Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/18/21
forecast discussion, there will be plenty of dry time as well, so
not looking like a washout by any means. Along with the southerly
flow will be increasing moisture drawn up from the Gulf of Mexico,
with precipitable water exceeding 1.25" (+1 to +3 Standard
Anomalies/greater than 90th percentile per NAEFS) into the weekend.
With warm cloud depths also exceeding 3000m at times, there could be
some heavy downpours under any storms that do form, though the lack
of a stronger focus and resulting more scattered to isolated nature
of convection precludes widespread heavy rainfall. There aren`t a
lot of strong signals to latch on to for severe weather in the
extended period, but given increasing instability Wednesday through
the weekend, will have to keep an eye out for any upticks in deep-
layer shear. 17.12Z GFS/Canadian/NAM are showing 30-40 kts of 0-6 km
bulk shear with a wave moving through Thursday afternoon, so this
might be one such time period to watch, although there are varying
amounts of instability to work with in the guidance. Beyond that the
flow aloft looks rather weak as eastern ridging nudges just a tad
westward toward us. The ridge looks to flatten toward the beginning
of next week, but timing/placement differences make predictability
low.
Temperatures from mid-week into the weekend look mild, with
increasing humidity as well. Highs in the 70s and 80s are certainly
possible, but one caveat to the warmth (and to some extent
instability) will be clouds, as low-level moisture looks plentiful
and the possibility of low-clouds at times could temper highs a bit
(more like 60s to 70s if low clouds are more extensive than
currently forecast).
&&
.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 935 PM CDT Mon May 17 2021
Cigs: saturation will be on the increase from the south overnight as
upper level shortwave trough approaches and 850 mb moisture
transport kicks in. Models all suggest dropping into MVFR
(potentially IFR), but differ in how soon that occurs. Consensus
mostly by mid/late morning (15-18z) but certainly could be a few
hours earlier. Once in, the models suggest that they could hold into
Wed.
Caveat to all this is the potential start out and/or improve to VFR
for a period Tue afternoon. RAP/HRRR bufkit soundings favor this for
KLSE, holding the lower cigs to the west/southwest (KRST) initially.
For now, will stay the course with bringing MVFR in to both TAF
sites at similar times, but something to watch.
WX/vsby: scattered to areas of showers should start to spread toward
the TAF sites btwn 15-18z, with chances persisting through the
afternoon. Might be more miss than hit for much of the time, and
what falls looks relatively light. Some hints that drizzle could
precede the rain chances if more low level saturation/lower cloud
bases could be realized. HREF not excited about vsby restrictions,
but a few other models suggest some potential. Will hold onto MVFR
with shra/br for the afternoon for now.
With responsible shortwave trough exiting north in the evening,
expect some decrease in shower activity/areal extent. Mixed messages
in the models on whether fog could then become a concern. Going to
stick with some MVFR reductions with low saturation and some
increase in near sfc moisture (increasing Tds and possible
rainfall).
Winds: generally looking to hold mostly east/southeast through the
period. Some uptick Tue as sfc gradient tightens. A few higher gusts
possible, but low cloud cover will inhibit some of that mixing.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...Zapotocny
LONG TERM...Lee
AVIATION...Rieck
Area Forecast Discussion
National Weather Service Caribou ME
933 PM EDT Mon May 17 2021
.SYNOPSIS...
A cold front will cross the area Tuesday. High pressure will
build south of the region Wednesday through Friday. A cold front
will approach late Friday and stall over the region Saturday. A
second cold front will push through the area Sunday.
&&
.NEAR TERM /THROUGH TUESDAY/...
935 PM Update: Despite a lull in shwr cvrg and intensity, a lead
s/wv impulse alf well ahead of the main s/wv trof slated toward
morn is resulting in a re-surgence of shwrs and even isold tstms
late this eve with some left ovr elevated CAPE. Subsequently,
we xtnded the mention of isold thunder til mdngt. Otherwise,
fcst hrly temps/ dwpts were updated into the late ngt hrs based
on trends seen from latest sfc obs with no chgs to ovrngt lows
posted at 5am.
Prev Disc: Onshore flow tngt will result in a marine layer and
the possibility of patch fog along Coastal Downeast late tngt.
After midnight, a low pressure system to the north will swing a
cold front into the state, starting in the NW and moving SE
across the state through the early morning hours on Tuesday.
Expected scattered rain showers ahead of the front. The timing
of the front still has some uncertainty. NAM and RAP models are
in agreement with the cold front entering the region much
slower, while the GFS and Euro have the cold front passing throw
much faster. Nevertheless, scattered rain showers are expected
across the region while the far north should see numerous
showers. By the afternoon hours, diurnal heating and instability
should support the production of isolated thunderstorms. As the
front passes, NW flow will return, pulling in stable, dry air
and causing showers to diminish. By the evening, the majority of
the shower should be out of the region. Due to the frontal
passage and cloudy skies, temperatures should be slightly cooler
for Tuesday for the area. Expect NW winds to increase after the
front moves through.
&&
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
This portion of the forecast will be dominated by a powerful
upper ridge building over the southeastern US and resulting
subsidence. The air mass will be of the dry Canadian variety
which makes high temps and dew points the biggest challenge.
Went on the high side of guidance for high temps on both days
and on the low side of dew point guidance on both days. Fire
weather is not a huge concern given light winds and the green up
status. Nights will be pleasantly cool with lows in the
40s...and maybe some 30s in the North Woods, but do not foresee
any significant frost issues. Offshore winds will ensure the
warmer temps right to the coast on Wednesday, but the sea breeze
returns Thursday. Thursday may be the warmest day of the week
with readings near 80F north of Hancock and Washington counties.
Can`t rule out an isolated shower or thunderstorm in the North
Woods on Thursday afternoon, but not too concerned given the
strong ridging.
&&
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
The massive upper ridge over the SE US retrogrades back towards
the lower Mississippi Valley and allows northern stream
shortwaves to move along the northern periphery of the ridge
across Maine Friday into Sunday. The air mass will become
moister as dew points rise towards the 50s by Saturday. The
first shortwave will offer the risk of thunderstorms Friday
afternoon and evening. Went for high temps slightly cooler than
Thursday due to the moister air mass, cloud cover and an
emerging onshore flow across the area. The associated surface
front then stalls over the area Friday night into Saturday with
enough clouds to further reduce highs on Saturday to the lower
70s and the continued risk of scattered showers and
thunderstorms. A stronger shortwave arrives Sunday and could
generate strong thunderstorms if the timing is right. Expect a
drier and cooler Canadian air mass to follow for the beginning
of next week.
&&
.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
NEAR TERM: VFR this evening and tonight. Light SW winds. Possible
MVFR in showers and thunderstorms. By early morning Tuesday,
BHB possible IFR with patchy onshore fog. Elsewhere, VFR,
possible IFR for Aroostook terminals with patchy fog in areas
that had rain and mostly clear skies. By Tuesday afternoon, VFR
with MVFR in rain and thunderstorms. SSW winds 10-15 kts.
SHORT TERM:
Tuesday night into Friday evening...Predominately VFR with light
winds and just a small risk of fog near the coast Thurs night
into Friday morning. There is a chance of thunderstorms Friday
afternoon and evening.
Friday night into Saturday morning...Chance of thunderstorms,
risk of IFR fog/stratus for BHB and BGR, MVFR tempo IFR cigs
further north. Light winds.
&&
.MARINE...
