Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/09/21
AREA FORECAST DISCUSSION
National Weather Service Albany NY
946 PM EDT Sat May 8 2021
.SYNOPSIS...
An elongated trough of low pressure will slowly migrate east of
the region tonight. A developing storm system across the central
and southern Plains States will approach later Sunday. Periods
of rain are expected by Sunday evening and continue through the
night. Conditions improve slowly on Monday with seasonable cool
weather and perhaps some showers, mainly for the higher terrain.
&&
.NEAR TERM /THROUGH SUNDAY/...
Upper system slowly exiting as upper dynamics and low level
forcing weaken. Showers are down to isolated in coverage and
should be dissipated late this evening. Clouds are gradually
breaking up in central NY and the breaks are building east. So,
between midnight and daybreak, eastern NY should see some breaks
in the clouds and western New England should see breaks by
daybreak.
Light winds and the breaking up of the clouds should support a
steady cooling of temperatures, especially after midnight. Not
including fog but some areas cold see fog depending on how much
clearing we get and if temperatures reach dew points for a
considerable amount of time. Just minor adjustments to the
temperatures, rain chances and sky cover through the night.
Previous AFD has a few more details and is below...
PREVIOUS DISCUSSION:
Deformation axis, inverted surface trough, extended from the
northwest hills of Connecticut into the Catskills and Herkimer
County. Some showers were attempting to develop to the east and
northeast of Albany which was tied to a more diurnal cycle along
with a little elevation boost to the convective potential. HRRR
at the moment appears rather too robust with the forecast
potential this afternoon with the HREF CAMS members a bit more
realistic. So we will keep PoPs into the chance-scattered
categories for the balance of the late afternoon into the early
evening hours. Due to rather chilly temperatures this afternoon
across the higher terrain of the Dacks and Catskills, with
sunset we would not be surprised to see a little wet snow mix in
before the departure of the precipitation. Variable cloud cover
can be expected across the CWA with better chance for some
clearing south of Albany with northwest winds aiding in
downsloping off the Catskills. Some patchy fog will be possible
where the rain was more prevalent earlier today as overnight
lows dip back into the 30s across the terrain to around 40F for
the Hudson River Valley locations.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
Mothers Day (Sunday)...Fairly good consensus for a dry yet cool
for the month of May standards. Any sunshine we are able to soak
in during the morning will become increasingly filtered by an
increase in cloud coverage. As seen in the upstream H2O vapor
loop, an elongated area of moisture extending from the Tennessee
Valley and northwestward into the Dakotas which leads to the
upper low over Montana will be approaching. 12Z NCEP Model Suite
and international guidance have come into better agreement with
the onset of precipitation during the afternoon from southwest
to northeast. An enhanced area of rainfall is forecast to
develop south of I90 by sunset with impressive FGEN and
isentropic lift. Otherwise, look for light rain to evolve after
18-21Z timeframe Sunday.
Sunday night...Surface wave is forecast to track east-northeast,
south of I80 corridor, with periods of light rain across the
region. The heaviest rainfall appears to fall south of I90 where
combination of best H850-700 FGEN, isentropic lift and divergent
q-vectors aloft are progged to occur. Here, rainfall amounts
could approach three quarters of an inch with values near two-
tenths north of I90. It will not only be damp but rather chilly
with overnight lows into the 30s across the higher terrain to
40-45F for valley locations.
Monday into Monday night...Overall a drier weather pattern as
the surface wave tracks off the New England coastline in the
morning hours. Then a cold front will approach and clear our
eastern CWA Monday evening. H850 temperature hover just above 0C
during the daylight hours then in the wake of the frontal
passage drop below zero by sunrise Tuesday morning. If skies are
able to clear and winds decouple, could see some valley areas
get close to frost advisory. So only slight chance PoPs for
mainly the terrain Monday then with the passage of the cold
front some wet snow may mix in across the Dacks with some Lake
Ontario contributions. Highs mainly into the 50s on Monday then
lows into the 30s with around 40F for Hudson River Valley
locations.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
The long-term forecast period will feature cooler than normal
temperatures with a couple of upper troughs that will serve as the
pre-dominant play makers during this period. The weather pattern
also looks mostly dry/tranquil through the period.
We start off the period on Tuesday with a pretty stout 540 mb upper
low moving over the area from southeastern Canada. Thermal profiles
aloft associated with this upper low will be pretty cold for this
time of year with 850 mb temperatures ranging between -2C to -4C,
which is 1 to 2 STDEVS cooler than normal. In addition to the chilly
conditions, some scattered showers are possible during the day on
Tuesday as cyclonic vorticity advection and differential heating in
the boundary layer increases. Given the dynamics in place, some of
the showers could be convective, especially during the peak diurnal
hours. At this stage it appears that higher elevation areas along
and especially north of I-90 will be most favored for showers on
Tuesday. Some of the highest peaks of the SW ADKs could see a
rain/snow shower mix. Most areas within our cwa (especially along
the valley and south) should remain dry. Breezy northwest winds will
be the other story on Tuesday as well. Increased height falls aloft
and incoming cold air advection associated with the aforementioned
540 mb upper low will cause for a tightening of the pressure
gradient. This will allow for breezy northwest winds at the surface.
The synoptic and topographic setup could favor a channeling of
breezy northwest winds down the Mohawk Valley into the Capital
District and into the Berkshires. At this stage of the game, it
appears that winds could gusts as high as 25 kts in this zone during
the day on Tuesday.
Tuesday night colder air moves over the region as any leftover
rain/snow showers come to an end. Overnight low temperatures will be
something to monitor in the days ahead given that levels could
approach/near frost or freeze territory. This is of concern given
that the growing season has begun most places. That said, winds
could be the saving grace as winds will only let up a little Tuesday
night with gusts approaching 20 kts. Again this will be something to
keep watch on in the days ahead.
Drier weather conditions for all return Wednesday as a broad 1028 mb
surface high pressure system builds into the region from the west.
