Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 06/26/20
Area Forecast Discussion
National Weather Service Birmingham AL
659 PM CDT Thu Jun 25 2020
.UPDATE...
For 00Z Aviation.
&&
.SHORT TERM...
/Updated at 0128 PM CDT Thu Jun 25 2020/
Through Tonight.
Scattered to numerous showers and storms continue across the
eastern half of Central Alabama as of early this afternoon. So
far, we`ve been able to achieve modest diurnal heating with
widespread clouds, but most locations have been able to rise into
the lower 80s as of the 1pm hour. Coverage of showers and storms
is still expected to be widespread as we go into the late
afternoon and early evening hours. A few strong storms certainly
can`t be ruled out, especially farther south with a bit more
surface based instability and 0-6km bulk shear of 20 to 25 knots
could sustain a few more updrafts. Additional showers and storms
are expected to develop to our southwest and move northeast
through the afternoon and evening. PoPs have been updated to
reflect that thinking, keeping likely PoPs in the forecast for
most locations through 10pm. At least scattered activity can be
expected to continue through the overnight hours with muggy
overnight temperatures.
56/GDG
Previous short-term discussion:
/Updated at 0340 AM CDT Thu Jun 25 2020/
Today and Tonight.
Mesoanalysis depicts a longwave trough across portions of the
Northeast CONUS with an upper-low spinning just south of Hudson Bay,
and an associated trough axis extending into the OH and TN Valleys.
Farther south, anticyclonic flow wraps around a subtropical ridge
centered near the FL Peninsula. A previous shortwave trough just to
our west and southwest has weakened and elongated, though a weakness
in mid-level heights is still observed near this area with embedded
convective vort maxes across the western Gulf. Overall, this
configuration continues to provide a pipeline of tropical moisture
across much of the Deep South as low-level flow trajectories remain
situated to advect Gulf moisture into the area. Low overcast and
patchy fog will linger into early this morning as a result.
Isentropic ascent and confluent zonal flow below 500 mb will provide
a corridor of showers and eventually thunderstorms across Central
Alabama later this morning and into the afternoon. PWs remain in the
1.6-1.9" range as indicated by RAP mesoanalysis and recent 00Z
RAOBs, with near-saturation through much of the troposphere (higher
PWs are south and southwest still yet). Aided by modest diurnal
heating, PoPs steadily increase into the afternoon and evening, but
sporadic activity including a rumble of thunder can`t be ruled out
across the area this morning as well. Low stratus overcast should
inhibit convective activity until mixing can occur later today,
however. Overall behavior of thunderstorms should be more tame as
compared to yesterday as the environment lacks low and deep-layer
kinematic support for stronger/briefly organized updrafts, as well
as relatively muted buoyancy with abundant mid/upper-level cloud
cover. However, there`s slightly better flow progged to stretch
across the southern half of the area today. This could promote a few
multicell clusters later in the convective life cycle, but this same
area also remains on the lower end with CAPE/DCAPE. A few pockets of
better sunshine may manifest across the area which could increase
low-level lapse rates and instability a bit, but
confidence/predictability on this is low. All things considered,
another generous coverage of rain is forecast, with high
temperatures in the 80s. I bumped temperatures down a tad overall,
though any extra sunshine here and there could ruin this adjustment
in spots. Shower and thunderstorm coverage and intensity should wane
throughout the evening with lingering showers overnight. Lows should
fall into the mid 60s to near 70.
Friday afternoon.
We may get a bit of a break from the day-to-day widespread rainfall
on Friday as guidance suggests positioning of the subtropical ridge
farther northwest, generally closer to our area. Anticyclonic flow
aloft and slightly drier air has led to PoPs being truncated to
<40%, with best chances north of US Hwy 80 where westerly to
northwesterly flow aloft remains a little more intact, just on the
northwestern periphery of the ridge. Warmer conditions are expected
with slightly less cloud cover, as well as drier air above 700 mb.
We`ll keep an eye on thunderstorm activity during the afternoon
since this could support a few stronger convective downbursts, even
though PoPs are lower. Highs are forecast in the mid 80s to lower
90s.
40/Sizemore
.LONG TERM...
/Updated at 0150 PM CDT Thu Jun 25 2020/
Saturday through Thursday.
Overview:
Expect chances for showers and thunderstorms to remain highest
during the midday through early evening hours but a few lingering
showers and storms will remain possible overnight through the period.
Features:
Upper ridging will become positioned over the Eastern Gulf
of Mexico on Saturday while diffuse troughing moves into the area
from the northwest.
A longwave trough over the Ohio River Valley Region will move east
over the East Coast portion of the country on Sunday. The height
falls will help to confine the upper ridging to our southeast
further south into the the South Florida and Southeast Gulf
vicinity. Meanwhile, Longwave ridging will amplify and build into
the Mississippi Valley from the Western Gulf Coast northward through
Wisconsin and Minnesota. Expect height rises to develop over the
area Sunday and persist into the day on Monday.
Higher heights will develop aloft over Northeast Mexico and into
South Texas Late Monday into Tuesday as heights locally begin to
descend with the weakening of the ridging aloft. A closed upper low
will dive southeast out of Eastern Canada into New England and
height falls are expected down the spine of the Appalachians through
the Carolinas and into Georgia Tuesday into Wednesday. Heights will
also fall over the Mid Mississippi River Valley region in response
to a potent closed low positioned over Montana Tuesday into
Wednesday. Expect the area to remain under the influence of a
weakness aloft into the day Wednesday and continuing into
the day on Thursday.
Toward the surface. expect weak high pressure toward the surface to
nose into much of the area from the southeast on Saturday and
persist through Monday. A weak front is progged to move south from
the Ohio River Valley region into the Tennessee Valley region from
Tuesday into Wednesday and may become positioned across our northern
counties by Thursday next week.
Forecast:
Shower and storm chances will be lowest on Saturday with isolated
activity across the area as the upper level ridging is in close
proximity to our southeast while height falls will occur to the
northwest.
An increase to scattered activity Sunday through much of the
upcoming work week with the gradual falling heights aloft as ridging
weakens over the area. A weak surface front is forecast to move
south toward the area from the Ohio River Valley Region Wednesday
into Thursday, further supporting higher chances for shower and
thunderstorm activity.
Overnight lows will remain in the mid to upper 60s north and east to
readings in the lower 70s west and southwest. Daytime highs will
remain in the range from the mid to upper 80s north and northeast to
values in the lower 90s south and southwest.
05
&&
.AVIATION...
00Z TAF Discussion.
Currently, there are some scattered showers and storms across
eastern portions of Central AL with a couple lines of strong to
marginally severe storms moving into western AL from MS. These
lines of storms should eventually merge and continue eastward
across the western half of the forecast area. Visibilities may be
reduced briefly due to heavy rainfall. There`s still some
uncertainty as to when the line(s) break up/dissipate so have only
carried VCTS at ANB/ASN/MGM/TOI for now. Amendments may be needed
throughout the evening.
Most of the current activity should dissipate or move out of the
area by 06Z, with only some isolated activity possible in the
north overnight. Widespread fog development is not anticipated,
and ceilings should remain VFR through the period.
19
&&
.FIRE WEATHER...
Tropical moisture will keep humidity and rain chances quite
elevated through this evening with scattered to numerous showers
and thunderstorms expected, particularly during the afternoon and
early evening. Winds remain light and variable this morning though
favoring the southwest and becoming 5-10 mph by the afternoon.
Rain chances decrease somewhat by Friday and into the weekend,
though minimum RH values remain above 50-60% with at least
scattered rain activity forecast each afternoon.
&&
.PRELIMINARY POINT TEMPS/POPS...
