Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 06/04/20
Area Forecast Discussion
National Weather Service Binghamton NY
834 PM EDT Wed Jun 3 2020
A front will move across the region this afternoon and tonight
bringing passing showers and a chance for thunderstorms,
especially from the Twin Tiers southward, where a few storms
could be severe. Weak high pressure builds in on Thursday with
mainly dry weather, but other passing disturbances Friday and
Saturday will result in chances of showers and thunder.
.NEAR TERM /THROUGH THURSDAY/...
830 PM update...
A line of severe thunderstorms developed along the NY/PA border
late this afternoon and tracked across Northeastern PA during
the early evening, producing significant, widespread wind
A few thunderstorms continue to bubble up northwest of the
Finger Lakes region. We increased POPs over our northern and
western counties for the next 2-4 hours to account for isolated
thunderstorm activity. Intensity and coverage should lessen as
nocturnal cooling takes over.
Patchy will form overnight as temperatures drop into the upper
240 PM Update...
Slight destabilization of the boundary layer was occurring this
afternoon in response to pockets of solar heating mainly along
and west of the Central Southern Tier. Mid level lapse rates are
not substantial, and a solid trigger is lacking at the surface
or in satellite views aloft. The latest HRRR still insists on
redevelopment of showers and storms developing and moving from
the lower Finger Lakes/Southern Tier into NEPA between about 20Z
and 00Z. We suspect this will occur to some degree and have
left scattered/chance shower and thunderstorm activity into the
evening. The risk of severe storms looks to be waning fast as
favorable parameters consolidate over central and eastern PA.
Beyond sunset...weak high pressure with dry air will build
across the region later tonight through most of Thursday. Models
suggest a minor wave curling through the OH Valley and riding
along a stationary front over PA from Thursday afternoon through
the evening. Guidance remains consistent with much of the
precipitation chances remaining to our south, but there`s still
enough evidence for scattered shower, or thunderstorm activity
over NEPA tomorrow afternoon and night. SPC positions marginal
risk of severe along our southernmost border counties...but no
major concern from us at this time.
Seasonable temperatures expected for the next 36 hours.
.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/...
A cold frontal boundary will move through the area Friday night
with another boundary to our south. These boundaries coupled
with enough moisture and instability should be enough to spark a
few showers and thunderstorms throughout the day. Shear looks
very week for any organized activity. Highs should still get
well into the 80`s on Friday.
Friday night looks warm and a bit muggy still being ahead of the
cold front with lows only falling into the mid 60`s on average.
Still with the warm moist air in place the threat for a few
showers and thunderstorms continues.
By Saturday, the cold frontal boundary should east of the area.
As typical for northwest flow events one concern is that
blended model guidance looks to quick clearing out the skies
with the potential for a little additional moisture on the
backside of the departing low pressure system. A cooler airmass
slowly builds into the region lowering highs down to around 80.
High pressure builds into the region Saturday night with a
favorable setup for radiational cooling light winds and clear
skies. As a result, lows fall into the low and mid 50`s. With a
slightly tighter pressure gradient winds pick up to around 10
mph Saturday from the northwest but winds Friday look even
.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
The high pressure system builds into the region early next week
and deflects Cristobal a named system in the southern Gulf
toward the western Gulf coast states while also keeping the next
cold front well west of the region. While Sunday starts off
cooler with highs around 70 the flow eventually becomes
southerly with highs in the 80`s by mid-week. Low temperatures
will rise a few degrees each night from the cold 40`s Saturday
night well into the 50`s by Tuesday night. Right now modeling is
keying on interaction between a frontal boundary and what`s
left of Cristobal around Wednesday well northwest of our region.
Still a considerable amount of ensemble spread here but enough
members indicate a few showers and thunderstorms could move into
the area by Wednesday next week ahead of that front.
.AVIATION /01Z THURSDAY THROUGH MONDAY/...
730 pm update...
Most of the convection has ended. Another thunderstorms near ROC
will move southeast but should die before it gets to ITH.
Most sites will remain VFR through 00z 6/5. Exceptions are RME
with cigs expected to fall to fuel alternate MVFR 6 to 12z and
MVFR vsbys 9 to 12z.
Other exception will be ELM also late tonight from 8 to 13z due
to IFR vsby fog. Ground is wet from multiple rounds of storms
while winds go calm and skies clear.
West to Northwest winds at 5 to 10 kts early drops to light and
variable by 03z. Thursday southwest to west at around 6 kts.
Thursday night...Mainly VFR.
Friday through Friday night...Chance of showers and
thunderstorms with associated restrictions as front passes.
Saturday...Small chance of showers/restrictions, otherwise VFR.
Saturday night through Monday...Flight restrictions unlikely.