Beyond Wednesday, deterministic forecast models diverge on the
evolution/overall handling of the weather pattern, particularly
with the aforementioned surface high pressure system and a storm
system over the southern U.S. Eventually, the storm system over the
southern U.S. will track northward towards our area. The question
remains when and how far west will it track along the East Coast to
potentially affect our area. The 12z GFS model is quickest/most
bullish with precipitation chance over our area, while the 12z
ECMWF/CMC models are more slower and more conservative with
precipitation chances (keeping the track of the storm system
furthest east). The suite of ensembles support the possibility of
precip as well with again the GEFS being the most aggressive. One
item to note is that run to run trends have scaled back for all
models and their ensembles precipitation chances and amounts. That
said, have kept just low grade 20-30% PoPs Thursday through Friday.
Forecast models advertise another storm system approaching from the
central U.S. over the weekend into early next week timeframe. Given
the amount of uncertainty in the medium range, have only low grade
PoPs through the remainder of the extended period.
As far as temperatures, as mentioned earlier, anomalies will run
cooler than mid May standards for the balance of this period. While
our normal highs for this time of year are in the upper 60s and lows
in the upper 50s, projected daytime highs during this period will
range from the mid 50s to mid 60s (cooler higher elevations) and
nighttime lows will mostly be in the 40s especially in the valleys
(cooler higher elevations).
&&
.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
Upper system exiting and showers are expected to end through
this evening. VFR ceilings will prevail at all TAF sites through
the evening. There are some breaks in the clouds in central NY
that are building east. Ceilings should break up between
midnight and daybreak at KALB, KPOU and KPSF but KGFL may see
ceilings most of not all of the night. There could be intervals
of ceilings in the MVFR range at KGFL between about 08Z-12Z.
Not including fog but if there are enough breaks in the clouds
to allow temperatures to reach dew points for a considerable
amount of time, some fog could form but chances too low to
include until near term trends can be monitored. After about
12Z, just a few clouds well above 3000 feet into the afternoon.
By about 20Z, the next system approaches and the leading edge of
ceilings just above 3000 feet spread across the region. SOme
patchy rain could approach KPOU and KPSF, so including VCSH
there after 20Z.
West to northwest winds at less than 10 Kt this evening become
near calm by daybreak. West winds Sunday morning at less than
10 Kt shift to southwest by around 20Z.
Outlook...
Sunday Night: High Operational Impact. Definite RA.
Monday: Low Operational Impact. Slight Chance of SHRA.
Monday Night: No Operational Impact. NO SIG WX.
Tuesday: Moderate Operational Impact. Breezy. Chance of RA.
Tuesday Night: No Operational Impact. NO SIG WX.
Wednesday: Low Operational Impact. Breezy. NO SIG WX.
Wednesday Night: No Operational Impact. NO SIG WX.
Thursday: No Operational Impact. NO SIG WX.
&&
.FIRE WEATHER...
Showers will slowly come to and end tonight as the passage of
the weak low pressure slides east of the region. Overnight RH
values range between 75 and 95 percent with a westerly wind less
than 10 mph.
The RH values fall between 30 and 50 percent Sunday afternoon,
with those lower values to the northeast of Albany. Otherwise
should be a generally dry day until late in the day. Chances of
rain increase as the next low pressure system approaches. The
winds to be west to southwest at 5 to 15 mph.
Periods of rain expected Sunday night with likely a soaking
rainfall south of I90.
&&
.HYDROLOGY...
Widespread hydrological issues on the main stem rivers are not
expected into the middle of next week.
Showers will be slowly coming to an end this evening as low
pressure tracks away from the region.
Another chance of rain with light to moderate amounts arrives
late Sunday through Monday. Total rainfall may vary from two
tenths of an inch to a half or three-quarters of an inch over
the HSA with the higher totals from the Capital District south
and east.
For details on specific area rivers and lakes,
including observed and forecast river stages and lake
elevations, please visit the Advanced Hydrologic Prediction
Service /AHPS/ graphs on our website.
&&
.ALY WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
MA...None.
VT...None.
&&
$$
SYNOPSIS...BGM
NEAR TERM...BGM/NAS
SHORT TERM...BGM
LONG TERM...Evbuoma
AVIATION...NAS
FIRE WEATHER...BGM/Wasula
HYDROLOGY...BGM/Wasula
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1157 PM EDT Sat May 8 2021
.AVIATION...
A mix of mid and high clouds over Lower MI thickens and lowers
during the late night before rain moves in along the IN/OH border
toward sunrise. Light rain initially allows VFR conditions to hold
on for a few hours during the early morning followed by a quick
transition to MVFR as rainfall rate increases. This mainly affects
the DTW corridor and likely up to PTK while just brushing the FNT
region with some sprinkles during the afternoon. The northern edge
of the pattern stops before reaching MBS and then begins pulling
away to the south and east. The diminishing trend in coverage and
intensity continues through late afternoon with rain ending across
the entire area by 00Z Sunday evening.
For DTW... High clouds thicken and lower during the late night
before rain begins shortly after sunrise. A quick transition to MVFR
occurs as the rain intensity increases around mid morning.
Conditions could also briefly touch IFR during the peak rain
intensity within a couple hours of 18Z.
.DTW THRESHOLD PROBABILITIES...
* High for ceiling 5000 feet or less mid morning into late
afternoon.
&&
.PREV DISCUSSION...
Issued at 948 PM EDT Sat May 8 2021
UPDATE...
Evening satellite imagery and surface observations indicate
afternoon cumulus lifted and settled into an 8000 ft broken layer
over the Tri Cities and northern Thumb region. The cloud trends
indicate a few more hours of cushion are likely before any strong
radiational cooling occurs in that area. The mention of patchy to a
few areas of frost is looking good before high clouds thicken later
in the night.
Looking farther ahead late tonight and Sunday, textbook cyclogenesis
is ongoing on the lee side of the Rockies through the central Plains.
It is a large low pressure system that already has a generous supply
of Gulf moisture fueling a wide swath of showers and thunderstorms
to the north and east of the low track. Moisture transport into the
low and mid levels of the leading warm front will be enhanced by the
strengthening nocturnal low level jet later tonight and Sunday
morning to continue fueling convection roughly in the surface to 850
mb frontal zone. Thunderstorms in this pattern are expected to remain
south of the Ohio border but the northern fringe of showers reaches
across into Lenawee and Monroe counties by sunrise. The latest runs
of the HRRR, RAP, and the 18Z NAM help with some refinement of onset
timing and additional sharpening of POPs on the north flank of the
pattern. The 18Z NAM collapsed the spatial scale of elevated
convection in its QPF footprint compared to the 12Z run while the 00Z
HRRR adjusted slightly farther north compared to its afternoon runs.
