Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 06/21/23
Area Forecast Discussion...UPDATED
National Weather Service Amarillo TX
554 PM CDT Tue Jun 20 2023
...New AVIATION...
.SHORT TERM ...
(This evening through Wednesday night)
Issued at 233 PM CDT Tue Jun 20 2023
While hot weather has arrive to the Oklahoma and Texas Panhandles,
additional thunderstorms may occur both of the next two days, with
Wednesday bringing a highly conditional chance for severe storms to
the eastern two thirds of the area.
This afternoon into this evening, as the upper ridge continues to
try to dominate proceedings, guidance suggests a shortwave will
traverse the northern side of this feature and pass over the
Panhandles. While surface dewpoints have dropped in the western
Panhandles behind a dryline, enough mid-level moisture is present
for guidance to continue to hint at the presence of 100-300 J/kg of
high-based CAPE. Have thus introduced 10 PoP mentions of
thunderstorms into the southern Texas Panhandle this evening. Given
the deep surface mixed layer, these thunderstorms may be nearly or
completely dry and also pose a risk for a stray severe wind gust.
Given the continued presence of the dryline, a recurrence of fog is
possible in the eastern Panhandles Wednesday morning as additional
moist advection occurs. Have thus introduced patchy fog mentions
in our east.
Tomorrow, while the upper ridge remains present, moisture and
potential instability in the eastern Panhandles continue to build,
with guidance suggesting perhaps 5000-6000 J/kg of MLCAPE will be
present by the late afternoon. With 0-6km bulk shear of 50 knots
likely present by the late afternoon as well, any thunderstorm that
develops is likely to become severe. The big remaining question is
whether or not the cap will break, as upper support may be lacking.
Have thus tried to keep mentions of thunderstorms over a large area
but limit them to a slight chance.
Ferguson
&&
.LONG TERM ...
(Thursday through next Monday)
Issued at 233 PM CDT Tue Jun 20 2023
Overview:
A persistent mid to upper level ridge over the south-
central US will continue to bring hot temperatures to much of
Texas into Mexico. This ridge will also continue to supply very
warm temperatures to the FA, especially the Texas Panhandle. The
ridge is expected to be suppressed just enough on Thu and Fri to
bring daytime highs back into the upper 80s and lower 90s. The
chance for some thunderstorms with perturbations in the ridge Thu
and Fri will help with the cooler temperatures as well. Severe
thunderstorms cannot be ruled out at this time. Going into Sat,
temperatures are progged to rebound back into the upper 90s with
some areas seeing triple digit temperatures once again. Sunday,
northern portions of the FA may see temps cool back into the upper
80s and lower 90s once again.
Additional Details:
Depending on the speed and nature of a shortwave(s) moving through
Thu night some showers and thunderstorms could still be present
somewhere in the FA through much of the day on Thu. Mainly in the
northeastern combined Panhandles. An additional shortwave is
progged to move through Thu night bringing scattered thunderstorms
once again to the area into Friday morning.
Thursday, additional moisture advection is progged to take place
with a dryline retreating west into eastern NM with southeast
winds feeding 60 Tds into the entire combined Panhandles. H7
theta-e advection looks quite nice for Thursday especially in the
eastern half of the FA. Depending on daytime heating and the
timing of additional shortwaves in the ridge, some afternoon
discrete storms will be possible, mainly in the western combined
Panhandles along the dryline. If discrete storms can get going
before the evening, they are expected to have a chance to tap into
some uncapped SBCAPE upwards of 3000-4000 J/Kg accompanied by
30-40kts of bulk shear. During the afternoon these storms will
have the potential to become severe. The RAP favors the western
OK Panhandle while the NAM favors the southwestern TX Panhandle
for small period of uncapped CAPE. Have stayed with the NBM PoPs
for now which could be a bit on the low side, especially during
the overnight period. During the overnight confidence in storms
being severe is not as high, but cannot not rule out the
possibility of a severe threat overnight. Confidence in the
overall tor threat for Thu is not high, but cannot completely
rule out one or two sometime Thu afternoon into the early
overnight hours.
For Friday, the ridge quiets down with all the perturbations, and
with slightly cooler temperatures expected, the probability for
thunderstorms drops below 15. There will still be plenty of
moisture across the majority of the Panhandles with Tds in the mid
to upper 60s with the possibility of a dryline across the area
once again. The environment on Friday is expected to be capped.
If something changes though, and some lift can be realized on
Friday afternoon an isolated severe thunderstorm may be possible,
although is looking unlikely at this time.
Saturday the ridge gains some strength again with the possibility
of triple digit temperatures for areas in the Canadian River
Valley and Palo Duro Canyon. Some guidance suggest that PDC may
need a Heat Advisory again on Saturday with a high around 105-106.