Area Forecast Discussion
National Weather Service Boston/Norton MA
1005 PM EDT Wed Jun 3 2020
The rest of Wednesday into early tonight will feature passing
showers at times for most of interior Southern New England, with
thunder also possible towards the Connecticut River Valley.
Clearing later tonight with areas of low clouds and fog towards
the South Coast, Cape Cod and the Islands. Mainly dry and mild
weather for Thursday. A weak surface low may bring showers to
the South Coast later Thursday night. Warm and humid for the end
of the week, with showers and thunderstorms likely Saturday as
a cold front moves across Southern New England. Drier and cooler
weather as high pressure builds into the region early next
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
10 PM Update...
Forecast is largely on track. As expected, Philadelphia and NYC
got pounded by the MCS`s earlier this evening while we got
grazed by the periphery of the MCS that affected NYC. North of
Boston, the showers briefly intensified and had some lightning
activity, mostly over the waters. So we took care of those
activities with SPS`s and Special Marine Warning.
Otherwise, slowed the development of dense fog across the South
Coast with the latest high-res and GFS lamp guidance as boundary
layer remains rather well-mixed at this time. Will let the
midnight crew continue to monitor and decide on any fog
645 PM Update...
Radar reflectivity shows two MCS`s, one across NE PA and another
across SE PA. The former is headed for NYC metro and the latter
is headed for the Philly area in the next couple of hours. This
is thanks to a 60 kt wind max embedded in a positively tilted 500mb
shortwave trough centered over Upstate NY. While the
aforementioned areas have good instability with SBCAPE of 1000
to 2000 J/kg, instability is rather limited in our area, with a
swath of up to 1000 J/kg over W CT and a more broader swath of
500 J/kg of SBCAPE over the remainder of our CWA per SPC
mesoanalysis. The CAM guidance, especially the 18z HRRR and NAM
Nest has done well in depicting the MCS`s and a few disorganized
cells clipping Western CT. There is also a line of showers
crossing S NH into ME that could skirt NE MA, but given the lack
of instability, really not expecting much more than a few
showers. Furthermore, surface dew point depressions range
between 15 to 20 degrees for most locations away from the
immediate coast, further limiting the coverage of precipitation.
As a warm front lifted north, warm, moist advection has sent
dew points into the 60s for much of our area, giving a muggy
feel to the air. With a southwest flow and warm moist air
blowing over cold ocean waters in the mid to upper 50s, expect
fog to develop across the South Coast. There are indications
from Bufkit mesoscale soundings that the winds wouldn`t
completely decouple, potentially limiting the extent of the
dense fog. So for now, have opted against any fog headlines but
will be something to watch into the overnight hours.
405 PM Update:
For the rest of the afternoon into early tonight:
A lot of mid-level cloud cover remains across Southern New England,
with very light passing showers currently progressing across eastern
MA. These showers are very light and most are not producing anything
measurable. However looking to the west across eastern and central
NY, greater clearing has allowed for some destabilization and re-
development of fairly shallow convection from roughly Utica NY
southward towards northern PA. This was indicated earlier by recent
runs of the HRRR, possibly from old outflow/boundaries left behind
from today`s mid-Atlantic MCS. Air mass is more unstable there than
across our area, with about 1000-1500 J/kg of surface-based CAPE.
However per SPC`s mesoanalysis, a corridor of 500 J/kg of surface-
based CAPE has developed into northern CT and indications are that
some further, albeit modest, destabilization is possible and some of
these showers may develop into thunder as they move southeast off
the Catskills. Storm steering flow is mostly from the WNW, and it is
possible these showers or storms may brush part of the CT Valley in
MA/CT, but that should really be it on the thunder threat. Will have
a few passing showers across the rest of MA and into RI but that
should be it.
For the rest of tonight:
Rain chances decrease by mid-evening toward dry weather as winds
become westerly. Toward the South Coast, Cape Cod and the Islands,
rising dewpoints will allow for lower stratus and possible mist/fog
to develop after midnight. HREF low-level sky cover forecast really
socks in this area with lower clouds, with visibilites in fog/mist
mainly in the 1 to 3 mile range, but may be as low as one-half mile.
Lows tonight in the mid 50s to lower 60s.
.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
Should have some ongoing areas of fog or low clouds/stratus along
the South Coast, Cape Cod and the Islands, with generally tranquil
weather elsewhere. There is some question how long these areas may
clear out in SW flow; did keep mostly cloudy skies going until
midday/early afternoon, with some breaks and peeks of sun into mid-
afternoon. Cooler temperatures here in the low 70s given the longer
period of clouds and some onshore flow component.