Gadsden 68 86 66 86 67 / 50 40 10 30 20
Anniston 68 86 68 87 68 / 50 40 10 30 20
Birmingham 70 88 70 88 71 / 60 40 10 30 20
Tuscaloosa 69 88 70 87 71 / 90 30 10 30 20
Calera 69 87 68 87 69 / 70 30 10 30 20
Auburn 68 86 69 88 69 / 50 20 10 20 20
Montgomery 70 89 70 90 71 / 60 20 10 20 10
Troy 70 91 70 92 71 / 60 20 10 20 10
&&
.BMX WATCHES/WARNINGS/ADVISORIES/...
None.
&&
$$
Area Forecast Discussion
National Weather Service Denver/Boulder CO
546 PM MDT Thu Jun 25 2020
.SHORT TERM...(This evening through Friday)
Issued at 324 PM MDT Thu Jun 25 2020
Becoming a relatively active thunderstorm afternoon day across
Colorado, but so far storms are mainly on the weaker side with
impacts of strong winds, brief rain and possibly some small hail.
Surface dewpoints have mixed out into the 30s across the urban
corridor and mainly 40s over the Eastern plains resulting in
surface based CAPE generally under 1000j/kg. Storms will be
outflow and boundary driven this afternoon with one convergence
boundary draped across Lincoln and Washington counties, while
several outflow boundaries have worked southward out of Weld and
Larimer counties. Expect most storms to be under severe limits but
can`t rule out a few severe storms with high winds over the far
eastern zones.
For tonight, a weak cold front will move southward across the plains
from 04-07z as winds shift to the north. Increasing low level moisture
is expected behind the front and even some possible low stratus late
tonight through Friday morning. A few showers and storms may
still be ongoing given some frontal lift expected until later tonight.
For Friday, temperatures will be cooler behind the front with
high temperatures around 80 degrees. The big question will be how
much thunderstorm activity we get and the potential for strong or
severe storms? Latest NAM soundings show very stable airmass and
strong inversion 700mb until late afternoon and then most storms
will be confined to elevated terrain of the Palmer Divide with
near zero chances over Denver. The high resolution HRRR on the
other hand is rather bullish and sending a whole line of
convection marching from west to east over the whole plains after
19z. This seems excessively bullish and think it may take a while
for convection to get going on the plains. For now will play a bit
in the middle but focus the higher pops over higher terrain and
for a mid/late afternoon target time of initiation. If and when
storms do fire there will be ample CAPE of 1500j/kg and sufficient
mid level flow for a few severe storms with damaging winds and
hail the main threats. Moisture levels also are up with
precipitable water values progged to be around an inch by late
afternoon over much of the plains.
.LONG TERM...(Friday night through Thursday)
Issued at 324 PM MDT Thu Jun 25 2020
Model discrepancies continue Friday night as the wave of
convection pushes east across the plains. Will keep the chance to
likely PoPs across the plains during the evening and then exit it
out after midnight. There still may be some lingering storms over
the far corner into the early morning hours. Storms during the
evening will continue to have the possibility of being strong to
severe, east of a line from Cheyenne to Last Chance. A surface
lee trough will begin to develop along the urban corridor
overnight to flush out the higher dewpoints to the east.
The upper trough over Utah and down into Arizona Saturday morning
will move east over the state Saturday. Look for slightly drier
and slightly warmer conditions across the area, with another round
of afternoon and evening thunderstorms. Could still see some
strong storms over the far eastern plains, as CAPES will be
1000-2000 J/kg, depending on whether you`re following the weaker
GFS or stronger NAM. Hail and strong outflow gusts would be the
main issues.
Sunday temperatures will be increasing as flow aloft turns
southwesterly from a large Pacific trough dropping into the Great
Basin. Afternoon and evening storm coverage will be less, as well
as the strength as the best moisture moves north and east. Likely
will only see a few isolated storms over the high country and that
is it. The upper trough will slow its movement Monday before it
starts to lift northeast. Temperatures will likely stay similar to
Sunday`s readings, and moisture will slightly increase, but still
staying isolated to scattered in coverage mainly over the high
terrain. The bigger concern will be fire weather as southwesterly winds
will be increasing as the jet ahead of the upper trough moves
overhead.
Tuesday should be cooling as the upper trough will move overhead
and bring lower heights. Better storm coverage but weak winds
aloft will result in better chance for wetting rains.
Northwesterly winds on the backside of the trough Wednesday should
bring even cooler temperatures with more shower and storm
coverage.
Upper ridging will then move up from the south for the rest of
the work week for warmer and drier conditions.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 541 PM MDT Thu Jun 25 2020
Afternoon showers and thunderstorms have died out, with another
round in the mountains to move out to near TAF sites before
sunset. Multiple colliding outflow boundaries make wind forecast
difficult, with low confidence in wind direction through this
evening. Toward 05-06z timeframe a weak front will shift wind
around to the north for a few hours, then return to south then
east. Potential for MVFR cigs in the 08-12z timeframe, then
improving to VFR after 12z. Afternoon showers and thunderstorms
on Friday again, with variable wind and gust potential to 20 to 30
kts.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...Entrekin
LONG TERM...Kriederman
AVIATION...Hanson
Area Forecast Discussion
National Weather Service Boston/Norton MA
1009 PM EDT Thu Jun 25 2020
.SYNOPSIS...
Dry weather and comfortable humidity levels are anticipated
most areas tonight. A few showers/thunderstorms will be possible
tonight into Friday, but dry weather will dominate. A warm
front brings higher humidity levels Saturday with rain in the
morning, then a potential for scattered stronger thunderstorms
Saturday afternoon. Less humid Sunday, but with pop up showers
and thunderstorms near the terrain, dissipating after sunset.
Turning cooler with daily rain chances into midweek, but not
expecting a washout on any one day.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
No major changes to the ongoing forecast this evening. Minor
tweaks to timing for showers across southern New England
tonight. Also brought temperatures back in line with observed
trends.
720 PM Update...
Made some minor adjustments to the going forecast to sharpen
timing of onset of cloudiness/showers towards the South Coast
and Cape Cod/Islands.
Though generally quiet for most, there are two main focus areas
tonight for shower possibilities: one is across a small area in
northwest MA stemming from weakening heavy showers/storms over
the Catskills into east-central NY. These storms are moving out
of the better convective instability, which are also waning with
daytime heating coming to an end. Most-unstable CAPE values
decrease markedly with eastern extent with T-Td spreads some 30
degrees. Did increase sky cover in western MA thru 02z - light
showers could briefly clip areas such as Hawley, Charlemont and
Rowe but expect that by mid evening this threat is over. Didn`t
think the chances necessarily are great enough to warrant
mentionable PoP for this small area. The other area, with
somewhat better prospects for showers, is after midnight and
early-Fri AM towards the South Coast, parts of southeast MA and
the Cape mainly S of Highway 44. Guidance seems to want to bring
the cluster of showers/storms now over the Jersey Shore
northeast ahead of the trough aloft. Dewpoints rise enough
associated with this that CAPE values on the RAP accordingly
rise around 500-750 J/kg; not terribly unstable, but enough to
include isolated thunder or rumbles thereof for these areas. Dry
conditions elsewhere with prospects for radiation fog nil.
Lows will range from the mid to upper 60s across southeast and
east MA into a good part of central and southern RI and the
Hartford area. Upper 50s to lower 60s across the remainder of
the interior.
Previous discussion...
Shortwave from the Great Lakes sweeps east and approaches New
England. The supporting upper jet remains over the region
through the night with the right entrance region over Southern
New England. Cold advection at 500-mb helps destabilize the
airmass. Surface dew points increase during the night. Put it
all together...it`s not terribly impressive, but enough to
support scattered showers during the overnight. Stability
parameters suggest a parallel chance of thunder.
Aside from the scattered showers, a dry night. Dew points in
the upper 50s to mid 60s...so expect min temps in the upper 50s
and 60s.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
Friday...
