Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/17/19
Area Forecast Discussion
National Weather Service Columbia SC
636 PM EST Sat Feb 16 2019
.SYNOPSIS...
A cold front is pushing southward through the CSRA this evening
with cool air flowing into the area overnight. Expect a
continued wet pattern Sunday through late next week as a strong
SW upper flow, with a series of embedded upper disturbances and
resultant surface waves, combine with abundant atmospheric
moisture to provide good chances of rain.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
The cold front has pushed into the CSRA this evening. With much
of the deeper moisture moved out of the area and PWAT values
falling below one inch have kept pops at slight chance or less
overnight. Cool air will continue to flow into the area from the
northeast bringing lows into the upper 30s in the north to upper
40s in the south. An upper level disturbance approaches from
the west around daybreak increasing the chance of rain over the
western Midlands and northern CSRA.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/...
Weak surface wedge pattern will continue through much of the
forecast period. Weak shortwaves will approach from the west,
bringing moisture that will ride up and over the cooler surface
air. One system is forecast to move through the area on Sunday,
with the best dynamics and rain chances across the northern half
of the forecast area. Southern counties may only see light
rainfall by late morning, and may even stay dry. Northern
counties will pick up some light to moderate rainfall through
the late morning into the afternoon as the system moves across
the area. Temperatures Sunday will be quite varied and highly
dependent upon where the southern and eastern edge of the wedge
front is. Highs in the low to mid 40s are likely across the
northern cwa, the southern Midlands and CSRA may raise into the 60s
during the afternoon. Temperatures should increase slightly
through the night with steady warm advection over the area.
Rain continues overnight Sunday night into Monday, then the
precip is expected to push off to the east during the day
Monday. Some drying may occur Monday night as the area is
between systems for a brief period. Temperatures Monday moderate
due to the wedge getting pushed out for a short period of time.
Highs in the 60s everywhere on Monday.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
By Tuesday the surface wedge pattern will set back up across the
eastern slopes of the Appalachians, bringing a return to cooler
and wetter conditions. Upper pattern remains southwesterly,
bringing Gulf moisture northward with each approaching shortwave
system. Next round of significant rainfall will occur Tuesday
through Thursday. Although the highest chances remain across
the western portions of the cwa, the entire forecast area will
see some amount of rainfall through the period. Another possible
front near the end of the week brings yet another chance for
rainfall to the region. Temperatures tricky and depend on
amount of clouds, location of wedge, and rainfall. Went with a
general blend.
&&
.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
Restrictions expected to dominate the 24-hour TAF period.
A cold front was moving south across the area early this
evening. At 23z, the front was located near the AGS terminal
area. Behind the front, a surface ridge over central North
Carolina and Virginia will build southwest across the region.
MVFR ceilings expected behind the front through the overnight
due to cold air damming. This is supported by the latest HRRR
and Lamp Guidance. After 12z Sunday, the guidance is suggesting
ceilings will lower to IFR most areas as low level moisture
increases. As weak lift develops during the day, expect patchy
light rain or drizzle at times, possibly more significant late.
This may result in reduced visibility at times.
EXTENDED AVIATION OUTLOOK...Restrictions possible at times
through mid week as a series of low pressure systems move
through or near the region.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
&&
$$
Area Forecast Discussion
National Weather Service Caribou ME
918 PM EST Sat Feb 16 2019
.SYNOPSIS...
High pressure will build across the region tonight through
Wednesday night. Low pressure will approach the region on
Thursday.
&&
.NEAR TERM /THROUGH SUNDAY/...
9:18 pm update: There are a few streamers affecting parts of
Aroostook County and into northern Penobscot and northern
Washington Counties. We have picked up 0.6" of an inch of fluffy
snow at the WFO this evening while Presque Isle has only had
flurries. The HRRR showed one band of snow across northeast
Aroostook County, but had it diminishing by now. Expect as high
pressure builds toward the region that these streamers will
diminish, but based on the latest radar returns will have
isolated to scattered snow showers until around midnight.
Previous discussion:
Low pressure located to the north of the State will continue to
move away to the northeast tonight. Snow showers across the
north are expected through early evening then gradual clearing
is expected. Central and southern areas are expected to remain
mostly clear. Strong high pressure is expected to build in from
the northwest on Sunday with mostly sunny skies expected. Also a
colder air mass is expected to move in ahead of the high on
Sunday.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
High pressure looks to dominate the short term with mostly dry wx
expected. Winds look to decouple Mon morning and under moclear skies
acrs the north and significant snowpack min temps wl lkly be blo
guidance. Hv contd with the idea of minus teens acrs portions of
northern Aroostook and blo zero temps to the north of Katahdin.
Lopres system progged to move off the mid-Atlantic coast Mon morning
may bring a glancing blow to the coast Mon morning with light snow
showers. 12z med range guidance do not differ much fm their sfc low
locations to the south of Cape Cod by 12z Mon, however they do
differ on extent of pcpn shield extending to the north. This lkly
centers on the strength of the high building ovr the area with CMC
strongest with hipres and NAM weakest. GFS looks to be the
compromise and given the discrepancies in the solns hv contd with
slgt chc pops along the coast for Mon mrng.
As low shifts south of Nova Scotia Mon night nrly flow conts to
bring in colder H8 temps. Mins on Tue mrng may be a touch cooler
than Mon morning if not for the winds staying up as pressure
gradient tightens with high building in fm the west and low exiting
to the east. High temps on Tue wl lkly be colder than Mon under
contd cold advection. Sunny skies and a stronger sun angle may
provide warmer temps than currently fcst for highs.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
Sfc high conts to build in fm the west cresting ovr the area Wed
evng. High quickly builds east Wed night with sfc low mvg into the
Great Lakes drg the ovrngt hrs and another low ejecting off of the
mid-Atlantic coast Thu morning. Sfc low mvg thru the Great Lks wl
quickly fill as it heads into New England while low mvg into the
Atlantic intensifies drg the day on Thu. This wl lkly set up another
Norlun trough affecting coastal zones where inverted trof sets up.
At the same time an upr lvl trof mvs acrs nrn portion of CWA leading
to light snow at all locations drg the day. Expect temps thru the
longer term wl moderate to abv normal by the end of the week as upr
flow bcms zonal.
&&
.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
NEAR TERM: Patchy MVFR at times late this evening at the
Aroostook County terminals in patches of lower clouds and
isolated snow showers. Otherwise, VFR conditions are expected
tonight and Sunday.
SHORT TERM: VFR Sun afternoon through Mon morning. Occasional
MVFR cigs may occur on Mon morning over Downeast terminals with
moisture from low pressure tracking well to the south. May see
MVFR cigs north of HUL in the afternoon in low stratus. VFR
expected Mon night through Wed before restrictions lower again
Thu morning.
&&
.MARINE...
NEAR TERM: Will use the Nam to initialize winds. For Waves: The
primary wave system is currently long period residual
southeasterly swell (currently 7 feet/9 seconds) from yesterdays
fetch across the Gulf of Maine. This system will continue to
subside tonight and is expected to all below 5 feet later this
evening. This is also a secondary off-shore wind wave which will
remain through tonight. Total Water Level: Will keep the Base
Tide Anomaly along the coast near +0.10 since the surge guidance
continues to perform well. Expect a reverse surge with off-shore
wind this evening then zero surge through Monday. In Bangor have
initialized the Base Tide Anomaly based on RFC guidance then
will adjust for surge/reverse surge.
SHORT TERM: SCA level winds may be reached Mon night thru Wed
morning, with a possible 6-hr window Tue morning where they drop
blo 25ks.
&&
.CAR WATCHES/WARNINGS/ADVISORIES...
ME...None.
MARINE...Small Craft Advisory until 4 AM EST Sunday for ANZ050-051.
