Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/22/17
Area Forecast Discussion
National Weather Service Wakefield VA
956 PM EDT Mon Aug 21 2017
.SYNOPSIS...
High pressure becomes centered off the Mid Atlantic coast
through Tuesday. A cold front crosses the area late Wednesday,
with strong high pressure building north of the area from
Thursday into the upcoming weekend.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
Update...Showers and storms from earlier this evening have all
but dissipated with the loss of daytime heating and instability.
Have trimmed POPs back accordingly and made minor adjustments to
dewpoints that are running a degree or two warmer. Otherwise,
forecast is on track for stratus and potential fog development
overnight.
Previous discussion (410 PM)...
Latest surface analysis centers ~1023mb high pressure just
offshore, resulting in light south to southeast flow over the
local area. A weak wave visible on water vapor and in the RAP
analysis is located over the Delmarva this afternoon. The wave
coupled with increasing moisture, afternoon destabilization, and
a lee/thermal trough over the northern Piedmont has helped fire
off scattered showers and thunderstorms generally north and
west of Richmond. Overall storm strength has been limited due to
westerly flow and modest lapse rates. However, cannot rule out
some gusty winds and brief heavy downpours. Showers and
thunderstorms push northeast through the afternoon and into the
evening hours as the wave pushes offshore. Coverage wanes
tonight with the loss of daytime heating/destabilization and
upper level support.
Warm and humid tonight with lows mainly 70-75 F tonight.
Fog/stratus possible again tonight over the Piedmont into
central Virginia, but not expected to be as dense as this
morning.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY/...
Increasing return flow on the back side of departing high
pressure and ahead of an approaching cold front will result in
warm and humid conditions Tuesday. Highs generally in the low to
mid 90`s, cooler along the coast. Dewpoints in the upper 60`s
to low 70`s will produce heat indices in the 100 to 103 degree
range. While the atmosphere will be quite moist with
precipitable waters around 1.75 inches, warm air aloft, weak
lapse rates, and a lack of appreciable forcing will limit the
convective potential Tuesday afternoon. Will retain silent PoPs.
Mild Tuesday night with lows in the mid 70`s. Clouds increase
across the north ahead of the approaching cold front.
Better forcing arrives along the front Wednesday as a lead wave
drops over the Mid-Atlantic. The cold front progged to slowly
push across the area Wednesday afternoon into Wednesday night.
PoP`s increase during the morning, becoming likely Wednesday
afternoon with the arrival of the better dynamics. The air mass
ahead of the front will become modestly unstable, with mixed-
layer CAPE values progged around 1000-2000 J/kg. Deep layer flow
also progged around 25-30 knots as mid level flow increases,
resulting in better organization and overall storm strength. Mid
level lapse rates also improve to around 6 to 6.5 C/km. SPC
maintains a marginal risk for severe weather, with damaging
winds and heavy rainfall the main threats. Highs generally in
the mid 80`s northwest to around 90 south.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Strong Sfc cold front drops south across the area Wednesday night
into Thursday morning. Modest ascent accompanies the front within
the RRQ of a ~110kt jet over New England, along with pw values to
around 2.0" (around +1 st dev). By Wed evening, have maintained
highest (70%/Likely) POP across srn VA/NE NC, with slight to low end
rain chances by Wed night NW of RIC, where drier air arrives first.
PoPs across SE portions gradually diminish to 20-40% by Thursday
aftn. Thunder will be maintained into Wednesday evening, with
showers thereafter as stable NE flow prevails in the wake of the
front. Drier air gradually filters in from the NW late Wednesday
night into Thursday with partial clearing across the nrn tier
counties.
Thereafter, the late week period will be characterized by the gradual
development of a longwave upper level trough over the eastern United
States for the late week period into next weekend. Meanwhile, broad
1024+ mb surface high pressure builds south over the interior
northeast from Great Lakes Thursday and Friday, eventually setting
up over New England and ridging down the east coast over the weekend
into early next week.
Resultant E-NE flow will result in markedly cooler and drier
conditions over the region, with early morning lows in the 50s
inland to mid 60s along the coast. Maintained a dry forecast through
the forecast period. High temperatures Thu-Mon will be at or just
slightly below normal through the period, mainly in the upper 70s to
low 80s.
&&
.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
Showers and storms from earlier this evening have all but
dissipated with the loss of daytime heating and instability.
Otherwise, forecast is on track for stratus development across
SE VA/NE NC and potential fog development overnight (initially
inland after 22/0600Z and then closer to the coast around
sunrise). Any fog/stratus that develops should dissipate/lift
after 22/1300Z. A cold front pushes into the Ohio Valley on
Tuesday with the region remaining dry with SCT cumulus
developing in the afternoon. The front approaches the region
Tuesday night and is expected to cross the area during
Wednesday. Flight restrictions will be possible Wednesday...
mainly in the afternoon and through Wednesday night due to
showers and thunderstorms. The front should exit the coast
Thursday morning with lingering showers possible across
far SE VA/NE NC. Conditions are anticipated to improve Thursday
afternoon into Friday as the front shifts farther southeast and
high pressure builds north of the region. Breezy NE winds are
also anticipated near the coast Thursday and Friday.
&&
.MARINE...
Latest surface analysis has a high pressure centered just off the
coast. The high will continue to move out to sea overnight and
Tuesday. A cold front approaches the waters Tuesday night and into
Wednesday morning. The front crosses the area late Wednesday and
moves SE of the area Thursday with high pressure returning for the
remainder of the forecast period. Obs indicate generally S/SE winds
of 10 to 15 knots over the waters with waves of 1 to 2 feet and seas
around 2 feet. Winds increase out of the SSW Tuesday through Tuesday
night as the front approaches the waters. Wind speeds may approach
15 to 20 over the Chesapeake Bay and ocean with seas building to 3
to 4 feet and potentially 5 feet north/20nm out, and waves building
to 2 to 3 feet. A Small Craft Advisory may be needed for the
Chesapeake Bay and northern two ocean zones Tuesday night into early
Wednesday. Winds shift to the N/NE behind the front late Wednesday
through Thursday around 10 to 15 knots.
Strong surface cold front drops across the waters Wed afternoon and
evening...pushing well SE of the area during Thu. Winds shift to the
N/NE behind the front late Wed through Thu around 10 to 15 kt.
Post-frontal, look for onshore (E-NE flow) for the remainder of the
forecast period as high pressure builds NNW of the local area. Winds
increase to 15-20 kt Thu night as a couple of waves move across the
stalled front to the south across the Carolinas. Seas will remain
choppy for the late week period into the weekend with the persistent
onshore flow, remaining 3-4 ft northern waters...4-5ft southern
waters.
&&
.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...None.
NC...None.
VA...None.
MARINE...None.
&&
$$
SYNOPSIS...LKB
NEAR TERM...BMD/LKB/SAM
SHORT TERM...LKB/SAM
LONG TERM...AJZ/MAM
AVIATION...BMD
MARINE...SAM
Area Forecast Discussion
National Weather Service Albany NY
1042 PM EDT Mon Aug 21 2017
.SYNOPSIS...
Warm and humid conditions will prevail tonight as high pressure
continues to move east of the Mid Atlantic Region. It will be hot
and muggy tomorrow with highs 10 to 15 degrees above normal.
Showers, along with the potential for strong to severe thunderstorms
are expected during the afternoon and evening hours ahead of a
strong cold front. Cooler and less humid air will move into the
region for Wednesday, with dry and cool conditions expected for the
rest of the week.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
As of 1042 PM EDT...The isolated showers and thunderstorms over
central NY just west of the eastern Catskills weakened and
dissipated shortly after sunset with the loss of the diurnal
heating. The slight chc pops for isolated showers/thunderstorms
were removed south and west of Albany. Some leftover cirrus and
mid level clouds drifted through the region based on the latest
IR imagery. The latest 3-KM HRRR supports a dry overnight
period.
The rest of the night time should be warm and humid with the
boundary layer winds increasing out of the south with the sfc
high drifting off the Mid Atlantic Coast. The sfc winds will be
decoupling in many locations with some patchy and locally dense
radiative mist or fog forming in the major river valleys. Some
low stratus may form and drift up the Hudson River Valley well
after midnight especially based on the NAM BUFKIT profiles. We
have kept the cloud cover partly cloudy to account for this.
Lows tonight will be mainly in the mid to upper 60s with a few
70F readings in the mid-Hudson River Valley. Some slightly
cooler readings are likely in the lower 60s over the southern
Adirondacks and southern VT.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY/...
A strong upper level trough will be digging from south-central
Canada across the Great Lakes, bringing a surface cold front
through the Ohio Valley into New England. Ahead of this
boundary, a surface pre-frontal trough will help kick off some
showers and thunderstorms during the early afternoon hours.
These showers/storms will track eastward across our area by
later in the afternoon and through the evening hours.
Strong south-southwesterly flow will allow for another
unseasonably warm and humid day, with highs well into the 80s
and dewpoints approaching 70 degrees. Some locations might even
hit the 90 degree mark. It looks like quite a breezy day as
well as the latest GEFS indicates that the 850 mb u-component of
the wind is 2-4 standard deviations above normal. GEFS also
shows PWATS 2-3 standard deviations above normal. These warm
temperatures along with a moist environment and strong southerly
winds should allow for at least a moderate amount of
instability tomorrow afternoon/evening. The NAM12 is more
bullish with CAPE in excess of 2K but also shows dewpoints in
the lower 70s. The GFS still shows moderate CAPE around 1-1.5K
across our western zones with even higher instability west of
the forecast area. Even though there is still model
disagreement on the amount of instability, there still looks
like there will be plenty for storms to tap into. Additionally,
with strong upper level dynamics approaching, 0-6 km bulk shear
will be reaching around 40 kts, so the ingredients are coming
together for some stronger storms tomorrow afternoon/evening.
One mitigating factor will be that mid-level lapse rates will be
fairly weak (generally 6 deg/km or less), but the combo of
instability/shear should allow for some storm organization. The
main threat will be gusty winds, but with PWATs reaching around
two inches, will also have to watch for some locally heavy
downpours and isolated flash flooding as well.
The storms may linger into the first part of tomorrow night,
but should be ending from west to east as the front crosses the
area, as lows fall into the 60s.
On Wednesday, dewpoints will be falling during the day, as much
cooler and drier air moves into the area. Highs will generally
be in the 70s with a partly sunny sky. There still may be a
lingering shower due to the passing upper level trough, but most
areas should be dry. Skies should continue to clear out by
Wednesday night, as lows fall into the upper 40s to upper 50s,
as high pressure builds into the area.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
The extended forecast continues to feature a mean longwave trough
over the region with high pressure building in at the sfc with
mainly fair and dry weather with temps slightly below normal for late
August.
Wed night into Thu...A broad upper level trough will be over
southeastern Canada, the Great Lakes Region, and the Northeast. The
latest GEFS has H500 heights 1 to 2 standard deviations below
normal. Initially, some lake enhanced isolated showers tapping Lake
Ontario moisture will impact the western Adirondacks Wed night.
Variable cloudiness and cool temps are expected with H850 temps
falling back to +6C to +10C from northwest to southeast across the
forecast area. Lows will be in the mid 40s to around 50F over the
mountains, and lower to mid 50s in the valleys. A short-wave
associated with the upper level low and a sfc trough will focus some
isolated to scattered showers especially west of the Hudson River
Valley, and over the higher terrain. It will be cool and breezy with
highs in the lower to mid 70s over many of the valley locations with
a few upper 70s in the mid-Hudson Valley and NW CT, and 60s to
around 70F over the hills and mountains.
Thu night through into Sat night... A large dome of Canadian high
pressure builds in from Ontario and the western Great Lakes Region
Thu night into Fri. The strong subsidence associated with the broad
sfc anticyclone will yield fair and dry weather to close the week
and enter the weekend. The sfc high shifts eastward over s-cntrl
Quebec and the Northeast by Saturday night. Slightly cooler than
normal temps and comfortable humidity levels are expected. The 12Z
GEFS H850 temps are 1 to 2 standard deviations below normal. Lows
will generally be in the mid 40s to lower 50s. Highs Friday and
Saturday will be mainly in the lower to mid 70s in the valley areas,
and lower to upper 60s over the higher terrain.
Sunday into Monday...The 12Z GFS and ECMWF both show some short-wave
energy swinging around the H500 upper low over the Northeast and
southeast Canada on Sunday. A few instability showers could pop up
over the southern Greens and the southern Adirondacks. The low-
level moisture profiles are not impressive. We placed a slight
chance of showers in for those locations, otherwise high pressure
builds back in from the Great Lakes Region Sunday night into Monday,
and low and mid level heights begin to rise. Temps continue to be
slightly below normal by a few degrees late in the weekend into
early next week. Humidity levels continue to be comfortable with sfc
dewpts in the 40s to 50s.
&&
.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
High pressure continues to move east of the Mid Atlantic Region
tonight. A cold front will slowly approach from the eastern
Great Lakes Region tomorrow with a prefrontal trough focusing
showers and thunderstorms late in the afternoon into the early
evening.
VFR conditions early this evening with sct-bkn cirrus around
due to some dissipating convection over central NY. Some mid
level clouds may also move into KPOU. A southerly flow will
continue in the boundary layer tonight advecting in higher
dewpoint air, and with the skies mostly clear and the sfc winds
decoupling we are expecting some mist and fog to develop
especially at KGFL and KPSF. We have forecasted LIFR/IFR
conditions at these sites. Our confidence was not as great at
KPOU and KALB, as some stratus may develop and move up the
Hudson River Valley tomorrow morning. We have placed some MVFR
stratus at KPOU at 1.5 KFT AGL, and kept it scattered at KALB
but with vsbys at 3SM for both sites.
