Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/24/17
Area Forecast Discussion
National Weather Service Bismarck ND
942 PM CDT Tue May 23 2017
.UPDATE...
Issued at 942 PM CDT Tue May 23 2017
Did expand the Frost Advisory into the James River Valley for
tonight. Upper level RAP relative humidity fields through the 01
UTC iteration suggest cirrus will be thinnest across the James
River Valley with light winds in the weakening surface ridge axis.
However, did cancel the advisory for Hettinger, Adams, Stark and
Dunn counties where greater cirrus and increasing return flow
will prevent frost formation.
UPDATE Issued at 634 PM CDT Tue May 23 2017
Little change with this update other than to blend to observed
trends through 23 UTC. Will continue to evaluate guidance through
the evening as an expansion of the Frost Advisory into the James
River Valley tonight may be needed.
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 241 PM CDT Tue May 23 2017
A few highlights in the short term period: A frost advisory for
portions of southwest and south central ND tonight into early
Wednesday morning; Clouds and winds will continue to diminish
over the James River Valley west to the Missouri Valley this
afternoon/evening. The gusty winds from earlier today, near 40 MPH
over south central North Dakota were related to the strong
temperature/pressure differences between the cloud and rain
cooled air southeast and the clearing skies/subsidence to the
west.
For tonight have trended the minimum temperatures down by using
the lowest of all guidance for low temperatures tonight. This
would have worked out well last night as well as temperatures
were 5 to 7 degrees cooler across the southwest than the ensemble
guidance was. Issued the frost advisory for late tonight and early
tomorrow for these adjusted temperatures.
For Wednesday, skies will be mostly sunny through most of the day
until an advancing shortwave and associated cold front move to
eastern Montana. This will bring some late afternoon clouds and a
chance for showers and a few thunderstorms to the far west.
However CAPE is pretty modest so expected fairly widely scattered
non severe thunderstorms. Return flow from the South and warm
advection should warm temperatures into the upper 60s to lower
70s.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 241 PM CDT Tue May 23 2017
The cold front will be the focus for showers and isolated
thunderstorms along a narrow band of instability Wednesday
night. By Thursday the showers will be departing to the east and
cooler temperatures into the 60s to around 70 seam reasonable.
Not getting a lot of cold advection from this shortwave trough
that initially tracks across the southern Prairie Provinces of
Canada. But then the GFS dumbbells this upper low across the
Northern Plains through the weekend keeping an extended period of
scattered showers and cool temperatures through Memorial day
weekend, especially Sunday. The ECMWF is a bit warmer and dryer
through Sunday then brings a cold front through Monday. So with
this disagreement between global models will keep the Superblend
guidance for the weekend which gives moderate chances of showers
and slightly cooler temperatures through the Memorial Day weekend.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 942 PM CDT Tue May 23 2017
VFR conditions are forecast across western and central North
Dakota for the 00 UTC TAF cycle. Strong southeast winds will
develop on Wednesday with gusts of 30-35kts expected for most
areas. Low level wind shear is possible across western North
Dakota early Wednesday morning with strong winds within a low
level inversion.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
Frost Advisory from 3 AM CDT /2 AM MDT/ to 9 AM CDT /8 AM MDT/
Wednesday for NDZ019>023-025-034>037-042-045>048-050-051.
&&
$$
UPDATE...AYD
SHORT TERM...WAA
LONG TERM...WAA
AVIATION...AYD
Area Forecast Discussion
National Weather Service State College PA
1120 PM EDT Tue May 23 2017
.SYNOPSIS...
Weak system passing to our south today producing mainly clouds.
A very deep upper low will bring clouds across the region
Wednesday with rain developing overnight and into Thursday. This
deep low will produce cooler showery weather through Friday. As
this low lifts out Friday into Saturday a weak upper-level ridge
should provide several relatively nice days to start the
Memorial Day weekend. Alas another low may approach the region
on Memorial Day.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Showers continue to straddle the Mason Dixon line late this
evening...with BKN-OVC skies covering all of central PA.
HRRR has been consistent in bringing a small batch of showers
northward into the West Central and Central Mountains later
tonight, and will carry slight chance pops for this through the
pre dawn hours. Shower area becomes more fractured after
midnight and latest HRRR actually favors showers reaching the
Northwest mountains...but am not convinced of this just yet. Any
rain that does fall will be light...with only areas near the
Mason Dixon line potentially receiving up to a tenth of an inch.
Expect patchy fog across the southern half of PA as well.
Overnight lows will range generally through the 50s.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
Tomorrow we should be mostly between systems. The clouds and
moisture from the wave to our southeast should be pulling away
overnight. And the clouds and rain from the deep 500 hPa low
will be heading our way from the west-southwest.
Most areas should have a pretty nice day, but once again on the
cloudier side of things. Kept POPS in the chance range in
southwest before 18 UTC and brought them up higher and into
central PA by 00 UTC.
Sometime from 2100 UTC Wed to about 0300 UTC it`s going to get
wet. But highest probability of rainfall in current guidance
will likely be on Thursday. New guidance might change this.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
As upper low drops into the TN Valley Wed night, surface low
develops over the Ohio Valley with a warm front extending
eastward across the mid atlantic states. Initial question will
be timing of onset of precip over CWA. Precip will be working
across W PA by early eve and will spread eastward as flow turns
from the SE around to the S, overspreading all of central PA by
the overnight hours. System slides through Thu into Thu night,
with a widespread rainfall around 0.75 inch.
On Friday, cool cyclonic flow on backside of departing cyclone
will maintain risk for showers. A lower-amplitude mid level flow
pattern will develop into the weekend with some ridging likely
at 500mb. Uncertainty regarding location and timing of shortwave
impulses rounding the ridge and effect of prior upstream
convection leaves plenty of question marks for Saturday - but
there is more agreement in area of max POPs over S OH/into WV
and SW PA in the afternoon.