Together, these model trends suggest keeping POPs high for a late
night onset toward the Ohio border while delaying the northward
expansion by a couple hours during the morning. The 700 mb frontal
zone is still too strong, especially with a boost from the upper jet
over the northern Great Lakes, to rule out higher based showers
reaching the M-59 corridor by late morning and then brushing the I-69
corridor during the afternoon. Other than the above mentioned timing
refinements, today`s afternoon forecast package remains fully on
track for Sunday with categorical POPs in the Detroit metro area
tapering to chance north of I-69 and then dry north of the Tri Cities
to northern Thumb.
PREV DISCUSSION...
Issued at 339 PM EDT Sat May 8 2021
DISCUSSION...
Seasonably cool early May environment firmly entrenched again this
afternoon, owing to the perpetuation of higher amplitude troughing
featured south of a closed mid level circulation positioned near
Hudson Bay. These lower mid level heights briefly ease northward for
latter half of the weekend period, as attention shifts to lower
amplitude shortwave energy of pacific origin now ejecting into the
plains. Blossoming corridor of mid level warm/moist air advection
will emerge tonight within the north/ne flank of the resulting low
level cyclone, the initial stages noted locally via a steady increase
in high based cloud from south to north overnight. This will place a
definitive ceiling on nocturnal cooling potential, particularly
south of the I-69 corridor. Larger window of open sky supports lows
of mid 30s north, with readings across the south in the vicinity of
40 degrees.
Mid level frontal zone lifts northward into southeast Michigan late
tonight and early Sunday, remaining anchored over southern sections
of lower Michigan throughout the daylight period. Aggressive period
of deep layer saturation will commence along the frontal slope,
anchored initially by strong system relative isentropic ascent.
Frontal forcing will increase with time as the boundary intersects
the right entrance region of the upper jet max fixated within the
height fall center looming to the north. Magnitude and duration of
forcing maintains a high probability for an all day, solid soaking
rainfall event south of the M-59 corridor. Rapid decline in both
forced ascent and moisture quality with northward extent suggests a
sharp northern edge to the gradient for meaningful precipitation -
latest model guidance offering the I-69 corridor as this line with
rain chances tailing off over the Saginaw valley and northern thumb.
Daytime heating potential certainly muted given rainfall expectation
and a northeast gradient - a raw day as temperatures linger in the
middle and upper 40s many locations outside of the far north.
Hudson Bay low will slowly eject south-southeast into the eastern
great lakes during the early week period. Subsequent height falls
arrive locally Monday, effectively reinforcing the cooler resident
thermal profile within prevailing low level northwest flow. Diurnal
steepening of lapse rates could yield a shower or two during peak
heating across central lower mi, but absent of greater moisture
depth or more tangible forcing the prospects appear limited. Highs
locked in the 50s. Emergence of deeper layer northwest flow
contained within the broader mid level cyclonic periphery supports a
period of cold air advection Monday night and Tuesday - low level
thermal trough early Tue afternoon characterized by 850 temps of -4
to -6C. Once again highs should arrive a solid 10+ degrees below
average.
Modest warming trend during the late week period, as upper heights
gradually recover. Dry and stable profile Wednesday as low-mid level
ridging briefly governs conditions. Loosely organized troughing then
appears to take residence Thu-Fri, so potential for conditions to
become more unsettled again within this window.
MARINE...
High pressure will continue to remain in place across the central
Great Lakes the remainder of today with generally dry conditions
except for a few stray showers across portions of southern Lake
Huron and Lake St. Clair. The high pressure will shift slightly
north as low pressure tracks eastward from the central Plains
towards the northern Ohio Valley late tonight into Sunday, bringing
widespread rainfall to the southern half of the local waters. Light
and variable winds will reorient northeasterly in response to the
low pressure system and become moderate in strength, especially
across western Lake Erie, where the tightest pressure gradient will
help yield gusts around 25 knots during the day Sunday and building
wave heights of 3-5 feet posing hazardous small craft conditions.
Winds will back more northwesterly and become more moderate in
strength across all waters for early next week as high pressure
becomes reestablished across the Great Lakes.
HYDROLOGY...
Rain will increase in coverage across lower Michigan Sunday morning
as a low pressure system tracks through the Ohio valley. Widespread
rainfall expected through the daylight period from the M-59 corridor
southward, with a period of lighter rain reaching northward into the
I-69 corridor. Highest rainfall totals will exist near the Ohio
border, where amounts upwards of one inch will be possible. Rainfall
totals generally between one quarter and one half inch will occur
across the Ann Arbor and metro Detroit regions, with under a quarter
of an inch north of M-59. This rainfall is not expected to result in
flooding concerns.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...Small Craft Advisory from 10 AM to 10 PM EDT Sunday for LEZ444.
&&
$$
AVIATION.....BT
UPDATE.......BT
DISCUSSION...MR
MARINE.......IRL
HYDROLOGY....MR
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Quad Cities IA IL
702 PM CDT Sat May 8 2021
...AVIATION UPDATE...
.SYNOPSIS...
Issued at 213 PM CDT Sat May 8 2021
A surface low is developing in the vicinity of the corner of NE
Colorado, NW Kansas, and SW Nebraska this afternoon. A warm front
extends east southeastward from the low towards Kansas City then
southeastward to Memphis TN. Clouds have overspread Iowa,
northeast Missouri into west central Illinois. A band of
precipitation associated with FGEN forcing in the 850 to 500 MB
layer stretches from FSD to IOW and then southeastward to MQB.
Temperatures across the area were generally in the lower to mid
50s. AWG is the cool spot at 48 degrees with rain falling.
&&
.SHORT TERM...(This Evening through Sunday)
ISSUED AT 213 PM CDT Sat May 8 2021
Forecast Changes:
1. Rainfall amounts of 1 to 1.5 inches have expanded across to
include all of the area for this storm system.
The main forecast concerns were chances of precipitation and type.