However for the rest of Southern New England, 500 mb height rises
and weak ridging should offer comparatively better weather
conditions. Warmer temperatures from mostly sunny skies, though mid
to high clouds will increase late in the day as moisture from the
next disturbance spreads northeast from the mid-Atlantic. So away
from the coast, looking at highs in the low to mid 80s. Will start
to notice the humidity a bit more with dewpoints in the upper 50s to
lower 60s, but humidity levels overall are still fairly low.
Height rises then transition toward modest height falls with
guidance indicating a disturbance/500 mb vort max and related
surface low pass near NJ/Long Island. There are significant
differences in mass field evolution and strength between the NAM and
the GFS, an indication of possible convective feedback problems. The
NAM is a far more robust feature and would spread steady rains to
the South Coast, Cape Cod and the Islands. The GFS is much weaker
and features less rain/QPF. Most of the available CAMs at this range
are also on the stronger side and spread a shield of rain across a
larger part of Southern New England. Will keep PoPs on the lower
side, mainly at Chance to solid Chance levels near the South Coast,
Cape and Islands, and slight chances to the Mass Pike. A fairly mild
and somewhat humid night with lows in the mid 60s, with low-mid 60s
dewpoints adding to the humidity level.
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
* Few showers/thunderstorms likely on Saturday
* Dry and seasonably warm early next week
Friday into Saturday...
A weak shortwave exits the coast of Southern New England early
Friday; providing a few morning showers or a rumble of thunder. At
500 mb the relative humidity values are nearly bone dry. Any morning
clouds should erode away. The 850 mb temperatures at 18z range from
12 to 16 degrees Celsius - allowing us to heat-up into the middle
and upper 80s. With adequate low-level moisture dewpoint Friday
could reach to the low and middle 60s south of the Pike. Doesn`t
appear to be a comfortable afternoon for those who aren`t a fan of
hot and humid weather.
A cold front will approach the region sometime on Saturday; the
timing of the front isn`t in the best agreement as of Wednesday
afternoon. Guidance is hinting towards the threat of some
thunderstorms Saturday, if the front comes through during the
afternoon and not the morning. Across western MA/CT Saturday
afternoon there`s the potential to have CAPE values between 1,000 to
2,500 J/kg, a lift index between -4 to -8, and 70 kts of bulk
shear. Which could lead to some strong or severe storms.
Bulk of the moisture moves east and we are left with remnant clouds
and a few isolated showers into Sunday as a trough slides across New
Sunday into Wednesday...
Dry and cooler temperature return on Sunday with mostly sunny
conditions as an area of high pressure moves south out of Canada.
This region of high pressure will provide a quiet weather week ahead
with seasonably warm temperatures in the mid-70s.
.AVIATION /02Z THURSDAY THROUGH MONDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
02z TAF Update:
Tonight: Moderate to high confidence.
Expect shower activities off the South Coast to exit by 03z. VFR
to start this evening for most terminals. Expect VFR conditions
to persist for terminals away from the South Coast. Exception
is for development of MVFR to LIFR ceilings/visbys in fog and/or
stratus near the South Coast, Cape and the Islands after 05z.
Confidence is fairly high on development but is moderate on
intensity and extent of fog. So there is a potential for
frequent changes in categories for terminals on the South Coast
and the Cape. W winds around 5-10 kt.
Thursday: High confidence.
VFR with SW winds of 5 to 15 knots. Possible turn to SE/ESE
with sea-breezes near the coast.
Thursday Night: High confidence.
VFR clouds for most, though lower-VFR to MVFR ceilings possible
in frontal rain showers towards the South Coast, Cape and
Islands. SW winds decrease to 4-8 kts.
KBOS Terminal...High confidence in TAF. VFR conditions expected
throughout TAF period.
KBDL Terminal...High confidence in TAF. VFR conditions expected
throughout TAF period.
Outlook /Friday through Monday/...
Friday: VFR. Slight chance SHRA, slight chance TSRA.
Friday Night through Saturday: Mainly VFR, with local MVFR
possible. Breezy. Chance SHRA, chance TSRA.
Saturday Night through Sunday: VFR. Slight chance SHRA.
Sunday Night through Monday: VFR.
No change to the previous discussion.
Tonight through Thursday Night: High confidence.
Small craft advisories remain in effect for most of the southern
waters due to a long fetch of south to southwest winds causing
seas to rise into the 4-6 ft range. SCAs are posted for these
seas into Thursday, though it may take a good part of Thursday
night before seas subside on the southern outer offshore
waters. SW winds should remain below SCA levels through the the
period, generally 10-20 kt.
Will also make note of low clouds/fog development on the
southern waters tonight, with visibilities variable ranging in
the 1-3 mile range, at times as low as one-half mile.
