Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/21/17
Area Forecast Discussion
National Weather Service La Crosse WI
945 PM CDT Sat May 20 2017
.SHORT TERM...(This evening through Sunday)
Issued at 316 PM CDT Sat May 20 2017
At 3 PM, dry slot was approaching the Interstate 90 corridor. This
dry slot will provide some dry time for late this afternoon and
early evening...then as the upper level low and occluded front
moves through the area another band of rain will move through the
region. With most unstable CAPES climbing up to 500 J/kg, there
will be enough instability for isolated thunderstorms during the
mid to late evening. The RAP soundings suggest that there may be
brief window (1 to 2 hours) where there may be enough instability
and 1-6 km shear for the potential of some hail. If this occurred,
it would be in northeast Iowa and southwest Wisconsin.
Warm air advection will allow temperatures to continue to rise
this evening. As a result, our high temperatures for today will
likely not occur until then.
On Sunday, the closed low will move into northern Minnesota and
northern Wisconsin. The cyclonic flow associated with low will
keep skies cloudy across the region and there will be isolated to
scattered showers mainly north of Interstate 90.
.LONG TERM...(Sunday night through Saturday)
Issued at 316 PM CDT Sat May 20 2017
From Sunday night into Wednesday, an upper level low will slowly
transition southeast across the Upper Mississippi River Valley.
This low will produce periodic showers. There will be enough
instability on Monday and Monday evening (CAPES up to 1250 J/kg
south of Interstate 90) and Tuesday afternoon and evening (CAPES
up to 500 J/kg) for isolated to scattered thunderstorms to
develop. With limited shear, not anticipating any severe weather
with these storms. The heaviest rain will be south of Interstate 90
from Monday night into Tuesday. During this time frame, the
rainfall amounts will be up to a half inch.
From Wednesday night into Friday, a 500 mb ridge will provide dry
weather and near-normal temperatures.
On Friday night and Saturday, a short wave trough will be moving
northeast out of the southern Plains. Most unstable CAPES will
climb into the 1500 to 2500 J/kg range. However the shear remains
weak, so not anticipating and severe weather.
&&
.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 945 PM CDT Sat May 20 2017
Cigs: blanket of ifr/mvfr cigs holding across the region, and likely
will stay that way into Sunday night. The sfc low responsible for
the low clouds will gradually exit northward into southern Canada
after 12z Mon-and not expecting a lot of improvement until it does.
Expect some minor diurnal "bump up" Sun afternoon, with a better
shot for clearing after 06z Mon.
WX/Vsby: cold front associated with the low pressure system sliding
northeast across the local area this evening. Forcing along the
boundary should be enough to pop a few scattered showers, with some
potential for thunder (better to the southeast of the TAF sites).
Most of this shifts northeast after 06z.
Had some reductions in vsbys from areas of drizzle earlier in the
evening - most of which has shifted north with the isentropic lift.
Some ifr/mvfr br still found north of the low/sfc front though - and
could impact the TAF sites for a few hours post 06z. Will monitor
and make adjustments as needed.
Wind: east southeast will swing to the south then southwest by Sun
afternoon as the low pulls away. Could be some gustiness to the
southwest of the low.
&&
.HYDROLOGY...
Issued at 316 PM CDT Sat May 20 2017
River Flood Warnings continue along the Mississippi River at
Wabasha, the Trempealeau River at Dodge, the Black River at
Galesville, the Yellow River at Necedah, and along the Wisconsin
River at Castle Rock Dam as runoff from the very heavy rain
earlier this week continues to move through the river system.
Through Wednesday, an upper level low will provide periodic rain.
The heaviest rain will be south of Interstate 90 from Monday
night into Tuesday. During this time frame, the rainfall amounts
will be up to a half inch.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...Boyne
LONG TERM...Boyne
AVIATION...Rieck
HYDROLOGY...Boyne
Area Forecast Discussion
National Weather Service State College PA
1130 PM EDT Sat May 20 2017
.SYNOPSIS...
High pressure well to the north of the state will slide to the
south and east tonight and be centered over the eastern
seaboard on Sunday morning. Low pressure will move from the
plains states into the upper Great Lakes Sunday and Monday. A
cold front will push through the state later Monday. The weather
will remain unsettled through the week as a large upper level
trough advancing slowly from the midwest.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Subsidence inversion persists this evening with low broken to
overcast now being overrun by increasing mid to high cloudiness
from the west as upper ridge tracks eastward. Am not expecting
substantial improvement overnight in areas where the clouds
currently remain, as inversion trapping llvl moisture will keep
mostly cloudy skies with isolated drizzle and the HRRR even
indicating isolated showers traversing the north central and
central mountains. Mid/high clouds will continue to increase
overnight...while winds go light.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/...
Expect most of the area to remain rain free for the balance of
the day on Sunday. POPs will be high over the west as heights
fall sufficiently there by the end of the day. The morning cloud
debris overhead will probably hold temps down, but not as cool
as Sat. A more- southerly wind will push temps into the m-u60s.
&&
.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
A cold front should cross central Pennsylvania Sunday night
into early Monday, accompanied by scattered showers and possibly
some thunder. Looks like flow from the south (parallel to the
front) will push a wave up the east coast during the day on
Monday, with a period of moderate rain poss in eastern counties
(though biggest impacts look to be east of CWA). Lighter precip
ends from the west during the day.
A weak area of high pressure will build in for Mon night and
Tuesday with a cooler morning and maybe some patchy fog in
store.
Weather pattern turns unsettled again during the middle and
later part of the week, as an upper-level low drops into the
Great Lakes and surface low pressure develops over the Mid-
Atlantic region. Light showers may begin to work into the region
on Wed, with Thursday looking quite wet and dreary as a soaking
rain looks likely.
The upper-low should begin to lift out by Friday, allowing
conditions to slowly improve. Light showers or drizzle may
linger under the upper low on Friday keeping a coolness in the
air. The weekend should bring a return of brighter skies, warmer
temps and dry weather.
&&
.AVIATION /04Z SUNDAY THROUGH THURSDAY/...
Low ceilings and stratus persist across almost all of Central
Pennsylvania, except for KIPT, where skies are clear. Easterly
flow continues and will likely keep the clouds over the region
overnight. Fog is also beginning to develop, and have increased
fog in the TAFs as well with the 03z updates. Will have to watch
KIPT, as the potential of dense fog formation possible if skies
remains clear there.
Front makes slow progress eastward, and likely that rain will
remain out of most TAF sites through 00z tomorrow except for
KBFD and KJST. Here, introducing VCSH after 14z/15z, and
prevailing SHRA after 21z.
Slowly progressing front will mean widespread rain/showers and
possible TSRA across the region Sunday Night into Monday, with
gradual improvement west to east after frontal passage.
.OUTLOOK...
Mon...MVFR/IFR in SHRA/TSRA in the morning over the west and
all day in the east.
Tue...AM fog possible. Otherwise no sig wx.
Tue PM-Wed...Restrictions developing with numerous showers and
thunderstorms.
Thu...Some restrictions AM Fog and possible showers.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Dangelo
NEAR TERM...Dangelo/DeVoir
SHORT TERM...Dangelo
LONG TERM...RXR
AVIATION...Jung
Area Forecast Discussion...UPDATED
National Weather Service Duluth MN
904 PM CDT Sat May 20 2017
.UPDATE...
Issued at 904 PM CDT Sat May 20 2017
The back edge of the main area of rain is continuing to make
steady progress northward this evening, as the dry slot evident in
GOES-16 band 10 water vapor imagery continues to rotate northward.
Steady rain should be confined to the northern part of the CWA
for the rest of the night, with a south to north decreasing trend
with time.
