Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/20/21
Area Forecast Discussion
National Weather Service La Crosse WI
1000 PM CDT Wed May 19 2021
.SHORT TERM...(This evening through Thursday)
Issued at 235 PM CDT Wed May 19 2021
Forecast concerns will be shower and thunderstorm chances along
with temperatures and winds.
The water vapor satellite imagery, heights, and lightning show
the closed low over Colorado/New Mexico has had very little
movement, just a slight southeast drift. Lightning was most
prevalent over southern Texas and also closer to the closed low
over northwest Texas.
Tuesday`s rainfall was highly variable. Many locations picked up
a trace to a third of an inch. Some locations received .40 to .75.
New Hampton had 0.75", Platteville had 0.46" and Steuben had
0.42". Locally, RST reported 0.18", LSE 0.08", and here at the La
Crosse NWS, we had a storm total of 0.14". At 1745Z...Clouds still
covered the region with temperatures in the 60s to around 70. The
WSR-88D radar mosaic showed a few showers, especially over parts
of western Iowa. Visible satellite imagery highlighted some
decreased cloud cover over southwest Iowa with heating and more
convective looking clouds near a weak 500mb vorticity maximum. not
showing a lot on radar at 1745Z, however a few echoes starting to
show up.
Today and tonight, we remain under the influence of the 500mb
trough that is migrating northeast from the Oklahoma Panhandle
northeast into southern Canada/northwest Minnesota. Ripples of
shortwave trough energy will lift northeast in the southwest flow
aloft combined with increasing moisture transport vectors this
afternoon and tonight. This initial moisture surge purchases east
into northeast Wisconsin through 18z Wednesday as another push of
moisture develops to our west and increases locally Wednesday
afternoon. We don`t have a boundary to focus on, so this makes it
a little more difficult to time and place shower and thunderstorm
chances. The 900mb winds increase to 30kt over the southern
portion of the forecast area by 00Z with 40 to 50kt wind by 06Z in
addition, as the upper level trough moves north...we see the
showers and thunderstorms push farther east across the forecast
area. Will maintain chance for showers on and off through Thursday
with higher pops over the western portions of the forecast area
tonight and early Thursday. Forecast soundings show some SBCAPE of
1000 late this afternoon with a pocket of stronger 30 to 35kt
effective shear. Should thunderstorms develop, they could contain
some small hail. This wave of showers and thunderstorms lifts
north per the HRRR by around 03Z with additional activity moving
in after 07Z. The instability has decrease and although there is
25 to 30kts of deep layer shear it is unidirectional. Mid day
Thursday forecast sounding per the RAP are still modest less than
500 on the SBCAPE with deep layer shear around 25kts. The NAM has
more deep layer shear 30-40kts. The NAM has instability of 500 to
1000 J/kg. SPC has us in the marginal outlook for Thursday, so
will want to keep an eye on the mesoscale related to shear trends
and differential heating Thursday. Temperatures should again be in
the 70s Thursday.
.LONG TERM...(Thursday night through Wednesday)
Issued at 235 PM CDT Wed May 19 2021
The parade of short wave troughs into the region in the southwest
flow aloft looks to continue for the remainder of the work week.
The 19.12Z guidance is in good agreement in bringing a wave across
the area Thursday night into Friday morning, generally tracking
from eastern Kansas toward the western tip of Lake Superior. The
forcing from the wave itself does not look to be all that strong
with just some very weak pv advection in the 500-300 mb layer
shown as of now. However, the low level moisture transport does
increase ahead of the wave and looks to be focused into or just
northwest of the area along an incoming weak surface boundary. An
axis of ML CAPE (250-500 J/kg) looks to overlap the moisture
convergence from the moisture transport with warm cloud depths
increasing into the 3.5 to 4 km range. This would suggest the
showers and a few storms should be efficient rain producers and
with precipitable water amounts around 1.75 inches, some decent
rains could occur. Model QPF output is showing an axis of at least
a half inch over parts of the western area with the 19.00Z ECMWF
even suggesting some six hour amounts up to an inch possible.
Given the recent dry conditions, would expect that this rain could
be readily absorbed by the ground with no concerns for any
flooding at this time.
The main storm track then looks to get a gentle nudge to the
northwest as the Atlantic upper level ridge retrogrades back into
the Ohio River Valley and parts of the Midwest. The rain chances
won`t be completely pushed out of the area, but far enough that
just the northern parts of the area could get some activity
Saturday into Sunday morning. The retrograding of the ridge will
help to bring in some warmer air with temperatures at 850mb
reaching into the 16C to 18C range late this week into the
weekend. While this is not that much out of the ordinary, only
about 1 standard deviation above normal, the combination of the
warmer air and higher dew points, may not allow for much cooling
to occur at night. Overnight lows could be warm enough to approach
or set some new records for warmest low temperatures both Friday
and Saturday mornings.
