Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/21/18
Area Forecast Discussion
National Weather Service Bismarck ND
948 PM CDT Fri Jul 20 2018
.UPDATE...
Issued at 941 PM CDT Fri Jul 20 2018
Made some minor adjustments to sky cover. Lowered temperatures a
bit central and added a mention of patchy fog over portions of
the central, mainly between Bismarck and Jamestown, and from
Harvey down to the SD border. Overnight shift can modify as
needed. Lots of rain here recently and appears to be a good
radiational cooling setup with the position of the surface high
early Saturday morning. HRRR, RAP and GFSLAMP are all hinting at
possible fog in this area tomorrow morning.
UPDATE Issued at 551 PM CDT Fri Jul 20 2018
For the early evening update only a few minor changes. We bumped
up sky cover a bit Saturday afternoon in the James River Valley
per forecast soundings. Did not increase sky cover enough to
produce a ceiling but this may be possible. We also bumped up
winds in the west Saturday afternoon into the 15 to 25 mph range.
Could be some patchy fog over central ND per the latest iterations
of some of the mesoscale models but confidence not high enough at
this time to add to the forecast. Will see how models trend
through the evening.
&&
.SHORT TERM...(This evening through Saturday Night)
Issued at 212 PM CDT Fri Jul 20 2018
Possible smoke impacts this evening into Saturday, and severe
thunderstorm potential west Saturday evening highlight the short
term forecast.
The main question for this evening through tomorrow is possible
smoke impacts from a fire approximately 115 miles northeast of
Winnipeg as smoke may be transported in the low levels around the
surface high. Visibility across the northern Red River Valley and
northwest Minnesota downstream of the fire is reduced as low as 4
to 7 miles. The experimental 12Z HRRR-Smoke forecast would
suggest an increasing potential for near-surface smoke across
western and central North Dakota this evening through tonight, and
possibly lingering into Saturday. Will continue to monitor
upstream satellite and surface observation trends.
For Saturday, did increase highs across the west into the upper
80s and lower 90s, closer to the warm edge of the 12-15 UTC
guidance envelope with the low level thermal ridge axis.
Regarding convective potential, SPC has placed a Slight Risk
across northeast Montana, into far northwest North Dakota, with a
Marginal Risk extending east to approximately Portal through
Dickinson and Hettinger. The 12 UTC CAM and global consensus is
for convection to initiate late Saturday afternoon or early
evening across eastern Montana along the cold front and inverted
trough. This convection may approach the North Dakota border
around 00-03 UTC. While deep layer shear is strong, around
40-50kts and oriented generally orthogonal to the surface
boundaries, the zone of 1500-2000 j/kg of MLCAPE is rather narrow,
and quickly drops off across western North Dakota. While
organized convection, including possibly a supercell or two, may
enter western North Dakota Saturday evening, the approach of
sunset and propagation too far east of the best instability should
limit the severe threat to the west and likely ending by 06 UTC.
Thunderstorms may be sustained into the night across central North
Dakota with the low level jet, however, their intensity should be
weaker and likely less organized.
.LONG TERM...(Sunday through Friday)
Issued at 212 PM CDT Fri Jul 20 2018
Severe thunderstorm potential central on Sunday highlights the
extended forecast.
A cold front with a mid level jet streak/shortwave will be the
focus for thunderstorm development across central North Dakota
Sunday afternoon and into the early evening. Cloud cover impacts
from likely ongoing morning convection adds uncertainty to
afternoon heating and destabilization. Deep layer shear around
40kts, and generally orthogonal to the cold front, would support
the potential for discrete organized convection. Precipitable
water climbing to around 1.75 inches supports the potential for
locally heavy rainfall, including across portions of the James
River Valley that saw very heavy rainfall earlier this week.
For much of next week, rather fast west-northwest mid level flow
south of the Canadian upper level low supports sporadic chances
for thunderstorms associated with low predictability impulses.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 941 PM CDT Fri Jul 20 2018
VFR conditions expected this evening with Northeast winds
diminishing and shifting southeast. Patchy fog possible mainly
between KJMS and KBIS but not confident enough to add to either
TAF at this time. Could be a couple hours of MVFR ceilings late
morning or early afternoon at KJMS as Cu field flattens and begins
to lift.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...TWH
SHORT TERM...PA
LONG TERM...PA
AVIATION...TWH
Area Forecast Discussion
National Weather Service Caribou ME
944 PM EDT Fri Jul 20 2018
.SYNOPSIS...
High pressure will exit to the east Saturday. Low pressure will
lift north across the region Sunday.
&&
.NEAR TERM /THROUGH SATURDAY/...
9:44pm update...Biggest change to near term is bumping up cloud
cover along the Downeast coast. Light winds and high humidity
has harbored growth of a fog shelf just offshore and in some
coastal communities. Webcams in Winter Harbor and Bass Harbor
confirm the sea level fog working its way towards the coast.
Like the HRRR depiction of this bank staying just along coastal
Hancock and Washington counties through early morning.
Previous discussion:
High pressure will cross the region tonight then exit to the
east Saturday. Skies will remain mostly clear across northern
and central portions of the forecast area tonight through
Saturday. Across Downeast areas, expect mostly clear skies much
of tonight. However, cloud cover could increase later tonight
with low clouds and fog moving inland from the Gulf of Maine
which could persist early Saturday. The low clouds will retreat
offshore later Saturday morning, leaving mostly sunny skies
from late morning through the afternoon. Low temperatures
tonight will range from the mid to upper 50s across
northern/central areas, to the mid 50s Downeast. High
temperatures Saturday will range from the mid to upper 80s
north. Temperatures will be cooler across Downeast areas with
onshore winds from the Gulf of Maine. High temperatures across
interior Downeast areas will range from around 80 to the lower
80s, with temperatures generally ranging through the 70s along
the Downeast coast.
&&
.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
Subtropical low pressure moving north across eastern or central
NY Sat night will drive clouds north across the state. Precip
will push northeast into the CWA by mid-morning Sun, with high-
end chance to likely POPs across much of the central and
southern CWA during the afternoon. Precip may die off a bit Sun
night, but kept chance POPs across most of the CWA as there will
be ample moisture coming onshore. The upper ridge may build back
west a bit during the day Mon, leading to reducing POPs over
Downeast. However, the axis of action appears likely to shift
inland, especially over the northwestern higher terrain, during
the afternoon Mon. Expect highs in the low to mid 70s Sun, and
in the mid 70s to around 80 Mon.
&&
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
Pattern remains active for much of the long term as the upper
trough remains off to the west through at least Thurs. POPs Tue
and Wed highest for central and NWern areas. A wave moving
across the area Thurs could spread a better chance of precip
back toward the coast. Models seem to be keying in on the upper
trough finally starting to shift east on Fri, pushing through a
front, with some drier air and likely lowering POPs for later
Fri into Fri night.
&&
.AVIATION /01Z SATURDAY THROUGH WEDNESDAY/...
NEAR TERM: Low clouds and fog will likely reach Downeast areas
late tonight with MVFR to LIFR conditions persisting through
early Saturday. Conditions will then improve to VFR levels
Downeast through the morning, with VFR conditions persisting
through the afternoon. VFR conditions are expected across
northern and central areas Saturday.