With that said, there is still decent forcing for ascent within
the dry slot as evidenced by redevelopment of showers from the MSP
metro area into northwest Wisconsin. This is in an area of
moderate forced ascent per QG diagnostics and decreasing
stability, so we expect continued redevelopment of showers in this
area for much of the night, just not the widespread steady rains
of the past several hours. Finally, the rapid development of fog,
very low stratus clouds, and drizzle has followed within an hour
or so of the end of the steady rain, and this will likely spread
northward with the leading edge of the dry slot aloft through the
rest of the night.
&&
.SHORT TERM...(This evening through Sunday)
Issued at 401 PM CDT Sat May 20 2017
Light to moderate rain showers will continue to expand northward
this afternoon and evening as a mid- to upper-level trough,
characterized by upper-level diffluence and stronger isentropic
lift at the mid-levels, will continue to ascend into the area.
Some 850-700 mb layer warm air advection will also provide
additional support for these rain showers. There have been reports
of some sleet with the leading edge of the precipitation shield,
which should continue through the afternoon, but taper off by the
evening as warmer low-level air moves in. There is the potential
for some thunderstorms, especially over northwest Wisconsin and
adjacent counties of northeast Minnesota. MUCAPE instability
values look to increase after midnight tonight due to steepening
mid-level lapse rates. Winds will remain gusty into the evening
and early Sunday morning hours before gradually weakening through
the night-time hours. Strongest wind gusts will remain over
adjacent locations near Lake Superior as winds remain from the
east and northeast, providing better fetch to intensify these
winds. The NAM model was indicating the potential for some light
snow over Itasca and Koochiching
Miller/Millercounties mainly after midnight.
However, if it does occur, it should be brief, and not expected to
lead to any accumulation as the sfc temperatures are just too
warm for it.
As the sfc low pressure center drifts closer to the region, there
may be a brief period of drier conditions over northwest Wisconsin,
due to a dry slot, mainly between 03z and 07z Sunday, as evidenced
by the latest HRRR/NAMNest models. Reduced the POPs accordingly over
this area. However, a corridor of positive vorticity advection will
bring another round of showers of northwest Wisconsin after 07z,
again as per the HRRR model.
Rain showers should turn to more drizzle on Sunday, especially over
our southern counties, due to decreasing moisture depth as seen in
the 20.12z NAM/GFS soundings. The NAM soundings indicate the depth
of the saturation layer to be around 6000 ft, which is sufficient
moisture depth for drizzle. Moreover, Pwat values gradually decrease
through the day Sunday. Still expecting chances of rain showers to
linger over most of the Northland through the day Sunday, with the
best chances lingering over the Iron Range and Arrowhead regions.
Overall rainfall amounts up to three-quarters of an inch will be
possible by Sunday evening.
.LONG TERM...(Sunday night through Saturday)
Issued at 355 PM CDT Sat May 20 2017
The large upper low over the region will continue to wobble slowly
north Sunday night through Monday night, keeping a chilly airmass
over the area with chances for rain/drizzle. Even as the low drifts
farther away from the area on Tuesday, a shortwave dives into the
area on the back side of the low to generate still more clouds and
showers. With the cloud cover, temperatures will only get into the
50s both Monday and Tuesday, with overnight lows in the mid 30s to
low 40s.
Tuesday night there is potential for clearing and drier air to move
into the area from the north, and with the north flow continuing, we
are likely to have another cold night, with lows around freezing
possible in the Arrowhead. We will have to watch this, as there may
be need of a frost/freeze headline. This area got down around
freezing the last two mornings, as well as a week ago so there
probably won`t be much of an impact yet.
Upper level ridging builds into the area for Wednesday and
Thursday, which should bring us a period of warmer and drier weather
for both days. However, towards Friday the ridge shifts far enough
east to allow chances for rain to return to the area for Friday and
Saturday. Would not be surprised to see this pushed later as the
ridging pattern is somewhat blocky in nature and may slow down in
later model runs. The return of southwest flow will also bring
above normal temperatures back to the region for the later part of
the week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 649 PM CDT Sat May 20 2017
Widespread light/moderate rain has spread across all terminals
except KINL as of 2330z, and is expected to begin within the next
few hours at KINL as low pressure over Iowa slowly moves
northeastward through the 24 hour period. Confidence is rather
high in conditions continuing to deteriorate to MVFR and
eventually IFR in most location overnight and persist for much of
Sunday. While widespread light/moderate rain is expected to
diminish in coverage/intensity after the first 4-6 hours, the
development of widespread low ceilings and fog is expected area-
wide. Winds should slowly back to north and eventually northwest
by the end of the period as the center of the low pressure area
moves to Lake Superior.
&&
.PRELIMINARY POINT TEMPS/POPS...
DLH 37 48 40 56 / 100 70 50 30
INL 40 49 41 53 / 80 80 50 50
BRD 40 50 41 60 / 100 40 40 30
HYR 44 53 42 58 / 90 70 50 30
ASX 39 51 41 57 / 100 70 50 30
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...Small Craft Advisory until 10 AM CDT Sunday for LSZ121-140>143-
146>148.
Small Craft Advisory from midnight tonight to 10 AM CDT Sunday
for LSZ144-145.
Gale Warning until midnight CDT tonight for LSZ144-145.
&&
$$
UPDATE...Miller
SHORT TERM...JTS
LONG TERM...LE
AVIATION...Miller
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1155 PM EDT Sat May 20 2017
.AVIATION...
Main potential vorticity anomaly is shown to pivot aggressively to a
negative tilt over the central Mississippi River Valley between 06-
12Z. This strongest of forcing is shown to miss the area to the
west. However, rich lower tropospheric theta e content will bedrawn
due northward out of the Ohio River Valley and eclipse or surge
northward through western and central sections of lower Michigan. It
is in this general vicinity that a secondary height fall maximum is
shown to lift through as a triple point develops over southwestern
Michigan under a boatload of 925-850mb frontogenesis.
Midlevel lapse rates will be unimpressive at moist adiabatic or
slightly better. Not expecting any strong thunderstorms tonight or
explosive development. Latest timing has a glaciated cluster or
ragged line of multicells pushing directly through semich in the 06-
10Z timeframe this morning. Some lingering light showers or drizzle
is then expected through mid morning. The other timeframe to monitor
will be after 20Z this afternoon when activity could re-initiate
along the cold front slicing across the area. Latest forecast data
continues to suggest this development will occur over far eastern
lower Michigan east of the terminals.
//DTW THRESHOLD PROBABILITIES...
* High for ceiling aob 5000 feet tonight.
* Moderate for thunderstorms between 06-08Z tonight.
&&
.PREV DISCUSSION...
Issued at 909 PM EDT Sat May 20 2017
UPDATE...
A robust thunderstorm response this afternoon and early evening
across portions of northwestern Indiana. This activity is being
driven in the center of a mesoscale circulation and small height
fall bullseye that is being kicked out ahead of the main vorticity
anomaly going negative tilt over the mid Mississippi River Valley. It
really is sort of messy tracing back but it appears the shortwave
energy has a history back to previous convection yesterday over MO
and AR. All things lining up for this response as NAM suggests this
is on the northern edge of what should be strengthening 925-850mb
frontogenesis and deformation. It is from this northern edge of the
thunderstorm activity that an elevated triple point is forecasted to
emerge over southwestern lower Michigan after 06Z tonight. Would not
characterize this setup as one with a tremendous amount of dynamical
forcing: detached well away from upper level Jet streak, removed from
the most direct of cva, and no organized convergence maximum to the
low level jet. Rather, it appears to be a good mix of prior
convective vort max, subtle low level limiting streamline and north
to south orientated convergence zone, and a surface warm front.
Surface analysis places this surface cold front from portions of
northeastern Illinois down into central Illinois. Middle 70s for
temperatures and mid-upper 60s dewpoints has contributed to +1000
MLCAPE and approximately 1500 SBCAPE to the south of the boundary.