NEAR TERM: Winds and seas will remain below SCA criteria through
Tuesday. Fog will reduce visibility at times for tonight and
early morning Tuesday.
SHORT TERM: No advisories are expected during the period. Fog
becomes a concern Friday evening through Saturday night.
&&
.CAR WATCHES/WARNINGS/ADVISORIES...
ME...None.
MARINE...None.
&&
$$
Near Term...VJN
Short Term...MCW
Long Term...MCW
Aviation...VJN/MCW
Marine...VJN/MCW
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
918 PM CDT Mon May 17 2021
.UPDATE...
Quick forecast update. The main change was to adjust PoPs and QPF from
now through about 1 am. The highest PoPs and QPF are now centered
around Zavala and Dimmit county where ongoing convection is producing
a lot of lightning and some moderate to heavy rainfall. Mesoscale
models are still all over the place, but the new 00z HRRR and new 00z
generally suggest that most areas other than the Rio Grande will stay
dry through much of the night. Earlier model runs developed an MCS
and brought it across our area during the early morning hours on
Tuesday. The 00z HRRR takes the storms across northwest Texas now
and forms an MCS out of them and drags that into our Hill Country
counties early Tuesday afternoon. It then continues moderate to heavy
rainfall across the I-35 corridor and points northward through the
evening until around 11pm tomorrow night. The new NAM on the other
hand creates an MCS over Mexico late tonight and moves it across
Maverick, Zavala, and Dimmit Counties. The model may have picked up
on whatever is causing the current convection and may just be running
a few hours later. Both models generate a large MCS across the Rio
Grande and/or Hill Country late Tuesday night and brings it through
our area during the day on Wednesday.
For this update have followed the mesoscale models and radar trends,
dropping PoPs for much of the I-35 corridor and Coastal Plains
through the evening. Have maintained Chance PoPs (around 30%-40%) for
the early morning hours across much of the area to cover any
potential new development.
&&
.PREV DISCUSSION... /ISSUED 659 PM CDT Mon May 17 2021/
UPDATE...
A Severe Thunderstorm Watch has been added for Dimmit, Frio,
Maverick, and Zavala Counties. An outflow boundary from convection
across the I-35 corridor earlier in the day is interacting with a
very conducive environment for storms and has produced one Severe
Thunderstorm already that is drifting to the southeast across the
eastern portion of Dimmit County.
AVIATION...
A complicated forecast for the TAFs, especially when it comes to
convection. Addressing the easy part in general expect VFR skies this
evening across the I-35 corridor. Some localized MVFR clouds have
developed over Bexar County for SAT/SSF but do not expect those to
last more than an hour or two. With the moist atmosphere in place
MVFR ceilings are likely at all TAF sites around 06z and should last
through the mid-morning hours on Tuesday. With respect to convection
have based the inclusion of PROB30 groups on a consensus of
mesoscale models which show convection along the Rio Grande this
evening, with a possible second round developing later tonight.
These storms will generally move to the east overnight and into the
I-35 corridor by the early morning hours on Tuesday. It is important
to note that the convective forecast with this TAF package is very
low confidence as mesoscale boundaries and small changes will have a
large impact on the timing of convection tonight into Tuesday. Winds
will generally continue out of the southeast.
PREV DISCUSSION... /ISSUED 319 PM CDT Mon May 17 2021/
SHORT TERM (Tonight through Wednesday Night)... An upper level low
was centered near the Four Corners area this afternoon. The low level
flow was from the southeast and the airmass over South Central Texas
remains warm and moist. A line of thunderstorms stretched across the
eastern half of the area moving toward the south. These storms have
been just short of severe and this activity will continue for the
next several hours. The next focus will be out west where we have
just issued a Tornado Watch for Val Verde County. Convection has
started to initiate over West Texas and the mountains in northern
Mexico. Conditions are favorable for severe thunderstorms with
tornadoes possible. In addition to tornadoes very large hail is
possible this evening. Convection will continue to be likely
overnight. Deep moist air is in place with PW values in excess of 1.5
inches across the southern half of the area. This will start an
extended period of possible locally heavy rain. The upper and lower
patterns will remain virtually unchanged through Thursday morning. As
the upper low moves slowly to the northeast over the next 48 hours
or so, we expect multiple rounds of showers and thunderstorms
Tuesday and Wednesday. There will be ample instability and sufficient
deep layer shear for strong to severe storms both Tuesday and
Wednesday. The better chances for severe will be Tuesday across the
northeastern part of the CWA. Locally heavy rain will continue to be
possible. With the multiple rounds of convection we expect rainfall
totals to be eight to ten inches along I-35 from Austin through
Williamson County. Outside of this area, two to six inches with
locally higher amounts is possible as far west as Kerr, Medina, and
Frio Counties. Lesser amounts are likely farther west.
LONG TERM (Thursday through Monday)...
Another upper level low will move onto the west coast Thursday
keeping Texas in the unstable southwesterly upper flow through the
weekend. While the low level flow will remain southeasterly, the
extreme moisture will retreat to the east. This will mean the locally
heavy rain threat will come to an end Thursday afternoon. However,
rain chances will continue. For the end of the week convection should
be more diurnally driven with higher POPs during the daytime periods
and lower POPs overnight. It`s a little early for forecasting any
severe potential, but this is climatologically the peak of our
severe season and the threat may come into better focus over the next
few days.
&&
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 86 71 83 69 79 / 40 40 90 80 80
Austin Bergstrom Intl Airport 86 71 84 69 79 / 40 40 80 80 80
New Braunfels Muni Airport 87 73 85 70 81 / 30 40 80 70 80
Burnet Muni Airport 84 69 81 68 79 / 30 40 90 60 70
Del Rio Intl Airport 94 71 93 72 86 / 10 40 20 30 60
Georgetown Muni Airport 85 70 82 68 79 / 40 40 80 70 80
Hondo Muni Airport 89 71 86 70 80 / 20 50 60 50 80
San Marcos Muni Airport 86 72 84 68 80 / 30 40 80 70 80
La Grange - Fayette Regional 86 73 86 71 81 / 50 30 80 70 90
San Antonio Intl Airport 86 72 84 70 81 / 30 40 80 60 80
Stinson Muni Airport 89 73 86 71 81 / 20 40 70 60 90
&&
.EWX WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through Thursday afternoon for Atascosa-Bandera-
Bastrop-Bexar-Blanco-Burnet-Caldwell-Comal-De Witt-Fayette-Frio-
Gillespie-Gonzales-Guadalupe-Hays-Karnes-Kendall-Kerr-Lavaca-Lee-
Llano-Medina-Travis-Williamson-Wilson.
&&
$$
Short-Term/Aviation...Treadway
Long-Term...Brady
Area Forecast Discussion
National Weather Service Goodland KS
728 PM MDT Mon May 17 2021
.UPDATE...
Issued at 726 PM MDT Mon May 17 2021
Updated the Tonight to Tomorrow time period to provide a smoother
transition between current conditions and storms expected to move
into the area from the southwest this evening prior to lifting out
of the area after midnight with some redevelopment by mid day
Tuesday.
&&
.SHORT TERM...(This evening through Tuesday night)
Issued at 315 PM MDT Mon May 17 2021
Overview: A deamplifying upper level low, presently situated over
the Desert Southwest, will slowly progress eastward across the
southern Rockies tonight through Tuesday night.
