Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/14/23
Area Forecast Discussion
National Weather Service La Crosse WI
1037 PM CDT Sat May 13 2023
.DISCUSSION...(This evening through Saturday)
Issued at 210 PM CDT Sat May 13 2023
- Scattered storms tonight-main severe weather risk southwest of
the area. A strong or severe (2-5% probability) storm could
reach parts of our northeast IA counties. Heavy rain possible
overnight for northeast Iowa/far southwest WI.
- Rain ending from north to south through the day Sunday, then a
dry start to the work week.
- Although a few showers could affect parts of central WI
Tuesday, the next better chance to see scatter showers/storms
would be Thursday.
Rain/Severe Weather/Heavy Rain Potential through Tonight:
Latest surface analysis shows a well-defined warm front lying
across Iowa from the northwest corner into northeast MO. The
surface low is now in northeast Nebraska with a rich boundary
layer with 68-70F dewpoints in southern IA and the latest SPC
mesoanalysis showing MLCape topping 1500 J/Kg with weak capping.
GOES Day Cloud phase imagery is showing initiation is occurring
along the front with numerous showers to the north in the elevated
decreased CAPE. Low-level stability is confirmed north of the
front with billow clouds seen in the visible GOES imagery.
Currently, most-unstable CAPE values are only 250-500 J/Kg along a
Mason City to Dubuque line, decreasing north of that to 0. In the
partial sky cover north of the surface warm front well to the
south, temperatures are warming and thus instability will be
growing with less capping by later afternoon. But how far the
front can move north is challenging. Latest CAM HRRR trends were
to back off the storms southwestward keeping the area entrenched
in elevated CAPE which remains in the 250-500 J/Kg range. Thus,
the severe storms should remain south of the area (as was
expected). Left-mover storms will have a NW-N vector, and radar
does indicate they are occurring, and supported with fairly
straight elevated hodographs. Those storms would move toward the
area but encounter lower CAPE values and weaken. This is happening
along I-80 at this time near Iowa City. So, it looks more like
scattered showers and storms for this afternoon, with most storms
confined to northeast Iowa. Maybe hail to penny- sized would be a
threat based on current analysis along a Mason City to Dubuque
Further north, frontogenesis anchored at around 700 mb has been
causing showers all day along and north of the I-94 corridor. This
frontogenesis continues into the early evening and would expect
the showers to as well. Have increase rain chances there...again.
Tonight...as the low begins to shift southeast, frontogenesis
increases across the I-90 corridor into southern WI to support a
northwest to southeast rain band across the southernmost forecast
area. Dry northeasterly flow is increasing overnight and undercuts
the band to help decrease precipitable water values in the
column. These should be closer to 1.25" and quite a bit lower than
Friday night, and along with lower MUCAPE/instability indicated
in the RAP and HREF, rainfall rates would be less. With the good
forcing expected, believe a 1-2" rain band, with "normal"
rainfall rates, has a high chance of occurring into Sunday morning
across northeast Iowa and into swrn WI. Most areas should be able
to handle this rainfall with only within-bank river rises
Rain ending from north to south through the day Sunday, then a dry
start to the work week:
Widespread showers and a few storms will be ongoing Sunday Morning
for much of the area south of Hwy 29 in north central WI. The hi-
resolution CAMs appear to have a southern band across northeast IA
into our forecast area and a secondary band farther north near or
north of I90. The southern band is where the 850-700mb
frontogenesis resides. The farther north band appears to be where a
secondary area of mid-level convergence is occurring. Through the
day, the trend is for the area of surface high pressure to build in
from the north and the surface low to continue to drop southward.
With these rising heights, this will suppress the precipitation
southward with time. As has been noted several times this week, the
CAMs have struggled with precipitation, generally under
forecasting the areal coverage. Albeit slow, the general trend of
most of the operational models is to sag the area of showers
southward during the day.
Drier Sunday night, however should the push not be as strong,
sprinkles or a light shower could linger into the early evening.
The start of the work week continues to look dry with considerable
sunshine with forecast sounding showing a lot of mid level drying
ahead of a longwave approaching trough from the north. A few
patchy clouds possible with some passing 850mb moisture.
By Tuesday morning, the 500mb longwave trough will spread showers
into the Upper Great Lakes. The longer range models differ in how
far west the showers will make it Tuesday. The EC has a weaker
front with the showers clipping the area, while the GFS is
farther west with the effect of the cold front. Any precipitation
Ridging builds in for Wednesday with the next cold front arriving
late Wednesday night or Thursday. There are some differences as
well with how quickly the 500mb low exits the area Friday. The
track of the surface low is across parts of Ontario and Minnesota.
At this time, the moisture return appear limited with surface
dewpoints forecast in the 50s and temperatures in the 60s and 70s. A
narrow axis of MUCAPE potential of 500-1000J/kg ahead of the frontal
boundary with 30kts of deep layer shear. At this time the
ensembles/Grand Ensemble has a mean of less than 0.25" of
precipitation with the front. Will need to monitor this as week
get closer to Thursday/Friday.