SPC RAP based mesoanalysis depicts a very sharp instability gradient
with little to no instability in place at this time across the
northern couple of tier of counties in northern IN. Radar trends from
KIWX support this initialization analysis as the most northern
activity has been weakening or glaciating.
The rest of tonight...Given the aggressive nature of the convective
response thus far, feel the nam solutions with a deeper cyclonic
circulation is the direction to hedge. Latest iterations of the HRRR
are in agreement with steady northward development of showers and
thunderstorms throughout the remainder of the evening hours. Best
consensus would bring showers and thunderstorms to the doorstep of
much of the western cwa (including Tri Cities) sometime around 5Z or
soon after midnight. Strong easterly flow here over southeastern
Michigan has a very cool and stable airmass in place (dewpoints are
overwhelmingly in the 40s). Pouring through forecast soundings
suggests little to no potential for surface based convection even as
the warm advection kicks into overdrive. The reason for the high
confidence in no surface based convection is that strong static
stability will exist in the lowest 1800 ft agl through 12z. The RAP
does suggest some potential for the existence of a steep midlevel
lapse rate pocket despite a lack of one in the Mesoanalysis. Just
enough cooling with height in the midlevels to potentially result in
upwards of 750 J/kg of MUCAPE, particularly across the far southern
cwa and Detroit. Farther north, all forecast soundings point to
straight moist adiabatic. With the amount of moisture that is
expected to converge over lower Michigan and the look of the forecast
soundings there will be a heavy rainfall potential tonight. Would
not be surprised at all if some locations were able to get a quick
+1.00 of rainfall.
The forecast message...showers and thundestorms becoming likely
after midnight...primarily in the 5-9Z timeslot. Some potential
exists for the activity to miss metro Detroit by scraping past to the
NW. However, confidence in completely missing is low. The threats
tonight for the strongest of storms will be small hail, heavy
rainfall, and lightning.
PREV DISCUSSION...
Issued at 353 PM EDT Sat May 20 2017
DISCUSSION...
MVC from earlier convection over the Plains is now lifting from
southwest Michigan into Central Michigan, and should track through
the Saginaw Valley during the very late afternoon and early evening.
Showers and thunderstorms associated with this feature will continue
to lift across the area, and should continue to exhibit a gradual
weakening trend they encounter higher stability over Michigan.
Overall, expecting high coverage of measurable rainfall.
Large upper low over the Central Plains will slowly lift northeast
through the upper Midwest late tonight and Sunday, and into Ontario
by Monday. This system will provide a good chance for precipitation
as it lifts to our west, with the main area of precipitation still
expected to push across the area late tonight into Sunday. This will
occur as the better moisture axis works through the area and a
shortwave trough axis pivots through the Western and Central Great
Lakes late tonight and Sunday. There looks to be a break in the
forcing during the late morning to early afternoon, with some drier
air also filling into the area, before the cold front sweeps across
the area later in the day. Extent and strength of any second round
of convection will depend, per usual in Michigan, on how much we can
destabilize before the frontal passage and perhaps even on how much
dry air becomes entrained into the boundary layer. NAM/GFS show
activity becoming surface-based after some daytime heating, with
about 500-1200 J/kg of SBCAPE able to build from roughly Flint east
by the time the cold front works across late in the day. (This is
assuming we reach forecast highs.) Skinny CAPE profiles and not too
impressive wind field should limit the threat for severe storms.
Temperatures will be a little tricky given muddled start to day, but
southerly flow ushering in warmer air ahead of the front and mild
start to the day should translate to max temps in the 70s.
Another strong shortwave looks to pivot through Central/Northern
Michigan as it rotates around the upper low over Ontario on Monday.
Forcing and moisture from this feature looks to remain primarily
north of the area however, and expect that is where precipitation
will remain. More noteworthy item for Monday will be the development
of breezy conditions once again as a westerly gradient tightens
between surface low pressure over Ontario and high pressure
strengthening over the Plains and Ohio Valley. Temperatures will
cool in the post-frontal airmass on Monday, reaching into the 60s,
which is just slightly below seasonal normals.
Mid-level troughing in association with an cut-off low will bring
rain chances for much of the extended period. A surface low pushing
east from IL/WI into lower Michigan will start off by bringing rain
chances Tuesday into Wednesday. The cut-off low is then expected to
be stationed over or near the Ohio Valley, and will spin-up a series
of upper-level disturbances which will bring additional chances for
pop-up showers Wednesday into Thursday. While a rumble of thunder
may be possible embedded in a shower or two, stability parameters
remain not all that impressive, thus general thunder chances have
been left out of the forecast. As the cut-off low moves east into
New England, upper-level ridging is then expected to settle across
the North Central Plains and Great Lakes through Friday and
Saturday, which will act to diminish rain chances.
A warming trend is also looking more probable for Memorial Day
weekend. Expect daytime highs peaking in the 60s during the middle
of the week, with a warm-up into the 70s for both Friday and
Saturday.
MARINE...
High pressure over the eastern Great Lakes and low pressure over the
Midwest will combine to support continued moderate easterly wind
early tonight. Small craft advisories remain in effect through the
evening before a weakening and veering wind trend develops
overnight. This will shift stronger wind over north sections of Lake
Huron through Sunday as a weak cold front moves through the region.
Southwest flow will then strengthen during Monday as low pressure
stalls and deepens north of Lake Superior. This will likely produce
wind exceeding small craft advisory levels on Saginaw Bay before
diminishing Monday night. The middle of the week looks unsettled in
terms of rain as another low pressure system develops over Missouri
Tuesday and moves into Lower Michigan Wednesday.
HYDROLOGY...
A weakening pattern of showers with isolated thunderstorms will move
through SE Michigan during late afternoon. Locally heavy downpours
with this activity will be capable of a quick 0.25 inch of rainfall.
This will be followed by a break in coverage through most of the
evening before another round of showers and storms develops toward
midnight and lasts through mid Sunday morning. There will be a
better chance of thunderstorms and heavy rainfall during this time.
Additional amounts of 0.25 to 0.75 will be possible producing totals
up to 1 inch in spots. The break between the late afternoon and
overnight activity will minimize potential for flooding, although
some ponding on area roads and in prone areas will be possible.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&
$$
AVIATION.....CB
UPDATE.......CB
DISCUSSION...HLO/AM
MARINE.......BT
HYDROLOGY....BT
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
632 PM CDT Sat May 20 2017
.AVIATION...
The cold front that produced showers and thunderstorms throughout
South Central Texas today has pushed south of the terminals towards
the Texas Coast. Because of this convection has ended with storms not
expected for most of the evening. VFR conditions will continue
through the evening before status builds back in around 06z at all
terminals. The HRRR and other high resolution models indicate showers
returning to the area late tonight as the low level jet kicks in.
Because of this vicinity showers has been added to all terminals
(AUS/SAT/SSF/DRT). MVFR conditions and showers will continue through
most of Sunday as well. Late Sunday into Sunday night showers and
thunderstorms are expected to increase across South Central Texas
again. For now will leave VCSH as timing and intensity vary depending
on which high resolution model examined. Will let later TAF issuances
refine the precipitation forecast for late Sunday at the terminals.
Winds in general will be north at all terminals between 7 and 13
knots.
&&
.PREV DISCUSSION... /ISSUED 329 PM CDT Sat May 20 2017/
SHORT TERM (Tonight through Sunday Night)...
A cluster of strong thunderstorms with very heavy rain over Frio
County is likely to continue to push to the east-southeast in the
next few hours. This cluster of storms is being lingering there for
hours at the tail end of the cold front. Storm total rainfall amounts
over parts of Uvalde and Frio counties reached 6 to 8 inches of
rain past 8 hours based on radar estimation numbers. There is the
potential for isolated severe thunderstorms within the next few
hours mainly along and south of Highway 90 where SPC has a severe
thunderstorm watch in effect through 5 PM CDT.