SHORT TERM: IFR to LIFR CIGs and perhaps IFR or lower vsby for
KBHB and KBGR developing Sat night. Widespread IFR CIGs will
spread northward through the day Sun and persist through much of
Monday. Fairly widespread MVFR to IFR CIGs expected through
mid-week as the weather pattern changes little.
&&
.MARINE...
NEAR TERM: Winds/seas are expected to remain below small craft
advisory levels tonight through Saturday. Visibilities will be
reduced in areas of fog later tonight with patchy fog through
Saturday.
SHORT TERM: Light wind and seas under 4 feet will continue
through Sat night. Winds will increase during the day Sun and
remain moderate breezes with gusts up toward 20kts through Mon.
Seas will build Sun, and may exceed SCA criteria Sun night into
Mon.
&&
.CAR WATCHES/WARNINGS/ADVISORIES...
ME...None.
MARINE...None.
&&
$$
Near Term...CB/Cornwell/Norcross
Short Term...Kredensor
Long Term...Kredensor
Aviation...CB/Cornwell/Norcross/Kredensor
Marine...CB/Cornwell/Norcross/Kredensor
Area Forecast Discussion
National Weather Service Cleveland OH
900 PM EDT Fri Jul 20 2018
.SYNOPSIS...
Slow moving low pressure will track from southern Lake Michigan
tonight into the Ohio valley by Sunday. The low will weaken and
dissipate as it drifts into the Tennessee valley Monday. A cold
front will slowly move across the area during the middle of the
week.
&&
.NEAR TERM /THROUGH SATURDAY NIGHT/...
Convection has pretty much died down so went with scattered
showers and isolated tsra for the overnight period. Also removed
mention of potential for severe tsra from HWO. Rest of forecast
looks reasaonable for the 930 update.
Original discussion...
Not many changes to the forecast tonight through Saturday
night, with the focus of the forecast on convection/severe
potential this evening and precip chances Saturday. A slow
moving, vertically stacked low will track from near Lake
Michigan this evening southward into the Ohio valley late
Saturday night into Sunday morning. Several waves of
precipitation will rotate east-northeast across the region, with
a focus on diurnal development during the afternoon on
Saturday. In the immediate, ongoing showers/storms across far
northeast Ohio and northwest PA will continue to work northward
late this afternoon, while and area of rain with embedded
thunderstorms pushes east across the southern part of the area,
south of US-30, over the next couple of hours, generally in a
weakening trend.
Focus turns to line of convection currently across northern Indiana.
Modest/narrow corridor of 1000-1500 j/kg SBCAPE exists ahead of this
line, with fairly weak/marginal effective bulk shear values of 30
kts or so. Biggest challenge is the intensity trend of this line,
and whether or not it will remain organized and severe into the I-75
corridor a couple hours from now. Hi-res guidance has been
consistent in weakening any convection as it tracks into the local
area around/after 00Z, however the latest runs of the HRRR are not
handling the speed/intensity of the current line. The line may
weaken if the instability corridor gets pinched off between the
advancing severe line and the more stable boundary layer near the I-
75 corridor from ongoing or recently ended rainfall. Still have high
likely pops working into the I-75 corridor from 22Z to 00Z, and
think there is some potential for a few organized/strong storms to
sustain into the area. Convection should diminish from 03Z onward
through the night.
Kept pops generally in the chance range overnight with a brief
period of likely pops across the southern part of the area towards
morning, as an area of lift associated with the low level jet moves
into the southeast part of the forecast area, with a consistent
signal of precip development in recent model runs. A lull in
convection is possible through the morning hours tomorrow, however
have ramped pops up to likely across the area in the afternoon as
modest destabilization of 500-1500 j/kg occurs across the area. Have
again trended pops downward through the evening/overnight with a
loss of instability. Kept temps near previous forecast tonight and
Saturday night, and maybe a degree or two lower for highs on
Saturday given expected cloud cover and scattered precip.
&&
.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
The upper level low will weaken on Sunday as it drifts southward.
However with the cooler air aloft within the upper level trough we
will have to maintain chances of showers and thunderstorms. Another
piece of energy will approach Monday night into Tuesday with chances
of thunderstorms increasing by Tuesday afternoon.
Sunday looks to be the cool day of the short term with highs in the
middle 70s. Seasonal temperatures Monday into Tuesday with highs in
the lower to mid 80s.
&&
.LONG TERM /TUESDAY THROUGH FRIDAY/...
The long term begins Tuesday night with models showing weak forcing
across the area however at the surface there should be a cold
front/trough bisecting the area. Best chance of precip should be
east with lower level flow bringing atlantic moisture into the area
from the southeast. Will have chance pops east to start the night
and go up to likely pops after midnight as moisture increases. For
Wednesday will continue with the likely pops far east, chance
through the central lakeshore and highlands to nothing northwest.
Wednesday night and Thursday models try to bring drier air in slowly
from the northwest, shifting the best moisture east. The cold front
will also shift east and dissipate as another cold front moves into
the region from the northwest. With the drier air in place however
believe rain chances still drop through the 24 hour period. For
Thursday night and Friday high pressure begins building in from the
northwest so will go with a dry forecast. Highs Wednesday should get
into the low and mid 80s with a few upper 80s west. Thursday and
friday look for highs 80 to 83.
&&
.AVIATION /00Z Saturday THROUGH Wednesday/...
Thunderstorms moving into TOL area have diminished significantly
last 2 hours. Expect showers and tsra to become more scattered
after sunset. Expect widespread MVFR to develop overnight with
areas of IFR in the West, as the low over Lake Michigan drifts
east.
OUTLOOK...Non-VFR possible Saturday and Sunday with showers and
thunderstorms.
&&
.MARINE...
Stacked low pressure will drift from Lake Michigan to southwest Ohio
by Sunday morning. This will keep south to southeast wind going on
the lake through Saturday afternoon. Winds will then shift a bit
more to the east as the low weakens as it drifts further south.
Current thinking is that he southeast to south winds will be low
enough to avoid the issuance of a small craft advisory. However
stronger gusts may occur with any thunderstorms. Low level lapse
rates steepen enough on Saturday to be concerned about waterspouts.
While it does look marginal the proximity of the upper level low
makes us think that the spouts could occur across the western half
of the lake from Toledo to Avon.
By Sunday easterly winds will increase with a good chance that we
will need a small craft advisory. We will take a closer look at this
tomorrow. The winds will only slowly decrease Sunday night into
Monday becoming light Monday night and remaining that way into
Tuesday.
&&
.CLE WATCHES/WARNINGS/ADVISORIES...
OH...None.
PA...None.
MARINE...None.
&&
$$
SYNOPSIS...Greenawalt
NEAR TERM...DJB/Greenawalt
SHORT TERM...Mullen
LONG TERM...TK
AVIATION...DJB
MARINE...Mullen
Area Forecast Discussion
National Weather Service State College PA
941 PM EDT Fri Jul 20 2018
.SYNOPSIS...
The recent stretch of pleasant and conformable weather across
central PA will come to an end this weekend, as the pattern
turns decidedly unsettled, muggy and rather wet through next
week.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Convection west of CWA has dissipated leaving the area with a
quiet night tonight. Latest HRRR runs show large area of rain
approaching SE zones after sunrise, which is covered well in
forecast.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
Hybrid coastal low will track north along the mid Atlantic
coast from eastern NC across the Delmarva on Saturday and
approach southern New England by Sunday morning. This low will
eventually be absorbed by the anomalous deep-layer cyclone that
is expected to move slowly southeastward into the Ohio Valley.