NBM/ECE blend yielded the highest POPs for Sunday across
Central PA associated with cold front moving south/eastward
across the Great Lakes/Appalachians. A severe risk may accompany
the cold front but still to early for details. The large scale
pattern evolves into a broadly cyclonic regime into early next
week around an upper low between the Great Lakes and Hudson Bay.
This should keep the pattern unsettled with continued threat
for showers/Tstorms through Tuesday.
&&
.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
Most of the flying area is under a blanket of high clouds. Some
MVFR has crept into MDT and this lowering ceiling trend over
southern areas as the area of rain slowly overspreads the
region.
Expect the mainly light rain to move into about the southern
half of the forecast area during the remainder of the overnight
and early Wednesday with MVFR/IFR conditions developing.
Northern areas will see just spotty light showers and widespread
sub VFR conditions are not expected.
Conditions will improve slowly Wednesday morning with most areas
improving to VFR by mid day. MVFR could hang tough over the
Laurels.
Clouds will increase west to east as another system approaches
with rain and reduced conditions overnight Wednesday into
Thursday.
.OUTLOOK...
Thu...Rain/low cigs likely through at least midday.
Fri...Showers/MVFR cigs NW. Mainly VFR SE.
Sat...No sig wx expected.
Sun...Reduced conditions with scattered showers.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Grumm
NEAR TERM...Grumm/DeVoir
SHORT TERM...Grumm
LONG TERM...RXR/Steinbugl
AVIATION...La Corte
Area Forecast Discussion
National Weather Service Green Bay WI
1042 PM CDT Tue May 23 2017
Updated aviation portion for 06Z TAF issuance
.UPDATE...
Issued at 649 PM CDT Tue May 23 2017
Area of concern this evening focusing on Calumet county. Surface
frontal boundary and surface low was located over southern
Wisconsin, however radar shows a convergent area north of the
surface boundary extending from Dodge County to Calumet County and
northern Manitowoc County. This convergent region was pivoting
with the bands of rain over MTW County lifting north. However
parts of the southern two thirds of Calumet County may pick up 1
to 2 inches of rain this evening if this band maintains. Will
consider an urban small stream advisory for this area if this
convergent band holds over the area this evening.
&&
.SHORT TERM...Tonight and Wednesday
Issued at 240 PM CDT Tue May 23 2017
The latest rap analysis and satellite/radar imagery show surface low
pressure centered near the Dells, and associated warm front
extending east across east-central WI. Instability has developed
south of the warm front, leading to thunderstorms developing along
and just north of the boundary. Some of these storms may make it
into areas from Waushara to Manitowoc this afternoon, but
convergence does weaken by early this evening, so think the threat
of storms will end by this time. Looking elsewhere, deeper moisture
is wrapping around the upper circulation across eastern WI, which
should keep the chance of showers highest over eastern parts of the
state for the afternoon. As additional showers move north from
northern Illinois, precip trends are the main forecast concern.
Tonight...Center of the upper low will drift south across Iowa and
Missouri, but the upper level trough axis will extend north across
Wisconsin through the night. As the low moves south, think precip
chances will come to an end over north-central WI by late evening.
Eastern WI will not be as lucky, as deeper moisture will rotate
around the trough and across eastern WI from about mid-evening
through the overnight hours. Some of these showers will likely
rotate into central WI as well, but coverage should not be as high
as further east. With ample cloud cover, lows will range from the
low 40s north to upper 40s south.
Wednesday...The upper low will continue to move to the southeast
across the mid-Mississippi Valley. Meanwhile, corridor of deeper
moisture will continue to impact eastern WI into at least early
afternoon with occasional showers, before diminishing. Have
increased precip potential in this area considerably. Otherwise,
skies will remain mostly cloudy and breezy with a stiff northeast
wind. Cool temps rising into the upper 50s to lower 60s.
.LONG TERM...Wednesday Night Through Tuesday
Issued at 240 PM CDT Tue May 23 2017
Expecting dry weather for the beginning of the period, then
uncertain precipitation chances for the Memorial day weekend.
Near normal temperatures are anticipated through the period.
A weak ridge of high pressure at the surface and aloft should
bring mainly dry conditions late Wednesday night through
Thursday evening, though an isolated diurnal shower cannot
be ruled out Thursday afternoon. Weak WAA will bring a small
chance of showers back to the forecast area late Thursday night
into Friday.
Models offer widely varying solutions for the Memorial Day
weekend. Saturday is looking like the driest and warmest day
of the weekend, with only a weak cold front moving through the
region. The GFS drops an upper low into the western Great Lakes
on Sunday and Monday, and also brings a swath of a rain to the
southeast part of the forecast area as low pressure lifts through
the Lake Michigan region Saturday night into Sunday. Meanwhile,
the ECMWF keeps the main upper low to our north, with a series of
short-waves and frontal passages bringing the best precipitation
chances to northern WI. Given the poor run to run consistency of
the GFS, would lean toward the ECMWF for now. However, overall
confidence in the precipitation chances over the holiday weekend
are low.
&&
.AVIATION...for 06Z TAF Issuance
Issued at 1040 PM CDT Tue May 23 2017
An upper level low system with a surface low will
track into the Ohio Valley region overnight into Wednesday.
Showers with patchy IFR/mvfr conditions will linger over eastern
Wisconsin tonight into Wednesday morning and then showers will
taper off while conditions gradually improve later Wednesday.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE.........TDH
SHORT TERM.....MPC
LONG TERM......Kieckbusch
AVIATION.......TDH
Area Forecast Discussion
National Weather Service Houston/Galveston TX
1044 PM CDT Tue May 23 2017
.UPDATE...