HiRes models are all over the place with the weather conditions
expected for late this afternoon and evening. Went ahead with a blend
of HRRR and RAP solutions where the cold front continues to push
slowly to the southeast with slight chances for strong to severe
thunderstorms to develop for the period with moderate confidence on
locally heavy rain capable of producing localized flooding.
There is a slight chance for elevated convection behind the front
late this afternoon and evening across portion of the southern
Edwards Plateau and Rio Grande with additional scattered showers and
isolated thunderstorms along the Rio Grande Plains overnight.
A second round of severe thunderstorms is possible along and west of
Interstate 35 on Sunday as an upper level low pressure system over
the northern Plains moves towards the Upper Midwest. The surface
boundary/cold front is expected to stall or slowly push back to the
north over the coastal Plains and brings southeasterly winds to the
Rio Grande Plains. This combination will aid the development of
strong to marginally severe thunderstorms capable of producing large
hail and damaging wind gusts in addition of localized heavy rain.
LONG TERM (Monday through Saturday)...
The wet weather pattern continues into Monday as an upper level
short-wave disturbance moves across the area and abundant Gulf
moisture remains in place. Another cold front is forecast to push
across the area Tuesday morning with chances of rain expected across
the entire area. Weather conditions begin to improve Wednesday with
dry weather expected through Saturday. Temperatures will be below
normal values through the middle of the week and back to near normals
by Thursday through the upcoming weekend.
&&
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 82 66 81 67 79 / 60 20 30 60 70
Austin Bergstrom Intl Airport 80 66 81 67 78 / 60 20 30 60 70
New Braunfels Muni Airport 79 67 81 67 80 / 60 20 30 70 70
Burnet Muni Airport 81 63 78 63 77 / 50 30 30 60 60
Del Rio Intl Airport 80 68 81 68 85 / 40 40 50 60 40
Georgetown Muni Airport 82 64 79 64 77 / 60 30 30 60 60
Hondo Muni Airport 79 69 82 68 82 / 80 20 30 70 50
San Marcos Muni Airport 77 67 80 66 79 / 60 20 30 60 70
La Grange - Fayette Regional 86 68 83 69 80 / 60 40 30 50 80
San Antonio Intl Airport 75 68 81 68 81 / 60 20 30 70 60
Stinson Muni Airport 79 69 82 69 81 / 60 30 30 70 60
&&
.EWX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Mesoscale/Aviation...Treadway
Synoptic/Grids...04
Public Service/Data Collection...Williams
Area Forecast Discussion
National Weather Service Grand Forks ND
851 PM CDT Sat May 20 2017
.UPDATE...
Issued at 851 PM CDT Sat May 20 2017
No significant updates planned for the late evening. Arc of low
stratus and light rain continues to wrap around the low pressure
system lifting across far southern MN...having overspread most
all of the FGF forecast area. HRRR updates show widepsread light
rain over west central MN and the MN Lakes Country transitioning
to more of a drizzle/mist/fog with embedded light rain after
midnight...which is fairly consistent with the 00z NAM12 package.
UPDATE Issued at 635 PM CDT Sat May 20 2017
Widespread and very light rain with some few hundredths of an
inch accumulation has spread northward through the Grand Forks
area and will continue a slow expansion into far northwest MN,
northeast ND and at least the eastern half of the Devils lake
Basin.
Areas with a tenth of an inch or more have so far been confined
to the south of a line from Cooperstown to Hillsboro to Fosston.
Cloudy and cool conditions with periods of light rain and a
steady northeast breeze should persist throughout the evening and
overnight. The southern RRV and MN Lakes Country should continue
to receive greater overall rainfall during the evening and
overnight periods.
&&
.SHORT TERM...(This evening through Sunday)
Issued at 334 PM CDT Sat May 20 2017
Latest runs of the HRRR have been doing pretty well in showing the
timing and north advance of the light rain shield. The light rain
will reach the far northern RRV this evening. Dry low levels will
continue to mean radar at first will be overdoing actual rain at
the ground. Latest models do take upper low more north and over
the Red River valley Sunday morning. Dry slot may work up into
west central MN tonight, while a steady light rain continues in
the RRV. Still looking like west edge of rain JMS-DVL. With this
in mind not a lot of further changes were made to the grids. Main
area of light rain will shift northeast Sunday, though lingering
patches of sprinkles/drizzle may remain behind it. Rainfall
amounts remain unchanged from prev thoughts with well under 0.10
inch DVL region to 0.25 to 0.50 GFK/FAR to a bit over 0.50
BJI/PKD/ADC region.
.LONG TERM...(Sunday night through Saturday)
Issued at 334 PM CDT Sat May 20 2017
Upper low moves remains over nrn MN Sunday night. Then a
secondary short wave will drop south thru western half of ND and
Monday helping to keep the upper low over nrn MN. Enough clearing
may occur so that some sun will lead to destabilization Monday
with heating and cause showers to form with the cold air aloft.
Upper low/trough will exit area on Tuesday with improving
conditions.
For Wednesday...surface high pressure remains in control and the
upper ridge begins to shift across the Dakotas and Minnesota. With
return flow and the shifting of the upper ridge...expect
temperatures to rebound with values in the low 70s. Otherwise by
Friday...an area of low pressure and trailing cold front begins
crossing the region...with increased chances for showers or storms.
Little temperature change is expected through the end of the
period.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 635 PM CDT Sat May 20 2017
Expect widespread MVFR conditions in low clouds and light rain
across the central and southern Red River Basin...with areas of
IFR CIGS developing during the overnight...especially along and
south of a Jamestown to Fargo to Bemidji line. Across the Devils
Lake Basin and northern Red River Basin expect areas of MVFR
conditions in low clouds and very light rain. Patchy IFR
conditions in low clouds and very light rain are possible from
Grand Forks and Grafton...eastward into the Red Lakes during the
early morning.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
&&
$$
UPDATE...Gust
SHORT TERM...Riddle
LONG TERM...Hopkins/Riddle
AVIATION...Gust
Area Forecast Discussion
National Weather Service Green Bay WI
1019 PM CDT Sat May 20 2017
Updated aviation portion for 06Z TAF issuance
.SHORT TERM...Tonight and Sunday
Issued at 232 PM CDT Sat May 20 2017
The latest rap analysis and satellite/radar imagery show low
pressure centered over western Iowa, and associated warm front
extending east across central Illinois/Indiana early this afternoon.
Arcing band of rain is lifting north across central Wisconsin, and
approaching the Highway 29 corridor. Thunderstorms have remained
well south of the area so far today, but the band of rain will
continue to lift north through the afternoon and should approach the
U.P. border by 00z. Behind the rain, spotty showers and some
drizzle are occurring over Iowa and northern Illinois. As the low
pressure tracks across the region, precip trends are the main
forecast concern.
Tonight...Low pressure will swing northeast into the northern
Mississippi Valley and western Great Lakes by late tonight. Arcing
band of light to moderate rain will lift north ahead of the low and
across northern Wisconsin during the evening. Behind the band of
rain, mid-level drying will drop inversion heights to 800-850mb,
which will temporarily put a halt to the rainfall, but will likely
leave areas of drizzle, low clouds, and possibly some fog. Then a
occluded front will lift from southwest to northeast across the area
late tonight. Some instability in the models along the boundary,
and forcing via potent shortwave could bring another band of showers
and a few thunderstorms to the area. As a result, removed thunder
chances through midnight, but left the mention after midnight to
account for this possibility. Lows only falling into the mid 40s
north and low 50s south.
Sunday...The occluded front will exit northeast Wisconsin by mid-
morning, bringing an end to the widespread shower and isolated
tstorm threat. The incoming dry slot should bring dry weather for
the rest of the day to eastern WI. But moisture wrapping around the
low will return occasional light showers to central and north-
central WI, mainly during the afternoon. Highs will range from the
low 50s over the west to around 60 in the east.