The mist/fog or low stratus should gradually burn off between
12Z-14Z. At KPSF, the stratus may linger at the MVFR levels the
longest in terms of cigs. The southerly winds will increase at
the sfc and the prefrontal trough thunderstorms are possible in
the afternoon. We have used a PROB30 group for the possibility
of thunderstorms as early as 18Z at KGFL, 19Z at KALB/KPSF, and
20Z at KPOU. The convection may linger into the evening at some
of these sites. Later TAF issuances will narrow in on the time
period. Expect MVFR or brief lapses to IFR/LIFR conditions with
any thunderstorms.
The winds will be south at around 5 kts at KALB tonight, but
will become light and variable at 4 kts or less or calm at
KPOU/KPSF/KGFL. The winds will increase from the south at 5-9
kts in the late morning, and be 9-15 kts during the afternoon
with some gusts in the 20-25 kts range especially at
KALB/KPSF/KGFL.
Outlook...
Tuesday Night: High Operational Impact. Likely SHRA...TSRA.
Wednesday: No Operational Impact. NO SIG WX.
Wednesday Night: No Operational Impact. NO SIG WX.
Thursday: No Operational Impact. NO SIG WX.
Thursday Night: No Operational Impact. NO SIG WX.
Friday: No Operational Impact. NO SIG WX.
Friday Night: No Operational Impact. NO SIG WX.
Saturday: No Operational Impact. NO SIG WX.
&&
.FIRE WEATHER...
Most areas will see showers or thunderstorms tomorrow afternoon
and evening thanks to a cold front and strong upper level trough
passing through the area. Min RH on Tuesday will only be 50 to
65 percent with south winds at 10 to 20 mph. RH values will
recover to near 100 percent tonight and tomorrow night with some
patchy fog possible tonight.
&&
.HYDROLOGY...
Dry weather is expected through tomorrow morning across the
region. An approaching cold front will allow for showers and
thunderstorms tomorrow, mainly during the afternoon and evening
hours. Any thunderstorm will be capable of producing locally
heavy downpours and could lead to isolated flash flooding.
The locally heavy rainfall may result in minor flooding of
urban, poor drainage and low lying areas. Behind this frontal
system, mainly dry weather is expected for the rest of the week.
Basin average rainfall on Tuesday will generally be around a
half of an inch to an inch, although point totals may be
higher. This rainfall will only allow for minor rises on rivers
and streams. River and stream levels should quickly recede by
Wednesday and then remain steady for the rest of the week.
For details on specific area rivers and lakes, including
observed and forecast river stages and lake elevations, please
visit the Advanced Hydrologic Prediction Service /AHPS/ graphs
on our website.
&&
.EQUIPMENT...
The KENX radar will likely be down through at least Friday,
September 1st for the bull gear replacement. We are waiting for
a ROC maintenance team and parts to arrive to assist local
technicians with the repairs.
&&
.ALY WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
MA...None.
VT...None.
&&
$$
SYNOPSIS...JVM/Wasula
NEAR TERM...Wasula
SHORT TERM...SND/Frugis/JVM
LONG TERM...Wasula
AVIATION...Wasula
FIRE WEATHER...Frugis/JVM
HYDROLOGY...Frugis/JVM
EQUIPMENT...WFO ALY
Area Forecast Discussion
National Weather Service Gaylord MI
1150 PM EDT Mon Aug 21 2017
.UPDATE...
Issued at 939 PM EDT Mon Aug 21 2017
Upstream cold front remains west of Michigan late this evening...
extending from near the arrowhead of Minnesota thru western Iowa
into Kansas. Plenty of warm/moist air streaming northward ahead of
this front continues to interact with a large axis of instability
to generate several areas of convection across the Western Great
Lakes and the Upper Mississippi Valley. Area of convection
quickly developed over the past hour or two across portions of
Northern Lower Michigan...featuring some thunder and heavy
rainfall. Marginal severe threat appears to be largely finished
with loss of instability in agreement with latest SPC Day 1
Outlook which now puts all of Michigan in only general thunder for
the remainder of the night. Latest short term models show this
initial wave of convection lifting off to our NE over the next
couple of hours... with a more widespread wave of precip
developing later tonight just head of the approaching cold front.
&&
.NEAR TERM...(Tonight through Tuesday)
Issued at 330 PM EDT Mon Aug 21 2017
Ill-defined and stalling cold front is draped across the Straits
region. This front connects with low pressure in Nebraska, which
will intensify as it lifts ne along the front. Intensification
will be most rapid over and downstream of northern MI, overnight
into Tuesday. This coincides with falling heights aloft, and the
eventual arrival of an upper trof Tuesday.
Diurnal heating was interrupted this afternoon by the eclipse
(temps fell by a few degrees in many locales), but has resumed.
Steamiest surface parcels are found from PLN to APN (with APN
81/69f), leading to MlCape values near 1500j/kg along that axis.
Earlier cu field here faded with the eclipse, but some mid-clouds
are approaching which indicate some weak mid-level forcing and
erosion of any capping. HRRR runs are becoming inconsistent as to
whether something can pop in ne lower MI this afternoon/early
evening. If it does, earlier discussions about favorable
shear/instability for supercells and svr wx remain valid. We are
seeing some cells cook off sw of CAD, which is not handled well by
the CAMs. There is certainly a nose of better instability (MlCape
just above 1k j/kg) poking into that region, but there is much
less in the way of shear down that way.
More widespread convective activity is still expected to break out
tonight, with the arrival of stronger forcing (to counter
decreasing instability). Last several runs of the HRRR show this
occurring in the 8-9pm range in nw lower MI, which would probably
be soon enough to support a strong/svr threat before instability
wanes too much. Will maintain an evening mention of strong/svr
storms in northern lower MI.
Very juicy airmass (PWATs around 1.75in) will support locally
heavy rainfall. This will become a bigger player overnight, as
forcing and precip coverage increases. 0.50-1.0 inch amounts
should be common, and locally higher amounts are anticipated.
Numerous to widespread pops in order for the overnight.
Showers will end from nw to se on Tuesday, as the low departs and
associated cold front swings thru. By mid-afternoon, only hanging
onto a slight chance of a shower for OSC/Tawas. We will be on the
breezy side from about late morning onward. Decreasing cloud
cover, though with enough diurnal heating and cool air aloft to
support a cu field (especially away from Lakes MI/Superior).
Min temps tonight quite mild, ranging thru the 60s. Max temps
Tuesday mainly in the 70s, some upper 60s near Superior.
&&
.SHORT TERM...(Tuesday night through Thursday)
Issued at 330 PM EDT Mon Aug 21 2017
...Much cooler weather for midweek...
High Impact Weather Potential: Nothing.
Longwave pattern becomes more amplified for the midweek period as
deep fall-like trough digs into the Great Lakes and Northern CONUS.
Embedded shortwave energy rotating through the trough may bring some
light scattered precipitation to eastern areas Wednesday, otherwise
quiet weather.
Deep layer drying Tuesday night behind the front as much cooler air
sweeps into northern Michigan. Early Wednesday, a well-defined
shortwave pinwheels around the stacked low now over Quebec, pushing
a secondary cold front and associated band of deeper moisture across
northern Michigan. A few scattered/light showers could result,
mainly over eastern Upper. Otherwise, even cooler temperatures will
headline the midweek portion of the forecast with high temps ranging
from the low-mid 60s north to the upper 60s to 70 degrees
elsewhere...some 10 or so degrees below normal for the third week of
August.
Additional shortwave energy may pinwheel through the eastern lakes
on Thursday, possibly brushing Lake Huron areas with an isolated
shower. Otherwise, large Canadian high pressure will slowly slide
southeast into the area resulting in lots of sunshine but still cool
temperatures.
.LONG TERM...(Thursday night through Monday)
Issued at 330 PM EDT Mon Aug 21 2017
High pressure will be over the Great Lakes region through Saturday
along with dry air, mostly clear skies, and rain free weather
through Saturday night. Sunday will see increased cloudiness and
rain chances throughout the day as an upper level area of low
pressure and surface reflection develops over the southern Great
Lakes with accompanying moisture. Rain chances will stick around
Monday as well as said area of low pressure remains over the
forecast area. Temperatures will only be around 70 Friday and warm a
bit the remainder of the period...in the low to mid 70s. Friday
morning has an opportunity to see some frost, with clear skies and
light winds...some mid to upper 30s are not out of the question for
our colder locales. The rest of the forecast period will see lows in
the mid 40s Saturday morning and warming to the mid 50s by Monday
morning.
&&
.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1150 PM EDT Mon Aug 21 2017
Showers and thunderstorms will redevelop across Northern Michigan
overnight ahead of an approaching cold front. Conditions will
deteriorate to MVFR/IFR...especially within heavier showers and
thunderstorms. Convection will continue into Tuesday morning
before cold FROPA brings precip chances to a close Tuesday
afternoon. SW winds under 10 kts will shifting to the W/NW on
Tuesday and strengthening to 15 to 25 kts in the wake of the cold
front.
&&
.MARINE...
Issued at 330 PM EDT Mon Aug 21 2017
Light sw winds will persist for much of tonight, ahead of low
pressure that will intensify as it crosses northern MI late
tonight. Winds will veer nw behind the low, becoming quite gusty
Tuesday into Wednesday. Small craft advisories will be hoisted
for many waters shortly.
&&
.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...SMALL CRAFT ADVISORY from 6 AM Tuesday to 6 PM EDT Wednesday for
LHZ345>349.
LM...SMALL CRAFT ADVISORY from 6 AM Tuesday to 6 PM EDT Wednesday for
LMZ323-341-342-344>346.
LS...SMALL CRAFT ADVISORY from 6 AM Tuesday to 6 PM EDT Wednesday for
LSZ321-322.
&&
$$
UPDATE...MR
NEAR TERM...JZ
SHORT TERM...JK
LONG TERM...TL
AVIATION...MR
MARINE...JZ
Area Forecast Discussion
National Weather Service Caribou ME
1156 PM EDT Mon Aug 21 2017
.SYNOPSIS...
High pressure will build south of the area this evening. Low
pressure will approach from the west on Tuesday. The low will
track to our north Tuesday night into Wednesday as it brings a
cold front across the area.
&&
.NEAR TERM /THROUGH TUESDAY/...
1155 PM Update...Made minor adjustments to placement of
isolated thunderstorm chances across the north next few hours
based on current radar imagery and lightning data. Activity
seems to be lining up along weak frontal boundary across far
northern Maine. Latest HRRR shows the activity diminishing the
next few hours. Otherwise, expect a very warm and muggy night,
as lows not expected to fall much lower than the mid 60s across
much of the region. Patchy fog still possible overnight in
spots.
Previous Discussion...
Humid airmass rmns ovrngt with dwpts rebounding into the lwr
60s and this wl lkly lead to patchy fog acrs the north as clds
dissipate.
Late tonight and Tue mrng wl be quiet, other than patchy fog as
brief ridging takes hold thru about 15z tomorrow. Wmfnt lifts
thru tomorrow aftn with showers and thunder dvlpng acrs the nw
aft about 18z. CAPES increase aft this time and 0-6km bulk shear
increase to 30-40kts in the aftn bfr increasing substantially
drg the evng hrs. PW values begin to rise in the aftn to nr 1.50
inches acrs srn areas, thus hv retained mention of hvy rain and
gusty winds to where convection is lkly.
&&
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
For Tuesday night, a strong cold front will cross the area later
in the night. This front has the potential to produce locally
heavy rainfall and will maintain that threat in the forecast. PW
values will approach 2 inches with a deep warm cloud layer
around 13K ft. A strong LLJ will be in place and Corfidi vectors
show the possibility of some back-building cells. The LLJ also
heightens the threat of gusty winds mixing down with
thunderstorms and will maintain mention of that in Tuesday
night`s forecast. It`s still unclear how much of the action will
be with a pre-frontal trough or with the front itself later in
the night. Otherwise, it will be a warm and humid night ahead of
the front with lows in the mid to upper 60s for much of the
area. Humidity will be high with dew points also in the mid to
upper 60s. Fog is likely along the coast and in high terrain.
Elsewhere, marine layer moisture will be streaming northward in
the form of stratus and some patchy fog. On Wednesday, clouds
with the front will exit the Down East region with a few
residual showers...but no thunderstorms can reasonably be
expected. Fog and low clouds will linger along the coast during
the morning. It will be a rather breezy day with a deep mixing
layer and still warm with highs in the mid to upper 70s. The
cooler air behind the front arrives gradually during the day and
it will be cooler and less humid Wednesday night with lows
mostly in the low to mid 50s. The cool Canadian air mass will be
fully in place for Thursday with highs in the low to mid 70s and
dew points in the upper 40s to lower 50s. Some cu fields will be
possible north of Houlton with the NW flow.
&&
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
In the longer term starting Thursday night, a quiet and cool
pattern appears likely with persistent upper level troughing and
surface high pressure. The primary challenges will be
identifying cumulus and stratocu fields in the a north to
northwest flow...and when minor shortwaves may kick off some
light afternoon showers Friday, Saturday and Sunday. In general,
little precipitation is expected and will hold off on specifying
chance pops for these days.
&&
.AVIATION /04Z TUESDAY THROUGH SATURDAY/...
NEAR TERM: VFR next 24 hours with potential MVFR vsbys btwn 07z
and 12z for northern terminals.
SHORT TERM: IFR conditions due to cigs, fog and thunderstorms
will affect all terminals Tuesday night. The low clouds will
linger into Wednesday morning for BHB and coastal sites, but all
of the area will be VFR by Wednesday afternoon and remain so
into Saturday.
&&
.MARINE...
NEAR TERM: Winds and seas will remain below SCA levels thru Tue
aftn bfr beginning to climb to near 5ft at the very end of the
period.
SHORT TERM: There is a credible threat of SCA conditions Tuesday
night into Wednesday in spite of the stable conditions and fog
that will be in place. Wind-driven waves could hit up to 6
feet. After Wednesday, no significant weather is forecast
through the end of the period.
&&
.CAR WATCHES/WARNINGS/ADVISORIES...
ME...None.
MARINE...None.
&&
$$
Near Term...Duda
Short Term...
Long Term...