The shortwave and colder air aloft move through during the
morning, then move off to the east in the afternoon. A second
shortwave then moves through during the mid-late afternoon. The
morning shortwave will be supported by cold air destabilization
and a deeper moist column. The afternoon shortwave will pass
while the temps aloft are starting to warm, the moist layer is
relatively shallow, and cross sections show dry air below 850
mb. Stability parameters continue to suggest a chance of
thunder.
The forecast will show clouds and scattered showers/tstms over
Eastern MA and parts of RI during the morning. Diminishing
clouds in the afternoon.
The mixed layer Friday reaches to 800 mb or above. Temperatures
at 800 mb are forecast at 8-10C, equiv to 13-15C at 850 mb.
That suggests max sfc temps again in the 80s. The pressure
gradient will be weak enough to allow afternoon sea breezes
again along the coast.
Friday night...
Shortwave ridge moves overhead during the night, bringing a dry
period much of the night. Another shortwave moves from the
Great Lakes, bringing more lift late at night. Expect increasing
clouds at this time. The GFS brings showers into western and
central MA between 5 and 8 AM, while the GGEM and ECMWF keep the
showers over NY state through 8 AM. The forecast follows the
slower onset, with dry weather past sunrise early Saturday.
Increasing clouds should keep min sfc temps will be in the
upper 50s to mid 60s.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
Highlights...
* Warm front brings period of rain/possible embedded thunder
first part of Sat. Turning more humid, with possible
strong/severe storms late Sat into early Sat night pending
clearing of clouds.
* More sun on Sunday with a little less humidity, but with
scattered diurnal showers/storms Sunday afternoon. Isolated
/limited-coverage stronger storms possible, best chance near
terrain and in the coastal plain.
* Turning cooler than normal for early next week with daily rain
chances, though not a washout on any particular day.
Details...
Saturday into Saturday Night:
An initial 500 mb shortwave trough/vort max associated with a
surface low and related warm front in the west flow aloft moves
through Southern New England during the day on Saturday. This
will likely spread a round of showers, perhaps embedded with
thunder due to the progged strength of the shortwave, during the
first part of the day. Model spread still remains considerable
on timing higher PoPs, with the GFS on the faster side and the
international suite of guidance as well as the NAM being
somewhat later, closer to mid- morning to early-afternoon.
Ironing out those details will be critical to the potential for
afternoon warm-sector strong to possibly severe storms, and more
specifically on if/how quickly can warm-frontal cloudiness
clear for any afternoon heating and destabilization. Across all
models, 700-500 mb lapse rates are progged to be around 5.5-6.0
C/km, values which are fairly low and would limit potency of
updrafts. Because the GFS brings precip in earlier than other
guidance, it allows for greater cloud breaks than the other
models, with progged CAPEs on the order of 2000 J/kg away from
the coast. On the other hand, only a few hundred J/kg of CAPE is
depicted in the other solutions, with greater progged
instability over the lower Hudson Valley into western sections
of MA/CT. Effective layer wind shear values are in the 35-40 kt
range and would support storm organization and persistence were
storms to develop. Current SPC Outlook for Saturday (as of this
writing), Marginal Risk/5% severe probs over Southern New
England with the Slight Risk/15% to our west, still seems
reasonable. If greater cloud breaks were to materialize sooner,
supporting a more unstable GFS stability depiction, then a
greater coverage of stronger storms could ensue but seems too
conditional at this time. As PWAT values rise to around 1.8-2",
any thunderstorm would be capable of downpours but storms would
be moving along at a fair clip. With current preference towards
the NAM and international guidance on timing PoPs/sky cover,
will be siding temperatures on the lower end of guidance - but
greater cloud breaks would allow for significantly warmer
temperatures. It will be quite humid though with dewpoints in
the mid to upper 60s.
Leftover showers or storms may linger Should have clearing by
mid- evening with some potential for patchy fog in the favored
spots.
Sunday into Sunday Night:
Troughing associated with the Quebec/eastern Ontario upper low
builds southward into Southern New England later Sunday into
early Sunday night. After the cloudier day anticipated for
Saturday, will have considerably less cloudiness and stronger
daytime heating on Sunday. With stronger heating, there`s a
better chance of realizing the 1000-2000 J/kg of CAPE progged
for Sunday on the GFS/NAM, with effective shear values around 30
kt. However with westerly flow there is less of a triggering
mechanism outside of the terrain and perhaps in the coastal
plain on the western side of sea breezes. There`s drier mid-
level air on Sunday that could lead to lower dewpoints and
somewhat less instability than models depict. Will continue to
carry mention of thunder in the forecast for Sunday, with better
chances in the interior and into the coastal plain. Still could
have a few stronger storms on Sunday given forecast
instability/shear parameters but the coverage may be limited by
a lack of stronger forcing mechanisms.
Any showers or storms should start to diminish in strength and
coverage by evening. Dewpoints to slowly fall into the upper 50s
to lower 60s, so also turning a little less humid.
Early Next Week:
Closed upper low over northern parts of ME/NH by 12z Monday
projects to be the dominant driver of weather conditions really
into a good part of next week. This upper level feature shifts
southeast towards the southern ME coast by Tuesday and continues
to at least be in the vicinity of Southern New England into
Wednesday. While there are no days which appear to be a washout,
scattered diurnal showers, possibly a rumble of thunder will be
around. Cloud cover will tend to increase a little more on
Wednesday as upper low starts to dig southward through Southern
New England into the mid-Atlantic region.
Temperatures will start to trend near to slightly cooler than
normal with modest onshore flow. Most days will feature highs in
the mid 70s to near 80 and lows in the lower 60s, with
dewpoints in the upper 50s to lower 60s - noticeable humidity
levels but still generally comfortable.
&&
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent. Moderate - 30 to 60 percent. High -
greater than 60 percent.
00z TAF Update:
Tonight: High confidence.
Generally VFR for most of the TAFs. Approaching disturbance
aloft may bring ongoing showers/storms toward the South Coast,
Cape and Islands tonight. Possible short-lived MVFR visibilities
in showers, from PVD-PYM southeast towards the Cape and the
Islands. Carried as VFR showers for now with TEMPOs as needed.
WSW-SW winds 4-8 kt.
Friday...High confidence
VFR. Widely scattered showers and thunderstorms possible across
RI and eastern MA, best chances generally within a few miles
either side of I-95. SW winds around 5 to 10 kts.
Friday night... High confidence.
VFR with light wind.
KBOS Terminal...High confidence in TAF/trends. Sea breeze
around 16z Fri, possible SHRA/-TSRA ~16-20z.
KBDL Terminal...High confidence in TAF/trends.
Outlook /Saturday through Tuesday/...
Friday Night: VFR.
Saturday: Mainly MVFR, with areas VFR possible. Breezy. SHRA
likely, slight chance TSRA.
Saturday Night: Mainly VFR, with areas MVFR possible. Breezy.
Slight chance SHRA, isolated TSRA.
Sunday: Mainly VFR, with areas MVFR possible. Chance SHRA,
isolated TSRA.
Sunday Night: VFR.
Monday: Mainly VFR, with areas MVFR possible. Slight chance
SHRA.
&&
.MARINE...
Winds and seas generally remain below Small Craft Advisory
thresholds. Seas may approach 5 feet on the eastern outer waters
Friday afternoon and evening.
Widely scattered showers/thunderstorms late tonight into Friday
with slight lowering of visibility.
Outlook /Saturday through Tuesday/...
Friday Night: Winds less than 25 kt. Seas locally approaching 5
ft.
Saturday: Winds less than 25 kt. Areas of seas approaching 5
ft. Chance of rain showers, isolated thunderstorms.
Saturday Night: Winds less than 25 kt. Seas up to 5 ft. Chance
of rain showers, isolated thunderstorms.