&&
$$
Near Term...CB/Mignone
Short Term...Farrar
Long Term...Farrar
Aviation...CB/Mignone/Farrar
Marine...CB/Mignone/Farrar
Area Forecast Discussion
National Weather Service Cheyenne WY
428 PM MST Sat Feb 16 2019
.SHORT TERM...(This evening through Sunday)
Issued at 341 PM MST Sat Feb 16 2019
Two hazards and resultant impacts to focus on next 24 hours:
1) Localized moderate snow bands and snow squalls this afternoon
to early evening along with scattered snow showers overnight into
early Sunday. Impacts could be difficult driving conditions at
times, especially in localized heavier snow bands/squalls and in
the higher terrain along I-80.
2) Cold wind chills of negative 5F to negative 15 degrees will
occur tonight into early Sunday and even colder wind chills are
expected Sunday night into Monday morning of negative 15 to
negative 25 degrees for a larger portions of the area. A Wind
Chill Advisory will likely be needed for Sunday night into Monday.
Weather Details: Modest divergence aloft with localized near-
surface convergence is ongoing underneath a shortwave trough
passage this afternoon across southeast Wyoming and Nebraska
Panhandle. A localized boundary was noted on satellite imagery
this early afternoon and this is the location of a now developing
narrow snow band across west Laramie County into Kimball County,
Nebraska. NAM and HRRR soundings indicate 50-100 J/Kg of low-level
CAPE with steep lapse rates present. In combination with elevated
snow squall parameter values, hi-res guidance indicates a
favorable environment for localized banding of snow showers that
could reduce visibility quickly across short distances. This
appears to be ongoing at this time near Kimball, NE. Additional
scattered snow showers are shifting southeast across the northern
Laramie Mountains and additional local bands and squalls will need
to be monitored for through the early evening hours. Low-level
lapse rates and instability will decrease through the mid evening
with localized banding likely to decrease with the shortwave
trough passage to the east. Meanwhile, the Sierra Madre and Snowy
Mountain Ranges will pick up an additional 3 to 6 inches of snow
through this evening where a Winter Weather Advisory remains in
effect until 11pm tonight. Some additional light snow showers will
linter tonight and Sunday but overall intensity will be reduced.
Following the passage of the trough to the east tonight, cold air
advection will shift over the region tonight and early Sunday.
Much colder temperatures expected tomorrow and even more so early
next week. Wind chill values will fall below zero Sunday night and
even further on Monday. Wind Chill advisories will likely be
needed Sunday into Monday for a large portion of the area.
Temperatures will remain below normal through all of the short
term and much of the long term as well.
.LONG TERM...(Sunday through Friday)
Issued at 300 AM MST Sat Feb 16 2019
A series of short waves will rotate through the base of the long
wave upper trough over the western CONUS through much of next
week. This pattern favors much below normal temperatures through
Tuesday with daytime highs in the teens and 20s and nighttime lows
from 5 to -10 degrees. Could be dealing with wind chill headlines
Sunday night and Monday night with wind chills from -15 to -25
degrees. Temperatures will moderate closer to normal Wednesday
through Friday with highs in the 20s and 30s. Windy Wednesday,
especially the I-25 corridor between Wheatland and Chugwater with
700mb winds around 40 kt and CAG-BRX 850mb gradients 55-65mtrs.
Snow showers will be confined to the southeast WY mountains and
high plains into parts of western NE Sunday through Tuesday, and
again Thursday through Friday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 428 PM MST Sat Feb 16 2019
Latest GOES-16 Satellite and local radar tracking bands of heavy,
localized bands of snow moving across southeastern WY and into the
NE Panhandle. Expecting vicinity snow showers for most of the
terminals with reduced conditions at KSNY and KBFF for the next
couple hours. Timing will likely need to be adjusted to
accommodate these bands and their cessation. Low ceilings and
gusty winds likely to continue through the overnight and morning
periods. Periods of MVFR to IFR conditions possible.
&&
.FIRE WEATHER...
Issued at 341 PM MST Sat Feb 16 2019
Scattered snow showers will move across the High Plains
and the higher terrain this afternoon and evening. Snow will taper down
Sunday but winds will remain elevated at 20 to 30 mph across southeast
Wyoming. Fire weather concerns will be minimal over the next several days
as below normal temperatures will hold on through the weekend into
early next week. Relative humidities will stay above critical values.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Weather Advisory until 11 PM MST this evening for WYZ112-
114.
NE...None.
&&
$$
SHORT TERM...JSA
LONG TERM...MAJ
AVIATION...WM
FIRE WEATHER...JSA
Area Forecast Discussion
National Weather Service Des Moines IA
1001 PM CST Sat Feb 16 2019
...Headline Decision Update...
.UPDATE...
Issued at 948 PM CST Sat Feb 16 2019
Have upgraded a small area to Winter Storm Warning based on law
enforcement and public reports of 4 to 5 inches across Adams,
Taylor, and Ringgold Counties in our area and Page and Montgomery
Counties in Omaha`s area. The initial burst of snow has been
quite intense with Murray reporting 1.4 inches in one hour and
Diagonal reporting 2 inches in an hour. Rates will taper off
overnight, but with 4 to 5 inches already on the ground seems
feasible to get 6 inches in 12 hours. As stated in the earlier
update, QPF from short range guidance like CONSShort, HRRR, NBM,
and 00z NAM all point to near/around the warned area being favored
for the higher QPF and thus snow amounts. Therefore, QPF amounts
were increased and expect the warned area to be around 6 to 7
inches by 12z. Rest of the forecast remains on track.
UPDATE Issued at 845 PM CST Sat Feb 16 2019
00z KDVN RAOB showed a very dry layer of air between 850 and
700mb and this was showing up on KDMX radar as a ring of
reflectivities around the radar. As of 830pm, that dry layer is
around 300 m/1000 feet. This dry layer will continue to shrink
with snow expected in the Des Moines metro between 9 and 10pm
depending on what side of town someone lives on. This quick top
down saturation occurred at KOAX/KOMA with the 00z RAOB having
dry air in the lowest 1km near balloon release time around 23z,
but by 01z snow was reported at KOMA. The snow intensity per
Iowa and Nebraska DOT plow cams has shown moderate to heavy snow
with roads going from dry to snow covered in the matter of an
hour. KOMA had already measured 2 inches a little after 8pm, which
was roughly an hour after it started. The same has occurred in
Diagonal (Ringgold County). Visibility is also dropping below a
mile and at times under a quarter of a mile such as at Clarinda,
Shenandoah, and Red Oak. And with light winds, this is all rate
driven visibility reduction. Have been mulling over an upgrade to
winter storm warning with 1 in/hr rates likely for a 3 to 5 hour
period at any given location, especially southern Iowa. 00z NAM
and latest runs of NBM and HRRR have an area centered around
Atlantic that has about two tenths more QPF in the 0-6z period
(e.g. now), which would yield another 2 to 3 inches of snow not
currently in the forecast. While the initial burst will yield
between 1 to 2 inch/hr rates, it may prove challenging to pin down
an area that will pick up 6 inches in 12 hours (criteria), but
will be making some calls across southwest forecast area to see
what has fallen and make a determination.
&&
.SHORT TERM.../Tonight through Sunday/
Issued at 300 PM CST Sat Feb 16 2019
An expansive area of cyclonic flow continues over the western
CONUS this afternoon. Two embedded shortwaves noted on water vapor
will impact the short term forecast, with one shortwave currently
crossing eastern MT and another moving out of the Four Corners
region. These waves will gradually attempt phase into a broad
upper level low over the Dakotas during the next 24 hours. This
will bring a prolonged period of accumulating snowfall to the
state beginning this evening and persisting through much of
Sunday.
