LU9DCE > ALERT 18.02.19 11:15l 260 Lines 14582 Bytes #5 (0) @ WW
BID : 18695_LU9DCE
Subj: Storm Prediction Center 18 02
Sent: 190218/1009Z 18695@LU9DCE.TOR.BA.ARG.SOAM LinBPQ6.0.18
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ESTACION DE PACKET RADIO - BUENOS AIRES (GF05OM)
BOLETINES INFORMATIVOS PROGRAMADOS (BIP)
MD 0107 CONCERNING WINTER MIXED PRECIPITATION FOR NORTHERN
NJ...LOWER HUDSON VALLEY...LONG ISLAND...MUCH OF CT
Mesoscale Discussion 0107 NWS Storm Prediction Center Norman OK
0127 AM CST Mon Feb 18 2019
Areas affected...Northern NJ...Lower Hudson Valley...Long
Island...Much of CT
Concerning...Winter mixed precipitation
Valid 180727Z - 181130Z
SUMMARY...Mixed winter precipitation is expected to continue from
northern NJ across the Lower Hudson Valley and into CT for the next
DISCUSSION...Recent regional radar imagery has shown a modest
increase in precipitation intensity across the region. Observations
continue to show a transition zone from rain to freezing rain to snow
extending from northern NJ across the Lower Hudson Valley and into
eastern CT. Expectation is for light to moderate precipitation to
persist across this region for the next few hours as southwesterly
flow aloft continues to support warm-air advection.
Those areas currently experiencing rain (i.e. Long Island) and
freezing rain (i.e. northern NJ and Lower Hudson Valley) will
likely continue to experience those precipitation types as surface
temperatures remain steady and low to mid-level temperatures increase
slightly. Areas experiencing snow will likely see a transition
towards more mixed precipitation as mid-level temperatures continue
to gradually warm but surface temperatures remain unchanged. Freezing
rain rates around 0.02"-0.05" per hour are possible.
...Please see www.spc.noaa.gov for graphic product...
LAT...LON 41647416 41747379 41827331 41887250 41757201 41597176
41357168 41047203 40677327 40587404 40567444 40587468 40647490
40797508 41057502 41267483 41647416
SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1117
PM CST Sun Feb 17 2019
Valid 181200Z - 191200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY... Isolated thunderstorms are possible over the Great
Basin this afternoon. Scattered thunderstorms are expected to
develop from east Texas into the lower Mississippi Valley tonight.
Another in a series of vorticity maxima rotating through the broad
upper trough will move through the 4 corners region near peak heating
this afternoon. With cold temperatures aloft and steep mid-level
lapse rates in place, heating of the boundary layer will boost MLCAPE
to 200-300 J/kg. This destabilization along with forcing for ascent
accompanying the vorticity maximum should result in an increase in
convection, with scattered showers likely today as well as isolated
thunderstorms by mid-late afternoon, continuing into early evening.
...East Texas through the lower Mississippi Valley...
A large area of surface high pressure will build eastward through
the Great Lakes and OH Valley maintaining offshore flow over the
Gulf. However, a cold front now moving through the western Gulf
will likely stall and then move northward as a warm front late
this period, approaching the LA coast by 12Z Tuesday. A southerly
low-level jet is forecast to strengthen from the western Gulf into
east TX and the lower MS Valley augmenting theta-e advection above
the stable surface layer north of the warm front. This will result
in a corridor of elevated instability overnight with 1000-1500
J/kg MUCAPE. Scattered thunderstorms will likely develop within
this zone of destabilization and isentropic ascent late. Despite
the elevated nature of the convection, effective bulk shear will
be sufficient for a few updrafts to acquire modest rotation, which
combined with moderate instability suggests a few instances of hail
cannot be ruled out. However, mid-level lapse rates below 7 C/km
should mitigate overall threat.
SPC 0700Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1121
PM CST Sun Feb 17 2019
Valid 191200Z - 201200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS TUESDAY
NIGHT IN A CORRIDOR ACROSS SOUTH CENTRAL THROUGH NORTHEAST
LOUISIANA...SOUTHWEST AND WEST CENTRAL MISSISSIPPI AND ADJACENT
PORTIONS OF SOUTHEAST ARKANSAS...