Late Saturday an H5 low is progged to move across the northern
Great Plains. This system may even send a very weak front
southward into the FA for Sun. Surface winds are progged to become
northerly with daytime highs across the area being suppressed a
bit. The northern combined Panhandles are progged to only reach
the upper 80s while the southern portion of the FA still gets into
the mid to upper 90s.
36
&&
.AVIATION...
(00Z TAFS)
Issued at 548 PM CDT Tue Jun 20 2023
Winds are expected to decrease to around 10 knots or less with the
setting sun. There could be a few showers around AMA this evening
that could cause some gusty winds to around 40 knots or greater.
Fog will be possible mainly east of a GUY to AMA line. At this
point it looks like any fog that would reduce the visibility to
less than 6 miles will stay east of the TAF sites. However, the
best surface convergence and potential low clouds or fog would
probably be near GUY. Southwest winds around 10 knots are expected
to prevail at DHT and AMA during the day on Wednesday. Winds are
expected to be easterly at GUY as this location will be north of
the surface low.
&&
.PRELIMINARY POINT TEMPS/POPS...
Amarillo TX 68 98 66 88 / 10 20 20 20
Beaver OK 69 90 66 83 / 10 20 30 30
Boise City OK 62 93 62 84 / 10 10 20 30
Borger TX 69 100 68 90 / 10 20 20 20
Boys Ranch TX 65 100 66 92 / 10 10 20 20
Canyon TX 68 100 66 90 / 10 20 20 20
Clarendon TX 70 98 65 87 / 10 20 30 10
Dalhart TX 61 97 62 88 / 10 10 20 30
Guymon OK 65 94 64 84 / 10 20 30 30
Hereford TX 68 101 66 93 / 10 10 10 20
Lipscomb TX 70 94 64 84 / 10 30 30 20
Pampa TX 69 95 65 86 / 10 20 20 20
Shamrock TX 71 96 66 87 / 10 30 30 20
Wellington TX 73 98 68 89 / 10 30 40 20
&&
.AMA WATCHES/WARNINGS/ADVISORIES...
TX...Heat Advisory until 8 PM CDT this evening for TXZ317.
OK...None.
&&
$$
SHORT TERM...77
LONG TERM....36
AVIATION...15
Area Forecast Discussion
National Weather Service Denver/Boulder CO
848 PM MDT Tue Jun 20 2023
.UPDATE...
Issued at 844 PM MDT Tue Jun 20 2023
HiRes models this evening showing some increase in low clouds
across the plains overnight, as well as some fog primarily to the
east and northeast of Denver. Consequently, I have increase the
cloud cover in those areas to account for the stratus, and added
patchy fog in those grids as well.
UPDATE Issued at 642 PM MDT Tue Jun 20 2023
There is very little adjustment needed for the grids this evening.
I adjusted the pops over Washington County to better match the
radar coverage, which is isolated this time. It should die off
later this evening.
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 302 PM MDT Tue Jun 20 2023
Northeast Colorado will remain between broad troughing to the
northwest and ridging to the south and southeast, with persistent
and increasing southwesterly to southerly flow aloft.
We maintain our Flood Advisories for the South Platte and Cache
La Poudre Rivers (basically from the western edge of Weld County
east almost to Sedgwick) and the Colorado River (between Willow
Creek and Little Muddy Creek) Hydrographs, of both gauge
observations and forecast by MBRFC, show action stage for many of
our points along the Advisory area, and are forecast to remain
so.
Tonight, partly cloudy to mostly clear and dry with near normal
overnight low temperatures, in the 50s across the plains and
mostly 30s and 40s across the high country.
Tomorrow, mostly clear (west) to partly cloudy (east) and dry
through much of the day. High temperatures are also forecast near
normal, in the 80s across the plains and mostly 50s and 70s across
the high country.
There is significant uncertainty regarding the intensity and
coverage of convection tomorrow afternoon and evening. There will
be great moisture in place again across the plains again by
tomorrow afternoon, with dew points in the 40s to 60s (some models
have 70s but that seems excessive) on a gradient southwest to
northeast. There should be good heating allowing instability to
build through the day; models have a good swatch of MLCAPE over
the eastern plains, from a reasonable 1500 to 2500 J/kg up to 3500
to 4500 J/kg in the very aggressive (NAM). Models also show good
bulk shear between brisk southeasterly surface flow and
southwesterly flow aloft, widespread 20 to 40 knots and areas of
40 to 60 knots by late afternoon. Regardless of exact details, we
expect the ingredients moisture, instability, and shear to be
present by late afternoon, but there is a question of
lift/forcing. There may be something of a weak disturbance in the
flow aloft but no real wave. We do expect a front but it looks
rather weak and its passage timing remains uncertain, and there is
a range of possible scenarios. If the front comes through early
(say, midday or so), then there won`t be enough time to build
serious instability, the forcing won`t coincide with the best
shear, and intensity and coverage will suffer (however, some
convection would still occur and it would be pushed farther west
and south toward greater population centers). If it comes through
around mid afternoon, we will likely get a rather typical
convective day (just frontally rather than terrain forced). If it
comes through late in the afternoon then we could have a
significant event, with multiple supercells producing all severe
hazards and heavy rainfall resulting in flooding hazards through
the evening into the night. SPC has included most of our plains in
a slight risk with probabilities of all hazards. I would be
surprised if we do not issue a watch tomorrow. More details in
the long term discussion below.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 302 PM MDT Tue Jun 20 2023
Key Messages:
Severe storms possible Wed night for the plains.