Through Tonight: An MCV (emanating from widespread convection
yesterday evening), initially situated invof southern
Greeley/Wichita counties at sunrise, currently (as of 21Z)
situated invof Goodland.. will continue to weaken/deamplify as it
lifts north toward the Nebraska border. Convection associated with
this feature has steadily weakened during the past few hours, and
will likely continue to weaken.. as activity progresses northward
into an increasingly stable/capped airmass. Convection presently
developing along the I-25 corridor in southern CO and central/
northern NM is anticipated to merge/coalesce into a NW- SE
oriented line this evening.. approaching southwest portions of the
area (i.e. Cheyenne county, CO and Greeley/Wichita counties, KS)
around 04Z. However, the approaching convective line will
encounter an increasingly unfavorable /worked-over/ airmass with
northern extent.. and simulated reflectivity forecasts via the
HRRR and NAM NEST suggest that rapid weakening is likely
thereafter.. with activity more-or-less dissipating by 06-08Z.
With the above in mind.. severe weather is not anticipated in the
WFO Goodland CWA. Given that ongoing convection associated with
the lingering MCV has already begin to weaken.. locally heavy
rainfall /isolated flash flooding/ appears unlikely from this
point onward.
Tue-Tue night: Scattered convection may develop over portions of
the area Tue aft/eve.. though recent runs of the HRRR and NAM NEST
suggest that coverage is very much in question. Given that the
thermodynamic environment upstream of the region will be altered
(to some degree) by widespread convection this evening, and that
forcing will, once again, largely be tied to mesoscale features
(directly or indirectly) associated with convection.. considerable
uncertainty persists.
.LONG TERM...(Tuesday night through Monday)
Issued at 332 PM MDT Mon May 17 2021
The long term period is looking drier than the start of the week
with temperatures that are slightly above average. In spite of the
drier pattern, chances remain nearly daily for rain and storms.
Wednesday continues to see the upper level low that moved in from
the west diffuse out into the larger flow as a ridge sets up in the
east and a trough sets up in the west. This general upper level
pattern then should persist through the remainder of the period
leaving the Tri-State area in southwest flow. Near the surface,
higher pressure will slowly move in through the remainder of the
week. However, low pressure systems may come off the Front Range
each day and could increase synoptic lift and rain chances. The air
aloft looks to dry out through Friday which should lower cloud cover
and chances for precip. However, guidance suggests that moisture
gets pulled northward during the weekend though how much is
uncertain.
What this means is that Wednesday still looks to be a transition day
with precip chances decreasing and cloud cover decreasing through
the day. There is still a chance for storms and a few could become
severe though confidence is not great in that regard. High
temperatures are forecasted to be in the low 70`s.
Thursday and Friday are looking drier and warmer with high
temperatures reaching up into the low 80`s and sunnier skies during
the day. There still could be some isolated storms that form with
dewpoints reaching the upper 50`s and lower 60`s, but the low
synoptic forcing and drier air aloft is expected to lower the
overall coverage. Some may become severe with lapse rates
approaching 8-9C and MLCAPE getting above 1000 J/KG but this is
remains uncertain for now.
This weekend and into Monday looks to be similar to the end of the
week but with a few changes. First, moisture is expected to move in
aloft from the south which would increase moisture available for
storms that form though nothing producing extreme amounts. Secondly,
the upper level trough is forecasted to move north and east and
flatten the ridge. At the same time, lower surface pressure is
forecasted to move into the northern Plains. Depending on how far
south it moves, the low pressure maybe able to add some synoptic
lift to the area. Finally, the cold front mentioned in previous
forecasts is looking less certain on when/if it would move through
the area with latest guidance suggesting Monday. Given the
inconsistencies in the handling of this front and slow movement of
the trough, I am currently leaning towards a warmer forecast for the
weekend. Temperatures are currently forecasted in the upper 70`s but
expect this to vary some as the weather pattern becomes clearer.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 534 PM MDT Mon May 17 2021
The scattered showers currently extending along the northwest
Kansas and southwest Nebraska border will continue lifting
northward across over the next few hours with another area of more
widespread showers and thunderstorms lifting northeastward out of
southeast Colorado across western Kansas into southwest Nebraska
between 06-12Z. Areas of fog are possible overnight. There is a
lul in showers expected Tuesday morning with additional
thunderstorm development expected generally after 17Z.
GLD will see mainly MVFR conditions primarily due to low ceilings through
05Z. After 05Z, conditions will deteriorate and vary between IFR
and LIFR due to low ceilings and visibility with fog rain showers
with isolated thunder through 14Z. After 14Z, expect low ceilings
and LIFR conditions to persist.
MCK will drop from MVFR to IFR with intermittent LIFR between
06-19Z and thunderstorms mainly between 09-11Z. After 19Z, MVFR
conditions are expected along with scattered thunderstorms.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
UPDATE...LOCKHART
SHORT TERM...VINCENT
LONG TERM...KAK
AVIATION...LOCKHART
Area Forecast Discussion
National Weather Service Huntsville AL
1057 PM CDT Mon May 17 2021
.UPDATE...
For 06Z TAFS.
&&
.NEAR TERM...(Rest of tonight)
Issued at 959 PM CDT Mon May 17 2021
Surface high pressure that brought the chilly weather last week has
moved east of the Mid Atlantic. A southerly flow rounding its
western periphery has helped continue a warmer trend, with high temps
earlier today in the mid 70s to around 80. Mid evening temperatures
have cooled into the upper 60s to mid 70s with light ESE winds.
As of the mid evening, local and regional radars indicated light
showers moving to the NE over NW Alabama. While measurable precip has
not been noted yet, a trace has fallen so far at Haleyville, with
0.01" in Marion AL and Amory MS in Monroe county. HRRR and RAP output
has not been handling this light precip well, as was the 00Z NAM.
Radar trends have these showers heading to the NE, while on a
diminishing trend. A layer of drier air above the surface was
evaporating most of the precip before it reached the surface. Going
with continuity and those showers, have kept lower end rain chances
going mainly for areas west of I-65. Soundings instability looks too
minimal for thunder, so will maintain a thunder free forecast. Lows
not as cool as last night in the low/mid 60s looks fine.
.SHORT TERM...(Tuesday through Wednesday)
Issued at 219 PM CDT Mon May 17 2021
Tuesday looks to house the best shot at the low-end chances for rain
for the area for the next 7-10 days. If we don`t see much then, it`s
looking pretty bleak for the rest of the extended forecast period for
the TN Valley. This is good news for those of you ready for Summer!
For the rest of you pluviophiles out there (myself included), this
may be the last shot for somewhat appreciable rainfall for a while
as the unofficial start of Summer begins next weekend.
Short-term models continue to lessen their chances for rainfall
tomorrow (again, thunder was removed from the fcst), but what does
fall, will dissipate as the day wears on, with the best chances
by/before midday Tuesday. Otherwise, the upper ridge to the south
begins building N, essentially shutting off any changes for rain
while it dominates the weather pattern for the rest of the
week/weekend. Temperatures for Tue/Wed will top out in the middle 80s
(with morning lows starting out in the middle 60s).
.LONG TERM...(Wednesday night through Sunday)
Issued at 219 PM CDT Mon May 17 2021
The H5 ridge S of the CWFA begins to build Nwrd and strengthen for
the remainder of the week/weekend ahead. With little in the way of
rainfall expected thanks to subsidence in place across the area,
temperatures will rise into the lower to perhaps middle 90s by this
weekend. This is pretty close to climatology for the area, with the
first 90-degree day falling somewhere in the last week (or so) of
May. Either way, it looks like it should shape up to be a nice
(albeit hot) Memorial Day weekend for the area. Morning lows will be
mild, only falling into the lower/middle 60s each day.