Aviation...Duda/
Marine...Duda/
Area Forecast Discussion
National Weather Service Cheyenne WY
451 PM MDT Mon Aug 21 2017
.SHORT TERM...(This evening through Wednesday night)
Issued at 230 PM MDT Mon Aug 21 2017
West-northwest flow aloft prevails this afternoon under the
influence of a broad mid-upper level northern CONUS trough. A
shortwave was pushing southeast across WY and western Dakotas.
A surface front extended from northeast NE into extreme northern
CO. A slightly drier and more stable air mass should preclude
convective development this afternoon, except for scattered CU
over the mountains. Temperatures dropped between 7 and 12 degrees
during the solar eclipse. Lowered high temperatures a couple of
degrees. It was breezy, especially over the plains with northerly
winds gusting from 20 to 25 mph.
The short range models and ensembles are in good agreement progging
eastward progression of the northern CONUS trough and arrival of
a mid/upper level ridge Wednesday. Generally dry conditions will
prevail through the next 24 to 36 hours with precipitable water
values between 0.50" and 0.75". The exception will be the
southeast WY mountains Tuesday afternoon/early evening where
isolated convection may erupt due to favorable orographic lift.
High temperatures Tuesday will be near seasonal normals with mid
70s to mid 80s. Breezy south-southeast winds will develop across
the plains Tuesday afternoon.
The flow aloft becomes more west-southwest Wednesday, which will
advect some monsoonal moisture north-northeast into WY and CO.
Isolated convection develops by midday over the southeast WY
mountains, increasing in coverage as far east as the I-25 and
I-80 corridor into the evening. 700mb temperatures rise to 12-14
degrees Celsius Wednesday afternoon, yielding highs in the 80s to
around 90 degrees for lower elevations.
.LONG TERM...(Thursday through Monday)
Issued at 230 PM MDT Mon Aug 21 2017
More like August weather for the long term as upper ridge overhead
and we get impacted by shortwaves moving through the flow along
the northern periphery of the ridge. What this does for us here is
southeast Wyoming and Nebraska Panhandle this time of year is
create gusty west to southwest winds and dry conditions possibly
leading to fire weather concerns.
Starting off Thursday, this looks to be the case as the ECMWF
shows a shortwave over southwest Montana move northeastward
through the ridge. Southwest winds across Carbon County with
15-20kts mixing down to the surface. Some differences in the EC
and GFS on precip coverage. EC much more bullish on PoPs over the
GFS. Will go with the EC solution right now with fairly widespread
slight chance PoPs across the CWFA.
Secondary low pressure system tracks across northern Montana
Friday on the ECMWF with 700mb winds increasing to 20-25kts. Could
be a fire weather day Friday with afternoon humidities falling
into the upper teens/low 20s. We will need to keep an eye on this
as the event draws closer.
Montana shortwave then drops southeast over the weekend into the
Dakotas. When this happens, we see a backdoor cold front moving
into the area from the northeast. ECMWF 850mb winds shift to the
northeast over the Panhandle Saturday, eventually shifting to the
southeast as the ridge begins to build back into the west. Weather
looks dry over the weekend with precip well east and south of the
CWFA.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 449 PM MDT Mon Aug 21 2017
Mainly VFR tonight with the exception of down here near KCYS.
Latest HRRR guidance suggesting some LIFR conditions in fog/low
stratus towards sunrise Tuesday. Did start to trend the KCYS TAF
down towards what the HRRR guidance is suggesting. We will
continue looking at trends this evening and provide a more
definitive forecast for KCYS on the 06Z TAFs.
&&
.FIRE WEATHER...
Issued at 230 PM MDT Mon Aug 21 2017
A cool front will push south of the districts this afternoon.
Afternoon humidities will fall to around 15 percent across lower
elevations of Carbon County, however winds will be light. Across
the plains, minimum humidities will range from 25 to 40 percent
with breezy northerly winds through early evening. Dry and warm
conditions are forecast Tuesday with lowest humidities across
lower elevations of Carbon County. It will be breezy east of the
Laramie Range Tuesday afternoon with south-southeast winds gusting
to around 20 mph. Moisture will increase Wednesday as monsoonal
flow from the southwest returns to the districts, and persists
through the end of the week. Higher humidities and better chances
of showers and thunderstorms can be expected at that time.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
SHORT TERM...MAJ
LONG TERM...GCC
AVIATION...GCC
FIRE WEATHER...MAJ
Area Forecast Discussion
National Weather Service Dodge City KS
659 PM CDT Mon Aug 21 2017
...Updated for aviation discussion...
.SHORT TERM...(This evening through Tuesday)
Issued at 250 PM CDT Mon Aug 21 2017
Regional 88-D radar showed and area of showers continuing to spread
northeast across the Texas panhandle into the Meade and Comanche
county areas. This trend is expected to continue through the
afternoon. Although the reflectivity appears rather light, there
should be potential for light to brief moderate rain rates under
this southwest to northeast oriented max in precipitable water
(around 1.8"). Between the precipitation and cloudiness persisting
over the south central Kansas counties, and the eclipse which
accounted for a 2 to 3 degree temperature drop this afternoon,
keeping a decent temperature trend as been difficult. However there
is a dry slot on satellite expanding slowly northeast across extreme
se Colorado. This subsident zone should ensure a dry rest of the
daytime hours in the west, while scattered showers expand north
east through south cental Kansas.
Another chance for scattered showers and isolated thunderstorms will
follow this evening as the 850mb front drops south into Kansas. The
overall coverage will probably be limited by the loss of maximum
moisture and theta-e transport by that time. However the Hi-Res
ARW/NMM and HRRR continue to hold on to the potential toward late
evening and beyond.
Any areas of fog that develop over south central Kansas overnight
likely will not last as the increasing northerly surface winds
increase mixing, and the model fields generally do not favor at this
time. Widespread low level cloudiness will rapidly advance across
most of the area with breezy northeast winds during the morning
hours, and clearing across the north in the afternoon. A dry push of
boundary layer air characterized by dewpoints in the 50s and upper
40s Tuesday night will will advance into the lower plains, creating
a zone of baroclinicity immediately south of our area.
.LONG TERM...(Tuesday night through Monday)
Issued at 250 PM CDT Mon Aug 21 2017
By midweek, the GFS displays another weak northwest flow pattern,
where any little weak midlevel impulse could bring showers or storms
daily, especially after peak heating. the same general idea is
supported in the ECMWF fields. The model consensus maintains a
somewhat seasonal temperatures spread, with highs just a few degrees
below normal for late August, in the mid 80s, and lows generally in
the low 60s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 657 PM CDT Mon Aug 21 2017
A cold front will pass across the TAF sites after 09z.
Thunderstorms with gusty winds are possible ahead of the front.
In the wake of the front, winds will shift to the northeast at
15 kts. There will likely be low cloud development behind the
front with low MVFR and possibly IFR CIGs for a few hours
before daytime heating burns it off.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 68 84 58 85 / 30 10 10 0
GCK 66 85 58 84 / 20 10 0 0
EHA 66 80 61 83 / 30 20 20 10
LBL 68 83 61 85 / 20 30 10 10
HYS 67 84 57 85 / 30 0 0 0
P28 71 87 61 85 / 30 20 10 0
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Russell
LONG TERM...Russell
AVIATION...Finch
Area Forecast Discussion
National Weather Service Hastings NE
814 PM CDT Mon Aug 21 2017
.MESOSCALE DISCUSSION...
Issued at 814 PM CDT Mon Aug 21 2017
CU towers and tstms are trying to form from just N of LXN to
Greeley. The 00Z LBF sounding shows why tstms are struggling.
There is a strong cap at the base of the EML with +14C near 700
mb. It is unlikely that the modest lift from the approaching trof
will be able to erase all of the CIN.
The 22Z HRRRX suggests we won`t see much tonight. POPs were
lowered quite a bit with an update associated with the 00Z TAFs.
No additional changes planned.
&&
.MESOSCALE DISCUSSION...
Issued at 528 PM CDT Mon Aug 21 2017
We cont to monitor potential for initiation of tstms. The cool
front currently extends from just N of LXN to just S of OLU (just
N of I-80). The RAP/NMM/WRF-ARW/RGEM are too aggressive... already
indicating tstms should have developed. So that leaves the NAM/GFS
which are later suggesting initiation between 00Z-03Z just W-NW-N
of the CWA. If this occurs...they should move into areas N and W
of the Tri-Cities before 03Z.
If initiation occurs...these storms will be in the post-frontal
air mass where deep layer shear will be increasing from 25 up to
35 kts.
We will be warning on 50 dBZ cores that reach 35K ft and 60 dBZ
cores that reach 23K ft.
&&
.SHORT TERM...(This evening through Tuesday)
Issued at 242 PM CDT Mon Aug 21 2017
Much of the focus today has involved keeping an eye on the high
cloud deck and the eclipse, but will also need to talk about the
expected weather over the next 7 days.
17Z Discussion --- Current water vapor imagery and upper air
analysis shows an active northern stream continues over the
region although the better forcing looks to be a little north of
us. A subtle mid level should move through west to east later this
afternoon. While the flow is weaker across and to the south of
our CWA, there is vort max to our southwest that could affect the
southeast part of the CWA later today. One other thing of note on
satellite is the sub-tropical tap that starts south of the Baja
region and has been streaming NNE through KS and SE Neb. This is a
big contributing factor to the eclipse-hampering cirrus in our
area. At the surface at 10 am, low pressure was situated over west
central Neb with a warm front extending ENE. Fog/Stratus deck was
taking its time burning off north of the warm front, but ODX has
gone from a quarter mile to 10 miles between 14 & 15Z
Primary question will be the extent of any convection firing later
this afternoon and into tonight. The shortwave noted above should
help drag the surface front into and through the CWA, starting in
the northwest CWA between 22-00Z and exiting the southeast part
of the CWA by sunrise Tue. The best instability should occur a
little to the north of our CWA but ML CAPE will still be in the
1000-1500 j/kg range in the northern half of the CWA. Deep layer
shear not as impressive with 20 kt 0-6 km shear progged at 00Z.
Will continue to monitor real time radar and CAM models for
convective initiation. Earlier runs of the HRRR have shown this to
occur around 4 pm in our northwest. HRRR does show some
convection along the front across much of the CWA during the
evening and overnight, however the bulk of this remains in our far
northern CWA and into NE Neb closer to the better forcing.
1930Z Update... Storms have indeed initiated along an outflow
boundary across northeast Neb and are just to the north of our
CWA. Latest HRRR guidance now showing this activity will push
southward through the CWA the remainder of the afternoon and
overnight, exiting the southern CWA just before sunrise. Deep
layer shear still lacking but enough instability that a few
strong/severe storms cannot be ruled out.
Tuesday should be quiet in terms of the active weather as the
surface front pushes well south with high pressure dropping into
northeast Neb. Will be a bit cooler with highs in the lower 80s,
but even more noticeable will be the lower dewpoints which should
be in the mid 50s, about 15 degrees lower than what we are seeing
today.
.LONG TERM...(Tuesday night through Monday)
Issued at 242 PM CDT Mon Aug 21 2017
Quiet conditions continue Wed and Thu as mid level ridge builds
into the Rockies before that pattern reverts to something similar
to the last few days for the weekend as the next wave moves onto
the PAC NW coast and dampens the ridge. Superblend producing Pops
during the day Thursday but don`t see a lot of evidence for that.
Tstm chances do return by Thu night into the weekend with series
of wave passages. If models are correct, the ridge then builds
back into the Rockies again early next week, lowering our
precipitation chances. At least early next week, high temps remain
in the lower 80s as the ridge axis remains far enough west of
here to keep the hotter temps at bay.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Tuesday)
Issued at 648 PM CDT Mon Aug 21 2017
Significant Wx: Low probability of IFR TSRA tonight.
Tonight: Cold frontal passage 02Z-03Z. Predominantly VFR with
multi-layered CIGs at or above 10K ft. A few CU around 4K ft will
be possible thru the night with some developing into sct TSRAs.
Lgt S winds will shift to the N after frontal passage. Confidence:
Medium
Tue: VFR SKC or becoming SKC before 17Z. N winds 8-12 kts becoming
NE. Confidence: High
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...None.
KS...None.
&&
$$
MESOSCALE...Kelley
SHORT TERM...Ewald
LONG TERM...Ewald
AVIATION...Kelley
Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
732 PM CDT Mon Aug 21 2017
.SYNOPSIS...
Issued at 318 PM CDT Mon Aug 21 2017
Large MCS progressing across southeast SD into IA, northeast NE
and srn MN. Weak development noted across Holt, Boyd and Keya Paha
counties earlier. Elsewhere broad trough across southern Canada
into the northern Plains with PV anomaly just over the Canadian
border. PV axis rotating through Dakotas serving as large scale
support for convergence along associated from now stalled across
the middle of NE.
&&
.UPDATE...
Issued at 730 PM CDT Mon Aug 21 2017
A look at the KLBF 00z UA flight this evening indicates a strong
700mb cap which explains why no thunderstorms have formed. The
focus for storm development is moving south of I-80 at this time
but continues across Custer County. A new forecast is in place
using a 4-way blend of the HRRR models, the RAP and GFS models
for isolated storm coverage.
&&
.SHORT TERM...(This evening through Tuesday)
Issued at 318 PM CDT Mon Aug 21 2017
The aforementioned stalled frontal boundary showing increasing
convergence along it with several waves of outflow moving southward
as well. Mesoscale analysis continues to support strong deep moist
convergence in this vcnty so would expect thunderstorms to develop
along the boundary by 4 PM CDT and would expect some supercell
potential with decent shear (30-40 kts)from LBF northeastward. 0-6km
shear orientation would suggest some storm interactions in the LBF-
BBW area, but more of a linear fashion further north. Despite a
clearing of stratus across southwest NE earlier this morning low
level lapse rates were not overly impressive yet. Think this will
change in the next couple hours though and scattered TSRA
developing, though more isolated the further southwest you go in NE.
