Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/20/19
/Previous forecast discussion issued 442 AM CST Tue Feb 19 2019/
Wednesday through Tuesday.
Southwest flow aloft continues on Wednesday between a positively
tilted longwave trough over the western CONUS and a strong
subtropical ridge centered east of the Bahamas. Within the western
CONUS trough, a negatively tilted shortwave over the Central
Plains will continue to lift northward into the Northern Plains
and Upper Midwest, while an additional vort max digs down the
back side of the trough along the West Coast, reinforcing the
longwave trough. A weak surface low will be over Mississippi, with
another low beginning to deepen near Kansas City. A 1037 mb high
will be centered near New York City, with a classical CAD wedge
extending down the lee of the Appalachians into Central Alabama. A
cold front will be over Mississippi with a warm front/wedge front
extending southeastward into far southwest Alabama and the Florida
panhandle. Showers and thunderstorms will be ongoing across
Mississippi into far northwest Alabama in the warm conveyor belt
ahead of front, aided by a 45-50kt LLJ. While some linear segments
may be present, CAMs do not suggest a well-organized QLCS.
Meanwhile further east across the rest of Central ALabama, a few
lighter isentropic lift showers may be occurring.
This activity will slowly inch eastward through the day, as flow
will be largely parallel to it and it may lack cold pool
organization. It will be maintained by the low level jet, some
upper-level divergence from the right entrance region of a jet
streak, the cold front, and perhaps some weak height falls at
least initially. While area-average modeled QPF amounts aren`t as
impressive as previously thought, this will still have the
potential to produce pockets of locally heavy rainfall given the
uni-directional flow promoting training, slow movement of the
overall line, instability resulting in convection, and especially
the high PWATs. The February monthly all-time PWAT record of 1.7
inches at BMX will definitely be in jeopardy. The flow parallel
to the front will help limit significant lifting over the
boundary, however. The main threat will be areal flooding of low-
lying areas and streams, and eventual flooding on area rivers.
This is why an areal flood watch is in effect rather than a flash
flood watch. But some pockets of flash flooding will be possible
as well, especially in urban areas, and quick rises on area creeks
will occur. So use caution when traveling and do not drive on
flooded road ways. Did expand the flood watch by a row of
counties southward, based on expected QPF and to include the urban
areas of Anniston/Oxford and Shelby County. By Thursday evening
the front and associated moisture/precipitation axis along it will
stall and become oriented from the southwest to the northeast.
The precipitation area will probably contract some, centered along
the front. Forcing will be weaker resulting in lighter rainfall
rates, but these will only serve to continue to saturate soils and
aggravate any ongoing flooding.
The tricky part of the forecast Wednesday will be the erosion of
the CAD wedge and retreat of the warm front/wedge front, which
will impact temperatures, dew points, and resultant surface-based
CAPE potential. Tonight`s CAMs followed suit with the NAM in
indicating the warm front getting hung up along our southern
border during the day on Wednesday. Thinking remains the same that
the higher resolution models have a better handle on the CAD,
though the long range HRRR and regional Canadian do show higher
dew points. There may be a non-zero threat of a brief tornado if
the warm front can lift up into our far southwest counties, but
confidence in this occurring is too low to mention in the HWO at
this time. Will note that the NAM suggests elevated MUCAPE of 1000
J/kg across the western half of the state and mid-level lapse
rates of 6-6.5 C/km and plenty of bulk shear, so some elevated
hailers may be possible, and isolated severe hail cannot be ruled
out if an elevated supercell forms. Did beef up the thunder
mention in the grids in the west for this reason.
Height rises aloft occur on Thursday as ridging builds over the
eastern CONUS ahead of a closed low over the southwestern CONUS.
This will be indicative of subsidence aloft. However, still expect
a band of lighter rain to be ongoing along the front due to lift
at low levels. While the surface front will remain stalled near
I-85, southerly flow in the 925-850mb layer will begin to push the
elevated portion of the front in that layer northward and the
moisture axis also moves northward. Isentropic lift associated
with the process will cause the band of light rain to move
northward. Overall rainfall amounts in the watch area will be
light, but could aggravate ongoing flooding. Could also see some
shower and thunderstorm development south of the front in our far
southeast counties with daytime heating of a moist air mass and
additional moisture moving off the Gulf. With SBCAPE values of
1000-1500 J/kg and 0-6 km bulk shear around 45 kts, some of these
storms could be strong, and an isolated severe storm with
wind/hail cannot be ruled out. However, low-level shear will be
confined to the cool side of the front, and the lack of an upper-
level trigger should prevent anything from being too organized.
Similar trends continue on Friday. Low pressure begins to develop
over the southern High Plains, with a 30-35 kt LLJ developing over
Mississippi into northwest Alabama. The warm front aloft should
continue to push north of the area, while models disagree how
quickly the surface warm front will push north with a weak wedge
also potentially developing. The main heavy rain threat should
set up north of the area from Arkansas to Tennessee, but rain
chances remain high given the moist air mass. A similar threat for
strong storms/possible isolated severe to Thursday exists, but
encompassing more of the area.
Models are in good agreement on a strong negatively tilted trough
lifting from the Southern Plains to the Great Lakes Saturday and
Saturday night, accompanied by a deepening surface low and cold
front. Strong heating of an expansive warm sector will occur on
Saturday afternoon. If forcing is strong enough this far south,
then there is the potential for supercells developing in
Mississippi to track into at least our northwest counties due to
60-65kt southwesterlies at 500mb and a 50 kt LLJ, potentially
followed by a QLCS. Will introduce a threat for tornadoes to the
HWO. If the timing remains during the later afternoon and early
evening versus overnight, and forcing is sufficient, an increase
in the confidence factor is a definite possibility.
Dry conditions finally arrive behind the front by midday Sunday.
However, this looks to be short-lived, as models are already in
agreement on another shortwave trough bringing more wet weather
for Monday night and Tuesday.
32/Davis
&&
.AVIATION...
00Z TAF Discussion.
We remain in a very wet pattern and should remain socked in with
low cigs through the forecast period. The current upper shortwave
will continue to move to the north/northeast this evening. We
should get a lull in the convection of at least the more
widespread activity until during the day on Wednesday. Winds will
stay up through the period as gradients remain tight. Showers and
thunderstorms will become more widespread again by Wednesday
afternoon as a warm front moves northward and ahead of a cold
front approaching from MS.
08
&&
.FIRE WEATHER...
A prolonged period of rainfall will continue through the end of the
week, with a strong storm system expected over the weekend. Very wet
conditions are expected, especially across the northern half of the
area. There are no fire weather concerns at this time.