Sunday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Chance of rain showers, isolated thunderstorms.
Sunday Night: Winds less than 25 kt. Areas of seas approaching
5 ft.
Monday: Winds less than 25 kt. Seas locally approaching 5 ft.
Slight chance of rain showers.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.
&&
$$
SYNOPSIS...WTB/Loconto
NEAR TERM...WTB/Belk/Loconto
SHORT TERM...WTB
LONG TERM...Loconto
AVIATION...WTB/Belk/Loconto
MARINE...WTB/Loconto
Area Forecast Discussion
National Weather Service Caribou ME
912 PM EDT Thu Jun 25 2020
.SYNOPSIS...
An upper low will drop southward from Canada over the weekend
into early next week with a series of upper level disturbances
affecting the region.
&&
.NEAR TERM /THROUGH FRIDAY/...
9:12 pm Update: Satellite pictures show an upper low to the
east of James Bay with mid level water vapor showing drier air
across Maine. This dry air was evident on the KCAR 00z sounding
with a PWAT of 0.80" which compares with a PWAT of 1.89" this
time last night. There are still a few showers ahead of the
upper low in eastern Quebec, although no lightning has been
detected all evening. Will make some adjustments to cut back on
the PoPs, not that they were any higher than isolated, but even
that looks like it can be trimmed back for the remainder of the
night. Otherwise, the forecast remains on track with a much
drier air mass at low and mid levels across the area and a much
more comfortable night. Lows by morning will mostly be in the
50s, and even some 40s are possible in the normally colder
northwest valleys.
Previous discussion:
An upper trof seen on the 12Z UA was moving into Quebec. This
feature is picked well on the visible and wv satl imagery. A
nice 35-40 kt jetstreak is associated w/this feature. RAP
soundings do show the column moistening up to 700mbs this
evening across far northern and western areas. The RAP and HRRR
have been consistent w/bringing some light showers across the
far northern areas during the evening hrs up through midnight.
Decided to go w/20-30% pops and just showers. Much cooler
overnight w/temps in the 50s. The exception will be across far n
and nw areas w/some upper 40s. SW winds will be dropping off
this evening as the gradient weakens. Some fog is possible
overnight especially across the Downeast coast. The latest RAP
and NAM support the fog development. Across northern areas,
there is potential for some patchy fog w/the cooldown and
temp/dewpoint being w/in few degrees.
Fog that is around in the morning, will quickly dissipate. A
sfc trof/pre-frontal boundary is forecast to slide into the
region late Friday morning into the afternoon. Dewpoint pooling
along and just ahead of the boundary is noted by the 12z NAM and
even the GFS. The best moisture convergence appears to be across
the interior Downeast nosing up into Nrn Washington and SE
Aroostook County. Mdl soundings show SB CAPE 500-900 joules in
this area. Mid level lapse rates are marginal, but llvl lapse
rates are shown to hit 8.0 c/km which would aid in allowing for
buildups. PWs around 1.0". 0-6KM shear is around 20 kt which
should be enough to allow for convection to fire and keep going.
Inverted sounding supports potential for some gusty winds w/any
tstms. Attm, confidence is not high enough to include any
enhanced wording in the forecast. Afternoon temps should be able
to hit 80 and higher across the region w/the warmest temps
across the Maine Central Highlands down to the Downeast region.
&&
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
Large upper low just east of James Bay Friday night gradually
drifts to over Maine late Sunday. As this upper low approaches,
it will send several shortwave troughs through our area with
shots at showers and storms.
One shortwave trough will be exiting to the east Friday evening,
thus expect showers and storms to die off quickly after dark.
Enough of an onshore component that there should be some fog
again mainly Downeast but possibly up to Houlton and
Millinocket.
Later Saturday, another shortwave trough approaches. Dynamics
could be strong enough to allow a weak surface low to form near
the Maine coast, and if this happens, could see some rain. Not a
done deal though. Raised PoPs to around 60 percent Downeast late
Saturday and Saturday evening. High chance to low likely PoPs in
Northern Maine late Saturday with perhaps some storms as well.
Then late Sunday the upper low nears the area and with the
colder air aloft, should see an increase in showers and storms
again. With the colder air aloft with the upper low, could be a
good setup for small hail. Not as warm with highs in the 70s.
There are some slight differences with model timing of
shortwaves, but nothing major and overall fairly confident in
the forecast.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Tough call Monday and Tuesday what happens to the upper low
after being over us late Sunday. Tentatively, it looks like it
will weaken a bit and drift slowly SW of the area. Enough cold
air aloft and instability Mon/Tue that kept a mention of thunder
those days, though coverage probably will be less than Sunday.
Pleasant temps Mon/Tue with highs in the 70s. Models in poor
agreement on what happens after Tuesday. Some build a decent
upper ridge in from the NW with a similar warm blocking pattern
to what we had a week ago, while others keep us under unstable
NW flow.
&&
.AVIATION /01Z FRIDAY THROUGH TUESDAY/...
NEAR TERM: VFR from KBGR northward. Some IFR cigs are possible
at KBHB overnight into the early morning hrs on Friday.
SHORT TERM:
Friday Night...Mainly VFR except for some IFR with fog Downeast.
Light wind.
Saturday through Sunday Night...Mix of VFR and MVFR. Generally
MVFR outside of showers and storms, but MVFR in showers and
storms which are possible through the period. Fairly light wind.
Monday and Tuesday...Mainly VFR with light wind.
&&
.MARINE...
NEAR TERM: No headlines. The main deal will be the fog over the
waters developing overnight into Friday morning causing some
navigation issues for the mariners. SSW winds around 10 kts
w/seas 2-3 ft, building to 3-4 ft.
SHORT TERM: Pretty quiet on the waters with seas and winds below
small craft. Main issue will be some fog lingering into Saturday
night.
&&
.CLIMATE...
Today was the 10th consecutive day with a high of 80 degrees (F)
or warmer in Caribou, Maine. This ties with August 2015 for the
longest consecutive stretch of 80 degrees on record. Weather
records in Caribou date back to 1939.
&&
.CAR WATCHES/WARNINGS/ADVISORIES...
ME...None.
MARINE...None.
&&
$$
Near Term...CB/Hewitt
Short Term...Foisy
Long Term...Foisy
Aviation...CB/Hewitt/Foisy
Marine...CB/Hewitt/Foisy
Climate...
Area Forecast Discussion
National Weather Service Cheyenne WY
933 PM MDT Thu Jun 25 2020
.UPDATE...
Issued at 933 PM MDT Thu Jun 25 2020
It was a active late afternoon and early evening with scattered
strong to severe thunderstorms over parts of southeast WY and
western NE. The most intense convection developed over northeast
Sioux and western Dawes counties, with several reports of 2 to 3
inch diameter hail in and around Crawford NE. Wind gusts of 58 mph
were measured at Douglas WY. A cold front was moving south across
the I-80 corridor this evening. Winds shifted to northerly and
were gusting to 35 kt with fropa. Behind the front, scattered
showers and isolated thunderstorms lingered. The threat for strong
convection has ended, however brief heavy rain and gusty winds
will be possible through late this evening. Shower coverage will
decrease overnight.
&&
.SHORT TERM...(This evening through Saturday night)
Issued at 210 PM MDT Thu Jun 25 2020
Tonight...The Storm Prediction Center slight risk outlook from
Glenrock to Chugwater to Sidney looks good based on best instability
axis and shear outlook. Approaching shortwave trough aloft will help
generate scattered to numerous showers and thunderstorms through the
afternoon and early evening as depicted on the HRRR model, with
strong winds the primary threat, along with a secondary threat for
large hail. Storms will be slow to decrease in areal coverage
overnight.