.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1035 PM CDT Sat May 13 2023
Rain showers will spread east overnight with the passage of a slow
moving front. When this front is overhead of the TAF sites by Sunday
morning, MVFR ceilings are likely with widespread rain showers.
Flight restrictions persist until late afternoon when the rain
dissipates and ceilings recover to VFR.
Area Forecast Discussion
National Weather Service Houston/Galveston TX
1010 PM CDT Sat May 13 2023
Issued at 952 PM CDT Sat May 13 2023
Inverted surface trough, though broader and less easily defined
in the wind field (probably from convection and lower night time
winds) should remain situated somewhere in the vicinity of the
I-45 corridor overnight. Long fetch of moist inflow wrapping in on
the eastern periphery will lead to continued chances of overnight
shra/tstms. HRRR has seemed to have the better handle on
initialization & trends for a good part of the day and
night...though notable run-to-run differences persist in the QPF
field. (Some guidance, even short term, have been abysmal).
Suspect well see a somewhat prevalent band of precipitation
overnight either side of the I-45 corridor. While a general 1-3"
swath of rain will probably be observed in that area between now
and midnight, rainfall rates will likely be the key for any
localized flash flood issues and localized 3-5" amounts. We saw
some localized 2-4"/hour rates earlier this evening and see
little reason that won`t be the thing to keep an eye on overnight.
Exactly where/when it occurs is uncertain, again - probably
either side of I-45, but street flooding and localized rises on
watersheds will be the primary issue if and where this occurs.
Thought about canceling the flash flood watch to our west...as
bulk of potential heavier rain should be to the east. However,
given the uncertainty involved at this time, we`ll let the midnight
crew re-evaluate the full 00z model suite and wx trends. 47
(This evening through Sunday Night)
Issued at 341 PM CDT Sat May 13 2023
Our immediate concern in the short term continues to surround the
potential for locally heavy rainfall over the next 6-12 hours. At
the time of writing (330PM CDT), radar imagery shows the inland
progression of a N-S oriented line of thunderstorms associated with
a slowly moving midlevel shortwave advancing onshore. Observed
rainfall rates associated with this line of storms have at times
approached 3-4 in/hr, although the relatively quick motion of the
storms themselves have thus far not produced much in the way of
heavy rainfall. Furthermore, daytime heating has thus far been
limited by widespread cloud cover and thus stronger instability
values are currently analyzed to the east of the area, away from the
area of greatest forcing. Nonetheless, with fairly steep midlevel
lapse rates, deep moisture availability, and non-negligible surface
based instability, we could still see some strong storms develop
this evening, mainly along and West of the I-45 corridor.
HiRes models have continued to indicate the potential for some areas
of locally heavy rainfall (especially W and SW of the Houston area),
though most locations can expect to receive an additional 1-3 inches
of rain associated with this system. However, given the antecedent
rain from earlier this week across much of our area, flood
conditions may be easier to achieve than typical (again, mainly to
the SW of the Houston area). Given this, a Flood Watch remains in
effect for portions of the area and those with travel plans should
continue to monitor the latest forecast as well as area roadway
The aforementioned shortwave axis will continue to move through the
area tomorrow, resulting in the potential for morning streamer
showers as well as another more widespread round of showers and
storms during the afternoon. New rainfall totals of up to an inch
are possible across the area during this time. Much like today,
daytime heating will be highly dependent on precipitation and local
cloud coverage, but most locations can expect to see highs in the
low to mid 80s and lows in the upper 60s to low 70s.
(Monday through next Friday)
Issued at 341 PM CDT Sat May 13 2023
The entirety of this weekend`s heavy rain event has now slid into
the short term forecast, and the long term largely looks
seasonable for mid-May. However, there are still some things to
talk about, including a couple weak fronts making their way
through the area. It`s...something...though impacts on sensible
weather don`t look to be significant, or notable, or any adjective
in that genre. Indeed, without any real indication of abnormal
weather patterns or outcomes, there doesn`t look to be much
opportunity for me to add value to the seasonable NBM output, so
I looked to largely limit any changes I made to small hedges
against known biases.
Come Monday morning, Gulf ridging will have won the battle for
influence over Southeast Texas, shoving the channel for moisture
and midlevel vorticity well to our west. Rain chances on Monday
look to be about the lowest of the week on this day, though some
isolated showers or storms are still on the menu. Similarly,
Monday may well be the warmest day of the week, though this is
getting mighty close to splitting hairs. What it will do is give
us our best chance of seeing locations reach 90 degrees Monday
afternoon, particularly east of the Houston metro, where the
stacked ridging will be most influential.
We`re still fully expecting a weak front to make its way across
Southeast Texas late Monday night into Tuesday morning as a
decently strong surface high settles into the Great Plains from
Canada. And we`re still fully expecting that single sentence also
largely covers the impact. Look for winds to briefly turn offshore
on Tuesday, but backing to southwesterly as soon as Tuesday
evening, as high pressure over the Gulf quickly becomes the
primary weather feature in the area. A vort max aloft will blunt
midlevel ridging, which should allow for a little more diurnal
convection in the mid-week as well.
