFR conditions persisted farther north. These
conditions are expected to changed little through the evening but
IFR/LIFR conditions will become more widespread to the south and
east as a cold front begins moving through the state and
precipitation begins. The precipitation should initially be rain
but transition to a FRZA/PL mix before switching to all snow area
wide into midday. This will be followed by gusty NW winds to
25-35kts and considerable blowing snow in areas with appreciable
accumulations. At least MVFR conditions due to ceilings and/or
blowing snow should persist through 00z.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 6 AM to 6 PM CST Thursday for
IAZ027-028-038-039-048-049-059>061-071>074-081>084-092>095.
Winter Storm Warning from 3 AM to 6 PM CST Thursday for
IAZ005>007-015>017-023>026-033>037-044>047-057-058-070.
Winter Weather Advisory from 3 AM to 6 PM CST Thursday for
IAZ004.
&&
$$
UPDATE...Small
SHORT TERM...Donavon
LONG TERM...Donavon
AVIATION...Small
Area Forecast Discussion
National Weather Service Grand Forks ND
709 PM CST Wed Jan 10 2018
.UPDATE...
Issued at 705 PM CST Wed Jan 10 2018
Forecast on track so no changes. Continue to monitor short term
trends. Heaviest snow area Grand Forks to Bismarck via
radars...and moving NE. Within this band snowfall rates 1/2 to 1
inch per hour. But with winds, so difficult to measure. Highest
winds in the RRV as anticpated as there is a favorable 340-350
degree wind. Gusts to 35-40 kts at GFK for the highest. DVL basin
not as bad and thus vsbys more like 3/4 to 1SM vs the 1/4 at GFK
and CKN. So overall the blizzard vs warning area working out well.
As we go thru the evening issue will be snow into NW MN (esp TVF)
where advisories are out and possiblity exists for 6 inches of
snow (on high end) and need to upgrade to warning. Right now
though the latest HRRR indicates a general snowfall in NW MN with
not quite as high rates but close call to warning criteria. Also
Fargo area Snow moving in and winds there gusty as well...will see
how things evolve to see if upgrade to Blizzard is needed there.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 340 PM CST Wed Jan 10 2018
Confidence in snowfall totals, wind speeds, and winter weather
impacts has increased enough to have a pretty good idea of what is
going to happen. Current conditions indicate a band of snowfall
from central North Dakota extending into the northern Red River
Valley related to mesoscale forcing being aided by synoptic scale
forcing. Latest CAM/High Resolution guidance indicates QPF totals
within this band of 0.40 to 0.60 inches, which would lead to an
area of 5 to 8 inches of snow (given stronger winds snow ratios
should be toward the lower end of the spectrum). Given the forcing
mechanisms involved, trust these models and will increase snowfall
totals into this range (expanded the winter storm warning
westward). Will need to monitor observations and incoming guidance
for the eastern extent of this heavier snowfall. The strongest
synoptic forcing will move through the region by this evening
which will then spread lighter QPF into the SE ND and west
central MN, although snowfall amounts will be less compared to the
northern areas.
Winds and blowing snow the other concern. Issued a blizzard
warning for the area that will experience the strongest winds and
heaviest snowfall (central/northern Red River Valley). Before the
snow started the current winds were already causing patchy areas
of 1/4 mile visibility. The coverage of these conditions has
deteriorated as the snow has begun to fall. As the snow continues
to accumulate, expect these conditions to further deteriorate.
Wind speeds expected to be 25-30mph with gusts to 35-40mph, which
will likely mean more of an open country type blizzard. Will need
to monitor other areas, but thinking is that either wind speeds or
snowfall amounts will limit the blowing snow impacts to near
blizzard conditions in open country (areas that are currently
winter storm warning). Conditions will improve after sunrise
tomorrow.