Confidence has increased significantly in a period of heavy rain
spreading northward across the eastern 1/3 of the CWA later
Saturday afternoon into Saturday night. The 12Z HREF mean shows
a cyclonically curved, 50+kt LLJ drawing deep moisture inland
ahead of the hybrid low, with PWs reaching 1.5 to 2.5 inches
over southeast PA. There is definitely a short-duration flash
flood risk given the impressive PWs, strong lift and low level
moisture transport, but limiting factors include dry antecedent
conditions, high FFG and low CAPE. 1-2 inch amounts are likely
with localized higher amounts possible. Despite high confidence
in a period of heavy rain, decided to hold off on FF watch given
aforementioned factors and preference toward a more short-fused
issuance. Added heavy rain/ff threat in the HWO.
Clouds will hold daytime temps in the low to mid 70s, and it
will feel more humid and muggy.
&&
.LONG TERM /SUNDAY THROUGH FRIDAY/...
By 12z Sunday, compact coastal low will be sliding north of the
area. But very gradually filling inverted low will edge toward
western PA while continuing to channeling tropical-like
moisture into the region - keeping unsettled weather ongoing
through much of next week - peaking in the afternoons. Best
daily chances for tstorms shifts to western/central sections
Tue/Wed before returning eastward Thu as a cold frontal boundary
finally pushes across the state.
Temperatures will be below normal Sun with thicker cloud cover
and moist SE/E flow, then highs return closer to normal for
next week while lows look to remain on the muggy side.
&&
.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
VFR conditions across the region this evening. Banded showers
moving south to north over western Pennsylvania. Expect VFR
conditions to continue into Saturday morning, followed by
lowering conditions during Saturday as low clouds and showers
develop across the airspace.
Low VFR to MVFR ceilings are probable Saturday into Saturday
night, with some pockets of IFR Saturday night into early
Sunday.
Showers are expected to spread northward from the Delmarva/Chesapeake
Bay region into the south central/southeast airspace early Saturday
morning. Expect a period of moderate to heavy rain later Saturday
afternoon into Saturday night across the eastern airspace.
Unsettled weather with showers and isolated thunderstorms to
continue into mid week.
.Outlook...
Sat...VFR start early, then conditions lowering to MVFR in all
areas except VCTY KBFD.
Sun-Wed...Frequent showers/isolated T`storms with associated
MVFR/IFR restrictions.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Steinbugl
NEAR TERM...Ross/Steinbugl
SHORT TERM...Steinbugl
LONG TERM...RXR
AVIATION...Jung/Steinbugl
Area Forecast Discussion
National Weather Service Grand Forks ND
950 PM CDT Fri Jul 20 2018
.UPDATE...
Issued at 950 PM CDT Fri Jul 20 2018
Adjusted POPs a bit for current radar trends as showers over our
far eastern tier have pretty much dissipated. Only a few
sprinkles remain and will be completely gone in an hour. Smoke
will continue to be in issue in some areas but will eventually
shift further west as winds begin to turn.
&&
.SHORT TERM...(This evening through Saturday)
Issued at 237 PM CDT Fri Jul 20 2018
Air quality alert from the Minnesota Pollution Control Agency in
effect until 9am Saturday morning. Smoke from Canadian wild fires
leading to reduced visibility and air quality concerns. These
conditions will improve by later tonight as the low level flow
becomes more easterly and keep the smoke plume north of the
region.
Upper low will continue to propagate off to the east, with
scattered showers (isolated thunder) east of the valley into the
evening. Timing the clearing clouds will be the main challenge,
which should gradually clear from west to east, but will likely
remain across the far eastern FA into Saturday morning.
Ridging will build into the region on Saturday, leading to
relatively quiet weather with temperatures near normal values.
.LONG TERM...(Saturday night through Friday)
Issued at 237 PM CDT Fri Jul 20 2018
A shortwave H5 ridge will influence the weather pattern going into
Sunday. This will be enhanced by an upper low moving eastward out of
Alberta. Winds aloft shift from northwesterly to southwesterly
through the day as this low moves into Saskatchewan. Surface winds
become southeasterly, allowing moisture levels to increase; however,
the relative strength of the low level flow will be weak. Although
we expect mostly sunny skies during the early part of the day,
increasing cloudiness and precipitation chances become the story
during the afternoon hours. Increasing CAPE and generally favorable
shear patterns will allow potentially severe thunderstorms to
develop along and ahead of a cold front. The highest instability
looks to remain west of the Red River with CAPE values approaching
the 1500 to 3000 J/Kg range briefly during the late afternoon/early
evening. The setup will be favorable for a multi-cell or weak
supercell mode with hail, damaging wind gusts, and tornadoes all
being possible.
The H5 upper low moves slowly through Saskatchewan on Monday before
moving into Manitoba on Tuesday. Shortwave troughs of varying
strength will pivot around the low, bringing unsettled weather into
the region during the Monday through Wednesday period. Another
chance of storms is in the forecast for Tuesday evening. Strong to
severe storms are possible, however, confidence is low regarding the
exact details at this time.
Slight rain and thunderstorm chances remain in the forecast on both
Wednesday and Thursday with isolated to scattered coverage expected.
Much cooler high temperatures in the lower to middle 70s prevail
both days.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 700 PM CDT Fri Jul 20 2018
Some MVFR ceilings at KBJI and KTVF moving in and out as some
cumulus and showers on the backside of a low pressure system
rotate through. All TAF sites should be VFR by later this evening.
Still some smoke in the area, although it is not currently
affecting visibility. HRRR has the smoke plume shifting
southwestward and becoming less dense. Thus, will keep out of the
TAFs for now and just amend as needed. North winds around 12 kts
will become more northeasterly and decrease towards the end of the
period.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
&&
$$
UPDATE...JR
SHORT TERM...TG
LONG TERM...Lynch
AVIATION...JR
Area Forecast Discussion
National Weather Service Goodland KS
922 PM MDT Fri Jul 20 2018
.UPDATE...
Issued at 922 PM MDT Fri Jul 20 2018
Main severe threat appears to have shifted east of southern
portions of the CWA for this evening. Have left in a slight
chance for a shower(rw)/thunderstorm(trw) for the next few hours
for mainly locales along and south of Hwy 40. No other changes at
this time.
&&
.SHORT TERM...(This evening through Saturday)
Issued at 255 PM MDT Fri Jul 20 2018
The Tri-State area is situated on the northeast periphery of an
upper level ridge, at the southern fringe of speedy NW flow
aloft. Light easterly flow will prevail in the low- levels this
afternoon into tonight, on the northern periphery of a weak
surface low situated over southeast CO/southwest KS.
Through Tonight: Challenging convective forecast. The HRRR and
NAM NEST continue to suggest that scattered convection will
develop invof the aforementioned sfc low along/south of
Cheyenne/Greeley/Wichita counties in southeast CO and southwest KS
late this afternoon and evening -- where weak low-level
convergence is present amidst little/no CIN -- with virtually no
development in northwest KS and northeast CO where low-level
forcing is weaker and 50-150 J/kg of CIN persists (as of 20Z).