Cleared near shore waters from Severe Thunderstorm Watch 259 as
the showers and thunderstorms associated with the surface front
have diminished. Also lowered PoPs to account for radar imagery
which is picking up on the line of showers with isolated thunder,
moving in from the north associated with the 850 mb front.
Hathaway
&&
.PREV DISCUSSION... /ISSUED 926 PM CDT Tue May 23 2017/
UPDATE...
Main updates to the forecast tonight have been clearing counties
from Severe Thunderstorm Watch 259. The surface cold front and
associated thunderstorm activity continue to push off the Upper
Texas coast tonight, taking the threat for severe weather with it.
The KHGX radar is showing a secondary line of showers developing
approximately 100 miles to the north in the vicinity of the 850 MB
front. Despite a uniform wind direction at this level, there is
sufficient speed convergence along this feature (30 knot winds
flowing into 10 knot winds) to result in isolated to scattered
showers. The atmosphere as destabilized significantly since this
evening`s storms moved through and severe weather is not expected,
but cannot rule out a rumble of thunder. Otherwise, remainder of
forecast remains on track with dry conditions expected after
midnight and clearing skies allowing overnight temperatures to
fall to the mid 50s to mid 60s... much below normal for this time
in May.
Huffman
PREV DISCUSSION... /ISSUED 644 PM CDT Tue May 23 2017/
AVIATION...
Storms occurring ahead of the cold front will be moving across the
terminals from 00Z at KUTS to about 04-05Z at KGLS. A strong
thunderstorm should be east of KCLL by 00Z; however, more showers
were developing to the west of the site. There is a slight
possibility of a strong or severe storm with gusts in excess of
50 knots and large hail making its way through the sites between
KCXO and KHOU between 00Z and 02Z.
Expect the storms to be off the coast by 06Z. VFR conditions are
then expected. Breezy winds are expected to then develop after 15Z
Wednesday.
40
PREV DISCUSSION... /ISSUED 438 PM CDT Tue May 23 2017/
DISCUSSION...
Surface analysis as of 1 PM CDT showed an approaching cold front
stretching from Del Rio to Waco towards Shreveport, with a weak
prefrontal wind shift entering portions of the Brazos Valley.
Regional radar mosaic this afternoon shows a few cells developing
along and behind the front as it continues to push towards the
southeast. With RAP guidance instability increasing ahead of the
approaching boundary and lift overspreading the region from a
passing 90 knot upper jet, expect the severe weather threat to
increase over the next few hours for Southeast Texas as scattered
thunderstorms continue to develop along the front. Expect the
front to clear the Brazos Valley late this afternoon, reaching the
Houston metro mid-evening, and clearing the coast around midnight
tonight. Steep mid-level lapse rates will result in a large hail
and damaging wind threat (especially if any storms bow out) as the
front progresses southward.
A few showers may linger behind the front tonight before
dissipating as drier air moves into the region, with clearing
clouds and cold air advection behind the front resulting in
cool overnight low temperatures in the mid 50s to mid 60s. Dry
weather will continue through the rest of the week with high
temperatures gradually warming into into the low 90s by Friday as
shortwave ridging translates across the region. Northerly winds
will gradually swing around to the south by Thursday as surface
high pressure slides off to the east, allowing moisture to
gradually return by the beginning of the weekend. A cold front
looks to slide into Texas by the beginning of the weekend and
stall at the beginning of next week as an upper low reaches the
Great Lakes. Will have to keep an eye on the Monday/Tuesday
portion of the forecast next week as disturbances overriding this
stalled boundary look to result in a very wet period for the
region.
Huffman
AVIATION...
A cold front will push off the coast tonight with strengthening
northerly winds and building seas in its wake (some thunderstorms
developing along and ahead of the front could become strong or
severe as they move off the coast this evening). Onshore winds
will return early Thursday and quickly strengthen during the day.
Elevated winds and seas can be expected from the end of the week
on through the upcoming Memorial Day weekend. Caution flags will
probably be needed, and advisories will be possible. 42
CLIMATE...
Low temperatures Wednesday morning will be well-below normal for
late May and observations across parts of the Brazos Valley and
Piney Woods regions may approach or reach record low temperatures
for May 24. A listing of record low temperatures for May 24 for
the first order climate sites are provided below.
LOCATION RECORD LOW YEAR
City of Houston 54 1892
Houston Hobby 57 1940
College Station 55 1913
Galveston 62 1940
Huffman
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 56 82 60 90 73 / 50 10 0 0 10
Houston (IAH) 59 83 64 89 74 / 60 10 0 0 0
Galveston (GLS) 63 81 73 84 79 / 40 10 0 0 0
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION until 10 AM CDT Wednesday
for the following zones: Coastal waters from Freeport to
the Matagorda Ship Channel out 20 NM...Coastal waters from
High Island to Freeport out 20 NM...Waters from Freeport to
the Matagorda Ship Channel from 20 to 60 NM...Waters from
High Island to Freeport from 20 to 60 NM.
&&
$$
Discussion...08
Area Forecast Discussion
National Weather Service Huntsville AL
936 PM CDT Tue May 23 2017
.NEAR TERM...(Tonight)
Issued at 920 PM CDT Tue May 23 2017
One batch of showers and storms has finally moved off to the east
into GA. However, another round will be moving across the MS River in
the next hour or so. These showers and storms are forming along a
cold front that extends S/SE out of a low pressure system over the
Great Lakes into the ArkLaMiss. Latest radar and surface analysis is
showing a secondary low pressure system forming over NE TX along the
front. This feature is forecast to lift NE into northern MS and then
into central TN tonight through Wednesday morning.