Outlook /Friday through Monday/...
Friday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Slight chance of rain showers.
Friday Night through Saturday: Winds less than 25 kt. Seas up
to 5 ft. Chance of rain showers, chance of thunderstorms.
Saturday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft. Slight chance of rain showers.
Sunday: Winds less than 25 kt. Seas up to 5 ft. Slight chance
of rain showers.
Sunday Night through Monday: Winds less than 25 kt. Areas of
seas approaching 5 ft.
MARINE...Small Craft Advisory until 2 AM EDT Friday for ANZ255-256.
Small Craft Advisory until 8 PM EDT Thursday for ANZ235-237.
Area Forecast Discussion
National Weather Service Des Moines IA
614 PM CDT Wed Jun 3 2020
...Updated Aviation Discussion...
.DISCUSSION.../Tonight through Wednesday/
Issued at 312 PM CDT Wed Jun 3 2020
Overnight storms should mostly miss Iowa to the SW, but chances for
some strong to severe storms reload for Thursday afternoon/evening,
potentially lingering through Friday. The heat and some degree of
humidity will stick around through the weekend and Monday, including
more opportunities to see widespread low 90s. Cooler conditions
return by the middle of the week, including an outside shot to see
remnants of Tropical Storm Cristobal.
Today through Thursday Night...
A messy forecast through this period. Synoptic and hi-res/CAMs
continue to be all over the place with their solutions this
evening/overnight and tomorrow evening/overnight. While there is
absolute consensus in convection, there is little consensus in
track/location, which is not unusual when being driven by ongoing
MCS progression. As a result, have relatively broad brushed both
time periods for convection.
The first round, tonight, will stem convection in south-central
South Dakota and north-central Nebraska (currently beginning)
growing upscale into an MCS. Most guidance suggests the bulk of the
activity turning to the southeast, riding along a relative
instability gradient, and missing the bulk of the forecast area. The
GFS and HRRR have continued to show some lower end activity into the
SW, so have kept some nominal mentions in the W/SW. Do not expect
much severe potential given the lack of instability, but could see
some enhanced winds with drying low-mid levels should it maintain
some gusto into the area.
The second round, tomorrow afternoon/evening/overnight, is the most
concerning for the area. While moisture return will not be dramatic,
combined with steep low level lapse rates, instability tomorrow
afternoon is likely to reach the 1500-2500 J/kg range in portions of
northern Iowa tomorrow and greater further south where better dew
points will reside. Low level shear continues to look lackluster,
but better deep layer shear (35-40+ kts), especially north, raises
concern for organization for any initially isolated cells. With the
eroding cap by the evening, theta-e advection, subtle short wave,
and weak surface boundary, there will be no issue for initiation.
Initiation will occur in southern Minnesota to northern Iowa where
the best forcing aligns. The question more becomes how quickly it
will congeal into a linear mode. Regardless, threat progression
looks to be hail/wind initially followed by primarily wind once it
becomes more linear. SPC discussion also highlights the relative
messy nature of the forecast and results in the broad brushed
Slight, and cannot find any reason to fault its location given the
Friday through Wednesday...
Main concern here will be how far south the surface boundary pushes
from Thursday evening/overnight convection. Should it push far
enough into Missouri, Friday may very well end up dry. Otherwise
scattered convection may be seen across portions of southern Iowa
throughout the day and evening. For the time being, majority of
available guidance point towards some lingering convection across
the southern third to half of the state.
Upper level/thermal ridging will build across the state through the
weekend, primarily keeping it dry and warm/hot/humid. By Sunday, may
see some ridge riders move across, and any threat associated there
will be evaluated in the upcoming days. Opportunity for low 90s
highs will continue, especially Sunday into Monday as 850mb temps
around 20 deg C continue to be suggested. The ridge will quickly be
shunted eastward as the western trough deepens, eventually giving
the area another round of showers/storms before cooling back down
towards normal in the upper 70s by the middle of the week. As the
trough kicks out, there remains a chance for the remnant of Tropical
Storm Cristobal to make it to the state, but the continues to seem
.AVIATION.../For the 00Z TAFS through 00Z Thursday evening/
Issued at 612 PM CDT Wed Jun 3 2020
VFR conditions prevail through the current TAF period. Isolated
TSRA activity could impact terminals overnight, and then again
Thursday evening. Forecast confidence in timing and location of
any TSRA is much too low to include in the TAF at this time.