Unless forcing is augmented by DPVA attendant a small amplitude
wave at the southern fringe of NW flow aloft, the atmosphere is
likely to remain capped in northwest KS and northeast CO -- which
is fortunate -- because the thermodynamic/kinematic environment in
northwest KS is otherwise quite supportive of supercells capable
of producing very large hail and damaging winds. At this time,
expect convection to be confined well south of US 40, where the
thermodynamics/kinematics favor multicellular organization and a
brief/intermittent potential for severe downbursts. Convection
will wane by 03-06Z in assoc/w loss of heating /increasing CIN/.
Saturday: The upper level ridge building eastward over the High
Plains is expected to result in pronounced capping /dry
conditions/. Expect highs in the lower to mid 90s.
.LONG TERM...(Saturday night through Friday)
Issued at 127 PM MDT Fri Jul 20 2018
The long term period starts with the region under northwest flow
aloft between a ridge across the southwestern CONUS and an upper
trough over the eastern half of the country. The pattern remains in
place through the weekend as a second upper trough cuts across the
Canadian border.
A disturbance is anticipated to work its way around the northern
edge of the ridge on Saturday which may result in a few storms
developing in central Colorado and progressing into our western CWA
during the evening hours. However, capping may limit convection.
After dry conditions during the day Sunday, better precipitation
chances return to the forecast Sunday night. The second trough
continues towards the Great Lakes, shifting the ridge westward.
Meanwhile, a cold front approaches the area, generating chances for
showers and thunderstorms across the forecast area. With PWATs at
1.5 inches, locally heavy rainfall still looks to be a threat.
The front continues to pass through the rest of the region early
Monday, dropping temperatures for the start of the work week.
Throughout the remainder of the long term, a series of shortwaves
pass through the northwest flow aloft as the upper trough digs into
the Upper Midwest, pushing ridging towards the west coast. This
results in better moisture filtering into the area and persistent
thunderstorm chances through Friday. Will continue to monitor the
potential for severe weather as this timeframe approaches.
High temperatures peak in the 90s on Sunday before decreasing mainly
into the 80s for the rest of the week. A few locations could see
some readings in the low 90s Wednesday and beyond. Low temperatures
will stay in the 60s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 529 PM MDT Fri Jul 20 2018
With high pressure over the terminal region for during the
forecast period...both sites will have VFR conditions w/ mainly
scattered high clouds.
Winds for KGLD...E 10-20kts thru 02z Saturday then SSE 10-20kts.
Winds for KMCK...E around 10kts thru 08z Saturday then light/
variable. By 14z...ESE around 10kts...w/ gusts to 20kts after
19z.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
UPDATE...JN
SHORT TERM...VINCENT
LONG TERM...JBH
AVIATION...JN
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1032 PM EDT Fri Jul 20 2018
.SYNOPSIS...
High pressure will weaken over the forecast area before a large
upper low drops south from the Great Lakes to the Southern
Appalachians tonight. This low will remain nearly stationary for
several days and support unsettled weather through the middle of
next week.
&&
.NEAR TERM /THROUGH SATURDAY/...
As of 1015 PM EDT Friday: Still seeing MCS convection march across E
TN, and as of this update MRX has issued SVRs right up to the state
line. Have increased pops just along the spine of the Appalachians a
little over the next couple of hours, but based on CSTAR research on
MCSs crossing the southern Appalachians, the thermodynamic
environment across the lee of the mountains really does not support
the MCS sustaining itself much farther east. Would expect that we
might have to issue a few SPSs and not totally out of the question
to see a SVR or two, but should not spread too far east. This is
shown pretty well in CAM reflectivity guidance. Of increasing
concern, however, is a secondary wave of convection just starting to
get going across Middle TN, and the HRRR and other CAMs DO have this
round of convection pushing east overnight and into the southern
mountains and north GA, upper Savannah Valley, around sunrise. We`ve
been watching these CAM trends for a few hours now and have seen a
consistent uptick in this, especially with some of the 00z HiRes
windows in now. Have increased pops accordingly. Other grids look to
be on track for now.
Otherwise, the potential for severe thunderstorms will dominate the
latter part of the near-term period Saturday. For the setup, a 500
mb low center over Lake Michigan this evening will continue to carve
out height falls across the Tennessee Valley and into the southern
Appalachians through the nighttime hours. Meanwhile, a low pressure
system along the coastal plain will move from SC to NC tonight with
just a continued low end threat of isolated showers along our
eastern piedmont fringe in weak deformation. A series of developing
MCSs will make a run south and east of the OH Valley and central TN,
but with most of the high resolution, convection allowing models
showing little impact across our forecast area overnight into
Saturday morning. The most recent runs of the HRRR are the most
aggressive, showing upstream convection filling in across central
Tennessee and eastern Kentucky by early evening and then brushing
the northern mountains and the Smokies vicinity before dissipating
in the weaker instability across the high terrain late evening/early
overnight. Additional activity may develop and make a run overnight,
but with little more than scattered showers and thunderstorm to
advertise along the TN/NC border through daybreak.
Forcing, instability, and shear should then come together for
Saturday. Although profiles look rather capped early in the day
tomorrow, the cap should be explosively overcome during the
afternoon hours, with 2000 to 3000 J/kg of sbCAPE likely realized
east of the Blue Ridge. The best pocket of 7+ deg C/km mid-level
lapse rates will then cross the region from mid-afternoon to early
evening. The mid-level speed maximum rounding the upper trough will
likely yield surface to 6 km bulk shear values of 30 to 35 kt by 21Z
Saturday. However, shear will be quite a bit weaker in the lowest 1
to 2 km of the atmosphere and this may toggle the severe potential
away from tornadoes to more of a damaging wind/hail threat.
Anticipate the better spokes of upper level vorticity under the
dominant trough to cross the region mainly from mid afternoon to
mid evening and this better forcing should promote the greatest
coverage and highest severe thunderstorm chances. Most of our area
remains in a well-placed Slight Risk of severe thunderstorms for
Saturday.
&&
.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
As of 215 PM EDT Friday: Robust,if not severe, deep convection
should be ongoing and numerous at the start of the period, all
within the unseasonable moderate deep cyclonic flow around Ohio
Valley closed low. Overall coverage will in no doubt wane overnight,
but the pattern will remain favorable for some degree of
regeneration at any point overnight, so at least low chance pop will
remain into early Sunday morning. Through Sunday, upper low will
continue it`s southward drift and slowly fill, which will actually
result in weaker shear and a little bit of drier air working in from
the west. But, at this point, it is hard to believe that diurnally
enhanced deep convective coverage won`t become numerous again,
especially across western NC. Sunday maxes still should about a
category below climo under the influence of the upper low. With the
axis of the filling upper low lingering atop the region through
Monday, the potential for a deeper southerly flow and influx of rich
Atlantic moisture increases. This setup may result in excessive
rainfall chances increasing. With Lots of clouds and rainfall
progged, max temps may wind up being at least 5 deg f below normal.
&&
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
As of 1230 PM EDT Friday: Not a lot of changes made to the ext fcst
from the previous package. The op models and ens means agree well
with a broad yet weak stacked low sw of the FA to begin the period.