Last few runs of the HRRR seem to have a good handle on the movement
although believe they are a bit on the slower side in the progression
of showers across the area. Initial forecast had PoPs increasing
well after 06z tonight but have shifted those to around midnight with
60-70 PoPs going for much of the overnight period. Forecast soundings
and model guidance all indicate some limited elevated instability
(200-500 J/kg) and 30-40kts of shear. Which is enough to continue
thunderstorm wording for tonight. Main hazards would be heavy
rainfall and wind gusts of 30-40 mph. Lows in the lower 60s still
seem reasonable based on temps upstream and latest hires guidance.
.SHORT TERM...(Wednesday Night through Thursday Night)
Issued at 249 PM CDT Tue May 23 2017
The upper low pulls away Wednesday night which should end precip
completely from southwest to northeast. Thursday should be a fine
weather day with a surface ridge shifting east with corresponding
confluent northwesterly flow at 500 mb. Highs should bounce back into
the lower to middle 70s, followed by lows in the lower to middle 50s
by Friday morning. We will hold off on patchy fog, but it may be
something for consideration if the winds are able to drop off.
.LONG TERM...(Friday through Monday Night)
Issued at 249 PM CDT Tue May 23 2017
Upper level ridging and subsidence behind the departed front become
established over the Tennessee Valley into the northeastern Gulf of
Mexico on Thursday night into Friday morning. This continues into
Friday afternoon, as the storm system over Oklahoma edges east only
slightly, mainly due to the upper level ridging to its east over the
Tennessee Valley. Although models hint at some energy moving through
almost zonal flow over northern Tennessee and Kentucky, the
atmosphere should still be too dry for even any isolated shower/storm
activity. Could see high cloudiness move into the area in response
to this upper level forcing, but most of it will be in Southern
Middle Tennessee.
Models continue to show very moist conditions returning northward
quickly Friday night into Saturday, as low level winds become more
southerly. However, synoptic models diverge concerning how far south
a warm front extending from the storms system over Oklahoma sets up.
GFS is much further north, while ECMWF is much further south by late
Saturday afternoon into Saturday evening. Thus, if GFS is right,
timing of precipitation potential may be later than the current
forecast indicates and hold off until late Saturday night. At this
point used a blend of models. This pushes scattered showers/storms
into Southern Middle Tennessee and northern Alabama Friday night
into Saturday. Warm temperatures aloft should keep wet-bulb heights
fairly high. Models show decent bulk shear values between 40 and 50
knots Friday night into Saturday, but the lack of forcing should
limit coverage to mainly near and north of the Tennessee River.
However, a few storms could be strong during this period producing
gusty winds around 50 mph and frequent lightning. Breezy conditions
with winds of 10-15 mph with gusts up to 25 mph should return on
Saturday. Higher elevations may see wind gusts a bit higher,
especially Saturday night.
Expect more widespread coverage of showers and thunderstorms to occur
Saturday night into Sunday (as forcing associated with the surface
low moving northeast into the western Great Lakes approaches and then
moves into Alabama from Mississippi). Most synoptic models are not
too different concerning the timing of this frontal boundary and have
the actual front approaching northwestern Alabama Sunday afternoon.
PWATS increase to between 1.6 and 1.8 inches and remain in this
range most of this period. This may lead to flash flooding/river
flooding issues during this period as well, given the slow movement
eastward of the front. Plenty of surface based and elevated CAPE is
forecast by models Saturday night into Sunday, especially on Sunday
(2000-3500 J/KG). 0-6 km bulk shear values will be between 40 and 55
knots as well. Low level helicity is forecast to increase Saturday
night to around 200 to 300 m2/s2 (especially west of I-65). This
helicity quickly decreases on Sunday. Couldn`t rule out a low
potential for a brief, weak tornado spinup on Saturday night before
helicity decreases. However, we are more confident that we will see
strong thunderstorms producing wind gusts around 50 mph, heavy
rainfall, and frequent lightning Saturday night through Sunday. Wet-
bulb heights remain fairly high, but lower to around 10,000 feet.
GFS more quickly moves the front south of the Tennessee River, but
ECMWF keeps the back edge of precipitation further north on Monday.
For now, went with a blend of models. Kept 30 to 40 percent chance of
showers and thunderstorms in the forecast to cover any convection
along and just behind the front. Kept mostly cloudy conditions in
place most of Monday as the upper low and associated moisture will be
slow to exit the area. By Monday night, a few showers may linger,
but this may be overdone due to blending of model differences.
Either way, cooler and drier weather should return with lows in the
lower 60s and highs around 80s degrees expected.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 620 PM CDT Tue May 23 2017
The storms have moved off to the east and we are left with VFR
conditions through about 06Z tonight. A cold front and associated
showers and thunderstorms will move across the area tonight. MVFR
cigs and vis accompany the storms tonight. Showers may continue past
12Z Wednesday morning but most of the activity will be off to the
east. MVFR cigs continue through the morning with winds increasing
out of the NW. Gusts of 15kts are possible in the afternoon.
&&
.HUN WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
TN...NONE.
&&
$$
NEAR TERM...Stumpf
SHORT TERM...17
LONG TERM...KTW
AVIATION...Stumpf
For more information please visit our website
at weather.gov/huntsville.
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1105 PM EDT Tue May 23 2017
.UPDATE...
Issued at 1055 PM EDT TUE MAY 23 2017
Hourly pops have been updated based on recent radar trends.
Showers and even a rumble of thunder in the far southeast has
occurred in the last hour as a mid level disturbance works through
the area. The current round of showers should weaken and shift out
of the area over the next couple of hours. However, another
disturbance should bring another round of showers and perhaps a
thunderstorm encroaching on the area around dawn.
