Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/19/19
Area Forecast Discussion
National Weather Service State College PA
1043 PM EST Mon Feb 18 2019
.SYNOPSIS...
A large area of high pressure will become centered over the
state Tuesday. A new storm system will move into the region
Wednesday with high pressure building back in for Thursday and
Friday.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
The back edge of the strato-cu and flurries is moving slowly east
into my western zones, and will bring about continued slow but
steady improvement overnight.
Northwest winds will continue to gust 15-20 mph before slowly
diminishing overnight.
Lows will drop into the very chilly single digits over the far
north, and range to around 20 over the lower Susq Valley.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
Much of the area will be clear by Tuesday morning, though RAP
soundings indicate that some patchy thin and low stratocu are
possible across the Northern Mtns of PA.
The Center of a sprawling area of high pressure covering the
NErn half of the CONUS will be centered over New York and PA.
However, low pressure will gather over the lower MS Valley Late
Tuesday and Tuesday night with a strong southerly flow of WAA
and Gulf Moisture out ahead of it, leading to a rapidly
blossoming area of Precip across Tennessee and Lower/Mid Ohio
River Valleys.
The leading edge of this precipitation shield (in the form of
snow) will move quickly up the OH River Valley and should start
in the Laurels up to a few hours before sunrise Wednesday, and
spread north and east to the Central Mtns and Susq Valley
between 11-14Z.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Looking at Wednesday into Thursday there is a little more certainty
in the timing of the event. The system should initially start as snow
but transition to FZRA/sleet in the afternoon. All models are
trending colder with GEFS having less probability of rain. Given
the increase in confidence a watch was issued with the heaviest
amounts of snow through the far southwest. Iced accumulation
should be an issue in the afternoon from from the warm air aloft
and cold sfc temps.
For most of the period from Thursday into at least early Saturday,
not a lot going on. I did cut back on POPS and weather where I
could. Temperatures borderline, so used a mix of rain and snow.
Main question is if a deep low will form and lift across the lower
Great Lakes on Sunday. Latest EC and GFS are trending towards
each other though EC is trending further north.
&&
.AVIATION /04Z TUESDAY THROUGH SATURDAY/...
Late evening satellite loop shows stratocu breaking up across
central Pa, with MVFR cigs still noted over the higher terrain
of the Appalachians at 0230Z and VFR conditions further east.
High pressure will build into the region tonight, causing winds
to diminish and remaining stratocu to break up. Linear extrapolation
of upstream clearing in satellite imagery suggests lingering mvfr
cigs over the central mountains will break up between 04Z-06Z.
The arrival of high pressure will bring a near certainty of VFR
conditions and light winds over the entire region Tuesday.
Outlook...
Wed...Snow to a wintry mix.
Thu...AM light freezing rain/low cigs possible.
Fri...AM low cigs possible W Mtns.
Sat...PM rain/low cigs possible.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
Winter Storm Watch from Wednesday morning through Thursday
morning for PAZ058.
Winter Storm Watch from late Tuesday night through late
Wednesday night for PAZ024>026-033>036.
Winter Storm Watch from Wednesday morning through Thursday
morning for PAZ027-028-056-057-059-063>066.
&&
$$
SYNOPSIS...La Corte
NEAR TERM...La Corte
SHORT TERM...Lambert
LONG TERM...Dangelo/Ceru
AVIATION...Fitzgerald
Area Forecast Discussion
National Weather Service Huntsville AL
911 PM CST Mon Feb 18 2019
.NEAR TERM...(Tonight)
Issued at 911 PM CST Mon Feb 18 2019
Canadian high pressure sprawled over the northern plains was the main
feature controlling the weather situation over much of the eastern
lower-48. The high was bringing colder air southward across the Deep
South, with early evening temperatures ranging in the mid 30s to low
40s with NNE winds of 5-10 mph, with a few higher gusts at times.
To our south, a lower level Gulf moisture return and isentropic
upglide had resulted in rain showers extending from north of Beaumont
TX to Meridian MS and south of Birmingham and Atlanta. These showers
were moving to the east while sliding northward. Unfortunately, the
models were not detecting nor handling this area of light showers
very well. The NAM/Canadian/ECMWF start showing it towards daybreak
tomorrow. Afterward, the GFS joins in as more widespread showers are
in order for Tuesday.