Late in the week, we generally return back to the early summer
pattern with mostly onshore winds and the typical diurnal
convection pattern. An upper trough in the northern stream tries
to dig into the Ohio Valley. It won`t do much to impact us
directly, but again keeps ridging flattened down and keep
scattered convection in the picture, rather than getting choked
off by stronger ridging. What it will eventually do is drag a weak
cold front attached to a Great Lakes low through the area next
weekend. Like the mid-week front, I`m not anticipating much to
talk about beyond a brief wind shift. But, it`s probably not wise
to write this front off entirely so far out. Something to watch
(00Z TAF Issuance)
Issued at 628 PM CDT Sat May 13 2023
A mix of MVFR/VFR conditions across the region early this evening.
Surface analysis shows a broad inverted trof axis stretching from
around Freeport-Conroe with a moist Gulf inflow situated to its
east. Still some moderate-heavy downpours occurring near the
Galveston Bay area and short term guidance is trying to flare
things back up northward along this axis in the 2-4z until 10z
timeframe. Question is exactly where it`ll set up...just east or
west of the I-45 terminals?. Going to be close, but consensus...for
what it`s worth...is just west of I-45. Training intermittent
heavy rain not out of the question at times, but considerable
model run-to-run uncertainty was noted in terms of intensity.
Suspect ceilings will trend downward overnight to mainly MVFR and
will keep an eye on trends in regards to the wx and issue
amendments as needed.
Probably somewhat of a lull in activity ~14-19z, and ceilings lift
toward VFR territory. After that, the potential for additional
tstm development exists thereafter with any heating (degree of
which uncertain considering mostly overcast conditions). 47
Issued at 341 PM CDT Sat May 13 2023
There will be a daily chance of showers and thunderstorms this
weekend across the coastal waters, but particularly on Matagorda
Bay and the lower Gulf waters. Daily chances for isolated to
scattered showers and storms will also carry deep into the new
week. Southeasterly winds will prevail through the weekend and
will periodically reach caution flag and advisory territory,
especially during the overnight to early morning hours.
Expect winds to become lighter and more variable early Tuesday
morning as a weak front makes its way offshore. However, onshore
flow will return quickly, and is expected to continue until the
next potential front next weekend.
At the shore, rip currents look to be an issue as long as the
persistent onshore flow continues, disrupted only by lighter,
more variable winds around the weak front. Expect water levels to
run 6-12 inches above astronomical tides, but short of levels that
typically cause any coastal flooding issues.
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 70 81 68 84 / 70 60 20 30
Houston (IAH) 72 82 70 89 / 80 60 20 20
Galveston (GLS) 71 79 74 83 / 90 40 10 10
TX...Flood Watch through Sunday evening for TXZ210-226-235-236-335-
High Rip Current Risk through Sunday evening for TXZ436>439.
GM...Small Craft Should Exercise Caution until 4 AM CDT Sunday for
Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
616 PM CDT Sat May 13 2023
Issued at 210 PM CDT Sat May 13 2023
- Cooler temperatures and continued rain showers/rumbles of thunder
expected through the rest of the weekend.
- Tuesday and Wednesday will be the warmest days of the week with
highs in the upper 70s to low 80s.
- The next chance for showers and thunderstorms is anticipated on
Wednesday and Thursday. Confidence remains low on the severe
potential at this time.
Recent GOES-16 WV and RAP 500-analysis showed a broad low
pressure system situated across far northern Maine into New
Brunswick with a trough extending across New England into Ontario.
Further south of this feature, a deep layer ridge of high
pressure encompassed much of the southeastern CONUS. Further
northwest of this feature, an upper-level low was apparent across
the Texas Panhandle. An area of low pressure was retrograding
into the Great Basin with high pressure centered across British
Columbia. Closer to home, the low pressure system that was
responsible for yesterday`s severe weather was centered over far
southeastern South Dakota. At the surface, associated surface low
pressure was noted north of Omaha with an occluded front across
far southeast Iowa. Further north, broad surface high pressure
encompassed much of the central Provinces of Canada. The
aforementioned low pressure system has resulted in persistent
cloudy skies across western and north central Nebraska with light
showers impacting portions of the northern Sandhills into north
central Nebraska. Though any lift and forcing remains weak across
the area, meager instability may cause a rumble of thunder within
these showers through the evening hours. As of 2 PM CT,
temperatures ranged from 64 degrees at Ainsworth to 69 degrees at
.SHORT TERM...(This evening through Sunday night)
Issued at 210 PM CDT Sat May 13 2023
The aforementioned upper-level low will gradually push across Iowa
and Minnesota before becoming an open wave and dissipating later tonight.
Rain shower coverage will increase tonight for areas primarily
north of I-80 in the wake of the departing low. These rain showers
will become more widespread across the entire area on Sunday as
the previously mentioned Canadian high pressure pushes south with
the trough axis bisecting much of the region. Deep layer moisture
persists into Monday which is depicted by NAEFS and ENS ensemble
guidance suggests that the mean PWAT will meet or exceed the 99th
percentile across much of the area. Though these rain showers will
be widespread, rainfall amounts of only a tenth of an inch to
near three tenths of an inch is anticipated through Sunday.