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
630 PM CDT Wed Jun 3 2020
.SHORT TERM...(This evening through Friday night)
Issued at 443 PM CDT Wed Jun 3 2020
Focusing on the first 5 night/day periods in this section, BY FAR
the main concern is the tricky thunderstorm/severe weather
chances mainly for tonight, but potentially also for various
points during the Thurs-Fri time frame (although confidence in the
actual likelihood of storm development for most of the area is
very much in question beyond tonight). In other departments,
confidence is high that our continued, seasonably-hot weather
pattern continues right on through the next few days, as we
continue one of the warmest starts to June in recent memory.
Briefly covering the here-and-now as of 4 PM:
Other than a few rogue showers/weak thunderstorms that briefly
flared up late this morning in our extreme southeast CWA (Mitchell
County KS area), it`s been very much as expected today with mostly
sunny skies, SLIGHTLY-cooler high temperatures than the past few
days (highs mainly 88-93) and fairly light easterly to southerly
breezes mainly around 10 MPH or less. In the mid-upper levels,
water vapor satellite and short term model data depicts broad
west-northwest flow over the Central Plains, with the main low-
amplitude shortwave trough of interest dropping east-southeast
across the SD/NE border area.
Now looking ahead forecast-wise through the next 5 periods...
The main focus by far is the Slight Risk of severe storms for the
entire coverage area (CWA). Confidence is fairly high that most of
our CWA will remain dry/storm-free through around 7 PM, although
isolated-to-scattered activity already underway to our west-
northwest will be on a gradual approach through that time. Based
on consensus of various short term models (including HRRRV4), our
main 6-hour block of concern for severe storms pretty clearly
looks to be 7pm-1am, during which time at least isolated-scattered
storms will drift in from the west and northwest, in an
environment characterized by up to around 2000 J/kg mixed-layer
CAPE and modestly-decent deep-layer shear of 30-40 knots. This
will easily support organized multicell structures with brief
supercell characteristics possible. The big question is whether
activity remains more isolated-scattered or perhaps becomes more
widespread in the form of a larger scale complex/MCS. At the very
least, hail of quarter to golf ball size and wind gusts of 60+ MPH
are on the table, but any organized complex with a good cold pool
could easily bring 70+ MPH winds into the picture. The bottom
line: confidence is high that at least parts of the CWA will see
an active evening, but just how much of it is in question? After 1
AM and through the late-night, some strong to marginally-severe
activity could linger, but the "main show" should be over by then.
In other departments, low temps tonight are aimed low-mid 60s most
areas. Not too concerned about patchy fog formation in the wake of
storms, but suppose some limited coverage not completely out of
Confidence is high that the majority of the CWA stays dry, and
this is strongly supported by NAM/HRRR solutions. Despite lack of
forcing aloft and capping trying to reign, models such as the
ECMWF are more aggressive in trying to pop late afternoon (and
potentially severe) storms mainly in our far east-northeast zones.
If anything goes, severe is possible, but agree that the overall
CHANCES of storms developing/lack of coverage support SPC
downgrading the entire CWA to only a Marginal Risk on the latest
Day 2 outlook. For the evening/overnight hours, will carry low-
confidence/slight chance PoPs across the area, as there could be a
bit better chance of hit-and-miss activity versus the late
afternoon hours. Temp-wise, based on our recent trends of slightly
under-forecasting highs, have nudged up highs Thursday a few
degrees, with mainly low-mid 90s. Winds will average 5-15 MPH from
a generally southerly to southwesterly direction.
As if there isn`t enough uncertainty in the Day 2 storm chances,
this sentiment only grows for this Day 3 time frame. As upper
ridging starts to build aloft, odds are fairly high that most of
the CWA remains dry/storm-free. However, with continued
significant instability around, will need to watch for "mesoscale
accidents" that could potentially pop isolated severe weather.
That being said, am not overly-confident in SPCs Day 3 Marginal
Risk in our east (would expect some typical modifications as it
gets closer). Otherwise, the early-summer heat continues, with
highs perhaps just barely cooler than Thursday but still mainly
low-mid 90s for highs. Daytime breezes look to average 10-15 MPH
from the east- northeast.
.LONG TERM...(Saturday through Wednesday)
Issued at 443 PM CDT Wed Jun 3 2020
General overview of this 5-day period:
The two main stories during this time frame remain/are:
1) Temperature-wise, a pronounced cool-down from continued well-
above-average heat Saturday-Monday (highs mainly upper 80s to mid
90s), to cooler and potentially even slightly BELOW normal
readings Tues-Wed in the wake of a seasonably-strong cold front
(highs only 70s to low 80s).