Uncertainty lingers thus two scenarios are presented.
A few updates to the long-term package includes a batch of severe
storms mainly for the eastern plains Wednesday night. Increasing
southeasterly flow reaching 35-45kts at 500-700mb will bring
moisture around the front side of an upper level low.
Northeastern Colorado sits between the edge of an upper level
ridge and an incoming trough axis which steer increasing pressure
gradients. Although upper level forcing is lacking, this provides
a low level jet to increase low level winds. The combination of
MUCAPE values across the HRRR/HREF at 1000-2000 J/kg, 0-6km bulk
shear near 30- 35kts and deepen hail growth zone shown on multiple
BUFKIT soundings give higher confidence in the development of
severe storms. Strong day time heat will allow de-stabilization
leading to a favorable environment for thunderstorm development
across the I-25 corridor to the plains. The question becomes when
and where Wednesday evening?
CAMs display a line of severe storms stretching east of Greeley
to Julesburg tracking down to southern Washington County. Would
rely on two different scenarios for Wednesday evening into
Thursday morning outcome.
-Scenario A (A most likely solution)-
Early Wednesday evening scattered showers and storms from
southeastern Wyoming will enter the plains mainly east of Greeley
producing severe hail, strong wind gusts up to 60 mph, and brief
heavy rainfall. These storms could combine with earlier convection
across our foothills becoming stronger. LCLs remain low and low
level winds support a possible isolated tornado. This line will
weaken before midnight leaving weak rain showers along the
Colorado/Kansas border. Areas that have received large amounts of
rainfall recently across the plains are at risk for river flooding
and flooded roadways.
(Note: There is hesitation on using quite a few supercell
parameters because even currently, the NAM and HRRR 18Z supercell
composite runs have high probability values of supercells across
the eastern plains but partly cloudy skies remain across current
METARs.)
-Scenario B (A low probability solution)-
Early Wednesday evening becomes too stable after multiple
boundaries produce storms too early in the afternoon. The severe
threat ends but showers could still pose a flood risk to rivers.
Either way, skies will remain cloudy through Thursday morning. This
will keep our lows overnight near mid 50s for the plains and low 40s
for the mountains. To add more to this complicated forecast,
instability sticks around across the region Thursday morning and
afternoon which could lead to additional scattered to numerous
showers and storms across the mountains, foothills and I-25. MLCAPE
values near 400-600 J/kg exists throughout these areas above. As
storms move east off the foothills, they could struggle.
Thunderstorms development and sustainment will depend heavily on how
much cloud cover remains across the plains and urban corridor
through Thursday afternoon. Without heating, storms and showers may
become stratiform. A shortwave will occur by Friday which could
bring one more round of weak showers and storms across the region.
Large differences in the NAM/GFS in terms of thunderstorm
formation Friday afternoon with the GFS being the drier solution.
Both direction shear and speed are favorable for our region along
with mid-level lapse rates near 8 C/km. With these factors in
mind, will keep weak isolated to scattered showers over the region
for now starting early Friday afternoon. This weekend, drier air
enters our CWA as upper levels shift into a ridge pattern. Warmer
temperatures continue for all areas.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 642 PM MDT Tue Jun 20 2023
VFR through 21z Wednesday, with southeast winds 8-13 kts
transitioning to a south/southwest drainage this evening. Back to
southeast by Wednesday afternoon. I also included a prob30 for
tsra in the terminals at 21z. Timing will be a big issue but
storms expected to develop either in the late afternoon period or
Wednesday evening. Based on low confidence, some adjustments to
the timing regarding the start time of the storm development.
Could see broken ceilings around 5kft AGL with the storms.
&&
.HYDROLOGY...
Issued at 302 PM MDT Tue Jun 20 2023
We maintain our Flood Advisories for the South Platte and Cache
La Poudre Rivers (basically from the western edge of Weld County
east almost to Sedgwick) and the Colorado River (between Willow
Creek and Little Muddy Creek) Hydrographs, of both gauge
observations and forecast by MBRFC, show action stage for many of
our points along the Advisory area, and are forecast to remain so.
Tomorrow afternoon and evening, there may be a limited threat of
burn area flash flooding east of the continental divide. There is
still significant uncertainty concerning convection and hazards,
but most of the impactful rainfall should occur east of the
divide.