&&
.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1057 PM CDT Mon May 17 2021
VFR flight conditions are expected to persist through the TAF period
at both terminals. Some light showers were seen on radar, but expect
those to dissipate by 06z. Breezy southeasterly flow will pick up
during the daytime hours on Tuesday, with wind gusts as high as
20kts. Should see a thinning in cloud cover and slackening winds by
the evening hours.
&&
.HUN WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
TN...NONE.
&&
$$
NEAR TERM...RSB
SHORT TERM...12
LONG TERM...12
AVIATION...25
For more information please visit our website
at weather.gov/huntsville.
Area Forecast Discussion
National Weather Service Wichita KS
910 PM CDT Mon May 17 2021
.UPDATE...
Issued at 910 PM CDT Mon May 17 2021
Loss of afternoon heating has led to most of the diurnally driven
cumulus to diminish for the late evening hours. So with loss of the
heating, also think chances of diurnally driven showers or storms is
diminishing to near zero as well. So plan on removing most of the
pops for the evening hours, as latest RAP doesn`t show any low level
moisture transport pushing back into KS until well after
midnight.
Next impulse to round the base of the main upper low, situated over
the Rockies, will begin to lift northeast out of NM and towards KS
late tonight or early on Tue morning. Lift associated with this
next impulse will lead to shower and embedded thunderstorm chances
increasing for early Tue morning, and certainly for the daytime
hours on Tue. So after this evenings lull, will ramp back up pops
for most locations for Tue morning.
Ketcham
&&
.SHORT TERM...(This evening through Thursday night)
Issued at 315 PM CDT Mon May 17 2021
The periodically wet and stormy weather pattern will continue
through the mid-week periods. While an a few showers and storms
cannot be ruled out through this evening in the weakly unstable
and uncapped airmass, better chances look to arrive late tonight
into Tuesday as a more pronounced shortwave upper trof looks to
rotate northeastward across the area, ahead of the main upper low
moving across the southern Rockies. While timing may be nuanced,
another such wave looks to move across the area late Tuesday night
into early Wednesday before the main upper trof opens up and lifts
northeastward across the Plains Wednesday night into Thursday.
The combination of moderate instability and shear at times will
give rise to a few strong and perhaps marginally severe storms the
next couple of days, though localized, yet transient areas of
heavy rainfall will remain the main threats. Temperatures will
continue to average near or just a couple degrees below seasonal
climo in the rather moist/humid airmass.
Darmofal
.LONG TERM...(Friday through Monday)
Issued at 315 PM CDT Mon May 17 2021
Periodic chances for showers and storms will continue through the
weekend and into early next week. However, chances could be
squelched or shunted a bit further west for a time, as an upper
ridge retrogrades across the lower Mississippi Valley into the
Ozarks. This may focus the better chances for deep convection
across the high Plains where better meridional flow and
instability will exist to the east of the deep western conus
upper low. This upper low/trof is progged to lift bodily north and
then eastward across the Rockies and northern Plains Sunday night
into Monday with perhaps better chances spreading into eastern
Kansas again.
KED
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 631 PM CDT Mon May 17 2021
Expect VFR conditions for the remainder of the evening hours, as
diurnally driven cumulus clouds dissipate after sunset. As the
overnight approaches, low level moisture is expected to increase
again after midnight and towards 09-10z/Tue, with CIGS dropping to
MVFR and then IFR as the next impulse on the SW flow moves NE out of
OK. As this impulse moves northeast, the chance for SHRA will
increase. By the daytime hours on Tue, increasing elevated
instability may lead to some scattered TSRA as well. So will go with
prevailing SHRA and VCTS for most locations for the daytime on Tue.
Ketcham
&&
.PRELIMINARY POINT TEMPS/POPS...
Wichita-KICT 60 74 61 75 / 50 70 80 60
Hutchinson 58 73 60 75 / 50 70 80 50
Newton 58 73 61 74 / 40 70 80 60
ElDorado 59 73 61 74 / 40 70 80 70
Winfield-KWLD 60 74 61 75 / 50 70 80 70
Russell 57 71 57 76 / 50 70 70 60
Great Bend 58 71 57 75 / 50 70 70 50
Salina 59 74 60 76 / 30 70 80 60
McPherson 58 73 60 75 / 40 70 80 60
Coffeyville 61 76 63 76 / 30 70 80 80
Chanute 60 75 63 75 / 30 70 80 80
Iola 59 74 62 75 / 30 60 80 80
Parsons-KPPF 61 75 63 75 / 30 70 80 80
&&
.ICT WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Ketcham
SHORT TERM...KED
LONG TERM...KED
AVIATION...Ketcham
Area Forecast Discussion
National Weather Service Jacksonville FL
856 PM EDT Mon May 17 2021
...WARMING TREND UNDER BREEZY EASTERLY FLOW CONTINUES...
.UPDATE...
Breezy onshore flow will continue over the local area through
Tuesday with more low level cloudiness and a low chance of spotty,
light coastal showers near the Golden Isles and possibly
Flagler/St. Johns counties into Tuesday where a couple of
convergent bands may set-up.
A general warming trend will continue with seasonably warm
temperatures ranging from lows in the low 60s coast to upper 50s
across inland SE GA, to highs in the low/mid 80s inland to near 80
coast. Shallow patchy ground fog may develop in a few inland
locations where wind decouple after midnight tonight, but elevated
boundary layer winds and passing clouds will prevent significant
fog development.
&&
.MARINE...
High pressure ridge will remain to the north of the waters through
the week. A long fetch of strong easterly winds will persist with
seas remaining elevated. Updated the offshore waters this evening
to Exercise Caution due to winds of 15-20 kts and there could be
some light showers nearing our outer GA waters later tonight into
Tuesday as a convergent band sets up.
Rip Currents: High to moderate risk expected through the upcoming
week.
&&
.FIRE WEATHER...
Elevated dispersion near 20 units will continue near a late
afternoon wildfire that developed near Colee Cove in inland St.
Johns county (noted on IR imagery this evening). Smoke from this
fire will continue stream westward across Clay county.
&&
.PREV DISCUSSION [804 PM EDT]...
.NEAR TERM [Tonight through Tuesday]...Easterly flow will persist
with high pressure situated to the north. Dry weather will
continue with gusty winds especially near the coast. Temperatures
will continue to be slightly below average.
.SHORT TERM [Tuesday night through Thursday Night]...
Deep layer of high pressure will strengthen to the north of the
area. A breezy onshore flow will persist and increase bringing a
slight increase in low level moisture. Rain chances will be too
low to mention as models show a low potential for coastal showers.
.LONG TERM [Friday Through Monday]...
High pressure ridge at the surface and aloft located to the north
on Friday will retrograde southwest through the period. The dry
pattern will continue as the airmass remains too dry for
precipitation. Near average temperatures will become above
average by early next week with daily highs reaching the lower
90s.
.AVIATION...
[Through 00Z Wednesday]
Prevailing VFR conditions under breezy easterly flow will continue
through the forecast period under passing cumulus moving onshore
with cloud bases primarily 4-5 kft. There could be brief periods
of 2-3 kft bases late night and early morning near coastal
terminals as well as spotty, light coastal showers, with latest
HRRR suggesting this potential near SSI around 10-14z Tue morning.