2) As for rain/thunderstorm chances, the truth is that although
many of these day/night periods carry at least slight chances/PoPs
somewhere within the CWA, many of these chances most definitely
carry a medium-high degree of uncertainty, and it`s just not worth
putting too much stock in them yet. See "daily details" below for
a bit more insight, but from a large-scale forcing standpoint, the
chances during the Mon night-Tues time frame look to carry the
overall-highest confidence of coming to fruition (on at least a
somewhat widespread basis). On the flip side, barring a pretty
big shift in the latest ECMWF/GFS model trends, our going
rain/thunderstorm chances for Tuesday night into Wednesday are
looking rather questionable and may ultimately need removed.
With the big points covered, will finish with some brief/day-to-
This is currently a dry forecast for the majority of the CWA,
which favors the latest ECMWF solution much more so than the
considerably-wetter/stormier GFS. With ridging aloft the main
influence, the main question is whether any weak forcing can
overcome warm temps aloft/capping to spark any activity. If so,
severe storms certainly appear possible. In higher-confidence
departments, this is expected to be another very warm day with
highs aimed mainly low-mid 90s, and also looks rather breezy out
of the south-southeast.
This 24-hour block officially carries a dry forecast CWA-wide as
upper ridging/warm air aloft/capping looks to prevail. Another hot
and quite-breezy (windy?) day out of the south with highs aimed
mainly mid 90s.
This time frame marks the beginning of a pattern/temperature
change as both ECMWF/GFS are in good agreement on a large-scale
trough and associated surface cold frontal passage. The day looks
mostly dry, with better storm chances kicking in Mon night. Temp-
wise, another hot one, currently aimed low-mid 90s.
High confidence in cooler temperatures behind the aforementioned
cold front, with highs very preliminarily aimed mid 70s north to
low 80s south, which will probably feel fairly refreshing after
the ongoing/upcoming heat between now and then. As earlier
mentioned, our currently-advertised rain chances for Tues night-
Wed are looking pretty questionable, at least by Day 7 standards.
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Friday)
Issued at 621 PM CDT Wed Jun 3 2020
The main aviation forecast concern will be thunderstorms in the
next 6 hours. A line of thunderstorms will move in from the west
this evening. The HRRR has a decent handle on timing and followed
that fairly close, expect it to be a 02-04z timeframe at both
terminals, with lingering precip possible after. Expect most
activity out by 06z, but have held on to VCTS until 07z as a
buffer. Winds will be variable as the storms move through and are
expected to remain variable through the overnight hours. Winds
will be southerly again tomorrow with few clouds and VFR
Area Forecast Discussion
National Weather Service Green Bay WI
1043 PM CDT Wed Jun 3 2020
Updated aviation portion for 06Z TAF issuance
.SHORT TERM...Tonight and Thursday
Issued at 358 PM CDT Wed Jun 3 2020
The latest RAP analysis and satellite/radar imagery show
yesterday`s cold front stalling over the southern Great Lakes
early this afternoon. Further north, a weak area of high pressure
is building southeast into the region. Diurnal convective clouds
have popped along a weak surface trough over much of northeast
WI, but have not observed any evidence of showers. Conditions are
relatively quiet upstream until the Dakotas where the next frontal
system is generating a few clusters of showers and storms. As
this cold front approaches north- central WI tomorrow, forecast
concerns mainly revolve around shower and storm chances.
Tonight...The high pressure system will settle over the area and
convective clouds should dissipate with loss of heating early this
evening. The rest of the night should be mostly clear with light
winds. Good radiational cooling conditions will spell some 40s in
the cold spots over the north woods. But most locations will see
temps range through the 50s.
Thursday....Shortwave energy passing across southern Canada will
push a cold front across northwest WI in the afternoon. As the
front approaches, southwest winds will advect a modest
instability axis with surface based capes approaching 1000 j/kg
into central and north-central WI. Forcing along the front is weak
at best, and support aloft looks relatively meager as well.
However, many of the higher resolution models are quite ambitious
with shower and thunderstorm coverage, which throws a fair amount
of uncertainty into the forecast. Nonetheless, have a difficult
time increasing precip chances given the lack of forcing, so will
remain conservative. Most of the day should remain dry though.
Temps are projected to be slightly cooler than today, but still in
the 80s except along the Lake.
.LONG TERM...Thursday Night Through Wednesday
Issued at 358 PM CDT Wed Jun 3 2020
The main highlights from this forecast period are the various
chances for showers and storms late Thursday night into Friday and
early next week.
Thursday night through Friday...A shortwave will push through the
region late Thursday night bringing chances for showers and
thunderstorms. CAMs show some signs of convection developing ahead
of the shortwave on Thursday evening, however having a hard time
believing this solution as there is very little forcing present
during this time period. This signal is also not present in any of
the other models. With confidence low, kept chance PoPs in the
forecast for central and north-central Wisconsin before midnight.