Model forecasts have trended southward with the track of the
surface low moving it from northern Missouri to roughly the
Interstate 80 corridor. Confidence still remains low on
precipitation amounts and location.
Models have consistently shown 850 to 500 mb FGEN overspreading
the area late this afternoon into early Sunday morning. This in
conjunction with shortwave trough moving across the area this
evening in zonal flow aloft. This will provide strong forcing for
precipitation across the area tonight into Sunday morning. Deep
moisture will also be in place during this period. Expect showers
to expand in coverage this afternoon this evening then warm moist
air aloft will bring instability to the area south of Interstate
80 with the threat for isolated to scattered thunderstorms. There
is no threat for severe storms today. There is one potential fly
in the ointment for the heavier precipitation is if the
convection expected across eastern Kansas into Missouri inhibits
to the northward flow of moisture into the area which the amount
of precipitation especially across the northern half of the area.
Precipitation type: Some models have been showing dynamic cooling
taking across the area tonight with the strong forcing in place
and large dewpoint depression this afternoon before saturation
wins out. This will cause the column to further cool. The NAM and
HRRR are the coolest of these solutions with a change over to snow
along the Highway 20 corridor and temperatures in the mid 30s
during this period. Think that a mix of snow is more likely with
slowly rising dewpoints but it will be close. Do think that a
couple of hours of snow or a rain/snow mix is possible early
sunday morning but do not expect any accumulations.
An easterly wind will develop this evening with gusts of 20 to 30
knots or up to 35 MPH. This will result in a raw, cool night,
across the area with falling precipitation. Low temperatures on
Sunday morning will range from the upper 30s north of Interstate
80 to the lower 40s south.
Precipitation will come to end from west to east Sunday morning.
Skies will be partly cloudy by the end of the day on Sunday. Winds
will diminish Sunday afternoon as the surface low passes to the
south and east of us. A quick rebound in temperatures is expected
as precipitation comes to an end on Sunday with highs in the lower
to mid 50s.
.LONG TERM...(Sunday Night through Saturday)
ISSUED AT 213 PM CDT Sat May 8 2021
1. Temperatures are still a concern in the days ahead.
While rainfall will not be significant, temperatures will continue to
be well below normal, and will bring the threat for additional frost
headlines to both Sunday night and Monday night in the forecast for
this upcoming week.
The pattern through Tuesday is dominated by a cold upper trof of low
pressure, centered over the Great Lakes. This will keep our skies
partly to mostly cloudy each day, and clear to partly cloudy at
night, since much of the cloud over is diurnally driven on the west
side of the trof. Highs given the strong sun angle will reach the
upper 50s to lower 60s Monday and Tuesday, but the cold air dry air
aloft will support lows in the 34 to 38 range Sunday and Monday
night, allowing for the threat for frost, especially along and north
of Highway 30.
Some light showers may develop at peak heating Monday, but for now,
I`ve left the forecast dry. It`s something to watch, and if the
signal towards instability showers continues, we can add
isolated/scattered showers on the next cycle. If they occur, they
would not offer a significant QPF impact.
The upper pattern shifts east somewhat by Wednesday, allowing for
surface high pressure push towards the eastern Great Lakes. Light
south winds and sunshine should return by Wednesday, with increasing
southerly flow strengthening by late week. While our temperatures
will rise, guidance continues to show mainly 60s and lower 70s,
until Saturday, where mid 70s are expected. Over all, this should be
a pleasant weather week after Monday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday Evening)
ISSUED AT 654 PM CDT Sat May 8 2021
Poor aviation conditions are expected tonight into early Sunday
morning as widespread light to moderate rain drops ceilings and
visibilities to MVFR/IFR. The rain could become briefly heavy at
times south of DBQ and there is the potential for embedded
thunderstorms. In addition to the rain, gusty E to NE winds
between 20 to 30 kts are anticipated tonight. Conditions will
improve through the mid to late morning on Sunday.
&&
.HYDROLOGY...
Issued at 1037 AM CDT Sat May 8 2021
A river flood watch has been issued for the La Moine River at
Colmar due to the current forecast of 1 to 2 inches falling in the
basin. There is lower confidence at this time in the exact
placement of heavy rain as well as rainfall amounts. While strong
lift will be in place north of the warm front tonight into Sunday
across Iowa and northwest Illinois, severe thunderstorms across
Missouri late this afternoon into this evening may disrupt the
flow of moisture into the area and limit the amount of rain that
we receive. Given the current dry conditions, the placement of the
highest rainfall amounts will dictate which points see within
bank rises.
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
SYNOPSIS...Cousins
SHORT TERM...Cousins
LONG TERM...Ervin
AVIATION...Uttech
HYDROLOGY...Cousins
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1132 PM EDT Sat May 8 2021
.UPDATE...
Issued at 1131 PM EDT SAT MAY 8 2021
Made some adjustments to precip chances for the rest of tonight,
based on the latest radar trends and HRRR and GFS model data. PoPs
overall were decreased with the main focus of rain the rest of
tonight along and north of the Mountain Parkway. Made some small
adjustments to temperatures as well, but nothing earth shattering.
Did have to take down Somerset`s low for tonight as they had
already fallen below the previously forecast min as of 3Z. Also
issued an update to the NPW simply to give the mid-shift until
toward the end of their shift to update it again. The information
in the NPW stayed exactly the same. All updated produces have been
issued.
&&
.SHORT TERM...(This evening through Sunday night)
Issued at 505 PM EDT SAT MAY 8 2021
Energy rounding the base of a negatively tiled trough over the
northern Rockies will break away and track eastward across the CONUS
in rapid fashion today. This disturbance will reach the lower Ohio
Valley by tonight. Rockies lee side surface low will strengthen
and move eastward in response, lifting a warm frontal boundary
northward across eastern Kentucky tonight. This will leave eastern
Kentucky within the warm sector of this storm system leading up
to cold frontal passage Sunday night.