...SUMMARY... Strong thunderstorms may impact parts of the lower
Mississippi Valley Tuesday night, accompanied by at least some risk
for severe weather.
...Discussion... Amplified ridging into troughing across the eastern
Pacific through the western U.S. appears likely to persist within
the mid-latitude westerlies through this period. Downstream,
it appears that flow will remain broadly confluent across much
of eastern North America, to the north of prominent subtropical
ridging centered near/east of the Bahamas.
Within this regime, another vigorous short wave impulse is forecast
to round the crest of the Pacific ridging, before digging near
the British Columbia coast, toward the U.S. Pacific Northwest
Tuesday through Tuesday night. As this occurs, models continue to
indicate that a fairly significant short wave impulse will accelerate
northeastward out of the western U.S. troughing, while short wave
ridging builds downstream, on the northwestern periphery of the
subtropical ridge, through the Ohio Valley and Great Lakes region.
In response to these developments, a gradual erosion of expansive
cold surface ridging, initially encompassing much of the nation east
of the Rockies, is expected to commence across the western Gulf
Coast region, Plains and lower Mississippi Valley. As strongest
mid-level height falls associated with the lead impulse spread
from the international border area, west of El Paso, TX, through
the middle Missouri Valley, a low-level jet is forecast to develop
and strengthen (to 50-70 kt at 850 mb) above the residual cold
surface-based air across parts of eastern Texas through the lower
Mississippi Valley, before shifting northward through Kentucky and
Tennessee by 12Z Wednesday. It appears that accompanying forcing
for ascent and destabilization associated with warm advection and
moistening return flow off the western Gulf of Mexico may contribute
to considerable weak elevated thunderstorm activity.
At the same time, weak surface troughing is forecast to develop
across the lower Mississippi Valley, northeastward toward the
lower Ohio Valley, late Tuesday through Tuesday night. It still
appears that this may become a focus for boundary layer moistening
and destabilization, with surface dew points increasing through
the lower/mid 60s in a corridor across parts of Louisiana and
Mississippi Tuesday night.
Although strongest low-level wind fields will have generally shifted
off to the north, low-level and deep layer shear across the lower
Mississippi Valley probably will remain supportive of organized
thunderstorm development. Given weak boundary layer destabilization,
the environment may become at least marginally conducive to isolated
supercells ahead of, and embedded within, an evolving squall line,
accompanied by the risk for a tornado or two, in addition to a few
potentially damaging wind gusts.
...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind:
5% - Marginal Hail: 5% - Marginal
SPC 0830Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0217
AM CST Mon Feb 18 2019
Valid 201200Z - 211200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS INTO THE DAY
WEDNESDAY ACROSS PARTS OF SOUTHEASTERN LOUISIANA AND MISSISSIPPI
INTO ADJACENT PORTIONS OF SOUTHWESTERN ALABAMA...
...SUMMARY... Strong thunderstorms may continue to impact parts
of the lower Mississippi Valley into the day Wednesday, accompanied
by at least some risk for severe weather.
...Discussion... Models indicate little change to the general
large-scale pattern from Tuesday into Wednesday. A belt of
mid-latitude westerlies likely will remain amplified across the
eastern Pacific into western North America, while flow remains
broadly confluent downstream, across eastern North America, to
the north of prominent subtropical ridging centered to the east of
While another strong short wave impulse continues to dig along the
U.S. Pacific coast, toward the base of the larger-scale western U.S.
troughing, a downstream impulse emerging from the troughing is
forecast to progress around the crest of the larger-scale eastern
U.S. ridging. At the same time, a gradual erosion of cold surface
ridging appears likely to proceed to the east of the Mississippi
Valley, and it appears that a modest cyclone may evolve within
deepening surface troughing accompanying the lead short wave impulse,
across the Upper Midwest and Great Lakes region Wednesday through
Considerable convective development, including embedded
thunderstorms, may be ongoing early Wednesday across the lower
Mississippi and Ohio Valleys, largely driven by warm advection and
moisture return above the residual cold/stable surface-based air.