Models in solid agreement with a dramatic increase in deep layer
forcing for ascent passing through the northern Plains today,
reaching western Iowa by early evening. HREF/RAP/HRRR have
consistently advertised the potential for 1"+/hr snowfall rates as
the initial snowfall spreads through southwest and central Iowa,
which is a reasonable outcome as a pocket of low mid-level EPV may
create a favorable environment for the release of upright
instability. RAP/HRRR also put their omega max through the DGZ
layer, so snowfall should efficiently accumulate early on in the
event. Any concerns with top-down saturation should be overcome
quickly given the enhanced vertical motion. Forcing for ascent wanes
tomorrow as the upper low occludes over the Dakotas, but
persistent weak lift through a deepening dendritic layer keeps
light to moderate snow around the much of the day. Higher snowfall
totals during the daylight hours should progress northward as the
QPF max shifts to northern Iowa. Average SLR hangs above climo
with a modestly deep and saturated dendritic layer. Total accum
results in a broad 4-7 inches across most of the area by Sunday
evening. Locally higher amounts are possible in central Iowa,
especially if the intense snowfall rates at the onset hang on for
an hour or two longer than currently forecast.
As for headline decisions, opted to maintain status quo with the
winter weather advisory after collaboration with neighboring
offices. Accumulations still on the fringe of warning criteria of
6"/12 hr or 8"/24 hr, but restrained winds this time around
should limit the potential severity of travel impacts. Would not
be surprised if some areas hit warning criteria snowfall, but
those locations would be tough to confidently pin down at the
moment.
.LONG TERM.../Sunday night through Saturday/
Issued at 300 PM CST Sat Feb 16 2019
As has been the case over the past month, Iowa and the region remain
in an active scenario in the longer term. However, the state will
see relatively quiet weather from Monday into Tuesday as surface
ridging builds toward the state and general subsidence occurs over
the state. During this time, the mean western trof will be
reinforced by another shortwave dropping into the Great Basin and
then ejecting east northeast on Tuesday. This system is forecast to
affect much of the southeast half of the region including Iowa
Tuesday night into early Wednesday. GFS and Euro have begun to
converge on their solution with isentropic lift increasing later
Tuesday along with strengthening mid level Q-convergence/dynamic
forcing during the evening and into the overnight. Deep saturation
occurs by the evening with snow spreading northeast into the state.
The GFS is slightly less amplified and bit faster than the Euro with
the progression of the system and overall fields. Both have snow on
Tuesday night but GFS is essentially done by 12Z Wednesday. The
more amplified Euro lingers longer and has more resultant QPF into
Wendesday morning before departing by midday. Most of the forecast
area will see light to moderate accumulations although locally heavy
amounts are reasonable. Winds will thankfully not be too strong
with this event which will limit blowing snow although the full
ditches will make it more likely even with the lighter winds.
Cold advection is limited on the backside of the system as deep
southwest flow continues across the CONUS. Warm advection will kick
in on Tuesday and persist into Friday with temperatures responding
in kind ahead of the next system. Given the inconsistencies in the
handling of the system next weekend, confidence is currently quite
low with how this system will evolve and the potential impact across
Iowa.
&&
.AVIATION.../For the 00Z TAFS through 00Z Sunday evening/
Issued at 545 PM CST Sat Feb 16 2019
VFR conditions will rapidly deteriorate through the evening hours
from southwest to northeast across central Iowa as a band of
moderate to heavy snow arrives. This will bring widespread IFR and
LIFR restrictions overnight and perhaps an isolated, short period
of VLIFR. The worst expected conditions for each terminal has
been placed in a TEMPO group. After the initial burst of heavier
snow, a prolonged period of light snow with IFR and MVFR
restrictions will linger through much of the day Sunday. Winds
from the east will be light at 5 to 15 knots switching to north or
northeast Sunday morning into Sunday afternoon.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 6 PM CST Sunday for IAZ004>007-
015>017-023>028-033>039-044>050-060>062-073>075-084>086-096-097.
Winter Storm Warning until 6 PM CST Sunday for IAZ057>059-
070>072-081>083.
Winter Weather Advisory until noon CST Sunday for IAZ092>095.
&&
$$
UPDATE...Ansorge
SHORT TERM...Martin
LONG TERM...Cogil
AVIATION...Ansorge
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
722 PM EST Sat Feb 16 2019
.UPDATE...
Although the late afternoon clearing trend across the Saginaw Valley
has persisted and expanded into Flint and the eastern thumb, there is
evidence that the Lake Huron moisture plume will continue to
influence a good portion of the area during the late evening into the
overnight as the low level flow continues to veer more northeasterly.
The low level flow will actually veer easterly toward Sun morning.
The extent of low clouds across Lake Erie and northern Ohio suggests
that the more pessimistic cloud forecast across metro Detroit/Ann
Arbor and points south looks reasonable. Farther north, while there
may be some additional periods of lake clouds, observational evidence
suggests there will at least be significant periods of clear skies.
The forecast will be updated to have a more graduation in sky cover,
from most clear across Midland/Bay counties to most cloudy along the
M-59 corridor and points south. The nighttime temperature forecast
will also be adjusted accordingly; a little warmer in south and
colder in the north based on nighttime sky coverage.
&&
.PREV DISCUSSION...
Issued at 608 PM EST Sat Feb 16 2019
AVIATION...
Although it took most of the afternoon, some significant clearing of
the MVFR strato cu field has occurred across the Saginaw Valley
region, aided by some downslope off the higher terrain of nrn Lower
Mi. Current satellite trends have this clearing pushing into the
Flint area by TAF issuance. The probability of whether this clearing
trend persists through the evening or if there is low cloud
redevelopment during the night poses a good degree of uncertainty in
the terminals.
The low level flow across southern Lake Huron will veer from north
to east-northeast during the night. This added moisture flux off the
lake, combined with some differential thermal advection actually
deepening the low level inversion, will likely result in a sustained
strato cu field, likely building back into areas which have already
cleared. Some better probabilities for clearing look to take hold
after daybreak Sunday into early Sun afternoon as strengthening
easterly flow temporarily advects some drier air into Se Mi. Light
snow will then overspread the area late Sun afternoon (after 20Z),
resulting in lowering cigs and vsby.
For DTW...With the low level flow already in the process of turning
northeast over southern Lake Huron, it is doubtful any of the
clearing to the north will make it to metro. Even as the low level
flow turns more easterly late tonight, there is still a considerable
amount of strato cu across Lake Erie and northeast Ohio. Thus a more
pessimistic approach to cloud cover seems warranted. The potential
for lowering inversion heights overnight may also force cigs below
2k feet. Probabilistic guidance suggests light snow arriving in
metro around 20Z Sunday.
DTW THRESHOLD PROBABILITIES...
* High in ceilings below 5000 feet this evening. Moderate overnight
through Sunday.
* High that precip will fall as all snow Sunday afternoon and
evening.
PREV DISCUSSION...
Issued at 332 PM EST Sat Feb 16 2019
DISCUSSION...
Widespread snow showers are winding down this afternoon as
increasing subsidence and diurnal heating erode moisture depth and
inhibit dendrite production within the extensive plume of lake
stratocu. Lowered highs a second time for this afternoon given
observational evidence that boundary layer flow is already beginning
to veer to a more favorable overlake fetch that will ensure some
persistence of clouds for most or all of the aftn and likely filling
in again tonight. Went ahead and raised lows 3 to 5 degrees tonight
as well due to clouds.
Focus for Sunday will be on potential for widespread accumulating
snow as a number of the NWP suite which are struggling to play catch-
up to the next surge of a very energized subtropical jet are
catching up to the NAM family which remains qualitatively unchanged
for its last several runs. To lesser consequence, the NWP have also
universally overestimated confluent flow over NW Canada which has
been modeled to impinge on the Great Lakes. The combined result of
these factors is the general trend in the guidance toward a faster
and more poleward solution for Sunday.
Strong isentropic ascent will overspread the CWA 12-18z Sunday as
the LLJ evolves northward almost completely orthogonal to the upper
jet. Meaningful upper jet dynamics, however, will be long gone early
in the day as the early push of support will mainly serve to
invigorate the LLJ and help saturate the column while producing just
a few isolated snow showers or virga during the morning. In general,
expect increasing probability of virga with northward extent during
the afternoon as well. The earliest onset is forecast to occur at
the nose of the incoming mid-level theta-e ridge for Detroit and
points south no earlier than 1 PM local time.