Friday...Best chances for afternoon and evening showers and
thunderstorms will shift to our southern counties where moisture and
lift will be most pronounced. Shear and instability look less
favorable for strong to severe thunderstorms. Cooler temperatures in
the wake of a cold front and with more cloud cover.
Friday night...Showers and thunderstorms will decrease in areal
coverage in the evening with the loss of daytime heating.
Saturday...With a low level trough axis expected from Casper to
Cheyenne, and adequate low and mid level moisture remaining, will
see isolated to scattered afternoon and evening thunderstorms mainly
south of a Wheatland to Alliance line. Warmer temperatures as 700 mb
temperatures rise to near 15 Celsius.
Saturday night...Showers and thunderstorms will likely end quickly
in the early evening. Not as cool as Friday night with the warmer
airmass in place.
.LONG TERM...(Sunday through Thursday)
Issued at 210 PM MDT Thu Jun 25 2020
Attention this period will be on the upper trough/low that will be
over the northwest part of the country, weakening slowly through
mid-week. Convection looks to be rather isolated over the CWA
Sunday behind a weak shortwave that will be moving east of the
area. It then appears convection will gradually increase over the
CWA Monday through Thursday as the upper trough edges a little
closer to the CWA with several weak impulses likely to lift
northeast and over the region on the front side of the trough. A
cold front should pass across the CWA Tuesday which would aid in
convective development. Less convective activity seen for Thursday
as the weakening trough axis moves across the area.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday afternoon)
Issued at 535 PM MDT Thu Jun 25 2020
VFR will prevail through the period. Scattered SHRA/TSRA will move
across the region through late this evening. Gusty erratic winds and
brief MVFR visibilities can be expected with the stronger convection.
&&
.FIRE WEATHER...
Issued at 210 PM MDT Thu Jun 25 2020
Minimal concerns for Friday based on expected afternoon relative
humidities. Lower humidities Saturday through Monday will increase
concerns.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
UPDATE...MAJ
SHORT TERM...RUBIN
LONG TERM...RE
AVIATION...MAJ
FIRE WEATHER...RUBIN
Area Forecast Discussion
National Weather Service Grand Forks ND
1010 PM CDT Thu Jun 25 2020
.UPDATE...
Issued at 1010 PM CDT Thu Jun 25 2020
Cold front is still moving into our CWA with warm sector slowly
sliding east. ML CAPE within warm/moist air mass is still within
1000-2000 J/KG according to SPC RAP analysis, with much lower
values 500 J/KG or less behind the front. Effective shear and
DCAPE are both very low. This type of air mass no longer supports
organized severe weather, though small hail can`t be ruled out
with any storms that develop. Beside frontal zones large scale
ascent is disorganized and as stable post frontal air mass
spreads east we would expect any shower/storm potential to end,
which is matched by current CAMs/radar trends. I lowered coverage
of showers/storms and adjusted timing for activity ending around
midnight in ND and around 09Z in MN based on observed and expected
trends. Patchy fog may develop for a brief period as moisture
pools near the frontal zone in MN late tonight/Sunday morning,
but the window for this is brief as front moves east and coverage
likely patchy.
&&
.SHORT TERM...(This evening through Friday night)
Issued at 344 PM CDT Thu Jun 25 2020
Convective chances and strength continue to be the forecast
challenge for the period.
The festivities have gotten an early start as the surface trough
axis enters the Devils Lake and James river valleys. Warm front
has been lifting across our central CWA with the cold front
further west over central ND. While there were worries about how
much we would destabilize due to clouds and early showers, there
has been a lot of clearing across the southern RRV and ML CAPEs
have managed to top 2000 J/kg. While the effective bulk shear is
not huge, up to 35 kts has been sufficient enough for several
supercells and multicells to develop early this afternoon. The
storms will push eastward into far western MN late this afternoon
and evening, with some weakening expected as the storms move into
more stable air. Will have to watch additional development in
south central ND that will push into our counties later tonight,
as there could be additional marginally severe cells as the front
moves eastward. Think that most of our severe threat should be
over by late evening, with the loss of daytime heating and winds
shifting to the northwest behind the low pressure system.
Later tonight, lingering showers and a few thunderstorms should
taper off, with portions of the western CWA clearing out. Clouds
will clear out of the rest of the region during the day on Friday,
with northwesterly flow aloft and surface high pressure building
in. Cold air advection behind the system is pretty weak and will
be offset by sunshine that some areas are not getting today, so
highs will be in the 80s across much of the CWA. The fairly quiet
weather will continue into Friday night with brief upper ridging
between systems.
.LONG TERM...(Saturday through Thursday)
Issued at 344 PM CDT Thu Jun 25 2020
Impactful weather opportunities will still be found during the
latter part of the extended period, principally during Tue-Thu
when strong to severe tstms will be possible.
Upper flow will transition from zonal to an upper ridge during the
weekend, allowing for warmer temps and dry conditions. Look for
highs in the mid 80s to low 90s during this time, with overnight
lows mostly in the balmy 60s.
A more southwesterly regime kicks in for late weekend into early
next week. An upper low will transit into the Northern Rockies at
this time, edging closer to the Northern Plains. PWATS will be on
the rise along with instability, but an inspection of 700mb ensemble
temp projections indicates a potentially stout cap in place, at
least for Mon. The approach of an upper wave/500 mb trough by Tue
could provide the de-stabilization/forcing necessary for organized
strong to severe convection. There is a decent chance though that
this approach could be delayed until Wed, making Wed/Thu the better
days for more focused convective activity.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 705 PM CDT Thu Jun 25 2020
Clusters of showers/thunderstorms continue to track over west
central/northwest MN with brief IFR/MVFR conditions where heavier
rain showers or thunderstorms track. Most activity isn`t severe
but we can`t rule out stronger storms through 03Z. Further west
west in ND activity as actively transitioned east with only one
lingering storms near KFAR which should move east around the valid
TAF time at 00Z. After a lull additional scattered showers/storms
should develop back into eastern ND and northwest MN as a cold
front shifts east before lingering showers/storms ends 06-07Z in
MN. There is still some guidance that shows potential for MVFR
conditions across MN 10-15Z period, but with westerly flow
arriving behind cold front this may support clearing and trends
toward prevailing VFR.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
$$
UPDATE...DJR
SHORT TERM...JR
LONG TERM...JR
AVIATION...DJR
Area Forecast Discussion
National Weather Service Goodland KS
605 PM MDT Thu Jun 25 2020
.SHORT TERM...(This evening through Friday Night)
Issued at 102 PM MDT Thu Jun 25 2020
19 UTC Water vapor imagery and RAP analysis indicated short wave
trough axis bisecting the CWA with some pronounced
drying/subsidence noted near its axis. At the surface, storms
starting to develop behind the upper level feature along surface
trough from KIML to KLIC, in area of persistent convergence. To
the south of the trough, very warm conditions dominated with
temperatures in the upper 90s to low 100s.
Main forecast concerns are going to be thunderstorm chances
through the evening, followed by another round on Friday evening.
Thunderstorms have already initiated along surface trough just to
the west of the area. With high LCL`s weak overall shear and
MLCAPES between 500-1500 j/kg, not expecting to see very
organized storms. However, the high LCL`s and dry inflow air will
likely create strong downdrafts which will pose a microburst
threat as well as allow a strong cold pool to form and further
initiate storms downstream across the CWA. Convective allowing
models all seem to be following this evolution which increases
confidence. The combination of strong winds,high cloud bases and
lots of evaporation may increase the risk of lightning induced
fires, although there is a lot of uncertainty with respect to how
much precipitation will reach the ground.
Cold front will sweep across the area overnight and may bring a
brief period of gusty winds, although current timing and pressure
rises estimates seem to indicate winds will not get out of hand as
it passes.