Given low potential of occurrence, refrained from VCSH in the
forecast at this time. Gusty easterly flow 20-25 kts picks-up
mid-morning Tue, continuing to spread inland toward VQQ/GNV into
the afternoon and early evening before weakening after sunset.
.FIRE WEATHER...Strong easterly winds will produce high dispersions
the next few days. The dry weather pattern will continue with
minimum RH values remaining above critical levels.
&&
.PRELIMINARY POINT TEMPS/POPS...
AMG 59 83 60 83 59 / 0 10 0 10 10
SSI 68 81 68 81 67 / 10 10 10 10 10
JAX 63 81 65 81 66 / 0 10 10 10 10
SGJ 66 79 67 79 67 / 0 10 10 10 10
GNV 61 84 61 84 61 / 0 10 10 10 10
OCF 61 86 64 85 63 / 0 10 10 10 10
&&
.JAX WATCHES/WARNINGS/ADVISORIES...
FL...None.
GA...None.
AM...None.
&&
AREA FORECAST DISCUSSION
National Weather Service Morristown TN
905 PM EDT Mon May 17 2021
.UPDATE...
EVENING UPDATE.
&&
.DISCUSSION...
Radar shows a few weakening showers/sprinkles still around. The
best chance for any measurable rain still looks north. Will leave
PoPs/Wx as they are as the diminishing trend depicted in the
forecast still looks to be on track. Will just tweak hourly temps
and dew points with this update.
&&
.AVIATION...
00Z TAF DISCUSSION.
A few showers will be around at times, especially early and late
in the period at TRI. Will include vcsh during these times for
TRI. If precipitation actually occurs at TRI this evening, then
fog will be more likely, but for now will keep the fog out given
uncertainty of any precipitation there. Otherwise, there will be
varying amounts of mainly high and mid clouds during the period
all sites. VFR conditions forecast all sites for the period.
LW
&&
.PREV DISCUSSION...
/ISSUED 329 PM EDT Mon May 17 2021/
SHORT TERM...(Tonight and Tuesday)...
Key Messages:
1) Isolated to scattered afternoon showers and possibly a
thunderstorm over the far northeast, but otherwise dry with near
normal temperatures.
Discussion...
Afternoon water vapor imagery along with RAP analysis places a
deep low near the four-corners with a shortwave progressing out of
the central plains. Further east, weak amplitude ridging continues
across the local area. At the surface, a weak front was noted to
the north of the area. Despite previous guidance depicting
isolated showers and thunderstorms developing, the strength of
the H70-H50 ridge likely has inhibited this development thus far.
However, continued moisture pooling along with further boundary
layer heating could still yield at least a slight chance of shower
development through the afternoon hours. GOES16 RGB`s have shown
recent increases in cloud tops over the past hour. Can`t rule out
a thunderstorm given some weak instability present. This activity
will be confined to far NE portions of the forecast area.
Tonight will remain quiet as ridging continues across the Southern
Appalachians while a weak shortwave lifts quickly NE into the
Ohio Valley. Overnight temperatures will be mild with lows in the
mid 50s to low 60s. Moisture aloft will continue to promote mostly
cloudy skies through the night. On Tuesday, conditions look
mainly dry as heights continue to increase over the area. However
cannot rule out an isolated shower or two mainly north and east of
the Knoxville area. Tomorrow looks like another warm day with
highs approaching the upper 70s to low 80s.
Diegan
LONG TERM...(Tuesday night through Monday)...
Key Messages:
1. Mostly dry weather through the extended with just a very small
chance of isolated convection across the higher elevations.
2. Anomalously strong ridging will bring much above normal
temperatures and many areas getting into the 90s by the weekend.
Discussion:
The extended period begins with surface ridging centered across the
Southern Appalachians and Mid-Atlantic regions with a strong upper
ridge across the Southeast. This ridge will become stronger through
the week with 500mb heights of 592 to 594 dam centered across the
Tennessee Valley by the weekend. This anomalous ridging is near the
NAEFS 99th percentile to maximum of the climatological record for
this time of year which indicates a reasonable chance of approaching
record max temperatures by the weekend. Record max temperatures for
the week ahead are below:
Daily Record High Maximum Temperatures
Date Chattanooga Knoxville Tri-Cities Oak Ridge
05-17 93(1962) 92(1962) 91(1962) 91(1957)
05-18 96(1962) 94(1962) 92(1962) 93(1996)
05-19 96(1962) 93(1962) 91(1962) 93(1962)
05-20 97(1962) 93(1941) 89(1962) 92(1998)
05-21 95(1962) 95(1941) 93(1941) 94(1948)
05-22 96(1941) 96(1941) 94(1941) 92(1962)
05-23 93(1953) 92(1903) 91(1953) 91(1962)
05-24 94(1953) 92(1904) 88(2019) 93(2019)
05-25 95(1953) 93(2011) 90(1953) 93(1953)
05-26 95(2019) 94(1926) 91(2012) 92(2019)
With strong subsidence across the area, precip chances will be too
low to mention throughout the extended with only a very small (<10%)
chance of a few isolated showers across the higher elevations.
JB
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 62 80 63 85 62 / 10 20 0 0 0
Knoxville McGhee Tyson Airport, TN 60 79 60 83 59 / 10 20 0 10 0
Oak Ridge, TN 58 79 58 83 58 / 10 20 0 10 0
Tri Cities Airport, TN 57 76 55 81 55 / 20 30 0 10 0
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...NONE.
VA...NONE.
&&
$$
...Updated Aviation Forecast Discussion...
.DISCUSSION...
Issued at 245 PM CDT Mon May 17 2021
The main forecast concerns are precipitation chances for the next
several days.
The following features were noted with the large scale pattern from
the 12Z upper air plots. At 300 mb winds were around 70 knots from
southern CA into west TX. At 500 mb there was a closed low centered
over northern AZ, and there were 12 hour height falls of up to
around 60 meters southeast of the circulation. The mid level flow
in our area was quite weak (700 mb winds were calm and both KOAX
and KLBF this morning) so there was not much in the way of
vertical shear. There was a cool pocket at 850 mb over the Great
Lakes with slightly warmer air back over the Rockies.
Skies have pretty much remained cloudy so far today, and where any
breaks have developed, they mostly filled back in fairly quick.
Spotty to scattered showers are likely to continue into the early
evening, then the coverage should slowly decrease. RAP forecast
soundings suggest just enough instability for isolated thunder.
Some fog and drizzle could redevelop again tonight, but exactly
how low visibilities will get is not certain. We should have winds
from 4-8 mph overnight most spots. A weak circulation is expected
to be over northwest MO toward sunrise Tuesday, and that may stir
up some showers, mainly in southwest IA. More showers could pop
up again Tuesday afternoon, but probably with lower coverage than
what we expected today. Look for highs Tuesday mostly from about
70 or the lower 70s - possibly 75 at a few spots.
By Tuesday evening, the closed low at 500 mb over AZ should have
tracked into northeast NM. Models show that system filling as it
tracks northeast through mid week, but a decent piece of energy
may enhance large scale lift in our area late Tuesday night into
Wednesday morning. Will keep POPs fairly high for that scenario.
Another weaker area of lift may move across the area late
Wednesday night into Thursday morning.
By Thursday evening, the 500 mb pattern is expected to feature a
ridge over the eastern US and a trough in the west, putting our area
in southwest flow aloft. The ridge is expected to retrograde
westward a bit toward the Mississippi River valley, with the low
remaining out over NV. That increases our heights and puts our mid
level flow more south/southwest. Stronger flow will remain farther
west until late Sunday or Monday (that seems to be our highest
chance of any organized severe weather the next week). After that,
the flow trends to more zonal by Tuesday May 26.
Highs Wednesday should be mostly 75-80 then look for mainly highs
in the upper 70s and lower 80s Thursday through Monday. A few days
in there could have some mid 80s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 616 PM CDT Mon May 17 2021
Scattered showers affecting the TAF locations at issuance time
with MVFR at KOFK and VFR at KOMA/KLNK. Coverage and certainty of
showers diminishes by 02-05z, with IFR conditions developing. LIFR
conditions develop 05-10z, and then back to MVFR by 17-19z.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.
&&
$$
DISCUSSION...Miller
AVIATION...DeWald
Area Forecast Discussion
National Weather Service Pendleton OR
845 PM PDT Mon May 17 2021
.UPDATE...Minor edits this evening as forecast remains on track.
Breezy conditions to continue tonight and tomorrow as the front
passes. Expanded shower potential tonight to cover a larger
portion of the Blues, the Blues foothills down into the northern
portions of Ochoco/John Day Highlands as the RAP and HRRR are
showing some QPF with the front. Otherwise, the big forecast
highlight will be the much cooler temps behind the front and with
the approaching cold upper level low. Temps Tuesday will be 15-20
degrees cooler than Monday with highs in the upper 50s to 60s in
the low elevations and mid 40s to 50s in high elevations. Even
cooler as we head towards Wed/Thu. Low temps Tue and Wed night are
likely to drop below freezing across portions of the forecast area
and Freeze warnings may be needed.
&&
.AVIATION...06Z TAFs...Increasing high level clouds through the
evening, ahead of approaching system that pushes through tonight.
Skies will become sct-bkn 5-8 kft late this evening and overnight.
A few showers could approach the terminals as well, esp
DLS/PDT/ALW. Expect variable mid to high level cloudiness
tomorrow, with a few afternoon cu buildups. Elevated winds will be
persistent 12-20g22-30kts through Tuesday early evening, before
decreasing Tuesday night.
PREV DISCUSSION... /issued 239 PM PDT Mon May 17 2021/
SHORT TERM...Tonight through Wednesday...Thermal/pressure
gradient firmly in place across the Cascades this early afternoon
has continued to produce breezy westerly winds through the Cascade
gaps and across the Basin into Central OR. Weak cold front
pushing ahead of approaching upper level trough will sustain
breezy winds through the overnight hours. Initial frontal passage
this evening and overnight will bring showers across the Cascades,
with chances dropping off steeply east into the lower elevations
of the east slopes. Behind the frontal boundary, cooler air will
start to filter into the forecast area, with overnight lows
dropping into the 40s to lower 50s. As the frontal boundary
continues to march east early tomorrow morning, the Blues may see
a slight chance of showers, though precipitation will likely be
less than 0.05 inches at any point. Shower chances will continue
across the Cascades and diminish across the Blues Tuesday as
trough axis crosses over the forecast area. Upper level trough
overhead will also produce enough instability over western WA and
the WA Cascades for a slight chance of thunder in this area.
Cooler air will continue to filter into the region with trough
passage tomorrow, with snow levels steadily dropping and afternoon
temperatures mainly in the upper 50s to 60s. Breezy westerly
winds will persist as well Tuesday as tight pressure gradients
continue over the forecast area. By late Tuesday, a closed low
will begin to form over the PacNW and drop south along the WA/OR
coast. Precipitation chances will initially diminish across the
forecast area overnight Tuesday, however as upper low pushes south
Wednesday morning, shower chances will increase again across the
Cascades and northeast mountains. Snow levels will be low enough
in the mountains for high elevation snow flurries Wednesday, with
accumulations through Wednesday afternoon generally less than
half an inch. Wednesday afternoon temperatures will continue the
cooling trend and will be a coupled degrees cooler than Tuesday.
By late Wednesday, center of the closed low will have moved to the
CA/OR border, which will diminish precipitation chances across
most of the mountain zones. Lawhorn/82
LONG TERM...Thursday through Monday...Models continue to be in good
agreement about the pattern in the long term period with just some
minor differences about the location and strength of various
features. An upper low and trough will be the dominant player in
bringing cool and unsettled weather for the late week into the
weekend. Thursday will see the trough overhead with the upper low
moving from southern Oregon into Northern California. There will be
a chance of light rain showers mainly over the mountains and breezy
winds are expected in the afternoon. Friday will see the trough
continuing over the area with the upper low moving into central
Nevada. There will be a chance of showers in the mountains and a
slight chance in the lower elevations with the Columbia Basin mainly
dry. Rain amounts will be less than a tenth of an inch. Saturday
will see the weakening upper low moving back north into eastern
Oregon. The eastern mountains and Blue Mountain Foothills will have
a slight chance of rain showers. Sunday will see the upper low
weakening further and moving into Idaho and Montana. Rain will be
confined to the northern Blue Mountains and Wallowa county. Have
added a slight chance of thunderstorms to Wallowa county on Sunday
with rain amounts of up to two tenths of an inch. On Monday the
upper low will be in Alberta and another upper low will be along the
northern British Columbia coast. This will give us a west to
northwest flow over the area and dry weather is expected. Snow
levels through the long term will rise from around 5000 feet
Thursday to around 7000 feet over the weekend. Those venturing into
the higher mountains of eastern Oregon could see several inches of
snow through the period. Temperatures will start out in the 60s with
50s in the mountains on Thursday then warm a few degrees each day
ending up in the mid 70s to lower 80s with mid 60s to lower 70s in
the mountains for Sunday and Monday. Perry
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 46 63 40 61 / 20 20 0 10
ALW 50 67 42 65 / 0 20 0 10
PSC 53 70 44 68 / 0 0 0 0
YKM 44 66 34 64 / 10 10 0 10
HRI 49 68 42 67 / 0 0 0 0
ELN 42 60 35 60 / 20 10 10 10
RDM 40 61 32 56 / 10 10 10 10
LGD 44 60 38 55 / 10 20 10 20
GCD 45 63 37 57 / 0 10 10 20
DLS 49 64 41 64 / 40 20 10 20
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
&&
$$
UPDATE.......84
SHORT TERM...82
LONG TERM....83
AVIATION.....84
Area Forecast Discussion
National Weather Service Pueblo CO
911 PM MDT Mon May 17 2021
.UPDATE...
Issued at 908 PM MDT Mon May 17 2021
...SEVERE THUNDERSTORM WATCH HAS BEEN CANCELLED FOR PUEBLO,
HUERFANO, AND LAS ANIMAS COUNTIES. THE WATCH STILL REMAINS IN
EFFECT FOR CROWLEY, OTERO, BENT, PROWERS, AND BACA COUNTIES...
-Steward
&&
.SHORT TERM...(This evening through Tuesday)
Issued at 344 PM MDT Mon May 17 2021
Main Forecast Concerns/Challenges:
1) Continued flash flooding risk for all the burn scars into this
evening.
2) Strong to severe storms will remain possible into the evening,
with the highest risk of storms still appearing to be along and
south of the HWY 50 corridor. An isolated stronger storm can`t be
ruled out to the north though, for the Pikes Peak region and Kiowa
county.
3) Increasing chances for snow across the higher terrain through the
period.