The upper level ridging looks to get flattened starting Sunday
afternoon as a short wave trough tops it. The upper level low in
the western trough will also be lifting northeast and is expected
to reach southern Canada sometime Monday or Monday night. While
the southwest flow will not be as amplified, it will persist with
more short wave trough expected to be embedded in it. A surface
boundary looks like it should set up over the region Sunday
afternoon and remain in the vicinity into early next week with the
models showing some divergence on placement and timing of this
feature. The end result will be a return of the more widespread
rain chances starting Sunday afternoon. The rain chances should
then continue into early next week but with decreased confidence
on what the eventual coverage will be.
&&
.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1000 PM CDT Wed May 19 2021
Persistent upper level pattern with steady influx of low level
moisture will keep ample low clouds with occasional showers and a
few storms the result - at least into Fri.
Cigs: low clouds are progged to develop/advect in from the south
overnight, with IFR/MVFR expected. The low cigs will hang through
the morning, but could see a bump back into VFR for a few hours in
the afternoon - similar to what happened on Wed. NAM supports this,
but the RAP/HRRR rather keep the low clouds. Going to hold onto the
low clouds for the moment and monitor trends.
WX/vsby: most showers tied to upper level features, and will tie
pcpn chances to timing those through the region. Weak instability
will support some thunder chances later Thu afternoon/early evening.
Winds: Southeast becomes more southerly early Thu morning. Mostly
10+ kts through the period with some higher gusts during the daytime
hours.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...Zapotocny
LONG TERM...04
AVIATION...Rieck
Area Forecast Discussion
National Weather Service Dodge City KS
546 PM CDT Wed May 19 2021
...Updated Aviation Discussion...
.SHORT TERM...(This evening through Thursday)
Issued at 134 PM CDT Wed May 19 2021
An Upper level low/trough was centered over northeast New Mexico
earlier this Wednesday morning based on UA observations and WV
loop. Models remain in good agreement today with this upper
low/trough weakening as it slowly lifts east northeast over the
next 24 hours across western Kansas and the Panhandle of
Texas/Oklahoma. Several upper level waves will rotate around this
system and with each disturbance there will be a chance for
showers and thunderstorms. At this time based on the latest RAP
and GFS PV it appears that the best chance for precipitation will
occur early this afternoon today (Wednesday) and then again this
evening, especially between 00z and 06z Thursday. Severe weather
is not expected from these storms but much like last night
isolated heavy rainfall will be possible, especially east of a
Garden City to Liberal line given the high precipitable water
values. 0-6km shear of around 30knots early this evening may also
produce isolated areas of hail up to the size of quarters. NAM
BUFR soundings also suggest another morning of fog given the light
southeast winds and moisture profiles in the surface to 1000ft
AGL.
As the upper level trough moves towards Nebraska during the day
on Thursday the skies will begin to clear. Temperatures should
rebound back into the 75 to near 80 degree range Thursday
afternoon given the sun breaking out and the 21z Thursday/00z
Friday forecast temperatures near the top of the mixed layer
(around 800mb). Later shifts may need to monitor the potential for
an few isolated high based thunderstorms late Thursday/Thursday
evening near the Colorado border given the forecast low level
lapse rates, near zero CIN and mid level moisture ahead of what
appears to be a weak upper level wave. Further east a 500mb
deformation zone will set up Thursday across central Kansas. GFS
shows a weak upper wave approaching from the south during the
afternoon which may provide enough lift for some isolated to
scattered convection over south central Kansas as far west of
Pratt and Medicine Lodge.
.LONG TERM...(Thursday night through Wednesday)
Issued at 134 PM CDT Wed May 19 2021
On Friday a surface trough will continue to develop across
eastern Colorado with a southeasterly flow advecting higher low
level moisture back into the West Central High Plains. At the
same time an upper low will be briefly establishing itself over
California/Nevada as multiple waves rotate around this upper low.
As each of these upper waves cross the West Central High Plains
over the weekend period there will be a chance for thunderstorms,
especially across far western Kansas. These waves will be embedded
in a southwest flow of tropical moisture given the high 300mb RH
and source region of this moisture. Heavy rainfall will be
possible from these storms over the weekend period. Hail and
strong winds will also be possible from a few of these storms.