Cross-sections indicate there really is not much to this
event from a forcing perspective. It will simply be strong WAA
serving to completely erode static stability between about 800mb and
500mb over the CWA. There will exist a tendency for organization
along the aforementioned convergent theta-e ridge which is currently
modeled to push up to about the M59 corridor in time for the evening
commute before the pivot out of the area begins. H85 to H7 layer
average specific humidity ranging from 2.5 g/kg in the M59 counties
to well over 3 g/kg near the Ohio border will certainly be capable
of supporting locally higher amounts in should a greater degree of
organization materialize. For now, a general 1 to 2 accumulation
potential M-59 south looks good with less to the north given delayed
onset and dry air. Further, once low-level saturation is complete
over the northern CWA, the strong jet will only be a detriment as it
forces the aggressive dry slot over area after 00z both diminishing
ascent and deep layer moisture quality. The potential for any higher
end accums would exist within a narrow band perhaps as wide as a
county or less with an upper end potential of a localized 4" given
limited forcing and duration. The 12z NAM12 gives an overzealous nod
to this potential as the solution implodes due to convective
feedback within this favored corridor, while the 12z NAMNest offers
a more subdued response and provides the general framework for the
afternoon forecast package. In fact the 18z HRRR appears to have
latched onto this potential as well. The existence of neutral
stability with pockets of shallow conditional instability and
ongoing trend of the NWP struggling to capture just how much energy
will be zipping by Lower Michigan on Sunday suggest a bit of caution
when it comes to expressing confidence in both location and
magnitude of snow, hence the extended paragraph dedicated to
outlining what currently presents as a lower probability outcome of
something in excess of 2 inches. Worth a note that the shallow 0-
0.5km unstable layer over Lake Huron will likely further slightly
enhance the moisture field near the ground. Progged thermodynamic
profiles will support event-average snow ratios near climo, around
13:1 - less to the north. Lingering boundary layer moisture and
descending dry air aloft will support low ratio snow/flurries
lingering into Monday morning.
Active jet stream will remain directed across the CONUS through the
majority of next week and SE Michigan`s placement on the poleward
side of the jet max among plenty of confluence aloft will result in
mostly quiet conditions. The exception will be during the midweek
period when potent Pacific shortwave energy results in amplification
of the longwave locally and brings a good chance for precip via
isentropic ascent. Current trends suggest light snow starting
Wednesday morning and lasting into the evening, with a chance for
some rain to mix in on the tail end as a surge of warmer temps
reaches the area. Temperatures will take on a rising trend through
the week, with highs increasing from the 20s on Tuesday to the upper
30s/lower 40s by Saturday. Lows in the teens and 20s will be likely.
The next chance for rain comes Saturday with a deep trough digging
through the central CONUS.
MARINE...
Light winds are expected into tonight as high pressure builds across
the area. Moderate easterly winds will then develop on Sunday as low
pressure tracks just south of the Ohio Valley. Winds will back to
the northeast Sunday night and north on Monday as this low pressure
continues to the east. Wind gusts will peak late Sunday into Sunday
night at 25 to 30 knots and then decrease from Monday into Tuesday
as another high pressure system builds into the region as winds back
further to the northwest. Easterly winds will then return by midweek
as the next low pressure system encroaches on the region. No
headlines are anticipated at this time as wind gusts remain below
gale criteria and nearshore areas remain largely ice covered with
limited wave action.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&
$$
UPDATE.......SC
AVIATION.....SC
DISCUSSION...JVC/TF
MARINE.......DG
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Grand Rapids MI
1040 PM EST Sat Feb 16 2019
LATEST UPDATE...
Update
.SYNOPSIS...
Issued at 131 PM EST Sat Feb 16 2019
-Continued Cold
-Light snow Sunday Afternoon into Sunday night with an inch or
two possible
-Snow likely late Tuesday night and Wednesday
&&
.UPDATE...
Issued at 1040 PM EST Sat Feb 16 2019
I have increased the risk of snow late Sunday afternoon into
early Sunday evening. I also increased the snow amounts to 2 to
3" in the I-69 area for that same time frame.
This is based on the consistency of NAMDNG, NAM12 and HRRR
operational runs (NAM12 since the 16th 00z which continues to show
in increased QPF farther north and west and the HRRR 30 hour run
from the 18z and 00z runs). The NAM shows a decent area of mid-
level FGEN (850 to 700 mb) in the Sunday 7 pm till Monday 1 am
time frame near and south of I-94. This is in exit region of the
upper jet and there is a decent cold conveyor belt over this area.
Also we have decent isentropic ascent over the area near and
south of I-96 from mid day Sunday into late evening Sunday. All of
this leads me to believe we could see 2-3" of snow fall from
around 3 pm till 10 pm in the I-69 area Sunday.
So, bottom line, I have higher pop and higher snowfall amounts
near and south of I-96 but the emphasis is in the I-69 area for
Sunday evening.
&&
.DISCUSSION...(This evening through next Saturday)
Issued at 131 PM EST Sat Feb 16 2019
The main challenges deal with the potential impacts from the next
couple of storm systems.
The first system arrives on Sunday. Currently the dry airmass
in place will act to slow the arrival of the snow so the morning
should be mostly dry. Around noon the moisture deepens up as the
warm air advection strengths and mid level height falls occur. A
broad area of mostly light snow should move in and basically stay
over the area through much of Sunday night. The best forcing and
lift is over the southern half of the CWA where upwards of 2
inches looks possible. North of Grand Rapids the potential for
accumulations looks rather low. Typical of minor accumulation
events...there should be some slick spots on the roads Sunday
afternoon into Sunday night and possibly for the start of Monday.
A strong and deep southwesterly mid to upper level flow pattern
sets up for the middle part of the week from TX to the Great Lakes
Region. Gulf moisture gets draw into this system. Models are in
relative agreement in showing two main areas of heavy
precipitation with this event. One to the west of MI...where the
mid level wave tracks through resulting in stronger height falls.
The second will be in the OH Valley where the moisture convergence and
lift will be maximized around the low level jet. Here in MI we
will be in the middle with what looks like another drawn out
lighter snow event. This could be a low end advisory event...with
the main period of snow expected to be from later Tuesday night
night into Wednesday evening. There is still potential for heavier
precipitation here in MI...it just does not look like the most
likely scenario at this time.
Stay tuned for next weekend as the latest model runs are trying to
wind up a stronger storm for the Great Lakes Region.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 639 PM EST Sat Feb 16 2019
The area of MVFR cigs is slowly eroding to the south as clear
skies spread in from the north. It would seem the eroding of the
clouds will not get to much farther south this evening. However
the hi res HRRR shows otherwise, it has all TAF sites VFR by 02z.
Even there through the clearly does not last long as the system or
our west moves in the low level moisture increases and clouds
should come back. All TAF sites should be at least MVFR due to
clouds by 12z.
Then the question arises as to what the snow will do with this
next system. Some models show a lot of low level dry air while
others do not. There is strong mid level lift by 12z over most of
the GRR CWA, which could mean IFR in snow. For now I will
compromise between the models and delay the start of IFR in snow
till the afternoon. I do think all TAF sites will be IFR due to
visibilities in snow by mid to late afternoon. Clearly this would
mean significant icing in the clouds so one should consider that
too. Winds will not be overly strong, mostly east - northeast
around 10 knots during the day Sunday.
&&
.HYDROLOGY...
Issued at 1231 PM EST Sat Feb 16 2019
All the rivers in our area have now recovered or are falling
substantially after the snowmelt and rain events from earlier this
month. Several of our rivers do remain near bankfull, including the
Pere Marquette (at Scottville), the Maple River (at Maple Rapids),
the Grand River (near Ionia), and the Looking Glass River (near
Eagle). However, no significant renewed rises are expected on any of
our rivers in the next week.