This low will likely become more disorganized beginning Wed as an
ulvl trof picks it up and shears it out. The mean flow within the
sfc-h85 layer will begin e/ly which will provide very good Atl moist
flux. Soundings show pwats on the order of 2.00 inches Tue and the
potential of some hydro concerns...esp across the eastern facing
upslope zones. As the stacked low dissipates the flow becomes less
defined and rather weak thru the column...so the potential for
upslope heavy precip will lessen. There will be some instability and
tstms during this time...but it will remain conditional with llvl
sbCIN persisting each afternoon. Will keep the higher mention PoPs
each day with some reduction on Fri as a weak cold front shud cross
the region during the day limiting convec moreso across the mtns.
However...there is much uncertainty with the timing of this front
attm. With high cloud cover each day...max temps will be held a cat
or so below normal...while mins persist abv normal within weak rad
cooling.
&&
.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
At KCLT and Elsewhere: VFR this evening and into the early overnight
period, but this will be short-lived as a round of MVFR to possibly
IFR cigs develops especially across NC TAF sites during the pre-dawn
hours as moisture increases. Convection to our west is progged to
fall apart before it crosses the mountains, with another round of
convective potential around daybreak, but confidence still to low to
mention more than VCSH at KAVL. Of greater concern is convective
potential for Saturday afternoon and have mixed a combination of
VCSH/PROB30 TSRA around midday, transitioning to prevailing TSRA at
all sites by 18-20z. With SPC slight risk in place, some of these
thunderstorms could become severe with damaging winds, but will hold
off on including enhanced wind wording until we are in a TEMPO time
frame and can narrow down timing with greater confidence. NNE winds
this evening will continue to back around the compass NW tonight and
toggle WSW to SW just ahead of the approaching trough on Saturday.
Outlook: An active/wet period is expected to continue from Sunday
through the middle part of next week as a slow-moving storm system
begins impacting much of the East. Numerous showers and
thunderstorms are expected during this period. While there will
likely be an afternoon/evening peak in coverage on most days, higher-
than-normal chances will also exist during the overnight and morning
hours.
Confidence Table...
02-08Z 08-14Z 14-20Z 20-00Z
KCLT High 100% High 92% High 90% High 100%
KGSP High 100% High 100% High 100% High 100%
KAVL High 100% Med 75% High 100% High 100%
KHKY High 100% Med 77% High 86% High 100%
KGMU High 100% High 100% High 100% High 100%
KAND High 100% High 100% High 100% High 100%
The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables and ensemble forecasts
are available at the following link:
www.weather.gov/gsp/aviation
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.
&&
$$
SYNOPSIS...SBK
NEAR TERM...HG/TDP
SHORT TERM...CSH
LONG TERM...SBK
AVIATION...TDP
Area Forecast Discussion
National Weather Service Huntsville AL
909 PM CDT Fri Jul 20 2018
.NEAR TERM...(Tonight)
Issued at 909 PM CDT Fri Jul 20 2018
The TN Valley is still playing the waiting game this evening.
Regional 00Z soundings and Univ. of Alabama-Huntsville soundings all
continue to indicate a highly unstable atmosphere. There is some
deep-layer shear in place but little low-level shear--at least for
now. Both UAH and BMX soundings show a very small cap around 800-825
mb, while the OHX sounding has it almost completely eroded. All that
is missing is some lift to erode this cap and realize the instability.
Severe convection so far has been limited to east Tennessee, but
convective initiation is occurring across Arkansas as of 02Z/9pm.
Convection-allowing models have been all over the place today. There
are signs that the 00Z CAM runs are beginning to get a better handle
on the situation but it is tough to put a lot of faith in them.
Several CAMs suggest explosive development over central/eastern
Arkansas, which then brushes NW Alabama in the 04-06Z timeframe. The
latest HRRR puts very little over the area for the entire overnight
period--but also is not resolving current upstream conditions very
well. So the 00Z CAM consensus is about the best available option
for right now. Instability is not a concern at this point, and deep-
layer shear should be fairly robust. Low-level shear will increase
over the next 2-4 hours as a low-level jet kicks into place around
the parent low, so the tornado watch seems reasonable for now.
As far as the forecast, precipitation has been delayed about 3-4
hours, with PoPs peaking from about 05-09Z. Otherwise, based on
current trends, both temperatures and dew points have been nudged
upward for the rest of the night.
.SHORT TERM...(Saturday)
Issued at 253 PM CDT Fri Jul 20 2018
The upper low will continue to move east into the Ohio valley on
Saturday with a cold front moving through the local area through the
day and probably out to the east by Sat night. Although guidance
isn`t too excited about spitting out some QPF for Saturday, the cold
front and upper wave will provide decent lift for storms. Instability
should still increase rapidly by the afternoon combined with high
bulk shear and even some low level shear given a llj increasing
through the afternoon. Would think we would see something strong
along the line but we could be too worked over from today. If we
ultimately don`t get much of anything on Friday (totally possible)
this would set the stage for stronger storms on Saturday. For now,
stay weather aware on Saturday with damaging winds being the highest
threat.
Temps will rise to the upper 80s to lower 90s with heat index values
remaining near 100.
.LONG TERM...(Saturday night through Friday)
Issued at 253 PM CDT Fri Jul 20 2018
Most models move the main front to our southeast by Saturday evening.
The exception to that is the GFS which is a bit slower with the
frontal progression and continues to show more widespread showers
and thunderstorms near/east of I-65 through midnight before
dissipating. This, as alluded to before, seems to be the outlier.
Therefore, keeping a token 20 to 30 percent chance of
showers/thunderstorms in the forecast east of I-65. Should be
slightly cooler with overnight lows dropping into the mid 60s to
around 70 degrees.
On Sunday, models are in fairly good agreement that the strong
surface low over the Ohio Valley moves far enough south to produce 20
to 50 percent shower and thunderstorm chances through much of the
day. Wouldn`t be surprised if more widespread showers and
thunderstorms developed in southern middle Tennessee (more
consistently impacted by the southern edge of the stronger surface
low). Decent instability with wet-bulb zero heights around 11,000
feet and some dry air aloft could still produce some scattered strong
to marginally severe storms producing up to quarter size hail and
wind gusts around 55 mph. However, with much weaker shear, do not
think this will be very widespread in nature. Expect with cloud cover
and more widespread precipitation than the previous day, that highs
will be a bit cooler, in the 83 to 88 degree range. Coolest afternoon
temperatures should be in northeastern Alabama and southern middle
Tennessee. As the surface low pulls further east in the evening,
precipitation chances should diminish and become isolated to
scattered.
The large surface low continues to meander between eastern Alabama
and Georgia through Monday, before being cut-off from the main jet
and sinking southwest into the northwestern Gulf of Mexico by
the end of the week. A weak longwave trough axis extends southwest
into central Tennessee and to the surface low over the northwestern
Gulf of Mexico much of this period in models. This will keep lift
over or near the area and abundant moisture/instability will be in place
over northern Alabama and southern middle Tennessee. Thus, at least
high chances of showers and thunderstorms are expected during the day
through the end of the week. Highs generally in the mid to upper 90s
are expected much of that period. PWATS remain high, so the
atmosphere becomes much saturated throughout the column Monday
through Friday. Thus heavy rainfall will continue at times, possibly
producing some isolated flooding concerns. Overall high temperatures
will be in the mid to upper 80s through much of this period, with
lows only dropping into the lower 70s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 701 PM CDT Fri Jul 20 2018
Quiet weather prevailed across the area for the start of the TAF.