The GFS and ECMWF remains in good agreement with this upper low
becoming negatively tilted as it lifts northeast across the
Rockies late this weekend and early next week. The track keeps the
better dynamics just to our west as it crosses the Central
Rockies. Confidence is improving on this solution given the latest
high positive NAEFS height probability of extremes over the
western great lakes region this weekend which favor a further west
solution of the upper low and upper low/trough track. This will
not remove the chance for strong or even severe thunderstorms
across southwest Kansas early next week but will lower the
possibility of widespread severe. Heavy rainfall still will be an
issue from storms through early next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 537 PM CDT Wed May 19 2021
VFR conditions to start the TAF period as thunderstorms push out
of the Texas and Oklahoma panhandles. All but HYS should see some
storms near station, but being hit or miss, only carried VCTS
during the 01-04Z timeframe. Otherwise, expect southeast winds to
continue through most of the period before picking up out of the
south gusting up to 25kts after 18-19Z as the gradient tightens
with a deepening surface low to the southwest. Ceilings down to
4kft with the storms before lifting to the mid levels with the
aforementioned stronger winds increasing the mixing near the
surface. MVFR ceilings possible for HYS with ample moisture and
light upslope winds from the east to southeast. No other weather
elements expected at this time.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 56 77 61 81 / 60 10 10 10
GCK 54 79 60 81 / 60 10 10 10
EHA 52 81 58 83 / 20 10 10 10
LBL 53 81 58 82 / 60 10 10 10
HYS 58 77 62 81 / 20 10 10 10
P28 60 77 63 80 / 40 10 10 20
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Burgert
LONG TERM...Burgert
AVIATION...Lowe
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1201 AM EDT Thu May 20 2021
.AVIATION...
Extensive mid level cloud will persist overnight, with skies
remaining clear across the lowest 7k ft. Modest winds prevailing
from the south to southeast overnight. Warm and stable conditions
will exist on Thursday as the area remains within the influence of
strong upper level high pressure. This ensures any diurnal cloud
development remains very high based /above 7k ft/. Winds persisting
from a southerly direction throughout Thursday.
.DTW THRESHOLD PROBABILITIES...
* None
&&
.PREV DISCUSSION...
Issued at 331 PM EDT Wed May 19 2021
DISCUSSION...
Summer-like pattern resumes across the greater Great Lakes region
where temperatures now reside in the lower 80s, with plenty of upper-
level clouds now starting to stream in from the better upstream
moisture connection and rain activity across the Midwest. Upper-
level low across the Pacific northwest and enhanced troughing over
the western Atlantic will continue to provide an open Gulf
connection, with greatest axis of moisture funneling in across
western Michigan and further west into the Dakotas, as seen in MIMIC-
TPW precipitable water imagery. Building heights throughout the
afternoon and a weaker connection to the ongoing moisture advection
will continue to limit shower and thunderstorm potential over the
cwa. However, will continue to advertise the chance for isolated
development over the cwa, with greater odds over the western half of
the cwa, tied to very subtle surface troughing/low-level convergence
& daytime heating. Limiting factors for precipitation, other than
lack of synoptic support, will be weaker mid-level lapse rates, poor
shear, and shallower convective depths with HRRR and RAP runs
developing a weak late-day cap between 10-12kft. HREF ensemble mean
and internal probabilistic data cap CAPE values between 250-500 J/kg.
Aforementioned troughing across the western Atlantic will strengthen
and develop into a closed low while retrograding west, with the
secondary closed low across the northwest Pacific set to drop south
across the western coast stating late tonight and through the end of
the week. This will set up an omega blocking pattern and will result
in increasing heights across the Great Lakes through the end of the
week. 12Z DTX raob recorded h850 and h700 height values above the
max moving average per the SPC climatology sounding page (h500
approaching max moving average), and latest NAEFS and EPS ensemble
data projects record height values that fall outside of all
climatological data values for Thursday and Friday between h850 -
h500. ECMWF deterministic data shows h850 and h500 height values
around 163 dam and 590 dam respectively, by 12Z Friday. This will
result in continued limited precipitation chances as better moisture
axis holds across the Midwest along the western periphery of the
ridge axis. Warmer temperature will arrive with the increasing
height trends, with above normal temperatures continuing through
Sunday. Record high minimums will be challenged Friday into Sunday
morning (lows in the mid to upper 60s), while weekend highs in the
upper 80s could challenge the record (pending cloud and convective
trends), especially for the Metro region. Better chances for rain
and thunderstorms do exist over the weekend as height fields start
to lower, with additional support from a series of shortwave
troughs.