There continues to be a major ice jam causing ongoing flooding in
the City of Portland. Water levels there will continue to fluctuate
up and down in response to shifting and changing ice conditions.
There is another ice jam that we are monitoring near Eastmanville,
near the 68th Avenue bridge. This ice jam is currently fairly small,
and is not currently resulting in additional flooding. There are no
ice jams in the Grand Rapids area, but we are still monitoring that
potential as the water will remain high for at least several days.
The weather over the next week looks cooler than normal and mostly
dry apart from chances for snow Sunday into Monday, and again
Wednesday. Any precipitation amounts appear to be light. These below
freezing temperatures will also limit additional snowmelt and allow
the rivers to continue to fall, however the cold temperatures will
also help maintain river ice. No significant warmups are expected to
cause any appreciable melting of snow.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...WDM
SYNOPSIS...MJS
DISCUSSION...MJS
AVIATION...WDM
HYDROLOGY...ANH
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1000 PM EST Sat Feb 16 2019
.SYNOPSIS...
A moist stationary front located just south of our area will
begin moving north tonight and Sunday as a warm front as low
pressure enhances rainfall. High pressure to our north should keep
any rain limited on Monday. As we get closer to mid week, a series
of low pressure systems will track from southwest to northeast
across the Southeast states, resulting in a persistent moist pattern
through most of the week. The heaviest rainfall is expected during
the second half of the week.
&&
.NEAR TERM /THROUGH SUNDAY/...
As of 945 PM EST Saturday: Some current developments will bear close
watching over the next couple of hours. We are starting to see some
very reduced visibilities in low clouds and fog in the upslope
sections along the northern Blue Ridge mountains late this evening,
and this fog will likely spread southwest down toward the Mount
Mitchell area through the early morning hours. Will issue a Special
Weather Statement for patchy dense fog at this point and monitor it
for a Dense Fog Advisory if it gets worse.
We are also closely watching surface wet bulb temperatures along
this same northern Blue Ridge mountain area, and they are now down
in the upper 30s and continuing to slowly fall. They still have a
way to go to bottom out around the freezing mark for some Sunday
morning light icing to occur, but the models have been spot on with
the cooling so far and the latest RAP runs and ensembles still
insist on plenty of lower 30s temperatures around daybreak. The main
point of contention right now is that the RAP is very dry in the
Winter Weather Advisory area overnight through Sunday morning, while
the NAM is very fast to bring QPF back in, indeed suggesting that
some precipitation should already be occurring. The truth likely
lies in between and this suggests that no changes are needed to the
area or timing of the Winter Weather Advisory for light freezing
rain accumulations Sunday morning. Still anticipate a light glaze on
elevated surfaces through the morning hours in the advisory zones
near the Blue Ridge escarpment.
Otherwise, the back-door cold front has wrapped solidly south of the
forecast area. Moisture return, and the redevelopment of low-level
upglide and mid-level dpva late tonight, should help to force precip
moving back in from the W/SW even as the low-level northeasterly
flow locks in the cold air damming wedge and forces light precip
near the Blue Ridge Escarpment. As mentioned, the narrow corridor of
light freezing rain along/near the escarpment is by no means a
certainty, but think the current advisory captures well the expected
location/time if icing issues develop. Temperatures along the chilly
northern Blue Ridge area should rise above freezing around noon.
Forcing improves throughout Sunday, so the precip probability
steadily increases from the west and reaches the categorical range
everywhere by the end of the day. Not expecting any truly
significant amounts with what should be the second in a succession
of wet systems, but it will only serve to further wet down the
region and contribute to our potential for more serious issues as we
work through the next week. High temps will be on the order of ten
degrees below normal owing to the wedge.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
As of 200 PM EST Saturday: Not much change to the overall synoptic
pattern over the short term as a large wrn trof will slowly dig as
it interacts with a sub-trop high. This will keep a 190 kt jet core
and better div/conv zones situated across the OH valley and into
the Mid/Atl. However...embedded waves of h5 energy south of the jet
stream will support a couple weak...yet very moist sfc lows over the
Deep South which will track ne/rd thru the period. Precip will be
ongoing across most locales at 00z Mon and shud continue thru
daybreak. Not expecting a lot of rainfall...probably arnd an 1.5
inches over the SW NC mtns and an inch or so elsewhere. Antecedent
soil conds will be fairly high tho...so isol hydro issues will be
possible across the higher terrain.
Good drying conds are expected behind a weak cold front Mon and
profiles show PWATS dropping below 0.5 inches into early Tue.
Another weak GOM system will generate early Tue and advance toward
the FA while moisture levels increase top down ahead of a warm
front. Precip wont really get going until arnd 18z or so and the
best rates will occur over the srn BR where an additional inch or so
will fall thru 00z. However...rainfall will continue into the ext
range period. Dropped soundings show good cooling ahead of the front
across the nrn NC mtns and some spotty -fzdz/fzra will be possible
arnd daybreak Tue before the sfc layer warms. Some uncertainty is had
the speed of the precip interacting with the cold air...so no sigfnt
ice accums are anticipated. Max temps will be rather warm over the
srn FA Mon with highs in the m60s...and u50s north and mtn valleys.
A cold wedge of hipres builds in Tue which will hold maxes abt 10
degrees below normal.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
As of 2pm EST Saturday: Latest in series of wet systems will be
under way Tuesday night, with no sustained breaks through Friday
morning. Precipitation may lull a bit on Saturday, as next upstream
system is not due in until Sunday. While this last system is past
the usual 7-day forecast range, both the EC and GFS models show
ridging out west on Monday, and the Sunday system passage may end
the wet period. Main issue will be accumulating hydrology impacts.
As sustained rain continues, rivers will be coming increasingly
prone to flooding as the week progresses. Generally 3 to 5 inches
of precipitation is anticipated in the Tuesday through Friday
period, with the heaviest amounts in the mountains.
Best chance, and currently the only real chance, for any thunder,
looks to be Thursday afternoon, when the GFS model develops some
marginal convective instability. Deep layer shear will be quite
good at that time as well, so that time period will be watched for
convective potential.
Surface wet bulb temperatures are currently warm enough for this to
be rain everywhere, except for the higher elevations of the
mountains in Western North Carolina when a brief period of snow,
mixed precipitation, or ice will be possible Wednesday morning.
Given healthy amounts of QPE for the Wednesday morning time period,
there is some chance for that brief period to have impactful snow or
ice in a small area. GFS currently has a small warm noise over the
north-central parts of the CWA Wednesday morning, giving some sleet
potential, but this is still 4 days out and is difficult to be
precise about at this point. Generally speaking, after Wednesday,
low temperatures will be running 5 to 10 degrees above normal, with
highs 5 degrees or so above normal, due to cloud cover and warm,
moist advection pattern.
Surface high pressure east of the Appalachians will likely give some
amount of cold-air-damming on Wednesday, accounting for the lower
temperatures on that day in the forecast, and the chance for winter
weather at a few of the higher elevations. Advance of synoptic
system on Thursday, at least in the GFS model, disrupts CAD on
Thursday, but it comes back on Friday as surface high pressure again
develops in the wake of the Thursday system. The Friday wedge may
hang-in there until Sunday when the next system comes in.
&&
.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
At KCLT and elsewhere: Ceilings are rather variable late this
evening, with MVFR at some times, then scattering MVFR layers and
lower end BKN to OVC VFR layers across the region. As upglide
moisture slowly redevelops, ceilings should fill in at lowering MVFR
levels overnight. As the light rain returns in earnest through
Sunday and into Sunday night, anticipate IFR conditions becoming
more entrenched through the afternoon hours, with LIFR cigs possible
by Sunday evening. Visibility restrictions in the MVFR range will
become more likely, with occasional IFR fog at times with the
heavier precipitation later in the day/evening. Expect mainly ENE
winds east of the mountains through the period, perhaps with some
ESE flow at times late Sunday. More solid SSE to SE flow is expected
at KAVL.