Chances for showers and storms will then increase after midnight as
the surface cold front moves into the region. Instability and steep
mid-level lapse rates appear to line up at some point over central
Wisconsin late Thursday night into early Friday morning allowing the
chance for an isolated strong storm capable of producing damaging
winds and hail. Precip chances will come to an end by Friday
afternoon as the shortwave pulls out of the region.
Rest of the extended...A surface high pressure system will slide
into the region late Friday night as the upper-level pattern
transitions to a northwest flow. This will bring "cooler" air to the
forecast area. High temperatures for the weekend are forecast to be
in the 60s along the lakeshore and 70s inland. Upper-level ridging
will build over the Midwest on Sunday allowing temperatures to rise
into Monday. There is some potential for a few light showers on
Sunday, mainly across the north, before the main axis of the upper-
level ridge builds over Wisconsin. Monday will be warmer with high
temperatures rising to the 70s along the lakeshore and 80s inland.
The upper-level pattern will then transition to a southwest flow
into Tuesday as the ridge shifts to east. This will allow, what is
currently Tropical Storm Cristobal, to merge with the southwest flow
and advance north to Wisconsin. Since this is a tropical system,
PWATs rise to around 2 inches over Wisconsin Tuesday into Wednesday.
Although the finer details have yet to be determined, heavy rain and
thunderstorms are likely to occur with this system.
.AVIATION...for 06Z TAF Issuance
Issued at 1043 PM CDT Wed Jun 3 2020
Good flying weather is anticipated through much of the taf
period. Some mid and high level clouds will drift across the
region during the overnight and into Thursday morning. Clouds
will increase and a few showers or storms will be possible across
far northern WI on Thursday afternoon and across central and
north-central Wisconsin Thursday evening. The best chance for rain
appears to be later Thursday night when a mid level shortwave
arrives from the west, therefore will leave rain out of this set
AREA FORECAST DISCUSSION
National Weather Service Morristown TN
1037 PM EDT Wed Jun 3 2020
Convection is dissipating with the loss of daytime heating.
Doppler radar at 0230Z showed a few light showers or sprinkles
remaining around Roane and Loudon Counties. The latest HRRR had a
good handle on this activity, so used that guidance to update PoPs
the next 6 hours. Have all areas dry by 05Z with only sporadic
showers over the mountains the second half of the night. Increased
cloud cover through the night based on satellite obs as a
disturbance slowly approaches from the west. Lows tonight are on
track with a warm and muggy night expected, so just inputed
current observations for temps, dew points, and winds in order to
tweak hourly curves. The rest of the forecast is on track.
00Z TAF DISCUSSION.
VCSH at CHA and TYS will be gone by 02Z, then dry weather and VFR
will prevail through the night. A slowly approaching cold front
will cause showers/storms to start developing after 14Z Thursday increasing
in coverage through the afternoon and early evening. This will
cause periods of MVFR or lower conditions at all TAF sites with
brief heavy rain and lightning.
/ISSUED 256 PM EDT Wed Jun 3 2020/
SHORT TERM (This Afternoon through Thursday)...
Convective has blossomed across Middle TN, north AL, and along
the Cumberland Plateau in the hot, humid, and unstable atmosphere.
Model soundings indicate a cap in place across much of the
forecast area. The cap is stronger the further to the north and
east. The RAP indicates the cap is the weakest where there is
ongoing convection and expect the cap to weaken further to the
north with showers continuing to initate further north throughout
the afternoon and evening. Best chances for precipitation will
continue to be for southeastern portions of the forecast area.
Mid-level lapse rates above the cap are rather impressive in
excess of 7 degrees C/Km in some cases. These lapse rates yield
SBCAPE values of 1500 to as high as 2500 J/Kg. The deep layer
shear is very weak with 0-6 km Bulk Shear values of less than 10
kts. Overall, not expecting any organized strong to severe storms
but could see a storm pulse up to become marginally severe later
this afternoon into the evening. Again, this would generally be
for locations south of I-40 where the cap is weaker. Any ongoing
convection should diminish in coverage and intensity around sunset
with the loss of daytime heating. Lows will be mild once again
tonight in the mid 60s to low 70s.
A weak upper level trough will move over the area tomorrow with some
cyclonic flow in the mid and upper levels. Model soundings indicate
the mid and upper levels will feature more moisture than today. This
scenario yields less impressive lapse rates than today with SBCAPE
values more in the 1000-2000 J/Kg range. There is a slight uptick in
deep layer shear with a jet passing well to the north, however, deep
layer 0-6 km bulk shear values are still in the 15-25 kt range at
best. Model soundings do not feature a cap tomorrow and with PW
values in the 1.5-1.8 inch range expect widespread convection to
develop. A few of these storms could become strong and maybe
marginally severe. Will continue the mention in the HWO but
confidence is not very high. Showers and storms tomorrow will also
feature locally heavy downpours that could lead to some brief
flooding issues in areas of poor drainage. Dewpoints will continue
to be in the typical mid 60s to low 70s tomorrow but temperatures
will be a bit cooler with the increased cloud cover and
precipitation. High temperatures on Thursday will generally range
from the low to mid 80s for most locations.