&&
.PRELIMINARY POINT TEMPS/POPS...
Gadsden 43 60 51 59 52 / 90 100 100 80 70
Anniston 44 62 55 63 55 / 90 80 100 80 60
Birmingham 47 65 54 61 55 / 90 100 100 80 70
Tuscaloosa 49 66 53 60 55 / 90 100 90 80 60
Calera 47 66 55 63 56 / 90 90 100 80 60
Auburn 45 65 61 73 60 / 70 60 80 70 60
Montgomery 52 71 63 74 63 / 70 70 80 70 50
Troy 53 71 66 77 64 / 50 40 60 60 40
&&
.BMX WATCHES/WARNINGS/ADVISORIES/...
Flood Watch through late Thursday night for the following
counties: Bibb...Blount...Calhoun...Cherokee...Clay...Cleburne...
Etowah...Fayette...Jefferson...Lamar...Marion...Pickens...
Shelby...St. Clair...Talladega...Tuscaloosa...Walker...Winston.
&&
$$
Area Forecast Discussion
National Weather Service Denver/Boulder CO
858 PM MST Tue Feb 19 2019
.UPDATE...
Issued at 858 PM MST Tue Feb 19 2019
The areas of light snow which persisted through the afternoon and
early evening are on the decrease and moving eastward as the
main upper trough moves out over the Central Plains. Radar data
shows a few bands of heavier snow moving over central and eastern
Elbert County, with light snow extending across Lincoln and
Washington Counties. Cold temperatures and lower dew points are
moving in from the north and northwest. Areas of stratus are
evident over northern Weld County, but the latest HRRR shows that
this cloud cover should remain north of the Denver Metro area
overnight. Th emain changes to the evening forecast were removing
the snowfall from the plains areas except for the Palmer Divide
and up into Washington County. Palmer Divide locations may see
another inch or so of accumulation overnight, and Washington and
Lincoln Counties should see less than a half inch.
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 315 PM MST Tue Feb 19 2019
Current satellite IR picture shows moisture pulling up from the
south and NE across the region. Another batch of moisture and CAA
will move SE from Utah and into the central mountains by the evening
hours. There will be a slight break over the mountains between the
two disturbances but conditions are expected to remain mostly cloudy
and cold. The next batch of energy is projected to impact the
mountains around midnight with light to moderate snow. NAM model
cross sections are showing 8-9 C/km lapse rates, which at first
glance seems a tad high, but could indicate some instability in the
mid levels that will increase snow intensity for a short period of
time overnight. For the plains, a denver cyclone continues to spin,
pulling in moisture from the SE and wrapping it around to the south
keeping light snow across the region. Cyclone center remains just NE
of the airport and is expected to break apart as increasing westerly
flow moves in from the approaching system and a lee side low sets up
over the northern foothills. This will aid in increasing westerly
winds and dry out the low and mid levels over Denver, ending the
snow. Accumulations into Wednesday evening will be 1 to 4 inches for
the mountains with a trace to an inch across the plains, with the
higher amounts east of a Sterling to limon line. Some gusting is
possible over the higher northern foothills with increased
subsidence during this time and some blowing snow may be possible
early Wednesday morning with the low density snow. With the
increased westerly winds by early Wednesday, conditions will
partially clear out over the plains, minus the far eastern plains
where some low level clouds may linger. Temperatures will drop into
the low single digits overnight.
For Wednesday, the upper trough will have moved out with increasing
zonal flow aloft. There is enough moisture upstream ahead of the
next upper level disturbance over Oregon to keep a slight chance of
snow in the mountains through Wednesday, but amounts will be light
and impact mainly the central and northern mountains. Highs on
Wednesday will be slightly warmer in the 30s across the plains.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 315 PM MST Tue Feb 19 2019
A brief period of ridging will develop over Colorado Wednesday
night which will allow for mainly dry conditions across the CWA.
Strengthening southwesterly mid to upper level flow will increase
the chance for snow showers in the mountains during the second
half of Thursday. Temperatures Wednesday night into Thursday will
be around 10 degrees below normal across the majority of the CWA.
By Thursday evening, the focus will shift to the trough digging
into the Desert Southwest. Models are now showing a weak shortwave
breaking off from the stronger trough and moving northeastward
through Colorado early Friday morning. This will create a chance
of snow showers in the mountains and foothills and northeastward
across to the Cheyenne Ridge. In addition, a lee cyclone
developing over east-central Colorado will likely develop low
clouds over most of the South Platte River Valley. With shallow,
low-level moisture in place, fog and perhaps freezing drizzle
could develop but there remains considerable uncertainty with
those developing so they were not included in the gridded
forecast.
The main portion of the trough will then eject onto the central
plains Friday night and into Saturday with a surface cyclone
developing over northeastern New Mexico. Models still produce
moderate to heavy snowfall over the northwest side of this cyclone
but overall guidance has shifted farther southeastward with this
system. Therefore, it looks less likely that the eastern plains
will receive moderate to heavy snowfall with this system unless
there is a major shift back northwestward. Instead, there is a
good chance of light snow over the eastern plains Friday night and
Saturday with little impacts.
Another system may affect Colorado Sunday night into Monday but
there is little agreement in the models on this system and low
confidence in the forecast.
&&
.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 858 PM MST Tue Feb 19 2019
Lingering snow flurries over the Denver area airports should be
clearing out in the next hour or so. Drier air will be moving into
the Denver area from the north and northwest through the night.
Winds should remain light. Some low cloud decks may hang around
through the early morning hours, but no ceilings below 2500 feet
AGL are expected. No impacts from ceiling or visibility are
expected tomorrow, but some gusty northwest winds may develop
during the late morning and afternoon hours.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Dankers
SHORT TERM...Bowen
LONG TERM...Danielson
AVIATION...Dankers
Area Forecast Discussion
National Weather Service Des Moines IA
552 PM CST Tue Feb 19 2019
.SHORT TERM.../Tonight through Thursday/
Issued at 409 PM CST Tue Feb 19 2019
Confidence: High on snow chances and amounts tonight into Wednesday.
Little overall changes to the system expected to impact the area
tonight into Wednesday. Main changes was to shift the heavier snow
axis a bit north, and increase amounts in that area slightly.
Otherwise did delay onset of the heavier snow this evening, so made
an adjustment to the start time of the Winter Storm Warning. Looks
like main area of precipitation will begin to spread across southern
and central Iowa toward mid/late evening. More dry air in place
across the state today than models had originally had thus, looks
like it will take a bit longer for snow to move into the state.