Outlook: A series of low pressure systems will move through
or near the region through much of next week. This will produce
precipitation and associated restrictions for long periods of time
during each wave of precipitation.
Confidence Table...
03-09Z 09-15Z 15-21Z 21-00Z
KCLT Med 75% High 87% High 100% High 80%
KGSP High 100% High 100% High 81% High 82%
KAVL High 81% Med 66% High 81% Med 63%
KHKY High 98% High 98% High 100% Med 71%
KGMU High 98% High 100% Med 75% High 85%
KAND High 91% High 100% High 81% Med 77%
The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables and ensemble forecasts
are available at the following link:
www.weather.gov/gsp/aviation
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...Winter Weather Advisory from 1 AM to 1 PM EST Sunday for
NCZ033-049-050-501-503-505.
SC...None.
&&
$$
SYNOPSIS...DEO
NEAR TERM...HG/PM
SHORT TERM...SBK
LONG TERM...WJM
AVIATION...HG
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
814 PM CST Sat Feb 16 2019
.UPDATE...
814 PM CST
Had updated earlier to expand area of lake-assisted flurries
across far northeast IL this evening based on weak radar returns
and brief reports of -sn at ORD and DPA. Have made a few other
minor tweaks to going forecast this evening, mainly to boost cloud
cover across the entire cwa, and to slow diurnal temp decline
overnight under the clouds. No changes made with developing light
snow late tonight, with recent high-res guidance maintaining
current forecast timing of arrival from after midnight through the
pre-dawn hours.
Patchy weak radar returns (around -5 dBZ) noted in KLOT
reflectivity late this afternoon were producing some light
flurries across portions of the Chicago metro area. These appear
to be "lake assisted", as lake effect snow parameters are not very
impressive with RAP soundings depicting delta-T of only around
10C and equilibrium levels around 4000 ft. This has been
sufficient to produce a few flakes however, and this will likely
continue in spotty fashion through late evening. Better focus will
generally shift north with time however, as evident in greater
concentration of weak radar returns seen in southeast WI here at
mid-evening. Of course, no accumulation is expected with this very
light precip. These light flurries have been occurring within a
larger area of low cloud cover which continues to spread west from
northern OH/IN as well as off the lake, making for cloudy skies
across the forecast area. This has kept temps from falling off too
quickly across the cwa, and have adjusted hourly temps to account
for this slower diurnal dip overnight.
Looking back to our west, regional radar mosaic indicates an area
of moderate snow has developed across parts of the mid-Missouri
Valley. This area of precipitation is associated with short wave
energy and a strong upper level jet streak traversing the southern
periphery of a trough over the central and northern Rockies. This
feature is progged to shear northeastward across our region
through Sunday night, producing a prolonged period of accumulating
light snow. Initial forcing will likely take a little time to
saturate the column, given dry air in the 850-700 mb layer noted
in ILX and DVN 00Z soundings, though persistent forcing and
presence of lower cloud layer should overcome this. High-res
guidance trends remain similar to earlier runs, in depicting light
snow developing across western counties of the forecast area
roughly 2-4 am and 3-6 am in the east. Various guidance suggest
there may be a lull in intensity during the mid-morning hours
before steadier snow redevelops by early afternoon, though
confidence is fairly low in these fine details. Intensity should
decrease early Sunday evening, as the primary mid- level
circulation moves east of the area. Quick look at the arriving 00Z
NAM suggests no significant adjustments needed at this time, with
greatest accumulation potential still across our northwest cwa
counties.
Updated digital and text forecast products available.
Ratzer
&&
.SHORT TERM...
249 PM CST
Through Sunday Night...
Main forecast concerns/challenges are with a period of light snow
likely from late tonight through Sunday.
In the near term, surface ridge is situated across parts of the
upper Midwest and Great Lakes region. In this pattern, easterly
flow being observed, while stratus remains in place across much of
the CWA. Some partial clearing possible across parts of the
southern CWA but as mid/high clouds spread across the region
tonight, cloudy skies will return. Turn focus to expected snowfall
tonight into Sunday, with a period of mainly light snow likely
very late tonight through Sunday afternoon and evening. Large
upper level trough expected to shift east through the CONUS
tonight into Sunday, with a mid level low moving into the northern
Plains. Out ahead of this, energetic mid levels will usher in
several short wave troughs, with WAA increasing out ahead of these
early Sunday morning. These features will assist with saturating
the column, with some drier in place likely delaying the onset of
snow, and then support blossoming snow across the area. Start time
for snow across north central IL is appearing to be right around
3-5 AM, around 4-6 AM for locations in northeast IL, and then soon
there after across northwest IN. Forcing appearing to be the
strongest Sunday morning, as some additional support from some
FGEN swings through. Additionally, forcing will also coincide with
the snow growth zone during this time. However, at this time,
guidance still showing any persistent or strong FGEN will be
lacking for the remainder of the day. Forcing likely weakening in
the afternoon and early evening, but with surface trough and large
upper level trough still in place, will likely support additional
snow development.
Light, to occasionally moderate, snow likely Sunday morning and
then periods of light snow expected through the afternoon and
early evening. Have slightly increased snowfall amounts with 2-4
inches expected across parts of north central and far northern IL.
In this location, some locally higher amounts of 5 inches are
possible, and have issued an Advisory for these locations.
Elsewhere across northeast IL and northwest IN, expect 1-3 inches.
Lake enhancement is possible across far northeast IL in the
afternoon, but conditions still not appearing overly favorable and
don`t anticipate this to add to the totals in this location at
this time. Delta Ts and inversion height do increase Sunday night
and could support some continued light snow development for areas
near the lake behind the system snowfall. It is appearing that
greater focus will stay just to the north in Wisconsin though.
This focus does have the possibility to swing south by very late
Sunday night into early Monday morning, and could provide some
slight increase in intensity. However, confidence is low at this
time. Will need to monitor for the possibility of a period of
freezing drizzle Sunday afternoon into Sunday evening for
locations south of I-80. Some guidance showing the deeper moisture
shifting to the east, while forcing remains in place. Not too
confident at this possibility at this time, but pattern could
support this freezing drizzle and this will need to be monitored
with later forecasts.
Rodriguez
&&
.LONG TERM...
249 PM CST
Sunday night through Saturday...
Persistent troughing in the western CONUS and persistent ridging
in the eastern CONUS will continue to dominate the 500-hPa pattern
through next Friday. The primary concern is a mid-level
disturbance that will likely impact the region overnight Tuesday
into Wednesday morning. The latest GFS guidance suggests 850-hPa
WAA, assisted by anticyclonic flow off the coast of the Carolinas,
will ramp up across the Midwest during this 10-12 hour period.
This will provide the synoptic-scale rising motion necessary for
precipitation. GFS cross-sectional analysis further suggest that
peak negative omega values centered within the DGZ will combine
with adequate moisture from the Gulf of Mexico, providing ample
conditions for snow throughout Chicagoland. Accumulation as a
result of this disturbance could result in several inches of snow
by early afternoon Wednesday, with possible higher totals in the
northwestern CWA. It is important to note, however, that a fair
bit of uncertainty exists with the spatial and temporal onset of
this system. Any slight deviations in its track early next week
could result in vastly different outcomes than those presented
here. We will continue to monitor this development.
DL/Rodriguez
&&
.AVIATION...
For the 00Z TAFs...
531 PM...Primary forecast concern is for a prolonged period of
light snow starting before daybreak Sunday morning...along with
associated cigs/vis.