Gradient winds will increase considerably ahead of the cold front
that is expected to pass through eastern Kentucky Sunday evening
into Sunday night. Operational models indicate that H850 winds will
increase within a LLJ to between 50 and 60 kts while H950 winds
increase to around 35 kts. Steep boundary layer lapse rates (>7
C/kg) and reasonably deep mixing (up to 5 kft AGL) over to
portions of eastern Kentucky could help mix down higher wind gusts
of around 35 to 40 mph. However, substantial mid/high level cloud
cover may help mitigate the deeper mix down of higher wind gusts
as well. Decided to try and give a little heads-up to our boaters
and went with a Lake Wind Advisory for Cave Run and a special
weather statement for the remainder of the area. Will need to
monitor upcoming runs in case the Lake Wind should be expanded to
the Lake Cumberland region as well, where wind gusts appear more
marginal.
SPC has a good portion of our area in a marginal risk for severe
thunderstorms Sunday. Cloud cover dampens potential instability
across the area and timing of the front into eastern Kentucky
Sunday evening into Sunday night means prime heating will be over.
MUCAPES of only 500-1000 J/kg and effective shear of 30-35 kts
could be enough for a few strong storms to fire, possibly an
isolated severe or two as well. As stated before, boundary layer
lapse rates are quite steep, mainly across the southeast portion
of the forecast area. But mid/upper level lapse rates are
marginal, indicative of the lack of over instability. At this
point, feel overall threat to be fairly minimal. However, this
could change should we see more insolation and better surface
based instability. Obviously, with the strong wind fields in
place, gusty winds in and around any showers or thunderstorms
would be the greatest hazard, which is why SPC decided to carry a
marginal threat...i.e. due to convectively augmented wind gusts
to gradient winds.
.LONG TERM...(Monday through Saturday)
Issued at 505 PM EDT SAT MAY 8 2021
Things start off pretty rainy initially on Monday morning. The
active weather of the short term will be winding down some as the
surface low continues east and drags the cold front through the
remaining southeastern half of the area. Any thunderstorms should be
done at this point and any ongoing rain showers will be pushing down
to the south through the day. High temperatures Monday will stay
quite cool, especially when compared to Sunday, under the
northwesterly to northerly flow behind the front, and generally top
out in the low 60s. High pressure then nudges in across the Ohio
Valley as the front exits, and skies start to clear some late, at
least in the northern parts of the CWA close to the center of the
high. The rain has generally pushed south of the area at this point.
However the NAM does bring some rain back into the far southern
counties late Monday night with a small passing wave of energy
aloft. Even with it being somewhat consistent in this solution, it
is a bit of an outlier and ensemble probabilities are low. So, kept
PoPs just barely under slight chance due to reasons just mentioned
and to keep more consistent with neighbors. Lows Monday night are
chilly in the low 40s.
Cool and dry weather will continue through mid-week as high pressure
remains over the Ohio Valley. Tuesday night is cold in particular,
dipping down into the upper, and possibly mid, 30s. A few valley
locations, particularly further north, may be able to squeak out
temperatures low enough to support a possible light touch of frost,
but am not super confident in that at this point, and trends will
need to be monitored. Going into Thursday, there`s still some
disagreement remaining. In general, there`s a wave that nudges over
from the Mississippi Valley over the day Thursday. The GFS in
particular is a bit sharper with this feature along with a slightly
stronger wave at the surface, and brings rain back into the area
Thursday afternoon. The ECMWF and Canadian have the upper level wave
weaker and have precip staying to our south. Ensembles appeared to
lean slightly more towards the ECMWF and Canadian in terms of the
pattern as a whole, and in terms of precipitation specifically,
probabilities are not super high, but not low enough to be ignored.
At this time, the forecast has rain moving in Thursday afternoon and
exiting Friday. A few thunderstorms are also possible Thursday
afternoon, though this is conditional on there actually being rain
at all. There looks to be a break in the rain Friday, before another
system eventually moves in sometime over the weekend. Temperatures
stay cool generally, but gradually modify through the second half of
the period. Overall, for the late part of the work week, agreement
is poor, and relied on the NBM for this time frame.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
ISSUED AT 727 PM EDT SAT MAY 8 2021
Mid and high level clouds will yield BKN to OVC CIGs this evening
and tonight, as a sluggish boundary returns to the north
overnight as a warm front. This warm front will drop CIGS to
around 6K AGL with scattered rain showers developing tonight.
Showers should end as sunrise approaches, with CIGS lifting back
up to 100 AGL or higher. There could even be a short window of
time where skies scatter out Sunday morning, with perhaps BKN high
clouds left over. A low level jet will increase across the region
late tonight with the warm frontal zone, leading to a period of
about 4-6 hours of non- convective low level wind shear, likely from
9 to 15Z. Surface winds will increase to between 10 and 15 kts
from the southwest from late morning onward, as stronger winds
aloft mix down. Gusts to around 25 kts will be possible at times,
the result of an approaching cold frontal system Sunday, which is
expected to reach eastern Kentucky by Sunday evening. SYM may
begin to be affected by showers and a few storms by around 19Z, as
the cold front approaches. Showers and storms will likely not
begin affecting SME, LOZ, and JKL until near the end of the TAF
period.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
Lake Wind Advisory from 1 PM to 7 PM EDT Sunday for KYZ051-052-
060-106.
&&
$$
UPDATE...AR
SHORT TERM...RAY
LONG TERM...HAS
AVIATION...AR
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
917 PM CDT Sat May 8 2021
.UPDATE...
917 PM CDT
Going forecast is in generally good shape this evening, with only
some minor adjustments made based on observational and recent
model trends. Primarily, tightened up the sharp QPF gradient
along the I-88 corridor, brought some slight thunder chances
farther north out west through midnight, and shifted greatest
potential for a period of rain/wet snow slightly south late
tonight into early Sunday morning.
Precipitation continues to overspread the forecast area at mid-
evening ahead of a strong 995 mb surface low analyzed over central
Kansas. A surface warm front stretched from northeast KS
southeast into far western TN, with an impressive low-mid level
baroclinic zone within the elevated frontal zone north of the
surface boundary. Strong frontogenesis was occurring across IA and
into central/northern IL within this zone, with 35-45 kt 850 mb
return flow providing moisture transport/convergence and producing
precipitation into the forecast area. Several mPING reports of
graupel had been noted upstream across IA as precip developed into
dry low levels, though largely all rain at the surface as the
column saturates. Has also been persistent thunder along and just
north of the U.S. 30 corridor across IA this evening, along the
northern periphery of elevated MUCAPE plume.