Forcing for this elevated destabilization and convection is expected
to spread east-northeastward across the Appalachians and northern
Mid Atlantic region through the period, while additional convective
development persists along a trailing quasi-stationary baroclinic
zone across the Tennessee and lower Mississippi Valleys into the
Texas Gulf coast vicinity.
Much of this convection may remain rooted above a cold/stable layer.
However, a corridor of weak to modest boundary-layer instability
developing across parts of the lower Mississippi Valley by 12Z
Wednesday may linger into at least midday, while slowly spreading
eastward. It appears that vertical shear will remain strong enough
across this region to maintain an environment at least marginally
conducive to organized severe thunderstorm development, perhaps
including supercells with the risk for a tornado or two.
Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK
0356 AM CST Mon Feb 18 2019
Valid 211200Z - 261200Z
...DISCUSSION... Models continue to indicate that blocking will
remain prominent within the mid-latitude westerlies across the
northeastern Pacific through this period. Downstream, it appears
that flow may transition to a broadly confluent regime across the
Pacific coast, Rockies, and Plains, and a less amplified regime in
general across the southern tier of the U.S., by late next weekend
into early next week. As this takes place, one more vigorous
short wave impulse is forecast accelerate east-northeastward out
of the Southwest.
There appears increasing consensus, within and among the various
model output, that this feature will provide support for strong
surface cyclogenesis to the lee of the southern Rockies by this
weekend. Guidance generally indicates that the cyclone center will
rapidly migrate from the Texas/Oklahoma Panhandle region into the
Great Lakes on Saturday. This probably will include intensifying
lower/mid tropospheric flow (to 50-70 kt in the 850-500 mb layer)
across an evolving warm sector boundary layer that will become at
least weakly unstable, across lower portions of the southern Plains
through the mid to lower Mississippi Valley region. This environment
may become conducive to the evolution of an organized mesoscale
convective system, and perhaps discrete supercell development ahead
of it, accompanied by the risk for damaging wind gusts and tornadoes.
It remains unclear whether destabilization eastward and
southeastward, toward the Mid Atlantic and Southeast, on Sunday
will remain sufficient to support an appreciable continuing severe
SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK
0122 AM CST Mon Feb 18 2019
Valid 181200Z - 191200Z
...Synopsis... A mid-level trough will deepen across the southwest
CONUS, with surface lee troughing commencing along an axis from the
Four Corners region, down to the west Texas/Mexico border. Return
flow along and immediately ahead of the surface trough will be
quite dry, supporting a modest threat for fire spread given the
dry fuels in place.
...Southern New Mexico into far west Texas... Though temperatures
will be rather mild during the afternoon hours (mainly in the 50s F),
15-20 mph southerly return flow associated with the aforementioned
lee trough will transport very dry air from Chihuahua state in
Mexico, with surface RH as low as 10-20% expected across portions
of southern New Mexico into southwest Texas (west of the Edwards
Plateau). As such, an elevated delineation was maintained across
this area. After sunset, the surface airmass will rapidly cool,
with RH recovery and subsiding winds expected, minimizing the
...Please see www.spc.noaa.gov/fire for graphic product...
SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK
0156 AM CST Mon Feb 18 2019
Valid 191200Z - 201200Z
...Synopsis... A mid-level shortwave trough will eject into the
Central Plains, with a surface low becoming established across
Chihuahua state in Mexico on Day 2/Tuesday. Breezy, dry conditions
north of the surface low will be present along the U.S/Mexico border,
supporting the potential for fire spread.
...Southwest Texas... A localized region of elevated wind/RH
conditions, to the northwest of the aforementioned surface low, is
expected just north of the U.S/Mexico border, mainly along/south
of the Santiago and Chisos Mountains. Here, 15-20 mph winds,
with 10-15% RH and 60F temperatures are expected during the late
afternoon. Locally higher downslope winds may be briefly be observed
along the lee of the Santiago or Chisos Mountains. As such, locally
critical conditions cannot be ruled out. By evening, rapidly cooling
temperatures will temper the threat for fire spread.
...Please see www.spc.noaa.gov/fire for graphic product...
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