Scattered storms and showers could produce heavy rainfall again,
Thursday afternoon which brings a limited flood threat over the
Cameron Peak burn area.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Cooper
SHORT TERM...EJD
LONG TERM...AD
AVIATION...Cooper
HYDROLOGY...AD/EJD
Area Forecast Discussion
National Weather Service Boston/Norton MA
1013 PM EDT Tue Jun 20 2023
.SYNOPSIS...
Scattered showers mainly across the interior will dissipate this
evening with dry weather overnight. Temperatures will still run
on the cooler end of normal on Wednesday with party sunny skies
and dry weather. An approaching warm front from the south will
bring a few showers Thursday, especially south of the Mass
Pike. Then warm and rather humid conditions prevail from Friday
into early next week. The increasing humidity will be
accompanied by scattered showers and thunderstorms each day.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
1005 PM Update:
Scattered showers from earlier have since dissipated. However
satellite imagery and obs showing developing stratus of varying
coverage, mainly away from Cape Cod. Admittedly the coverage of
cloudiness has been a bit of a challenge in that it is not
being handled by guidance all that well. General indications
from near- term guidance shows stratus expanding in spatial
coverage as the night progresses, especially as sfc winds back a
bit from ESE/E to more of an ENE to NE overnight into the pre-
dawn hrs and to bring slight cooling to the boundary layer. Used
the RAP and today`s 12z HREF to show the increased spatial
extent of stratus. Less certain on cloud cover across Cape Cod
and the Islands but some increase is anticipated here too. Temps
should be a few degrees milder than last night in the mid to
upper 50s.
Previous discussion:
* Scattered showers & perhaps an isolated t-storm across western
MA/CT comes to an end this evening
* Dry & pleasant overnight with lows mainly in the lower-middle 50s
Still some marginal instability across western New Eng with SBCAPES
200-500 J/kg. Widely scattered showers moving south across western
MA/CT and this activity will dissipate this evening as shortwave
moves offshore with warming temps aloft and cooling boundary layer
stabilizing the environment. Perhaps a brief isolated t-storm
next hour or so.
Otherwise...high pressure building south across northern New England
will provide for another cool night for late June standards. The
biggest uncertainty is if/how extensive potential low clouds/fog
patches develop overnight. This needs to be watched though given
subtle moist onshore flow and a cooling boundary layer. Thinking
overnight lows bottom out mainly in the lower to middle 50s...but
some localized upper 40s are possible in the typical low-lying areas
of eastern MA but that will depend on sky conditions.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
Highlights...
* Dry & partly sunny Wed with highs in the lower to middle 70s
except 65 to 70 on portions of the very immediate coast
* Dry & cool again Wed night with lows mainly lower-middle 50s but
some patchy ground fog may develop late
Details...
Wednesday...
High pressure will be moving just east of our region on Wednesday.
This brings partly sunny skies...but unlike today rising height
fields will prevent any diurnal precipitation and kept the forecast
dry. Despite more sunshine than today...925T are cooler given
persistent easterly flow. Therefore...we expect high temps to reach
the lower to middle 70s across the interior and between 65 and 70
along portions of the very immediate coast.
Wednesday night...
Large high pressure will remain anchored off the coast. We think it
should enough to keep the low pressure and associated rain shield to
our south through daybreak Thursday...but will have to watch the
immediate south coast in case guidance speeds up. Otherwise...high
pressure still in control will result in one more relatively cool
night for late June standards. Overnight low temps should bottom out
mainly in the lower to middle 50s...but some upper 40s are possible
in the normally coolest outlying locations. We will also have to
watch for the formation of patchy ground fog late.
&&
.LONG TERM /THURSDAY THROUGH TUESDAY/...
Highlights...
* Chance of showers Thu. Cool near the coast
* Warmer temperatures and increasing humidity levels Fri into early
next week with scattered showers and thunderstorms each day
Thursday...
Rex block breaks down as ridge shifts to the east over the Maritimes
with closed low remaining across the TN/OH valley. This results in
developing southerly flow aloft with a quicker influx of higher PWAT
air advecting north into SNE. We discounted the NAM which is slowest
of the guidance bringing the deeper moisture northward. PWATs
increase to 1.5-1.75" Thu and this surge of moisture will likely be
accompanied by some showers lifting northward into the region. ECMWF
may be too aggressive but expect at least scattered showers,
especially south of the Mass Pike with lower probs of showers
further to the north. Increasing cloud cover and easterly flow will
result in cooler temps near the coast with temps possibly holding in
the 60s, with 70s further N across interior MA.
Friday through Tuesday...