Will likely see little if any precip chances through the day
Friday as cooler air builds into the area shifting instability
axis to the south of the area, with capping very strong to the
north of front even if instability present. Think the most likely
scenario will be thunderstorms developing in the easterly flow
behind front along higher terrain. Shear profiles certainly
support organized storms and with the 0-3km shear orientation and
likelihood of strong cold pools, expect MCS to roll across the
area during the evening hours, perhaps bringing an organized
damaging winds threat.
.LONG TERM...(Saturday through Thursday)
Issued at 212 PM MDT Thu Jun 25 2020
For the extended period, the models start out showing the Plains
being between an upper air trough and ridge on Saturday due to an
localized upper air low over UT/NM. During this period, a shortwave
trough will move through the local area. On Sunday, models both show
an upper level low traveling in from Pacific Northwest U.S. while
another upper level low persists in the Northeastern U.S. This setup
causes an upper air ridge to reside over the Plains for the
beginning of next week. The GFS model shows the Pacific Northwest
low moving more southeastward on Tuesday evening causing a
negatively tilted upper air trough to move over the CWA. However,
the ECMWF model keeps the low in the Pacific Northwest making this
trough stay more over the Rockies and starting to tilt negatively by
Thursday. This situation will be monitored as the timing of the
middle of next week`s weather system relies on how this plays out.
On the surface, a chance of showers and thunderstorms are expected
on Saturday in the CWA due to the shortwave trough aloft. For the
beginning of next week, dry conditions are expected throughout the
CWA. However, isolated showers and thunderstorms cannot be ruled
entirely at this time Sunday and Monday. Chances of showers and
thunderstorms return Tuesday evening and these chances increase on
Wednesday across the CWA. Thursday`s forecast also shows a slight
chance of showers and thunderstorms. Fire weather also cannot be
ruled out entirely for the western counties of the CWA for Sunday
through Tuesday as forecasted RH values begin to drop Sunday below
20% with models show wind gust speeds expected to reach up to 25 mph.
Saturday`s high temps for the CWA are expected to be in the lower
90s as precipitation cools things in the area. Sunday and Monday
should see a return of highs reaching the upper 90s across the CWA
with some parts hitting possibly 100 degrees. Middle 90s are the
expected Tuesday`s high temps. Wednesday and Thursday`s high temps
for the CWA will return to the upper 80s and lower 90s as
precipitation cools the area. Overnight low temps are forecasted to
stay in the upper 50s to middle 60s for the western counties of the
CWA throughout the forecast period with the eastern counties of the
CWA low temps ranging from the lower 60s to lower 70s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 600 PM MDT Thu Jun 25 2020
For KGLD, vfr conditions expected through the period. Winds will
veer to the northwest at speeds around 10kts after midnight as a
cold front moves through. Winds continue to veer to the north with
gusts around 20kts from shortly after sunrise through late morning
then decrease below 12kts and veer to the northeast and east
through the afternoon.
For KMCK, ongoing thunderstorms at taf issuance will move east of
the terminal by 01z with isolated to scattered showers producing
erratic wind gusts to 40kts through about 02z. After 03z a similar
scenario as KGLD regarding timing and winds after midnight through
the day Friday.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
SHORT TERM...JRM
LONG TERM...MRC
AVIATION...99
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
837 PM CDT Thu Jun 25 2020
.UPDATE...
837 PM CDT
No changes to the going forecast this evening.
Weak lake breeze across parts of the Chicago metro area will
dissipate through late evening, with winds becoming light
southwest across the region overnight ahead of a warm front which
will move into the area Friday morning. Warm advection will
strengthen aloft overnight ahead of the front, with isentropic
ascent and moistening eventually allowing the development of
scattered convection from west central IL back into central and
eastern IA after midnight. Recent high-res CAM guidance continues
to indicate elevated showers/thunderstorms spreading into the cwa
toward/sunrise Friday morning, with western parts of the forecast
area seeing higher potential prior to gradual weakening as
activity moves farther east after sunrise. Light southwest surface
winds and gradually increasing low level moisture/dew points will
allow for milder overnight temps in the low-mid 60`s in most
spots.
Recent CAM guidance continues to suggest the potential for
additional thunderstorm development across parts of northern IL by
late morning/midday, in association with a convectively enhanced
(from MCS activity across the Plains to our west tonight)
circulation or MCV. Increasing chance pops north of the I-80/88
corridors across northern IL by midday in going forecast appear
reasonable based on this scenario. MCS evolution overnight should
allow for further refinement in temporal/spatial distribution of
thunder chances.
Ratzer
&&
.SHORT TERM...
256 PM CDT
Through Tonight...
Most of tonight will be quiet and milder. After midnight and
especially toward daybreak, warm advection/isentropic ascent on
the nose of a modest veering low level jet is expected to cause
scattered higher based convection to break out from central
Illinois to northwest Illinois after midnight and then gradually
spreading northeast toward and after daybreak. Main short-wave
forcing passing to the north, relatively dry profiles, fairly weak
mid- level lapse rates, and resultant minimal elevated instability,
should keep coverage and intensity in check. That said, there
should be enough MUCAPE (250-500+ j/kg) to tap into above capping
around 650 mb to allow for some isolated to widely scattered
thunderstorms. Not expecting severe weather due to the modest
instability despite decent deep layer shear.
Castro
Friday through Saturday Night...
An active Friday and Friday night is expected across the Great
Lakes region, including both a scattered severe thunderstorm and
potential zone of a flash flood threat. Confidence is highest in
thunderstorms occurring along and north of I-80 late day into the
evening. This area thus has a greater potential for severe
weather and heavy rain than south of I-80 in an otherwise
background Slight Risk (Level 2 of 5).
Scattered showers and probably some storms should be ongoing
Friday morning in the warm advection across southern Wisconsin
and northern and possibly central Illinois. These will be on the
leading edge of stronger elevated instability shifting eastward.
As noted above, the instability is not forecast to be particularly
robust, but the 2-6 km shear of 30 kt may yield a couple stronger
storms.
A positively-titled upper level short wave presently over eastern
Montana will be a key forcing feature for later Friday as it
translates east-southeast in the upper level westerlies. An
ongoing MCS or convective clusters by midday across central to
southern Wisconsin will likely be intersected by this wave`s
forcing. The signal in 12Z guidance is fairly pronounced for
upscale convective growth as an MCS along the warm/stationary
front into eastern/southeastern Wisconsin during the afternoon and
into Michigan Friday evening. This is where the greatest
likelihood of severe weather due to organized convective modes and
45-60 kt of deep layer shear is expected, and given the close
proximity there is wiggle room that the MCS threat impinges into
far northeast Illinois mid-afternoon into early evening. More
likely though is that convection develops along the periphery
outflow or composite outflow/front into northern Illinois during
mid or late afternoon. This will align well with peak heating,
with forecast highs near or to 90, and surface dew points along
the boundary to near 70.
There are noteworthy variances in forecast timing though, with
the global solutions much more progressive with the Wisconsin MCS
or developing MCS, thus resulting in its outflow moving more
rapidly southward through the northern half of the CWA during the
mid-late afternoon and evening. This is important because it would
limit the otherwise decent signal for training convection along
the general west-east composite boundary with a moisture feeding
40 kt low-level jet. Those ingredients, along with PWATs of over
1.75 inches, will be plenty for convection and we will need to
monitor closely if a flash flood risk becomes more apparent.
The boundary and/or outflow composite will likely be the focus,
as further to the south and southeast in the warm sector is likely
to be capped through at least early evening. Convective modes of
multicell clusters and small scale segments or bows are favored
with sufficient deep layer shear. The severe threat with this
setup would be primarily wind. If the outflow push from the north
is not as quickly and the boundary(ies) becomes stalled, any
cells along this mainly late day/early eve could have a rotating
supercell threat of hail and a tornado or two.