Already seeing some mid level echoes across the far south, and may
still see a flurry or some very light snow at times across the
south/west early this evening. Otherwise push of moisture advection
across Iowa by this evening into tonight. As the column saturates
snow will spread and pick up in intensity overnight. Cross-sections
indicate decent lift through the DGZ especially across
central/northern Iowa late tonight and also some instability present
aloft across most of the area. Strongest in the south from 06-12z.
Therefore expecting fairly intense snowfall rates at times with a
decent band moving through. Have trended initial pops toward the
HRRR given the drier air to overcome. Much of the area to be covered
in snow by late tonight with rates of 1-2 inches per hour at times.
This will allow snow to build up quickly on roads and significantly
reduce visibilities to less than 1/2 miles at times. Travel
conditions will deteriorate rapidly after 03-06z through 12z. The
bulk of the snow across metro area and southern Iowa to fall through
10-12z tonight, with some heavier snow into northern Iowa initially
still Wednesday morning. The morning commute will be impacted at all
sites.
As the surface low tracks across Iowa from south to north through
Wednesday morning, should start to see the snow lighten up and taper
off from south to north through the day. Also have some drier air
aloft move into the south/southeast which could allow for a
transition to some light freezing drizzle/rain Wednesday morning
resulting in a light glazing of ice potentially. The latest model
sounding suggest the west/southwest could see some light snow linger
a bit longer than previously anticipated with the deformation zone
moving through Wednesday. Therefore did extend the Winter Storm
Warning for Cass, Adair and Audubon Counties through the morning
hours. Also similar for the extension of the western Hwy 20 counties
from 18-21z Wednesday afternoon.
As for amounts, kept fairly similar amounts as previous forecast.
Latest track and potential for banded snow/higher snowfall rates
shifts this axis slightly further north pushing the highest snowfall
still in our forecast area west of I-35 and north of I-80. These
trends can be further refined as the snow moves in, but a location
within the heavier band may likely see close to 10" of snow or
possible slightly higher. Otherwise widespread 8-10" in the
west central to northwest looks most likely.
Once the snow moves out Wednesday, dry conditions expected for
Wednesday night into Thursday as high pressure builds in to the
state. Temperatures will remain chill with highs into the 20s to
around 30 Thursday.
.LONG TERM.../Wednesday night through Tuesday/
Issued at 409 PM CST Tue Feb 19 2019
The active weather pattern continues into early next week. While
timing and placement issues still exist, the current trends indicate
that a winter storm will impact the state later Friday and persist
through Sunday morning. On Friday an upper trough will deepen over
the Plains eventually closing off into an upper low. As it deepens,
it will tap warmer air and eventually a lot of deeper moisture
sending this up over Iowa. As the precip potential increases across
the far west late Friday, we will see a rain or freezing rain
potential across the south with snow north. As the precip spreads
across the state Friday night, ice introduction and temps are all
sporadic and very messy giving us a wintry mix including the
potential for rain far south, freezing rain or snow far north and
freezing rain and sleet in between. Ice accruals during this period
look to be around a tenth of an inch northwest and west with a
secondary area southeast. Somewhat lighter amounts are expected
across central sections.
Late Saturday and Saturday night as the low lifts out of Kansas and
into Southern Iowa a second shot of deeper moisture and much colder
air sweeps in on the backside and precip changes over to snow
northwest into central Iowa. Wind picks up during this period as
well and this will be a period of moderate to heavy snowfall with
wind across the northwest. Across central sections, light to
moderate snowfall is expected and across the southeast, precip will
change from rain to snow late with around an inch of so. The
interesting thing with this area is that there is enough instability
during the afternoon and evening that thunderstorms may be possible.
Uncertainty with this is too high to include in the forecast for now
but it is something that we will be evaluating as time goes on.
Late Saturday night and Sunday morning, the system wraps up and
lifts into the Great Lakes with deformation zone precip continuing
north and northeast and the rest of the state seeing much colder and
windy conditions.
High pressure builds in for Sunday into Monday then by late Monday
into Tuesday, another weak system pushes in from the west. A
surface low over the Southern Plains with a frontal boundary
extending into Missouri and possibly southeast Iowa will increase the
forcing and moisture across southern/western Iowa which will spread
precip across the state Monday night into Tuesday. with a couple of
stronger systems to contend with first, and the high uncertainty
with anything regarding the Monday/Tuesday system, we will not be
highlighting this at this time.
&&
.AVIATION.../For the 00Z TAFS through 00Z Wednesday evening/
Issued at 552 PM CST Tue Feb 19 2019
Poor aviation weather will occur for much of the forecast period
as widespread snowfall moves through the state. Severe
restrictions to visibilities and ceilings are expected with
widespread IFR to LIFR conditions late tonight into Wednesday
morning. Some improvement is expected by Wednesday afternoon,
mainly to visibilities as the snow ends. Winds will increase from
the east tonight and become south to southwest by Wednesday
afternoon.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning from 9 PM this evening to noon CST
Wednesday for IAZ044>048-057>062-070>075-084>086.
Winter Storm Warning from midnight tonight to 6 PM CST Wednesday
for IAZ004>007-015>017-023>028-037>039-050.
Winter Storm Warning from 9 PM this evening to 9 AM CST
Wednesday for IAZ081>083-092>097.
Winter Storm Warning from midnight tonight to noon CST Wednesday
for IAZ049.
Winter Storm Warning from 9 PM this evening to 3 PM CST
Wednesday for IAZ033-034.
Winter Storm Warning from midnight tonight to 3 PM CST Wednesday
for IAZ035-036.
&&
$$
SHORT TERM...Beerends
LONG TERM...FAB
AVIATION...Cogil
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1010 PM EST Tue Feb 19 2019
.UPDATE...
Emphasis in the evening update is placed on the character of snow
expected at the start of the event across the Winter Weather Advisory
area. Rapid onset of snow remains projected in the 5-7 AM time
window followed by a burst of heavier snow shortly after and lasting
through mid morning. This has potential for stronger negative impact
on the morning commute before the transition to wintry mix and then
freezing rain/drizzle mid to late morning, which remain on track in
terms of timing. As for the snow, there remains concern for the
limiting factor of lower end snow-liquid ratio, as detailed in the
afternoon discussion, but with trends toward higher QPF brushing the
south 4 counties during the 12-15Z time period. These trends are
supported by upstream observations across MO, KS, NB, and IA that
report pockets of 1/4-1/2sm visibility in snow occuring with the
leading zone of strong isentropic ascent that is expected to follow
the entrance region of the upper jet into Lower Michigan toward
sunrise. The rapid progression of forcing through the region does
suggest just adding an inch to total accumulation for now along with
greater emphasis on snow intensity in the WSW update.