Rather unsettled pattern sets up for much of this period as slow
moving cutoff low to the west opens up and lifts into New Eng late
in the weekend. Then another amplifying upper trough moves into the
Gt Lakes early next week with deep southerly flow becoming
reinforced across New Eng. The biggest challenge will be timing of
wet weather and extent/magnitude of convection. The increasing
dewpoints and warmer temps will contribute to moderate diurnal
instability developing each day. NBM shows decent probs of CAPES of
1000 J/kg so while we are not expecting widespread rain, expect at
least scattered showers/t-storms developing each day. Axis of
instability is favored across the interior where best chance of
storms will be. Deep layer shear is lacking so risk for organized
severe weather is quite low, but can`t rule out a few strong storms
with pattern favoring a wet microburst if sufficient instability is
generated. CSU machine learning probs and CIPS analogs favor Sat for
best chance of any severe weather but there are low probs into
early next week. Guidance is suggesting increasing wind field
and deep layer shear on Tue ahead of higher amplitude trough so
this will have to be monitored in the days ahead.
Heavy rainfall will be the primary risk this weekend given the
anomalous PWATs and weak flow aloft and CSU machine learning probs
are fairly bullish on excessive rainfall potential on Sat while
still showing low probs Sun/Mon.
There will be a summer feel to the airmass through early next week
as warmer temps and much higher humidity levels move into New Eng.
Highs will generally be upper upper 70s to lower 80s with potential
for mid 80s this weekend in the interior. Uncomfortable humidity
levels will be the the bigger story as an extended period of
dewpoints near 70 is likely from Friday into early next week. Mild
nights with lows in the 60s.
&&
.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
00z TAF Update...
Tonight...Moderate Confidence.
Scattered showers ending early with VFR for much of the
evening. However...cooling boundary layer and calm/light onshore
flow may allow for some MVFR-IFR conditions in low clouds/fog
patches to develop. Timing and areal coverage of them remains to
be seen...but greatest risk near the coast and the Worcester
Hills.
Wednesday...High Confidence.
Any low clouds/fog patches burn off by mid to late Wednesday
morning. Otherwise...VFR with ESE winds 5 to 10 knots.
Wednesday night...High Confidence.
Mainly VFR...but will need to watch for some patchy ground fog
late especially in the typically prone low-lying locations.
Outlook /Thursday through Sunday/...
Thursday: VFR. Slight chance SHRA.
Thursday Night: Mainly VFR, with local IFR possible. Chance
SHRA.
Friday through Friday Night: Mainly VFR, with local IFR
possible. Chance SHRA, isolated TSRA.
Saturday: Mainly VFR, with local MVFR possible. Breezy. Chance
SHRA, isolated TSRA.
Saturday Night: VFR. Breezy. Chance SHRA.
Sunday: Mainly VFR, with local MVFR possible. Chance SHRA,
slight chance TSRA.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Tonight through Wednesday night...High Confidence.
High pressure moving off the southern New England coast combined
with a wave of low pressure developing off the mid-Atlantic states
will generate a persistent ESE wind over the next 36 hours.
Strongest gradient will be southwest of our waters...but did opt to
issue a small craft advisory for our southwest most outer-waters Wed
afternoon and night. This is for some 5 foot seas and we also may
see 20+ knot gusts develop. For the rest of the waters...no
headlines through Wed night but will need to watch for some
overnight/early morning fog at times.
Outlook /Thursday through Sunday/...
Thursday: Winds less than 25 kt. Areas of seas approaching
5 ft. Chance of rain showers.
Thursday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Chance of rain showers.
Friday through Saturday: Winds less than 25 kt. Chance of rain
showers.
Saturday Night through Sunday: Winds less than 25 kt. Seas
locally approaching 5 ft. Chance of rain showers.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 2 PM Wednesday to 8 AM EDT Thursday
for ANZ256.
&&
$$
SYNOPSIS...KJC/Frank
NEAR TERM...KJC/Frank/Loconto
SHORT TERM...Frank
LONG TERM...KJC
AVIATION...KJC/Frank/Loconto
MARINE...KJC/Frank/Loconto
Area Forecast Discussion
National Weather Service Grand Forks ND
1025 PM CDT Tue Jun 20 2023
.UPDATE...
Issued at 1023 PM CDT Tue Jun 20 2023
The thunderstorms have moved north into Manitoba. The severe
tstorm was expired for our NW fcst area at 0230z. Interesting
evening as storms formed initially along the frontal boundary from
west of Langdon to Leeds to near Harvey ND southwest from there
but fizzled out as new storms formed west of the boundary in a
better sheared environment. These storms were mainly just west of
our fcst area. For the overnight will keep some lower pops in for
areas west of the RRV due to collab with other offices and
continuity. Some CAMs indicate a few showers and storms moving
northeast into parts of E ND toward 12z Wed. These would not be
severe.
UPDATE Issued at 656 PM CDT Tue Jun 20 2023
Looking at sfc winds the frontal boundary was from near Windygates
MB to Munich ND (just west of Langdon) to Leeds ND to Esmond ND
then near Harvey to just west of Bismarck. Storms fired along this
boundary and intensified but have since had a bit more trouble
increasing in strength. Very sharp gradient looking at 0-6 km bulk
shear and effective shear from 20 kts near DVL to 50 kts Rugby.