Activity should slowly be sinking southward Friday overnight into
Saturday morning, likely with a diminishing footprint. Another
lower amplitude short wave is forecast to pass northern to central
Illinois Saturday, interacting with the boundary and instability
to foster thunderstorm chances. This would likely be more of the
scattered thunderstorm variety. The trend continues to support
drying for north of I-80 by later day and Saturday evening/night.
MTF
&&
.LONG TERM...
330 PM CDT
Sunday through Thursday...
Little changes made to this period, with quite a bit of
uncertainty on Sunday and Monday, as the aforementioned frontal
boundary should begin moving northward over the mid-Mississippi
Valley. Heights are also likely to be building though, so that
should limit the amount of thunderstorm coverage especially
further northeast in the region (such as the Chicago area). So
have limited PoPs from what the blend provided during Sunday-early
Monday. Conditions look warm and muggy away from the lake this
coming week.
MTF
&&
.AVIATION...
For the 00Z TAFs...
Aviation forecast concerns:
* Potential for three periods of SHRA/TSRA through Friday evening.
Greatest potential for widespread and likely more impactful TSRA
appears to be Friday evening.
* Strong southwest winds Friday, with gusts 30+ kts possible
especially late afternoon.
Quiet aviation weather is expected to persist through this
evening. Lake breeze has moved inland with east winds at ORD/MDW,
with winds expected to become light west-southwest after lake
breeze dissipates mid-late evening.
Warm front is expected to lift northeast across the forecast area
Friday morning. Elevated convection is forecast to develop ahead
of the warm front late tonight, and spread into northern IL toward
sunrise. KRFD looks to have the highest chance of seeing elevated
SHRA/TSRA around sunrise, with various high-res model guidance
weakening this activity as it moves east through mid-morning.
Can`t rule out a few SHRA making it to the Chicago area terminals,
though coverage is expected to decrease significantly farther
east.
Latest CAM guidance is hinting at another period of potential
convection mid-day, originating from a convectively enhanced
circulation (MCV) which is progged to develop from storms
currently developing across the Plains. Recent runs of the HRRR
maintain scattered TSRA threat across the area into early
afternoon as the mid-level vort passes. As several different
models have picked up on this over the last several hours, feel
it`s worthy of a prob30. Guidance then remains in good agreement
in a more widespread strong thunderstorm threat Friday evening,
ahead of a cold front sagging southeast from WI. Of course any
potential convection and associated cloud cover earlier in the
day may have impacts on the evolution of these trends through late
Friday, though confidence is fairly decent that organized
convection will affect the terminals Friday evening.
Outside of thunderstorms, southwest winds will become strong and
gusty by Friday afternoon after the warm front lifts north of the
area. Forecast soundings support gusts near/above 30 kt during the
afternoon, particularly the late afternoon as 35-40 kt low level
jet develops ahead of an approaching upper trough. Magnitude of
peak gusts may be modulated by earlier convection/residual cloud
cover, so have stayed a bit conservative at this distance, but if
good low level mixing does develop, gusts of 30-35 kts are
possible during the late afternoon hours.
Ratzer
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
LMZ745...1 PM Friday to 10 PM Friday.
&&
$$
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Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
942 PM CDT Thu Jun 25 2020
.NEAR TERM /Now Through Friday night/...An upper trof over the
eastern states moves off into the western Atlantic through Friday
while an upper ridge remains in place over the northern Gulf. A
less well defined upper trof is also currently located from
eastern Texas into southern Arkansas, and remains close to this
position through Friday night. A series of shortwaves are ejected
from this feature and advance eastward (within the westerly flow
north of the Gulf upper ridge) and move across the forecast area
through the period. A surface ridge which extends from the western
Atlantic to along the northern Gulf coast gradually shifts into
the north central Gulf coast states through Friday night. This
results in light southerly surface winds over the forecast area
becoming southeasterly over the southern portion of the area on
Friday with a southwesterly flow expected further inland. For the
remainder of this evening, an area of rain with some embedded
storms will affect the northernmost counties while elsewhere
isolated convection is possible. Have gone with mainly dry
conditions for the late night hours. For Friday, despite the
series of shortwaves set to move across the area, model soundings
show significant drying will have occurred within the 900-650 mb
layer, likely due to subsidence effects from the nearby Gulf upper
ridge. This should be a fairly significant impediment for
convective development though have opted to stay with slight
chance pops for the afternoon hours for now. Lows tonight and
Friday night range from around 70 well inland to the mid to upper
70s at the immediate coast. Highs on Friday will be mostly in the
lower 90s and afternoon heat index values look to be near 100. A
low risk of rip currents is expected from tonight through Friday
night. /29
&&
.PREV DISCUSSION... /issued 621 PM CDT Thu Jun 25 2020/
NEAR TERM UPDATE /Now Through Friday night/...An upper trof over
the eastern states moves off into the western Atlantic through
Friday while an upper ridge remains in place over the northern
Gulf. A less well defined upper trof is also currently located
from eastern Texas into southern Arkansas, and remains close to
this position through Friday night. A series of shortwaves are
ejected from this feature and advance eastward (within the
westerly flow north of the Gulf upper ridge) and move across the
forecast area through the period. A surface ridge which extends
from the western Atlantic to along the northern Gulf coast
gradually shifts into the north central Gulf coast states through
Friday night. This results in light southerly surface winds over
the forecast area becoming southeasterly over the southern
portion of the area on Friday with a southwesterly flow expected
further inland. For this evening, a mesoscale convective system,
manifesting as a broken line of convection, currently located
mainly over south central Mississippi is expected to advance east-
northeastward across interior southeast Mississippi and interior
southwestern Alabama. Some isolated convection will also be
present over south central Alabama this evening. MLCAPE values of
2500 J/kg, possibly higher, will be present initially early this
evening then gradually diminish to 500-1000 J/kg by midnight.
While shear appears to be very low, HRRR model soundings show mid
level dry air near 700 mb which will continue to enhance downdraft
production as the line of convection progresses across the
interior portions of the forecast area. Expect that strong to
marginally severe wind gusts are possible. Have updated to go with
likely to categorical pops early this evening over the
northwestern third of the area due to the convection to move
across this portion and made other minor adjustments. For the
after midnight to pre dawn hours, the potential for any convective
development looks sufficiently limited to continue with a dry
forecast for that time period. For Friday, despite the series of
shortwaves set to move across the area, model soundings show
significant drying will have occurred within the 900-650 mb
layer, likely due to subsidence effects from the nearby Gulf upper
ridge. This should be a fairly significant impediment for
convective development though have opted to stay with slight
chance pops for the afternoon hours for now. Lows tonight range
from around 70 well inland to the mid to upper 70s at the
immediate coast. Highs on Friday will be mostly in the lower 90s.
Lows Friday night range from the lower 70s inland to the mid to
upper 70s at the coast. A low risk of rip currents is expected
from tonight through Friday night. /29
AVIATION...
00Z issuance...Numerous showers and storms will affect interior
southeast Mississippi and interior southwestern Alabama this
evening along with mainly isolated convection expected over south
central Alabama. IFR conditions along with strong wind gusts can
be expected with the convection. Dry conditions are expected over
the entire area by 06Z which continues through early Friday
morning, after which isolated convection is possible. VFR
conditions are expected to prevail outside of the convection
except for the potential for MVFR visibilities mainly due to dust.
Southerly winds 5 to 10 knots at the beginning of the period
become light and variable tonight. For Friday, expect a
southeasterly flow at 5 to 10 knots over the southern portion of
the area while further inland will see a light southwesterly flow.
/29
PREV DISCUSSION... /issued 357 PM CDT Thu Jun 25 2020/
NEAR TERM UPDATE /Now Through Friday/...Forecast for this afternoon
basically on track, isolated showers and thunderstorms are
beginning to develop over portions of interior southwest Alabama.