Higher uncertainty regarding precipitation and temperature trends
exists next week, especially on Monday as the blocking pattern
starts to break down. The western Pacific low will weaken while
heading northward into Montana and the Dakotas which will work to
flatten ridging across the Midwest through early next week. A
baroclinic zone will work its way in the vicinity of Michigan on
Monday in response, while shortwave troughs ripple across the region,
which will bring lowering temperature trends and additional chances
for precipitation through early next week.
MARINE...
The central Great Lakes will continue to reside on the western
periphery of a broad area of high pressure centered over the mid-
Atlantic, with winds gradually rotating from SE to SW throughout the
remainder of the week as the high gradually expands to the west.
Wind gust potential will be limited as a warmer air mass aloft and
cooler lake temps at the surface work to stabilize the marine
boundary layer and limit mixing depths. As such winds generally
remain below 15 kts, although slightly stronger gusts are possible
during the afternoon/evening hours today and tomorrow. Favorable
marine conditions are expected to persist through the end of the
work week with light winds, calm waves, and generally dry
conditions, although potential remains for an isolated shower/tstm
this afternoon and evening.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&
$$
AVIATION.....MR
DISCUSSION...AM
MARINE.......MV
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Grand Forks ND
911 PM CDT Wed May 19 2021
.UPDATE...
Issued at 911 PM CDT Wed May 19 2021
A broken line of shower and thunderstorm activity continues along
a Jamestown to Cooperstown to Oslo to Warroad line. There is
another area of showers and storms lifting through the Twin Cities
into east central Minnesota. In between the two areas, there is no
precipitation. Still do not have a really good handle on what will
happen overnight with these two areas. Some models linger the
Jamestown to Warroad line about where it is, then lift the east
central Minnesota activity just east of this FA, with only spotty
showers in between the two areas. Other models show expanding
activity between the two areas after midnight. All said, think the
overall chances and coverage of precipitation tonight will be
disappointing to those who wanted rain, as it is looking more
spotty than widespread. However, there are multiple chances
throughout the late week and weekend yet.
UPDATE Issued at 659 PM CDT Wed May 19 2021
This evening`s showers and storms started up as expected, but the
frontal boundary is stalling out. Not seeing a lot of additional
activity anywhere else, so what rain there is is falling in only
a few select areas. Eastern Eddy County in North Dakota has seen
over an inch of rain, but the rainfall has been spotty. Most
models show a lot more activity right now than is occurring, which
translates into a low confidence rainfall forecast into tonight.
The models have been showing another wave lifting up overnight,
which should bring some more precipitation, but when and where is
pretty hard to say right now. To start off, have trimmed most
shower and storm activity to where it has been, and dropped it
for other areas through mid to late evening. Will be watching to
see what happens over the next few hours. Other than that, the
strong to severe storm threat is pretty much done, much like it
was at this time yesterday, when the boundary was in eastern
Montana.
&&
.SHORT TERM...(This evening through Thursday night)
Issued at 311 PM CDT Wed May 19 2021
Initial wind shift boundary separating south wind from more west
or northwest wind is from east of Winnipeg to just wests of
Hallock (near St Thomas ND) to just west of Grafton then to east
of New Rockford then to west of Jamestown.
The first boundary is seeing sct t-storms along it at 19z, a tad
earlier than what HRRR showed. Will expect the boundary to move a
tad east thru the evening but unsure how far east as most model
runs keep winds south at GFK til near 06z. T-storms will be psbl
along the boundary. The northern end in Manitoba is moving faster
east than the ND section.
Meso analysis shows sufficient instability for t-storms to form
along the boundary with MU CAPE values progged to be around 2000
j/kg and atmosphere is not capped. 0-6 km bulk shear is very weak
though and therefore a more multi-cell storm mode is likely with
lack of sustained storm updrafts. Therefore large hail is not
likely. As storms form along the boundary and form a line, an
organized outflow may develop and in this case produce wind gusts
over 50 kts (58 mph). McHenry 8N NDAWN had wind gust to 42 mph as
storms were overhead. The best area for sfc vorticity remains from
Cavalier to Bismarck and in this zone the non supercell tornado
parameter is around 2 and is progged to be around 3 in spots, esp
Jamestown region at 00z. So as been messaged, some risk for brief
spin ups, funnels, with these storms. LCL levels around 4000 ft.
Overnight into Thursday will see continued moist advection as
front slowly sags east and south before it stalls out thru the
middle of the fcst area. One 500 mb wave will lift north Thursday
and should produce a pretty widespread shower and t-storm event.