Very unstable aloft and hail parameters look good. Heavy rain also a
possibility as PW values around 1.6" on the sounding this morning
which is significant but no where near records. Appears as though
the corridor from LBF to BBW would be favored for TSRA development
with overall progression into Custer Co. which could cause issues
since they`ve had so much rain lately.
TSRA development should exit the area along with the front by
midnight or so and would therefore expect a drier and cooler airmass
in place tmrw.
.LONG TERM...(Tuesday night through Monday)
Issued at 318 PM CDT Mon Aug 21 2017
The main forecast challenge this forecast period will be
precipitation chances towards the end of the week.
High pressure builds across the western CONUS bringing a northwest
flow across the central US through mid week.
The ridge then flattens out towards the end of the week. A short
wave trough then moves across the area Thursday into Friday bringing
chances for showers and thunderstorms. At this time widespread
severe weather is not expected. That being said models show a good
flow of moisture into Nebraska Thursday into Friday which could lead
to the potential for decent rainfall amounts to end the week.
Saturday and beyond...precipitation chances look slim for the rest
of the period. Temperatures will remain seasonal with highs in the
80s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 638 PM CDT Mon Aug 21 2017
A look at the KLBF 00z UA flight this evening indicates a strong
700mb cap which explains why no thunderstorms have formed. The
focus for storm development is moving south of I-80 at this time.
Thus the potential for thunderstorms at KLBF appears unlikely.
There is potential for storm development east of KLBF but this
will also diminish in time this evening.
Otherwise MVFR cigs are underway near KONL and these cigs may
spread south along and east of a line from KLBF-KBBW this evening.
Some models don`t capture this and one them is the SREF which
maintains VFR. The forecast follows the SREF model for now.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...CDC
SYNOPSIS...Stoppkotte
SHORT TERM...Stoppkotte
LONG TERM...Gomez
AVIATION...CDC
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
832 PM CDT Mon Aug 21 2017
.UPDATE...
831 PM CDT
Little change to going forecast this evening, though severe
threat continues to appear minimal in the wake in the wake of
extensive morning MCS cold pool and cloud cover across eastern IA
and northern IL/IN. SPC has removed the northern 2/3 and northwest
IN from the marginal risk for the remainder of the overnight
hours.
Evening surface analysis depicts weak surface low pressure over
the Upper Mississippi Valley, along a cold front which stretches
from the northern Great Lakes to the Central Plains. Strong low-
level baroclinic zone was noted across Missouri and downstate IL
however, in association with strong outflow boundary from MCS
which decayed across the region earlier in the day. Despite warm
and humid warm sector air mass ahead of the cold front, RAP
mesoanalysis and 00Z soundings indicate relatively stable/capped
near-surface conditions, with weak low-level lapse rates north of
the outflow boundary. Remnants of strong linear MCS over IA
continues to weaken as it propagates east-southeast toward the
Mississippi.
While the threat of severe weather diminishes, especially across
northern parts of the cwa, shower and thunderstorm coverage should
continue to increase across the area through late evening as
forcing strengthens in association with a digging/amplifying upper
trough across the Upper Midwest. The resulting increase in
southwesterly low level jet, large scale height falls and the
increasingly favorable upper jet position is expected to allow
showers/storms to spread across the region overnight in advance of
the cold front. While some potential for isolated strong wind
gusts will persist across the southern tier or so of counties,
locally heavy rainfall looks to be the primary concern with
overnight storms. PW`s around 2 inches and southwesterly low level
jet parallel to the cold frontal zone may produce some
training/back-building in some spots which could produce isolated
rainfall amounts in excess of 1-1.50 inches. Thunderstorm
coverage should diminish from the north/northwest toward morning,
with the focus quickly shifting to the east/south of the forecast
area after sunrise.
Ratzer
&&
.SHORT TERM...
313 PM CDT
Through Tuesday...
Main concern is showers and thunderstorms this evening and
overnight and associated risk for primarily heavy downpours and
localized flooding. Current subsident regime behind earlier
short-wave has yielded dry conditions for the time being this
afternoon. Fairly quiet conditions should continue through about
sunset. Thereafter, in the evening into the overnight, trend
should be for increasing coverage of showers and storms tied to
additional short-wave energy arriving from the Plains. Main wave
is tied to well defined MCS over NW IA, with another arriving from
KS/MO area. A signal on high-res and WRF guidance for a subtle
disturbance and perhaps better lower-level convergence could
provide an earlier evening focus for convection breaking out in
mainly NW Indiana (possibly extending into parts of NE IL).
Later in the evening and into the overnight as activity expands in
from the west, strengthening low level jet could help sustain more
robust showers and storms, with PWAT of 2-2.25" supportive of very
heavy downpours and even localized flooding in stronger storms
depending on residence time/training. Overall storm motions do
appear to be quick enough to preclude a more significant flooding
risk. Severe risk appears to be unfavorably timed diurnally, with
an isolated gusty/damaging wind risk (wet microburst/precip
loading) and deep layer shear possibly supportive of a hail risk
(marginally severe on the high end).
A cold front will sweep across the area on Tuesday, with lingering
isolated-scattered storms possible in the morning (12z-15z) and
focus shifting to mainly southeast of I-55 in the early-mid
afternoon for any additional showers/isolated storms immediately
tied to frontal passage. Clouds will clear from the northwest
behind the front in dry air advection and CAA, with breezy west
to northwest winds. Highs will reach the upper 70s to lower 80s.
Castro
&&
.LONG TERM...
241 PM CDT
Tuesday night through Monday...
Transition to drier and much cooler weather occurs mid-week and
lingers through the end of the week before a gradual warm-up
brings temps back to near normal for late August.
Surface cold front clears the forecast area to the southeast by
Tuesday evening, with breezy northwest winds bringing a cooler and
less humid air mass into the region. This trend persists through
the end of the week, as a long-wave upper trough deepens across
the eastern CONUS, and keeps us in deep northwest flow. Surface
high pressure spreads across the region during the period, though
models have been fairly consistent in depicting a mid-level short
wave which digs across the Upper Midwest and Great Lakes region
late Wednesday night into early Thursday, with a reinforcing push
of cooler air and a surface cold front passage. Guidance continues
to indicate the potential for some spotty showers early Thursday
as 850 mb temps drop to about +6C over the warm late-August waters
of Lake Michigan. Otherwise, dry conditions are expected to
persist into the weekend as the surface high strengthens across
the western Lakes.
925 mb temps support daytime highs in the low-mid 70`s, with
overnight lows dropping into the low-mid 50`s. A few upper 40`s
are possible in our typical cool spots away from the immediate
Chicago metro area and warmer lake front areas.
The eastern CONUS upper trough eventually is progged to drift off
to the east this weekend, with the surface high pressure ridge
also moving off and allowing winds to become more southeasterly.
Medium range solutions of the ECMWF and GFS both indicate a short
wave trough propagating from the Northern Plains southeast into
the Midwest Saturday night into Sunday, though there are
differences with the evolution beyond that time. The EC develops a
deep closed upper low over the area which lingers into the
following Monday, while the GFS is much less amplified. In general
however, a gradual moderation in low-level temps and a modest
increase in low-level moisture is likely.
Ratzer
&&
.AVIATION...
For the 00Z TAFs...
641 pm...Main forecast concern is thunderstorm potential through
sunrise Tuesday morning.
Short term guidance has been in good agreement showing
thunderstorms developing early this evening over the terminals and
this appears to be starting now and slightly further east then
was expected with convection extending from southern Lake Michigan
and then more scattered into eastern IL. This activity is
expected to shift east over the next few hours with a lull
expected through mid/late evening. However...the airmass is moist
and unstable so its possible scattered showers or isolated
thunderstorms could develop at any time.
Focus then shifts to convection across IA and models differ as to
how far east this activity will move overnight as it appears the
strongest convection and more solid line may move south of the
terminals overnight. Confidence is too low to make any significant
changes with this forecast and maintained tempo thunder during the
same time period from the previous forecast. Trends will need to
be monitored later this evening and overnight. Once this activity
moves east/southeast of the terminals by sunrise Tuesday morning
only lingering/scattered showers are expected Tuesday morning.
Southwesterly winds 10-15 kts this evening will slowly turn more
westerly overnight and then shift northwest Tuesday morning as a
cold front moves across the area. Winds may turn more northerly
for a time Tuesday afternoon. Speeds in the 12-16kt range with
gusts into the 20kt range are expected Tuesday.
Any of the stronger storms will produce heavy rain and brief ifr/
mvfr cigs. Prevailing mvfr cigs are possible overnight and into
Tuesday morning. Maintained previous forecast for mvfr cigs but
confidence is low regarding how widespread and how long mvfr cigs
may persist. Cigs should lift and scatter Tuesday afternoon. cms
&&
.MARINE...
241 PM CDT
Main marine forecast concerns continue to be on a period of
northerly winds down the length of the lake Tuesday night into
Wednesday. While not overly strong, the long fetch will likely
result in small craft advisory conditions for the shores of
southern Lake Michigan.
In the near term, a cold front has become nearly stationary near
the north shore of the Lake in the Upper Peninsula. Low pressure
is expected to develop along this front over Wisconsin tonight,
moving northeast over far northern Lake Michigan early Tuesday
morning and trailing a cold front which will push down the lake
during the day. The low is expected to deepen later in the day as
it pulls away into Quebec, setting the stage for breezy northwest
winds across the lake. These north-northwest winds will continue
into Wednesday before weakening as high pressure spreads into the
region. The high eventually late Thursday, allowing winds to
diminish and waves to subside. The strongest winds, 20-25 kts, are
expected late Tuesday and Tuesday night, with small craft
advisory conditions expected along the southern shores of the lake
from Tuesday afternoon through Wednesday.
Ratzer
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...Beach Hazards Statement...INZ002...1 PM Tuesday to 4 PM
Wednesday.
LM...Small Craft Advisory...LMZ744-LMZ745...1 PM Tuesday to 4 PM
Wednesday.
&&
$$
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Area Forecast Discussion...UPDATED
National Weather Service Norman OK
906 PM CDT Mon Aug 21 2017
.UPDATE...
Modified PoPs earlier for activity moving into southwest/west-
central Oklahoma. Continued development possible into the
overnight hours southwest into north-central Oklahoma within plume
of elevated moisture. Convective development late tonight into
early tomorrow morning near frontal boundary still plausible, with
stronger/more extensive storm development late tomorrow into
tomorrow night primarily near and south of I-40.
&&
.PREV DISCUSSION... /issued 610 PM CDT Mon Aug 21 2017/
AVIATION...
VFR conditions to continue tonight with mainly mid-clouds expected
to increase across the area. There is also an increasing
chance for shower/thunderstorms to impact GAG/WWR overnight.
Elsewhere, chances remain too low to mention overnight. A front will
drop south to near or just south of I-40 Tuesday afternoon and will
be focus for additional thunderstorm development. Will include a
prob30 at several of the sites for late in the forecast. Still
anticipate VFR conditions.
30
PREV DISCUSSION... /ISSUED 440 PM CDT Mon Aug 21 2017/
DISCUSSION...
Storm chances begin to go up this evening, mainly across
northwestern Oklahoma, although the RAP and especially the 18Z NAM
suggest chances farther south into west central Oklahoma than
earlier expected this evening. Have expanded POPs farther south,
but will watch trends to see if additional adjustments will be
necessary. A cold front will move into the area tomorrow morning,
with additional storms expected to redevelop near the front
tomorrow afternoon. But the front will also being mild-for-August
weather with high temperatures generally expected to be in the 80s
beginning Wednesday and through the end of the week. Some
precipitation chances will persist (mainly south) with the
surface front somewhere in the vicinity mid-week. As we get
farther into the week, the will be some additional uncertainty
with precipitation chances influenced by the track of the tropical
system currently south west of the Yucatan Peninsula that models
suggest may move north through the western Gulf and perhaps into
the southern Plains.
&&
.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK 75 92 70 84 / 20 50 50 20
Hobart OK 76 95 70 86 / 30 50 50 30
Wichita Falls TX 77 98 72 88 / 10 20 50 30
Gage OK 72 89 65 85 / 30 40 20 10
Ponca City OK 76 90 65 85 / 40 40 20 10
Durant OK 75 95 73 88 / 10 20 50 40
&&
.OUN WATCHES/WARNINGS/ADVISORIES...
OK...None.
TX...None.
&&
$$
11/30
Area Forecast Discussion
National Weather Service Pueblo CO
304 PM MDT Mon Aug 21 2017
.SHORT TERM...(This evening through Tuesday)
Issued at 303 PM MDT Mon Aug 21 2017
Scattered thunderstorms developing over the mountains as of 21z,
with greatest coverage so far near the Continental Divide from
Monarch Pass northward. Over the plains, surface cold front was
slowly moving southward, with boundary just north of the Arkansas
River at mid afternoon. For the rest of the afternoon and into the
evening, expect isolated to scattered storms to continue to develop
over the mountains, with very slow/erratic storm motions as steering
currents have a very weak ely component west of I-25. On the plains,
last few runs of the HRRR and NAM both suggest at least isolated
activity developing along the cold front as it continues to push
south, and expect most storms to end up south of the Arkansas River
by mid to late evening. Main threat from any storms will be heavy
rainfall, with 06z NAM hinting at higher QPF amounts over the San
Juans/La Garitas this afternoon, then potentially over the srn
Sangres/Raton Mesa later in the evening. Front continues to sink
south overnight, and will keep some low pops for at least showers
going into Tue morning over the srn mts and near the Raton Mesa,
where N-NE upslope is maximized and residual convection is slow to
dissipate.
Cold front will be well south of the area on Tue, with
cooler/moister air mass over the plains through the day. GFS and NAM
both break out convection in the morning across much of the region,
with convective focus shifting across the mountains in the
afternoon. NAM would suggest little/no precip over the plains after
18z despite reasonably unstable (CAPE around 1000 J/KG) air mass,
while GFS hints at enough wly steering flow to push mountain storms
onto the plains late in the day. Will keep pops fairly high in the
mountains, with a broadbrush of isolated to sct at lower elevations.