.LONG TERM...(Thursday night through Wednesday)
Issued at 340 PM CST Wed Jan 10 2018
In the wake of the mid week snow and wind event, Arctic air will
continue to build into the Northern Plains. High pressure overhead
Fri night will offer optimum radiative cooling conditions and
resultant low temps colder than 20 below throughout the forecast
area. This will bring apparent temps close to 40 below even as wind
speeds remain at 5 mph or lower. Some warm air advection Sun will
allow for daytime highs edging over the zero degree mark as a trough
swings down within the NW flow aloft. Then back to frigid weather
and more dangerous apparent temp values for Sun night through Mon
night.
Two systems with migrate through the NW flow through the weekend.
The first round is slated for Fri and a southerly track is First
still favored as guidance products converge to this solution. This
will be followed by a second instance of potential snowfall for Sun,
associated with the previously mentioned upper trough and modest
warm air advection. Light accumulations would be the most likely
result. By Wed western ridging will edge closer to our area, bumping
temps up toward or beyond seasonal expectations.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 705 PM CST Wed Jan 10 2018
For most areas IFR conditions thru the night, worst at GFK, as
snow system moves through. IFR either with vsby or ceilings.
Conditions will improve gradually Thursday daytime. Gusty north
winds 20-35 kts, highest in the RRV.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...Winter Storm Warning until 9 AM CST Thursday for NDZ007-014-015-
024-026-028-038-039-049-052>054.
Blizzard Warning until 9 AM CST Thursday for NDZ008-016-027-029-
030.
Winter Weather Advisory until 9 AM CST Thursday for NDZ006.
MN...Winter Storm Warning until 9 AM CST Thursday for MNZ003-029.
Winter Weather Advisory until noon CST Thursday for MNZ005-006-
008-009-013>017-022>024-027-028-030>032-040.
Blizzard Warning until 9 AM CST Thursday for MNZ001-002-004-007.
&&
$$
UPDATE...Riddle
SHORT TERM...TG
LONG TERM...WJB
AVIATION...Riddle
Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
638 PM CST Wed Jan 10 2018
.AVIATION...
/00Z TAFs/
Several forecast challenges this cycle, with the immediate issue
being the resumption of MVFR/IFR conditions at the TAF sites this
evening/overnight. A large swath of MVFR ceilings currently
extends from the Bonham/Paris area southward to Corsicana and
Palestine. Scattered elements of this cloudiness already encompass
part of the Metroplex, and expect MVFR conditions to redevelop in
the 03-05z timeframe as low level moisture advection and
isentropic lift proceed.
Went ahead and included a period of IFR ceilings at KDAL and KACT
from around 09-15z, closer to the deeper moisture feed that will
exist across central and eastern Texas by daybreak Thursday. In
keeping with the latest HRRR and SREF solutions, believe there`ll
be a marked east-west gradient of low cloudiness overnight. I was
not confident about including any IFR conditions from KDFW/KGKY
westward. As surface low pressure intensifies across the Texas
Panhandle overnight, south winds of at least 15 knots (and perhaps
higher) will persist across North and Central Texas.
Stayed pretty close to the latest HRRR/3km NAM guidance on the
timing of Thursday`s frontal passage, with 16-17z being the
estimated time period for FROPA in the Metroplex. The wind shift
at KACT should occur around 18z. Winds at all locations will veer
to a southwesterly direction for a few hours Thursday morning
prior to FROPA, with a sharp swing to the northwest at speeds of
25 knots once the front passes. We could briefly see some
crosswind issues at KDFW in the 17-20z timeframe if post-frontal
winds jump up in speed yet don`t veer as much as expected. By
mid-afternoon, wind direction should be in the 320-330 degree
range, which should preclude significant crosswind problems.
Still see a relatively brief, yet robust period of mid-level lift
associated with the strong shortwave that will be transiting the
region tomorrow afternoon. This in turns still suggests the
possibility of some brief scattered snow showers, or a mix of
sleet and snow, across the far northwestern and northern counties
of Texas Thursday afternoon. While it`s not out of the realm of
possibility that a few flakes or sleet pellets could reach the
I-20 corridor and the Metroplex TAF sites, confidence is not high
enough at this time to include a mention of these precipitation
types in the 00z TAFs. This will need to be monitored closely for
possibly inclusion with later packages, however.
