Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/09/21
Area Forecast Discussion
National Weather Service Columbia SC
838 PM EDT Thu Apr 8 2021
Dry high pressure will move further offshore overnight with an
approaching frontal system bringing increasing chances of
showers and thunderstorms Friday into the weekend. The front
will move through Sunday and expect dry conditions late Sunday
through Tuesday as high pressure builds into the area.
Temperatures will remain mainly above normal through early next
.NEAR TERM /THROUGH FRIDAY/...
Moisture continues advecting into the area as the upper ridge
slides offshore of the Carolina Coast. Strong short wave moving
through the OH Valley continues generating thunderstorms while
weak short waves move just northwest of the forecast area. Area
radar returns indicate a few light showers over the northwestern
portions of the area and the Pee Dee...expect much of the
returns are virga with a few trace amounts reaching the surface.
With plenty of high clouds overnight and a 20-25 knot low level
jet keeping the boundary layer mixed expect lows in the lower
.SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/...
Friday and Friday night...the Ensembles and GFS/ECMWF suggest an
increase in low level moisture by the afternoon with dew points
into the low 60s. Resulting instability appears moderate
with greater than 50 percent chance of cape > 1000 in the CSRA
from ensemble guidance. low to mid level lapse rates near
7C/km. Bulk shear is not that impressive and the latest spc
outlook for severe has shifted to the west of east central GA.
The Nam model appears to have a stronger low to mid level cap
and air mass remains rather dry...but think moisture advection
will be a little stronger in southwest flow. Possible weak mid
level short wave trough moving through late in the day may
provide some lift. CAM models suggest bulk of convection may set
up in south central GA to the coast...mainly south of the area.
Favor chance pops mainly in the CSRA and west Midlands with
lower pops to the east due to surface ridging from offshore.
Scattered convection should diminish overnight with lack of
strong forcing. Slightly cooler in the CSRA where more
cloudiness expected...upper 70s to low 80s. Min temps around 60.
Saturday and Saturday night...Stronger large scale lift across
the area during the period with increased divergence over the
area as another deep upper low moves northeast from the Mid
Mississippi Valley. Strongest lift mainly in the late afternoon
and evening associated with short wave trough. Question of
degree of instability. Moderate deep layer shear. Some guidance
such as nam 3km shows a line of convection moving through the
area although weakening as it moves east. This convection will
be well ahead of the front back in Tennessee and Alabama. But
the GFS and ECMWF ensemble guidance is suggesting weak
instability. Given stronger lift and deeper moisture, continue
likely pops for showers and scattered to widely scattered
thunderstorms. Max temps in the upper 70s to low 80s.
Persistence with min temps around 60.
.LONG TERM /SUNDAY THROUGH THURSDAY/...
A cold front pushes through The Midlands and CSRA during Sunday.
The best instability should be in the eastern Midlands due to
the frontal timing and peak heating. Expect a chance of showers
and thunderstorms. It is still too early to assess the severe
Model ensembles place the Southeast U.S. in a nearly zonal flow
aloft early next week with a flat ridge axis over the Lower
Mississippi River Valley. Low level Gulf of Mexico moisture
slowly advects into The Midlands and CSRA during the middle of
next week for an increasing chance of showers and
thunderstorms. Temperatures are expected to remain above normal.
.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
Starting off VFR at all terminals with a threat of MVFR/IFR
restrictions at AGS/DNL Friday morning. Convection developing
around all terminals Friday afternoon as a cold front
High pressure continues to shift further offshore opening the
region to S-SW moist flow. A significant upper level trough is
passing through that resulting in a few surprise sprinkles at
CUB/CAE. Winds light predominately out of the S-SW tonight, with
a weak band of higher winds above the inversion out of the
SW...with the potential of bringing in moisture mixing at the
top of the inversion after 09-10Z. Ensemble models, along with
HRRR and LAMP forecast guidance suggest some stratus or strato-
cu may develop late tonight and tomorrow morning resulting in
ceiling restrictions at AGS/DNL, along with some fog. This may
be overdone but this is a favorable pattern for at least MVFR,
and confidence is high enough to include in the TAFS.
EXTENDED AVIATION OUTLOOK...Expecting scattered convection and
associated restrictions Friday afternoon at all terminals.