UPDATE Issued at 835 PM EDT TUE MAY 23 2017
Some late afternoon heating and a mid level disturbance have
combined to bring some showers and thunderstorms to parts of
Central KY and parts of Middle TN and the Cumberland Plateau of
TN. Much of these have experienced a downward trend in intensity
over the past hour or so with the exception of the convection in
the Bluegrass Region of KY while showers persist across much of
southeast KY. Thunder chances were added for the evening with the
upstream thunder detected. Also, dewpoint depressions across much
of the area are just a few degrees. With low level moisture
lingering and some cooling in between the current shortwave and
the next to approach late tonight and on Wednesday at least some
patchy fog will be experienced possibly both on the ridges and int
the valleys and this has been included. Otherwise, no substantial
changes were needed at this time.
&&
.SHORT TERM...(This evening through Wednesday night)
Issued at 500 PM EDT TUE MAY 23 2017
20z sfc analysis shows a broad area of low pressure over the
middle of the Tennessee Valley encompassing Kentucky. This has
brought showers and sprinkles to eastern Kentucky as well as
plenty of clouds. The rain has also kept temperatures in check and
on the cool side through much of the JKL CWA with readings
currently in the low 70s northwest and southwest where the clouds
were thinnest to the mid 60s in the rain further east. Dewpoints
are generally in the upper 50s to lower 60s while the winds are
light and variable.
The models are in good agreement aloft through the short term
portion of the forecast. They all depict a deep and cut off
closed low digging into the Deep South through Thursday morning
along with ample energy swirling around. The core will roll down
the backside of this larger trough and generally target locations
to the south of Kentucky on Wednesday into Wednesday night. The
good model agreement lends support to a blended model solution
along with the use of the high res HRRR through the near term.
Sensible weather will feature scattered showers departing to the
northeast this evening - with a stray thunderstorm possible. This
will be followed by a lull in the activity through midnight for
most locations under cloudy skies before the next surge in
moisture moves in late tonight with showers and thunderstorms
increasingly possible toward dawn. The thick clouds should keep
most of the fog at bay tonight, but for places that saw the rain
late this afternoon and into the evening - should the clouds thin
enough - patchy fog will be possible and will need to be
monitored. Showers and thunderstorms will then sweep over all of
eastern Kentucky on Wednesday with some gusty winds and a window
of heavier rain possible should they manage to be more organized -
perhaps helped from a mid level wave swinging through around
midday. Have highlighted this time frame in the grids for the
best shot at thunder, as well. Later in the day the thunder
chances fade out from west to east as the main sfc low lifts past
to the east. Lighter shower will linger, though, into the night.
The CONSShort and ShortBlend were used as a starting point for
the grids` with only minor adjustments to temps through the
period. As for PoPs, made some significant adjustments to them to
better represent the spatial and timing aspects of the rain
shield moving into East Kentucky from late tonight through
Wednesday afternoon.
.LONG TERM...(Thursday through Tuesday)
Issued at 400 PM EDT TUE MAY 23 2017
An upper level low will be centered over Kentucky to start out the
period Thursday morning, shifting northeast throughout the day and
into Thursday night, with rising heights expected across the
Commonwealth. Ridging will take hold Friday, however will be
dampened as several shortwaves move through the pattern and affect
the region over the next couple of days. By Saturday, another upper
level low will drop south from central Canada, allowing for longwave
troughing to develop across the central U.S. While timing on this
system is still somewhat unresolved between the models, as is the
intensity of the trough, much of the state can expect some type of
height falls and destabilization to occur to round out the weekend
and start the beginning of the workweek. Models actually come back
into better agreement by the very end of the extended period, with
the axis of the trough nearing the state Tuesday, and traversing the
state into the day Wednesday.
At the surface, the presence of a surface low pressure system just
north of the CWA (in conjunction with the upper level low) will
result in precip chances throughout the day Thursday. This precip
will pull northeast of the region into Friday morning as the surface
low exits in this direction. However, given our location on the
backside of the cold front, latest forecast soundings aren`t
supporting much in the way of instability, so chose to keep out
mention of thunder Thursday. A brief area of high pressure will move
into place with the building heights, keeping us mostly dry Friday.
However, incoming shortwaves that will ride along this pattern will
bring the return of unsettled weather and shower/thunderstorm
chances by Friday night, continuing through Saturday and increasing
in intensity and coverage by Saturday night into Sunday as a surface
low moves NE towards the state and a cold front drags eastward. This
cold front will cross eastern KY Sunday night into Monday, with
another brief area of high pressure moving in behind during the day
Monday. Yet another cold front will near the state Tuesday,
attached to a stronger surface low to our north (in conjunction
with the second upper level low referenced above). This will bring
yet another round of precip (showers and thunderstorms) to the
region through the day Tuesday.
Temperatures should start out below normal during the day Thursday
behind the departing cold front, with highs in the mid 60s. stronger
S to SW flow will take place by Friday, bumping temps into the mid
and upper 70s Friday afternoon, and into the upper 70s and low 80s
on Saturday and Sunday afternoon. Despite a cold front moving
through on Sunday night/Monday morning, temps will only be slightly
(a couple degrees) cooler on Monday and Tuesday than the weekend
thanks to the quick return of SW flow behind the frontal passage.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
ISSUED AT 820 PM EDT TUE MAY 23 2017
In advance of a shortwave, areas of showers and thunderstorms are
moving across East KY this evening with the strongest activity
headed toward the far northwest counties and could affect SYM with
MVFR or IFR for a time. Additional showers could affect LOZ and
SME as well. This activity should diminish 3Z to 5Z before showers
increase again 10Z to 16Z. The low levels remain moist so outside
of showers some MVFR fog should develop and could affect all of
the TAF ties. This next round should lead to saturation at all
levels again and cigs should fall to MVFR if not IFR at times as
shra and some tsra move in from the southwest with the next
shortwave. Winds should average less than 10KT through the period.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...JP
SHORT TERM...GREIF
LONG TERM...JMW
AVIATION...JP
Area Forecast Discussion...UPDATED
National Weather Service Chicago/Romeoville, IL
825 PM CDT Tue May 23 2017
.UPDATE...