In regards to temperatures, overnight lows tonight and Sunday will
be in the above normal range in the 40s and 50s. Daytime highs will
be rather chilly on Sunday ranging from the mid 50s across the
Sandhills to the mid 60s across southwestern Nebraska. Breezy winds
will continue into Sunday behind the departing system with
northwesterly winds today before veering towards the northeast on
.LONG TERM...(Monday through Saturday)
Issued at 210 PM CDT Sat May 13 2023
The previously mentioned westward retrograding low pressure system
aloft will become near stationary across the PNW coastline Monday
into Monday night. High pressure will encompass the area Monday into
Tuesday, though the ridge axis will remain weak with multiple weak
disturbances aloft tracking across the area. Isolated rain showers
are possible Monday and again Tuesday afternoon and evening.
However, confidence in the area seeing any rain showers remains
low at this time given differences amongst model solutions. Most
model solutions are in agreement with the area remaining dry
during this period, however, some ensemble members are hinting at
the potential for an isolated rain shower or two. If any rain
showers do develop, minimal rainfall amounts are anticipated with
a trace to maybe a few hundreths of an inch.
Tuesday and Wednesday will be the warmest days of the week with
highs climbing into the upper 70s to low 80s across the region.
These temperatures are 5 to 10 degrees above the climatological
normal for the middle of May.
The next potential for convection appears to center around Wednesday
and Thursday as a northern stream trough tracks southeast into the
northern Plains and Upper Midwest. Confidence at this range remain
rather low at this time, however, will continue to monitor with
Beyond Thursday, a weak Canadian cold front will track south
across the forecast area on Friday with surface high pressure
building in behind it. Somewhat cooler temperatures are
anticipated on Friday though climbing back into the well-above
normal range by next Saturday.
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 616 PM CDT Sat May 13 2023
MVFR/local IFR/LIFR in scattered showers and low ceilings will
continue across nrn Nebraska this evening. This flight concern is
expected to spread south to near Interstate 80 tonight and remain
in place throughout the day Sunday. Flight conditions during this
time across nrn Nebraska will also likely lower to IFR/local LIFR
in low or very low ceilings and VSBYS. MVFR/IFR ceilings are
expected along I-80 Sunday.
Area Forecast Discussion
National Weather Service Newport/Morehead City NC
1000 PM EDT Sat May 13 2023
A cold front will begin to move south across the area tonight,
then clear the southern coast by tomorrow afternoon. Several
more cold fronts will cross the area over the upcoming week.
.NEAR TERM /OVERNIGHT/...
As of 10 PM Sat... Made some changes to the forecast on this update
given latest radar trends and current environment around the
area. The previously mentioned front continues to near the VA/NC
border this evening with a line of rain and isolated
thunderstorms just out ahead of this front. Latest 00Z sounding
shows we are rather dry through the mid levels with mid level
RH`s sitting at 36% and low level RH`s only up to 63% this
evening despite over 1 inch PWAT`s. On top of this, latest
analysis via the RAP shows instability remains off to the west
of the CWA this evening with just about the entire area sitting
on less the 100 J/kg of MUCAPE. This will likely continue to
inhibit thunderstorm activity around the area and also make it a
bit harder for any approaching shower activity to reach the
ground as well. As a result I have scaled back PoP`s and left
them at SChc to Chc probabilities (20-50%) and took thunder out
of the forecast for our northern zones. Made little in the way
of changes with temps and dewpoints as those seem to be tracking
Although Tds will continue to slowly climb through this evening
as moisture pools along the front, the loss of heating will
offset any potential destabilization across the area. Thus, the
expectation (and the signal from most CAMs) is for the cluster
of showers and isolated thunderstorms to quickly begin to
collapse after crossing into NC. The best potential for any
shower activity will be across areas north of Highway 64 when
activity will be at its strongest, otherwise activity will
gradually fall apart as it pushes south. The front should
provide just enough low-level convergence to promote a continued
risk of widely scattered showers overnight as it continues
south. Still, lowered PoPs further across the CWA tonight.
The increase in dew points means a muggy night is in store with
lows in the mid 60s, upper 60s along the coast.
.SHORT TERM /SUNDAY/...
As of 325 PM Sat...Front will gradually cross the region
tomorrow morning, although its speed is somewhat in question.
Our forecast incorporates a general blend of hi-res models with
less weight on the NAM, which shows a front driven across more
quickly by outflow - unlikely with our currently poor
instability profiles. By the afternoon, the front will be mostly
across the area although potentially getting hung up along the
coast, putting most of the area under cooler and drier
northeasterly flow. Most areas will be dry, but some weak
convergence along the stalled front could bring a few showers
along the coast. Once again, instability will be hard to come by
and opted to keep any thunder mention out of the grids.
.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
As of 300 AM Saturday...An anomalously strong upper level ridge is
forecast to develop over the central and western US this week, with
troughing over the eastern US. This will lead to a dominant NW flow
pattern aloft over the Mid-Atlantic States/Carolinas. Models
continue to advertise several shortwaves moving through embedded
within the NW flow, but they continue to differ on the timing,
strength, and amount of moisture available. The key "Long Term"
takeaway, then, is a continued lower confidence forecast through the
upcoming week. Late in the week, the upper level ridge begins to
flatten, with more of a zonal flow developing across the Carolinas.