This will change over the next few hours, as an upper disturbance
brings scattered to numerous showers/thunderstorms this evening and
in the overnight. The strongest convection will be moving in from
NW-SE during the mid/late evening (coinciding with the stronger shear
parameters). Have more confidence of higher winds at KMSL this
evening when that area moves across NW Alabama. Isolated to scattered
convection should continue in the overnight. The stronger storms
could produce gusty winds over 30kt and hail. A frontal boundary
moving in from the NW should cause winds to become W-NW during
Saturday afternoon.
&&
.HUN WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
TN...NONE.
&&
$$
NEAR TERM...BCC
SHORT TERM...LN
LONG TERM...KTW
AVIATION...RSB
For more information please visit our website
at weather.gov/huntsville.
Area Forecast Discussion
National Weather Service Wilmington NC
627 PM EDT Fri Jul 20 2018
.SYNOPSIS...
Low pressure will move up the coast tonight with widespread rainfall.
Saturday will be mostly dry with another system bringing showers and
thunderstorms early Sunday. Next week is shaping up to be very unsettled
as low pressure moves into the Southeast.
&&
.NEAR TERM /THROUGH SATURDAY/...
As of 330 PM Friday...on the synoptic scale, the global models are
similar on dropping the upper level low into the Ohio Valley on
Sunday. The deep moisture, 2.5" precipitable waters, will be shunted
off the coast for a short bit on Saturday during the day before it
return Saturday night.
At the surface this afternoon the surface low is still in coastal
Georgia. The 12 UTC runs of the NAM, GFS, and ECMWF show the low
pulling out with the NAM the fastest and GFS the slower. All have
the low closing in Hatteras by 12 UTC Saturday. The frontal boundary
appears to waffle offshore in the wake of the low.
For precipitation today we had a couple of spots to get 3 to 5 inches
of rain. Currently the band of overrunning precipitation is running
from western Horry county to off the coast of New Hanover county. As
mentioned by WPC earlier in the day there has been not lightning
with any of these showers, but the lift over the frontal boundary
and the abundant moisture are making up for the lack up deep
instability.
Will continue the Flood Watch to midnight for Horry, Georgetown and
Williamsburg counties. But with the GFS and ECMWF slower track of
the low have extend the time for the Watch for Brunswick, New
Hanover, and Pender counties until 2 AM.
&&
.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
As of 330 PM Friday...As the upper-level low methodically shifts
southeastward, another swath of high precipitable water values
moves back over the area. A frontal boundary from the west will be
approaching the Carolinas late. The chance of thunderstorms
increases overnight Saturday with the extreme western portion of the
forecast area. This front is expected to stall over early next week.
With the deep moisture feed and the upper-level low to the west
during this time there is a good chance of thunderstorms throughout
this period.
Lows will be in the lower to middle 70s and Highs upper 80s at the
beaches and the lower 90s well inland.
&&
.LONG TERM /MONDAY THROUGH FRIDAY/...
As of 330 PM Friday...A very unusual pattern shaping up for the extended
period and if it comes to fruition, it could be a very wet period as
well. Guidance has the closed low currently in the Upper Midwest,
dropping due south and lingering along the Gulf Coast before
basically dissipating and or drifting west by the end of next week.
This, combined with the Bermuda High to the east sets up a
persistent tropical plume which feeds directly into the area through
about Thursday. We are maintaining likely pops throughout most of
the period subsiding a little very late as the pattern finally
shifts to more of a drier westerly flow aloft. Several inches of
rain could fall across the area. Temperatures will be stable with
highs mostly in the middle to upper 80s and warm and muggy overnight
lows well into the 70s.
&&
.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
As of 00Z...Low pressure moving up the coast with onshore showers.
The coverage and intensity are much less than the models were
showing earlier, and the HRRR model has backed off considerably over
the last few hours. Nevertheless, look for IFR conditions to spread
over the CWA beginning around 05-06Z (based on the LAV). Most of the
deep moisture moves out of the region by 13Z, with Pender county the
last to see precip as the low exits the region. Conditions will
improve to VFR by early afternoon at the latest with west southwest
flow becoming southwest along the coast.
Extended Outlook...Occasional MVFR to IFR conditions due to
scattered SHRA and TSRA Saturday through Tuesday.
&&
.MARINE...
NEAR TERM /THROUGH SATURDAY/...
As of 330 PM Friday...low pressure is located southeast of Savannah
and this low is projected to slowly move northward along the stalled
cold front that is hanging just inland from the coast. The latest
models are showing at low to move off Hatteras late tonight. The
winds will increase to 15 to 20 nm and seas will increase to 3 to 5
feet overnight. As the low shift north the winds will shift offshore
and the seas will fall back to 2 to 4 feet.
SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
As of 330 PM Friday...A frontal boundary pull northward and winds will
shift to the southwest south of the front at 10 to 15 knots.
Seas will run 3 to 4 feet Saturday night and increase to 3 to 5
feet late Sunday into Sunday Night.
LONG TERM /MONDAY THROUGH WEDNESDAY/...
As of 330 PM Friday...Along with the public part of the forecast, the
Coastal Waters Forecast looks quite unsettled as well. With surface
and mid level low pressure to the west, and Bermuda High Pressure
to the east, winds and seas should stay elevated. Expect south to
slightly southeast winds of 15-20 knots Monday and most of Tuesday.
Speeds should drop back slightly on Wednesday in a 10-15 knot range.
These winds will keep significant seas elevated in a range of 3-6
feet.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...Flash Flood Watch until midnight EDT tonight for Scz053-
054>056-058-059.
NC...Flash Flood Watch until 2 AM EDT Saturday for NCZ105>110.
Coastal Flood Advisory until 7 PM EDT this evening for NCZ107.
MARINE...None.
&&
$$
SYNOPSIS...SHK
NEAR TERM...DRH
SHORT TERM...DRH
LONG TERM...SHK
AVIATION...43
Area Forecast Discussion
National Weather Service Memphis TN
858 PM CDT Fri Jul 20 2018
.UPDATE...
Thunderstorms are starting to develop over Central Arkansas at
this time. The NAM Nest showed this development on the 18Z run.
This could be the start of the expected severe weather. Right
now if these storms continue to evolve, best chances for severe
storms may be along and south of I-40. Will leave forecast as is
for now.
KRM
&&
.DISCUSSION... /issued 303 PM CDT Fri Jul 20 2018/
Skies are mostly sunny across much of the forecast area this
afternoon with temperatures in the low to mid 90s. Current heat
index values are close to 110 degrees in areas where the excessive
heat warning is in effect. Currently, a cold front extends from
northern Indiana into central Missouri.
This cold front will continue to drop south tonight and move into
the forecast area overnight. Additional thunderstorms are expected
to develop ahead of the front tonight and move into the forecast
area. Some of these thunderstorms could become severe with
damaging winds as the main threat but large hail and isolated
tornadoes can`t be ruled out especially over northwest Tennessee.
Temperatures will remain rather seasonable with lows Saturday
morning in the low to mid 70s.
The cold front will continue to move through the forecast area
Saturday with scattered thunderstorms expected ahead of the front
mainly over north Mississippi. Temperatures will be a little
cooler with highs in the lower 90s. Heat index values will be
lower on Saturday so no Heat Advisory should be needed. High
pressure will briefly build into the region for Saturday night
bringing dry weather and slightly cooler temperatures.