Weak low pressure will pass well south of the area along the Ohio
Valley Sunday into Sunday night. This system will spread light
snow across the area starting early Sunday morning and continuing
into Sunday night. There may be periods with very light snow or
flurries but its difficult to pin down any possible lulls in the
light snow. Likewise...there may be a few periods of more steady
light/moderate snow. One perhaps mid/late morning and a second
mid/late afternoon. Eventually some briefly lower conditions will
likely be needed. Lake effect snow showers may persist into Monday
morning for ord/mdw/gyy. Prevailing low mvfr cigs are expected
through the duration of the snow but guidance is slowly trending
cigs into ifr by early/mid Sunday afternoon. Thus lower cigs with
later forecasts are also possible. A few flurries are also
possible this evening.
East/northeast winds have been gusty at times into the 15-20kt
range late this afternoon. These should relax later this evening
with speeds 10-15kts into the overnight. The gradient will tighten
a bit by Sunday morning with gusts to 20kts possible for much of
Sunday. Wind directions will turn more northeast Sunday afternoon
and more north/northeast Sunday evening. cms
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Winter Weather Advisory...ILZ003-ILZ004-ILZ008-ILZ010-ILZ011-
ILZ019...midnight Sunday to midnight Monday.
Winter Weather Advisory...ILZ005-ILZ006...3 AM Sunday to 6 AM
Monday.
IN...None.
LM...Small Craft Advisory...LMZ740-LMZ741-LMZ742-LMZ743...midnight
Sunday to 4 AM Monday.
&&
$$
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Area Forecast Discussion
National Weather Service Omaha/Valley NE
809 PM CST Sat Feb 16 2019
.UPDATE...
Issued at 807 PM CST Sat Feb 16 2019
A pronounced vorticity maximum --evident in mosaic radar and
water-vapor imagery-- over south-central NE as of 8 PM will
continue east-northeast through the area tonight. A plume of
modestly steep mid-level lapse rates (around 7 C/km) per 00z
sounding data coupled with intense deep-layer forcing for ascent
will support the continuation of moderate to heavy snow (1"/hr
rates) through midnight.
Latest near-term model guidance is reasonably consistent in
suggesting the axis of highest snowfall over the next 3-6 hours
from Omaha east toward Des Moines, along and immediately north of
vorticity lobe track. The current snowfall forecast is consistent
with this scenario, so we don`t expect to make any substantive
changes at this point. Some snowfall amounts could approach the
high-end of advisory criteria, namely over portions of southwest
IA where 5-7" appears probable.
&&
.SHORT TERM...(Tonight through Tuesday)
Issued at 310 PM CST Sat Feb 16 2019
The main concern is the system that will bring snow to the area
overnight and into Sunday morning. Some light snow is possible
Sunday afternoon and evening, but the main accumulation should be
prior to Noon or even prior to 9 am Sunday. There may be some
mixed precipitation along the KS border.
Primary features noted from the upper air maps at 12Z this morning
included the following. There was about a 9 degree C difference
in temperature at 200 mb from KOAX back westward upstream to KSLC.
At 300 mb, winds of 140-180 knots were in place from southern CA
toward southwest KS. 12 hour height falls at 500 mb were 100-130
meters from northern AZ up into UT and western CO. There was a
modest temperature gradient at 700 mb from SD to KS. Only weak WAA
was noted at 850 mb in the regional area. The highest 850 mb
dewpoints were 8-9 degrees C along the Gulf coast.
Forecast snow amounts were adjusted only slightly based on the
most recent available model guidance. The 12Z NAM was an outlier,
with QPF that seemed too high. We will continue to use mainly a
blend of available model output and national center guidance,
with heavier weight given to some of the recent HRRR and RAP
runs. These suggest the heaviest amounts will be from 6 pm to
midnight, with values mainly from 0.10 to 0.25 liquid equivalent
and snow to liquid ratios of in the 14 or 16 to 1 range. Lift does
linger somewhat past midnight, but will be weaker and thus snow
amounts lower. Expect that QPF values after midnight should be
0.10 or less (water amount) in our area. This will result in Storm
Total Snow amounts in our forecast area (for the whole 24 hour
period from 6 pm today to 6 pm Sunday) being mostly less than 6
inches. The area from Omaha northward and eastward could see some
amounts around or in excess of 6 inches, but that would be over
an extended time. Since it is over a long duration and we do not
expect a lot of wind with this system, we will stay with a Winter
Weather Advisory for now. Adjustments are always possible as new
information comes in, but this was well collaborated with
bordering offices as of 3 pm Saturday.
Lapse rates will be fairly steep, at least the first half of
tonight, and model cross sections show a bit of negative EPV in
the 650 to 350 mb layer, mainly prior to midnight. Mixing
ratios/specific humidity values will be mostly in the 2-3 g/kg
range overnight. A several hour burst of moderate to heavy snow is
likely as the strongest lift moves through the region (700 mb
omega values over 10 microbars per second).
Light snow could linger in the northern and eastern parts of the
forecast area for Sunday afternoon and evening, but at this time,
expect amounts will be light enough to not need a headline. The
period from Monday into Monday night is expected to be cold and
mainly dry. Lows Monday night will be near zero in northeast NE
and zero to 9 above for the rest of the area.
Model suggest increasing lift will cause snow to expand across the
forecast area on Tuesday, with some light accumulations.
.LONG TERM...(Tuesday night through Saturday)
Issued at 310 PM CST Sat Feb 16 2019
Similar to what we saw yesterday, at the start of this period we
should see a split flow at 500 mb, with a mean trough extending
from the Hudson Bay area back toward northern Baja. We will be
mostly under the influence of the southern stream portion of the
split flow.
Several pieces of energy will move out across our area, bringing
continued snow chances from Tuesday night into Wednesday and again
Thursday night through Friday night. Mixed precipitation could
occur by Saturday, as some warmer air starts to work its way into
the region. This will be a system to monitor closely next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 517 PM CST Sat Feb 16 2019
Large-scale forcing for ascent is increasing markedly early this
evening with the arrival of a vigorous vorticity maximum, and
within the left-exit region of a powerful mid-level jet nosing
into the southern Plains. Steepening lapse rates aloft should
contribute to the onset of moderate to briefly heavy snow this
evening at the TAF sites with IFR to LIFR conditions expected. The
strongest forcing for ascent and attendant higher snow rates
should shift east of the area by midnight. However, light snow
will continue into Sunday with MVFR to IFR ceilings and
visibilities.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Winter Weather Advisory until noon CST Sunday for NEZ011-012-
015>018-031>034.
Winter Weather Advisory until 6 AM CST Sunday for NEZ030-042>045-
050>053-065>068-078-088>093.
IA...Winter Weather Advisory until noon CST Sunday for IAZ043-055-056.
Winter Weather Advisory until 6 AM CST Sunday for IAZ069-079-080-
090-091.
&&
$$
UPDATE...Mead
SHORT TERM...Miller
LONG TERM...Miller
AVIATION...Mead
Area Forecast Discussion
National Weather Service Springfield MO
521 PM CST Sat Feb 16 2019
.SHORT TERM...(This evening through Sunday)
Issued at 144 PM CST Sat Feb 16 2019
Surface temperatures were slowly climbing to near freezing across
the area this afternoon however thicker cloudcover is moving in
and will likely halt much more warming. Short term models have
struggled with temperature guidance today and have had to go with
the coldest guidance (generally GLAMP and HREF) going into
tonight. A shortwave currently moving into Kansas along with a
very strong upper level jet will move towards the region tonight,
providing another round of winter weather to the area. 850mb warm
air advection precip was developing in an arc from Kansas into
western Missouri already. Had a few reports of sleet in this
band in southeast Kansas, likely due to some wet bulbing and
convective processes since about 50j/kg of MU cape exists. With
this in mind, decided to go ahead and start the Winter Weather
Advisory early for locations west of a Joplin to Warsaw line. The
rest of the area (with the exception of Newton and McDonald
counties) will start at 6pm.