A concern for the overnight are how cold will low temperatures go.
The on-going forecast overall from the day shift have lows into the
lower 30s north of the Tennessee River. Thus a worry of a brief
wintry mix south of there cannot be totally ruled out, as the
precip meteors aloft cool as it falls in the dry layer between >12kft
to the surface. The RAP soundings suggest the moisture layer by the
time it reaches this area will be too thin to produce precip that
will survive the trip to the surface. The soundings also suggest, and
supported by the satellite view that mid/upper altitude clouds aloft
should be dense enough to reflect longwave radiation back to the
surface, making for somewhat warmer night time. Temperatures should
start warming before daybreak and the onset of showers, that should
help lessen wintry mix issues. Only minor changes will be made to
the grids for the overnight, not enough to change the wording much.
.SHORT TERM...(Tuesday through Thursday)
Issued at 316 PM CST Mon Feb 18 2019
Models have continued the trend of shifting the heavier rain band to
our W/NW on Tuesday. This is in response to a deeper trough across
the western US, slightly stronger ridge to our SW, and a CAD event in
the Lee of the Appalachians. These factors will take make of the
forcing and focus for heavier rains on Tuesday along and west of the
MS River. This more westward shift in latest guidance has lowered
rainfall totals from past forecasts. However, any shift in where this
axis sets up will have a big impact on rainfall totals.
As the trough moves out of the desert SW and into the Plains Tuesday
into Wednesday it begins to shift the heavier precip axis associated
with the cold front eastward. Moisture transport ahead of this boundary
will be very high with PWAT values approaching records for February.
Couple the influx in near record moisture with a strong 850mb jet,
the right entrance region of the 250mb jet over the area, and strong
isentropic ascent and you get strong vertical motions situated along
the cold front. Since the front will be delayed until after sunrise
Wednesday it is looking increasingly possible that we`ll have enough
time for CAD to weaken and winds to become more southerly. This will
advect better low level moisture into the area and with steep lapse
rates aloft, which would support thunderstorms to be embedded in the
axis of heavy rainfall. MUCAPE from the GFS could range from 200-500
J/kg and when combined with a veering wind profile, there is a risk
for some stronger thunderstorms Wednesday afternoon.
The biggest concern is that if the frontal boundary stalls out over
the TN Valley for a longer period on Wednesday, any thunderstorms
that develop could really enhance rainfall totals. Rain rates could
be upwards of an inch or two per hour, which could start to overwhelm
drainage basins. The current forecast for the 6am to 6 pm Wed period
calls for between 0.5 to 1 inch. So, if thunderstorms do form and
there is training of these storms these totals could be very
underdone.
After coordinating with TVA, there is large amount of water in their
upstream reservoirs and they are forced to release much of that
water downstream. In doing so it would raise river levels into Minor
flood stage by Wednesday. And that is just a result of water being
released downstream, not truly taking into account the added rainfall
from this event. So we could be looking at a situation where water
along many of our drainage basins won`t have a place to drain to and
water just begins to backup. Based on this weekends event and the
responses we saw in river/stream levels, soils are likely completely
saturated and can`t hold any additional rainfall. So, if the heavier
rain axis sits over the area for any length of time on Wednesday, all
of the rain will be runoff and could result in some significant
issues. As the previous forecast stated, the amount of rain on
Wednesday will be heavily dependent on the duration the band sits
over the area.
By Wednesday night into Thursday morning, high pressure moving into
the OH Valley will push the cold front to our south. This should give
much of the area a brief reprieve from the moderate to heavy rain.
Some models suggest we could see some lingering light rain Thursday
due some weaker shortwaves moving through the upper level
southwesterly flow. Starting Thursday afternoon into the evening
hours the frontal boundary to our south will begin to lift back
northward as a warm front. We should begin to see a return of the
moderate to heavy rainfall overnight as this boundary crosses back
over the area.
.LONG TERM...(Thursday night through Sunday)
Issued at 316 PM CST Mon Feb 18 2019
Extended range guidance from a consensus of the global scale
deterministic and ensemble models suggests that a subtropical ridge
(initially centered east of the Bahamas) will retrograde and weaken
by Sunday, while a broad positively-sheared longwave trough remains
intact across western North America. The net result will be a
continuation of seasonably strong/deep southwest flow across the TN
Valley for the majority of the forecast period. Within this regime, a
mid-level vort max located off the Pacific coast of Mexico is
predicted to eject rapidly northeastward in the southern branch of
the jet, but should shear apart in increasingly confluent flow aloft
before reaching the mid-MS Valley around 12Z Saturday. Regardless of
the weakening nature of this disturbance, an axis of surface pressure
falls related to its movement will slowly become established to the
north/west of the TN Valley late this week, allowing an effective
warm front to surge northward through the region on Friday afternoon.