Steady improvement in ceilings should occur from west to east
across the region after 23z Thursday, with some VFR conditions
likely developing area-wide by the evening hours. North winds will
remain quite strong, however, averaging 20-30 knots with higher
gusts.
Bradshaw
&&
.SHORT TERM... /Issued 340 PM CST Wed Jan 10 2018/
/Tonight through Thursday Night/
An upper level trough located to our west will swing through the
Southern Plains tonight through Thursday night bringing notable
weather changes to the region. The surface low currently in
southeastern Colorado will move southeast overnight, and this will
maintain breezy south winds tonight. With the aid of the breezy
south winds, low level moisture will continue to increase,
especially across the eastern half of the region. In these areas,
dense cloud cover will prevail and temperatures are expected to
remain nearly steady and/or rise some overnight. Across our
western counties, where clearer skies are expected, temperatures
will fall into the mid and upper 40s.
As the lead impulse within the upper level trough moves northwest
of the region this evening, some light rain may occur in our far
northwestern counties. In addition, with the help of warm air
advection overnight, some patchy drizzle may occur east of
Interstate 35/35E after midnight. With the breezy winds, do not
think there will be much of a fog potential, but light fog may
occur east of Interstate 35/35E where better moisture advection is
expected, and in particular where drizzle/mist may be observed.
The lead disturbance within the trough will move north of the
region by daybreak, with a secondary disturbance dropping across
the state during the day Thursday. A strong cold front will enter
our CWA from the northwest in the morning hours and proceed
southeast through the day, exiting the region by mid afternoon.
Falling temperatures and very strong winds are expected behind the
front. Sustained winds of 20-30 mph, possibly higher in some
places, with wind gusts up to 40-45 mph will occur behind the
front. Have hoisted a Wind Advisory for all but our southeastern
counties from 9 AM-Midnight. This advisory could have been piece-
mealed with various start times as the front progresses through
the area, but the main message is it will be very windy tomorrow,
on top of turning much colder!
The cold and blustery conditions on Thursday and Thursday night
will be the main highlight for all of North and Central Texas, but
many people are likely more excited for the wintry mix potential.
I`ll start out by saying any accumulations are expected to be
very minor with very little, IF ANY, in the way of travel impacts.
However, temperatures behind the front will likely fall into the
lower 30s Thursday afternoon north and northwest of the DFW
Metroplex, and this is where there could be minor accumulations
and impacts. It is possible the howling winds may cool elevated
and exposed surfaces enough for some slick spots on roads the area
northwest to north of the DFW Metroplex.
An in depth analysis of soundings, frontogenesis, lift, humidity,
instability and more continue to suggest the most likely location
of wintry precipitation is northwest of the DFW Metroplex.
However, based on the latest data, I did expand the mention of a
sleet and snow mix to north of a Goldthwaite to Hillsboro to
Athens line, and also extended the mention into the evening hours.
The sleet mention was retained during the afternoon hours before
the column cools completely below zero supporting a transition to
all snow, but surface temperatures will likely still be above
freezing and most of this sleet should melt. Whether the frozen
precipitation occurs in small bands, or as a larger coverage
area, we may not know until the event unfolds, but this is a fast
moving system, and we do not expect the sleet/snow to last more
than a few hours at any one particular location. Where surface
temperatures remain above freezing, most of the frozen
precipitation will melt, but the strong winds may also have a
factor in potential minor accumulations. Again, we do not expect
significant impacts from this event!
Thursday night will be a cold and breezy night with low
temperatures in the 20s. Wind chill values will be in the teens
Friday morning. If anyone wants to wrap outside pipes, today or
tomorrow before the front is the best time to complete that task.
JLDunn
&&
.LONG TERM... /Issued 340 PM CST Wed Jan 10 2018/
Fairly tricky forecast in today`s extended periods, with dry and
cool weather occurring first, followed by additional changes next
week. Friday through Sunday, the weather will be relatively quiet.
Temperatures will be below normal, as highs will remain in the 40s
during the afternoon hours, while overnight lows will also be
below normal. However, the weekend is expected to remain dry.