Thunderstorms for much of this afternoon have remained tied to the
higher terrain and adjacent locations. Development has remained sub-
severe so far, with only a few stronger storms. However, the
location of his development has been concerning for the flash flood
potential across the burn scars. Think this will continue to be
concerning for the remainder of the afternoon into this evening, as
focus/moist upslope flow persists. While Decker and Hayden Pass
could see some stronger storms with higher rainfall rates, think the
most at risk will continue to be the Junkins and especially the
Spring Burn scar. Strongest development has been focused right in
these areas, and this looks to continue well into the evening. The
overall risk should lower later this evening into the overnight
hours as the main convective activity pushes to the east. As the
upper level system pulls overhead tonight, do think steady light
rain will continue over the burn scars but the rates should not be
enough to produce any flooding at this time.
As noted above, most of the convection has been sub-severe and
mainly tied to the higher terrain. However, have begun to note
development across the far I-25 corridor. Think this is the
beginning of an eastward push of this development, as upper level
system and more vigorous mid level energy lifts across the region.
Surface trough and boundary are evident across far southern CO,
where upper 40s to around 50 degree dewpoint air is located.
Meanwhile, an abundance of sunshine and daytime heating has
occurred, with steepening low level lapse and increasing MLCAPE
values the trend this afternoon. As thunderstorm expands east over
the next couple of hours, think any storm along and south of HWY 50
will quickly become strong to severe. Steep mid level lapse rates
will continue to support large hail, with an axis of higher DCAPE
values situated right along the border supporting damaging winds.
Additionally, the highest shear is analyzed here, with latest RAP
analysis showing values in the 30-35 kt range. Still think there is
a chance for a few weak tornadoes into this evening, as boundary in
place could once again serve as an area of enhanced low level
helicity. RAP analysis is showing a maximized area of 0-3km MLCAPE
and surface vorticity along and east of Walsenburg to Trinidad into
far SE CO. This looks to be a persistent signal into early evening,
and something to keep an eye on for support of tornadic development.
Lastly, upper low moves overhead tonight into Tuesday, and will
support decent chances for widespread precip across southern CO. Did
increase pops and qpf to reflect this thinking, however, may not be
high enough for both. As this system moves overhead, think snow
chances will increase across the higher terrain. Did increase snow
totals but once again, could be on the lower side. Chances for
showers and thunderstorms return on Tuesday, though the severe
threat does not appear to be as high. However, instability and
moisture look to linger and can`t rule out isolated strong to severe
storms Tuesday afternoon across the far southern plains.
.LONG TERM...(Tuesday night through Monday)
Issued at 344 PM MDT Mon May 17 2021
Main Forecast Concerns/Challenges
1) Dryline scenario eastern plains Friday through Sunday
Tuesday night through Thursday...The upper low will be located along
the CO/NM border Tue evening, then weaken and gradually lift to the
north-northeast through the day Wed. The next storm system to affect
the region drops south out of the Pacific NW and into northern CA
and NV through Thu. Models indicate that Tue evening there will
still be around 1000 j/kg of CAPE across the far eastern plains, so
convection will probably linger late into the night before tapering
off. On Wed as the low begins to lift, CAPE and shear really drop
off, but feel that there will be sufficient available moisture for
another round of aftn and evening convection, mainly tied to the
higher terrain, and more scattered for the plains. Strong
southwesterly flow aloft settles in across the Four Corners for Thu,
with a rapid warm-up in max temps and just isolated convection
expected. Plan on highs in the mid 60s to mid 70s for most locations
on Wed, then 70s for the high valleys and 80s for the plains on Thu.
Friday through Sunday...Extended models continue to point to a deep
trough setting up over the western third of the US, with the closed
upper low remaining nearly stationary over NV over the weekend. This
will produce deep southerly flow aloft across the state, with a
healthy tap of moisture feeding into CO. The dryline will develop
over the eastern plains near the eastern border, but may actually
pull west back into CO. This will serve as the focus for strong
thunderstorms each aftn and eve. Meanwhile, multiple disturbances
within the flow will help fire isolated to low-end scattered
convection each aftn across the higher terrain and high valleys.
Plan on highs around 70F each day for the high valleys, and in the
70s to around 80F for the eastern plains. This will potentially be
another very busy period of weather for southeast and south central
CO.
Monday...Long range models agree on finally moving the upper low to
the northeast, shifting the flow aloft across the Four Corners to a
more southwest direction. The dryline should kick east as conditions
dry out, with just isolated convection at best forecast. Temps will
climb into the lower 70s for the high valleys, and mid 70s to lower
80s for the plains. Moore
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 344 PM MDT Mon May 17 2021
Active weather will continue across all the sites, as showers and
storms and low ceilings will remain possible. As an upper level
system approaches, expect showers and storms to continue to develop
out ahead of it. Showers with a few thunderstorms have already moved
across ALS and think similar trends are possible going into the
evening. Thunder chances do look to lower for ALS later tonight,
however, do think rain showers will persist for much of the period.
Additionally, this added moisture could support some lowering of
ceilings through the period.
Similar trends expected at COS, however, COS may observe some
stronger thunderstorms into the evening. The highest confidence for
more prevailing and longer in duration thunder is still at PUB,
where stronger storms are expected to occur into early evening. The
strongest storms, possibly severe, are once again expected at PUB.
Thunderstorm activity should diminish later this evening, though the
upper level system will move overhead through the remainder of the
period and likely provide a longer duration of light rain for all
the sites. In this rain, think MVFR ceilings are possible,
especially across COS. Some possibility for IFR ceilings, but
confidence is low at this time.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch until midnight MDT tonight for COZ072>075-079-
080.
&&
$$
UPDATE...STEWARD
SHORT TERM...RODRIGUEZ
LONG TERM...MOORE
AVIATION...RODRIGUEZ
AREA FORECAST DISCUSSION
National Weather Service Raleigh NC
915 PM EDT Mon May 17 2021
.SYNOPSIS...
A series of weak shortwave troughs will move through the area
tonight through tomorrow, resulting in periods of cloudy skies as
well as a few sprinkles. By Wednesday however, conditions will turn
drier and much warmer with temperatures steadily increasing through
the weekend. Warm/dry weather should persist into early next week.
&&
.NEAR TERM /TONIGHT/...
As of 915 PM Monday...
Forecast is on track. Considerable mid and high clouds will continue
to streak southeastward over the area, thickest over the NW, all
within the right entrance region of the upper jet to our NE and E
and along a weakening mid level shear axis. The latest surface
analysis shows the core of high pressure still sitting off the
Delmarva, while a weaker mesohigh sits just E of the mountains, over
W VA into the NW Piedmont/Foothills of NC, separated from the
offshore high by a weak inverted trough extending from central SC NE
through the I-95 corridor. This weak mesohigh is setting up an in
situ wedge event, with enhanced NE flow (albeit weak) over the
Triad. Model signals of the degree of stratus and/or fog tonight is
varied, but the GFS has sufficient low level saturation and moist
upglide through the 290k-295k depth late tonight over the Triad
region for patchy lower clouds. With nighttime dewpoints continuing
to creep up and continued light surface winds, shallow fog remains
possible, mainly over and N of the Triad to RDU, locations that saw
a few sprinkles in the last several hours, and over bodies of water.
The general muted forcing for ascent and still somewhat limited
moisture below 800 mb favors isolated sprinkles or light showers at
most for the next few hours over the far N and NW, so minimal
changes needed there. Still expect lows from the mid 50s to around
60. -GIH
Earlier discussion from 243 PM: Early afternoon water vapor imagery
continues to show WNW flow across the Mid Atlantic with a weak
embedded shortwave trough making its way through western VA.