.LONG TERM...(Friday through Wednesday)
Issued at 311 PM CDT Wed May 19 2021
The extended period is marked by rain chances and cooler
temperatures. Showers and thunderstorms will be possible into mid-
week next week, and some strong storms possible as well.
A frontal boundary is expected to remain draped across the region
through the weekend, allowing systems that move through to interact
with it and cause pop-up showers and thunderstorms. Instability
remains a slight concern, although on the low end (~1000J/kg).
However, Gulf moisture is surging through the region, making PWATs
above normal for this time of year and QPF greater than half an inch
possible but on the less likely side for the Red River Valley and
east into Minnesota.
Heading into the beginning of the week, a jet streak ahead of an
upper low begins to affect eastern North Dakota and northwestern
Minnesota. A ridge in the southeastern United States will hold
strong, forcing a low pressure system to camp out in the western
US until the ridge weakens into Monday. Ensembles are not in
agreement as to whether this low will remain closed or become
absorbed in the jet stream as it pushes into Canada. What we do
know is with the movement of this system across North Dakota, we
get more chances for rain, and some cooler air coming our way as
well. Confidence is low in terms of precipitation amounts,
severity, and other impacts, but these will become more known as
the system comes into range of the CAMs.
Temperatures for the long term will drop with the initial cold
front, with Sunday seeing highs in the low 60s and 70s, and they
will not get a chance to rebound much before cold air due to that
traversing low becomes present mid-week next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 659 PM CDT Wed May 19 2021
So far, any shower and storm activity has missed the TAF
locations. Confidence is low on what happens over the next 3 to 6
hours, as well as overnight. For that reason, have removed most of
the mention of precipitation from the TAFs for most of the
evening, then showed a chance again late tonight into Wednesday
morning (as another wave lifts into the FA). The only other thing
of note is that guidance is showing MVFR ceilings developing
again overnight into Wednesday, with some fog around the area. Did
not mention any fog, but did go with the MVFR idea. Wind speeds
will lower after sunset, and then should be much lower thereafter.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
$$
UPDATE...Godon
SHORT TERM...Riddle
LONG TERM...AK
AVIATION...Godon
Area Forecast Discussion
National Weather Service Marquette MI
736 PM EDT Wed May 19 2021
.SHORT TERM...(This evening through Thursday)
Issued at 425 PM EDT WED MAY 19 2021
Water vapor imagery and RAP analysis indicate an amplified pattern
with a mid/upper level ridge over the Ohio/TN River Valleys and a
trough over the west. A moist sw flow between these features will
result in more moist and at times unsettled weather over the
northern Great Lakes into Thursday. Above normal temps will
continue.
Into this evening, scattered light shower activity will continue
late afternoon into early evening mainly over the east half of the
U.P. but at the same time rising 5H ridge heights and associated
increasing subsidence as noted on fcst soundings should lead to
a lull in shower activity and drier conditions into this evening.
Late tonight into Thursday, models suggest a series of weaker
shortwaves moving through the area which will lead to increasing WAA
and deepening moisture/increase in PWATs, which in turn will lead to
increasing chances of rain, mainly across the western half of the
cwa which will be closer to the track of the shortwaves. NAM fcst
soundings show quite a bit of instability (500-1000 j/kg at some
locations) during the day on Thursday, but gut feeling is this is
overdone as there will be quite a bit of cloud cover. GFS
soundings indicate more minimal instability which looks more
reasonable based on cloud expectations. Expect only slight chances
for thunder over the west half Thu afternoon.
Min temps tonight will be mainly in the 50s, except for a few
readings near 60F over the west and perhaps a few upper 40s readings
near Lake Mi southeast. Highs Thursday under clouds should be mostly
in the lower 70s with perhaps a few mid 70s readings west. Cooler
readings in the 60s will occur downstream of Lake Mi in southerly
flow.
.LONG TERM...(Thursday night through Wednesday)
Issued at 342 PM EDT WED MAY 19 2021
Amplified pattern with ridging over the eastern CONUS with troughing
over the western US is expected to continue in the extended,
allowing for multiple rounds of showers and thunderstorms through
the weekend and into next week. The ridge is progged to retrograde
westward to the eastern Plains for the remainder of012 this week,
allowing for continued warm and humid conditions. By late in the
weekend, models suggest the mid-level high will sink toward the
southeastern US through the early part of next week, which will
allow the upstream trough to open the pattern into zonal flow over
the region. This looks to unlock some cooler conditions on Sunday,
before returning back near normal to above normal Monday and Tuesday.