825 PM CDT
The going forecast of scattered/periods of showers tonight remains
on track. There was a slight diminishing in coverage since 7 pm
owing more to the passing of a shortwave than a true diurnal
downtick. While some diurnal dissipation should be the case
through the evening, variation in coverage is likely with
continued cold mid-level air and subtle short wave impulses ahead
of the main low center. The 00Z DVN and ILX soundings indicated
200-400 J/kg of MUCAPE and 25-40 kt of deep layer shear that will
continue to be tapped for showers with some organization and
spotty moderate to heavy rates. As an example, Pontiac Airport
had 1/2SM visibility around 7 pm with a shower. The potential for
funnel clouds likely has ended as surface winds are generally
light and variable with little for low-level convergence, and any
lightning should be few and far between.
Given the rain and low T/Td spreads, fog is a possibility. There
is quite a bit of existing cloud cover that would hint at low
stratus being more dominant than fog, but confidence is low.
Certainly at least shallow patchy fog is a good bet in some
locations, and would be likely and even dense in any areas that
have a thinning in cloud cover (presently not favored for most of
the CWA).
MTF
&&
.SHORT TERM...
240 PM CDT
Through Wednesday...
Deep low pressure will continue to sink south from the corn belt
to the lower Mississippi valley Thursday. The first in a series of
waves ahead of the low will shift northeast through the flying
area this afternoon. Expect an increase in shower coverage and
intensity over the coming hours with the enhanced lift from this
wave, with some moderate showers due to a narrow moisture plume
precipitable water values in excess of 1 inch There is a small
pocket of instability across north Central Illinois into adjacent
Wisconsin where the best near term chances for embedded
thunderstorms exists. With the upper low shifting farther east,
cold temperatures aloft will allow some of this weak instability
to shift over northeast Illinois and northwest Indiana. This
combined with the vort max still warrants a low chance thunder
mention. RAP forecast of non-supercell tornado threat are still
low but low level cape does exist in very localized pockets near
the cold frontal boundary where low level vorticity is enhanced,
and with some limited clearing there is still a limited severe
weather concern for gusty winds as the vort max encounters the
front this afternoon.
As the low sinks south tonight into Wednesday, Expect continued
waves of showers as additional energy spreads northward ahead of
the low, with coverage likely decreasing though possibly becoming
more narrowly focused on eastern half of the area. There could be
a modest rainfall axis that will setup tomorrow, with the I-55
eastward corridor still favored, but still challenging to pinpoint
at this time. A low thunder chance exists across east Central IL
and northwest IN as well. Elsewhere just expect occasional showers
and cool cloudy conditions.
KMD
&&
.LONG TERM...
240 PM CDT
Wednesday night through Tuesday...
Looking ahead through the extended part of the forecast, there are
not many periods without a mention of rain chances. We transition
away from one upper low late this week but into another this
weekend, with only weak ridging in between. However, despite the
frequent chances for rainfall, it does not appear that each day will
be a washout. In general the showers should be to some extent
diurnally driven under a cyclonic upper level circulation, which
means at least the early part of most days could be favorable for
outdoor activity.
The most likely period for a break in activity appears to be
Thursday afternoon into the early part of Friday as the first system
moves out and cooler, drier air moves in with northerly surface
flow.
Warmer and more humid air returns for Friday and Saturday. The
biggest uncertainty for this forecast period comes late Friday and
into the weekend, with the deterministic GFS and ECMWF in poor
agreement with the timing of an upper wave and surface low pressure
system moving through the southern Great Lakes. Presently the much
faster ECM...as well as the GEM...brings this system through late
Friday and leaves behind just some light activity for Saturday. The
GFS is about a day slower and shows widespread rainfall Saturday
afternoon and evening. Both have a stationary front extending east
from a larger center of low pressure across Oklahoma early Friday.
They both also depict a wave forming along the front as the one that
pushes through the local area. Given the proximity of the boundary
and the uncertainty with the movement of the surface wave, will
continue to carry increasing precip chances late Friday, especially
south, and again Saturday afternoon and evening for a larger portion
of the area.
Models are in somewhat better agreement in depicting another break
in the weather early Sunday, then a large upper low becoming parked
over the Great Lakes from late in the weekend through at least
midweek. This would support ongoing widespread chances of rainfall,
especially during periods of afternoon heating.
Lenning
&&
.AVIATION...
For the 00Z TAFs...
The main concerns are precipitation trends, winds and CIG/VSBY
trends. A slow moving upper level low pressure will continue to
bring waves of showers at least into Wednesday morning which will
be capable of reduced visibility. The more frequent or prevailing
rain/shower activity should on the large scale focus over the
eastern terminals, with isolated to at times scattered showers
near RFD. The wind field is quite light with a light pressure
gradient but as weak low pressure organizes south of area tonight,
tendency should be for gradually increasing northeast winds. By
mid-day Wednesday and likely through Wednesday evening, the
position of stronger low pressure off to the east will support
gusty north-northeast winds with gust speeds forecast of 18-20 kt
and potential for up to 25 kt at eastern terminals.
Regarding CIG trends, the most widespread low clouds are over
Wisconsin from MKE and to the north and northwest of there. Much
of the guidance, but not all, brings these low clouds southward
tonight with time and then lingers it into Wednesday. Am concerned
that this a bit overdone, so limited the duration of IFR in the
TAFs, leaning on probabilistic ensemble guidance for trend toward
improvement by the mid-late morning through the afternoon.
Confidence is low- medium with CIG trends overall. If the low
clouds do scatter as anticipated, some guidance hints at them
spreading back southwest Wednesday evening. The lighter wind and
moist regime overnight into Wednesday morning may support VSBY
reductions in BR outside of shower activity.