An upper level disturbance will drop south into Middle Tennessee
on Sunday with scattered thunderstorms possible over eastern
sections of the forecast area for Sunday and Sunday night. Monday
may see some scattered afternoon thunderstorms over eastern
sections of the forecast area.
Another cold front will approach the region on Tuesday and move
into the forecast area on Wednesday. This will mean more
thunderstorms both days. This front will die out across the
forecast area on Thursday but another front will start to approach
the region Thursday and next Friday so more thunderstorms are
expected to form.
ARS
&&
.AVIATION...
Expect SHRAs/TSRAs to develop in a very unstable atmosphere
across the Mid-South as an upper level disturbance moves through
in the strong NW flow aloft. Moved the timing for TSRAs up a
couple of hours given the ongoing trends and latest HRRR run.
Expect most of the activity to push south of the region by
sunrise. Saturday looks VFR with gusty NW winds.
SJM
&&
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...None.
MO...None.
MS...None.
TN...None.
&&
$$
Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
1008 PM CDT Fri Jul 20 2018
.DISCUSSION...See updated information for land areas below.
&&
.UPDATE...Relatively quiet evening across the central Gulf Coast
region as a subsident and somewhat drier deep layer airmass has
advected into our region in northwest flow aloft. There still
remains considerable forecast uncertainty regarding storm/severe
weather potential across our forecast area through the next 12-24
hours. Regional satellite/radar imagery shows the next complex of
severe convection developing across central/eastern portions of AR
along a frontal boundary and a shortwave trough pushing
southeastward within northwest flow aloft on the southwestern
periphery of a larger scale trough axis encompassing the OH/TN
Valley regions. The bulk of short range guidance quickly brings
this shortwave trough southeastward across the Lower MS River
Valley and toward AL through Saturday morning. There remains a lot
of spread in the short range and higher resolution convection-
allowing guidance on storm development/evolution overnight into
Saturday morning, with the past few runs of the HRRR tending to
weaken convection before it reaches our CWA early Saturday
morning. Nonetheless, ascent and increased deep layer moisture
associated with the approaching shortwave trough will support a
low potential for convective development into our northwest zones
through around 7-8 A.M. with additional development possible
through the morning/early afternoon across the rest of the
forecast area. Plentiful instability with CAPE values between
3000-4500 J/KG and increased 0-6 km shear on the order of 25-40
knots will certainly be supportive of severe storm development if
convection moves/develops over our region late tonight into
Saturday. Will opt to pull the Marginal Risk a little farther
south/east through Saturday morning in our local graphics given
short range guidance trends. Severe risk into Saturday afternoon
remains conditional on convective evolution through Saturday
morning, and will continue to assess this potential overnight after
looking at newer available guidance. /21
&&
.PREV DISCUSSION... /issued 803 PM CDT Fri Jul 20 2018/
DISCUSSION...See updated information for land areas below.
UPDATE...Have updated evening zone package to remove heat
advisory headlines that expired at 7 pm this evening. No other
updates at this time. /10
PREV DISCUSSION... /issued 635 PM CDT Fri Jul 20 2018/
DISCUSSION...Updated for latest aviation discussion below.
AVIATION...
00Z issuance...VFR conditions forecast tonight over the coastal
terminals. Light south to southwest winds this evening becoming
more west late. /10
PREV DISCUSSION... /issued 414 PM CDT Fri Jul 20 2018/
NEAR TERM /Now Through Saturday/...Main impacts to affect the
forecast area through Sat afternoon will be the chance for a few
strong to possible severe thunderstorms moving into northern
sections of the forecast area late tonight and early Sat,
generally along and north of highway 84, and persistent heat
index values ranging from 108 to 112 degrees. For tonight and
early tomorrow thunderstorms will be moving southward towards the
coast with the potential for strong gusty straightline
winds...frequent cloud to ground lightning and very heavy rain
beginning mostly after midnight tonight continuing into the mid
morning hours. Most of the model guidance depict a well defined
MCS forming over the TN River valley later this afternoon and into
this evening pushing southward over northern sections of AL and
MS late this evening, then further south through the mid morning
hours. Thunderstorms should be on a weakening trend as they move
southward overnight though with plenty of deep moisture and
instability in place overnight this trend will have to be closely
monitored. By Sat afternoon more showers and thunderstorms are
expected to develop as the boundary layer becomes recharged from
daytime heating. Gusty straightline winds...frequent cloud to
ground lightning and very heavy rain will be likely with the
stronger thunderstorms during the afternoon on Sat. The best
chance for thunderstorm development on Sat will be generally east
of the Mobile River including coastal areas and the near shore
waters of Al and NWFL. There is plenty uncertainty on the coverage
and timing with the development of thunderstorms tonight and on
Sat possibly leading to more updates this evening and overnight.
Day and nighttime temps will continue to be above seasonal norms
combined with dewpt temps ranging from the middle 70s to near 80
for most locations. Heat index values ranging from 108 to 112
degrees F have been recorded in many locations over southeast MS
and along the coast today and will likley continue in these
through the weekend. As a result a Heat Advisory will continue
over all areas of southeast MS and bordering counties in southwest
Al through 7 pm tonight followed by another Heat Advisory from 10
am until 6 pm Sat mainly for all coastal counties of AL and NWFL
along with Greene, Stone, George and Perry counties in southeast
MS. 32/ee
SHORT TERM /Saturday night Through Monday night/...The large
upper high pressure system over the southern Great Plains will
slowly retrograde westward over the Desert Southwest through the
short term. An upper level ridge extending southeast from the
center of the high over the northern Gulf of Mexico will shift
south- southwest over the western and southern portions of the
gulf by noon Monday while the center of a large upper low pressure
system over the Ohio River Valley region drops south over the
southeast states. The surface ridge across the Gulf of Mexico will
migrate slowly southward slightly through the period, while a
surface low reflected under the upper low across Ohio River Valley
region also drops south across the southeast states.
Isolated to low-end scattered showers and thunderstorms will
develop Sunday afternoon east of the Alabama River as the upper
low approaches, and likley remain dry to the west of the river.
These showers and thunderstorms will then dissipate through early
Sunday evening. Shower and thunderstorm coverage will increase on
Monday, with scattered showers and thunderstorms east of the
Alabama River, with isolated coverage to the west of the river.
High temperatures on Sunday will reach the mid 90s with the very
moist airmass still in place. As a result, heat indices on Sunday
will reach 107 to 112 degrees across the southern portions of the
forecast area, and 100 to 107 degrees across the north. Therefore,
the Heat Advisory in effect across the southern portions of the
forecast area on Saturday has been extended through Sunday
afternoon. /22
LONG TERM /Tuesday Through Friday/...The upper low over the
southeast states will persist through midweek, but gradually
evolve into an open wave. This upper level weakness will then
weaken through the remainder of the long term. The surface low
reflected under the upper low across the deep south will also
slowly weaken, follow by a surface ridge rebuilding across the
northern Gulf of Mexico. Shower and thunderstorm coverage will
increase on Tuesday, with isolated to scattered showers and
thunderstorms continuing through Friday. The increased cloud
cover and convection should knock afternoon temperatures and heat
indices down a few degrees. /22
MARINE...Hazardous conditions for small craft can be expected
late Sat through Sun evening in response to a strong pressure
gradient setting up over the northern gulf waters. this pattern is
from a persistent ridge of high pressure over the central and
northern gulf combined with a weak frontal approaching from the
north stalling near or just north of the coast by late Sun. Most
of the model guidance moves the front offshore by early next week.