Have noticed a few storms trying to form more northwest of the
boundary in area of higher shear and there is a zone of elevated
instability near 4000 j/kg Rolla area to west of Harvey. some CIN
is noted as well on the SPC mesopage. 850-500 mb flow is north and
not allowing the storms to deviate east and thus paralleling the
frontal boundary. HRRR indicates a bit more activity shifting just
west yet behind the front as the airmass in front of the frontal
boundary remains dry. 850 mb wind covergence is showing south-
southeast 40 kts east of the boundary bumping into 10 kts NW flow
just behind the boundary. So parameters are there for intense
storms to fire along the boundary and just west but missing
ingredient apparently keeping storms for now not as impressive as
one would thought. Wonder if lack of effect shear where storms
fire is an issue as the overlap of shear and instability isnt as
great as is shown on analysis or in CAMs. Anyhow, the next few
hours will keep any storm chance in the same area.
&&
.SHORT TERM...(This evening through Wednesday night)
Issued at 321 PM CDT Tue Jun 20 2023
-Isolated to scattered thunderstorms are possible from late
afternoon through the overnight period tonight primarily over the
Devils Lake Basin. Severe thunderstorms will be possible from the
late afternoon through the evening (5-15% chance for severe
impacts). A 5% probability for severe may linger overnight.
-Scattered showers and thunderstorms are possible again over a
large part of the region Wednesday, with isolated severe
thunderstorms continue to be possible all day Wednesday into the
evening period.
A quasi-stationary front and associated surface trough along our
western CWA should slowly shift east through Wednesday as upper
ridging finally breaks down and S-SW flow aloft becomes more
southwesterly over our CWA. The response will be for increasing
synoptic ascent with embedded PVA in the mid levels. Coverage
initially may be a bigger questions due to stronger capping in the
very hot air mass this afternoon/evening but with increasing ascent
shower/thunderstorm coverage should increase west to east though
details/impacts will vary/evolve. BL Tds in the 62 to 70F range
combined with good mid level moist return is keeping PWATs well over
1.2" (up to 1.6") and heavy rainfall should be expected with storms,
though faster motion lowers residence time and lower coverage keeps
potential for training/flood impacts lower (still could ruled out
minor excessive runoff).
Regarding the severe threat today: Strong/deep shear (effective
shear 35-50kt) and ML CAPE in the 2500-3500 J/KG are already in
place along the frontal zone in our far northwest. Steep mid level
lapse rates should remain in place through tonight (7.5-8.5 C/km)
and this keeps at least elevated instability in the 1500-3000 J/KG
range even after sunset/low level decoupling. Shear does decrease
though as the LLJ weakens, but 0-3km shear may still hold around
30kts raising the potential for lingering down burst wind and
isolated hail threats if thunderstorms continue overnight.
Shallower CU is developing currently, but CAPE may still be holding
for now. Still, as we approach convective temperatures in those areas
RAP/HRRR show initiation occuring closer to 23Z (6PM) when RAP
sounding show the CAP complete eroding. The environment supports
elevated supercell development at least through this evening, with
high mixed layers and strong 0-3km shear (30-45kt) supporting
enhanced wind potential. As it stands one scenario would be the CAP
holds, coverage remains isolated this evening until later in the
night when clustering of cells would be more favored than discrete
cells. The other scenario would be discrete elevated supercells
and mergers with smaller scale clustering and QLCS type features
resulting in higher end and higher coverage of severe impacts.
Severe threat Wednesday: W-SW flow with periods of PVA aloft and the
frontal zone lingering over our area should support ongoing shower
and thunderstorm chances. ML CAPE in the 1500-2000 J/KG and marginal
effective shear less than 30kts lowers confidence in coverage of
severe impacts Wednesday, but there will still be some potential for
isolated severe updrafts through the daytime period into the evening.
.LONG TERM...(Thursday through Tuesday)
Issued at 321 PM CDT Tue Jun 20 2023
-Cooler (but seasonably mild) temperatures arrive Thursday and
continue to be favored into at least the early part of next week.
-An active/unsettled pattern will be in place, with shower and
thunderstorm chances each day into next week. The best chances this
weekend (50-80%). Between these periods there is an increased signal
for beneficial rainfall (1"+) across the region.
-There is a low probability for severe thunderstorms (5%) on
Saturday, otherwise the probably for severe thunderstorms is low.