Instability is limited, so the severe threat appears to be
limited but threat for thunder is present. Periodic ceiling and
visibility restrictions will continue through Saturday and into
early Sunday afternoon until a dry airmass and cold front
finally push through Sunday afternoon.
Area Forecast Discussion
National Weather Service Pueblo CO
820 PM MDT Thu Apr 8 2021
Issued at 803 PM MDT Thu Apr 8 2021
Let Red Flag Warning for this evening expire, as winds across the
area were slowly decreasing. Quick look at latest HRRR supports
Red Flag conditions again over the San Luis Valley and
Fremont/Pueblo Counties on Friday, and will upgrade current fire
weather watch to a warning for these areas. Eastern plains will
certainly be windy enough for critical conditions, but with RH
rising slowly behind the cold front, we may not see the required 3
hrs of sub-15 percent RH for a highlight, and will push decision
off to the next shift.
.SHORT TERM...(This evening through Friday)
Issued at 227 PM MDT Thu Apr 8 2021
Latest upper air analysis shows a long wave trough over the western
half of the CONUS. Within the long wave trough were two short wave
troughs, one over the Northwest CONUS and the other over the Central
Plains. Northwest winds were breezy over the Plains behind the
second trough. This has led to Red Flag conditions being observed
in the Plains.
For the rest of the afternoon the breezy northwest winds will
progress southeast across the Plains. These winds will peak mid
afternoon then start to decline late this afternoon.
Tonight the winds will decline. Lows will range from the teens to
30 degrees in the mountains, with mid 30s to low 40s in the Plains.
Friday a cold front will move through the forecast area during the
morning. Behind the front northerly winds will increase, reaching a
peak by early afternoon. Gusts of 40-50 MPH are expected in the
Plains. As was mentioned previously, wouldn`t be surprised if a
there are isolated gusts of 60 MPH during the afternoon over the
eastern Plains. However confidence is low this will occur given the
winds near 60 MPH are confined to the top of the mixed layer, or
well above it for most locations. Therefore am thinking this will
be a windy day but should remain below high wind criteria.
Despite the cooler temperatures behind the front, there is a fire
weather concern for zones 224, 222, and 228. The current watch has
been expanded to include zone 228 Pueblo County. Highs will range
from around 30 in the mountain peaks to the 50s in the Plains. Due
to a dry environment in place, am not expecting much cloud cover
despite the frontal passage.
Friday night northerly winds will become light by mid evening. Lows
will fall teens and 20s across the forecast area.
.LONG TERM...(Saturday through Thursday)
Issued at 227 PM MDT Thu Apr 8 2021
For this part of the forecast the upper level weather pattern will
not change much from what we have had. An upper level short wave
ridge on Saturday will transition to a trough as the first of two
upper level short wave troughs move through the flow over the
forecast area during this timeframe. Despite the rather active
weather pattern, models are in remarkable agreement with the timing
and track of these two upper level short wave troughs.
The path of the first trough looks to be too far north to bring much
of a chance for precipitation to the forecast area. Accompanying
the first trough will be a cold front. This air mass will linger
over the forecast area through the rest of next week.
The path of the second trough that moves in early next week looks
to be better positioned to bring precipitation to the forecast
area. Current model guidance shows this second trough retrograding
somewhat during the latter half of the week. This is what causes
the chances for precipitation to last from Tuesday through the end
of the week.
Saturday critical fire weather conditions may occur for the
western half of the forecast area. The relative humidity will be
low enough, the question is whether the winds will be strong
Sunday afternoon the threat for critical fire weather conditions
expand to most of the forecast area. As with Saturday, the
relative humidity values will be low enough, however the limiting
factor will be the strength of the winds.
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 520 PM MDT Thu Apr 8 2021
At KALS, VFR conditions are expected for the next 24 hours. Winds
and the high cloud cover both are expected to diminish this
evening by around 04z. Northwest winds then pick up again around
midday, gusting to around 25 kts.
At KPUB and KCOS, VFR conditions are expected for the next 24
hours. Winds continue to decrease to around 10 kts tonight. The
high clouds are also anticipated to decrease through the evening.
A frontal passage in the early morning brings strong northerly
winds to both terminals around 11 or 12z, peaking from mid
morning through the afternoon before gradually decreasing in the
Red Flag Warning from noon to 8 PM MDT Friday for COZ222-224-228.