.LONG TERM...Sunday Night Through Saturday
Issued at 232 PM CDT Sat May 20 2017
Main forecast concerns include precipitation trends for the first
half of the week, a period of dry weather late in the work week,
and a warm-up by the weekend.
A potent negatively-tilted short-wave trof will sweep across
northern WI late Sunday night into early Monday, so have boosted
pops to likely over north central WI during that period.
Following that, a cold front is expected to shift across the
forecast area later Monday into Monday night, then slow down or
stall out as a surface wave lifts northeast along the boundary on
Tuesday. Models all offer different timing with the wave, which
will impact whether or not any significant rains impact the
southeast part of the forecast area, or occur to our east.
Canadian high pressure will build into the region midweek, with
dry conditions expected from Wednesday night through at least
Friday. Abundant sunshine will cause temperatures to moderate,
with readings rising to above normal again by Friday and Saturday.
Return flow on the back side of the high may bring a small chance
of storms to our western CWA late Friday night or Saturday, but
the best precipitation chances should hold off until Saturday
night.
&&
.AVIATION...for 06Z TAF Issuance
Issued at 1019 PM CDT Sat May 20 2017
As a band of rain showers departs north of the state
at midnight, another band of showers along a frontal boundary,
with an isolated storm possible, will pass over the area late
tonight. In between these bands of showers, widespread IFR/LIFR
cigs with IFR/MVFR vsbys due to fog. Vsbys to improve after the
fropa late tonight or Sunday morning with cigs gradually
improving late Sunday morning into the afternoon to mainly mvfr
levels.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM.....MPC
LONG TERM......Kieckbusch
AVIATION.......TDH
Area Forecast Discussion
National Weather Service Lincoln IL
919 PM CDT Sat May 20 2017
.UPDATE...
Issued at 919 PM CDT Sat May 20 2017
Widely scattered showers and thunderstorms have developed in
advance of a cold front across the Illinois River Valley this
evening. Latest radar imagery continues to show the cells
struggling to organize as daytime instability wanes...with the
activity mainly confined to locations from Rushville southward.
HRRR has been consistently showing scattered convection spreading
E/NE across the remainder of the CWA by midnight, with showers
ending from west to east overnight.
&&
.SHORT TERM...(This evening through Sunday)
ISSUED AT 300 PM CDT Sat May 20 2017
Warm front has pushed northward across most of the forecast area,
and was just starting to come into the areas from Galesburg to
Lacon at 2 pm. Quite a bit of thinning in the clouds has taken
place south of the front, and SPC mesoanalysis shows surface
based CAPE`s have reached 1500-2500 J/kg from about Bloomington
southward, although some capping is still evident looking at
mixed-layer CAPE. Initial line of convection has formed to our
southeast and was tracking northeast into Indiana, which just some
weak showers from around St. Louis southwest.
Main issue for this part of the forecast will be with convective
redevelopment ahead of the cold front, which is currently back in
western Missouri. High-res models have been trying to focus on a
couple bands of convection, one forming near I-57 during mid-
afternoon and another one arriving early evening immediately
ahead of the front. The NAM and HRRR support CAPE`s around 1000
J/kg through sunset across western Illinois as the line arrives,
although the better shear lags behind just a bit. Still may see
a broken line of stronger storms though, with the threat waning
toward late evening. Most of the forecast area will be dry by
about 3-4 am once the front passes. While Sunday should remain
dry, the circulation around the departing low will keep a fair
amount of cloudiness across the northern CWA.
The Flash Flood Watch for Sangamon County was extended into Sunday
morning, as hydrographs downstream of Spaulding Dam continue to
show a steady rise.
.LONG TERM...(Sunday night through Saturday)
ISSUED AT 300 PM CDT Sat May 20 2017
The large upper low will slowly lift northeast early next week,
with a secondary lobe of energy swinging into the Great Lakes
Monday night into Tuesday. Scattered showers and a few
thunderstorms will be possible with this system. The trough will
continue to deepen as it moves into Illinois early Wednesday, and
some cold-core showers will be possible mid-week as lapse rates
steepen due to 500 mb temperatures down to -20C. Have included
some isolated thunder mention in the grids Wednesday afternoon due
to the steep lapse rates as well.
The upper low will finally shift off to the east late in the week,
allowing for a narrow ridge to build eastward from the Plains.
Some discrepancies with the models late-week in terms of a
shortwave coming out of the Rockies to help disrupt the ridge,
with the ECMWF most aggressive with any associated rain activity.
Have kept rain chances in the 20% range for now.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 645 PM CDT Sat May 20 2017
Central Illinois remains largely dry early this evening: however,
latest radar imagery is beginning to show widely scattered showers
developing well in advance of an approaching cold front from near
KMQB to KPPQ. HRRR suggests these cells will become more numerous
over the next few hours as they track northeastward toward the
I-55 corridor. Will include VCTS at both KPIA and KSPI through 05z
accordingly...but will hold off on any thunder mention further
east until radar trends become better established. Any storms that
develop will diminish toward midnight as the cold front pushes
into the area. Forecast soundings continue to suggest a brief period
of MVFR ceilings immediately behind the front...mainly at the
eastern terminals. These clouds will rapidly clear out by 10z. After
that...the main aviation challenge on Saturday will be potential
MVFR ceilings spilling into KPIA/KBMI. Based on NAM forecast
soundings...have lowered ceilings to MVFR at KPIA by 14z...then
further east to KBMI by 17z. Further south...kept ceilings in the
low VFR category through the day.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through Sunday morning for ILZ051.
&&
$$
UPDATE...Barnes
SHORT TERM...Geelhart
LONG TERM...Geelhart
AVIATION...Barnes
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
1056 PM EDT Sat May 20 2017
.UPDATE...
Issued at 1056 PM EDT SAT MAY 20 2017
Had some convection develop along left over outflow boundaries as
mentioned earlier. Stuff has been avoiding southwest areas.
However, widespread rain is now working into our southwest zones
associated with a mid level wave pushing northward. This rain will
continue to overspread the area overnight setting up a damp night
and a damp start to Sunday for most of the area. Thunderstorm
chances will be slowly diminishing overnight as instability
diminishes with the widespread rain moving into the area. A few
isolated storms will remain possible however. Updated temperature
grids based on the rain cooled air in the east. Also, receiving
numerous reports of significant flash flooding in Magoffin county
associated with the ongoing flash flood warning. We may need to
consider a flash flood watch if more significant rain threatens
the area again.
UPDATE Issued at 645 PM EDT SAT MAY 20 2017
All convection has shifted off to the north and east of the area
with a lull expected through the early evening hours. A modest
moisture gradient is in place across the area with areas near the
Cumberland river in the southwest seeing dewpoints into the mid
50s, while dewpoints reside near 70 or higher to the north and
northeast. With the dry air in the southwest, have removed any
thunderstorm chances for the evening. Left some isolated pops in
the areas with better moisture, but confidence is low if we will
see new development. However, some left over boundaries have been
noted in the area, so it wouldn`t take much to see some new
development towards sunset. In fact, both the RAP and HRRR show
this potential, so will leave some low end pops in over the next
few hours. Also with the rain moving in tonight, models are fairly
consistent with this idea, so have bumped pops up to categorical.
&&
.SHORT TERM...(This evening through Sunday night)
Issued at 418 PM EDT SAT MAY 20 2017
A warm front located just north of the CWA has kept warm southerly
flow across the region today, and has recently been the epicenter of
which isolated to scattered convection has developed. While storms
are generally located along our northern periphery and moving out of
the CWA as of 4pm, the continued presence of this
warm/moist/unstable airmass cannot rule out some continued isolated
development through this evening. Latest CAMs aren`t in very good
agreement, but all of them do show that a few more developing storms
are not completely out the question through this evening, so kept
isolated mentioned through the evening. By this evening the warm
front will begin to lift northward as surface low pressure moves
northeast towards the Upper Great Lakes region overnight and pulls
it with it. This movement will also drag a surface cold front
farther eastward into Western KY overnight.