There is a strong signal in ensembles that the amplified mid level
ridge should break down with falling heights across the northern
Plains, allowing for a progressive westerly flow to develop. This
puts an end to our above normal pattern and seasonably mild
temperatures in the 70s to lower 80s will be favored (some potential
for highs in the 60s dependent on precipitation and clouds). In this
unsettled pattern the active jet stream will allow a series of more
defined shortwave trough passages, however due to the pattern shift
deeper southerly flow may be limited, so local evapotranspiration
will be keep to how high Tds get and thus what kind of instability
will be in place each day. PWATs should at least be within seasonal
ranges 1.0-1.25 which still supports heavy rain where
shower/thunderstorms develop. Details on these waves still varies
will will impact where the more organized periods of precipitation
ultimately set up. the 24hr prob for 1"+ rain from NBM increases
this Saturday-Sunday into the 50-55% range for ND counties highlights
the highest potential for beneficial precipitation.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 656 PM CDT Tue Jun 20 2023
DVL TAF site near the area for potential t-storms this evening,
though looks like more west. But VCTS needed 03z to 07z. Otherwise
mainly clear, few CI in the RRV and east into Wednesday morning.
Chance for a few showers or t-storms does increase Wed aftn into
the RRV. Gusty south winds in the RRV and MN tonight, though not
as strong as during the day. Winds turning northwest behind the
front into DVL.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
&&
$$
UPDATE...Riddle
SHORT TERM...DJR
LONG TERM...DJR
AVIATION...Riddle
Area Forecast Discussion
National Weather Service Gray ME
1026 PM EDT Tue Jun 20 2023
.SYNOPSIS...
A pair of mostly dry days are on the way before yet another low
moves into the region. Increasingly southerly flow will usher
in warmer temperatures and higher humidity by the end of the
week. Afternoon showers and thunderstorms are possible each
afternoon through the weekend with heavy rain at times.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
1025 PM Update...
A couple widely scattered showers per latest radar imagery will
continue to dissipate over the next hour or two. Temperatures
are already falling towards their dew point values, so fog
should begin to develop late this evening and during the
overnight hours. Have made minor edits to the near term
temperatures, dew points and winds.
Prev Update...
A few scattered showers continue early this evening per latest
radar imagery. The latest HRRR has this precipitation continuing
through about sunset which seams reasonable. Otherwise only
minor tweaks to the near term portion of the forecast. Patchy
fog will develop later this evening across the region with
plenty of low level moisture remaining in place.
Prev Disc...
A broad area of high pressure over the region is bolstered by
an incoming upper level ridge, rolling over from the northern
Great Lakes region... a sharpening, east-west oriented trough
axis will still be present over our area, but shower chances
will dwindle as diurnal mixing is lost this evening. The
combination of subsidence from the incoming ridge and high
humidity in the boundary layer will combine for another damp
night with patchy fog and areas of low clouds. A few areas of
lingering mid cloud decks will muddy the location of fog and
stratus tonight, and may make it come-and-go-and-come-again in
some areas, but in general areas most favored for development
are in river valleys... along the coastal plain... and in areas
that see rain today, which paints a pretty wide-spread
smattering across the forecast area. Elevated dew points in the
50s coupled with clouds and boundary layer humidity place low
temperatures in the 50s area-wide.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
Wednesday sees pressure and height rises as the aforementioned
ridge axis stretches across Quebec and into the Canadian
Maritimes... with a surface high pressure center sinking
offshore into the Gulf of Maine. This produces a southerly to
southeasterly flow over the forecast area, bolstered by an
afternoon seabreeze that should make significant inroads into
the foothills during the afternoon. In the meantime an east-west
oriented trough axis will still be present over the forecast
area, extending from the Northern Atlantic back into cut off low
pressure over the Ohio and Tennessee Valleys.
With modeled sfc charts showing convergence into the mountains,
especially as the sea breeze marches inland... some shallow
instability atop the mixed layer... and lingering cyclonic flow
aloft, I wouldn`t be too surprised to see a corridor of slow-
moving afternoon rain showers form. This would be most likely
over the northern mountains. Otherwise, temperatures are
forecast to warm into the 70s, warmest in the Connecticut River
Valley and coolest at the coast where it may struggle to hit
even 70 with the maritime influence. Instability- based cumulus
will make for a partly cloudy day over the interior, with
clearing behind the sea breeze.
Wednesday night looks to be a similar to tonight, although
stronger clearing and increasing subsidence will allow for
stronger decoupling and thus more in the way of valley and
coastal plain fog. Low temperatures should be a touch cooler
than tonight, with lows in the upper-40s to low-50s.
&&
.LONG TERM /THURSDAY THROUGH TUESDAY/...
Overview: The blocking pattern will continue to dominate the
forecast, but the period starts dry as upper level ridging is
overhead. An upper trough will then swing in to replace it later
in the week, leaving us in a wet pattern once again.
Details: Thursday looks dry and warm as the upper ridge remains
overhead, but it will begin shifting eastward. By Friday, upper
level moisture will be allowed to begin streaming in and it is
likely thickening clouds will tamper high temperatures down a
bit.