Model trends, including 18Z ECMWF and several consecutive runs of
the HRRR, have continued to depict a tight gradient in expected
rainfall totals along and just north of the I-88 corridor across
northern IL. Going forecast trends for precip timing/pops appear
to be in good shape, though did tighten up the QPF gradient across
far northern/northeast IL with lowered amounts especially toward
the IL/WI border in the northern suburbs, and increased amounts
immediately south of I-88. Still expecting 1-2 inch amounts there,
with isolated 2+ amounts possible. Lightning trends have been
decreasing recently as elevated convection approaches the
Mississippi, but based on proximity did take slight chance thunder
potential into the I-88 corridor and across our southwest counties
this evening. This should slide southeast with time, with areas
mainly south of I-80 favored for embedded thunder later tonight.
Other adjustment was to shift our narrow axis of potential rain
and snow mix (or even briefly changing to all wet snow pre-dawn)
slightly south about a half county or so into the I-88 corridor
west of Chicago late tonight. Again successive HRRR runs and the
18Z ECMWF continue to highlight that area for this potential, with
HRRR and RAP forecast soundings both depicting cooling of the
column and WBZ heights lowering below 1500 ft AGL along the
northern periphery of the heavier precipitation shield during the
pre-dawn hours. Continued to mention the potential for some slushy
accums from roughly the Forreston and Dixon areas through Rochelle
and into DuPage/northwest Will counties. Blustery east flow off
the lake should help keep surface temps a little warmer farther
east into the metro area and reduce potential for any accums on
grass or elevated surfaces.
Otherwise, no changes to going forecast. Updated digital and text
products already available.
Ratzer
&&
.SHORT TERM...
245 PM CDT
Through Sunday...
Mother`s Day will feature weather conditions more characteristic
to St. Patrick`s Day, with cloudy, blustery, and very wet
conditions for the morning. The main forecast messages are:
* Rain onset spreads from west-to-east this evening with possibly
brief ice pellets mixing in at first
* Rain increases in intensity late this evening into overnight,
with some embedded thunderstorms possible mainly south of I-80
* Potential for a mix with snow has increased for primarily a
portion of north central Illinois and eastward toward the Fox
River Valley part of northeast Illinois late tonight into early
Sunday morning
* Rainfall of 1 to 2 inches for most locations along/south of
I-88, with isolated over 2 inches possible, though flooding
threat should remain low
* Gusty northeast winds keep temperatures down through Sunday,
even as rain ends west to east late morning into afternoon
A lot to unpack for the rest of this weekend. Looking upstream on
GOES-16 water vapor imagery shows a well-defined, strong upper low
over Montana moving southeast bringing with it 100 meter 500 mb
height falls. In still a somewhat split flow pattern, a 100 kt
subtropical jet moving into the Central Plains ahead of this wave
will result in a deepening surface low below 1000 mb into
Missouri overnight. This should spread into an area of some
coupled jet divergence over our region overnight into Sunday
morning, resulting in the mid-latitude system overall maturing as
it heads over Illinois/Indiana. The synoptic pattern is such that
a rain shield should gradually blossom through the evening
followed by a steady moderate to more heavy rain with the stronger
upper forcing overnight into early Sunday.
Model guidance is in decent agreement with this synoptic
evolution, though some spread exists and given where we are
located within the baroclinic leaf, a subtle difference in low
track will alter the heavier QPF axis, the area where a few hour
wet snow mix is favored, and the magnitude of the winds. Given a
hefty footprint of convection anticipated over the Central Plains
into Missouri River Valley tonight, this could result in a more
south track within the model solution envelope, such as the RAP
has been advertising and the 12Z ECMWF depicts. The HRRR has also
trended ever so slightly south from its earlier solutions today.
This is the more favored route, but a more north solution such as
the 12Z NAM cannot be fully discounted yet.
All model guidance agree on the strong mid-level baroclinic zone
to our west (18C difference from LBF to MPX on 12Z RAOBs)
tightening over the area tonight and a sharpened frontogenetic
vertical circulation. This is a longer duration zone of such
forcing and this is the zone most favored to see the heaviest rain
rates on strong moisture convergence and ascent. It`s also along
this where enough wet bulb cooling may occur to support snow.
Given marginal low-level melting profiles (<10 J/kg of positive
energy using a local revised Bourgouin technique) and upright
instability predicted on an area of steeper 650-500 mb lapse
rates, there likely will be an area that does change over. As
mentioned earlier, there certainly is some wobble room where this
is, but a consensus/middle ground solution is toward I-88. Warm
surface temperatures will result in quite a bit of immediate
melting, but if a band of instability-driven heavier rates
persists for 2-3 hours as mainly snow, then could certainly see
accumulation on at least grassy and elevated surfaces. While a
tail of the solution envelope, f-gen magnitude events such as this
can provide a mesoscale-level (multi-county scale) quick several
inches. There have been a few CAMs run that have shown something
like this, though seem to be much too robust in their efficiency
of turning 100% QPF to snow, and at too high of ratio.
Further east with increasing easterly winds off the warmer waters
of Lake Michigan, the potential for snow drops into the heart of
the Chicago metro as well as far northwest Indiana. South of I-80,
more melting energy exists thanks to the proximity of the 850 and
700 mb lows passing closely by to the south.
It is always a true challenge with predicting snow during these
tail end of season events, as thermal profiles are marginal and
present one striking failure mode. Also there could be enough
moisture transport robbing from the south by daybreak to start
reducing the precipitation rates by early Sunday morning to the
point where overcoming the marginal low-level temperatures becomes
quite iffy.
The surface low looks to be due south of the area during the
morning Sunday, and this is when the tightest pressure gradient
and strongest winds are predicted. The 925 mb winds look to be
around 35 kt, with the outlier NAM giving 40 to 45 kt. With some
lake-induced steeper lapse rates and a slightly deeper boundary
layer, some gusts to 40 mph may be experienced in the lake
adjacent counties with the onshore flow. As a note regarding any
lakeshore flooding concern, wind speeds over the lake are too low
and the direction does not look to maximize the fetch, especially
with lake levels having dropped over the past year.