LONG TERM (Thursday Night through Wednesday)...
The extended range period kicks off on Thursday night amidst low
amplitude longwave troughing across the eastern CONUS, with a series
of embedded shortwave impulses passing through the mean flow aloft,
all while subtropical ridging prevails over the western Atl and
another ridge holds over the Desert Southwest. At the surface, for
the most part, high pressure dominates over the southeast states
while a weak frontal axis slowly creeps southward through the OH
Valley. Furthermore, the larger highlight at this point will be the
status/forecast of TC Cristobal located in the southwest GOM. At
fcst initialization, modest daytime heating amidst the weak height
falls aloft look to support ongoing convection across much of the
region, which could last into the overnight hours given persistence
of elevated instability and modest moisture in the profiles. Much
the same for Friday as upper heights continue to favor some weak
shortwave activity coinciding with deep moist and unstable profiles,
however pops will be slightly less (highest over the mountains) as
the aforementioned surface front looks to essentially washout
nearby, which would suggest little/no sfc frontal convergence. By
that point, the overall pattern begins to complicate as TC Cristobal
enters the central GOM and a northern CONUS trough digs across the
Great Lakes region, pushing a cold front through the Upper Midwest.
Into Saturday the northern trough will dig into the OH Valley
driving the cold front southeast, while the western ridge amplifies
and slides east across the Plains. As for Cristobal, guidance tends
to suggest an eastern motion given the intrusion of the large upper
ridge to the west. Closer to home, falling heights beneath the
trough combined with an approaching front will suggest another day
of diurnal convection, with the highest probs over the mountains.
Overnight into/through Sunday, the upper trough axis will shift east
of the Appalachians allowing the surface front to move in as deep
ridging builds over the OH and northern TN Valleys. Given this
further eastern migration of the upper ridge, Cristobal looks to
take a jaunt back westward before making landfall across the central
Gulf Coast. The aforementioned surface cold front is progged to
stall nearly atop the forecast area into Monday, before getting
pushed northward as Cristobal moves inland and the upper ridge
centers over the Southern Appalachians. By Tuesday, Cristobal
should be inland across the central CONUS favoring deeper moisture
advection into the southeast states and southern/central
Appalachians. All said, Sunday and Monday look drier with pops only
in the slight chance levels south of I40, dry northward, while pops
ramp back up slightly on Tuesday as WAA commences. As for
temperatures, above normal levels will prevail through the period,
warmest on Friday/Saturday, coolest on Sunday/Monday (and Tuesday
across the southern valley). Would like to note that confidence in
the pattern next week is rather low as much depends on the track of
Cristobal, stay tuned.
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 69 85 68 87 69 / 20 60 50 40 30
Knoxville McGhee Tyson Airport, TN 69 85 68 86 69 / 20 60 50 50 20
Oak Ridge, TN 68 85 68 87 68 / 20 60 50 40 20
Tri Cities Airport, TN 65 84 64 83 64 / 10 60 50 60 30
Area Forecast Discussion
National Weather Service Nashville TN
901 PM CDT Wed Jun 3 2020
FOR EVENING DISCUSSION.
Radar imagery this evening shows earlier scattered thunderstorms
across the area have dissipated with just some stratiform rain
over our southern counties at present. Latest CONSShort and HRRR
models indicate some isolated showers and storms could pop up
overnight in the very humid and unstable airmass in place (MLCAPE
of 1018 J/Kg on 00Z OHX sounding), so will show a slight chance
pop overnight for all zones. No other significant changes were
made to the forecast for tonight. Precip chances look to ramp up
significantly Thursday morning and especially Thursday afternoon
as a weak shortwave trough moves across the region. GFS forecast
soundings for tomorrow show MLCAPE over 1000 J/Kg with DCAPE
around 750 J/Kg and PWATs in the 1.6-1.7 inch range, indicating
some storms could be severe with wet microbursts and hail.
00Z TAF DISCUSSION.
Scattered showers and thunderstorms that fired up today from an
old boundary out of Kentucky have dissipated. Expect more
scattered showers to develop early again tomorrow (maybe even
closer to midnight). Scattered showers and thunderstorms will be
around tomorrow. A few storms could even be strong to severe.
Clouds will start VFR and most likely become MVFR. If a storm
moves over a terminal conditions could briefly become IFR/LIFR.