Area Forecast Discussion
National Weather Service Blacksburg VA
832 PM EDT Thu Apr 8 2021
A complex low pressure system will keep a front over the region
through Friday. Another low continues the chance of showers
through Sunday. Dry weather is expected behind this system for
Monday and Tuesday.
.NEAR TERM /THROUGH FRIDAY/...
As of 820 PM EDT Thursday...
Thunderstorms have manage to take advantage of the instability
provided by today`s heating ahead of the shortwave slipping
across the region: surface CAPE of the evening sounding was
~1000 j/kg, so no shock that we are getting some thunder and
lightning: that instability combined by the weak shear has
allowed for some isolated cells to produce some hail.
Will continue to monitor the showers and storms as they slip
across the area: generally expecting things to continue to
remain mostly quiet, though the HRRR is wanting to slightly
organize the line as it skips northeast past Lynchburg as it
slips into Sterling`s coverage area.
Following the rain, wedge conditions start to build into the
region, coating the area in areas of fog and low clouds
generally in the foothills and Piedmont, into the Southern
Shenadoah and New River Valley.
As of 150 PM EDT Thursday...
As we head through the afternoon, a shortwave/vort tracks into
the mountains, with upper divergence increasing to the
northeast. High- res models still highlight best shower chances
in a corridor from the Alleghanys of Virginia, southeast into
the piedmont of VA. MLCAPEs of 400-700 J/Kg may be enough to
allow for some thunderstorms. Otherwise, rest of the CWA will
see isolated to scattered showers this afternoon, with lowest
threat across the NC piedmont into the foothills
Tonight, will see shallow wedge hold firm across the piedmont while
rest of the area will stay on the warm side of the front. Tail end
of vort will keep threat of showers high this evening along/north of
a BKW-LYH line, then should see some drying at least south of this
line overnight, which in agreement of the Euro/NAM solution. Could
see some drizzle/fog across the foothills/piedmont of VA outside the
showers, but the wedge overall does not look that strong. Lows in
the 50s most areas tonight.
Friday will see another scattering of showers/storms as another
shortwave pivots across the area, with best chance along/east of the
Blue Ridge. Temperatures overall are dependent on wedge/cloud cover
and showers, but leaned toward cooler MET. Still warm with mid to
upper 60s from Lewisburg-Roanoke-Lynchburg north, to lower to mid
Forecast confidence high.
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
As of 225 PM EDT Thursday...
Showery and isolated thunderstorms while warm weather continues...
Backdoor front will have partially eroded the wedge by Friday night.
Overnight showers will be less numerous before a cold front
approaches Saturday night, and because of the lack of insolation to
help instability, don`t expect any thunder after sundown. Showers
and storms pick up again Saturday afternoon. With the wedge eroded
and the best forcing of the weekend from the front, have isolated
thunder in the forecast for most of the area through Saturday
afternoon and evening. Rain persists through the night into early
Sunday morning, expecting this to be the period of heaviest rain. Up
to three-quarters of an inch in our northernmost counties around
On Sunday after the front has passed, may have some lingering precip
before the closed low moves far enough north, which should be late
Sunday. Skies will also start to clear after an overcast weekend.
Despite the cloudiness, temperatures over the weekend will be still
be above normal for the time of year. Daily highs across the
forecast area will be in the high 60s or 70s this weekend.
.LONG TERM /MONDAY THROUGH THURSDAY/...
As of 200 PM EDT Thursday...
Generally dry early, then an increasing chance for showers along
with a cooling trend later next week.
Ensemble guidance is consistent with indicating shallow ridging
aloft with a flat closed low spinning over the Great Lakes gradually
gaining some amplitude toward the latter portion of next week.
While this pattern will not favor any significant weather for the
Appalachians and central mid Atlantic region, it may not be
completely dry as some weak short waves cross the region especially
as the upper low starts to amplify later in the week. Cooler air
will steadily filter in from the northwest though since we will be
starting off the week above normal expect the cooldown will only
bring us closer to seasonal normals for mid April.
.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
As of 830 PM EDT Thursday...
Scattered showers and storms continue to press through the area
this evening, bringing brief moments of sub vfr ceilings and
visibilities, as well as some lightning. This wave is expected
to continue to press northeast over the next few hours.