As we head through the mid to late evening, the low level airmass
will continue to saturate and stronger lift will move in. Cloud
ice will likely be absent for most of the area therefore we are
expecting widespread drizzle, especially after 10pm. This will
likely be freezing drizzle in most locations with surface temps
ranging from 28-32 degrees. Temperatures could be slightly colder
than this depending on exact wetbulb temperature. Southeasterly
winds will begin to develop as a sfc trough takes shape over the
area. This will also favor fog development, especially along the
Ozark Plateau from Springfield and points east. Visibilities may
drop below a mile at times. Will need to monitor the fog
development this evening to see if it needs expanding. RAP model
guidance is much more aggressive with fog.
Freezing drizzle will begin to become more patchy from 12-15Z
Sunday as better lift moves off to the northeast. Total ice
amounts from freezing drizzle will generally range from 0.05 to
0.10in across the area with the highest of these amounts generally
north of interstate 44. Any light sleet or light snow amounts
would remain a dusting at best and reside across central Missouri,
closer to a region of more cloud ice. Plan on slick road
conditions tonight into Sunday morning. Temperatures will not move
much at all on Sunday with most locations staying in the lower to
middle 30s with plenty of cloud cover.
.LONG TERM...(Sunday Night through Saturday)
Issued at 144 PM CST Sat Feb 16 2019
Main concerns will be systems ejecting northeast in southwest flow
aloft. Right now this would be appear to be Tuesday, then again
late in the week as a potentially more substantial system ejects
into the Plains and through our cwfa.
Sunday night/Monday: Canadian sfc high pressure is expected to
nose south into the area with colder than normal temperatures and
dry conditions.
Tuesday: A quasi stationary sfc front is expected to set up from
the TX Gulf coast with a broad area of upglide north of the front
as an upper level impulse moves northeast through the region.
Still some variance in guidance, but in general precipitation is
expected to spread northeast into the area Tuesday. Our area will
be on the edge in terms of vertical thermal profiles between rain-
winter mix-snow once again. However, the ECMWF and GFS aren`t
showing much of a warm nose at this point, so for now will keep
main precip types rain and snow. The northwest cwfa has the best
chance for accumulation remaining in colder air longer. At hits
point, it looks like an advisory type of winter event. We may also
have to watch rainfall amounts for our south central MO counties
for a possible flooding, although higher rain amounts look to be
just south and east of the area. System looks to shift east of the
region Tue night.
Wednesday-Thursday: Look like this period will be relatively quiet
with (somewhat) moderating temperatures. Longwave trough over the
western CONUS with a ridge over the east leaves us in southwest
flow aloft and really can`t rule out some precip during this time,
but there is no clear mechanism for lift with weak sfc high
pressure expected to pass to the north through the Midwest.
Friday-Saturday: There looks to be a pattern change with the
longwave trough over the west opening up and ejecting a system
into the Plains during this time. Right now, it looks to be mostly
rain or maybe rain changing briefly to snow before ending, but
have low confidence in the track and timing of the system.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 518 PM CST Sat Feb 16 2019
Getting some more convective showers of sleet/freezing rain/rain
depending on the temperatures from around BBG-SGF and points
northeast. Trend of lowering ceilings will persist through the
night with IFR most of the night expected. Will need to monitor
the potential of dense fog as the ceilings build down. Expecting
some freezing drizzle behind the showers throughout the night as
well. Winds will eventually come around to the west-northwest by
morning.
&&
.SGF WATCHES/WARNINGS/ADVISORIES...
MO...Winter Weather Advisory until 6 AM CST Sunday for MOZ056>058-
069>071-079>083-090>092-094>098-102>106.
Winter Weather Advisory until 6 AM CST Sunday for MOZ055-066>068-
077-078-088-089.
KS...Winter Weather Advisory until 6 AM CST Sunday for KSZ073-097-101.
&&
$$
SHORT TERM...Burchfield
LONG TERM...DSA
AVIATION...Lindenberg
Area Forecast Discussion
National Weather Service Shreveport LA
954 PM CST Sat Feb 16 2019
.SHORT TERM.../Tonight through Sunday/
The evening sfc analysis indicates a stationary front that
continues to linger near or just S of the I-10 corridor of SE TX/S
LA. However, the RGB satellite imagery depicts overrunning
underway atop the shallow cold dome in place, with sfc temps
responding as readings have slowly begun to warm since sunset.
Areas of FG have redeveloped this evening just W of the CWA over
ECntrl TX, and the short term progs (particularly the HRRR)
suggest the FG bank gradually expanding ESE into portions of E TX
late tonight as a wind shift associated with a cold front begins
to advect the FG SE. Additional FG may develop late tonight over
Deep E TX/Wcntrl LA as the stationary front to our S begins to
slowly work back N as a warm front, which may lift as far N as the
Sam Rayburn and Lower Toledo Bend Country of Deep E TX and into
the Srn sections of Ncntrl LA by daybreak Sunday.
The short term progs including the HRRR suggest that sct areas of
-RA will develop after 06Z along/just ahead of the approaching
front in an area of increasing isentropic ascent, and thus low to
mid chance pops still look good late, mainly over SW AR/N LA.
However, the FG potential is a little less clear, except for the
WSW sections of E TX. Will hold off on a Dense FG Advisory for
this area for now and continue to monitor trends, as only a small
area may be affected late tonight, and this potential being of
brief duration. Did scale back FG mention to patchy over Scntrl
AR/much of N LA, where the sct areas of -RA will likely disrupt
more organized FG formation. Did have to make some adjustments to
min temps tonight, mainly to lower values to near the 03Z obs as
temps are expected to slowly rise overnight given the weak warm
advection underway vis the overrunning. Also scaled down the FG
mention to patchy Sunday morning, as the fropa will quickly mix
the air from W to E. The progs, including the 00Z NAM, suggest
that isolated areas of -RA may linger in for the afternoon over
portions of N LA near and even slightly behind the front, and
thus have added slight chance pops for this area for the
afternoon.
The zone update is already out...grids will be available shortly.
15
&&
.PREV DISCUSSION... /issued 613 PM CST Sat Feb 16 2019/
AVIATION...
Low MVFR will linger across the region this evening, although cigs
should fall to IFR across much of the region by mid to late
evening as overrunning increases. Areas of -RA will continue to
shift E this evening mainly across N LA, but not expecting any
vsby reductions at MLU before diminishing by mid-evening.
Additional areas of -RA may re-develop late tonight across SW
AR/extreme E TX/N LA where overrunning continues ahead of a cold
front, which will enter SW AR/E TX just prior to daybreak Sunday.
In addition, a warm front will advance N into portions of Deep E
TX and Cntrl LA between 07-11Z, which will result in LIFR cigs and
reduced vsbys in BR affecting Lower E TX/Srn and Ern sections of
Ncntrl LA. In fact, areas of dense FG will be possible at LFK and
possibly MLU, but confidence is lower at MLU. Once the front
sweeps SE through the remainder of the area by mid to late
morning, drier air will begin to spill SE in wake of the fropa,
resulting in cig improvements from NW to SE from late morning
through the afternoon. While VFR conditions should return to much
of E TX/SW AR/possibly NW LA by afternoon, MVFR cigs look to
linger through much of the day at MLU before scattering out during
the evening. ESE winds 4-7kts tonight will become NW 8-12kts with
the fropa Sunday morning. /15/
&&
.PRELIMINARY POINT TEMPS/POPS...
SHV 46 62 38 55 / 40 20 10 0
MLU 45 65 38 55 / 40 40 10 0
DEQ 39 54 28 51 / 30 20 10 0
TXK 40 57 32 51 / 30 20 10 0
ELD 40 61 34 52 / 40 30 10 0
TYR 47 57 37 54 / 30 20 10 0
GGG 46 60 37 55 / 30 20 10 0
LFK 51 64 40 61 / 30 20 10 0
&&
.SHV WATCHES/WARNINGS/ADVISORIES...
AR...None.
LA...None.
OK...None.
TX...None.
&&
$$
15