32/ee
&&
.MOB WATCHES/WARNINGS/ADVISORIES...
AL...Heat Advisory from 10 AM Saturday to 6 PM CDT Sunday for
ALZ261>266.
FL...Heat Advisory from 10 AM Saturday to 6 PM CDT Sunday for
FLZ201>206.
MS...Heat Advisory from 10 AM Saturday to 6 PM CDT Sunday for MSZ075-
076-078-079.
GM...None.
&&
$$
This product is also available on the web at:
http://weather.gov/mob
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1105 PM CDT Fri Jul 20 2018
.SHORT TERM...(This evening through Saturday)
Issued at 252 PM CDT Fri Jul 20 2018
Isolated showers are redeveloping this afternoon. Clearing skies
and temperatures rising into the upper 70s/low 80s are building
instability. Could see some of these showers develop into
thunderstorms through early evening before losing instability
around sunset. So far, lightning activity has been confined to
northern Minnesota. Coverage is not expected to be particularly
widespread, perhaps 30-40 percent.
Widespread smoke across northwestern Minnesota associated with
wildfires over southern Canada will drift south tonight. Visibilities
range from 2 to 5 miles. The RAP smoke model maintains this plume
overnight into southwest Minnesota, which seems reasonable with an
inversion trapping the smoke near the surface and continued northerly
flow. The MPCA has posted an Air Quality Alert for northwest and
portions of west central/central Minnesota through mid morning
Saturday before better mixing takes over.
.LONG TERM...(Saturday night through Friday)
Issued at 252 PM CDT Fri Jul 20 2018
Overall, models continue to support a cooling trend after the
middle of next week as the mean wind in the boundary layer
contributes to a more Canadian air mass regime.
For the ladder part of the weekend, and into early next week, the
anomalous upper low, which is currently located across the
western Great Lakes, will drift southward and weaken over the next
few days. This will keep deep tropical moisture limited to the
far south in the extended period. The mean upper flow will also
become stronger and westerly early next week as a storm system
moves across southern Canada.
Although PWATs do increase slightly as another weak cold front moves
across the region Monday, most of the energy with this system will
remain in Canada. Thus, any rainfall will be isolated or scattered
in nature and no robust updrafts for strong storms. A more potent
short wave, and a stronger jet streak, will move across the Upper
Midwest the middle of next week. Instability will remain weak as
another front passes through the region. However, with better jet
energy, any thunderstorms could be capable of producing strong wind
gusts.
The end of next week can be characterized as cooler than normal as
the mean upper flow remains northwest. This will likely mean highs
near 80 and lows in the 60s.
&&
.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1104 PM CDT Fri Jul 20 2018
Main concern now is how extensive does stratus get tonight.
Beginning to see the first signs of this stratus showing up to
the northeast of Mille Lacs. RAP/HRRR continue to show this
stratus working toward southwest MN. NAM soundings are certainly
moist in the low levels, but that moisture is relatively shallow,
so it`s hard to say how widespread the stratus will become. At
either rate, LAV continues to show best IFR/MVFR probs at
AXN/STC/RWF, though MSP and MKT could get in on the fun as well.
No rain Saturday, with morning stratus slowly lifting through the
morning. Looks like cloudiest skies will be over MN, with mainly
sunny skies over WI.
KMSP...Still potential for 1k to 1.5k ft cigs to impact the
airport between 10z and 16z Sat morning. Will have to watch how
stratus to the northeast of Mille Lacs Lake evolves.
/OUTLOOK FOR KMSP/
Sun...VFR. Wind NE 5-10 kts.
Mon...VFR. Slight chc -TSRA. Wind vrbl becoming NW 5-10 kts.
Tue...VFR. Wind W 5 kts.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
&&
$$
SHORT TERM...BORGHOFF
LONG TERM...JLT
AVIATION...MPG
Area Forecast Discussion
National Weather Service Tucson AZ
900 PM MST Fri Jul 20 2018
.SYNOPSIS...Isolated to scattered thunderstorms will continue this
tonight and again Saturday afternoon and evening. Then high pressure
will strengthen over the region late this weekend into early next
week resulting very little storm activity and much warmer
temperatures. High temperatures Monday into Wednesday will be much
warmer than normal and likely reaching record levels at some
locations.
&&
.DISCUSSION...Thunderstorms brought some quarter size hail to parts
of Sierra Vista and Corona De Tucson this afternoon. The
thunderstorm activity had diminished this evening, but another round
of storms will be possible tonight. Latest radar and satellite
imagery suggested that this next round was already starting to flare
up across Cochise and Graham counties. The steering flow was from
the east which will track storms westward toward the lower deserts
tonight. Latest HRRR also supported the notion of more showers and
thunderstorms overnight. Current forecast already conveyed this
scenario of nighttime storms, so no updates necessary this evening.
&&
.AVIATION...Valid through 22/06.
ISOLD to SCT TSRA will continue well into this evening and
potentially through 21/10Z before with cloud bases 8-10k ft AGL.
Some clearing expected after 21/12Z then ISOLD-SCT TSRA After an
active thunderstorm day for parts of southeast Arizona, especially
around Sierra Vista and Corona De Tucson where several reports of
quarter size hail were received.will redevelop again after 21/19Z
east and south of KTUS. Outside of strong and erratic TSRA outflows,
surface winds remain below 12 kts through the period. Aviation
discussion not updated for TAF amendments.
&&
.FIRE WEATHER...Isolated to Scattered thunderstorms will continue
into the overnight hours then fire up again east and south of Tucson
Saturday afternoon, although they should be fewer in number. Upper
level high pressure will build over the region significantly
suppressing thunderstorms Sunday through Tuesday so they will be
tough to come by at all outside of the White Mountains although
dewpoints will remain at respectable levels. However, this high will
bring near or record level heat to the area Monday through at least
Tuesday. Later in the week the high shifts to the west allowing
monsoon moisture to begin returning to the area. Winds typically
light for mid-summer with the exception of strong gusty winds near
thunderstorms.
&&
.PREV DISCUSSION...On Saturday, we will gradually begin to
transition to a less favorable thunderstorm environment thanks to
upper level high pressure that will build westward from Texas this
weekend. Still expecting some storms Saturday, just fewer in number
and more limited to higher terrain east and south of Tucson. Also
may end up with a fair amount of cloud cover through the morning
which would hinder development.
Sunday the high approaches and settles overhead Monday through
Tuesday. Sunday there will be very limited convection then Monday
and Tuesday will not likely see much of any development thanks to
the subsidence and mid-level warming. That said, that warming will
impact our temperatures significantly. Heights and temperatures
700mb and above are forecast to be at or above the 99th percentile
for this time of year which translates to hot temperatures Monday,
Tuesday and possibly Wednesday. Unlike June when dewpoints are
typical very low they will be higher this event which will make it
feel warmer yet. We already have an Heat Warning in effect and that
looks great.
There is some question for Wednesday as it will depend on how fast
the monsoon moisture returns over the area behind the departing high.
At a later time we may need to expand the warning into Wednesday at
least for western parts of the area.
By the end of the week temperatures should return to "normal" with
moisture providing for some storms once again.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...
Excessive Heat Warning from 10 AM Monday to 8 PM MST Tuesday for
AZZ501>509.
&&
$$
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