This cold front will be the main concern throughout the short term
portion of the forecast as it continues its track eastward, reaching
and then passing across the eastern portion of the state Sunday
evening through Sunday night, exiting by 12Z Monday. A line of
convection has already developed across the western portion of the
ahead of this frontal feature, and is poised to continue eastward
ahead of the approaching front. Models are all in good agreement
that convection, potentially widespread, will begin impacting our
CWA overnight, with scattered to numerous convection continuing
throughout the day Sunday, before the front finally pushes through.
Once the front does pass over a location, temperatures will quickly
drop and dry air will fill in within the matter of a couple of
hours. This will result in a defining line as to where the front is,
with a cut off to clouds and precip just behind. In fact, the pops
are likely too broadbrushed for the cut off that will likely occur,
but will keep them as such just given some uncertainty on timing.
Latest forecast soundings continue to support heavy raining cells
for the convection that occurs overnight and tomorrow, with the
entire forecast column saturated from the ground up, but not a lot
of forcing otherwise. This will eliminate most hail concerns, and
winds are not overly impressive, but can`t rule out a few higher
gusts in the heaviest storms. Continued to hype up flooding warning
in HWO, as any high precip producing cells could cause problems,
especially if multiple storms pass over the same locations, or
across areas which have already been saturated from rains over the
previous days.
.LONG TERM...(Monday through Saturday)
Issued at 345 PM EDT SAT MAY 20 2017
The models are in fair, but steadily growing, agreement with the
highly amplified pattern that will affect the region through the
extended portion of the forecast. The models depict a relatively
deep trough over the heart of the continent at the start of the
extended with Kentucky in mostly fast zonal mid level flow just to
the south. This upper low will then proceed to consolidate to the
southwest and start to dig through the Plains Tuesday night into
Wednesday. As this occurs, several energy batches will drift over
eastern Kentucky While the core of the low moves into the Ohio
Valley. At this point, the models diverge more with the GFS closing
off the low and settling over Kentucky while the ECMWF is also
starting to close off, but further north - over Lake Michigan.
Either way, plenty of additional energy will pour through the area
to end the work week with some better consensus on moving the upper
low to the Mid Atlantic region on Friday - though the ECMWF is
significantly stronger at this point than the GFS. Heights will then
start to rebound for Kentucky that evening and early Saturday,
though still some energy will probably be working its way across the
state late in the period.
Sensible weather will feature a brief respite from the heat and
humidity Monday, but return flow will quickly brings PoPs, in the
form of showers and thunderstorms, back in later that night and
Tuesday as sfc low pressure takes shape to the southwest - though
somewhat cooler conditions will continue through the rest of the
week. This low will then likely move through the area with heavy
rain a concern in the far east as it slowly passes Tuesday night and
Wednesday. Cooler wx follows to end the work week, but the high
pressure that pushes into the area will not be that strong and
additional showers will be possible on Saturday.
Did not deviate too far from the blend temps for the extended as
conditions look too damp for much of any terrain differences of
note. Also kept the PoPs similar as the blend came in pretty
reasonable.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
ISSUED AT 800 PM EDT SAT MAY 20 2017
Ceilings will come down overnight into Sunday morning as
widespread rain spreads across eastern Kentucky. We may see a few
brief periods of IFR conditions with the rain early Sunday
morning, but expecting it to be mostly MVFR. The MVFR cigs may
hold through much of the day as rain persist into the afternoon
hours.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...KAS
SHORT TERM...JMW
LONG TERM...GREIF
AVIATION...KAS
Area Forecast Discussion
National Weather Service Memphis TN
855 PM CDT Sat May 20 2017
.DISCUSSION...Surface analysis this evening places a surface
low over Iowa with a cold front extending south over Missouri and
Western Arkansas. Regional WSR-88D radars indicate a majority of
convective activity is occurring well east of the Mid-South over
Middle/East Tennessee and Alabama. A few scattered showers are
occurring along the front in Arkansas. As of 8 PM CDT,
temperatures across the Mid-South are in the 70s at most
locations. Latest HRRR and 00Z WRF indicate potential for any
additional showers and thunderstorms may decrease in coverage as
the cold front moves through the area overnight. At this time,
isolated to perhaps scattered pops still seem reasonable for the
remainder of the night. Will make some adjustments to account for
short term trends.
CJC
&&
.PREV DISCUSSION... /issued 635 PM CDT Sat May 20 2017/
UPDATE...
Updated to include the 00z aviation discussion.
PREV DISCUSSION... /issued 257 PM CDT Sat May 20 2017/
DISCUSSION...
Latest KNQA radar shows that most of the shower and thunderstorm
activity has pushed east ahead of a gust front that pushed through
Memphis this morning. The shower and thunderstorm activity is now
located just east of the Tennessee River and across Northeast
Mississippi. This activity will push further east by sunset. Thus
will significantly reduce POPS across the area. Although, can`t
rule out new development along the cold front that is currently
pushing through Southern Missouri and Northern Arkansas. The
likelihood seems rather low as the atmosphere across Northeast
Arkansas as well as the rest of the CWA has been worked over from
this morning`s activity.
The cold front will push through the CWA tonight into Sunday.
Cooler and drier air will begin to filter into the Mid-South
behind the front. Some redevelopment of showers and thunderstorms
will be possible across areas of West Tennessee near the Tennessee
River and Northeast Mississippi on Sunday. Highs will be in the
mid to upper 70s.
High pressure will settle over the Mid-South Sunday Night into
Monday providing pleasant conditions. Lows will be in the 50s with
highs in the mid to upper 70s.
Another cold front will begin to approach the area by Tuesday. In
addition, a SFC low pressure may develop along the Gulf Coast and
track northeastward into Alabama by Tuesday. As a result, chances
for showers and thunderstorms will begin to occur Monday Night
into Tuesday with best chances occurring across Northeast
Arkansas and Northeast Mississippi.
Much cooler temperatures will filter into the area behind the cold
front. Highs on Wednesday will only be in the upper 60s for the
most of the area as an upper trof is expected to bring light
showers with a possible thunderstorm or two to the region.
An upper ridge will begin to build into the Mid-South by the end
of the week. As a result, a gradual warming trend is expected to
occur from Thursday into early next weekend.
KRM
&&
.AVIATION...
/00z TAFs/
Generally VFR will conditions will prevail through the evening
hours with a few showers developing across the Mid-South. A cold
front will approach the Mississippi River from the west after
midnight, providing a final focus for showers. A few hours of low
stratus will be possible with this boundary, persisting longer
over northeast MS where warm-sector stratus is anticipated.
Conditions should improve by mid/late morning as dry air advects
into the Mid-South. Generally south winds at 5-8 kts will veer
northwesterly at up to 10 kts once the front passes.
Johnson
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...None.
MO...None.
MS...None.
TN...None.
&&
$$
Area Forecast Discussion
National Weather Service Miami FL
726 PM EDT Sat May 20 2017
.AVIATION...
VFR expected to prevail through the period. Best chances for
convection on Sunday will be at APF where a Gulf sea breeze is
expected to develop by early Sunday afternoon. Otherwise, easterly
to southeasterly flow will continue at the east coast terminals.
&&
.UPDATE...
Latest visible satellite imagery shows mostly clear skies with a
few fair weather cumulus and scattered patches of cirrus. NWS
radar is quiet this evening with dry conditions prevailing. Brisk
east winds are expected to continue overnight along the Atlantic
coast with light winds for the interior. Other than loading in the
latest short term wind guidance, and updating the sky grids to
lessen cloud cover, all other variable appeared on track.