Widespread light rain is anticipated to redevelop in the cool sector
to the immediate north of the retreating warm front late Thursday
night and continue through Friday morning, with a low probability for
thunderstorms expected to expand northward throughout the day as the
increasingly unstable warm sector builds northward.
Scattered-numerous showers and a few thunderstorms will continue
across the region from late Friday night and throughout the day on
Saturday, although with a general lack of synoptic scale forcing for
ascent over the warm sector we have indicated a gradient in POPs with
highest values over the northern/western zones. Meanwhile, a
stronger mid-level shortwave trough embedded in the broader western
CONUS longwave is expected to lift rapidly northeastward from the
southern Rockies into the eastern Great Lakes on Saturday-Sunday.
Low-level southerly flow will increase considerably on Saturday in
response to the movement of the stronger shortwave, with highs
forecast to reach the l-m 70s assuming a decreasing trend in
precipitation and at least some breaks in cloud cover. As the
deepening surface low related to this disturbance lifts northeastward
across the central Plains and into the mid-MS Valley on Saturday
afternoon/night, the trailing cold front will begin to accelerate
eastward, initiating a linear convective feature across western
portions of the lower MS Valley on Saturday afternoon which will
impact our region late Saturday night/early Sunday morning. Both
deep-layer and low-level shear will be more than adequate to support
storm organization, and with dewpoints in the l-m 60s supporting
MLCAPE potentially as high as 500-1000 J/kg, we are certainly
concerned about the potential for a severe thunderstorm event.
Canadian surface high pressure will build southward into the region
in the wake of the cold front, with cooler and drier conditions
anticipated on Sunday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 550 PM CST Mon Feb 18 2019
Cold high pressure situated over the Northern Plains will build
eastward, resulting in NE winds ~10kt becoming easterly overnight and
on Tue. A more ESE component above the surface will bring additional
moisture preceding a developing area of low pressure over the NW Gulf.
This system moving NE will bring lower clouds and begin rain chances
across the TN Valley, from south to north during the Tue. Easterly
winds should increase into the 10-20kt range later Tue afternoon, as
a pressure gradient around the developing low strengthens. MVFR
CIG/VIS reductions are possible early Tue afternoon, with IFR
conditions developing late in the TAF.
&&
.HUN WATCHES/WARNINGS/ADVISORIES...
AL...Flood Watch from 6 AM CST Tuesday through late Thursday night for
ALZ001>010-016.
TN...Flood Watch from 6 AM CST Tuesday through late Thursday night for
TNZ076-096-097.
&&
$$
NEAR TERM...RSB
SHORT TERM...Stumpf
LONG TERM...70/DD
AVIATION...RSB
For more information please visit our website
at weather.gov/huntsville.
Area Forecast Discussion
National Weather Service Omaha/Valley NE
526 PM CST Mon Feb 18 2019
.SHORT TERM...(Tonight through Thursday)
Issued at 325 PM CST Mon Feb 18 2019
The main forecast concern is the potential for significant snow
starting late Tuesday afternoon and continuing into Wednesday
morning. Several things appear to be coming together for an
event that could bring 5 to 8 inches of snow to most of the
area. More on that in a bit.
Much of the area saw a decent amount of sunshine today, with
clouds holding a bit more in some of our southern counties. Mid
afternoon satellite imagery showed clouds spreading northeast.
Clouds tonight should be variable and temperatures will be cold
again. Look for lows near zero in the northern and eastern parts
of the forecast area, with single digits elsewhere.
Isentropic upglide will bring thickening clouds to the area
for Tuesday, and saturation should occur in our southern and
possibly western counties before 6 pm. After looking at available
model output and coordination with bordering offices, thought a
winter storm watch for all of the area was a good idea. We are
currently looking for amounts ranging from 4 to 8 inches. There is
still quite a bit of model variability on the axis of heaviest
precipitation. Hopefully there will be better model agreement the
next few runs.
A general blend of model output suggests the 500 mb height fall
center (HFC) should track from the TX panhandle at 6 pm Tuesday
to northeast KS or southeast NE by 6 am Wednesday, then to central
IA or the IA/MN border area by Noon Wednesday (depending on what
model you look at). It appears that there will be somewhat of a
coupled jet structure at 300 mb. It appears we may be affected by
the left exit region of a jet max to our south and the right
entrance region of a jet max to our east. The 12Z GFS suggests
about a 12 degree C temperature difference from our area
southwestward back into the trough - valid at around 21z Tuesday.
750-700 mb mixing ratios/specific humidity values are expected to
be mostly in the 2 to 3 g/kg range, but the snow accumulation
period is a bit over 12 hours. Mid level lapse rates do not appear
to be as strong as the last system, but 12Z GFS cross sections
show a bit of negative EPV near the top of the dendritic growth
zone above 600 mb. The strongest omega values are forecast through
most of the dendritic layer. Some of the extended RAP grids are
showing pockets of negative EPV as low as about 750 mb Tuesday
evening. Snow to liquid ratios for the event are expected to be
between 14 to 1 and 19 to 1, a little higher than normal.
Snow chances will decrease from southwest to northeast through the
day Wednesday, with currently little or no accumulation forecast
for the afternoon hours. Mainly dry weather should then continue
for Wednesday night and Thursday.
.LONG TERM...(Thursday night through Monday)
Issued at 330 PM CST Mon Feb 18 2019
Large scale pattern at 500 mb for the start of this period is
expected to feature a closed low back toward NV or southern CA,
part of a broad trough from central Canada back off the coast of
Baja. A fairly strong piece of energy is expected to lift out
across the central US for Saturday into Saturday night, bringing a
chance of snow for most of the area. A mix will be possible near
the KS and MO borders. The GFS/ECMWF and Canadian model all
suggest the low becoming closed off at 500 mb at least briefly,
and a strong deformation zone moving across the forecast area.
Track of the surface low moving from southwest to northeast over
Kansas City is a favored storm track for snow in Omaha. Stay
tuned.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 517 PM CST Mon Feb 18 2019
Light winds and VFR conditions expected tonight with some higher
clouds. Lower ceilings will be moving in Tuesday morning ahead of
the approaching storm system. MVFR ceilings expected after 12z
with ceilings continuing to decrease through the afternoon. Snow
will move in to the area from east to west through the early
afternoon. IFR conditions may move in as the snow increases
through the evening but left out of TAF for now as it is late
in the TAF period.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Winter Storm Watch from Tuesday evening through Wednesday
morning for NEZ011-012-015>018-030>034-042>045-050>053.
Winter Storm Watch from Tuesday afternoon through Wednesday
morning for NEZ065>068-078-088>093.
IA...Winter Storm Watch from Tuesday evening through Wednesday
morning for IAZ043-055-056-069-079-080-090-091.
&&
$$
SHORT TERM...Miller
LONG TERM...Miller
AVIATION...HB
Area Forecast Discussion
National Weather Service Pueblo CO
759 PM MST Mon Feb 18 2019
.UPDATE...
Issued at 746 PM MST Mon Feb 18 2019
Light snow is spreading in again with KPUX radar showing echoes
blossoming across the northern Sangre De Cristo mountains. Also
seeing an area of light snow expanding across portions of
Pueblo, El Paso, and Crowley counties. Still appears a broad band
of isentropic lift will set up across northern portions of the
southeast plains extending back to Fremont county...across the
northern Sangres and northern San Luis Valley tonight through
Tuesday morning. Another 1 to 3 inches will be possible north of
highway 50...though with the dry nature to the snow...this may
decrease impacts some. Farther south...high res model runs and
00z NAM still suggesting only light additional accumulations...and
have downgraded the winter storm warning to an advisory. Another
1 to 2 inches will be possible for that area. Area to watch for
the heaviest snow tonight will be across the Eastern San Juans
where upslope will enhance snowfall totals...and across the San
Luis valley...the Sangre De Cristos (mainly the northern
range) and parts of Fremont county where the next band sets up.
Current highlights look on track for now. -KT
&&
.SHORT TERM...(This evening through Tuesday)
Issued at 350 PM MST Mon Feb 18 2019
Currently...
Light snow showers were noted over the plains per radar and sfc
obs. Precip was very light. Finely banded structures were noted on
radar across El Paso and N Pueblo counties extending back into
crowley county. Convection was very low topped so radar was only
observing echoes relatively close to the radar. It was cold across
the region at 2 pm with readings in the teens across al of the
plains. 20s were noted in the San Luis Valley (SLV) while temps
were very cold at mtn top; below zero readings.
Rest of today through tonight...
2nd short wave will come across the region during the early morning
hours. 700 mb circulation associated with this wave was over
southeastern UT and was moving east-northeast. This wave will
enhance the snowfall over a good part of the region, especially the
SW mtns, the Northern SLV, the northern Sangres, Fremont county and
across N Pueblo and a good part of Teller and EL Paso counties.
Snowfall over the lower elevations will likely range between 1-2"
with local 3" amounts, while over the mtns a foot or more of new
snow will be likely. N SLV will see 2-4" and 3-6" in Fremont county.
Per numerous runs of the HRRR and other guidance products, it
appears the best chance of snow over El Paso and Pueblo counties
will be from 06 UTC to 12 UTC.
A good part of the plains, especially ares generally from Rye to
Lamar may see little additional accumulations. The S SLV will also
see the least amount of snow in the valley.
Temps tonight will be in the single digits to low +10s across the
plains and SLV, with temps below zero in the mtns. If it were clear
tonight, it would have been much colder.
Tuesday...
Snow will be exiting the plains by mid morning tomorrow with only
snow showers expected as another weak wave moves over the area
during the afternoon. Snow will continue over the mtns, but snowfall
rates will decrease (although may be locally enhanced in some areas
during the afternoon as the weak wave moves across). Note that I
changed the highlights so that they will end around noontime over
the lower elevations. They originally were in effect until late
afternoon. Temps tomorrow will be a bit warmer than today, but will
still be cold with readings in the 20s in the valleys and plains and
single digits mtns. /Hodanish
.LONG TERM...(Tuesday night through Monday)
Issued at 350 PM MST Mon Feb 18 2019
Overall, a continued theme of unsettled meteorological conditions
at times in combination with below seasonal latter February
temperatures are anticipated during the longer term.
Initially, the next in a series of upper level disturbances will
be capable of producing another round of accumulating snow over
southern Colorado Tuesday night with an additional one to three
inches of snow projected over higher terrain/mountain locations
and generally an inch or less of snow over lower elevations
during this time-frame.
In addition, well below seasonal temperatures are expected
Tuesday night with minimum temperatures dropping into the positive
single digits over many Interstate 25 corridor locations, while
the San Luis Valley and mountain locations should basically
experience minimum temperatures in the negative single digits.
A brief respite in the active meteorological conditions should be
noted over the majority of the CWA from Wednesday into Wednesday
evening as CWA should be between storm systems.
Meteorological focus the shifts to Continental Divide
locations(initially favoring the eastern San Juan mountains from
Wednesday into Thursday and then the central mountains on Friday)
from later Wednesday evening into Friday as next system impacts
this region with additional accumulating snow during this-frame.
Next longer-term concern then runs from later Friday night into
Saturday as closed upper low has the potential to develop over the
Texas Panhandle region, which would be capable of generating
accumulating snow and gusty winds over eastern locations during
this time-frame. As always, WFO Pueblo will closely monitor all
potential incoming storm systems closely.
Then, a return to more tranquil conditions(outside of Continental
Divide locations...where additional light accumulating snow will
be possible at times) are anticipated over many southern locations
from Sunday into next Monday as zonal to southwesterly upper flow
impacts the region.
Finally, as touched upon briefly earlier, generally below
seasonal temperatures are projected during the balance of the
longer term with coldest temperatures expected Wednesday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 350 PM MST Mon Feb 18 2019
It will remain quite cold with light snow likely at the taf
sites tonight with IFR conditions likely. Snow should end after
sunrise tomorrow with gradually clearing skies. Winds will be
light.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 11 AM MST Tuesday for COZ064-065-
069>071-076>078-081>089-095-096.
Winter Storm Warning until 5 PM MST Tuesday for COZ068-072>075-
079-080.
Winter Weather Advisory until 5 PM MST Tuesday for COZ058-060-
061-063-066-067.
&&
$$
UPDATE...KT