As the system departs east, rain will end from west-to-east over
the region, with areas east of I-55 likely seeing some rain
continuing into early afternoon. The cloud shield, precipitation,
and winds will keep temperatures from climbing much at all on
Sunday morning, with many areas likely hanging in the 30s through
10 to 11 AM. There should be some recovery in the afternoon,
although highs should probably stay shy of 50 for many of those
eastern CWA communities including Chicago. These will not be a
record cold high temperatures for the day as those are low 40s
for Chicago and Rockford. See the longer term forecast below for
more brighter weather to discuss by later next week!
MTF
&&
.LONG TERM...
119 PM CDT
Sunday night through Friday...
As a surface high pressure system settles over the Great Lakes
beneath upper-level northwesterly flow, most of next week looks
relatively quiet. Sunday and Monday nights continue to look chilly
with lows in the mid 30s supporting areas of frost away from the
Chicago metropolitan area. Light winds and partly cloudy skies
will then be a daily occurrence, with highs gradually warming from
the mid to upper 50s Monday and Tuesday toward the mid to upper
60s by the end of the week. Daily lake breezes will hold lakeshore
locations in the 50s, however. A few afternoon sprinkles or light
rain showers can`t be ruled out from time to time as "wiggles" in
the upper-level flow pass through. The upper-level pattern from
the weekend onward looks decidedly spring-like with warming
temperatures and chances for showers and thunderstorms.
Borchardt
&&
.CLIMATE...
330 PM CDT
Some wet snow mixing in is possible at Chicago and more so
Rockford late tonight and early Sunday morning.
The last time Rockford saw snow in May was May 16, 2014 (trace).
As for accumulating snow in May, the last time was May 10, 1990
(0.2 in.). The latest accumulating snow on record in Rockford is
May 11, 1966.
The last time Chicago (official site O`Hare) saw snow in May was
May 2, 2005 (trace). The last measurable snow in May was May 5,
1989 (0.5 in.). The latest accumulating snow on record in Chicago
is May 11, 1966. There have only been two Mother`s Days with snow
in Chicago since Mother`s Day became official in 1908, and those
were May 9, 1954 and May 8, 1960 (both traces).
MTF
&&
.AVIATION...
For the 00Z TAFs...
624 PM...Primary forecast concerns include...
Ifr cigs overnight/Sunday morning.
Strong/gusty northeast winds overnight and Sunday.
Rain developing this evening, ending late Sunday morning.
Chance of snow early Sunday morning.
Rain will spread across the area this evening and increase in
coverage and intensity late this evening into the overnight hours,
ending from west to east mid/late Sunday morning. There is likely
going to be a sharp cut off to this rain which may be near a rfd/
dpa/ord line and there is some uncertainty for cigs along and
north of this cutoff. Ifr cigs are expected to develop for much of
the area overnight and continue through late morning Sunday,
slowly lifting to mvfr and then to vfr during the afternoon. For
now have maintained only tempo ifr cig mention for rfd/dpa/ord.
There is a chance for a few thunderstorms overnight, but these are
expected to remain south of the terminals. There may be a narrow
axis of snow that develops along the northern portion of the rain
axis, which would possibly be along a rpj/arr/igq/gyy line. There
is quite a bit of uncertainty regarding the snow potential and for
now opted to keep previous forecast mention at rfd/dpa, though
some mention at mdw/gyy may be needed as trends emerge.
Easterly winds around 10kts will slowly increase through the mid/
late evening with gusts into the 20kt range overnight. Winds will
turn more northeasterly by daybreak when gusts into the upper 20kt
range will be possible, only diminishing into the mid 20 kt range
Sunday afternoon. These strong winds/gusts will end with sunset
Sunday evening. cms
&&
.MARINE...
245 PM CDT
Strong east-northeast winds will develop over southern Lake
Michigan late tonight and continue through midday Sunday. There is
potential for gale force winds with this but that signal is
somewhat muted, with the most favored outcome looking to be winds
of 30 kt and possibly sporadic gales Sunday morning and early
afternoon. This is supported by similar situations to that as
forecast (analogs), which indicate around a 60% chance of 30 kt
winds along the Illinois shore while less than 10% chance of 35 kt
winds. Also the winds becoming more north-northeast Sunday
afternoon into evening will continue wave action despite the wind
speeds gradually diminishing.
MTF
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
LMZ745...4 AM Sunday to 4 AM Monday.
&&
$$
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Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1053 PM CDT Sat May 8 2021
.UPDATE...
Issued at 1045 PM CDT Sat May 8 2021
Updated to include 06z aviation discussion below.
&&
.SHORT TERM...(This evening through Sunday night)
Issued at 250 PM CDT Sat May 8 2021
The big winner today is dry air. 12z MPX sounding showed RHs just
above h7 of less than 1%, so the baroclinic zone of forcing in place
from western NoDak (where it has been snowing most of the day!) to
southeast IA is doing nothing more than moistening the mid levels of
the atmosphere locally. HRRR has been trending farther and farther
south with the northern edge of the rain shield through the day and
it is now looking like it doesn`t even make it as far north as the MN
River in western MN. Still have categorical PoPs, but have them just
confined to the I-90 corridor. Though we may not get much rain out
of this, we are seeing ample mid/upper level cloud cover. These
clouds will help keep temperatures tonight from falling into the 20s
as they did this morning. There may be some clearing into central MN
tonight, so temps near 30 are possible up there, but this is also
where the growing season has not reached an advanced enough stage to
need frost/freeze headlines, so for now, we have no frost freeze
headlines. A one night break before they`ll likely be needed again
Monday and Tuesday mornings.
For Sunday, the GFS/NAM show a weak pressure trough working across
the area, with afternoon showers developing along the boundary in
southeast MN into adjoining portions of western WI. However, forecast
soundings looks really dry, so think this is nothing more than a
hint at a diurnal cu-field forming. Followed more the idea of the
ECMWF with a dry forecast and a Mother`s Day that is a little on the
cool side with highs in the 50s with a mix of clouds and sun.
Sunday night, the big unknown is what happens with cloud cover. At
the surface, high pressure will be moving in with light winds and dry
conditions prevailing. This will be yet another opportunity to drop
lows into the 20s and 30s, so another round of frost/freeze headlines
may be needed depending on how potential mid/upper cloud cover
impacts lows.