Once again, though, still a lower confidence forecast thanks to the
continued potential for waves embedded within the flow to traverse
In light of the above, what we know is that strong ridging will be
in place to our west and northwest. From a pattern recognition
standpoint, this may tend to favor drier weather locally, with the
better moisture and instability residing just to our southwest and
south. That said, the risk of showers isn`t completely off the
table. Perhaps the best chance is with a potent wave dropping
southeast through the area on Monday. That wave, in particular, is
forecast to have a decent, but compact, plume of moisture with it,
supporting a better chance of showers compared to some of the
subsequent waves through mid-week. By late in the week, better
moisture may begin to creep north beneath the developing zonal flow
aloft, with a modest increase in the risk of showers and
Temperatures will fluctuate some with each wave, but the general
theme is near normal temps for much of the upcoming week. The
exception, though, is Monday, as low-level thicknesses briefly fall
below normal in tandem with showers and mostly cloudy skies. Based
on this, I leaned a bit more towards the 25th-50th percentile of
guidance to reflect the potential of "cooler" conditions.
.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
SHORT TERM /Through Sunday/...
As of 10 PM Sat... Biggest change was to take any thunder
mention out of the TAF`s this evening as the environment is
unsupportive of thunderstorm development. Otherwise the previous
forecast thinking continues to hold.
Prev Disc...Currently have VFR conditions across all
terminals this evening as of this update. This however will
likely be disrupted by a S`ward moving cold front tonight which
will bring the threat for bringing scattered showers across the
region. Left SHRA down at the southern terminals
given the expectation that any activity that makes it this far
could produce some brief sprinkles.
Cigs gradually fall through tonight, with MVFR ceilings getting
to the N`rn terminals around 8/9Z and to the southern terminals
around 12Z SUnday. A brief period of IFR is possible across
PGV/ISO between 10-12Z however, after 12z all terminals should
be MVFR at the lowest as the area begins to mix after daybreak.
MVFR cigs then continue through the morning and into the
afternoon with skies returning to VFR and clearing from N to S
Sunday afternoon. Winds remain rather light through the period
but do shift from the SW to NE tonight into SUnday morning as
the front pushes through.
LONG TERM /Sunday night through Wednesday/...
As of 300 AM Saturday...Sub-VFR conditions may continue into Sunday
along a southward-advancing cold front. The front will continue to
be accompanied by SCT SHRA and isolated TSRA, especially in the
vicinity of KOAJ and KEWN. Another front will move through on
Monday, accompanied by another risk of SHRA and lower CIGs. Gusty
winds will accompany both fronts as well.
SHORT TERM /through Sunday/...
As of 340 PM Sat...Very quiet conditions over the waters this
afternoon as Bermuda high continues to influence the weather.
Southwesterly to south winds at around 10-15 kt are keeping seas
at around 1-2 feet. Like yesterday, expecting an uptick in winds
late this afternoon into the evening with the thermal gradient,
enhanced further by a front approaching from the north. A few
gusts to 25 kt are not out of the question for the sounds and
northern offshore waters, but not enough to warrant any
headlines this package.
Front gradually crosses the waters tomorrow with a north to
northeasterly surge of winds up to 15-20 kt and continued
infrequent gusts to 25 kt, driving seas up to 3-5 feet across
northern and central waters. Exception will be across the
western waters of Onslow Bay where the front will get hung up.
Winds here will remain relatively light with seas still around
Widely scattered showers possible overnight. Tomorrow, some
more activity could fire for outer portions of southern waters
along the stalled frontal boundary.
LONG TERM /Sunday night through Wednesday/...
As of 300 AM Saturday...A series of upper level waves and associated
cold fronts will traverse area waters through the middle of the
upcoming week. Each front will have a period of gusty winds with it,
with marginal SCA conditions. This may especially be the case with a
potent wave moving through on Monday. If confidence in 25kt winds
increases, a SCA would eventually be needed. Each front will have a
risk of showers with it as well, especially on Monday. During this
time, seas will generally be 3-5 ft.
The KMHX WSR-88D radar in Newport, NC remains down for
scheduled maintenance, and will be down for around another
week for an important upgrade. During the downtime, adjacent
radars will be available, including: KAKQ, KLTX, and KRAX.
Area Forecast Discussion...UPDATED
National Weather Service Morristown TN
1012 PM EDT Sat May 13 2023
Issued at 954 PM EDT Sat May 13 2023
Convection has died down across the CWA this evening, but regional
radar mosaics shows a line of scattered showers and thunderstorms
moving south through eastern Kentucky. CAM guidance hasn`t handled
this extremely well, but there are indications some residual
convection may move in overnight. Didn`t erase PoPs but did, in
the next few hours, bring them in line with radar trends.
Otherwise, no noteworthy chances for the evening update. Still
have a low degree of confidence with how widespread fog will be
tonight given incoming high clouds and covective debris.