Following the rain comes wedge conditions that will produce
very poor flight conditions in the east, impacting LYH and DAN.
Likewise, confidence has increased in that these wedge
conditions look to also impact BCB and ROA. BLF due to its
proximity away from the BLue Ridge looks to make it through the
night fairly well. LWB still remains of question, but given the
precipitation it has received there this evening, confidence
has risen enough to put fog in for tonight.
Tomorrow will see flight conditions gradually improving for TAF
sites near and east of the Blue Ridge. Following the improving
conditions will be yet another possible wave that could impact
flight conditions in the late afternoon, but high- res guidance
remains variable on how much/when these would impact sites so
any mention of showers/storms have been left out of TAFs at this
Extended Aviation Discussion...
The next round of more widespread sub-VFR conditions arrive
Friday night into Saturday with a frontal boundary and
showers/storms. These conditions may linger into the first half
of Sunday before improving conditions through early next week.
Area Forecast Discussion
National Weather Service Topeka KS
601 PM CDT Thu Apr 8 2021
Issued at 248 PM CDT Thu Apr 8 2021
Active upper air pattern persists over the CONUS as the stacked
upper low impacts much of the Midwest, Mid-Atlantic, and Great Lakes
regions while upstream, another shortwave trough is deepening in the
Pac NW region. Wrap around stratus and light rain showers associated
with the stacked low gradually departs east this evening, resulting
in mostly clear skies overnight. Short term guidance hints at broken
to overcast cirrus clouds atop weak sfc high pressure early the
evening. There is a possibility if high clouds clear out, fog may
develop a few hours prior to sunrise, especially across eastern KS.
On Friday, a progressive moving cold front sweeps from northwest to
southeast across the state during the late morning and afternoon.
While tightest sfc pressure gradient resides over central KS, did
increase sustained northwest speeds from 15 to 25 mph with gusts in
excess of 30 mph in the afternoon towards north central areas. Temps
in this portion of the CWA are on the cooler side of the front with
readings falling to the lower 60s. The tight temp gradient spreads
into the lower 70s over far east central KS, just ahead of the
boundary during the late afternoon. Weak elevated CAPE varies
amongst model guidance while strong effective bulk shear on the
order of 40-50 kts is likely. Given the decent forcing along the
front, opted to add slight pops to the entire CWA by late afternoon
for scattered showers and storms to develop along the front,
increasing to chance pops Friday evening across far eastern KS. Not
expecting severe storms at this time given the meager instability in
place, but cannot rule out a stronger storm capable of producing
small hail or gusty winds.
Wrap around showers are likely as the system matures overnight into
Saturday, particularly across far northern and eastern KS. Cloud
cover and showers on Saturday inhibit temps to the low 60s, perhaps
middle 60s in north central areas where precip appears less likely
in the afternoon. Sunday should be the last warm afternoon of the
forecast as warm southerly advection returns ahead of the next cold
front progged to arrive Sunday evening. Highs in the 70s are
probable as southwest winds are on the order of 10 to 20 mph.
Next week`s pattern trends cooler and wetter as a Canadian
longwave trough settles over the western CONUS, ejecting several
vort maxes into the central and southern plains throughout the
week. Timing and location from operational and ensemble guidance
is varied, resulting in low confidence and slight pops in the
extended. Temps overall are near or below normal values from lows
in the lower 40s to highs in the low 60s.
.AVIATION...(For the 00Z TAFS through 00Z Saturday)
Issued at 601 PM CDT Thu Apr 8 2021
Cloud cover and precip into the early afternoon have prevent
boundary layer moisture from mixing out over northeast KS while
west winds and clear have dropped dewpoints into the 20s across
north central KS. The RAP has trended more favorably towards
radiational fog forming as high clouds clear out over the areas
where dewpoints have not mixed out. This includes TOP and FOE. So
with a good nocturnal inversion with light winds and clearing
skies, will include some IFR VSBY with FG developing in the 06Z to
08Z time frame and hanging in until 14Z. With the dryer air
mixing down at MHK, confidence in ground fog is lower and will
monitor trends this evening. Outside of the fog, VFR conditions
are expected to persist. Will need to watch out for some
convection developing Friday afternoon with a front moving in from
the northwest. At this point, probabilities look to small to
include in the forecast.