Heavy rain again the main storm threat with weak shear and slow
storm motions. Max temps will run several degf lower than Mon along
and east of the mountains, while areas farther west see readings
just slightly cooler.
.LONG TERM...(Tuesday night through Monday)
Issued at 303 PM MDT Mon Aug 21 2017
Relatively active weather is expected to continue, with daily
chances for showers/tstms, especially over and near the higher
terrain, as moisture remains over the area and occasional weather
disturbance move across the state Tue night through Sat night.
At this time, it looks like the southeast CO plains could see fairly
widespread pcpn chances Thu night as one of those disturbances moves
acrs the area. Sat night, another disturbance drops southward
through eastern CO and could again bring widespread pcpn.
On Sun and Mon an upper level ridge is expected to be centered over
UT and will cover the western U.S. Overall, southern CO looks drier
on these days but there will likely still be enough residual
moisture for afternoon and evening pcpn over some of the higher
terrain.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 303 PM MDT Mon Aug 21 2017
Thunderstorms will drift across the lower elevations/adjacent plains
late this afternoon and into the evening. Will carry VCTS this
afternoon and early this evening at all 3 terminal sites, with
lowest chance at KPUB. VFR cigs along with locally heavy rainfall
and erratic gusty winds up to 45 kts will be the primary storm
threats. Thunderstorms will diminish this evening with winds
shifting to the north at both KCOS and KPUB as a cold front moves
through. Could see some isolated -shra Tue morning across the area,
then more widespread convection develops over the mountains after
18z. Expect a risk of tsra at all taf sites after about 20z as
storms drift away from the higher terrain.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...PETERSEN
LONG TERM...28
AVIATION...PETERSEN
Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
730 PM EDT Mon Aug 21 2017
.UPDATE (Overnight through Tuesday)...
23Z water vapor and H4 RAP analysis shows the Florida
peninsula resides between a large expanse of upper ridging
from Carolinas/Georgia to the western Atlantic...and an
upper trough retrograding westward across the
central/western Gulf of Mexico. A swath of quite dry
mid/upper level air has pivoted over the central and
southern peninsula during the past 24 hours from the SE
within the large-scale flow between these two features.
This drier air as significantly held back the coverage of
storms from the I-4 corridor southward this
afternoon/evening. We were actually able to mix high enough
to tap into this drier air...and evaporate quite a bit of
the cumulus field. This process that began a bit before the
effects of the passing eclipse shadow was actually enhanced
by the loss of solar insolation. An even more dramatic
decrease in cumulus coverage was evident in satellite
imagery closer to where totality passed well off to our
north.
Have seen a few widely scattered storms the past few hours
across the Nature coast where the impacts of the drier air
have not been as great today. However, the swath of drier
air will continue to pivot slowly north and northwest the
next 24 hours, and it will be these nature coast zones
(north of I-4) that see the greatest impact/suppression of
storms from the dry air during Tuesday.
So, for the rest of tonight, the few isolated shower that
have been able to survive the hostile thermodynamic
environment aloft will dissipate with sunset and loss of
diurnal heating. The remainder of the overnight will see a
dry forecast, with typical August overnight temperatures.
Tuesday, the dry forecast continues over the landmass
through the morning hours, with just a slow development of a
few-sct cumulus field. As mentioned above, the driest mid-
level air will have move up over the Nature Coast zones to
the north of I-4, and it will be these areas that struggle
to see much in the way of showers/storms during the
afternoon/evening.
A renewed influx of deep moisture will be slowly trying to
move back into the central and southern part of the FL
peninsula, with greatest influence the further south and SE
one travels. Therefore, isolated storms (20% PoPs) are
expected in and around the I-4 corridor the second half of
Tuesday, ramping up to scattered coverage (30-40%) down
toward Sebring/Punta Gorda/Fort Myers).
Temperatures look quite warm for your Tuesday, with many
spots...even close to the coast...reaching the middle 90s.
Have a great evening everyone!
&&
.AVIATION (22/00Z through 23/00Z)...
VFR conditions will prevail for all terminals through much,
if not all, of the the TAF period. Light easterly or
northeast winds overnight will continue into the daylight
hours of Tuesday, with some potential for winds to turn NW
during the afternoon at KTPA/KPIE/KSRQ. Thunderstorm
potential will still be below normal, although returning
moisture will increase the chance for a passing storm at
KPGD/KFMY/KRSW late in the afternoon or evening. Potential
further north is still low enough to exclude form current
TAFs.
&&
.Prev Discussion... /issued 351 PM EDT Mon Aug 21 2017/
SHORT TERM (Tonight-Tuesday)...
One tropical wave lifting off to the NW over northern FL,
another wave in place over the eastern Bahamas, and high
pressure ridging in between with a little dry slot across
the central and southern zones this afternoon. This drier
mid level air is limiting rain chances for this afternoon,
with the greatest chances in place across the Nature Coast.
These features will continue to shift to the W/NW through
Tuesday with the dry slot lifting north and moisture
returning from the south as the tropical wave approaches and
then moves over southern FL through Tuesday. For Tuesday
afternoon, the Nature Coast will have low rain chances,
while the southern half of the area increases to 40-50
percent chances. Generally E/NE flow will be in place
through the period, with a weak sea breeze possible near the
coast Tuesday afternoon. Temperatures will be near normal
for lows, generally in the 70s, and highs will be on the
warm side in the lower to mid 90s.
LONG TERM (Tuesday Night through Next Monday)...
The start of the long range period will feature a strong
upper trough centered over the Great Lakes with upper
level high pressure from the western CONUS into the Gulf of
Mexico. At the surface, high pressure will extend across the
western Atlantic Ocean and the Gulf of Mexico with a weak
tropical low across the far eastern Gulf.
The forecast remains highly uncertain with respect to the
tropical low/easterly wave expected to move across the
southern tip of Florida or Florida Straits. This feature is
currently being affected by an area of drier air and weak
wind shear, which is good because it limits the potential
for this feature to strengthen into a tropical cyclone.
However, conditions may become slightly more favorable by
Wednesday. So if this low makes it into the eastern Gulf of
Mexico, it will have to be monitored closely. Given the
feature is generally being poorly resolved, models vary in
its position over the next 72 hours, with some solutions
showing it over the Gulf and others just of the east coast
of Florida. In the current forecast, we expect the low to
track across south Florida, bringing greatly increased rain
chances to areas along and south of I-4. The most recent
guidance shows this low will remain a relevant feature
through the latter half of the week as it slowly meanders
either over south Florida, or just off the southwest Florida
coast. It goes without saying, this will need to be watched
closely for potential tropical development. At the very
least, this feature will maintain high rain chances each day
as deep tropical moisture mingles with the seabreezes and
daytime heating. Locally heavy rainfall may also become a
concern, especially south of I-4 where the greatest QPF
signal is apparent.
Heading into the weekend, a potent shortwave is expected to
lead to a deepening of the Great Lakes trough, allowing a
cold front to drop southward into the southeast U.S. The
more aggressive European brings the drier post frontal air
all the way into northern Florida with the more reserved GFS
confining it more to Georgia and the Carolinas. In both
cases, an interaction between the remnants of the tropical
disturbance and the frontal boundary will likely promote
heavy rainfall across portions of the southeastern U.S.
including Florida.
Temperatures will remain seasonal, becoming slightly cooler
for the latter half of the week into the weekend as
humidity increases.
MARINE...
Winds will increase with an easterly surge overnight as the
area remains in weak high pressure between two tropical
waves, one over northern Florida, and the other over the
eastern Bahamas. The features will shift west through mid-
week, with high pressure then returning over the waters for
the end of the week. Scattered showers and storms possible
as moisture returns across the area through the rest of the
week. No headlines expected through the period.
FIRE WEATHER...
No concerns.
&&
.Preliminary Point Temps/PoPs...
TPA 78 94 78 92 / 10 20 10 30
FMY 77 95 77 92 / 10 40 40 60
GIF 75 95 76 94 / 0 30 10 40
SRQ 77 95 78 92 / 10 20 30 30
BKV 72 95 75 94 / 10 10 10 20
SPG 80 94 79 92 / 10 20 20 30
&&
.TBW WATCHES/WARNINGS/ADVISORIES...
FL...None.
Gulf waters...None.
&&
$$
UPDATE/AVIATION...Mroczka
PREVIOUS DISCUSSION...HUBBARD
...Update to aviation forecast discussion...
.SHORT TERM...(This evening through Tuesday)
Issued at 257 PM CDT Mon Aug 21 2017
19Z water vapor imagery shows a low amplitude shortwave moving
through the northern plains. A weak MCV from the early morning
convection has become difficult to discern over northeast KS and
likely has sheared out. Otherwise water vapor imagery shows a plume
of mid level moisture from wester TX through northeast KS. At the
surface, a prefrontal trough was noted from northwest KS into the
eastern Dakotas with a cold front over western ND and into eastern
WY.
For tonight models still show some weak vorticity advection ahead of
the northern plains shortwave and some frontogenesis overnight with
the front. With the very moist airmass in place, showers and
thunderstorms are expected to become widespread this evening and
move through the area overnight. Models have trended slightly faster
with the frontal system and some of the high resolution models show
precip exiting the forecast area to the southeast by 7 am Tuesday.
The clouds and shower activity have slowed down the destabilization
of the boundary layer. But RAP analysis suggests MLCAPE values over
2000 J/kg beginning to develop. Deep layer shear remains a little
marginal, but look to be good enough that if a discrete storm were
able to persist it could go on to produce some severe hail and
winds. Aside from that, the main focus remains on the heavy rain
potential. With PWs still progged over 2 inches, the airmass looked
primed for heavy rainfall. Although with the model trends of a
faster progression to the frontal system, the risk for flash
flooding looks to have diminished somewhat. While the ensemble means
for QPF have also lessened, a few members continue to show the
potential for isolated heavy to excessive rain. Because of this will
maintain the flash flood watch as is.
Showers and thunderstorms should be moving southeast of the area
Tuesday morning and have POPs decreasing with virtually a dry
forecast for much of the area by noon. The stronger cold air
advection looks to hold off until late morning or early afternoon so
Lows tonight are expected to remain muggy with readings in the upper
60s to around 70. Have trended highs cooler by a degree or two with
models showing decent low level cold air advection through the
afternoon. Have forecast highs in the lower and middle 80s.
.LONG TERM...(Tuesday night through Monday)
Issued at 257 PM CDT Mon Aug 21 2017
By Tuesday night, the mid-level trough will be shifting into the
northeastern U.S. with surface high pressure sliding southward from
the Northern Plains into the central U.S. The region will remain
under the influence of this surface high pressure and northwesterly
flow aloft through Thursday, resulting in dry conditions and
temperatures cooler than the seasonal normals with highs in the low
80s.
By Thursday night, models show a mid-level ridge briefly building
into the central U.S. ahead of a mid-level trough diving into the
Pacific Northwest. Models are in decent agreement with showing an
embedded shortwave developing within this ridge Thursday night and
gradually tracking across the CWA Friday and Friday night. The mid-
level trough over the Pacific Northwest will get pushed back into
Canada as a broad mid-level ridge builds across the western U.S.
Saturday through Monday. The central U.S. will remain under
northwesterly flow aloft into early next week, with models showing
additional embedded waves developing within the mid-level flow. As
a result, some periods of scattered showers and thunderstorms will
be possible from Thursday night into Sunday, with some isolated
precipitation possibly continuing into early next week. Temperatures
through the weekend and into early next week will remain below the
seasonal normals, with highs staying in the low 80s and low
temperatures in the low 60s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 610 PM CDT Mon Aug 21 2017
Scattered TSRA developing north and west of terminals currently.
Radar trends has the cluster through KMHK by 02Z with no
reduction in flight category. A little more uncertain how the band
of TSRA evolves as it moves eastward towards KTOP/KFOE. Sfc
analysis shows a frontal boundary in the area with ample
instability, despite meager amounts of wind shear. Have therefore
kept a mentioned of VCTS with scattered showers through 08Z when
short term models clear the convection eastward. Next focus is the
convection that develops along the front currently in Nebraska in
the 06-09Z time frame. Current indications is that coverage may
not be as widespread as previous guidance. Nonetheless kept the
mention of TSRA with MVFR stratus developing along and just behind
the boundary through 16Z.
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through Tuesday morning for KSZ011-012-022>024-
026-035>040-054>056-058-059.
&&
$$
SHORT TERM...Wolters
LONG TERM...Hennecke
AVIATION...Prieto
Area Forecast Discussion
National Weather Service Wakefield VA
201 PM EDT Tue Aug 22 2017
.SYNOPSIS...
High pressure remains centered off the Mid Atlantic coast
through tonight as a cold front begins to approach from the
west. The front crosses the area late Wednesday afternoon
through Wednesday night, with strong high pressure building
north of the area from Thursday into the upcoming weekend.
&&
.NEAR TERM /THROUGH TONIGHT/...
Latest surface analysis centers ~1021mb high pressure from
eastern NC to well off the coast, resulting in a light southerly
flow over the local area. Some lingering low clouds still
visible over southeast Virginia/northeast North Carolina, but
expect those clouds to dissipate in the next hour or so. Humid
conditions, with dewpoints ranging from the low 70`s northwest
to upper 70`s southeast.