(This evening through Sunday)
Issued at 315 PM EDT Sat May 13 2023
1. A few isolated showers and storms this evening and overnight
but most areas dry.
2. Patchy fog again tonight, some areas could be locally dense.
3. Isolated showers and storms again on Sunday.
High pressure remains to our south and our region remains on the
northern periphery of the high with weak northwest flow aloft. With
weakened heights aloft, a few isolated showers and storms are
expected this evening and into the overnight hours. However, most
areas will stay dry. Patchy fog expected again overnight, especially
for any areas that receive rain this evening.
Low confidence forecast for Sunday. The HRRR shows a decaying MCS
moving northwest to southeast through middle KY and middle TN early
tomorrow morning that may impact our southern areas. The other CAMS
arne`t showing this solution so confidence is low but I at least
wanted to mention it as a possibility. If the MCS does materialize
it should be falling apart as it moves into our area. The biggest
impact, if it occurs, will be the high clouds associated with this
complex. High clouds would likely affect/delay any Sunday afternoon
convection due to cooler temperatures in place which would result in
lower instability. With or without the MCS, there will likely be at
least some isolated convection tomorrow but when and where is still
to be determined.
(Sunday night through next Saturday)
Issued at 315 PM EDT Sat May 13 2023
1. Scattered to numerous showers and thunderstorms Monday. The day
with the best chance of precipitation in the extended.
2. Temperatures above normal Monday, then cooling back to near
normal mid to late week with lower rain chances Tuesday through
3. Increasing rain chances Friday and Saturday.
A cold front will still be in the vicinity Sunday evening with
scattered showers and a few thunderstorms lingering. If a convective
complex developing over the Illinois area tonight continues its
journey southwest tonight and early Sunday and makes it into central
Tennessee some thunderstorm redevelopment Sunday afternoon could
affect the plateau and southern valley through early Sunday evening.
Late Sunday night and into Monday shortwaves moving southeast in NW
flow pattern are expected to keep the chance of showers high
overnight Sunday night in the northeast part of the region and be a
focus for more convection during the day Monday. I will continue to
forecast high rain chances southern and eastern sections Monday. The
risk for severe thunderstorms will be low later Monday with the
frontal system across the southern part of TN the higher instability
will be to the south. Some brief heavy rainfall possible during the
afternoon and evening Monday. Highs Monday will be cooler due to
clouds and precipitation in the 70s to around 80.
Monday night through Wednesday models still want to keep some
moisture moving through the area as upper trough digs southward
through the eastern third of the country. Shortwave energy will
trigger more showers and possible a few thunderstorms. WIll have to
keep slight chance showers and storms Tuesday with drier conditions
Wednesday with only a chance of precipitation in the south.
Wednesday looks to be the driest day of the extended. By Thursday or
Friday a more southerly low level flow returns as surface high
pressure shifts east and increasing moisture and higher rain chances
are needed within longwave upper troughing across the Eastern
states. This next system will bring a cold front across the
Mississippi Valley Friday with a cold front moving into east
Tennessee Saturday. Temperatures will be near normal with highs mid
70s to lower 80s Tuesday through Saturday.
Issued at 747 PM EDT Sat May 13 2023
A few ISOLD SHRA may persist INVOF KTYS through 02z or so.
Otherwise, will carry dry conditions at all terminals. Main
concern is likelihood of overnight fog development and impacts.
A lot of high clouds seem poised to move into the region from the
northwest overnight. This combined with higher temp/dewpoint
spreads seem to indicate fog will be a little more tame than last
night. Toned back the fog just a tad in the forecast as a result.
Have all sites VFR by 14z-16z, with SCT-BKN050 clouds by midday or
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 83 66 87 65 / 40 10 30 30
Knoxville McGhee Tyson Airport, TN 82 64 85 63 / 40 20 40 40
Oak Ridge, TN 83 63 85 63 / 30 20 40 40
Tri Cities Airport, TN 79 62 80 59 / 40 20 40 50
Area Forecast Discussion
National Weather Service Phoenix AZ
405 PM MST Sat May 13 2023
The warming trend will continue through the weekend with daytime
highs approaching or exceeding 100 degrees across the lower deserts.
Increasing moisture heading into early next week will lead to daily
chances for showers and isolated thunderstorms across the Arizona
high terrain north and east of Phoenix. Chances will be much lower
across the lower deserts including the Phoenix area. The main risks
with any thunderstorms will be gusty winds and lightning.
Latest satellite imagery resembles what we might expect in late June
with isolated convection firing across the Mogollon Rim and higher
peaks of the lower deserts. Surface dewpoints are generally in the
lower 30s and while this is higher than this time yesterday, the
lower-levels remain much too dry for convection or other
thunderstorm impacts in the short-term. However, latest model
ensembles continue to suggest a highly unusual pattern developing
over the next few days, which will provide us with a sneak peak of
what’s to come this summer.