Regional radar imagery, vis satellite, and surface obs indicate
light rain ahead of the trough approaching the NW Piedmont as of 18Z
(relatively close to previous HRRR and HREF projections for this
time of day). Conditions remain dry elsewhere but cloud cover has
started re-developing area-wide.
For the rest of the afternoon/evening hours, thermodynamic
parameters are largely unsupportive of convection across the area,
although a few sprinkles or light showers cannot be ruled out.
Surface and mixed layer instability is virtually non-existent given
relatively dry air in the boundary layer and cooler than normal
temperatures from extensive cloud cover. While there is some
elevated instability to work with, it is meager at best (100-200
J/KG MUCAPE) and is mainly south and west of the area (well
displaced from the trough). While it`s possible that there could be
a rumble or two of thunder, that should be the exception and not the
rule. Despite the less than favorable BL, showers presently across
VA should be able to make it into NC late this afternoon/evening,
but will struggle to hang on. I will maintain the idea of 30-40 PoPs
mainly along and north of I-85, with only 10-20 PoPs elsewhere.
While some guidance is suggesting isolated showers overnight, lack
of a strong forcing mechanism should limit areal coverage after
midnight. Where rain does occur this afternoon/evening, moisture
pooling along with light/vrb winds could allow for patchy fog
development. We should have enough low/mid cloud cover overnight to
preclude widespread/dense fog but I felt it was worth a mention in
the forecast nonetheless.
Temperatures tonight should bottom out in the mid/upper 50s.
&&
.SHORT TERM /TUESDAY AND TUESDAY NIGHT/...
As of 243 PM Monday...
WNW flow aloft will continue on Tuesday with yet another weak
shortwave trough forecast to move through the flow and into the Mid
Atlantic. Similar to today, thermodynamic parameters are largely
unfavorable tomorrow afternoon and the areal coverage of showers
that develop should be even less than today. Mid level height rises
and increasingly warm temperatures aloft should further preclude
widespread shower/thunderstorm development. Opting to include only a
slight chance mention of showers tomorrow afternoon along and west
of I-85, but barely (15-20 percent PoPs at most). Any showers that
make it into the area should quickly dissipate by evening, with
gradually eroding cloud cover overnight.
Temps tomorrow should generally hit the mid/upper 70s, with lower
80s to the south. Lows should once again fall into the mid/upper
50s.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
As of 243 PM Monday...
In the upper-levels, a large omega ridge will spread from the
Southeast to the Great Lakes region through the end of the work
week. The ridge will then weaken across the Carolinas and build
towards the Mid-Mississippi Valley this weekend, providing northerly
flow across our region, and then weaken early next week, shifting
flow to more northwesterly.
At the surface, high pressure along the Mid-Atlantic/NC coast
Wednesday will slowly move across NC and into the TN Valley by
Friday. The ridge will weaken over the lower Mississippi Valley into
early next week as a coastal trough develops along the NE/Mid-
Atlantic Coast.
The aforementioned pattern will yield increasing temperatures and
dry weather from ridging and subsidence aloft, with highs increasing
from the low to mid 80s on Wednesday to the upper 80s to low 90s by
Saturday and possibly the low to mid-90s by Monday. Although the
increasing temperatures will make for quite hot weather, dewpoints
in the 50s will prevent it from feeling too muggy and help lows
radiationally cool to the 50s for the end of the work week and the
60s for the weekend into early next week. Precipitation may return
for the middle of next week, however confidence remains low at this
time.
&&
.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
As of 840 PM Monday...
VFR conditions at all sites for most of the TAF period. A few
scattered showers may try and make it into INT/GSO as well as RDU
tonight, but precip intensity should be light enough not to affect
vsbys. Any showers that manage to develop near INT/GSO will likely
remain elevated and not reach the ground. Elsewhere at RWI/FAY,
confidence is not high enough to include a mention of showers at
all, so those sites have been left dry. Any showers that develop
should be over with by 08Z. For those sites that do manage to get
showers tonight (INT/GSO/RDU), there is a low possibility of MVFR
fog/stratus early Tuesday morning. Extensive cloud cover should
prevent conditions from dropping below MVFR but some haze is
certainly possible before daybreak. Conditions will improve to VFR
by 15z Tuesday morning.
Looking beyond 18z Tue, there is a possibility of non-VFR weather
early Wednesday morning due to lingering fog. Mainly VFR weather
expected Wednesday afternoon through Saturday.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Leins
NEAR TERM...Hartfield/Leins
SHORT TERM...Leins
LONG TERM...JJT
AVIATION...Leins/GIH/AS
Area Forecast Discussion
National Weather Service Tucson AZ
257 PM MST Mon May 17 2021
.SYNOPSIS...A storm system will bring cooler temperatures and
gusty afternoon winds today, along with a chance of thunderstorms
with most favorable locations in the mountains northeast of Tucson.
High pressure will heat things back up Wednesday before another
system brings gusty winds and a few degrees of cooling to end the
week.
&&
.DISCUSSION...A low pressure system currently near the 4 corners
region has brought some gusty winds and unseasonably mild
temperatures to SE AZ today. It`s also generating some
thunderstorm activity along the Mogollon Rim north of the area.
Over the next 24 hours the low will slowly push across northern
New Mexico with surface winds relaxing toward normal diurnal
trends and temperatures already climbing back toward seasonal
values for mid May. Meanwhile, a modest moisture increase combined
with a weak impulse rotating around the back side of the low from
the north will bring a decent chance of thunderstorms to the
mountains of Graham and Greenlee county Tuesday afternoon. Most
larger scale deterministic models don`t do much as far west as
Tucson, however it should be noted that HRRR and University of AZ
WRF runs are showing a chance through the Tucson area as well.
Ensembles appear to be tamping this down too much so we`re going
to blend 10 to 15 percent chances into eastern Pinal and Pima
counties as well.
By Wednesday a shortwave ridge will push temperatures back to
several degrees above average.
Another system digging into the Great Basin the second half of the
week will bring back gusty winds Thursday and Friday, along with
a few degrees of cooling Friday. It looks like this one is going
to remain further north as a strong broad ridge takes hold across
much of the southern tier of states and the storm track retreats
northward.
&&
.AVIATION...Valid through 19/00Z.
FEW-SCT mid level clouds W and N/NE of KTUS until 18/04z otrw SKC
thru 18/14z. SCT mid level clouds once again aftr 18/15z with a
slight chc of -shra. Winds W/NW 10-15 kts gusting 20-25 kts thru
18/04z then again aft 18/15z. Winds at other times terrain driven
with speeds 5-10 kts. Aviation discussion not updated for TAF
amendments.
&&
.FIRE WEATHER...A weather system lingering over the area through
mid-week will bring a chance of mainly dry thunderstorms to the
White mountains this evening and then again Tuesday and Wednesday
afternoon. Elsewhere from Tucson east there is a slight chance of
showers on Tuesday. Winds will be breezy today and Tuesday mainly
from Tucson eastward. Wednesday winds will be elevated to the west
and east of Tucson. Wind speeds pick back up Thursday into Saturday
with brief and localized fire weather conditions possible in Cochise
County Friday and Saturday. Minimum RH values will be 10-15 percent
for most locations through Thursday then drop into the single digits
Friday into the weekend.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
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