The region will maintain its position relative to southwesterly
flow, allowing for another shortwave to progress northward through
the region Thursday night and Friday. With this shortwave, a wave of
theta-e advection and isentropic lift will support another round of
showers. CAPE among the guidance varies, but generally tops out at
500 j/kg. Given this, I wouldn`t be surprised if a few thunderstorms
develop. This shortwave is progged to continue moving through the
region Friday, allowing for continued chances of showers and
thunderstorms. With CAPE increasing to 800-1200j/kg, expecting a
better chance for thunderstorms during the afternoon hours. With the
cloud cover, warm airmass and PWATS of 1.5 to 1.75 inches, expect it
to be warm and humid. Lows Thursday night should bottom out near 60F
with some low-mid 50s being possible in the east and the northern
tip of the Keweenaw. Friday, widespread 70s to near 80F in the west
half, mid 70s in the east except 60s by Lake Michigan and dewpoints
in the 60s will certainly make it feel like summer.
The mid-level high is expected to drop a little south overnight
Friday into the middle-Mississippi River Valley and then southeast
toward Florida late in the weekend. With this change, we`ll
transition to a period of zonal flow over the region by Saturday,
with ridging returning Sunday behind a shortwave late Saturday into
Sunday. This shortwave looks to kick off another round of showers
and thunderstorms. Early next week, models are queuing in on an upper
level low ejecting out of the upstream trough and progressing
eastward into the northern Plains. By late Tuesday, this low looks
to regress into an open wave as it moves eastward through the Upper
Great Lakes.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 736 PM EDT WED MAY 19 2021
Challenging fcst shaping up for the next 24+hrs. With moist upslope
southerly winds at KSAW, there is higher confidence in the fcst at
KSAW. IFR conditions should prevail at KSAW tonight with improvement
to MVFR Thu morning, though that could certainly be delayed until
aftn. Not out of the question that conditions could fall to LIFR
during the night. There could be a few -shra as well during the fcst
period, but timing is very uncertain attm. At KIWD, downsloping
southerly wind should allow VFR conditions to prevail thru the
evening. MVFR conditions and periodic -shra should return overnight
and continue for the remainder of the fcst period. At KCMX, VFR
conditions should prevail for much of the night. Expect MVFR
conditions and potential of -shra at times from early Thu morning
thru the aftn.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 425 PM EDT WED MAY 19 2021
Other than a few gusts approaching 25 kts this evening along the
eastern Superior nearshore zones, expect winds 20 knots or less
through much of the fcst pd. With higher dew points moving in for
the rest of the week, and multiple chances of rain expected between
now and the weekend, Areas of fog are expected to develop and then
persist for several days and just drift around the lake. There`s a
good bet it will be dense at times. Have a dense fog advisory in
effect into this evening for LSZ162.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
Dense Fog Advisory until 8 AM EDT /7 AM CDT/ Thursday for LSZ162.
Lake Michigan...
None.
&&
$$
SHORT TERM...Voss
LONG TERM...JP
AVIATION...Rolfson
MARINE...Voss
Area Forecast Discussion
National Weather Service Phoenix AZ
440 PM MST Wed May 19 2021
.UPDATE...00Z Aviation Discussion.
&&
.SYNOPSIS...
High temperatures will top out near 100 degrees today
under sunny skies and then cool into Friday as a strong weather
system digs into the central part of the western U.S.. Friday and
Saturday will be the coolest days with highs only reaching the mid
to upper 80s most places. Very breezy to windy conditions will also
develop each day through Saturday. There will be a slight chance for
rain late Thursday into early Friday, but the probability of
receiving measurable rain is very low. Winds relax and temperatures
warm heading into next week.
&&
.DISCUSSION...
Satellite and RAP upper air analysis shows a dry progressive
positively tilted ridge aloft with mostly clear skies across the
lower deserts region. The slow moving closed low pressure system has
moved well off to the east with its circulation now centered near
the NW TX Panhandle. Well to the northwest a positively tilted
closed NE PAC low had begun to dig into the Pacific Northwest. The
high pressure and plenty of insolation today will support a second
day of warming and allow high temperatures to climb to the upper 90s
to low 100s. A high of 101 degrees is forecast for Sky Harbor today
and would be the hottest day in the 7-day forecast period. This
would be our 6th 100 degree day this year.
For the shorter term the deterministics agree on the progressive
ridge aloft ejecting rapidly east today as the next closed low
pressure continues digging and dropping SSEwrd into the W US through
Friday. This ushers in noticeably and relatively cooler temperatures
in time for the weekend with well below normal highs only in the mid-
upper 80s for Friday and Saturday, and upper 80s to low 90s on
Sunday as the low pressure system lingers nearby to the northwest
and gradually weakens.
As the regional gradients tighten over the next few days in advance
of/with this system very breezy to windy conditions will spread
across the area with the strongest winds forecast out west. As a
result a wind advisory remains in effect for parts of SE CA in the
far west CWA. There is also a Red Flag warning for Thursday
afternoon and evening for the Lower Colorado River valley for
critical fire weather conditions developing there. There is also a
fair chance of patchy and lofted blowing dust for SE CA and
perhaps SW AZ.
This system will also bring a slight chance of rain mainly on
Thursday night. However, ensembles keeps our region dry in spite of
a moderate IVT plume and weak disturbance that penetrates S-Cent and
SE AZ from the southwest in advance of the main low. QPF associated
with this system is currently 0. Nevertheless HREF family members
agree on mostly light to occasionally moderate rain, and sometimes
centered more south and east of Phoenix.
However the NAM Nest is the most bullish outlier showing scattered
light-moderate rain with much better coverage further to the
northwest across Phoenix and a large portion of the CWA. Forecast
soundings and HREF CAPE forecasts indicate stable conditions and
almost no CAPE due to the offset position of the low and colder
air displaced well to the NW. Also most moisture is concentrated
in the upper mid levels around 600-500+mb, with the column being
fairly dry below that so the result is low to no QPF for the
Thursday night rain.
The clusters analysis/forecast agree that the low will eject late
next weekend and into early next week towards the northeast into
Montana. As it does heights will recover and high temperatures
will warm back up to near normal in the upper 90s by Mon-Tue.
&&
.AVIATION...Updated at 2340Z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
West-southwest gusts up to 20-25 kts through 03/04Z. After
sunset, winds will subside and gradually transition to an easterly
component between 07-10Z. Tomorrow will see normal diurnal trends
with another increase in speeds by the early to mid afternoon.
There could also be a period of slightly elevated crosswinds,
around 10 kts, as winds transtion from the southeast to
southwest. Skies will stay mostly clear before an increase in
cloud coverage tomorrow. By 16Z, we can expect mid and high
clouds at 180 & 250 to start increasing in coverage, with bkn to
ovc conditions by the late evening.
Southeast California/Southwest Arizona including KIPL and KBLH:
Winds will be the primary aviation weather concern through the TAF
period. At KIPL, westerly winds are anticipated through the TAF
period with gusts commonly reaching 20-30 kts through the early
afternoon tomorrow and then closer to 40 kts by the mid
afternoon. At KBLH, wind directions will mostly favor the south
and southwest through the TAF period. Gusts up to 30 kts, will be
likely through late this evening before speeds weaken a bit
overnight into tomorrow morning. By the mid-afternoon tomorrow,
wind gusts at KBLH will be upwards of 40-45 kts. Areas of blowing
dust could reduce surface visibilities while lofted dust could
create slantwise visibility issues.
&&
.FIRE WEATHER...
Saturday through Wednesday:
Expect well below normal max Ts only in the mid-upper 80s for
Friday and Saturday, and upper 80s to low 90s on Sunday as the low
pressure system lingers nearby to the northwest. Max Ts to then
warm to near normal by/on Mon-Tue. Lingering breezy conditions are
expected on Sat. With very dry fuels, an elevated fire danger is
possible on that day. Min RH levels will stay near 4-8% through
the period. Overnight recovery will be poor, initially around
20-35% Friday night and decreasing to 15-30% for much of the
period.
&&
.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Red Flag Warning from noon to 8 PM MST Thursday for AZZ131.
CA...Wind Advisory until 11 PM PDT this evening for CAZ560-563-566.
Red Flag Warning from noon to 8 PM PDT Thursday for CAZ231.
Wind Advisory until 5 AM PDT Friday for CAZ562.
&&
$$
DISCUSSION...Sawtelle
AVIATION...Feldkircher
FIRE WEATHER...Sawtelle/Benedict
Area Forecast Discussion
National Weather Service Shreveport LA
932 PM CDT Wed May 19 2021
.SHORT TERM...