Latest RAP streamline analysis reveals an elongated cyclonic
circulation extending northward from the Baja Peninsula into the
northern Rockies. A vort max is also evident across central Arizona,
which is associated with cooler temperatures aloft and relatively
steep lapse rates across northern Arizona. Latest runs of the HRRR
indicate the ongoing convection across northern Arizona will drift
northward this afternoon and this evening. Overnight, additional
activity is expected to develop across western New Mexico, which
will likely produce a westward propagating outflow boundary. Several
CAMs suggest this boundary will sweep through central Arizona early
Sunday morning, transporting additional low-level moisture into the
lower deserts. This will consequently enhance MUCAPE which will be
sufficient for isolated storms across the higher terrain east of
Phoenix Sunday afternoon. Although storms remain unlikely across the
Valley, there is a 40 percent chance a gust front emanating from
these storms will reach the Phoenix area, resulting in the potential
for wind gusts of 30-50 mph.
There is considerable uncertainty regarding the evolution of the
pattern across the western CONUS through next week. Nevertheless,
the presence of the lingering albeit weak cyclonic circulation and
the trend of increasing and anomalously high PWATs will provide
favorable conditions for isolated thunderstorms and associated
hazards including dry lightning and strong winds. This will be most
pronounced across the higher terrain north and east of Phoenix, and
across the lower deserts including Phoenix, outflow boundaries
containing strong winds and possibly blowing dust will remain a
threat through much of next week. Meanwhile, the relatively humid
conditions will also result in above normal overnight temperatures
through the week and the latest NBM indicates near record values
.AVIATION...Updated at 2300Z.
South-Central Arizona including KPHX, KIWA, KSDL, KDVT:
Winds Sunday will be the greatest weather issue with occasional
mid/high cloud decks drifting over terminals. The typical overnight
shift to easterly should occur slightly earlier than usual with the
pattern favorable for enhanced speeds topping the nocturnal
inversion. While this will likely remain below LLWS criteria,
abnormal mixing and gusts 15-25kt may materialize as early as near
sunrise with odds increasing through mid morning. Confidence in wind
directions become very low later Sunday afternoon and evening as the
tendency to switch to westerly fights a pressure gradient favoring a
SE component. TSRA over the mountains well east of terminals may
also send outflow boundaries and abrupt wind shifts into the Phoenix
area Sunday evening.
Southeast California/Southwest Arizona including KIPL and KBLH:
No major weather issues will exist through Sunday evening under
mostly clear skies. North winds should generally transition to
westerly this evening, however confidence is good that a modified
Gulf surge will quickly shift directions to S/SE prior to sunrise.
This southerly component should be maintained throughout Sunday with
some chance of afternoon gustiness up to 20kt.
A warming trend will continue through this weekend with high
temperatures approaching or exceeding 100 degrees this weekend
across the lower deserts. Above normal temperatures will persist
into early next week before gradually cooling heading into the
latter half of the week. Winds will overall remain light, but there
will be an uptick in afternoon breeziness this weekend. Anomalous
amounts of moisture will push into the area by Sunday and will lead
to daily chances for showers and isolated thunderstorms (20-40%)
across the southern Gila County high terrain each afternoon. Chances
across the lower elevations are expected to remain low (~20% or
less). The primary threats with thunderstorms will be strong,
erratic winds and dry lightning.
.HYDROLOGY...Updated 455 AM MST 5/11/2023
GILA: Ongoing releases above 3000 cfs from Painted Rock Dam continue
to travel down the Gila River through Yuma County. These releases
will continue to impact unbridged crossings with multiple roads
reportedly closed due to flooding. The latest USGS gauge observation
along the Gila River near Dateland continues to report a depth just
over 9 feet, which is just above minor flood stage. Further
downstream, another USGS gauge near Dome shows a depth of 22.2 feet,
which is above action stage (20 feet). Flood Warnings remain in
effect along the Gila River between Painted Rock Dam and the
Colorado River through at least May 16th.
Area Forecast Discussion
National Weather Service Sacramento CA
332 PM PDT Sat May 13 2023
Dry and warm conditions this weekend. Isolated afternoon mountain
thunderstorm chances develop on Sunday and late next week. Warm
temperatures will continue the next week.
Today will be the warmest day over the next several days.
Temperatures will be topping out in the 90s for the central valley
with the warmest temperatures up to the upper 90s over parts of the
central and northern Sacramento valley. North to east winds will
continue through Sunday morning for some areas with local gusts
over the northeast foothills up to 35 mph and up to 20 mph for
mainly most of the western portions of the Sacramento valley.
Low pressure area currently located over eastern Nevada/western
Utah will retrograde westward towards northern California. The low
will help to bring a cooling trend although temperatures will
remain above normal. It will also bring a chance for some
afternoon and evening thunderstorms over parts of the region. For
now the best chances are mainly above 3000 feet for the Sierra
Nevada but have extended chances northward over Shasta County.
Best timing should be between 3 pm and 9 pm. Profiles look more
like thunderstorms will produce hail and gusty winds. Would not be
surprised to see an isolated storm produce some large hail on
Sunday. The HRRR does bring an isolated storm into the north end
of the valley Sunday evening but all other models are keeping that
area dry. For now have less than 10 percent chances for that area
but as the low moves towards us that could change. Models do seem
to favor the northern mountains for activity Sunday evening as
the center of the low drifts northward.