&&
.PREV DISCUSSION...
Issued at 708 PM EST Tue Feb 19 2019
AVIATION...
Surface high pressure exits the central Great Lakes while
maintaining VFR across the area for almost the entire night. During
this time, low pressure continues to organize over the Plains and
reaches northern Missouri during Wednesday morning. A pattern of snow
develops ahead of the system and across the Ohio valley before
moving into Lower Michigan and first reaching the DTW area around
sunrise. The snow quickly spreads northward during the morning
resulting in at least MVFR restriction in ceiling and visibility. A
burst of heavier snow capable of IFR is also expected during mid
morning but likely only reaches PTK before shearing eastward. This is
followed by a transition to mixed sleet, freezing rain, and freezing
drizzle through the afternoon which further strengthens IFR
conditions across the region. As low pressure moves into Wisconsin,
the associated warm/occluded front moves into Lower Michigan and
keeps conditions IFR/LIFR through mid Wednesday evening. Temperature
warms above freezing as far north as FNT while barely reaching the
freezing mark at MBS during late afternoon which likely maintains a
mix of rain or freezing rain before precipitation decreases coverage
and intensity around mid Wednesday evening.
For DTW... VFR above 5000 ft holds through much of the night while
the wind gradually becomes light easterly. Conditions rapidly
transition down to MVFR with the onset of snow toward sunrise and
then IFR with a burst of heavier snow around mid morning. About 1
inch of normal to wet snow accumulation is expected before a
transition to freezing rain/freezing drizzle occurs by late morning.
Temperature then rises above freezing mid to late afternoon
resulting in just scattered rain showers before ending Wednesday
evening. LIFR ceiling and fog is expected to persist from late
afternoon through mid Wednesday evening when a cold front brings a
gusty wind shift to southwest.
DTW THRESHOLD PROBABILITIES...
* High for ceiling 5000 ft or less after 11Z Wed.
* High for precip type as snow 12z-16z Wed
* High for precip as mix of freezing rain and sleet 16z-20z.
PREV DISCUSSION...
Issued at 316 PM EST Tue Feb 19 2019
DISCUSSION...
Very strong dynamic response taking shape over the southern tier of
the United States this afternoon. Strong right entrance dynamics are
strengthening a deep tropospheric warm front that is supporting
increasingly widespread heavy rain currently extending from the
Arklatex eastward to the Appalachians. Moisture transport into and
ascent within the frontal zone will tend to increase tonight as
height falls associated with the deep PV anomaly over the Desert
Southwest emerge over the Front Range and amplify the low-level
response. Snowfall will expand over Iowa, Minnesota, and the eastern
Great Plains as the deformation zone matures overnight. The warm
conveyor has been forecast to mainly deflect south and east of the
area, although the 12z EC did make a slight westward adjustment with
slightly higher QPF suggested in the southern segment of the
advisory first thing Wednesday morning.
Most of the forecast reasoning remains unchanged from last night and
this morning`s update. What would typically be a solid WAA type
snowfall along this impressive incoming warm front will be
compromised early by the surging dry slot which will set the stage
for transition to light freezing rain and freezing drizzle as the
warm nose surges north. Forecast cross-sections indicate that
Wednesday afternoon will be characterized by a strongly stable
boundary layer supportive of freezing drizzle courtesy of both large
scale ascent and respectable shearwise forcing. In addition, a
considerable coverage of conditional instability is noted over the
entirety of CWA between the top of the boundary layer and about 600
or 650mb. Spontaneous PV generation by the NAM12 within this layer
is a nod toward the convective potential. The general expectation is
still for 0.1" or less of ice accretion, however fzra showers are
appearing increasingly likely during the afternoon and will support
locally higher amounts. Coverage of showers and/or intensity of
drizzle will be key concerns going forward. Northern counties were
omitted from the advisory due to increased probability of sleet
reducing the magnitude of the travel hazard there.
There is one item of concern heading into tonight. Widespread
convection across the south has been, and will continue to, generate
copious amounts of latent heat. Coincidentally, the rapid refresh
guidance and the 18z NAM has been trending westward with the higher
QPF prior to the arrival of the dry slot. Quick analysis of the 18z
NAM output suggests that it is not due to a westward migration of
the warm conveyor. Instead, it appears that the warm front may
simply be modeled to retain its integrity for slightly longer as it
lifts north. The physical reason for this trend is presumably
convection-driven backbuilding of the upper jet and attendant right
entrance dynamics. The latest RAP guidance exhibits an identical
trend, though slightly more aggressive. The afternoon update will
feature a slight upward nudge in QPF across the board with another
adjustment to QPF 09-15z in the southern portion of the advised area
most of which will go into antecedent snowfall. However, the warm
column will support plenty of riming and a coincident lowering of
snow ratios below 10:1. Lowering of the dry slot will relegate any
remnant precip after 03z Wed evening to drizzle or flurries. Breezy
with gusts around 25 mph on Thursday as the gradient ramps up with
high pressure building to the south, but modest cold advection will
limit forcing for any higher end gusts and keep highs elevated in
the 30s.
Height rises associated with a high pressure and confluent flow
aloft with be passing through the region on Friday and result in
quiet and dry weather conditions to end the work week. Cold start
to the morning with temperatures starting out in the teens to low
20s with the expectation of mostly clear skies allowing for good
radiational cooling overnight. Diurnal temperature increase will
bring highs into the mid to upper 30s.
Main focus for the weekend will be a very strong upper wave tracking
out of the Four Corners Region and undergoing strong cyclogenesis as
it tracks into the Midwest. This system will lift through the Great
Lakes Region with the center of the low pressure tracking
northeastward across the Lower Peninsula Saturday night and into
southern Ontario by Sunday afternoon. Precipitation in the form of
rain will first impact southeast Michigan Saturday afternoon ahead
of this system within a region of WWA and isentropic ascent. High
temperatures will increase into the 40s for much of the area within
this warm sector. Given the track of the low, expect rain to be the
dominant precipitation type with the warm sector being driven east
throughout the day Sunday. By Sunday late afternoon and early
evening, cold air on the back side of the departing low will be
ushered into southeast Michigan and bring falling temperatures and a
transition to snow into Sunday night. Cold northwesterly off the
lakes will keep a chance for lingering snow showers into Monday
before high pressure moves in and brings and end to precipitation.
MARINE...
High pressure will bring quiet weather and light winds the rest of
today and tonight. A low pressure system will move across the
northern Great Lakes Wednesday and Wednesday night. Southeasterly
winds will increase Wednesday to 20-25kts with gusts to around 30kts
across north half of Lake Huron. Winds will veer to the west by
noon Thursday as the low moves off to the east. Winds will continue
sustain 20-25kts gusting to around 30kts Thursday before diminishing
Thursday night through Saturday. Another system Sunday will bring
another round of higher winds.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Winter Weather Advisory from 7 AM to 7 PM EST Wednesday for MIZ075-
076-082-083.
Winter Weather Advisory from 11 AM to 10 PM EST Wednesday for
MIZ060>063-068>070.
Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&
$$
UPDATE.......BT
AVIATION.....BT
DISCUSSION...JVC/AA
MARINE.......DRC
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
922 PM EST Tue Feb 19 2019
.SYNOPSIS...
Canadian high pressure will ridge down over the forecast area
into Wednesday as a series of low pressure systems moves up from the
Gulf. The combination of cold air and abundant moisture will result
in an area of wintry precipitation for the mountains and foothills
through early Wednesday. The moist pattern will continue well into
the weekend until a cold front finally moves through the region and
dries things out.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
As of 900 PM: Precip rates have tapered off across the northern
CWFA as frontogenesis band has shifted northward above the drier
airmass. This trend is expected to continue for the very near
term. The predominant forcing soon will become upglide atop the
strengthening CAD wedge, as 1035-ish mb arctic high pressure settles
into southern New England. Thus likely to categorical PoPs return
to the area over the next few hrs where not already present in the
fcst. The fcst temps produced by day shift so far have performed
very well. That fcst leaned heavily on the cold NAM, which has
done rather well with diabatically enhanced CAD events throughout
the winter. Wet bulb temps from current mesoscale analysis and
short-term guidance however remain a bit warmer than the fcst
does overnight. The assumption of diabatic cooling still seems
wise, so these temps mostly look good. With this update some LAMP
temps/dewpts have been blended in for the first few hrs, in order to
match obs to the fcst. Combined with updated temp profiles from the
RAP, this results in some areas that previously were fcst to get a
few hrs of freezing rain now getting mostly sleet instead. The NW
NC Piedmont still looks to be on the fence as far as getting more
than a trace of ice, but the advisory looks well-placed for now,
in light of the intermittent possibility of wintry wx beyond what
has already happened.
Confidence is high that cold air will be able to lock in near
the Blue Ridge, especially in the barrier jet location along
and near the eastern Blue Ridge escarpment. In addition to the
cooling from the maintenance of the CAD, very strong SE upslope
flow at the top of the developing cold dome will both enhance
the cooling while providing additional forcing to augment precip
rates. In fact, with the frontogenetical forcing shifting north
of the forecast area this evening, upslope flow will become the
primary source of lift tonight into Wednesday. All that being the
case, our confidence in significant ice accretion remains highest
in areas along the eastern Blue Ridge escarpment north of I-40,
where the warning is currently in place. Other areas of concern
will be farther southeast, especially in the upslope areas of
Polk/Rutherford mtns, as well as Henderson and Transylvania
Counties. I suspect that some locations in these zones will see
warning criteria ice, esp along and south/west of the Divide, but
confidence is low in heavy ice accretion being widespread enough
to warrant an upgrade. Meanwhile, the strength of the SE upslope
flow and developing CAD creates a concern that areas along the
Blue Ridge in northwest SC and extreme northeast GA will see light
icing develop toward daybreak Wed, and Pickens/Oconee Mtns in SC,
as well as Rabun County in GA will be added to an advisory.
Otherwise, Wed will see gradually diminishing precip chances,
with most areas likely warming enough to see just rain/drizzle
during the afternoon. Temps will be almost 20 degrees below climo
under the influence of mature cold air damming.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
As of 215 PM EST Tuesday: Upper jetlet divergence will increase over
the mountains Wednesday night, with 500 mb channeled vorticity
crossing the region as well, enhancing upward vertical motion over
the forecast area. Meanwhile, a surface cold front west of the
Appalachians Wednesday night will push east into the mountain chain
before laying over into the region through the day on Thursday. The
uptick in forcing and deeper moisture along and ahead of the frontal
zone will raise the QPF, and the associated hydro threat, starting
Wednesday night. It`s quite possible that a Flood Watch will be
needed soon, especially for the southwest NC mountains and the
northeast Georgia mountains. The narrow zone of deeper moisture
around the frontal boundary may well stay parked over the forecast
area Thursday. Anticipate some 500+ J/kg sbCAPE values over the
lower piemdont southeast of the front, with temperatures throughout
being quite difficult to pin down given uncertainty over the frontal
position.
Anticipate some very modest height rises over the southeast Thursday
night through Friday. The strongest upper jet energy continues to
wrap around to the north and west of the region for most of late
Thursday through Friday. However, low level southwest flow refocuses
once again over the mountains through Friday while upglide fans out
to the east along a baroclinic zone. This will cause the hydro
threat to either persist or return through the period. Although 1032
mb high pressure will set up to the north, low level temperatures do
not look quite cold enough to support mixed ptypes at present, so
will keep the robust PoPs all associated with liquid rain for now.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
As of 230 PM EST Tuesday: A southern stream closed low will move
from the four corners region of the desert southwest to the southern
plains Friday night through Saturday, before lifting over the Great
Lakes on Sunday. This will batter down heights across the southeast
over the weekend. Low-level southwesterly flow will strengthen
Saturday night ahead of an approaching cold front, and it`s good bet
that hydro problems will persist and develop through a good chunk of
the weekend. There is good consensus on a cold fropa from the west
on Sunday morning. This timing will be unfavorable for much
instability along the passing front, keeping any thunder in check.
Upper flow then becomes more zonal late Sunday through Monday. Any
shot of shallow northwest flow moisture into the NC mountains Sunday
night behind the departing cold front will be very short-lived. Mid
to upper flow backs Monday night through Tuesday, with weak
shortwaves moving from the western Gulf coast to the southern
Appalachians. The GFS holds off on upglide moisture returning across
the southeast until Tuesday afternoon, while the ECMWF brings
moisture back a bit faster late Monday night. Will feature a
consensus of increasing PoPs for rain on Tuesday. Max temps some 10
degrees above climo on Sunday will fall back below climo by Tuesday.
&&
.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
At KCLT and elsewhere: The primary forcing for precip at the start
of the TAF period is a band of midlevel frontogenesis extending
across NC and northern upstate SC. This forcing is occurring over
a cold sfc high centered over the Mid-Atlantic coast, and cold-air
damming is beginning to take shape as a result of precip falling
into this dry airmass. Mostly RA is present over the region,
but within some of the heavier pockets, PL or even SN is mixing
in. Precip rates will diminish to some degree as the frontogenesis
band moves further north and also weakens. Cigs are mainly VFR
with the forcing being elevated, but as nocturnal cooling occurs
in the PBL and as isentropic upglide over the wedge takes over as
the primary forcing, IFR cigs will develop overnight. Have kept
cig trends closer to the more pessimistic MAV/MET, since LAMP and
HRRR aren`t reflecting enough of the CAD`s effect. Periods of IFR
vsby may occur during heavier precip.
FZRA still looks likely to develop over KAVL as temps cool below
freezing via diabatic processes in the CAD wedge, and can`t
rule this out at KHKY either--though with lower confidence it is
mentioned only in TEMPO there. This threat will come to an end by
late Wed morning as temps warm again, as precip rates diminish as
warm front effectively moves north. This is expected to worsen vsby,
however, as fog settles in. IFR will persist to end of period.
Outlook: A series of low pressure systems will continue to move
through the region through the end of the week. This will produce
precipitation and associated restrictions for long periods of time
with each system.
Confidence Table...
02-08Z 08-14Z 14-20Z 20-00Z
KCLT High 83% Med 69% High 84% High 80%
KGSP Med 78% Med 76% High 86% Med 78%
KAVL High 83% Med 73% High 81% High 84%
KHKY High 87% High 82% High 82% High 90%
KGMU Med 79% Med 78% High 87% Med 78%
KAND High 87% Med 69% High 86% Med 78%
The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables and ensemble forecasts
are available at the following link:
www.weather.gov/gsp/aviation
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...Winter Weather Advisory until 4 PM EST Wednesday for GAZ010.
NC...Winter Weather Advisory until 4 PM EST Wednesday for
NCZ035>037-048-052-053-056-057-059-063>065-502-504-
506>510.
Winter Storm Warning until 4 PM EST Wednesday for NCZ033-049-
050-501-503-505.
SC...Winter Weather Advisory until 4 PM EST Wednesday for
SCZ001>003.
&&
$$
SYNOPSIS...DEO
NEAR TERM...JDL/Wimberley
SHORT TERM...HG
LONG TERM...HG
AVIATION...Wimberley
Area Forecast Discussion
National Weather Service Lincoln IL
935 PM CST Tue Feb 19 2019
.UPDATE...
Issued at 930 PM CST Tue Feb 19 2019
Will continue the winter weather advisory tonight starting at 9
pm, and going til 6 am in southeast IL and through noon on Wed
over central IL.
Updated the forecast for the light snow chances increasing late
this evening, and also having the chance of light freezing rain
arriving a bit quicker from the sw during overnight. Much of CWA
has been dry so far this evening as mid level cloud deck as been
gradually lowering in the 5-10k ft range. During past 30-60
minutes finally has some very light snow develop in Altona with a
dusting, while flurries at weather office in Lincoln started
around 9 pm. Radar mosaic and surface obs show brunt of
precipitation along and south of a St Louis to Bloomington, IN
line, just south of Clay, Richland and Lawrence counties. Temps
were 32-35F along and south of I-70, so mixed precipitation over
southern IL with rain, snow and light freezing rain being reported
south of CWA. Temps were 30-32F over central IL north of I-70 and
holding nearly steady or dropping about a degree this evening with
an increasing easterly wind 10-16 mph and few gusts around 20
mph.
Latest hi-resolution models show one band of light snow developing over
northern CWA late this evening mainly along and north of a Canton
to Bloomington line. The larger area of mixed pcpn over southern
IL is forecast to spread northward across southern half of CWA by
midnight and overspread northern CWA early overnight. Much of
central IL will start as light snow, with mixed pcpn in southeast
IL, including snow, rain and freezing rain. The mixed pcpn
including chance of freezing rain to spread northward across
central IL during overnight, reaching northern CWA late tonight.
Temps in southeast IL forecast to drop to near or just below
freezing for a few hours, then rise back above freezing late
tonight. Northern CWA has lows in upper 20s overnight, then rising
above freezing by late Wed morning. Snow accumulations of 1-2
inches over much of CWA overnight, will ice accumulations around a
tenth inch northern/nw CWA and just a light glaze in southeast IL
until late tonight when temps rise back into the mid 30s with ESE
winds.
&&
.SHORT TERM...(This evening through Wednesday)
ISSUED AT 325 PM CST Tue Feb 19 2019
A fast-moving winter storm system will affect central and
southeast Illinois tonight and Wednesday. A deep upper level
trough centered on the Rockies this afternoon will become
negatively tilted tonight as surface cyclogenesis occurs over
Nebraska. That low is forecast to track through Iowa on Wednesday
and eventually into NW Wisconsin by Wednesday evening.
During that time, a 150KT 300MB jet across the southern Great
Lakes will create upper level divergence over Illinois, in the
right entrance region. At the same time, another lobe of the
300mb jet is projected to intensify across Missouri, further
aiding in forcing for upward vertical motion. Southerly 850MB
winds will intensify tonight into the 40-50KT range, becoming a
major player in the moisture and heat transport into the system.
The combination of those features will work to produce widespread
snow across our southern counties early this evening. Meso-scale
models continue to indicate a rogue band of waa farther north of
the main precip shield as it advances into southern Illinois late
this afternoon. It looks to affect areas along I-72 and north
through I-74 between 6pm and 9 pm. That band of snow could even
contain a brief period of freezing rain, per the latest HRRR and
RAP models. Have sped up the northward expansion of PoPs as a
result, but did not introduce freezing rain that far north that
early in the event, as the warm nose will not have reached a
sufficient warmth in that area to produce freezing rain,
according to forecast soundings. Will have to watch that closely,
as freezing rain falling on dry cold ground could cause a sheet of
ice to develop before snow accumulates.
NAM3K/NAM12 guidance are outliers with moderately heavy snow in
our southeast counties south of I-70, while all other models
continue with minor snow amounts in that area this evening before
precip changes through freezing rain to rain. However, have
increased snow amounts in the southeast slightly to account for
the NAMs persistence in keeping those higher snow totals in the
south for several days now. High QPF and nearly convective omega
in the southeast are also factors that support the potential for a
quick burst of a couple inches of snow in those southern
counties. Thunderstorms are already active in Arkansas, and are
poised to surge into SE Illinois late tonight. Instability
projections show 80-100 J/kg of MUCAPE into Lawrence county from
09z-12z tonight (3am-6am). So a rumble of thunder can not be ruled
out.
Snowfall for areas north of I-70 looks similar to our previous
forecasts, with a surge of light to moderate snow northward this
evening and continuing after midnight. Snow amounts were generally
kept in the 1 to 2 inch range through Wed morning. Snow could
linger the longest in Knox and Stark counties, closer to the
colder air mass.
As the 850mb LLJ shifts from a SE direction to the south after
midnight, the warm nose will advance quickly into central IL from
SW to NE, affecting Jacksonville to Springfield initially. All
portions of our forecast area will eventually have the potential
to see icing from freezing rain, with the highest amounts along
and NW of the Illinois river, where 0.10" to 0.15" of ice will be
possible. The duration of the freezing rain portion of the storm
still remains in question. However, forecast soundings continue to
show the warm layer aloft as a nearly isothermal layer surrounding
the freezing line, as surface temps linger near or just below
freezing for several hours. If the surface temps warm more
quickly, and freezing rain transitions to rain sooner, icing
amounts could be diminished.
Another fly in the ointment is a potential quicker end to the
precip on Wed morning. A dry slot aloft has been consistently
forecast to push into Illinois from SW to NE on Wed morning, as
early as 12z in Scott Co to Sangamon Co. That will remove ice
crystals from feeding the precipitating cloud layer, but drizzle
or freezing drizzle could linger much longer than the models show
precip occurring.
Temperatures are expected to rise above freezing Wednesday
afternoon all across C and SE IL. So some melting of ice/snow
would occur Wed afternoon into early evening. However, low temps
Wed night will dip back below freezing, so any lingering moisture
on untreated surfaces will refreeze.
The end result in our messaging has been no change to the Winter
Weather Advisory timing, and wintry travel impacts are likely
across our entire forecast area over the next 18 to 24 hours.
.LONG TERM...(Wednesday night through Tuesday)
ISSUED AT 325 PM CST Tue Feb 19 2019
A dry period is forecast from Wed night through Friday, as a
warming trend develops. Some light rain showers are forecast for
Saturday, as a strong low pressure system develops in western OK
Sat morning and advances quickly toward lower Michigan by Sunday
morning. A cold front will get dragged across Illinois during that
time, with strong jets at the lower and upper levels creating the
potential for severe storms late Saturday afternoon and evening in
our SE counties, mainly S of I-70. SPC continues to indicate that
time frame for severe weather potential in the Day 5 outlook.
Damaging winds and isolated tornadoes also continue to be the
primary hazards. Highs on Saturday could climb near 60 in our SE
counties, with dewpoints into the mid 50s, which would definitely
support strong storms this time of year.
A brief period of freezing rain could also be a part of that
system, mainly NW of the Illinois river late Friday night into Sat
morning.
As that low pressure system departs to the NE on Sunday, rain
could change to snow for a time as colder air returns, before
precip ends by Noon on Sunday. No significant snow or ice accums
are expected from that system, with current model solutions.
A brief dry and cooler period is expected for Monday, but another
low pressure system is expected to shift from the Plains toward
Illinois on Tuesday, bringing rain and snow chances back to the
area.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 600 PM CST Tue Feb 19 2019
VFR conditions currently across the central IL airports will
overcast mid level clouds around 10k ft. Will see possible MVFR
ceilings of 2-3k ft at times this evening, with a band of light
snow spreading in from the sw during mid to late evening from
03-06Z. IFR conditions to develop during overnight as light snow
mixed with and eventually changes to light freezing rain with
vsbys getting as low as 1-2 miles and ceilings dropping below 1k
ft during overnight. Surface temps will rise above freezing toward
dawn at DEC and SPI and by mid morning at PIA and BMI with light
freezing rain changing to light rain/drizzle. Ceilings below 1k ft
Wed morning to rise to 1-1.5k ft by late afternoon. East winds
10-15 kts could have few gusts 15-20 kts tonight. East winds to
veer se around 10 kts Wed morning and then sw during Wed
afternoon.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 6 AM CST Wednesday for ILZ062-063-
066>068-071>073.
Winter Weather Advisory until noon CST Wednesday for ILZ027>031-
036>038-040>057-061.
&&
$$
UPDATE...07
SHORT TERM...Shimon
LONG TERM...Shimon
AVIATION...07
Area Forecast Discussion
National Weather Service Blacksburg VA
831 PM EST Tue Feb 19 2019
.SYNOPSIS...
Low pressure along the Gulf Coast States tonight will track
northeast across the Carolinas by Thursday morning. Moisture
associated with this system will bring a swath of significant
wintry weather to the area tonight into Wednesday evening. Our
weather pattern will remain on the wet side for the remainder of
the week into the weekend as a series of fronts and low
pressure systems track through the region.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
As of 825 PM EST Tuesday...
Radar showing precipitation slowly making its way northeast into
the area this evening but hampered so far by dry air aloft which
remains in the 85h-7h layer per evening RNK raob. Latest short
term models show this finally being overcome across western/southwestern
Virginia by midnight and over points to the northeast shortly
thereafter. However models disagree a bit on just how long the
ptype will remain snow given a slower to evolve event this
evening. Latest HRRR suggests that much of the column will become
isothermal espcly along the I-81 corridor as lift increases and
is able to overcome the warm nose that looks to actually be
above the 85h layer overnight. This scenario with a higher level
warm nose in the past has supported snow longer then more sleet
per a deeper lower layer below freezing after the initial
snowfall. Moisture layer finally looks to shallow out allowing
precip to become more liquid per loss of crystals late tonight
or early Wednesday as the axis of forcing lifts north. This in
conjunction with the HRRR showing more banding after midnight as
the warm front aloft edges north supports bumping up totals a
bit in a strip from BCB to ROA to LYH and points northeast where
deeper colder air will reside longer. Otherwise only some minor
tweaks to slow down pops a bit with all of the area bumping to
categorical pops overnight. Small changes to bump up lows a
degree or two in spots but overall upper 20s/lower 30s.
Previous discussion as of 240 PM EST Tuesday...
Regional/national radar shows band of precipitation extending from
south of I-40 in wester/central NC west across the TN Valley into
Arkansas. This area of precip is making inroads toward the NC
mountains/foothills. However, ground truth reveals most of the
precip is evaporating in NC or barely reaching the ground. As is the
case with dry airmass and increasing moisture transport will be a
battle into seeing precip reach the ground but mountains/higher
ridges will see snow/rain by dusk in NC then moving northward
through the evening as isentropic lift maximizes.
Best frontogenetical forcing/lift along band will reach our southern
CWA this evening and exits to the north overnight. Think along this
axis will be when precip falls the heaviest, and could see some
mesoscale banding of sleet/snow which may bring a quick 1 to 2
inches before precip starts to swing toward freezing rain. This is
more likely in the foothills/mountains.
At the moment our current headlines look good. May see less wintry
precip in the Mountain Empire given decent inverted trough with 8h
temps around +2 to +3 and as wedge strengthens this evening,
southeast flow in the low level increases which will create a
downslope warming effect toward far SW VA. So places like
Saltville/Richlands/Chilhowie may see barely a dusting if any with
snow/sleet with more potential for trace to light icing.
Meanwhile still looks like a solid 1 to 2 tenths of ice over most of
the forecast area with potential for a third of an inch of ice
across the Greenbrier Valley into the Alleghanys. This area is also
the last to switch from snow/sleet to freezing rain late tonight
into early Wed, so snow/sleet amounts will total 3 to 6 inches here.
Further south most will see less than 2 inches of snow/sleet, with
little to none south of the Roanoke River in the piedmont south to
NC.
As we head through the day Wednesday models continue showing warm
nose increasing and eventually the low levels warm enough to change
freezing rain to rain from southwest to northeast, but will still
see sub-freezing temps in the wedge keep freezing rain past dusk
from the Roanoke/Floyd line northward into the Shenandoah Valley to
Lynchburg/Buckingham and Greenbrier.
As far as heavy rain threat, will see greatest rainfall west of our
area, so at this time flooding threat is low.
Models do show a lull in the precip fields behind the best
banding/isentropic lift pushing in from south to north Wednesday, so
may see transition to freezing drizzle/drizzle.
Temps tonight to drop into the upper 20s to lower 30s, then hold
steady or slowly rise in the wedge Wednesday to the lower to mid 30s
while the far southwest VA area warms to the mid 40s with break in
the precip.
Southeast winds will still be gusty across far southern WV into the
Mountain Empire around 35 mph, so this will still be mentioned in
the winter weather headlines.
Confidence is high for winter weather impacts, but lower on
snow/sleet amounts, and medium to high for ice amounts.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
As of 230 PM EST Tuesday...
Winter storm warnings and advisories continue into Wednesday night.
A cold front approaches the region Wednesday evening, ushering in
relatively warmer air and converting any frozen precipitation over
to a cold rain. Unfortunately, the front will slowly move across the
area, depositing another quarter inch or so of rain to an already
water-logged ground. This round of rain may push creeks and streams
above bankfull if they are not already there. The front is expected
to move east of the mountains Thursday morning, then south into
North Carolina by noon. Creek and stream levels will begin to recede
Thursday, but river flooding will remain a concern into the day
Friday, especially along the Roanoke and Dan Rivers.
Temperatures Wednesday night are expected to warm from the lower 30s
to near 40F Thursday morning. Cold air lags well behind the front
Thursday which will help allow temperatures to warm into 50s across
the region.
High pressure will build in Thursday night as the front slides
farther south into the Carolinas. However, dry weather will be brief
as a disturbance over the southern Mississippi Valley throws
moisture over another high pressure surface wedge. Isentropic lift
increases over the area Friday and Friday night producing around a
quarter to half of an inch of liquid precipitation. At this time,
sounding profiles support an all rain event. If models trend colder,
the Greenbrier Valley to the southern Shenandoah Valley could see a
light winter mix as temperatures wet-bulb down below freezing
through the event.
Temperatures Thursday night will drop into the 30s north of the
VA/NC state line, south around 40F. High temperatures Friday will
only warm into the 40s.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
As of 300 PM EST Tuesday...
An upper level trough will swing out of the Rockies and over the
central Plains on Saturday. A surface low will move quickly into the
Ohio Valley by Saturday evening. Pressure falls over the Ohio Valley
will mark the beginning of end for this weekend`s wedge. Until the
wedge and moisture are pushed out of the region by a cold front
Sunday morning, rain will continue to fall over the area Friday
night into Saturday night. Storm total rainfall could be on the
order of 1 to 2 inches for this weekend`s event. With very little
drying between Wednesday`s and this weekend`s event, flooding of
creeks, streams and rivers are again possible. We will know more
once we get this first system out of the way.
Cold high pressure will allow the area to dry out Sunday through
Tuesday. Our next chance for precipitation is expected next Tuesday
night into Wednesday.
Temperatures are expected to be cooler than normal Friday night and
Saturday, then near normal for the first part of next week.
&&
.AVIATION /01Z WEDNESDAY THROUGH SUNDAY/...
As of 600 PM EST Tuesday...
VFR early this evening will transition to MVFR from south to
north with cigs lowering including arrival of wintry
precipitation across the area between 00z/7PM and 06z/1AM. Will
see snow at the start on all TAF sites, except mixed with rain
at KDAN and possibly KROA/KLYH/KBCB, then shift over after 06z
to sleet to freezing rain while cigs/vsbys linger in LIFR to low
end MVFR range, but confidence is higher on sub 1K feet cigs.
There may be some weakening of the precip after 12z/7AM
Wednesday, but still enough low level moisture to keep freezing
rain/freezing drizzle around, except changing to rain
along/west of a KBKW-KBLF-KMKJ line by afternoon.
Guidance has the winds picking up from the southeast in the
mountains as a strong low level jet moves into the area after
00Z/7PM. Winds at KBLF may gusts as high as 35 knots overnight.
Confidence in the aviation forecast is above average.
Extended Aviation Discussion...
Wintry precipitation will gradually transition to all rain from
south to north by early Wednesday evening as warmer air
arrives. Expect widespread sub-VFR conditions through much of
the day.
A frontal boundary will meander around the region into the start
of the weekend, along with several areas of low pressure moving
along this boundary. This will keep the potential for
rain and sub-VFR conditions across the area through Sunday.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...Winter Storm Warning until 8 PM EST Wednesday for VAZ014-017-
018-022-032-033.
Winter Storm Warning until midnight EST Wednesday night for
VAZ019-020-023-024-034-035-045>047.
Winter Storm Warning until 4 PM EST Wednesday for VAZ010>013-
015-016.
Winter Weather Advisory until noon EST Wednesday for VAZ007-
009.
Winter Weather Advisory until 6 PM EST Wednesday for VAZ043-
044-058-059.
NC...Winter Storm Warning until 4 PM EST Wednesday for NCZ001>003-
018-019.
Winter Weather Advisory until 6 PM EST Wednesday for
NCZ004>006-020.
WV...Winter Storm Warning until 8 PM EST Wednesday for WVZ044.
Winter Storm Warning until midnight EST Wednesday night for
WVZ507-508.
Winter Storm Warning until 4 PM EST Wednesday for WVZ042-043.
&&
$$
SYNOPSIS...DS/KK/WP
NEAR TERM...JH/WP
SHORT TERM...RCS
LONG TERM...RCS
AVIATION...AMS/JH/NF/WP