Castro
&&
.MARINE...
309 PM CDT
Low pressure dropping from Wisconsin into Indiana tonight and then
moving to Ohio Wednesday evening will support northeast winds
across the lake through Thursday night. Winds are lighter and more
variable Friday and Saturday under the influence of a ridge of
weak high pressure moving over the lake.
Lenning
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.
&&
$$
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Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
541 PM CDT Tue May 23 2017
.SHORT TERM... (Through Late Wednesday Afternoon)
Issued at 309 PM CDT Tue May 23 2017
Showers and isolated thunderstorms are currently moving east across
the area along and behind a cold front. This initial wave of showers
will shift east into south central and southwest Illinois as well as
southeast Missouri. This is where the RAP is showing low level
moisture convergence becoming concentrated from early evening until
after midnight underneath mid-level ascent ahead of a shortwave
trough coming around the south side of the the upper low. The
shortwave trough will move off to the southeast by early tomorrow
before the main upper low sinks south into Missouri during the day
tomorrow. This will bring scattered showers and thunderstorms to
the area under the cold pool of the upper low during the day.
Temperatures will be cooler tonight and tomorrow behind the front.
Highs will be much below normal tomorrow underneath the upper low
with 850mb temperatures only around +5C resulting in highs only in
the mid 60s.
Britt
.LONG TERM... (Wednesday Night through Next Tuesday)
Issued at 309 PM CDT Tue May 23 2017
The upper level flow will undergo significant transition during the
period from Wednesday night through early next week. A deep trof
will be centered over eastern portions of the MS Valley with an
upper low in the vicinity of southeast MO at the beginning of this
time frame. Cyclonic flow will be present across the region
attendant with the departing cyclone and residual/lingering
diurnally driven showers will be possible near and east of the MS
River on Wednesday evening. Low level cyclonic flow will diminish
overnight as the upper trof progresses eastward into the OH/TN
Valley Region. Thursday looks to be the tranquil and pick-day of the
week. The upper level trof will continue to depart through the
eastern U.S. with rising heights aloft in the wake of the trof and
ahead of a deepening long wave trof in the western U.S.. Weak high
pressure will dominate at the surface with low-level WAA getting
underway above the PBL.
An active and stormy weather pattern will take hold late Thursday
night through Saturday night. Continued progression of the upper
air pattern and evolution of the upstream broad longwave trof will
result in active west-southwest flow. A migratory short wave
within this flow will move across the area late Thursday night
through early Friday morning. An increasing southwesterly LLJ will
result in pronounced low level WAA and moisture return, and
elevated instability due to these advective processes and steep
mid level lapse rates. The primary focus for showes and storms on
Thursday night will be across central and northeast MO expanding
to the remainder of the CWA on Friday morning. A cold front will
then settle into the region late Friday becoming quasi-stationary
late Friday night into early Saturday. The environment during this
time frame remains quite supportive of deep convection with weak-
moderate instability due to a large expanse of steep mid level
lapse rates atop a warm moist low level air mass within a
persistent low level WAA regime.
There are some model differences with the evolution of the front
Saturday into Saturday night with the new ECMWF a bit more
progressive, and faster moving the cold front out of the area by
daybreak Saturday. Alternatively the consistent GFS and GEFS mean
is suggesting the potential for a very volatile period from
Saturday afternoon into Saturday Night. In this scenario a
deepening surface low would translate northeastward along the cold
front which would advance southeast on Saturday night, and the
warm sector will be quite favorable for organized severe weather
characterized by strong instability and strong deep layer shear.
Cooler weather would dominate in the wake of the front Sunday
through the Memorial Day and thru the early part of next week.
Several disturbances in the northwest flow aloft will bring
reinforcing surges of cooler air, as well as the potential for a
few showers and thunderstorms. The greatest threat of any
additional precipitation should be across northeast MO into west
central IL.
Glass
&&
.AVIATION... (For the 00z TAFs through 00z Wednesday Evening)
Issued at 517 PM CDT Tue May 23 2017
Upper level low over IA will drop southeastward through eastern
MO on Wednesday. It appears that much of the scattered shower
activity, now mainly in the St Louis metro area will dissipate
this evening with the loss of daytime heating, although could not
rule out isolated light showers through the overnight hours.
Scattered showers and a few storms should redevelop over the area
Wednesday afternoon. For now will likely just include VCSH in the
St Louis metro area tafs early this evening, then include VCSH in
all the tafs Wednesday afternoon. Should have mainly VFR cigs
through the period, but possibly dropping into the MVFR catagory
early Wednesday morning with plenty of low level moisture across
the area. Northwesterly surface winds will continue through the
period with surface troffing across the OH and TN Valley regions
and surface ridging over the Plains.
SPECIFICS FOR KSTL: Upper level low over IA will drop southeastward
through eastern MO on Wednesday. It appears that much of the
scattered shower activity, now mainly in the St Louis metro area
will dissipate this evening with the loss of daytime heating,
although could not rule out isolated light showers through the
overnight hours. Scattered showers and a few storms should
redevelop over the area Wednesday afternoon. For now will likely
just include VCSH in the STL taf early this evening, then include
VCSH again Wednesday afternoon. Should have mainly VFR cigs
through the period, but possibly dropping into the MVFR catagory
early Wednesday morning with plenty of low level moisture across
the area. Northwesterly surface winds will continue through the
period with surface troffing across the OH and TN Valley regions
and surface ridging over the Plains.