As the low moves northward into Oregon for Monday the area will
dry out and high pressure will build over the area on Tuesday
warming valley temperatures back up into the 90s. Monday will be a
transition day with highs near Sunday`s highs.
.EXTENDED DISCUSSION (Wednesday THROUGH Saturday)...
High pressure extends over interior NorCal through the extended
forecast period and into Canada. This is supported by cluster
analyst as deterministic models differ with subtle features that
far out. This will result in continued above normal high
temperatures Tuesday through Friday with upper 80s to mid 90s in
the Central Valley. Slight chance of afternoon showers or
thunderstorms over higher elevations of the Sierra Nevada Friday
and Saturday for now but that will depend on where the high
pressure centers over the west.
VFR conditions over interior NorCal next 24 hrs. In Sac Vly, areas
Nly sfc wind gusts to 25 kts possible til 03z Sun. In
foothills/mtns, lcl NE-E sfc wind gusts up to 30 kts.
Area Forecast Discussion
National Weather Service Tucson AZ
228 PM MST Sat May 13 2023
.SYNOPSIS...A broad and steady moisture increase from the east will
bring increasing chances of showers and thunderstorms Sunday through
most of the coming week. Strong gusty outflows from some storms will
lead to erratic wind conditions at times.
.DISCUSSION...Slowly but surely moisture is very gradually increasing
across Arizona with an upper low extending down into the western part
of the state. This environment has already resulted in thunderstorms
developing all along and just north of the Mogollon Rim with
movement to the north in the upper level southerly flow present at
the moment. At the surface, easterly flow is just beginning to nudge
over the AZ/NM border although the dewpoints are struggling as drier
air aloft is mixing out the surface moisture at this point.
That changes overnight tonight into Sunday as the flow aloft becomes
southeasterly and the easterly low level flow strengthens resulting
in more moisture streaming westward into Arizona. By Sunday afternoon
that easterly flow looks to punch as far west as central Pinal,
eastern Pima (west of Tucson) and Santa Cruz counties. This boundary
should set up a point of focus for convection in that area during the
afternoon and evening hours favoring higher terrain, at least
initially. The various CAM solutions including the HRRR point to that
scenario. Running with that idea, dewpoints, while elevated will not
be that high this far west Sunday meaning rainfall isn`t expected to
be heavy with dry lightning a good bet outside of immediate
thunderstorm cores. The other issue with this setup is DCAPE should
be on the high side with strong outflow winds a good bet. HREF notes
a 70% or better likelihood of greater than 30kt outflows in the above
mentioned area. The more vigorous convection will die off into the
evening hours with only a few light showers lingering well into the
A similar setup remains across the area Monday with the moisture
likely being a bit further west. Our Pop grids follow that thought.
By Tuesday the weak upper low consolidates west of Baja maintaining
the easterly/southeasterly flow of moisture through Wednesday or
potentially Thursday. Then, this feature looks to gradually move
north and/or east and at this point there are differences in the
various models. Main difference relates to when the moisture feed is
shut down but it looks like it could remain into the early part of
next weekend. In the meantime, we get to "enjoy" an early taste of
monsoon-like (not a monsoon pattern) weather.
.AVIATION...Valid through 15/00Z.
SCT to locally BKN mid clouds near 14k-18k ft MSL this afternoon
will diminish this evening with an isolated -SHRA/-TSRA near the NM
border area until 14/03Z. Mid level clouds 12k-16k ft MSL developing
again after 14/18Z with SCT -SHRA/-TSRA developing after 14/20Z from
the KTUS/KOLS area eastward. Light winds generally from a westerly
direction into this evening will become east-southeast overnight at
8-15 kts and increasing to 18-22 kts toward dawn across areas that
favor an easterly wind. Easterly winds will remain through Sunday
from KTUS eastward with light westerly winds west of KTUS.
Thunderstorms could produce strong outflow winds Sunday afternoon and
evening. Aviation discussion not updated for TAF amendments.
.FIRE WEATHER...Moisture will spread across southeast Arizona from
the east tonight through the end of next week. This will lead to
scattered showers and thunderstorms each afternoon/evening starting
Sunday. The main threats will be strong, gusty and erratic outflow
winds and lightning strikes causing new fire starts. Initially,
thunderstorms further west from the NM border will likely be mostly
dry except directly under rather small rain cores Sunday with storms
as far west as eastern Pima and Pinal counties. Then Monday into the
rest of the week storms will have a better chance of producing
some rainfall, however dry lightning around the edges of the storms
is a decent bet although humidity levels will be higher. Sunday
through much of the coming week winds will be from the east to
southeast at least as far west as Tucson with more variable and at
times westerly afternoon winds west of Tucson. The moist pattern with
scattered afternoon showers and storms looks to linger through the
coming workweek and possibly into the early part of next weekend.
.CLIMATE...Here is a listing of individual station normal rainfall
amounts for May.
Picacho Peak 0.22"
Sierra Vista 0.20"
San Simon 0.12"
Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson