Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/22/17
Area Forecast Discussion...UPDATED
National Weather Service Albuquerque NM
822 PM MDT Fri Jul 21 2017
.UPDATE...
Added pops to portions of the east central for tonight as isolated
thunderstorms have developed from Lea into Roosevelt county most
likely spawned by the outflow boundary from storms farther south.
Recent RAP13 picked up on this activity and hangs onto it until after
midnight, while the HRRR has not yet latched onto anything in that
part of the forecast area. Updated ZFP has been transmitted.
&&
.PREV DISCUSSION...521 PM MDT Fri Jul 21 2017...
.AVIATION...
00Z TAF CYCLE
Plume of moisture stretching from south to north over western and
central NM with drier air over the northeast and east central parts
of the state. Mts occasionally obscured in brief MVFR cigs/vsbys
associated with sct tstms over central and western NM til around 03Z
then transition to mid clouds with sct showers. Wind gusts to around
40kt associated with the stronger storms. Upper high center to the
east of NM to weaken with the high center over the Great Basin
regaining dominance next 24 hrs, which will result in moisture
and convection starting to work into the east aft 22/18Z while
redeveloping over the west and central.
&&
.PREV DISCUSSION...315 PM MDT Fri Jul 21 2017...
.SYNOPSIS...
Much of eastern NM will remain dry today and Saturday, but showers
and thunderstorms will persist across western and central New Mexico.
Locally heavy rain and areas of flooding will be possible. Storm
coverage is expected to increase area wide on Sunday after a boundary
slides down the plains and through the gaps of the central mountain
chain Saturday night. Heavy rain and flash flooding will remain a
threat. Thereafter, the upper level high will build over New Mexico,
decreasing the chances for storms through the middle of the week.
&&
.DISCUSSION...
Abundant dry air remains in place over eastern NM this afternoon,
relegating showers and thunderstorms to central and western NM. So
far, a rather tame set of storms given near 0.99" PWAT on the 12Z
ABQ sounding, and an MCV over the southwest mountains and another
over NE AZ. Additionally, satellite imagery is showing the moisture
plume getting squeezed between the persistent ridge to the east, and
developing ridge to the northwest. With the plume becoming more
focused, combined with the other aforementioned reasons, expect at
least western NM to become more active through the early evening,
with areas of flooding possible. Rainfall rates could exceed 2"/hr.
On Saturday, the ridge to the east of NM will weaken, while the high
to the northwest will strengthen. Meanwhile, the dry air that is
over eastern NM today, may actually advect a bit westward across
central NM around the strengthening high. So, it`s not looking like
as much of an uptick on Saturday as previously thought. However, it
does appear that the northern mountains will remains quite active,
as well the southwest mountains. PWATs won`t change much overall,
perhaps slightly less, so locally heavy rains will remain possible
in these areas.
Saturday night should see an increase in activity at least across
northeast NM. A boundary across Colorado will push southward into
the plains, convectively aided. This boundary will be a focus for
precipitation on Sunday, though the NAM and the GFS are a bit at
odds with regards to how far south and west this boundary will go.
Will hedge closer to the NAM as it is more in line with the ECMWF.
Therefore, there should be plenty of upslope flow across the plains
on Sunday and storms should initiate over the central mountain chain
and spread across at least the northeast plains. Storms may stay
closer to the high terrain across the southeast, but that will
depend on if there are any remnant boundaries from the previous
nights convection. Meanwhile, the high terrain of western NM should
remain active. All-in-all, this may be the busiest day of the next
several. PWATs look to increase some as well, so the potential for
flash flooding remains.
On Monday, the upper high that was to the northwest of NM will build
right over NM. This will result in less convection, though the
mountains will remain active. The high will remain over NM through
at least mid week, thus lesser storm coverage is expected each day.
There will still be storms, but relegated mainly to the mountains.
Could see an increase in storm coverage late in the week if the
upper high can shift a bit eastward.
34
&&
.FIRE WEATHER...
A thin axis of deeper moisture centered over central and western NM
will be the focus for the best coverage of showers and storms with
wetting rainfall through the weekend. Storm motions toward the north
and northwest today will shift more toward the northeast and become
slow and erratic toward the southeast through Sunday. Locally heavy
rainfall with flash flooding is possible mainly for the northern and
western high terrain, especially areas that receive multiple rounds
of rainfall.
A couple models are trending drier for the southeastern half of the
region this weekend. The frontal boundary advertised to shift out of
Colorado doesn`t look as robust and a very dry mid and upper level
airmass to our east is maintaining a tight grip over eastern NM.
Temperatures will remain hot across the east while readings across
the west trend near to below normal. Weaker flow aloft will favor
deteriorating ventilation through the weekend all areas.
There are even more notable changes from models the past 18 hours
that will impact precipitation coverage next week. A dry and hot
upper high center to the east of NM and another gathering strength
over the Great Basin are now shown to choke the moisture plume and
shift the pool of moisture into southwestern NM and AZ beginning
Tuesday. As a result, temperatures have trended warmer through next
week for central and eastern NM while the focus for greater storm
coverage shifts into far western NM and AZ. Ventilation in this
pattern will remain poor/fair for most of the region.
Guyer
&&
.ABQ WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Area Forecast Discussion
National Weather Service State College PA
1024 PM EDT Fri Jul 21 2017
.SYNOPSIS...
Pennsylvania will be on the northern periphery of a subtropical
ridge passing across the southern states through the weekend.
A few rounds of showers and thunderstorms are expected both
Saturday and Sunday, and some could produce gusty winds, hail
and heavy downpours. Another cold front will push through the
area early next week.
&&
.NEAR TERM /UNTIL 8 AM SATURDAY MORNING/...
A boundary dropping southward through PIT is firing off
convection. Dewpoints on one side are in the m60s, and KPIT is
76F. Don`t see that too often in PA. Some of this convection
could slide into the Laurels shortly, but HRRR & RAP - which, to
their credit, do have it there - die it off. Have just mentioned
a shower there through 2-3AM. Dewpoints are high, sky only
partly cloudy, and the air is calm. Fog already in fcst for some
places, and have added fog to the rest of the area, mainly in
the valleys. All the rest of the forecast is in great shape. It
was a dark and muggy night...
Prev...
Convection all but dead. Just a hint of taller cu in the far srn
tier, and the 20 POPs there will expire in an hour or so - right
on time. Other than the high clouds in the N, clearing should
come to much of the area shortly.
Prev...
Weakening MCS traversing WV and approaching the WV and MD
panhandles at mid afternoon. PW pooling around 2" along the
Mason Dixon line and slowly lifting northward should bring
isolated to scattered coverage of showers and thunderstorms
through this evening across my southern tier counties (Laurel
Highlands and South Central Mountains), with mainly dry
conditions expected elsewhere.
remnants of aforementioned MCS track off the mid Atlantic
coastline later this evening, and any diurnally-driven
showers or storms along the southern tier should die out around
sunset. Weak surface ridge passes over PA tonight bringing fair
weather and mins ranging from the upper 50s north to around 70
southeast.
&&
.SHORT TERM /8 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
Large MCS forms upstream overnight and approaches eastern OH in
the pre dawn hours Saturday morning. This feature will be the
main player for potential severe weather on Saturday, as strong
moisture flux and increasing boundary layer convergence point
increase the likelihood of strong to severe storms over PA by
late morning and afternoon.
CAMs differ on timing and strength of MCS evolution ranging from
as early as late morning into my western zones to as late as mid
to late afternoon. Think the former is more likely...given quick
moisture return late tonight and Saturday ahead of the
approaching complex. Warm front pushing into the region on
Saturday will also tend to favor lower LCLs and sufficient shear
for rotating updrafts. Farther north, extensive cloud cover
associated with the warm front will likely result in limited
CAPE Saturday as the 00Z GEFS shows.
&&
.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
A second round of convection is possible Sat night as strong
low level jet and plume of anomalous PWATs works through the
area. Convection associated with this feature could potentially
evolve into another MCS with potential for overnight severe
weather in central PA into Sunday morning.
Favorable scenario for additional severe weather across central
Pa during the daylight hours Sunday as the region will be
within warm sector south of anomalous surface low tracking
eastward along the PA/NY border. Moderate CAPES and moderate
westerly flow aloft, combined with large scale forcing ahead of
approaching upper trough, should support widespread convection
by afternoon.
Some uncertainty continues with regards to timing of upper
trough passage early next week, but additional showers/storms
appear possible. A period of dry and cooler weather appears very
likely by midweek, as upper trough axis finally passes east of
Pa and surface high builds into the area.
&&
.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
Quiet night tonight, with most locales remaining VFR, though the
usual spiderweb of valley fog will settle into the western and
northern mtns. The warm air and high dewpoints will allow for
fog formation early, which will mean IFC cigs will form between
04Z to 08Z. Expect them to continue until 12Z to 13Z. Mainly
partly sunny skies with increasing clouds through the day with
CIGS dropping to MVFR between 18Z to 21Z with showers and
thunderstorms in the vicinity of TAF sites after 18Z progressing
west to east as a warm front pushes into the region.
This will be followed by an upper trough on Sun, which will
keep numerous showers and thunderstorms around over the weekend.
.OUTLOOK...
Sat...AM valley fog possible. TSRA/SHRA likely with
intermittent impacts.
Sun...AM valley fog likely. Cig restrictions likely north.
TSRA/SHRA likely with intermittent impacts.
Sun night...Cig restrictions likely. Scattered TSRA/SHRA.
Mon...AM restrictions likely. Scattered TSRA.
Tue-Wed...Patchy AM fog. Otherwise no sig wx.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...DeVoir
NEAR TERM...Dangelo/DeVoir
SHORT TERM...DeVoir
LONG TERM...Fitzgerald/Gartner
AVIATION...Ceru
Area Forecast Discussion
National Weather Service Duluth MN
715 PM CDT Fri Jul 21 2017
.UPDATE...
Issued at 715 PM CDT Fri Jul 21 2017
Severe thunderstorms were occurring this evening from just north
of Duluth west through the Grand Rapids area into the Pine River
area. Instability has been steadily increasing across the
Northland and the storms have shown little signs of weakening as
they move toward a less unstable airmass to the east. The
afternoon KINL sounding showed dry air in the lower to mid levels
which will enhance the wind threat. Per coordination with SPC,
we`ve added Aitkin, Carlton, and Saint Louis Counties to the
watch. The latest HRRR shows the storms continuing for the next
few hours but gradually decreasing in intensity as they move
further east.
&&
.SHORT TERM...(This evening through Saturday)
Issued at 336 PM CDT Fri Jul 21 2017
Storms have formed over northwest Minnesota this afternoon that we
have been watching very carefully. A severe thunderstorm watch has
been issued, and I will leave it to the reader to refer to the
specifics of that watch in the WCN. A plume of 2000J/KG plus most
unstable CAPE extends up the Red River valley, overlapping much
of western Minnesota and eastern North Dakota and South Dakota. In
addition, this area has decent shear, a weak shortwave aloft and
is underneath the right entrance region of the upper level jet. We
are looking at getting a round of severe storms for the next few
hours, mainly affecting the far western areas of the CWA along the
high cape gradient. After that have poor confidence in additional
storms, though several models bring a second round of convection
through the southwestern half of the forecast area after midnight
tonight.
Attention then turns to Saturday, when the tight upper low/vort
max currently over the Saskatchewan/Manitoba border drops
southeast cross the forecast area during the afternoon and early
evening. Expect that depending on the overnight convection we will
have an additional round of showers and thunderstorms move across
the area during the afternoon and early evening. Depending on the
amount of CAPE we can develop severe weather is a real threat,
but we will have to watch what happens overnight tonight to
determine the daytime threat for tomorrow.
.LONG TERM...(Saturday night through Friday)
Issued at 336 PM CDT Fri Jul 21 2017
The extended forecast period features a couple of chances of showers
and thunderstorms over the Northland, with temperatures forecast to
remain around seasonal averages.
Saturday night begins with continuing chances of showers and storms
from Saturday afternoon as a compact mid-level shortwave dives
across our north and eastern areas of the CWA Saturday night. There
should be some good forcing associated with this shortwave as there
is a large lobe of positive vorticity advection, along with higher
850-300 mb omega, per the Thaler QG analysis. The Storm Prediction
Center currently has the entire Northland in a Slight Risk of severe
weather for the Day 2 convective outlook. The magnitude of
instability from 00z Sunday between the synoptic models differs
somewhat, with values ranging between 300 up to 2000 J/kg between
the GFS/NAM/ECMWF/CMC models. The expectation is that any strong to
severe convection on-going at 00z Sunday will dissipate as the sun
sets, decreasing instability rapidly. There could be some damaging
winds and large hail possible, if some strong convection continues
into this period. As the shortwave departs, there may be some
lingering showers Sunday morning as the region remains under the
cyclonic flow of the mid-level wave. Non-zero MUCAPE could provide
enough instability for a rumble of thunder, but no severe weather
expected at this time.
By Sunday afternoon, drier conditions will return to the Northland,
as sfc high pressure builds. Skies look to clear out overnight
Sunday into Monday morning, so there could be some patchy fog,
especially over areas that receive rainfall Sunday. Winds look to be
light as well, especially over the Minnesota Arrowhead and along
Lake Superior. Dry conditions will continue through the day Monday
before another area of low pressure develops over northern Manitoba
and northwest Ontario Canada, bringing a cold front boundary through
the Northland. The GFS/ECMWF/CMC models are showing some decent
agreement with the areal coverage and timing of precipitation, so
confidence is fairly high this precipitation will move through
Tuesday morning and afternoon.
Temperatures will be around seasonal averages, with highs in the 70s
across the Northland.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 715 PM CDT Fri Jul 21 2017
Strong to severe storms were occurring across portions of the
Northland this evening and they will continue to move east. IFR or
LIFR conditions will occur in and near the storms along with
strong winds and hail. Outside of the storms, expect mainly VFR
conditions this evening but IFR or MVFR ceilings will expand later
tonight into Saturday morning before lifting to VFR. Additional
showers/storms will be possible through the night and again
Saturday as a frontal boundary and upper level trough impact the
area. Updates to the chance for storms will be needed as we
progress through the period.
&&
.PRELIMINARY POINT TEMPS/POPS...
DLH 59 73 57 70 / 50 40 40 20
INL 60 77 56 74 / 40 60 40 20
BRD 65 83 60 75 / 50 10 10 10
HYR 63 80 58 71 / 20 40 30 20
ASX 58 74 56 67 / 10 30 30 30
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
WI...Beach Hazards Statement until 8 PM CDT this evening for WIZ001.
MN...Beach Hazards Statement until 8 PM CDT this evening for MNZ037.
LS...None.
&&
$$
UPDATE...Melde
SHORT TERM...LE
LONG TERM...JTS
AVIATION...Melde
Area Forecast Discussion
National Weather Service Flagstaff AZ
310 PM MST Fri Jul 21 2017
.SYNOPSIS...Expect very active monsoon conditions for the next
several days. Local heavy rainfall capable of producing flash
flooding remains possible from stronger storms.
&&
.Discussion...Another active day across northern Arizona today.
Storms are generally moving from northwest to southeast and
producing locally heavy rain and flooding issue--especially over
recent fire scars. A few storms also show (on radar) indications of
one inch or larger hail.
Showers and thunderstorms will decrease in coverage after dark
tonight. However, other storms/storm clusters could develop
overnight. HRRR is showing the Northeast and White Mountains as the
favored areas for development overnight.
For Saturday and Sunday...The forecast models are still insisting
that a northeast to southwest flow sets up across Arizona in
response to high pressure becoming centered over
Nevada/Utah/Arizona. The described flow pattern will deliver a drier
air mass to the northeast corner of Arizona with a decrease in
shower and storm activity. From the Mogollon Rim and White Mountains
southward and across central Arizona monsoon moisture will remain
entrenched with a good chance of showers and storms each day.
From Monday onward...Moisture will remain in place with the threat
for daily showers and thunderstorms continuing.
&&
.AVIATION...For the 00Z package...Expect scattered to numerous SHRA
and TSRA lasting into early evening, with isolated +TSRA. MVFR/IFR
in the stronger storms. Shower and thunderstorm coverage gradually
decreasing after 03Z. Other thunderstorm development is also
possible through the night. More storms are expected again after 17Z
Saturday. Aviation discussion not updated for TAF amendments.
&&
.FIRE WEATHER...Active monsoon conditions will continue through
Saturday with scattered to numerous showers and thunderstorms. Heavy
rain and gusty winds will remain the primary impact. Expect near
average temperatures across the area.
Monday through Wednesday...Daily chances for showers and
thunderstorms continue, favoring the Mogollon Rim southward Sunday,
then all of northern Arizona Monday and Tuesday.
&&
.FGZ WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
PUBLIC...MAS
AVIATION...MAS
For Northern Arizona weather information visit
weather.gov/flagstaff
Area Forecast Discussion
National Weather Service Grand Rapids MI
947 PM EDT Fri Jul 21 2017
LATEST UPDATE...
Update
.SYNOPSIS...
Issued at 815 PM EDT Fri Jul 21 2017
An area of low pressure will track eastward along the quasi-
stationary front just south of Michigan tonight into Saturday.
It will keep most of the strong storms closer to I-80 than I-94.
There will be some periods of light rain tonight over areas near
and south of Grand Rapids with the risk of thunderstorm around
midnight west of Battle Cleek, near and south of I-94. A few
instability thunderstorms are possible Sunday and the truly cooler
air moves into the area.
Canadian high pressure will move through the area early next week
bringing slightly cooler than normal temperature and considerable
sunshine.
&&
.UPDATE...
Issued at 946 PM EDT Fri Jul 21 2017
The thunderstorm complex continue, for the most part, tracking
southeast. Watching the individual cells in the storm complex
over WI, IA, IN and IN most of the cells are tracking southeast
too. However over the past 1/2 hour one cell just south of the
city of CHI is tracking northward. Likely this is some sort of
boundary interaction. On the other hand the RAP and HRRR low level
jet shows a surge northward just ahead of the MCV assoicated with
the complex of storms near CHI moves across Southern Lake
Michigan and Northern Indiana over the next few hours. It is more
than possible a few storms could make it into Van Buren and
Kalamazoo Counties in the 11 pm to 2 am time frame. Otherwise near
and north of I-96 it would seem to me there little if any threat
for thunderstorms tonight.
The way the surface wave tracks across the CWA Saturday it would
seem the instability will stay south of I-94 most of the day. I
see very little chance of showers so I lowered the POP over most
of the area through the afternoon.
UPDATE Issued at 815 PM EDT Fri Jul 21 2017
It seems to this forecast that the threat for any serious severe
storms is once again been trumped by the frontal boundary being
closer to I-80 than I-96. While there is a real surface wave on
that front, and that will allow some storms to track east to east
southeast just north of the warm front, that warm front does not
really push northward into our area overnight. That tells me the
significant convection will also stay south of our area.
Going along with this idea of you look at the SPC-HRRR model
browser and look at the trends of models heavy rainfall between
17z runs and the 22z run for any hour between 01z and 09z, the
heavy rainfall is father south with each run. So the trend suggest
the strongest convection will miss our CWA to the south.
The best chance for any thunderstorms would be west of Battle
Creek along and south of I-94 between 11 pm and 2 am as the best
support moves through this area.
As a result I trended back on the precipitation (POP) threat and
put the significant QPF significantly farther south. I may have
to do cut back on the QPF even farther later this evening.
&&
.SHORT TERM...(This evening through Sunday night)
Issued at 330 PM EDT Fri Jul 21 2017
Very high precipitable water values will mean we will have to
monitor radar trends for excessive rainfall tonight. The model
guidance including the HRRR and NCAR models have trended further
south with the higher risk of storms tonight but the southern
forecast area may still get clipped by the organized storms which
will also bring the threat of strong winds.
We have adjusted POPs and QPF further south and lowered POPs on
Saturday based on the belief that convection tonight will impede
instability and moisture transport on Saturday.
.LONG TERM...(Monday through Friday)
Issued at 330 PM EDT Fri Jul 21 2017
The weather to start the period will be characterized by a mid level
ridge which will be building in from the Upper Plains. This feature
will help to dry the airmass out and lead to a cooling trend with
the temperatures. Will feature dry conditions for Monday and
Tuesday as the surface high tracks through.
Mid level height falls occur over the Great Lakes region as we go
into Wednesday and Wednesday night. This will be the result of an
upper low that will be tracking eastward from Ontario into Quebec.
Models are in reasonable agreement on the timing and track of this
system. Thus some showers look possible ahead of and along the cold
front associated with this system With instability developing as
well... a risk for a few storms exists. Overall the forecasted
forcing and instability look weak...so will only go with a low
chance for measurable precipitation.
The atmosphere then dries out for the end of the week as a northwest
flow and subsidence develops behind the departing front. The new
High Res Euro does stall the front out just south of the MI border
on Thursday and tracks a weak surface wave along it. If this system
trends further north with time...some rain may occur for southern
parts of the CWA.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 815 PM EDT Fri Jul 21 2017
For the most part the convective threat is south of our TAF sites
tonight. Still I could see, being north of the surface wave
tracking along the front to our south, there will be an area of
low clouds and light fog Saturday morning. This should clear by
mid afternoon but that will not be long enough to allow enough
instability for afternoon thunderstorms. My bottom line to this
is VFR most of the night (threat of thunderstorms best at AZO
after 05z). The other TAF sites are to far east or north to be
impacted by this event.
&&
.MARINE...
Issued at 330 PM EDT Fri Jul 21 2017
Winds and waves will generally remain relatively light through the
weekend. The exception could be for some gusty winds and higher
waves tonight in strong thunderstorms south of Muskegon and
Saturday morning south of of South Haven. There could be some
dense fog at times through Saturday before drier air moves in.
&&
.HYDROLOGY...
Issued at 330 PM EDT Fri Jul 21 2017
The favored region for locally heavy rainfall through early Saturday
will be south of I-96 and particularly near the MI/IN border. Hi res
models have trended further south with thunderstorm activity
overnight into Saturday morning due to poor handling of earlier
convection. Therefore, the risk for heavy rainfall has shifted
accordingly. Localized flooding will still be possible where any
storms persist. This may be more of a concern near I-94 and toward
the MI/IN border. Rises of small rivers and streams will be possible
but it is not looking like the main stem rivers will have any big
issues unless convective trends change significantly.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&
$$
UPDATE...WDM
SYNOPSIS...WDM
SHORT TERM...Ostuno
LONG TERM...MJS
AVIATION...WDM
HYDROLOGY...Hoving
MARINE...Ostuno
Area Forecast Discussion
National Weather Service Wilmington OH
948 PM EDT Fri Jul 21 2017
.SYNOPSIS...
Multiple disturbances are expected to bring several rounds of
showers and thunderstorms to the region through the weekend and
into early Monday. High pressure and dry conditions are then
expected for Tuesday. More disturbances in northwesterly flow
aloft will cross the region later in the week.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
A very humid air mass remains in place over the ILN CWA, with
the 00Z KILN sounding indicating an unstable and uncapped
environment. Forcing has been the missing factor through most of
the day, though a few isolated storm clusters developed near
Cincinnati, and a weak boundary (part of a tailing boundary from
an earlier MCV) is now starting to ignite near Wilmington.
Nonetheless, with overall support for organized ascent rather
weak, and no shear to speak of, activity through the first half
of the overnight is not expected to be more than intermittently
strong (and unlikely to be severe).
A much different scenario is expected for the second half of the
overnight period, as an environment much more favorable for
organized storms gradually advects to the ESE out of northern
Illinois. The thermodynamic environment over the ILN CWA (and
downstream of existing convection) will be entering its usual
min, which may lead to some storms becoming elevated with time,
as indicated by RAP/HRRR soundings. What these storms will bring
is their own source of forcing (low level convergence ahead of
another developing MCV) and shear (increasing 30-35 knot
westerly 850mb flow). These factors should help the storms stay
strong to severe, at least for portions of the line/MCS/cluster,
even as the storms make it into the ILN CWA somewhere in the
3AM-6AM time frame. Current storm trajectories, storm-level
flow, and recent HRRR runs would suggest the greatest threat for
strong storms will be in the northern third of the forecast
area. Nonetheless, eventual propagation toward instability will
likely lead to more of the area being impacted in some way. PoPs
have been increased and re-focused in terms of timing and
placement, based on this latest forecast information.
Finally, added some fog to the forecast for the areas where
heavy rains occurred from Cincinnati southeastward.
Previous discussion >
Apparent temperatures were expected to remain
at or over 100 in the southwest, which had me extend the current
advisory into the overnight hours as the eastern portion of it
drops off later today.
Upstream thunderstorm complex west of Indianapolis and a shower
complex underneath the MCV northeast of Indy will work into the
CWA later this afternoon into this evening. Expect convection to
be possible almost anywhere this evening but with a higher
propensity southwest of a Richmond/Lebanon/Georgetown line.
Overnight should see convection from this evening waning, but
another upper level disturbance will ride southeast in the mean
flow and cross northern Ohio. Storms from this will primarily
affect the I-70 corridor and northward, with isolated activity
possible elsewhere late overnight.
Confidence in the occurrence and/or placement of these storm
clusters is low. Forecast will be dynamically updated as storms
fire and a better timing and areal extent of them are able to be
extrapolated in both time and space. With this being said,
forecast is probably too low on pops overnight in the northern
CWA where it was limited to chance category.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
Saturday had me bring another tier of counties into the heat
advisory fold as unusually warm dewpoints solidly in the middle
70s combine with temperatures in the low 90s to push apparent
temperatures over the 100 degree mark.
Storms that are present in the morning should be focused north
of and along the I-70 corridor, but a few models are indicating
some isolated activity popping south of it just before daybreak.
The outflow boundary that lays out along the I-70 corridor later
in the day is expected to be a focus for a second round of
development, given an added boost by a continued feed of moist
and unstable air on southerly winds. Storms will fire along a
w-e oriented line and then move south in the evening.
Any storm in the next few days will have a higher potential for
damaging winds and especially very heavy rainfall. The tornado
and large hail threat appear to be negligible at this moment in
time.
Storms will weaken and diminish as they move south to the Ohio
River on Saturday night. Dewpoints will remain in the middle 70s
until the airmass changes beyond the short term period.
&&
.LONG TERM /SUNDAY THROUGH FRIDAY/...
A weak trof/boundary is forecast to push through the region on
Sunday. This feature may be entering our far eastern/southeast
zones by peak heating which would bring the highest PoPs to these
locations. All in all, just have slight chance/chance of
showers/storms. SPC has a slight risk for severe storms. There could
be an isolated severe during the afternoon due to diurnal heating.
For the period Sunday night into Monday night, mid level trough will
dig southeast across the Great Lakes/eastern Canada. As this occurs,
a cold front will move slowly southeast through our region. With the
lack of strong low level forcing and upper level support, the
chances for showers/storms appears low and should affect our
eastern/southern zones in the afternoon on Monday. Skies should
become at least partly cloudy Monday night as high pressure builds
into the region from the north with a drying and stabilizing air
mass.
High pressure should remain over the region through at least Tuesday
into Tuesday night with dry weather expected.
As the high moves east on Wednesday, return flow and increasing
moisture may lead to a small chance of showers and thunderstorms.
Models indicate that the next frontal boundary to affect our region
will be during the Thursday/Friday time frame. Differences are seen
in the timing, so a broad brush forecast has been used with a chance
of showers and thunderstorms.
Temperatures will cool back down to more July normals Tuesday
through Friday.
&&
.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
While VFR conditions will prevail through the evening, an area
of thunderstorms will move through the Cincinnati area over the
next hour or two, possibly bringing MVFR/IFR TSRA conditions to
the CVG/LUK TAF sites. Some MVFR visibilities are possible with
an area of rain moving into CMH/LCK as well.
Later in the overnight period, a larger complex of thunderstorms
is expected to move into the region, affecting the northern four
TAF sites near daybreak. These storms have now been specifically
included in the TAFs, and future forecasts may need to forecast
further reduced conditions (lower ceilings / higher winds) with
the storms. It is most likely that these storms will remain
north of Cincinnati. Outside of the storms, some MVFR
visibilities are also possible at the Columbus airports.
After a break in the activity through late morning and early
afternoon, additional thunderstorm development will be possible
going into the afternoon and evening. Southwest winds will
increase to around 10-15 knots.
OUTLOOK...Thunderstorms will be possible again from Saturday
night through Sunday, and then again on Wednesday.
&&
.ILN WATCHES/WARNINGS/ADVISORIES...
OH...Heat Advisory from 1 PM to 7 PM EDT Saturday for OHZ070-071.
Heat Advisory until 7 PM EDT Saturday for OHZ077-078.
KY...Heat Advisory until 7 PM EDT Saturday for KYZ089>096.
IN...Heat Advisory from 1 PM to 7 PM EDT Saturday for INZ066.
Heat Advisory until 7 PM EDT Saturday for INZ073>075-080.
&&
$$
SYNOPSIS...Franks
NEAR TERM...Franks/Hatzos
SHORT TERM...Franks
LONG TERM...Hickman
AVIATION...Hatzos
Area Forecast Discussion
National Weather Service Lincoln IL
901 PM CDT Fri Jul 21 2017
.UPDATE...
Issued at 901 PM CDT Fri Jul 21 2017
Current forecast grids have already been updated once, but will be
making further adjustments to mainly pops/wx and severe watch. All
convection has remained north of the CWA this evening and based on
current radar trends looks like it will remain north of the CWA
remainder of the evening and possibly into the overnight hours.
However, additional precip is expected to develop along the
boundary out west and then move into northern IL again overnight.
Convection therefore is still possible in northern part of the CWA
overnight and will maintain some pops up there. Will be making
adjustment to evening pops across the north to account for current
trends. Update should be forthcoming.
&&
.SHORT TERM...(This evening through Saturday)
ISSUED AT 300 PM CDT Fri Jul 21 2017
19z/2pm surface analysis shows a 1006mb low over northeast
Nebraska...with a warm front extending eastward along the I-80
corridor. A large cluster of showers/thunderstorms has been
ongoing throughout the day northeast of the low over southeast
Minnesota into Wisconsin. As a result, an impressive instability
gradient has developed from north to south across Iowa, with
SBCAPEs of 5000-6000J/kg south of the boundary in southern Iowa.
A new cluster of storms has recently developed along this boundary
near the Iowa/Nebraska border. The HRRR has been consistently
showing convection firing in this area for the past several runs,
with the storms then developing/tracking E/SE along the boundary
into north-central Illinois this evening. Given the extreme
instability feeding into the storms, think they will quickly form
robust updrafts and become severe across central Iowa over the
next couple of hours. Once a cold pool can develop, the storms
will then begin racing E/SE along the instability axis into
north-central Illinois by mid to late evening. While the main push
will likely be along the I-80 corridor, think areas as far south
as I-74 will feel the impacts as well. Based on latest HRRR, have
introduced likely PoPs across the NW KILX CWA around Galesburg by
02z/9pm. Have then spread likely PoPs E/SE along/north of I-74
into the overnight hours. As the initial convective system pushes
east, a trialing band of showers/thunder will gradually sink
southward to I-72 toward dawn Saturday. Further south, have kept
the southern half of the CWA dry through the entire night. As it
stands now, think the biggest threat for severe weather and
potentially damaging wind gusts will focus along/north of I-74
between 9pm and 3am.
Scattered showers and thunderstorms will linger across the
northern CWA through mid-morning Saturday before dissipating.
May see some re-development along the cold front later in the
afternoon: however, subsidence in the wake of the morning
convective system may act to suppress widespread development
initially. As a result, will only carry low chance PoPs
during the afternoon. Areal coverage of convection will likely
increase across the southern half of the CWA Saturday evening as
the front sinks further south. High temperatures on Saturday will
once again climb well into the 90s...with peak afternoon heat
index readings of 105-115 degrees.
.LONG TERM...(Saturday night through Friday)
ISSUED AT 300 PM CDT Fri Jul 21 2017
Front will sink into the Ohio River Valley on Sunday: however, a
trailing weak trough axis may trigger isolated thunderstorms. Once
this feature passes, high pressure will build into the region
early next week...allowing a cooler/less humid airmass to take
control. High temperatures will drop into the lower to middle 80s
for both Monday and Tuesday, then will slowly climb back into the
middle to upper 80s by Wednesday. There are still some
discrepancies among the synoptic models later next week, but
consensus suggests the next significant chance for rain will hold
off until late Wednesday night through Friday as a slow-moving
frontal boundary comes into the picture.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 646 PM CDT Fri Jul 21 2017
Main short-term aviation concern will be convective trends through
the evening. Latest radar imagery continues to show a cluster of
thunderstorms over eastern Iowa, moving E/SE along a stationary
frontal boundary draped across northern Illinois. Based on radar
timing tools, it appears these storms will remain north of the
I-74 terminals later this evening. Once this initial surge of
storms passes to the north, trailing cells will gradually settle
southward overnight into early Saturday morning. As a result, have
introduced VCTS at KPIA/KBMI/KCMI between 09z and 14-15z. A cold
front will drop into central Illinois on Saturday, triggering
scattered thunderstorms by late afternoon. Based on expected
location of boundary at peak heating, have included VCTS at
KSPI/KDEC after 21z. Winds will initially be from the S at less
than 10kt this evening, then will veer to the W/NW by Saturday
afternoon as the front arrives.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
Excessive Heat Warning until 8 PM CDT Saturday for ILZ027>029-
036-037-040>042-047>054-061-062-066>068-071>073.
Heat Advisory until 8 PM CDT Saturday for ILZ030-031-038-043>046-
055>057-063.
&&
$$
UPDATE...Auten
SHORT TERM...Barnes
LONG TERM...Barnes
AVIATION...Barnes
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1044 PM EDT Fri Jul 21 2017
.UPDATE...
Issued at 1044 PM EDT FRI JUL 21 2017
Another cluster of showers and thunderstorms developed further
north of the area, along the outflow from the earlier convection
this evening. The remnants of this, have been spreading some
light rain across our far northeast counties. Have held onto some
some isolated showers over the next hour or so, as this remnant
gradually diminishes off to the east, while any new convection
initiates further northeast into southern Ohio. Otherwise, mostly
clear skies reign south of I-64, with temperatures ranging from
the mid 70s in the cooler valleys, to the lower 80s in some of the
broader valleys and ridgetops. Organized convection upstream in
Illinois and Indiana will spread some high clouds near and north
of I-64 by around 06z and thereafter, but the associated
precipitation continues to look to stay north of our area through
the overnight. Updates have been sent.
UPDATE Issued at 758 PM EDT FRI JUL 21 2017
Isolated convection initiated north of I-64 early this evening.
This is on the demise now, as outflow from earlier storms
gradually lifts to the northeast. Ongoing more organized
convection up in Illinois looks to stay to our north through the
rest of the night, so will keep the area dry. Consequently, have
reduced the sky cover and played up the valley fog a bit more.
Lows generally in the low to mid 70s looks on target, although did
nudge a few valley readings down a bit more based on the trends in
observations. Updates have been sent.
&&
.SHORT TERM...(This evening through Saturday night)
Issued at 325 PM EDT FRI JUL 21 2017
Convection associated with the MCS that moved across OH affected
the northern part of our forecast area this morning, but the
convection quickly dissipated as it moved into the northern part
of our forecast area. A couple of outflows were associated with
this with one pushing into VA where more convection was triggered,
and a secondary residual boundary which remains across the
central part of the forecast area. It is still possible something
could develop along this residual boundary late this afternoon
and evening.
Satellite also shows an MCV across IN with convection beginning
to develop in west central IN, and there is yet another MCS across
WI. The HRRR is not showing much development this evening over
IN with the MCV, but latches onto the system now in WI.
Both the NAM and GFS point towards the possibility of convection
across the north early tonight, possibly associated with the
Indiana MCV. The ECMWF points towards a chance in the north closer
to dawn as the main MCS now in WI passes by to our north. For the
near term forecast have leaned towards the HRRR with support from
the ECMWF. This results in lower rain chances for tonight than
either the GFS or NAM MOS.
As we move into Saturday another steamy day is on tap with maximum
forecasts mostly in the lower 90s and heat indices near 100. How
much convection we see on Saturday is still in question and
followed the standard model blend for rain chances Saturday.
.LONG TERM...(Sunday through Friday)
Issued at 325 PM EDT FRI JUL 21 2017
The period begins with a upper level short wave trough and
associated surface low pushing SSE across the northern Great
Lakes. This will progress on into the northeastern U.S. early next
week, with the associated cold front moving across our area on
Monday. At this point it appears the best chance for showers and
storms will be Sunday afternoon even though the front won`t clear
the area until Monday. The front looks to stall to our south next
week. This will result in temperatures closer to normal, but with
at least a small chance of daily showers and storms especially in
the southern part of the forecast area.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
ISSUED AT 758 PM EDT FRI JUL 21 2017
Mainly VFR conditions will prevail through the period, as we
remain under the influence of an upper level ridge. Some MVFR or
worse fog will be seen in the deeper valleys once again between 06
and 12z. Some relatively drier air did mix down at SME and LOZ
late this afternoon into the early evening hours. As such, have
only kept a temporary window of MVFR fog at SME to between 09 and
12z. Isolated to scattered convection will threaten eastern
Kentucky during the afternoon hours, and have included VCTS at
all sites by 16z Saturday. Light and variable winds through the
night will increase to between 5 and 10 kts out of the west
southwest by Saturday afternoon.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...GEOGERIAN
SHORT TERM...SBH
LONG TERM...SBH
AVIATION...GEOGERIAN
Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
729 PM CDT Fri Jul 21 2017
.SHORT TERM...(This evening through Saturday)
Issued at 307 PM CDT Fri Jul 21 2017
The model consensus of the RAP, HRRR, NAM and HRRR exp appear to be
keying on a disturbance moving through Ncntl Colo as the forcing for
storm development across Swrn Neb this evening. WPC has put Ncntl
Colo on notice for heavy rainfall potential and what develops out
west should grow upscale into Swrn Neb tonight.
The HRRR appears to generate heavy storms from the robust CAPE
across Ncntl Neb. This instability forms ahead of a cold front
moving through Ncntl Neb which could form a strong cluster of
thunderstorms late this afternoon and this evening.
850mb winds this evening become northeast and this should support
upslope theta-e advection into Colorado supporting the model
consensus and the WPC heavy rain discussion. This storm activity
would be late evening and overnight across Swrn Neb. Precipitable
water will be 1.5-1.75 inches supporting locally heavy rainfall.
Thunderstorms may redevelop Saturday afternoon across Swrn Neb. The
stronger storm activity could easily be across Scntl Neb near the
Sfc front but h850mb winds are east across Swrn Neb which could
support storms near and south of Interstate 80.
The temperature forecast tonight uses blended bias corrected
guidance for lows mostly in the 60s. Blended guidance plus bias
correction produced highs in the upper 80s to mid 90s Saturday.
.LONG TERM...(Saturday night through Friday)
Issued at 307 PM CDT Fri Jul 21 2017
Whatever rain activity that forms Saturday should move south
Saturday evening. Moisture decreases markedly by Sunday morning but
begins to increase Monday as return flow develops. Opportunities for
thunderstorm development Monday through Friday revolve around
genesis off the Black Hills and Laramie Range.
The subtropical upper level ridge retrogrades Sunday and Monday
setting up northwest flow aloft. Storm development could be off the
Black Hills Monday. Thereafter, the upper level ridge builds east
and a ridge runner pattern sets taking storms through SD, perhaps
affecting Nrn Neb. POPs are lofty in the 30 to 40 percent range
which could be a stretch given the drought conditions underway.
POPs across Wrn Neb are mostly isolated which is appropriate given
the developing thermal ridge and associated capping mechanism.
The temperature forecast uses bias corrected model data from the
ECM, GFS and GEM. This was close to the national blend of model and
guidance data. Highs in the 90s will be common. The upper level
ridge will build back toward the cntl Plains Tuesday through
Thursday presenting a potential heat wave. H700mb temperatures rise
to 14-16C during this time. The models have been slow to adjust with
temperatures. The GFS gives 90s to near 100 for highs those days.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 726 PM CDT Fri Jul 21 2017
Isolated strong to severe thunderstorms between KODX and KONL in
north central Nebraska this evening. Baseball hail reported with
the southern storm. Storms to move out of northeast Colorado
through the early morning hours of Saturday. Have carried vcts at
KLBF.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM CDT /7 PM MDT/ this evening for
NEZ005>010-025>029-037-038-059-070-071.
&&
$$
SHORT TERM...CDC
LONG TERM...CDC
AVIATION...Power
Area Forecast Discussion
National Weather Service Melbourne FL
905 PM EDT Fri Jul 21 2017
.UPDATE...
Tonight...The early onset of convection has resulted in an early
end. The GFS shows high moisture remaining over the area, but the
evening soundings actually look a little drier than the model. The
GFS only generated light precip overnight while the HRRR indicates a
dry forecast. Have already updated the forecast to take out POPs
for the overnight period.
&&
.AVIATION...VFR until convection initiates tomorrow. Don`t see any
sources of subsidence/drying so expect the atmosphere will remain
very moist. The east coast sea breeze development early in the
afternoon should start things off again, so have vicinity thunder at
the coastal terminals at 17z. Boundary interactions will then build
storms inland and have vicinity thunder at the interior sites at
18z. Some drier/cooler mid level air should promote a potential for
strong wind gusts and frequent lightning strikes.
&&
.MARINE...
Tonight-Sat...Suppressed surface ridge axis will produce a
south/southwest gradient wind flow. Speeds look 10 knots or less.
The Wave Watch continues to have a high bias on seas, albeit only
about 1 foot. Buoy observations have shown seas 2 feet or less with
3 feet way offshore at 41010. Therefore will have seas 2 feet or
less, except up to 3 feet well offshore (and that is probably even
too generous).
&&
.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...None.
&&
$$
Forecasts...Lascody
Impact Wx/Radar...Weitlich/Combs
Area Forecast Discussion
National Weather Service Mount Holly NJ
1126 PM EDT Fri Jul 21 2017
.SYNOPSIS...
A very warm and humid air mass will remain over the area
through this weekend and possibly into Monday. Meanwhile, low
pressure along a roughly west to east frontal boundary will
result in periods of showers and thunderstorms. By Tuesday, high
pressure will build over the area bringing somewhat milder and
drier conditions through through the middle of next week. A
seasonally strong cold front may cross the area later in the
week.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Amended the forecast overnight to increase PoPs south of the
Mason-Dixon Line, where an isolated storm has tracked eastward
from near the Baltimore metro to Chesapeake Bay. The latest HRRR
and NAM Nest (00Z) indicate that more storms may initiate
through the night in advance of a weak perturbation moving
through the southern Mid-Atlantic. Radar rainfall rates are
fairly excessive with this storm, and given the slow storm
motion and very high PWs in place downstream of the storm, some
localized heavy rainfall is possible. Should more storms develop
and/or the isolated storm intensify, the grids may be updated to
include more enhanced wording.
A light and variable wind is forecast for tonight. Low temperatures
should range from the middle 60s in the elevated terrain up north to
the 70s in the Philadelphia metropolitan area, southern New Jersey
and on the upper Delmarva.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
Some updated thoughts on this period...
The first is that there is large spread in forecast temperatures
tomorrow, likely owing to some uncertainty regarding the speed
with which convection moves into the area (and downstream
clouds hindering temperatures from maxing out during the
afternoon). However, observations the past two days suggest that
heat indices have tended to reach their maxima in the late
morning (when dew points have not mixed out substantially).
Though clouds may be present in the morning (in association with
a perturbation moving through the southern Mid-Atlantic), I am
somewhat worried the combination of temperatures and dew points
will be quite uncomfortable once again in the urban corridor. My
feeling is some heat product will be necessary again,
particularly since this will be the third day with heat indices
flirting with or exceeding the century mark. The 00Z NAM MOS
numbers are quite cool (90 at KPHL), owing to more clouds.
However, the GFS MOS is much warmer (95 at KPHL) with dew points
likely to be higher than today. MOS has overdone temperatures
the past couple days (though not by much), so although there is
quite a bit of uncertainty regarding meteorological criteria
being reached...the factors of it being a weekend day, the
prolonged nature of the ongoing heat, and the potential for heat
issues to be reached relatively early in the day all point to
the need for some sort of heat-related advisory or warning. Will
make the final decision with the 330 am update.
The second regards severe/flood potential. There remains large
uncertainty with the evolution of upstream convective
clusters/complexes as they move along a quasi-zonally oriented
boundary from the Ohio Valley to the southern Mid-Atlantic.
High-resolution output has large variability in timing/location
of the convection, but there are consistent indications of
strong convection (combination of substantial instability and
fast midlevel flow) and multiple rounds of storms (as upscale
growth of initiating convection allows for downstream
propagation along the aforementioned boundary) beginning late in
the day. This leads to some concern regarding both severe
storms and hydrologic issues. More details to come with the 330
am package, but some enhanced wording in the grids will probably
be necessary at minimum.
&&
.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
The extended period starting Saturday night features a
transition in the flow aloft from roughly zonal flow across the
northern US to a somewhat more amplified pattern with troughing
over the east US by the latter part of next week. In terms of
weather this translates to very warm/hot and humid conditions
this weekend transitioning to a milder and somewhat drier period
for at least part of next week.
A quasi-stationary east-west frontal boundary is expected to
persist across the area through the weekend, although it may
lift north a bit on Sunday. Low pressure along the front will
favor low-level convergence and areas of showers and
thunderstorms. PWAT values near 2 inches will support some
heavy downpours and possible flooding. Also SPC has a slight
risk of severe for Saturday and Sunday. Timing is tricky but
there is some indication of more likely precip for Saturday
night and possibly again Sunday night.
By Monday morning a fairly pronounced shortwave trof is forecast
to be over the Great Lakes and move east to New England by
Tuesday morning. The GFS is a bit slower than the ECMWF, but
either way the trof should force a cold front across the mid-
Atlantic and offshore by Tuesday morning. With the frontal
passage on Monday there will be a continued good chance for
aftn/eve t-storms. Max temps on Monday ahead of the front look
to be still a few degrees above normal.
Tuesday and Wednesday should be relatively pleasant with shrtwv
ridging aloft and surface high pressure moving across the area.
The high is associated with a somewhat cooler and drier air
mass. Looks like some low-level warm advection develops
Wednesday night and the forecast carries a chance of showers at
that time. Chance of precip increases on Thursday as another
shrtwv trof and associated cold front approach from the NW.
&&
.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
VFR conditions are forecast for much of the overnight and Saturday.
Showers and strong thunderstorms are expected to approach from
the west late in the day. They should begin arriving around KRDG
and KABE about 2100 to 2200Z, and they are expected to reach
KTTN, KPNE, KPHL and KILG around or shortly after 2300Z.This
timing will be fined out as new information comes in during the
overnight hours.
A light and variable wind overnight becomes west to southwest
on Saturday.
OUTLOOK...
Saturday Night through Monday...Generally VFR conditions
expected, but temporarily lower cigs/vsbys in scattered showers
and thunderstorms are likely at times.
Tuesday and Wednesday...VFR conditions.
&&
.MARINE...
The wind is expected to favor the southwest around 10 knots
tonight and it should back to the south for Saturday. Wave
heights on our ocean waters will remain around 2 feet and waves
on Delaware Bay should be 1 to 2 feet.
Scattered showers and thunderstorms may affect the coastal waters of
Delaware and far southern New Jersey, as well as Delaware Bay,
tonight.
OUTLOOK...
Generally sub-SCA conditions are expected Saturday night through
Wednesday. However winds and seas may be locally higher in
scattered thunderstorms over the waters from Saturday night
through Monday.
RIP CURRENTS...
The energy associated with the underlying 10 to 14 second
southeasterly swell continues to weaken and the 6 second south
southeast swell has become prominent. As a result, we will continue
to carry a low risk for the development of dangerous rip currents
for the balance of today and the same should be true for
Saturday.
&&
.EQUIPMENT...
Dewpoint values at KDOV continue to run a few degrees over
actual.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...None.
&&
$$
Synopsis...AMC
Near Term...CMS/Gaines/Iovino
Short Term...CMS
Long Term...AMC
Aviation...AMC/Gaines/Iovino
Marine...AMC/Gaines/Iovino
Equipment...Staff
Area Forecast Discussion
National Weather Service Tucson AZ
110 PM MST Fri Jul 21 2017
.SYNOPSIS...Scattered to numerous afternoon and evening
thunderstorms will prevail into early next week. The greatest
daily thunderstorm coverage should occur east to south of Tucson
with reduced thunderstorm activity across the western deserts. A
less favorable pattern may temporarily bring reduced thunderstorm
coverage around the middle of next week.
&&
.DISCUSSION...
Scattered showers and storms continue to fire in the higher terrain
locations east of Tucson. After quite an early start to the
convection, things have tempered a bit in terms of intensity. This
is temporary however as much of the lower cloud cover across the
area has eroded and new (more vigorous convection) is forming across
the Chiricahua Mtns as well as along the Mogollon Rim. Tucson has
been right on the edge of storms so far and whether that trend
continues through the rest of the afternoon is the big challenge of
the day. Most runs of the HRRR and latest UA WRFs suggest convection
will continue to move into the area from the north. Even though most
of the organized storms will be along the AZ/NM border where a
remnant circulation can still be seen on satellite and where mid
level lapse rates are steeper, nearly all hi-res models depict
enough areal coverage that I feel comfortable hanging onto a decent
mention of PoPs around town through mid evening. Boundary collisions
and even the slightest bit of ascent have been all we`ve needed the
past few days and not much has changed thermodynamically across the
area today. Given the fact that we`re already seeing isolated storms
propagating off the Catalina Mtns, I think higher than normal PoPs
are still more than warranted in this case. CAPE is much more
marginal as one heads west and I think most locations across western
Pima Co will be dry.
Similar moisture and stability indices are forecast across the
region on Saturday with a bit more of an easterly component to the
flow. Storms will likely form by late morning east of Tucson and
attempt to descend into the deserts. They`ll be fighting a bit of a
battle as additional dry air (not to mention warmer air aloft) will
have moved into the western half of the state by then and how far
storms make it before they dissipate is up for debate among the more
reliable operational models. Looks like another decent shot at rain
in Tucson, with much lower chances to the west. Confidence starts to
go downhill on Sunday as the day starts off looking like a typical
late morning through early evening convective event, but the past
few deterministic GFS/NAM/ECMWF all indicate a weak inverted trough
will move through the area late Sunday night into Monday morning.
Could end up being another double shot of storms like we had a few
days ago (last Saturday) with precip lingering into early Monday
morning. I ended up raising PoPs a bit during this time period but
confidence is always low this time of year given so many variables
at play.
Big picture-wise, it looks like daily storm chances will be the rule
through much of next week. There is some suggestion in the guidance
that low/mid level steering flow will take on a bit of a
southwesterly component by the middle/end of the week which will
usher in enough dry air to put the brakes on storms from Tucson
westward. I agree with the idea of a slight reduction in storm
chances, especially from Tucson to Ajo, although there will still be
strong/moist flow across much of Sonora and I don`t see much in the
way of a large scale pattern change that would prevent that from
advecting into AZ. PoPs gradually return to a climo-like appearance
by the end of the week but that`s certainly subject to change
depending on how much convection forms over Sonora next week.
&&
.AVIATION...Valid thru 23/00Z.
VFR conditions with cloud decks generally 5k-10k ft AGL with BKN
layers above, and surface wind variable in direction mainly less
than 12 kts. SCT TSRA developing after 21/18Z and lingering through
22/06Z. Winds vicinity TSRA could gust 40+ kts. Aviation discussion
not updated for TAF amendments.
&&
.FIRE WEATHER...Scattered to numerous mainly afternoon and evening
thunderstorms will continue into early next week with locally heavy
rain and strong winds. Temperatures will remain below normal with a
continuation of elevated humidity levels through Tuesday. Wednesday
onward conditions will become a bit drier and warmer with somewhat
less convection. From 20-foot winds will mainly remain below 15 mph
with the exception of strong outflow winds in the vicinity of
thunderstorms.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...None.
&&
$$
Leins/Cerniglia
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