&&
.PREV DISCUSSION... /issued 444 PM EDT Sat May 20 2017/
DISCUSSION...
Through Sunday: A large dome of upper level high pressure can be
observed on water vapor imagery stretching from the mid Atlantic
coast to Bermuda. The 1018 mb surface high is sitting stagnant,
beneath this feature. Clockwise motion around the high continues
responsible for the persistent east southeast winds, mainly 10 to
15 mph. As noted on this mornings sounding, there is an extremely
dry layer in the mid levels. This can be traced back to a Saharan
dust layer, originating from Africa, advected in from the
southeast flow. During the summer months, the SAL typically
suppresses cloud cover and convection, as is the case today. Short
term models, including the HRRR and Hi-Res WRF, show just enough
moisture and instability to squeeze out an isolated shower or
storm in along the Gulf Coast this afternoon. Otherwise, expecting
dry conditions for the remainder of the CWA. Tonight, as diurnal
heating ceases, so should the chance of precip. East winds may
still be brisk along the Atlantic beaches, around 10 mph, but
light elsewhere. On Sunday, synoptic conditions will be nearly
identical as today, along with the SAL layer. Therefore, expecting
similar weather to ensue. Surface high pressure will still reside
to the northeast, with breezy easterly flow developing. The best
chance of showers/ isolated thunderstorms will once again be over
the northern interior and Gulf coast region. Maximum temperatures
are forecast near normal for this time of year, upper 80s along
the east coast metro and around 90s further west.
Early to mid next week: Monday marks the beginning of synoptic
pattern change. The GFS and ECMWF both begin to sag a long wave
trough over the southern CONUS. This feature will push the
aforementioned surface high eastward, weakening the flow across
southern Florida. Weaker flow will allow for both the Gulf and
Atlantic coast sea breezes to develop in the afternoon, creating
convergent lift. Showers and storms, however, still appear to be
limited to the central and northern interior with dry conditions
along the coasts. As the week progresses, however, the front will
edge closer and weaken. Wednesday/Thursday, as the flow turns
more southerly, then southwesterly, deeper moisture will advect
northward from the northern Carribean. As the atmosphere
destabilizes, chances of showers and thunderstorms steadily
increase during this time frame. The GFS pushes the front across
the area late Thursday into Friday, but the ECMWF stalls the
dieing front over South Florida. Still nearly a week out,
confidence of timing remains low.
MARINE...
This weekend, surface high pressure near Bermuda will maintain
brisk east to southeasterly flow. As a long wave trough begins to
approach Florida early next week, the flow will subside and become
more southerly. The chance of showers and thunderstorms will
increase by mid next week as moisture deepens over the area. Waves
will generally be 3 feet or lower through the period.
BEACH FORECAST...
This high risk of rip currents continues through Sunday evening
along the Atlantic Beaches, as breezy easterly winds prevail.
&&
.PRELIMINARY POINT TEMPS/POPS...
West Palm Beach 77 87 74 88 / 20 20 10 10
Fort Lauderdale 78 87 75 86 / 10 10 10 10
Miami 77 88 75 88 / 10 10 10 10
Naples 73 90 72 88 / 10 30 40 30
&&
.MFL WATCHES/WARNINGS/ADVISORIES...
FL...High Rip Current Risk through Sunday evening for FLZ168-172-173.
AM...None.
GM...None.
&&
UPDATE...27/JT
AVIATION...02/RAG
Area Forecast Discussion
National Weather Service Marquette MI
643 PM EDT Sat May 20 2017
.SHORT TERM...(This evening through Sunday)
Issued at 413 PM EDT SAT MAY 20 2017
WV imagery and RAP analysis indicated a mid/upper level trough
through the plains with a well-defined shortwave over ern Nebraska.
At the surface, low pressure was located over wrn IA with a warm
front through cntrl IL. 300k-305k(800-650mb) isentropic lift ahead
of the shrtwv and low supported a large area of rain from srn MN
through cntrl WI that was lifting slowly northward. Very dry low
level air ahead of the rain area has delayed the progress of the
pcpn into Upper Michigan.
Tonight into Sunday, expect the pcpn to gradually spread through
Upper Michigan btwn 21z-00z with the main area lifting north of the
area after 03z. As aggressive mid level dry slotting moves in
overnight, the rain should diminish to drizzle as lower level 285k-
295k (900-800mb) isentropic continues. As the shortwave approaches
Upper Michigan btwn 09z-15z with stronger qvector conv and steeper
mid level lapse rates, expect another period of showers with some
isold tsra possible. The pcpn should then diminish during the later
morning into the afternoon with even a few peeks of sun possible as
drier air movesino from the west. However, some additional wrap-
around shra may move into the west late. Temps will recover into the
mid and upper 50s .
.LONG TERM...(Sunday night through Saturday)
Issued at 258 PM EDT SAT MAY 20 2017
Overall forecast highlights include a cooler start to the week with
periodic chances for rain showers as cut off energy lingers across
the Upper Great Lakes region. Towards the end of the work week
temperatures will begin to warm back up to near normal for this time
of year with minimal chances for precipitation. We could see a few
nights early in the week where overnight lows drop low enough to
possibly warrant frost headlines.
Expect rain showers to linger across the area Sunday night and
through the day on Monday as the surface low lifts northeast across
the area and the main upper-level low remains becomes anchored
across the Upper Great Lakes. If the pressure gradient can maintain
some of its strength across Upper Michigan, Monday could also be a
breezy day. Given the cool and cloudy conditions expected, did bump
afternoon high temperatures for Monday down a bit. This cool and
cloudy weather will continue through Tuesday as a shortwave digs
south across the Upper Mississippi River Valley and brings a
reinforcing shot of cooler Canadian air. Given the lingering cloud
cover and enhanced lift as vorticity maxes dig south across the
area, we could see scattered rain showers linger through the day on
Tuesday. No concerns for thunder through this time period as mid-
level lapse rates only approaching 6.0-6.5C/km at best and the
atmosphere remains stable.
Through the day on Wednesday, skies are expected to finally clear
from west to east, and precipitation chances will come to an end.
The best chance for any additional precipitation during the day on
Wednesday will be across south central and eastern portions of the
area. As the main 850mb low slowly rotates about the Ohio River
Valley, even though we will still be under a modified cooler
airmass, the increasing insolation should allow temperatures to warm
up into the mid/upper 50s across much of Upper Michigan. Thursday
through Friday, as moist and warmer 850mb air pivot back northeast
into the Upper Great Lakes, temperatures will warm back up to near
normal for this time of year. Not expecting any precipitation as
subsidence should be dominant with upper-level heights building
across the region, allowing a narrow area of surface high pressure
to impact Upper Michigan.
Friday night through Saturday, as troughing continues to traverses
and begins to eject out across the west, surface ridging will shift
east of the region and a lee cyclone is progged to develop across
the High Plains. As a result, low-level moisture will try to make a
return to the Upper Great Lakes. There is some uncertainty among the
medium range models in how regards to how quickly this moisture
return will occur, with the GFS being the most robust this far
north. Depending on how much moisture can get this far north, we
could see the return of some thunderstorm activity to the region for
Saturday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 641 PM EDT SAT MAY 20 2017
Rain showers will lift north across the area as low pressure
approaches. Conditions will fall to MVFR at all sites this evening
as the rain becomes more widespread, and as rain begins to taper off
overnight tonight conditions will lower to IFR. There may even be a
period of LIFR conditions at KSAW late tonight in a moist upslope
ese flow.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 413 PM EDT SAT MAY 20 2017
An increasing pres gradient ahead of low pressure lifting toward
Lake Superior will result in strong winds up to 30 kts and a few
gale force gusts to 35 knots. As the low pres passes into Ontario on
Sun and drags a trough across Lake Superior, expect the winds to
diminish and shift to the w-sw by Sun night. Winds under 20 kts
should then be the rule on Mon into Wed as a relatively flat pres
gradient dominates the Upper Lakes.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...JLB
LONG TERM...Ritzman
AVIATION...07
MARINE...JLB
Area Forecast Discussion
National Weather Service Nashville TN
728 PM CDT Sat May 20 2017
.UPDATE...