The trough settles into the region for the weekend. Continued
southerly flow will advect ample moisture into the region and warm
dewpoints well into the 60s. This will make for some muggy days and
contribute to instability. Confidence is increasing in daily
afternoon shower and thunderstorm chances with periods of heavy
rain. Models are in good agreement that PWATS will be in the
realm of 1.50- 2.00 inches meaning that, depending on how much
we can dry out before hand, any showers and storms that develop
will need to be watched closely for possible hydro concerns.
To begin next week either an upper trough, or an upper closed
low depending on what model you look at, looks to settle into
the Great Lakes Region. This will continue allowing moisture
into the region in some capacity, so despite some uncertainty,
rain showers appear likely.
&&
.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
Short Term...A mix of VFR and MVFR decks today continue through
tonight, lowering to IFR or worse in BR/FG and/or low CIGs for
many locations. In general there is low confidence regarding
which terminals experience more significant restrictions, and
for what duration, however there is a greater likelihood of
this occuring in river valleys and along the coastal plain...
which includes all of our TAF sites. Restrictions lift to VFR
Wednesday with light flow out of the south or southeast, then
potentially return Wednesday night as BR/FG and/or low CIGs.
Long Term...VFR should prevail to start the period, but sustained
southerly flow increasing marine fog/stratus development chances
make areas of IFR or lower possible beginning Friday night. In
addition, afternoon showers and thunderstorms may bring local MVFR
or lower conditions.
&&
.MARINE...
Short Term...High pressure builds into the Gulf of Maine
tonight and tomorrow before sinking south and east by Thursday
morning. This brings southeasterly flow through tonight turning
southerly flow tomorrow and tomorrow night, with seas and winds
remaining below SCA thresholds.
Long Term...High pressure and ridging will remain in place over the
waters keeping winds and seas below SCA thresholds. Seabreeze
circulations will develop each afternoon.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...None.
&&
$$
NEAR/SHORT TERM...Cannon
LONG TERM...Baron/Dumont
...Update to aviation forecast discussion...
.DISCUSSION...
Issued at 252 PM CDT Tue Jun 20 2023
Key Points:
- Hot and humid through this weekend
- Small chance of thunderstorms in central KS overnight into early
Wednesday
- Slightly better chance of storms Friday night through Saturday
The upper pattern remains much the same as it was 12 hours ago, with
an amplified ridge stretching across the central CONUS into Ontario
and Quebec and a persistent trough across the western US and Canada.
Water vapor imagery depicts a stream of upper-level moisture from
the High Plains to the Hudson Bay, and similarly, at the surface we
have the highest dew points stretching from southeast TX and LA up
through the High Plains into the Dakotas. A subtle perturbation on
the eastern side of the upper trough has developed low pressure at
the surface in the Dakotas.
That disturbance is progged to develop convection in western/central
NE, extending into parts of central KS. There are still varying
ideas among CAMs regarding the storm mode, and therefore the extent
of storm coverage and even the placement of storms. The HRRR has
been indicating storms being more scattered in nature, while the NAM
Nest and HRW-based models are more indicative of a MCS with some
solutions bringing the complex further south than others. In any
case, movement of storms appears to be focused along the
moisture/instability gradient with the best moisture transport and
instability west of the area. Still, MUCAPE of 1500-2500 J/kg in our
far western counties would support elevated thunderstorms
maintaining themselves overnight into early Wednesday if they make
it far enough south and east. Shear doesn`t look impressive, so
severe weather is not anticipated, but Pwat 1.5" or more could
result in some heavy rainfall for locations that get storms. Rain
should come to an end by the afternoon, although lingering mid/high
clouds could keep temperatures a few degrees cooler toward central
KS with highs in the upper 80s, compared with low 90s in the east.
The upper ridge looks to weaken somewhat Wednesday afternoon into
Thursday, with another perturbation rounding the edge of that ridge
and bringing another round of storms to the Plains. At this time,
these look to remain mostly out of the forecast area until perhaps
early Thursday when north central areas could get clipped.
Otherwise, mainly dry weather is expected into Friday afternoon with
the ridge axis moving overhead. A more notable wave moves across the
northern Plains on Saturday, dragging an associated surface cold
front through the area sometime in the afternoon or evening. The
better dynamics and upper support for thunderstorms and severe
potential are located well north, but there could be just enough
convergence along the frontal boundary to develop storms in our
area. Questions regarding timing and strength of the boundary keep
chances limited to 20-40% at this time. Outside of storms, Saturday
looks like the hottest day of the week with increased moisture
bringing heat indices around 100 degrees.
The front may hang around east central KS through Sunday, and if it
does, there is a slight chance (15%) for thunderstorms to redevelop
in those locations in the afternoon. Otherwise, temperatures with
highs in the 90s and lows in the 60s look to continue into early
next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 605 PM CDT Tue Jun 20 2023
Expecting VFR conditions to continue with just some high clouds
approaching from the west. Showers and storms tomorrow morning
should stay west of KMHK. Winds stay from the east to southeast
at around 5 to 10 kts.
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION...Picha
AVIATION...Reese