By Monday, the moisture will be slowly creeping back into north
and Central Texas, and rain chances return to the forecast late
Monday and into Tuesday morning. During nearly any other time of
year, this would be your typical 20-30% chance of rain. However,
with temperatures dropping near and below 32 degrees, this does
introduce the changes for a few hours worth of light rain or light
freezing rain during the overnight hours. The chances for rain
remain Monday night and Tuesday, and return again on Wednesday.
The mid week precipitation chances are far from certain, however.
The ECMWF is suggesting a slightly stronger short wave trough
moving across North Texas on Wednesday than the GFS. While the
deterministic GFS remains dry, about half of the GFS ensemble
members suggest some sort of precipitation during the middle of
next week. Have therefore kept at least a slight chance of rain
mentioned for Tuesday/Wednesday. Expect this to change somewhat as
the details get ironed out over the next few days.
Fox
&&
.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth 54 54 28 45 27 / 10 30 30 0 0
Waco 55 58 28 50 28 / 10 10 10 0 0
Paris 52 59 23 43 25 / 10 30 20 5 0
Denton 51 52 24 45 25 / 10 30 30 0 0
McKinney 52 56 25 44 25 / 10 30 30 0 0
Dallas 54 56 27 46 27 / 10 20 30 0 0
Terrell 54 60 26 45 25 / 10 20 20 0 0
Corsicana 54 61 27 45 27 / 10 20 10 0 0
Temple 55 60 29 51 29 / 10 10 5 0 0
Mineral Wells 47 47 25 48 24 / 10 30 20 0 0
&&
.FWD WATCHES/WARNINGS/ADVISORIES...
Wind Advisory from 9 AM Thursday to midnight CST Thursday night
for TXZ091>095-100>107-115>123-129>135-141>146-156>159.
&&
$$
Area Forecast Discussion
National Weather Service Grand Rapids MI
937 PM EST Wed Jan 10 2018
LATEST UPDATE...
Update
.SYNOPSIS...
Issued at 330 PM EST Wed Jan 10 2018
Warmer air surging into the area over the snowpack will continue
to create areas of fog into Thursday. The fog may become dense in
some locations late today and tonight. Drizzle will also persist
through the night, while temperatures rise. Breezy and very warm
conditions are expected on Thursday, with high temperatures
reaching into the 50s. Rain is also likely ahead of a cold front.
The front will then push through the area Thursday night, changing
rain to snow. Accumulations Thursday night into Friday are
expected to remain less than an inch.
&&
.UPDATE...
Issued at 937 PM EST Wed Jan 10 2018
I made two changes to our ongoing forecast. I have expunged the
eastern 2/3rd of our fog advisory on a diagonal from near
Kalamazoo to Evart. I also increased our forecast high to the mid
to upper 50s based on how our current temperature has already
reached the upper 40s at GRR and that matches the ECE mos with
gives GRR a high of 59 Thursday.
As for the fog advisory, both the HRRR and RAP model visibility
forecast and CONSHORT in GFE show the area of lowest visibilities
lifting north with time through midnight, then after midnight is
seems a marine layer seems to come in and lower temperatures
so an area west of a line from Kalamazoo to Evart have air
temperatures in the lower to mid 40s while area east of that after
midnight are in the mid 50s! So, since those models are doing
nicely now, I am assuming that they will continue to do well. This
would lead to fog reformation. Which is why I am holding onto the
fog advisory.
It should be pointed out that the HRRR does have air temperatures
in the mid to upper 50s east of US-131 Thursday afternoon. This is
also supported by my 1000/925 mb thickness tool temperature
forecasts.
Bottom line is most of the snow on the ground, over most of our
CWA will be gone by Thursday evening. Areas close to Lake
Michigan, where it does not get quiet so warm Thursday and there
was more snowfall in the first place, some of the snow is likely
to remain on the ground there.
&&
.SHORT TERM...(This evening through Friday night)
Issued at 245 PM EST Wed Jan 10 2018
Deep southerly flow stretching from the Gulf of Mexico through the
Great Lakes will persist through Thursday in advance of an
amplified upper trough that spans much of central North America.
This will keep us in a persistent pattern of warm air advection
dominated by drizzle, fog, and mild temperatures. Freezing
temperatures are not expected until Thursday night, and no further
ice development is expected on roads. Main concern will be
visibilities as 40+ degree dewpoints over extreme southwest
Michigan and Indiana seep further north tonight and Thursday. The
high dewpoint/warmer air flowing over the snowpack and frozen
ground may create areas of dense fog later today and tonight, and
cannot rule out an advisory being needed. Temperatures are
expected to warm through the night, with areas of drizzle
persisting.
Better surge of moisture (PW values reaching near an inch) will
occur tomorrow ahead of a cold front and as the upper trough moves
closer. Breezy conditions and a weaker inversion should allow some
more warmer air moving in aloft to be realized, even with the
snowpack, and expect to see temperatures rise into the low/mid
50s. Best chance for rain showers tomorrow will be during the
afternoon and through the evening in advance of the cold front.
Model cross-sections are indicating a little convective
instability, but lapse rates do not look too strong on forecast
soundings, so left thunder mention out of the forecast. Cannot
rule out an isolated rumble of thunder however ahead of or along
frontal passage. Cold front will sweep through during the very
late evening and early overnight hours, allowing rain to change
to snow. There is a small chance for a brief changeover to
freezing rain, but impacts should be mitigated by wet and warm
roads. Snow accumulations behind the front look to be less than an
inch before drier air arrives and sweeps the DGZ of ice crystals.
Colder temperatures are expected Friday/Friday night. Northerly
flow looks to limit coverage of lake effect snow, while inversion
heights around H850 and lake-H850 temperature differences remain
in the teens. This should keep any snow that does fall along the
immediate lakeshore light.
.LONG TERM...(Saturday through Wednesday)
Issued at 245 PM EST Wed Jan 10 2018
Arctic air dominates the weekend into next week with 850 mb temps in
the minus 15C to minus 20C much of that time. Saturday morning could
start off colder than guidance if northerly flow allows any
clearing. Lake effect snow showers are expected to gradually move
onshore by Sunday as the flow goes more westerly.
A clipper moving through Monday and Monday night will bring the
potential for some widespread snow but accums will be limited by
quick moving storm and the DGZ being close to the ground.
Lake effect snow showers in northwest flow following the clipper
will taper off on as sfc ridging builds in on Wednesday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 640 PM EST Wed Jan 10 2018
The good news is temperatures are well above freezing and will
stay that way though 00z Friday. Otherwise expect IFR or LIFR
ceilings and visibilities through 00z Friday. Scattered rain
showers are expected, some this evening, but mostly Thursday
during the day. The greatest concentration of rain showers will
be north and west of Grand Rapids through 21z Thursday. After that
an are of showers assoicated with the cold front will move east
across the CWA. Visibilities may go up briefly during rain some of
the rain showers but will go back down once the shower passes
through.
There will also be a considerable amount of wind shear for the
next 24 hours. Between 10000 ft agl and 2000 ft agl winds will be
in the 45 kt to 55 kt range through 00z Friday. Surface winds
only 15 to 25 knots, which of course creates the low level wind
shear. The good new there is the direction of the wind does not
change much, mostly 180 degrees at the surface to 210 degree at
3000 ft agl.
&&
.MARINE...
Issued at 245 PM EST Wed Jan 10 2018
Strong southerly flow will continue to allow large waves to build
north of Holland, with heights generally between 5 and 8 feet
tonight through Friday morning. Winds will increase and turn
northerly on Friday, remaining strong through the day and keeping
waves large. The Small Craft Advisory was extended through Friday
afternoon. Additional Small Craft Advisories will likely be
needed from Holland to South Haven Thursday evening through at
least Friday night as the winds increase and turn north.
&&
.HYDROLOGY...
Issued at 1054 AM EST Wed Jan 10 2018
Snowmelt is expected through Thursday, as warm moist air invades the
region. We could see great reductions in the snow pack. Not all of
the melt water will make it into the river system before the cold
air moves back in and locks it down.
Snow water equivalent of the snowpack ranges from around 0.5 inch
near Lansing to around 2 inches in the lake effect belts west of
Highway 131. Fortunately, at this time, no excessive rainfall is
expected with the warmup and amounts should be generally under one
half inch through the warm period. This implies mainly just some
minor nuisance flooding will occur with the snowmelt, however the
rivers will need to be closely monitored for ice breakup and
potential ice jam flooding.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Dense Fog Advisory until 10 AM EST Thursday for MIZ037>039-
043>045-050-051-056-057-064-071.
LM...Dense Fog Advisory until 10 AM EST Thursday for LMZ844>849.
Small Craft Advisory until 5 PM EST Friday for LMZ846>849.
&&
$$
UPDATE...WDM
SYNOPSIS...Duke
SHORT TERM...HLO
LONG TERM...Ostuno
AVIATION...WDM
HYDROLOGY...63
MARINE...HLO
Area Forecast Discussion
National Weather Service Memphis TN
932 PM CST Wed Jan 10 2018
.UPDATE...
Update to remove dense fog and adjust p-types for Thursday night
into Friday.
&&
.DISCUSSION...
A complex winter weather system expected to impact the Mid South
Thursday night into Friday.
First off, expect very mild and moist conditions ahead of an
arctic cold front that will move through Thursday night. Light
rain, drizzle, and fog will continue through Thursday across much
of the region with well above average temperatures.
Quickly changing weather is expected Thursday night and Friday.
Temperatures will quickly fall behind a cold front Thursday night.
This will result in rain changing over to freezing rain and sleet,
then eventually snow through Friday. Latest guidance suggests that
a more prolonged period of freezing rain will occur over the
Winter Storm Watch area with lighter snow and sleet accumulations.
At this time, it appears that over the Winter Storm Watch area
there will be the potential for up to one quarter of an inch of
ice along with 1 to 3 inches of snow and sleet. The greater snow
and sleet accumulations should remain across northwest Tennessee.
In addition to the winter weather potential, it appears that
several hours of strong northwest winds will occur behind the
frontal passage with latest guidance suggesting up to a 10 mb
pressure change across a 100-150 mile distance across the front.
This is likely due to the extreme temperature differences expected
on either side of the frontal boundary. This should result in a
period of very strong winds with a few hours behind the frontal
passage with sustained winds possibly up to 30 mph, with gusts up
to 50 mph possible. These type of winds could result in some
downed trees and power outages.
This system will be quite dynamic and additional forecast
adjustments will be possible. Please continue to monitor the
latest forecast for up to date details.
JLH
&&
.PREV DISCUSSION... /issued 334 PM CST Wed Jan 10 2018/
Winter is expected to return during the end of the work week, a
Winter Storm Watch has been issued for all of West TN, the
Missouri Bootheel, as well as portions of North Mississippi and
East Arkansas.
A dense fog advisory remains in effect across East Arkansas. The
HRRR has done a good job with this hazard...and gradually shifts
it into Central Arkansas later this evening. We may be able to
expire the advisory a bit earlier than 6 PM when is set to
expire.
The latest guidance from WPC focuses more on ice accumulation
from freezing rain and less on significant amounts of snow.
However there is still a large amount of uncertainty with regard
to both the timing...and amount of accumulation. The area of most
concern is generally along the Interstate 40 Corridor Northeast of
Memphis. SREF plumes from the Jackson, TN area range from zero to
a high of 7 inches...with the mean right around one inch. A bit
farther North, values are a bit higher...but the mean remains
under two inches. However, the main threat from this system may
end up being accumulating freezing rain and sleet resulting in
dangerous roadways. We do not anticipate major ice
accumulations capable of widespread damage at this time but once
again, roadways could become treacherous.
Precipitation is expected to begin as widespread rain late tonight
continuing through the day tomorrow. Rainfall totals may approach
one inch before a strong cold front approaches the Mississippi
River late tomorrow. High temperatures tomorrow will likely climb
into middle 60s...but temperatures will tumble Tomorrow night
with morning lows near to below freezing everywhere across the
Midsouth with the exception of portions of Northeast Mississippi.
Rain will transition over to freezing rain after midnight, then
likely a sleet snow mix around sunrise Friday...and transition to
all snow midday Friday. Temperatures will likely remain below
freezing Friday across most of the Midsouth. Any freezing or
frozen precipitation will likely remain with us well into he
weekend.
A reinforcing cold front is expected to sweep across the area
Saturday night. Sunday morning lows will likely be in the teens
area wide.
There is the potential for another round of Wintry weather early
next week, but guidance remains very uncertain. If it materializes
it appears it would be a "mostly snow" event as opposed to a
Wintry mix.
30
&&
.AVIATION...
00z TAFs
Next 24 hours consist of gusty southerly flow and mainly vicinity
showers, with the main frontal passage just getting in range of
the KMEM 30 hour TAF. Expecting mainly MVFR to IFR ceilings, with
not as much visibility issues in this set. KTUP being the main
exception with LIFR ceilings and some fog possible through the
morning hours. Showers will not prevail until after the frontal
passage, which looks to be around at around 04z tomorrow.
WLC
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...Winter Storm Watch from late Thursday night through Friday
evening for Clay-Craighead-Crittenden-Cross-Greene-
Mississippi-Poinsett-St. Francis.
MO...Winter Storm Watch from late Thursday night through Friday
evening for Dunklin-Pemiscot.
MS...Winter Storm Watch from late Thursday night through Friday
evening for Alcorn-Benton MS-DeSoto-Marshall-Tippah-
Tishomingo.
TN...Winter Storm Watch from late Thursday night through Friday
evening for Benton TN-Carroll-Chester-Crockett-Decatur-Dyer-
Fayette-Gibson-Hardeman-Hardin-Haywood-Henderson-Henry-Lake-
Lauderdale-Madison-McNairy-Obion-Shelby-Tipton-Weakley.
&&
$$
Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
812 PM EST Wed Jan 10 2018
.UPDATE (Overnight through Thursday morning)...
01Z water vapor and H4 RAP analysis shows shows a cutoff
mid/upper level low continuing to spin over south Florida
and the Florida Straits. The majority of the synoptic lift
and resulting surface reflection forcing precipitation is
off to the east of our area this evening. A few instability
showers under the upper low cool pool migrated toward Fort
Myers a few hours ago...but have since diminished with the
loss of diurnal heating. Regional radars shows this energy
forcing a large area of rain off the FL east coast...but the
bulk of this activity (if not all of it) stays confined to
the FL east coast overnight into Thursday morning.
The main forecast concern for our area overnight and
Thursday morning will be the development of locally dense
fog. The fog and widespread lower clouds ceilings will
mostly be a concern to the aviation community, but may
become dense enough in spots to impact the early morning
commute as well. Overall...these conditions will make for a
dreary/cloudy start to the morning for a lot of the
region. In addition...will watch the potential for some of
this fog to drift over the coastal waters...including Tampa
Bay and Charlotte Harbor late tonight. This occurred early
Wednesday as well...and had a significant impact on the
shipping route in and out of Tampa Bay. Will be watching the
fog development and evolution closely over the next 3-6
hours in case any dense fog advisories, or marine dense fog
advisories become necessary.
&&
.AVIATION...
Winds becoming light and variable with possible -SHRA near
FMY and RSW ending by 02Z. Confidence is high for a
widespread fog event with MVFR vsby/cigs by 05Z across all
TAF sites. IFR conditions are likely to set in by 08Z with
possible LIFR impacting some locations overnight,
especially across our southern terminals. Conditions should
improve by 15Z although low cigs may still linger for a
couple of hours as daytime heating works to lift and burn
off the stratus.
Prev Discussion... /issued 252 PM EST Wed Jan 10 2018/
SHORT TERM (Today and Thursday)...
A potent upper trough continues to dig in across the
Southern Rockies, generating widespread wintry weather to
the Rocky Mountains. Downstream from this feature, broad
ridging exists from the Southern Plains into the Mid
Atlantic region. Within this upper ridge, a weak cutoff low
continues to spin over southern Florida. At the surface,
weak high pressure remains anchored across the Mid Atlantic
and Northeast, maintaining light easterly flow across the
region.
Though it took some time to mix out of the low clouds and
fog this morning, we are well on our way to a warm afternoon
with middle and upper 70s report across much of southwest
Florida. Just like last night however, low clouds and fog
will begin to build back in overnight tonight. This is due
to a rather deep layer of dry air atop a shallow moist layer
near the ground. This will set up a subsidence inversion,
favoring fog formation as well as low stratus with the
moisture coming off the Atlantic Ocean. The fog may be
locally dense, but widespread dense fog is not expected at
this time. Mild overnight lows generally in the 60s can be
expected as dewpoints remain relatively high with several
days of east to southeast flow off the Atlantic.
We will start the day off gray and dreary on Thursday, much
like we did today. Expansive fog and low clouds will likely
linger into late morning and perhaps midday in some areas.
With enough surface heating, we should eventually erode that
stable surface layer and get the fog and low clouds out of
here, after which another warm one is expected. Some areas
will likely climb into the lower 80s with middle and upper
70s common elsewhere.
Long Term (Thursday night-Wednesday)...
A weak trough at the surface and aloft will be in place
across the state to start the period with an approaching
cold front back to the NW over the Lower MS Valley region.
The front gradually moves through the area later Friday into
early Saturday with scattered showers and a few
thunderstorms possible along and ahead of it Thursday night
through early Saturday. Cooler and drier high pressure then
builds into the area behind the front for the rest of
Saturday through Monday night, with a dry reinforcing front
moving through the area later Tuesday. Lows Thursday night
will be in the upper 50s to upper 60s, then cooling to the
mid 40s north to around 60 south Friday night. The colder
air then moves in for Saturday night and Sunday night with
lows near freezing north to the mid 40s south. Monday night
and Tuesday night will then see some moderating, with lows
in the upper 30s north to around 50 south. Highs follow a
similar trend, starting in the lower 70s north to lower 80s
south on Friday, then mid 50s north to upper 50s south
Saturday, lower 50s north to mid 60s south Sunday, and
moderating Monday to the upper 50s north to around 70 south.
Highs Tuesday and Wednesday in the lower 60s north to the
lower 70s south.
MARINE...
Weak high pressure north of the waters will maintain light
east to southeast flow over the next few days. Patchy sea
fog will be possible both tonight and tomorrow night as fog
moves off land and over water. As winds become southerly
ahead of a cold front Friday, a prolonged sea fog event may
unfold. Winds will increase sharply behind the front as it
passes late Friday into Saturday, bringing drier air and
removing fog potential. Cautionary to advisory winds and
seas will be likely for a few hours Friday night into early
saturday. As strong high pressure builds in north of the
waters, periods of cautionary to advisory level conditions
may occur at times through the weekend and into early next
week.
FIRE WEATHER...
Weak high pressure will remain north of the area with light
easterly flow persisting. Warm and somewhat humid
conditions will persist through Friday. A cold front will
move through the area Friday night into saturday, bringing
breezy winds and cooler drier conditions for the weekend.
Humidities look to remain well above critical thresholds
through the weekend and no fire weather concerns are
expected.
&&
.Preliminary Point Temps/PoPs...
TPA 61 76 65 77 / 0 20 20 50
FMY 62 79 67 81 / 30 20 20 30
GIF 62 79 65 80 / 10 20 20 50
SRQ 61 74 64 77 / 0 10 20 40
BKV 60 78 60 77 / 10 20 20 50
SPG 61 75 64 75 / 10 20 20 50
&&
.TBW WATCHES/WARNINGS/ADVISORIES...
FL...None.
Gulf waters...None.
&&
$$
UPDATE...Mroczka
Aviation...Norman
Previous Discussion...Austin/Hubbard