For today, increasing return SSW flow will prevail on the back
side of departing high pressure offshore and ahead of an
approaching cold front. A weak thermal/lee trough by this aftn
will provide a bit more of a pressure gradient than the past few
days, resulting in SSW winds of 10-15 mph this aftn. Highs today
should rise about 2 to 5 degrees above Monday`s values, with
low-mid 90s for most locations (and only a little cooler near
the coast). Humid air mass remains entrenched over the area,
with dewpoints mixing down only into the low to mid 70`s. Heat
indices this afternoon will approach 105 F for an hour or two,
especially across southeast Virginia and northeast North
Carolina. Given that it will be marginal and latest guidance and
trends are consistent, did not issue a heat advisory but will
mention in the HWO. While the atmosphere will be quite moist
with precipitable waters around 1.75 inches, warm air aloft,
weak lapse rates, and a lack of appreciable forcing will limit
the convective potential this afternoon. Will retain silent PoPs
for most areas, did add a 20% over a few spots across interior
NE NC where RAP and hi-res guidance indicate some convergence
away from the coast. Warm/humid tonight with little chance for
any rain under a SW wind of 10 mph. Lows mainly in the mid to
upper 70s. Clouds increase across the north ahead of the
approaching cold front and lead shortwave. Have introduced a
slight chance PoP for the Maryland Eastern Shore late tonight,
but best chances for measurable precipitation remain north and
west of the local area.
&&
.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
Better forcing arrives along the front Wednesday as a lead wave
drops over the Mid-Atlantic. The cold front progged to slowly
push across the area Wednesday afternoon into Wednesday night.
Latest models generally depict somewhat weaker forcing with the
lead wave as the vort gets sheared out, and have dropped PoPs a
little from previous forecast through 18Z. PoP`s increase more
during the 18Z/Wed to 00Z/Thu period, with some sharpening of
the upper trough looking to focus best lift over southern/SE
zones. Will have high chc PoPs N/NW zones to likely over the
S/SE late in the day. The air mass ahead of the front will
become modestly unstable, with mixed- layer CAPE values progged
around 1000-2000 J/kg. Deep layer flow also progged around 25-30
knots as mid level flow increases, resulting in better
organization and overall storm strength. Mid level lapse rates
also improve to around 6 to 6.5 C/km late. SPC maintains a
marginal risk for severe weather for most of the CWA, with
damaging winds and heavy rainfall the main threats. The NW,
where PoPs are a little lower and where the lift is weaker is
not included in the marginal risk at this time. Highs generally
in the mid-upper 80`s north to around 90 F south.
Strong Sfc cold front drops south across the area Wednesday night
into Thursday morning. Modest ascent accompanies the front within
the RRQ of a ~110kt jet over New England, along with PW values
to around 2.0" (around +1 st dev). By Wed evening, have
maintained highest (70%/Likely) POP across srn VA/NE NC, with
slight to low end rain chances by Wed night NW of RIC, where
drier air arrives first. PoPs across SE portions gradually
diminish to high chance by daybreak Thu morning. Thunder will
be maintained into Wednesday evening, with showers thereafter as
stable NE flow prevails in the wake of the front. Drier air
gradually filters in from the NW late Wednesday night into
Thursday with partial clearing across the nrn tier counties.
Lows lower 70s SE to mid-upper 60s NW.
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...
The pattern will be characterized by the gradual development of
a longwave upper level trough over the eastern United States
for the late week period into next weekend. Meanwhile, broad
1024+ mb surface high pressure builds south over the interior
northeast from Great Lakes Thursday and Friday, eventually
setting up over New England and ridging down the east coast over
the weekend into early next week.
Resultant E-NE flow will result in markedly cooler and drier
conditions over the region, with early morning lows in the 50s
to lower 60s inland to mid-upper 60s along the coast.
Maintained a dry forecast through the forecast period. Overall,
high temperatures Thu-Mon will be below normal for late August,
mainly in the upper 70s to low 80s.
&&
.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
VFR and dry conditions prevail to begin the 18Z TAF period as
high pressure remains centered just offshore. Scattered cu with
decks around 3 to 4k feet AGL has developed across the region.
South to southwest winds generally 10-15 knots. Few gusts to 20
knots inland. Not much chance for any tstms today or this
evening.
A cold front approaches the region late tonight, but with a
continued SW flow, expect VFR conditions tonight/early wed
morning with fog/low stratus unlikely. Flight restrictions will
be possible with the front later on Wednesday...mainly in the
afternoon and through Wednesday night due to showers and
thunderstorms. The front should exit the coast Thursday morning
with lingering showers possible across far SE VA/NE NC.
Conditions are anticipated to improve Thursday afternoon into
Friday as the front shifts farther southeast and high pressure
builds north of the region. Breezy NE winds expected near the
coast Thursday and Friday.
&&
.MARINE...
Early this morning, sfc high pressure was cntrd off the Mid Atlc
coast. Winds were SSW 5 to 15 kt over the waters with Waves 1 to
2 ft, and Seas 2 to 3 ft. The high will slide farther out to
sea during today. A cold front will approach the waters from the
NW tonight, then crosses the area Wed thru Wed night. High
pressure will then gradually build down into the region from the
NW Thu aftn into Sat.
SSW winds will increase later today into tonight, as the front
approaches the waters fm the NW. Have kept wind speeds at 15 kt
for the Ches Bay tonight, and 15 to 20 kt for the coastal
waters, with a few gusts up to 25 kt possible over the nrn two
coastal zns. Waves will build to 2 to 3 ft in the Ches Bay, and
Seas will build to 3 to 5 ft over the nrn coastal zns. Thus,
have issued a SCA for the nrn two zns (650-652) fm late this
evening into early Wed morning. Winds shift to the N/NE behind
the front fm later Wed aftn into Thu morning, mainly 10 to 15
kt.
Post-frontal, look for onshore (NE flow) for the remainder of
the forecast period, as high pressure builds in fm the NW.
Expect wind speeds at 10 to 15 kt (could be gusts to 20 kt) acrs
most of the waters, with the highest winds over the SE VA/NE NC
waters. Waves will be 1 to 3 ft, and Seas will be 2 to 4 ft.
&&
.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...None.
NC...None.
VA...None.
MARINE...Small Craft Advisory from 10 PM this evening to 6 AM EDT
Wednesday for ANZ650-652.
&&
$$
SYNOPSIS...LKB
NEAR TERM...LKB/SAM
SHORT TERM...LKB/SAM
LONG TERM...MAM
AVIATION...LKB/SAM
MARINE...TMG
Area Forecast Discussion
National Weather Service Albany NY
147 PM EDT Tue Aug 22 2017
.SYNOPSIS...
Warm and muggy conditions are expected today with showers and
thunderstorms developing ahead of a cold front, mainly this
afternoon into this evening. Any thunderstorm will be capable of
producing gusty winds and heavy rainfall. The threat for showers
and thunderstorms will end tonight with the passage of the cold
front. Much cooler and drier air will move into the region tomorrow,
with dry and comfortable conditions expected for the rest of the
week.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
...Tornado Watch 461 is in effect until 9PM for the Adirondacks,
Mohawk Valley, and Warren county...
As of 130 PM EDT, Strong line of convection has developed across
western NY/eastern Great Lakes with some isolated cells expected ahead
of it. This main line of convection will make its way eastward
and into the forecast area from NW to SE beginning around 20Z,
where damaging winds and heavy rain will be the primary threats.
Cannot rule out an isolated tornado/spin-up along the convective
line, especially in the Adirondacks and Mohawk Valley regions
where there is a tornado watch. That being said, made no major
changes to the forecast but freshen up the hourly temps and sent
updates to NDFD and web servers.
Prev Disc...
As of 1041 AM EDT...skies range from clear to mostly cloudy
around the area. temperatures are in the 70s to around 80F.
dewpoints have risen to around 70F. Winds are generally from a
southerly direction. Isolated showers and thunderstorms popped
up this morning along back door warm front. These showers have
dissipated.
The surface cold front is still crossing Michigan, still well
upstream. With 850 hpa temps rather warm (16-18 degrees C), it
should be yet another warm day. Max temps look to reach the mid
to upper 80s for valley areas by early afternoon and dewpoints
will be very sticky in the mid to upper 60s.
Previous...
As the cold front and upper level trough continues to move
eastward, some scattered showers/thunderstorms should develop
along a pre-frontal trough by the early to mid afternoon hours
for the Adirondacks, as seen in the 3km HRRR and NAM. There
could be multiple bands of thunderstorms for late today, as
more organized convection (perhaps a QLCS) looks to develop just
ahead of the front boundary for late this afternoon into this
evening and move across the entire region from west to east.
There is considerable concern for some strong to severe
thunderstorms today. 0-6 km bulk shear increase to 35-45 kts by
late today, especially across northern/western areas. There is
also a decent amount of shear within the bottom 1-2 km (as much
as 30-35 kts), especially just ahead of the frontal boundary
across the Hudson Valley, where the low-level flow will remain
backed within the valley, resulting in locally higher helicity.
This would favor the development of a localized tornado threat,
especially in any supercells that develop and any notches along
a QLCS.
There still is question about the exact degree of instability,
and the models still vary the amount of CAPE that will be
present. Considering the warm/humid air mass, 1500-2500 J/kg of
surface-based CAPE is reasonable. If dewpoints are a little
lower than what models suggest, it could be more in the
1000-2000 J/kg range, but still more than sufficient to support
severe thunderstorms. One mitigating factor will be that mid-
level lapse rates will be rather weak due to the warm temps
aloft, generally less than 6 deg/km. Still, the strong shear and
dynamical forcing should be enough to support organized and
persistent thunderstorms today.
As a result, SPC has placed the western and central Adirondacks
and Mohawk Valley in an Enhanced Risk for severe storms, with a
slight risk across much of the remaining parts of the area. Main
threat is damaging winds, but cannot rule out an isolated
tornado or large hail within any discrete cells.
In addition, PWATS rising in excess of two inches would result
in a threat for heavy rainfall within a short period of time,
which could result in localized flooding, especially for urban
and poor drainage areas. Although the fast flow aloft should
keep cells moving, the expected multiple rounds of convection
could result in some training, which may allow for excessive
rainfall in some areas. WPC has much of the area in a slight
risk for excessive rainfall today, so flash flooding cannot be
ruled out today.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/...
Thunderstorms will be continuing this evening, with the main
threat for severe storms through about midnight, as storms track
west to east across the area. The threat for showers and
thunderstorms should end with the passage of the cold front by
late tonight, with lows remaining in the 60s.
Behind the front, cooler and less humid air will work into the
region for the middle of the week. Mainly dry weather is
expected through the rest of the short-term period, although
cannot totally rule out a lingering rain shower across the
Adirondacks or Mohawk Valley for later Wednesday into Thursday,
as the passing upper level trough picks up some moisture off
Lake Ontario and allows for a lake- enhanced shower or two.
Highs on Wednesday will reach the mid 70s to low 80s, but temps
on Thursday only look to reach the low to mid 70s for valley
areas. Overnight lows will mainly be in the 50s, with some 40s
across the higher elevations. Sky cover will generally be partly
cloudy.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
Extended period of fair weather with slightly below normal
temperatures.
Canadian high pressure at the surface will build in and shift
southward as it expands across the Great Lakes region and the
Northeast over the weekend into early next week. An upper level
trough will remain over region however heights are expected rise
some as the trough weakens.
Short waves are expected to rotate through the trough however
guidance differs on the timing and strengthen of them; mainly
expecting an increase in cloud cover as the individual short waves
approach and move through.
Looking at temperatures around 5 degrees below normal with highs
generally in the mid 60s to upper 70s and lows in mid 40s to mid
50s. Cooler readings are expected across the higher terrain of the
western Adirondacks, eastern Catskills and southern Green Mountains
of Vermont.
In addition to the cooler temperatures, we will have low humidity
levels with dew points in the 40s and lower/mid 50s.
&&
.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
Line of showers and some strong thunderstorms currently extends from
the Saint Lawrence River Valley southwest to Watertown, Rochester
and then to Bradford, PA. We expect this line to gradually move
southeast this afternoon and evening and bring thunderstorms to all
the TAF sites between 23/00Z and 23/05Z. A stray shower or storm is
possible this afternoon at the TAF sites, but only a low probability
Highest probability is at KGFL.
Gusty south to southwest winds of 10 to 20 kts expected today.
Frontal passage is expected between 06Z and 12Z Wednesday with the
winds shifting to the northwest behind the front. Winds Wednesday
will be mainly from the northwest at 5 to 15 kts.
Outlook...
Wednesday-Saturday: No Operational Impact. NO SIG WX.
&&
.FIRE WEATHER...
Ahead of an approaching frontal boundary, it will be warm and
muggy today. RH values will only fall to 55 to 65 percent this
afternoon. Most areas should see a wetting rainfall due to
passing afternoon and evening showers and thunderstorms.
Southerly winds will be 10 to 20 mph today, and will switch to
the west by tonight at 5 to 15 mph.
Behind the front, cooler and less humid conditions will be in
place for the rest of the week. RH values look to fall to 45 to
55 percent on Wednesday afternoon with westerly winds of 10 to
20 mph.
&&
.HYDROLOGY...
An approaching cold front will allow for showers and
thunderstorms today, mainly during the afternoon and evening
hours. Any thunderstorm will be capable of producing locally
heavy downpours and could lead to isolated flash flooding. The
locally heavy rainfall may also result in minor flooding of
urban, poor drainage and low lying areas. Behind this frontal
system, mainly dry weather is expected for the rest of the week.
Basin average rainfall on Tuesday will generally be around a
half of an inch to an inch, although point totals may be
higher. This rainfall will only allow for minor rises on rivers
and streams. River and stream levels should quickly recede by
Wednesday and then remain steady for the rest of the week.
For details on specific area rivers and lakes, including
observed and forecast river stages and lake elevations, please
visit the Advanced Hydrologic Prediction Service /AHPS/ graphs
on our website.
&&
.EQUIPMENT...
The KENX radar will likely be down through at least Friday,
September 1st for the bull gear replacement. We are waiting for
a ROC maintenance team and parts to arrive to assist local
technicians with the repairs.
&&
.ALY WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...Tornado Watch until 9 PM EDT this evening for NYZ032-033-
038>040-042-082-083.
MA...None.
VT...None.
&&
$$
SYNOPSIS...SND
NEAR TERM...SND/JVM
SHORT TERM...Frugis
LONG TERM...IAA
AVIATION...SND
FIRE WEATHER...Frugis
HYDROLOGY...Frugis
EQUIPMENT...
Area Forecast Discussion
National Weather Service Gaylord MI
128 PM EDT Tue Aug 22 2017
.UPDATE...
Issued at 1017 AM EDT Tue Aug 22 2017
Secondary cold front/trough swinging through Northern Lower
Michigan this morning with a band of mainly showers and possibly a
rumble of thunder. Fairly tight gradient with fropa and have seen
some gusty winds of 30-40 mph along the nearshore waters. The
gustier winds will be translating across the rest of the CWA over
the next few hours, highest along some of our coastal locations. I
raised POPS across much of the area for the next few hours as the
front moves through. Quite a bit of subsidence/dry air coming in
for the afternoon hours, so clouds should scatter out with
increasing sunshine for most areas. Temperatures fairly steady for
the afternoon hours. The most noticeable difference for the
afternoon hours will be steadily lowering dewpoints - much less
humidity!
&&
.NEAR TERM...(Today through Tonight)
Issued at 342 AM EDT Tue Aug 22 2017
High impact weather potential: Thunderstorms early this morning.
Pattern synopsis and forecast:
Upper level troughing was working into the western Great Lakes early
this morning, with an associated sfc low pressure deepening while
tracking into eastern Lake Superior. The system cold front extended
from this low back through eastern Wisconsin and Iowa. Showers and
some isolated thunderstorms have finally developed over the last
couple of hours as low level convergence and DPVA have increased
within a region of 400-900 j/kg of MUCAPE. Latest RUC analysis also
suggests that maybe some right entrance region dynamics from 100+kt
jet are in play. Quite the warm/muggy morning with temperatures and
dew points in the middle 60s to lower 70s.
Upper troughing settles in over the region through the day with the
sfc low lifting into Quebec, while dragging the cold front through
nrn Michigan this morning into early afternoon. The forcing
continues to increase through daybreak with showers and isolated
storms likely to continue to increase in coverage. No severe storms
with not much instability around and lapse rates not all that
impressive at less than 6c/km. A secondary sfc trough axis looks to
follow behind the cold front, resulting in a band of lighter rains,
especially into the higher terrain of nrn lower. There is likely to
be some afternoon cumulus, but the overall air mass dries through
this evening. As cold advection continues through the night however,
temperatures get cold enough for overlake instability, almost to
850mb. Gotta believe that lake effect clouds in NW flow will be
common by daybreak Wednesday.
Highs not really going anywhere through the day with middle 60s to
lower 70s, slightly higher in downsloping areas of NE lower. Lows
tonight in the middle 50s most areas with less humidity.
&&
.SHORT TERM...(Wednesday through Thursday)
Issued at 342 AM EDT Tue Aug 22 2017
...Cool weather for midweek...
High Impact Weather Potential: Minimal.
Pattern Forecast: North American pattern features a decent short
wave trough for late August moving through the Midwest and adjacent
portions of Manitoba/Ontario. Overall pattern from the Midwest back
into the eastern Pacific has become more amplified over the past 36
hours with short wave ridging having developed over British Columbia
downstream of a compact upper low south of Alaska. Associated with
the Midwest short wave trough is a 1008mb surface low over northeast
Minnesota...with an eastward extending warm front across Upper
Michigan and into southern Quebec...and a trailing cold front back
into northwest Iowa/Nebraska. Plenty of humidity south of the warm
front with dew points well into the 60s/precipitable water values in
the 1.50-2.00 inch range (1.58 inches on 00z APX sounding).
Cold advection into the mid level short wave trough moving through
the Midwest suggests continued deepening of this feature...
eventually closing off north of the Great Lakes later today. The
result will be deep layer cyclonic flow across Michigan for the
midweek period...followed by rising heights for the end of the week
as short wave ridging crosses the prairie provinces. Impressive
surface low for late August will drag cooler air across the Great
Lakes...followed by high pressure building in for Thursday/Friday.
Thermal troughing will ensure a much cooler pattern.
Primary Forecast Concerns: Cold air getting pulled across the lakes
should bring about a good deal of lake plus diurnally induced cloud
cover Wednesday. Some scattered light rain showers also possible
within typical northwest flow lake effect areas at least into early
afternoon. Breezy day expected with gusts 20-25+mph...winds should
subside by Wednesday evening. Highs Wednesday will be mostly stuck
in the 60s...generally 8-12 degrees below normal.
No real issues for Thursday outside of some nuisance cloud issues
between thermal trough in place and short wave trough rotating
across the area from the north...again probably through early
afternoon with decreasing clouds north to south. Probably another
afternoon with highs in the 60s...and chilly Friday morning where
some of the typical cold spots will probably drop into the 30s.
.LONG TERM...(Thursday night through Monday)
Issued at 342 AM EDT Tue Aug 22 2017
High Impact Weather Potential: Minimal.
Great Lakes looks to be stuck in split flow between ridging across
northern Ontario and a southern branch weakness that develops over
the Mississippi Valley this weekend. The result is fairly weak
upper level flow across Michigan for the weekend. High pressure
will be in place Friday...and given lack of "direction" from above
will probably linger through the weekend though a couple short wave
troughs may slide across Michigan. How weakness in the southern
branch of the split flow evolves early next week is uncertain.
Overall weather looks quiet through the weekend...with a moderating
trend in temperatures.
&&
.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 122 PM EDT Tue Aug 22 2017
A cold front has pushed through the area, with generally MVFR CIGS
in its wake. Drier air is working into the area from the northwest
and this will continue through the afternoon hours, resulting in
clouds gradually scattering out. This evening will likely be
fairly clear, before cold air advection over the warm lakes
begins to produce lake clouds overnight. These clouds will
persist through the first half of Wednesday. VFR cigs are
generally expected at this time, with pockets of MVFR possible. A
few light lake effect rainshowers are also possible.
Northwest winds will be gusty both this afternoon and Wednesday,
with a strong gradient across the Great Lakes. Gusts of 20+ kts
are expected this afternoon, subsiding some tonight, with gusts
of 20+ kts expected again on Wednesday.
&&
.MARINE...
Issued at 342 AM EDT Tue Aug 22 2017
A cold front will sweep across the region this morning into early
afternoon, with winds shifting out of the NW and becoming quite
gusty due to a tight gradient and developing overlake instability.
Widespread advisory winds, with low end Gales expected in Whitefish
Bay and through Presque Isle light for this afternoon and evening.
Advisory speeds will be common in most nearshore waters into
Wednesday before higher pressure approaches Wednesday night into
Friday. Showers and isolated non severe storms ahead of the front
this morning.
&&
.APX WATCHES/WARNINGS/ADVISORIES...
MI...BEACH HAZARDS STATEMENT through late tonight for MIZ016-019>021-
025-031.
LH...SMALL CRAFT ADVISORY until 6 PM EDT Wednesday for LHZ345-346-349.
GALE WARNING until midnight EDT tonight for LHZ347-348.
LM...SMALL CRAFT ADVISORY until 6 PM EDT Wednesday for LMZ323-341-342-
344>346.
LS...SMALL CRAFT ADVISORY until 6 PM EDT Wednesday for LSZ322.
GALE WARNING until midnight EDT tonight for LSZ321.
&&
$$
UPDATE...JK
NEAR TERM...SMD
SHORT TERM...JPB
LONG TERM...JPB
AVIATION...JK
MARINE...SMD
Area Forecast Discussion
National Weather Service State College PA
244 PM EDT Tue Aug 22 2017
.SYNOPSIS...
A strong cold front will move through the region late today and
early tonight. Much cooler and drier conditions will return for
the second half of the week. Temperatures will average a few
degrees below normal highs starting tomorrow and lasting into
early next week.
&&
.NEAR TERM /THROUGH TONIGHT/...
Radar motor was installed and it has been up for over an hour.
In a nick of time.
Updated forecast to show the potential for severe thunderstorms
this afternoon and evening. First lead cells developed over
Warren County. Stronger storms are to our west. The NCEP and GSD
HRRR show at least two potential lines this afternoon and
evening. With deep cores and 850 hPa winds 40 to 55kts strong
and severe winds at the surface are possible.
Tornado watch was for more QLCS type tornadoes. Though we have
had a few initial rotating cells in KCCX and KBUF radar. More
linear features to our west.
Ahead of the convection a very hot humid Summer day. Farther
east you live the more likely this day will end on a good note
as convection will be in evening and SPC may issue watch for
eastern PA later this afternoon.
Behind the line POPS drop fast and drier air comes. Some areas
of fog possible. But a cooler and drier AM Wednesday.
&&
.SHORT TERM /WEDNESDAY/...
Wednesday will be noticeably drier as the PW values crash to -1
sigma below normal after being well +1 to +2 sigma above
normal. It will also be significantly cooler. The 850 hPa
temperatures fall to near normal Wednesday and will fall below
normal overnight Wednesday into Thursday.
Chance of rain should be very low Wednesday.
The cool air aloft will likely produce some cumulus in the
mountains during the afternoon hours.
It should be a nice and notably cooler day.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
An extended period of early autumn-like weather will begin
Wednesday and continue right through the upcoming weekend as a
-2 sigma upper trough (and similarly anomalous/cool 850 mb
temps) move over the Great Lakes and NE U.S.
1026-1028 mb SFC High (+2-3 Sigma) over south-central Canada
will drift slowly to the Great Lakes by this weekend
Daytime high temps will be about 5-7 Deg F below normal across
the Western Mtns on Wednesday, though still just slightly below
normal across the SE zones prior to the arrival of the
deeper/colder air for the latter part of the week.
GEFS mean 850 mb temps will dip about 2-3 deg C in all locations
for Thursday-Sunday, leading to max temps averaging 5-10 F
below normal (with min temp departures about 10-13F below
normal Friday-Sunday) as a large Canadian High Pressure area
pushes SE across the Glakes Region and becomes centered over the
NE states.
Lows Fri/Sat/Sun mornings with high centered overhead will be
dipping into the l-m 40s over the Northern Mountains (and deeper
valleys of the Central Mountains) and solidly into the 50s
elsewhere. Some of the perennial cold spots near and to the east
of KBFD could see readings of 38 or 39F.
&&
.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
Most of the eastern areas mostly sunny with some cumulus clouds
about making for a bumpy ride in the boundary layer. Over
western PA and OH there is a line of strong and severe storms.
Strong winds and large hail are possible. Check radar before
flying over western PA this afternoon and central areas this
evening.
The line of storms will move east this afternoon and evening.
Areas of patchy fog will develop around/after midnight. Spotty
MVFR and IFR.
Conditions will improve rapidly Wednesday morning, as cool
Canadian high pressure builds into the area.
.OUTLOOK...
Wed...AM low cigs BFD/JST, otherwise VFR.
Thu-Sat...No sig wx expected.
&&
.EQUIPMENT...
KCCX is fixed with new motor installed.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Dangelo
NEAR TERM...Grumm
SHORT TERM...Grumm
LONG TERM...La Corte/Lambert
AVIATION...Grumm/Lambert
EQUIPMENT...
Area Forecast Discussion
National Weather Service Duluth MN
110 PM CDT Tue Aug 22 2017
.SHORT TERM...(Today through Wednesday)
Issued at 321 AM CDT Tue Aug 22 2017
The remnants of a mid-level shortwave will move out later this
morning, which will bring a brief respite to any precipitation
chances this morning. However, as the shortwave departs to the east,
northwest flow aloft will continue, along with some weak cold air
advection. This will support chances of showers and perhaps a small
chance of a thunderstorm late this morning and through the
afternoon, mainly along the International Border and Iron Range
regions. Some of this activity may reach as far south as the Twin
Ports and South Shore regions as well as some of the convective-
allowing models (HRRR and NAMNest) are progging this solution. 850
mb temperatures will fall to the 6 to 8 degree C range, with some
decent instability possible, as MUCAPE values range from a few
hundred up to around 1000 J/kg. 850 mb wind speeds will also
increase, with values between 25 to 35 kts. NAM and RAP model
soundings both indicate some decent boundary layer mixing expected,
which will help to mix down these low-level winds. Moreover,
pressure rises from the west will enhance the sfc pressure gradient.
To account for this, I bumped up the winds a bit more from the
previous forecast package, leaning towards the MOS guidance. Wind
gusts across the Northland could increase up to 25 kts, with
possibly some isolated stronger gusts. Temperatures will be on the
cool side today, with highs ranging from the lower 60s over the tip
of the Minnesota Arrowhead, into the upper 60s and lower 70s further
inland.
Chances of showers and storms will quickly decrease this evening as
diurnal heating diminishes. As such, cloud cover should also
diminish. This, coupled with light winds, will lead to a night of
rather cool temperatures due to radiational cooling. Temperatures
over northern Minnesota could drop to as low as the lower 40s in
some spots. Due to the expected reduction in temperatures,
introduced some patchy fog to the forecast for tonight, mainly from
north-central Minnesota, southeast towards Hayward, WI. Most of the
day Wednesday looks to be dry, but cool, with highs in the mid to
upper 60s. A compact mid-level shortwave trough is progged to then
bring another round of showers to the Northland, late in the day
Wednesday.
.LONG TERM...(Wednesday night through Monday)
Issued at 319 AM CDT Tue Aug 22 2017
The Northland will be under northwest flow aloft through much of the
extended period with high temperatures mostly below normal. There
will be a few opportunities for mainly showers as several shortwaves
move through the region.
A shortwave will move through the region Wednesday night and combine
with low-mid level FGEN to cause a chance for showers during the
evening from the Walker area to the Twin Ports to Hayward and points
south. As those features exit late Wednesday night, high pressure
will nose into the area, bringing dry conditions Thursday and
Thursday night. Mainly dry conditions will continue into Friday as
the high shifts further east. Highs Thursday and Friday will range
from the upper sixties to lower seventies.