Well fairly quiet rainy night unfolding with coverage
increasing now in deep east Texas and western Louisiana. Shower
and occasional thunderstorm activity has been slowly pivoting in
southern Arkansas all evening. Our current low to mid 70s will
fall off into the mid to upper 60s by daybreak. So no changes
there, and the HRRR shows good initiation with current activity
modeled to move into much of the Texas counties along I-20 and
I-30 over the next several hours. For now will continue current
flood watch through the night and high pops, with new 00Z models
indicating a wet day for much of our Thursday. So portions of the
watch may be extended in the next zone issuance. Our pwat is down
to 1.5, but will be increasing overnight with saturation aloft. A
weak upper low will form over east Texas and continue to focus
much of the activity in our direction. /24/
&&
.PREV DISCUSSION... /issued 727 PM CDT Wed May 19 2021/
AVIATION...
For the ArkLaTex terminals, an axis of showers with embedded
isolated thunderstorms stretches from KELD to near KAEX, moving to
the NNW at 20KT. S/SE winds will prevail this cycle with 10-15KT
and 20KT gusts. Stronger gusts from S will accompany downpours.
The HRRR model carries this activity to the W with all terminals
being affected by some extent during the overnight hours. Little
change in the pattern this cycle with more convection likely
throughout our Thursday. Fri/Sat are looking better for us. /24/
SHORT TERM.../Tonight through Thursday night/
This evening, showers and thunderstorms will continue to progress
across the southern and eastern portions of our area in the wake of
a decaying MCS shifting out of SW AR. This lingering precipitation
will be reinforced by an upper-level low propagating out of south
TX into north/central TX, ahead of a deep upper-level trough
across the Southern Plains. Some of this precip could be locally
heavy, which may present a continued risk of flash flooding in
areas of already saturated soil. The current Flash Flood Watch
will remain in effect until 7:00 AM Thursday, and is not expected
to be extended further at this time. Will continue to monitor
closely through the evening and overnight.
Continued flow out of the southeast at 5-10 kts will prevail through
the short term period, maintaining an influx of Gulf moisture
keeping dewpoints in the upper 60s to low 70s throughout. Followed
NBM guidance for temperatures, keeping lows in the mid-upper 60s
tonight and highs in the upper 70s to low 80s Thursday afternoon.
The aforementioned upper level trough will remain with us through
the day Thursday, thanks to the upper level ridge to our east
forming a pseudo-Omega block. Thus, precip chances will remain
across the Four-State region through tomorrow night. Made some minor
edits to limit and smooth extremely high/low PoP values. Otherwise
followed NBM guidance. /26/
PREV DISCUSSION... /issued 302 PM CDT Wed May 19 2021/
LONG TERM.../Friday through Wednesday/
The general trend going forward into the weekend will be for warmer
and drier conditions as an upper level ridge across the eastern U.S.
continues to slowly migrate farther westward, but we won`t be done
with convection quite yet on Friday. That`s because our persistent
mid level low to the west will recenter itself down along the lower
TX coast and continue to advect Gulf moisture northward across our
region. As it does, this moisture will combine with diurnal heating
to generate showers and thunderstorms through Friday into Friday
evening before gradually diminishing with loss of heating overnight.
As the upper level ridge axis continues to shift farther west into
our region over the weekend, expect high temperatures to climb into
lower to mid 80s on Saturday and Sunday with rain chances generally
confined to our western zones farther removed from the center of the
ridge axis. However, rain chances will continue to gradually lower
later in the weekend with just slight to low chances PoPs by Sunday
as the ridge axis becomes more influential areawide.
The trend of warmer and near summer-like temperatures will continue
into the first half of next week as moist low-level southerly flow
prevails. Convection should be generally limited to diurnal shwrs
and storms although a weak shortwave and associated cold front will
attempt to approach our region from the Southern Plains and could
aid in convective development by mid week. /19/
&&
.PRELIMINARY POINT TEMPS/POPS...
SHV 69 82 68 81 / 70 70 60 70
MLU 68 82 65 84 / 70 70 30 40
DEQ 66 79 67 80 / 70 70 60 60
TXK 69 81 69 80 / 70 70 60 60
ELD 66 80 64 83 / 70 70 40 40
TYR 69 81 70 80 / 70 70 50 70
GGG 67 80 68 79 / 70 70 50 80
LFK 67 81 68 79 / 70 70 60 80
&&
.SHV WATCHES/WARNINGS/ADVISORIES...
AR...Flash Flood Watch until 7 AM CDT Thursday for ARZ050-051-059>061-
070>072.
LA...Flash Flood Watch until 7 AM CDT Thursday for LAZ001>005-010>013-
017>020.
OK...Flash Flood Watch until 7 AM CDT Thursday for OKZ077.
TX...Flash Flood Watch until 7 AM CDT Thursday for TXZ096-097-108>112-
124>126-136>138-149>153-165>167.
&&
$$
24/26/19