Current forecast calls for likely PoPs by later this afternoon,
and although coverage may not end up as widespread as originally
thought, mesoscale analysis indicates a quite unstable airmass in
place (MLCAPE 2500-3000 J/KG and areas with SBCAPE up to over
4000 J/KG) so coverage (and intensity) of storms could very well
increase this afternoon. Unlike yesterday though, atmospheric
shear is much lower, so the severe threat is lower (especially
with regard to tornadoes). However, the previously advertised
Saharan Air Layer, and associated dust and dry mid level dry air,
has arrived along the central Gulf coast and the drier air aloft
could result in some stronger downdrafts with the stronger storms
this afternoon. Our microburst checklist procedure came up with a
Moderate threat of downbursts today. Also heating up this
afternoon, a few degrees above expected in some locations, with
heat indices in the upper 90s and even into the 100-105 range in
some locations over the southern third of our forecast area.
For tonight, expect at least isolated to scattered convection to
continue until mid evening, especially over inland areas. By late
evening most of this activity should end, but some lingering
showers or storms could last all night long as the low level airmass
remains moist and weak disturbances continue to move across the
area on the backside of the upper trough that will be departing
off to the east of the area. Lows tonight remaining quite muggy,
mainly in the lower 70s over inland areas and mid to upper 70s
closer to and along the coast.
On Friday, the weather pattern begins to change somewhat as weak
deeper layer ridging begins to develop across our area. Plenty of
low level moisture with a continued east to southeast flow off of
the Gulf (PWATs in the 1.7 to 1.9 inch range), combined with
daytime heating, should allow for some isolated to scattered
daytime showers and thunderstorms, but overall coverage should
continue to be decreased as compared to the last couple of days.
Will continue to be hot and a little hazy (due to the dust in the
air) on Friday. High temperatures will primarily be in the upper
80s and lower 90s across the entire area, with the cooler temps
over the far northwest and also along the immediate coast (where
even a few mid 80s for highs will be possible). Heat indices on
Friday will again be quite warm, mainly in the upper 90s to
100-105 degree range once again. /12
SHORT TERM /Friday night Through Sunday night/...A flat upper
level ridge is progged to be positioned from the southwest
Atlantic westward into the Gulf into the weekend. North of the
ridge, mid-level impulses with varying degrees of amplitude
amongst the guidance migrate eastward Saturday. Some indications
that the nose of the Gulf upper ridge will extend more northward
over the area into the day Sunday, bounded by a two upper level
trofs. One over the Mid-Atlantic to its east and the other over
the Plains to its west. No appreciable change to environmental
moisture depth is noted through the weekend with PWATs ranging
from 1.8-2.0 inches. Considering this along with daytime
instability and the passage of mid-level impulses looks to aid in
the initiation of mainly daytime scattered showers and storms
Saturday. Even though more ridging aloft would suggest a lower
chance of storms Sunday, will maintain a modest chance of storms
out of respect for impulses riding down the southwest side of Mid-
Atlantic trof.
As for temperatures, latest guidance shows warm, muggy nights with
night-time lows ranging in the lower/mid 70s interior. Mid to
upper 70s likely to the south and closer to the coast. Highs
Saturday are anticipated to be in the mid to upper 80s northwest
of I-65 and along the coast. Upper 80s to lower 90s along and
southeast of I-65 to I-10. Highs Sunday 87 to 92 range area-wide.
/10
EXTENDED TERM /Monday Through Thursday/...Gulf upper ridge looks
to continue nosing northward into the Lower MS River Valley to
start the new work week. An upper low over the northeast US Monday
eases southwest over the New England states by the middle of next
week. A potentially active high level northwest flow pattern looks
to setup between this northeast US upper trof/low and the southern
US ridge. These types of flow patterns support southeastward
propagating convective complexes which can produce strong winds.
Considering this potential, little change in deep moisture as
mentioned in the short term discussion, daytime heating and
instability, showers and storms look to become likely each day.
Before storms bring a cool off, heat indices of 98 to 103
possible in some locations through the middle of next week.
Low level/surface pressure ridge remains anchored over the FL
Peninsula with little change in highs and lows. /10
MARINE...No significant impacts expected over the marine area
through the period. Seas generally 2 feet or less, enhanced
slightly near shore by afternoon sea breeze and also around
isolated to scattered showers and thunderstorms. /12
&&
.MOB WATCHES/WARNINGS/ADVISORIES...
AL...None.
FL...None.
MS...None.
GM...None.
&&
$$
This product is also available on the web at:
http://weather.gov/mob
Area Forecast Discussion
National Weather Service Tucson AZ
340 PM MST Thu Jun 25 2020
.SYNOPSIS...The heat will slowly subside over the next few days as
high pressure weakens over the area. A moisture increase from the
south will bring a chance of afternoon and evening thunderstorms
to the area Saturday afternoon into early next week before another
drying trend by mid week.
&&
.DISCUSSION...High pressure overhead with temperatures running
7 to 8 degrees above climatology today. First 109 of the season so
far at Tucson International with 110 not out of the question this
afternoon.
With a weak trough digging into the region over the next 36 hours,
we`ll see some moderation in the temperature as heights and
thicknesses fall back toward climo by Saturday. In the mean time,
pressure differentials are enhancing a southerly flow up the Gulf
with a moisture surge just beginning. HRRR trends are grabbing
onto this nicely with elevated surface and near surface moisture
beginning to spread into the lower deserts tonight and Friday
morning. HREF ensemble moisture probabilities suggest surface dew
points in excess of 50 degrees pushing in from the south late
Friday into Saturday morning, 1 inch precipitable water values
pushing from central to northern Sonora as early as Friday
evening. While initial surge depth will be on the shallow side,
NAEFS mean integrated water vapor transport percentiles suggest
some depth by Saturday afternoon and evening. In addition, we are
looking at the proximity of a significant remnant weakness in the
flow providing some potential shear and organization to any
storms that might develop Saturday afternoon. Main concerns will
be strong, gusty and erratic outflow winds and potential dry
lighting. Storm cores should be tight with relatively narrow (but
not inconsiderable) rain shafts and prime microburst conditions.
We`ll keep a chance of thunderstorms into Monday or Tuesday, but
ultimately a very late season trough should push a dry westerly
flow back over the area by Wednesday.
Some early signs of what might end up being even stronger and
hotter high pressure around the July 4th weekend. Stay tuned.
&&
.AVIATION...Valid through 27/00Z.
FEW-SCT clouds AOA 15K ft MSL thru the forecast period, with
occasional periods of BKN clouds possible mainly north of KTUS.
Surface wind WLY/NWLY at 11-16 kts with gusts near 26 kts through
26/03Z, then becoming 12 kts and variable in direction at other
times through about 26/17Z. SWLY/WLY winds resume thereafter at 10-
18 kts with gusts up to around 27 kts. Aviation discussion not
updated for TAF amendments.
&&
.FIRE WEATHER...Dry conditions will continue across much of the area
through Friday. An increase in lower to mid level moisture will
result in isolated to scattered mainly afternoon and evening showers
and thunderstorms Saturday through Tuesday mainly for areas from
Tucson south and eastward. These thunderstorms will be capable of
producing gusty and erratic outflow winds. Brief downpours are
possible with the stronger storms but widespread wetting rain is not
expected.
Otherwise, expect elevated southwest to west winds 20-
ft winds through Tuesday, with the strongest winds expected Sunday
and Monday. Wind speeds may briefly approach critical fire weather
thresholds Sunday and Monday. Minimum humidity levels will remain
low with poor overnight recoveries tonight. Some improvement with
overnight recoveries is expected this weekend and early next week.
Haines 5 & 6 conditions mainly from Tucson eastward through
Friday.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Public...Meyer
Aviation...Lader
Fire Weather....Lader
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