GKS
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&
$$
WFO LSX
Area Forecast Discussion
National Weather Service Marquette MI
652 PM EDT Tue May 23 2017
.SHORT TERM...(This evening through Wednesday)
Issued at 322 PM EDT TUE MAY 23 2017
12Z raobs/latest wv imagery and RAP analysis show a closed upr lo
sinking slowly swd thru the Upr MS River Valley under general upr
troffing stretching fm Quebec into the Plains downstream of an upr
rdg in wrn NAmerica. There is a good deal of cld cover stretching
into the Upr Lks under the upr troffing, and there have been some
sct showers mainly over the scentral where wv imagery hints there
may be a weaker shrtwv lifting nwd toward the Upr Lks within the ssw
flow aloft e of the upr trof axis.
Main fcst concerns thru Wed focus on pops for mainly the se cwa,
which wl remain under a ssw flow alf e of the slowly progressive
upr trof axis.
Tngt...Although the main closed h5 lo is fcst to continue to drift
slowly s and into nrn Missouri by 12Z Wed, most of the guidance
indicate some hier mid lvl rh/large scale forcing wl impact roughly
the se half of the cwa, where the winds alf wl be out of the sw on
the ern flank of upr trof stretching fm James Bay to the slowly
departing closed upr lo. Since the llvl flow wl remain weakly cyc,
wl retain some pops in this area. But absence of any daytime
heating, exit of closed lo/sharpest forcing to the s, and concerns
about impact of some dry air in the h9-85 lyr supporting more breaks
in the clds to the ne and e wl restrict pops into the chc range.
Even over the w where the forcing wl be weak or even negative,
guidance shows a good deal of mid cld lingering, which wl limit the
diurnal temp fall.
Wed...As the closed lo to the s and upr trof axis drift slowly to
the ese, the guidance shows mid lvl drying/larger scale subsidence
pressing slowly to the ese as well. But since some large scale
qvector cnvgc/deeper mstr wl linger to the e of the upr trof axis
and over the se portion of the cwa thru most of the day, wl retain
some chc pops there thru the day as well. With earlier arrival of
larger scale drying/subsidence, expect at least some sunshine over
the w. Expect temps to rise aoa 60 away fm cooling off Lk Sup in
llvl ne flow.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 246 PM EDT TUE MAY 23 2017
No high impact weather is expected through the long term. Only item
to mention specifically is that there`s a slim chance of some frost
over far western Upper Michigan Wed night. Otherwise, looks like
chances for some light rain over at least portions of the CWA in
each period with temps near or below normal. Did not make any
changes to blended initialization.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 651 PM EDT TUE MAY 23 2017
Expect generally VFR cigs into this evng, when some lower MVFR cigs
likely to dvlp at the TAF sites with upslope llvl nne flow and loss
of daytime heating/mixing. Upstream obs over ne MN/adjoining Ontario
show a good deal of loW clOUd, so lower IFR cigs may impact IWD for
a time. With the arrival of drier air on Wed and daytime
heating/mixing, cigs wl rebound into the VFR range.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 322 PM EDT TUE MAY 23 2017
Expect winds under 20 kts into this coming weekend as a relatively
flat pres gradient dominates the Upper Lakes.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...KC
LONG TERM...Titus
AVIATION...07
MARINE...KC
Area Forecast Discussion
National Weather Service Sacramento CA
310 PM PDT Tue May 23 2017
.SYNOPSIS...
Triple digit heat continues today in the Central Valley then
cooling Wednesday into Friday with near to slightly below normal
readings by the end of the week. Isolated afternoon showers or
thunderstorms possible over the southern Sierra Nevada today and
over the northern interior mountains Wednesday.
&&
.Discussion (Today through Friday)...
Strong upper ridging over Interior NorCal today is resulting in
triple digit heat again in portions of the Central Valley. Hottest
temps across the CWA this afternoon are occurring in the Northern
Sacramento and Northern San Joaquin Valleys. Potential for some
additional record highs to be broken today as the record for KRDD
and KRBL is 101 and 99 at Modesto. Afternoon CU and some TCU have
developed along the Sierra Nevada and will need to be watched,
however latest HRRR not showing any showers or thunderstorms
developing.
Delta breeze expected to ramp up this evening becoming moderate
to strong tonight into Wednesday morning. Marine layer deepens
tonight as offshore upper low approaches and combined with Delta
breeze will provide low level CAA into portions of the Central
Valley overnight.
Upper troughing over the PacNW digs towards the Great Basin
tomorrow as associated weak cold front stalls over northern
portions of CA. This may provide enough lift to set off a few
afternoon showers or thunderstorms over the Coastal and northern
interior mountains. Increased Delta breeze and synoptic cooling
over the area Wednesday will result in about a 10 degree drop in
max temps.
Broad upper troughing continues over the forecast Thursday into
Friday providing additional cooling. Highs expected in the 80s
throughout the Central Valley Thu/Fri, 70s in the Delta, and 50s
to around 80 for the mountains and foothills.
PCH
&&
.EXTENDED DISCUSSION (Saturday THROUGH Tuesday)
A ridge will be in place for the holiday weekend and that will
bring warming temperatures and quiet weather. If you have outdoor
plans over the weekend you will want to be prepared for hot
weather. Highs on Saturday will be in the 80`s and 90`s but we
will warm into the 90`s and lower 100`s by Memorial Day. A Delta
breeze will keep that region a little more comfortable throughout
the weekend though. We will also see some instability build into
the higher elevations and we could see a few isolated afternoon
and evening t-storms in the Sierra. The ridge starts to flatten
out later Monday and a short wave trough moves into the region on
Tuesday. This will keep isolated t-storm chances in the forecast
for the Sierra. Temperatures will also be a bit cooler on Tuesday
but still above normal.
-CJM
&&
.AVIATION...
VFR conditions expected at the TAF sites the next 24 hours. Local
wind gusts to 20 knots possible in the Delta after 00z Wed
otherwise 5-10 knot winds can be expected. Slight chance for
isolated t-storms over the Sierra south of US-50 between 23-03z.
-CJM
&&
.STO WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$