A couple more shortwaves will affect the region over the weekend
aiding to knock down the upper ridge with a trough developing over
the region. There will be a chance for showers over the weekend into
early next week with highs Saturday from the upper sixties to lower
seventies warming slightly by Monday.
&&
.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 107 PM CDT Tue Aug 22 2017
Mainly VFR across all sites through the forecast period. There may
be some MVFR cigs with rain showers this afternoon across the
DLH/HIB/INL airports. There could be some early morning fog
Wedensday but conditions should stay VFR through midday Wednesday.
&&
.PRELIMINARY POINT TEMPS/POPS...
DLH 70 49 66 47 / 20 20 20 20
INL 67 44 66 41 / 30 20 10 0
BRD 72 47 69 48 / 0 0 30 20
HYR 70 49 67 44 / 10 10 10 20
ASX 71 50 66 46 / 20 30 10 10
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...Small Craft Advisory until 10 PM CDT this evening for LSZ146-147.
&&
$$
SHORT TERM...JTS
LONG TERM...Melde
AVIATION...Stewart
Area Forecast Discussion
National Weather Service Flagstaff AZ
949 AM MST Tue Aug 22 2017
.SYNOPSIS...Isolated showers and thunderstorms will develop along
the Arizona-Utah border today. An uptick in thunderstorm activity
is forecast across all of northern Arizona Wednesday and
Thursday. For Friday and over the weekend...thunderstorm chances
will decrease.
&&
.UPDATE...Latest radar trends indicate isolated showers rotating
north of a line from Grand Canyon Village to Tuba City to Fort
Defiance. The latest HRRR progs scattered thunderstorms developing
near the AZ/UT border this afternoon. As a result, updated the
forecast to indicate the greatest chances of convection near the
AZ/UT border. Also updated the sky cover based on current
obs/trends. Otherwise, the remaining forecast elements are in good
shape.
&&
.PREV DISCUSSION /241 AM MST/...A low pressure system continued to
spin just off the central California coast during the morning
hours. Showers and thunderstorms across the northwest portion of
Arizona will subside by noon as a drier air mass and a warm layer
aloft spins around the California low and across Arizona. As a
result, expecting mainly isolated shower and thunderstorm
activity for most of today through Thursday.
For Friday and the weekend...The low weakens as high pressure
surges northward across Arizona, Nevada and Utah. The drier air
mass and shorter days will make it tough for much more than
isolated afternoon and evening thunderstorms across much of the
area. The exception will be the White Mountains region of east
central Arizona where moisture will remain more substantial and
storms more numerous.
Early next week...Monsoon moisture will attempt to make a
comeback, pushed northward by an increase in thunderstorm
activity over northwest Mexico. At this time the best chances look
to be from the Mogollon Rim southward. We`ll see.
&&
.AVIATION...For the 18Z package...Expect isolated thunderstorms
after 18z with coverage mostly north along the Arizona and Utah
border, decreasing after 02Z this evening. Heavier storms may
produce IFR/MVFR conditions temporarily. Winds less than 10 kts
outside of showers/storms. Otherwise, VFR expected to prevail.
Aviation discussion not updated for TAF amendments.
&&
.FIRE WEATHER...Expect isolated to scattered thunderstorms today
and Wednesday, favoring the mountainous areas of northern Arizona.
Daytime temperatures will be near average with generally light winds.
Thursday through Saturday...Thunderstorm chances will continue
through Thursday afternoon. A drying trend is forecast Friday
through Sunday.
&&
.FGZ WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
PUBLIC...TM/McCollum
AVIATION...ET
FIRE WEATHER...TM
For Northern Arizona weather information visit
weather.gov/flagstaff
Forecast discussion for routine afternoon forecast issuance
.SYNOPSIS...
Issued at 220 PM CDT Tue Aug 22 2017
Generally quiet late-summer weather into early next week.
Seasonably cool the next couple days, then temperatures close to
normal.
The large scale pattern will complete an amplification cycle the
next couple days as a rather strong upper trough becomes
established from eastern Canada into the lower Great Lakes region.
Jet energy working east across Canada will cause the trough to
begin weakening by late in the week. By early next week, the main
westerlies will recede north into Canada, leaving just a weak
remnant of the trough lingering across the forecast area.
Temperatures will begin the period below normal, then rebound to
near normal levels by the weekend. Rainfall will be limited with
precipitation events consisting of just scattered showers. As
such, amounts for the period are likely to end up below normal.
&&
.SHORT TERM...Tonight and Wednesday
Issued at 220 PM CDT Tue Aug 22 2017
The latest RAP analysis and satellite/radar imagery show upper
troughing settling over the western Great Lakes early this
afternoon. A widespread cu field has developed across the region,
though cu has the most vertical extent over far northwest WI and
northeast MN where the highest capes reside. Some of this more
enhanced cu and even a few showers will move into north-central WI
later this afternoon. As cold air continues to funnel across the
region, forecast concerns revolve around light showers early this
evening, followed by lake effect showers/drizzle late tonight.
Tonight...As a secondary surge of cold air arrives from the
northwest tonight, high res models continue to indicate that
scattered showers will persist over north-central WI through the mid
evening hours. Then attention turns to precip off western Lake
Superior overnight. 1000-850mb flow veers around to the NNW
direction after midnight, which is a good trajectory for showers or
drizzle to move into north-central WI. Increased cloud cover some
late as a result, but 10-15 kts of low level flow should not be
strong enough for these clouds to move into central or east-central
WI. With enough wind to prevent temps from tanking, should see lows
ranging from the mid 40s north to mid 50s south.
Wednesday...Broken cloud cover along with patchy drizzle/showers
will likely linger into the mid-morning hours over northern WI. With
day time heating, however, think mixing will cause these clouds to
scatter by midday. Elsewhere, should see scattered fair weather cu
develop, which will lead to a partly cloudy day for most. Highs
ranging from the low 60s in the far north to mid 70s at Wautoma.
.LONG TERM...Wednesday Night Through Tuesday
Issued at 220 PM CDT Tue Aug 22 2017
At low-levels, a cool, dry Canadian air mass will settle across
the area and linger through the weekend. Some pretty chilly
nights are likely unless clouds move through during the nighttime
hours. The typical cool spots across the north will probably fall
into the 30s Wednesday night and Thursday night, and would not be
surprised if there is some patchy frost. The anticyclone and its
associated air mass will linger across the area for much of the
forecast period, but moderation of the air mass should allow
temperatures to rebound to near seasonal levels by the weekend.
While the dry anticyclone dominates at low-levels, the forecast
area will be at least brushed by some middle and upper level
shortwave energy at times. That will lead to some clouds and
maybe some showers. But given the limited moisture, any rains are
likely to be scattered and light.
Tweaked mins down in the typical cool spots Wednesday night and
Thursday night, but tempered the adjustments some due to uncertainty
about passing clouds. Otherwise, the standard forecast
initialization grids based on a broad blend of model output seemed
reasonable, so no other significant changes were necessary.
&&
.AVIATION...for 18Z TAF Issuance
Issued at 1052 AM CDT Tue Aug 22 2017
Cloud bases continue to rise at midday, and should settle in the
4000-5000 ft range this afternoon. As a weak disturbance moves
southeast, short range guidance indicates that a few showers could
move into north-central WI this evening, though confidence is not
high enough to include in the RHI taf. Otherwise, cool north-
northwest flow off Lake Superior will bring some low clouds and
patchy light showers or drizzle to north central WI late tonight,
but conditions should remain VFR farther south and east. Gusty
northwest winds will diminish after sunset.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS.......Skowronski
SHORT TERM.....MPC
LONG TERM......Skowronski
AVIATION.......MPC
Area Forecast Discussion
National Weather Service Lincoln IL
1218 PM CDT Tue Aug 22 2017
.UPDATE...
Issued at 1035 AM CDT Tue Aug 22 2017
The latest surface map indicates a cold front stretching roughly
just south of the Interstate 72 corridor late this morning. The
band of showers and thunderstorms that brought locally heavy
rainfall to parts of central and east central Illinois early
this morning has shifted into southeast Illinois late this
morning. the last few runs of the RAP and HRRR models continue to
suggest any redevelopment of thunderstorms along the cold front
will occur just to our southeast this afternoon. Based on these
trends will continue to push precip chances out of the central and
east central counties early this afternoon and over southeast
Illinois by late afternoon, and even there, will only hold on to
low chance POPs. RAP forecast soundings indicate clouds will be
slow to clear initially early this afternoon, but as drier air
filters south into the region, we should see the clouds gradually
lift and then dissipate by late afternoon or early this evening.
The front will be southeast of our area by early this evening
with drier air filtering southeast into central Illinois as much
cooler air moves in for later tonight into Wednesday morning.
Under a clear sky and light winds late tonight, look for early
morning lows to drop into the low to mid 50s over our far
northern counties, with upper 50s forecast for areas south of
Interstate 70. Updated forecast should be out by 11 am.
&&
.SHORT TERM...(Today and tonight)
ISSUED AT 241 AM CDT Tue Aug 22 2017
Both 00z model suites and more recent CAMs show a speed up
of the precipitation ending across the forecast area. This seems
reasonable given the progression of the energy moving across
western Missouri this morning. As it interacts with the digging
trough and help to intensify it. Will be ending the precip from
northwest to southeast.
Due to training nature of some of the storms tonight, soil
moisture should be high in some areas. Will have to watch for the
potential for fog tonight. Will leave it out for now and let day
shift analyze precip reports and wind forecasts to determine if
mention is warrented.
.LONG TERM...(Wednesday through Monday)
ISSUED AT 241 AM CDT Tue Aug 22 2017
Cool northwest flow will persist at least through the first part
of the weekend. Several waves will rotate through the trough
during the period, but with limited moisture available the biggest
impacts may be a brief increase in clouds and a reinforcement of
the cool air in place. Temps should be 5-10 degrees below normal.
There are several differences in the way the models are handling
the tropical moisture associated with the remants of Harvey and
its interaction with the longwave trough over the eastern U.S. For
now will keep rain chances low Monday given the uncertainty.
&&
.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1215 PM CDT Tue Aug 22 2017
Cigs will lift to VFR and scatter out this afternoon as much drier
air filters southeast into the forecast area. Based on current
trends with the visible satellite loop, we may see a brief period
of bkn cigs at 2000-3000 feet early this afternoon before the
drier air starts to work on the cig bases after 20z. Most of the
area will see a tempo scattered to broken group early on with a
trend towards a scattered deck by mid to late afternoon. A clear
sky is expected overnight into Wednesday morning with west to
northwest wind of 10 to 15 kts with a few gusts approaching 20 kts
at times this afternoon. The winds will be light northwest tonight
with speeds of 5 kts or less.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Smith
SHORT TERM...Barker
LONG TERM...Barker
AVIATION...Smith
...Previous Extended Marine Forecast Discussion Slightly Modified...
Fri-Sat...Meandering low pressure and lingering tropical moisture
will team to keep plenty of showers and storms in the forecast. Wind
direction and wind speed will be tricky as there is some potential
for a surface low to form over or near the ECFL/NEFL coastal waters.
Seas generally 2-3 ft, perhaps 4 ft well offshore.
&&
.Climate...Potential warm minimum temperature records for 22-Aug-17.
Melbourne...82 which would tie the record from 2007.
Vero Beach..80 which would break the record of 78 set in 1944.
&&
.PRELIMINARY POINT TEMPS/POPS...
DAB 75 92 75 92 / 10 30 30 40
MCO 76 95 76 93 / 10 30 30 60
MLB 78 91 77 91 / 20 60 40 60
VRB 76 90 75 90 / 30 70 50 60
LEE 77 96 78 95 / 10 30 20 40
SFB 76 96 77 95 / 10 30 30 50
ORL 78 96 78 94 / 10 30 30 60
FPR 76 90 76 90 / 40 70 50 60
&&
.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...None.
&&
$$
Sedlock/Pendergrast/Smith
Area Forecast Discussion
National Weather Service Nashville TN
131 PM CDT Tue Aug 22 2017
.DISCUSSION...
A wide band of showers has developed across Middle Tennessee early
this afternoon. Additional activity is occurring farther
upstream, just on the other side of the Ohio River in the vicinity
of a surface boundary that is approaching Middle Tennessee.
Latest HRRR shows the activity persisting throughout the
afternoon, and even increasing late this afternoon and into the
evening as the front pushes into Middle Tennessee. Most of the
cells will diminish by 06Z, with some lingering showers mainly
across eastern and southern Middle Tennessee tomorrow morning
before the front finally exits the mid state. There is a marginal
risk of severe storms this afternoon and evening, but the
potential for severe activity is quite limited. Expect cooler
temperatures beginning tomorrow as post-frontal air filters into
the mid state, and below normal temperatures will persist right
through the end of the forecast period. The remainder of the week
looks to be dry, so we won`t see any appreciable rain chance until
the weekend as deeper moisture drifts up from the south in
advance of a tropical system coming onshore along the western Gulf
of Mexico. At this time, it appears that the tropical system will
have a more direct impact on Middle Tennessee next Thursday and
Friday, and already the GFS and ECMWF are coming into good
agreement over placement and timing.
&&
.AVIATION...
18Z TAF DISCUSSION.
Deteriorating conditions is trend for this period as a front
approaches later today into tonight...and passes overnight.
Showers/storms currently developing expected to become bit more
widespread late afternoon/early evening. Will include vcnty
until mid afternoon...then ramp up chance toward 00z. Not much
precipitation expected overnight but MVFR/IFR cigs/vsbys likely
to form.
&&
.PRELIMINARY POINT TEMPS/POPS...
Nashville 72 84 62 83 61 / 70 10 0 0 0
Clarksville 67 81 58 81 58 / 50 10 0 0 0
Crossville 68 78 57 77 56 / 70 30 10 0 0
Columbia 71 83 61 83 60 / 70 20 0 0 0
Lawrenceburg 70 83 61 82 59 / 70 20 0 0 0
Waverly 69 81 60 81 59 / 50 10 0 0 0
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION......08
AVIATION........07