FOR EVENING DISCUSSION.
&&
.DISCUSSION...
Will opt to continue to slowly clear counties from the watch from
west to east. Over the past hour, strong storms have moved into
the southern Cumberland Plateau with 40 to 50 mph wind gusts.
Thus, will refrain from pulling the entire watch at this time.
Otw, instability levels are on the downswing. Latest Hrrr data
shows a continuation of showers and thunderstorms over our eastern
third. Back to the west, a break is indicated before some
redevelopment occurs just west of the TN river toward 10z.
For the update, will lower pops some but not too much as the main
frontal boundary will continue to reside to our west overnight,
with an increase in proximity with time. No other changes at this
time. Current dewpoints are very close to projected lows, so temps
look ok.
&&
.AVIATION...
00Z TAF DISCUSSION.
Frontal boundary stretches from central MO southward through
central AR. Pre frontal forcing exists in advance of the main
boundary, and this has helped initiate the current convection
across the mid state. Should see a bit of a break aft 08z as this
current convection pulls east. Toward 12z, cigs and vsbys will be
somewhat reduced. Showers will redevelop in the morning, with
tstms again being possible by afternoon as the aforementioned
main frontal boundary reaches our area.
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION......21
AVIATION........07
Area Forecast Discussion
National Weather Service Shreveport LA
1018 PM CDT Sat May 20 2017
.DISCUSSION...
Sct convection continues this evening over portions of extreme Ern
TX/NW LA, generally along a Nwd surging outflow bndry that is
intersecting a weak and shallow cold front analyzed from near a
HOT, to TXK, to just E of GGG, to JSO and CLL line as of 03Z.
Moderate MLCapes of 1500-2000 J/KG remains over these areas, but
storm intensity should continue to diminish as instability wanes
overnight. The short term progs are all over the place with
whether or not convection will continue or not, with the HRRR
initializing best with the ongoing convection, and actually
expands it E across much of N LA along/just ahead of our cold
front overnight as the front drifts SE through the remainder of
the area, exiting the region by/shortly after daybreak Sunday. The
00Z NAM is quite aggressive with convection exploding by 06Z but
appears tied to feedback issues, but the latest water vapor
imagery suggests a weak shortwave over Cntrl TX which is driving
isolated convection development NW of LZZ, with this shortwave
moving over the region late tonight/Sunday morning. Even as the
shallow front slips SE overnight, the H850 trough will still lag
the front a ways, and could still focus at least isolated to sct
redevelopment mainly SE of the I-30 corridor of NE TX/SW AR as
well as N LA.
Have made some minor adjustments to pops tonight in the forecast
update, mainly to lower pops slightly over NE TX and remove them
over SE OK/adjacent SW AR N of the H850 trough. Did maintain mid
chance pops over much of lower E TX/N LA for the ongoing
convection, and potential for additional redevelopment late with
the arrival of the Cntrl TX shortwave and outflow bndrys still
building back N across SE TX near/W of LFK. Also raised min temps
a bit overnight as well, as cold advection will be shallow, and
the 02-03Z temps/dewpoints are not cooling as fast as earlier
forecast closer to and N of the I-30 corridor.
Zone update already out...grids will be available shortly.
15
&&
.PREV DISCUSSION... /issued 810 PM CDT Sat May 20 2017/
AVIATION...
For the ArkLaTex, a weak cold front is nudging in across E TX, NW
LA and S AR. KLFK on the worse end with recent svr tstm. Convection
is going to linger S of I-20 due to fropa later. Overall, we had a
busy morning and just have not fully recovered area wide limiting
coverage, but some shwrs will be in and out of terminals overnight
and amendments may be necessary for tstms. Sfc winds bcmg N. Climb
is NW10KT, but quickly SW/W 20-50KT into flight levels. Otherwise
this front will lift back soon with more convection into new week.
/24/
&&
.PRELIMINARY POINT TEMPS/POPS...
SHV 67 80 62 75 / 40 30 20 50
MLU 68 81 63 75 / 40 40 20 50
DEQ 57 80 56 79 / 10 10 10 20
TXK 62 79 59 76 / 20 10 10 30
ELD 64 78 58 77 / 30 20 10 30
TYR 63 79 62 76 / 30 20 30 50
GGG 65 79 61 75 / 30 20 30 50
LFK 67 83 66 76 / 40 50 30 60
&&
.SHV WATCHES/WARNINGS/ADVISORIES...
AR...None.
LA...None.
OK...None.
TX...None.
&&
$$
15
Area Forecast Discussion
National Weather Service San Angelo TX
703 PM CDT Sat May 20 2017
.AVIATION...
/00Z TAFS/
VFR conditions will persist across the terminals through the
evening hours. Stratus will develop across the southern terminals
late tonight, with MVFR ceilings expected into the morning hours.
Scattered showers and a few thunderstorms are expected to develop
towards daybreak across the southern terminals and linger through
much of the day. Thunder chances may increase by afternoon but
due to coverage uncertainties, will only mention VCTS during the
afternoon hours at this time.
&&
.PREV DISCUSSION... /issued 347 PM CDT Sat May 20 2017/
SHORT TERM...
(Tonight and Sunday)
Moist air overrunning the cold front will likely allow the
development of isolated to scattered showers south of Interstate 20
tonight and Sunday. Texas Tech WRF and HRRR indicate a few showers
developing along the I-10 corridor late this evening, spreading
north to the Concho Valley toward morning.
An isolated severe thunderstorm is possible...Sunday afternoon and
evening along and south of the I-10 corridor, where GFS MUCAPES
range from 1000 to 1200 J/KG along with moderate 0-6 KM shear values
of 35 to 40 KTS. An upper shortwave moving east across the Big Bend
and northern Mexico will also increase the potential for storms
Sunday afternoon, particularly in Crockett country. Lows tonight
will range from lower/mid 50s in the Big Country where clear skies
will mainly prevail, to upper 50s to lower 60s to the south where
developing stratus will limit cooling. Temperatures will stay cooler
Sunday. Highs Sunday will range from the upper 70s to lower 80s in
the Big Country to lower/mid 70s farther south where stratus limits
surface heating.
LONG TERM...
(Sunday Night through Saturday)
Unsettled pattern continues into early next week. Low level
moisture will surge northward Sunday Night and Monday as the front
to the south dissipates. With abundant cloud cover, instability
will be somewhat limited on Monday. Cap will be weaker as well
however, so scattered showers and thunderstorms continues to look
possible. Cold front will slide through West Central Texas late
Monday Night into Tuesday morning, bringing a focus for additional
showers and storms. Drier air mass follows the front, ending the
precip chances for the remainder of the week.
Cloud cover will keep temperatures down to around 80 degrees for
Monday, with the front and more cloud cover keeping readings even
a few degrees cooler for Tuesday. Warm up starts mid week
however, with afternoon highs pushing towards the upper 80s on
Thursday and then into the lower 90s for Friday.
&&
.PRELIMINARY POINT TEMPS/POPS...
Abilene 56 78 59 78 / 10 10 30 40
San Angelo 59 75 60 80 / 30 40 40 30
Junction 63 75 62 81 / 40 40 60 40
Brownwood 57 77 59 77 / 20 20 40 40
Sweetwater 55 77 58 78 / 5 10 20 40
Ozona 60 73 61 81 / 40 50 60 30
&&
.SJT WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
99/99/24