.LONG TERM...(Monday through Saturday)
Issued at 250 PM CDT Sat May 8 2021
More of the same to start this period on Monday and Tuesday with
surface high pressure and the same cut-off low aloft aloft. This
means dry conditions and below normal temperatures with highs in the
mid 50s on Monday and low 60s on Tuesday.
The pattern finally starts to change mid week as the cut-off low and
surface high pressure move out. This leads to a more active pattern
with a few shortwaves moving through the Upper Midwest. This first
wave moves through late Wednesday/early Thursday, but this appears to
be a rather week wave with little synoptic support provided so rain
chances are low. The next chances arrives Friday into Saturday and
this one could provide some more synoptic support and therefore some
rain. Despite this wave being present in most members of the GFS and
ECMWF systems there remains a wide spread in the strength of this
wave and its associated QPF. So the chances of rain look better late
week than mid week, but the spread remains high. For example among
GEFS members QPF for this late week wave range from near zero to a
half inch. There is however more clustering on the lower end such
that confidence is higher in this being a light precipitation event.
What remains more certain in this period is a gradual warming trend.
After we bottom out on Monday with high temperatures only in the 50s,
normal highs are in the upper 60s, temperatures will gradually warm
up next week. Breaking out of the early week northerly flow pattern
will allow temperatures to warm up to normal by the end of the week
with both forecast and normal highs around 70. Looking ahead the rest
of May looks more likely to be near or above normal rather than
below normal on the temperature front at this point.
&&
.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1045 PM CDT Sat May 8 2021
Solid VFR conditions expected throughout this TAF duration. High
clouds will be prevalent throughout, with ceilings likely to be
maintained overnight and potentially for much of Sunday. SE winds
under 10 kt to start will go light/variable overnight before picking
up 5-10kt Sunday from the north.
KMSP...No additional concerns.
/OUTLOOK FOR KMSP/
Mon...VFR. Wind N 10 kts.
Tue...VFR. Wind N 5 kts.
Wed...VFR. Wind SW 5-10 kts.
&&
.FIRE WEATHER...
Issued at 250 PM CDT Sat May 8 2021
A very dry airmass will remain in place through Tuesday. Afternoon
humidities between 20 and 30 percent are expected daily through
Tuesday. At this point, winds are not expected to be strong enough
any day to meet Red Flag criteria, but the dry conditions will
continue to lead to elevated fire weather conditions daily through
Tuesday.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...None.
WI...None.
&&
$$
UPDATE...JPC
SHORT TERM...MPG
LONG TERM...NDC
AVIATION...JPC
FIRE WEATHER...MPG
Area Forecast Discussion
National Weather Service Pueblo CO
327 PM MDT Sat May 8 2021
.SHORT TERM...(This evening through Sunday)
Issued at 327 PM MDT Sat May 8 2021
Warm and windy across much of the area today, though changes have
begun this afternoon as upper wave digs into the nrn Rockies and
cold front drops south through the plains. Enough upward
motion was associated with the wave to generate some high-based
storms over the mountains this afternoon, though large t/td
spreads were keeping precip light and confined to mainly
the higher elevations. Surface front was roughly along a COS to LAA
line as of 22z, and will likely accelerate southward this evening as
convective outflows give it a boost. Instability increases behind
the boundary, as dewpoints rise into the 30s/40s, suggesting a
risk of some strong/severe storms over the far eastern plains
into mid-evening. Severe wind will likely be the main risk given
large downdraft CAPE (gt 1200 j/kg), and latest HRRR suggests
cold pool/broad outflow boundary developing ahead of the storms,
which may generate a period of blowing dust and low visibility
mainly east of I-25 until sunset. Activity fades overnight, though
clouds will increase along and east of the mountains toward morning
as low level flow turns more e-se.
On Sun, cool/moist air mass covers the eastern plains, with some
isolated showers developing during the morning. By Sun afternoon,
low level sly flow reappears along the NM border, with CAMs
suggesting enough instability/shear for some strong/severe cells in
Las Animas County where SPC has a marginal risk. Just enough
instability elsewhere for a mention of thunder in the afternoon as
weak convection develops over the ern mountains and I-25 corridor,
though severe threat will be low given CAPE of only 100-300 j/kg
away from the mountains. Max temps will be cooler area-wide, most
pronounced cooling on the plains, where clouds and precip should
hold readings even cooler than NBM numbers would suggest, especially
along I-25.
.LONG TERM...(Sunday night through Saturday)
Issued at 327 PM MDT Sat May 8 2021
...Potential for widespread precipitation event for plains and
eastern mountains through early Tuesday...
...Possibility for significant snow accumulations above around
9000 feet in the eastern mountains...
.Sunday night through Monday...Trough over the northern and
central Rockies will progress eastward with cool and moist airmass
over the eastern plains and into the eastern mountains. Models and
ensembles show variations in the strength of the trough which
will affect the amount of precipitation on the plains and eastern
mountains. The models and ensembles generally fall into to camps.
The GFS and GEFS mean have a sharper trough across the northern
Rockies. The sharper trough has more southwest flow aloft with
the 700 mb baroclinic zone remaining over northern Colorado. With
a widespread overrunning event likely Monday into Monday night,
the further northern baroclinic zone would tend to keep the
heavier precipitation over northern Colorado. The EC, EPS and CMC
have a weaker trough with the 700mb baroclinic zone remaining
further to the south. As a result, the heavier band of QPF would
be over southern Colorado. A quick look at the cluster analysis
shows the general disparity between the models and their
associated ensemble means for QPF Monday night into Tuesday. In
the grids followed the WPC QPF and the NBM snow levels. The WPC
QPF is good compromise for QPF totals, giving 2 day totals from
around 0.6 to 1.2 inches of liquid. If the further south solution
verifies, QPF totals could be higher. As for the burn scars,
believe much of the precipitation will be stratiform with lower
rates over a longer time period. The NBM snow level is a good
compromise between the higher snow levels in the GFS/GEFS and the
lower snow levels in the EC/EPS/CMC solutions. The NBM keeps the
heavier snow mostly above 9000 feet. It could get cold enough
Monday night for snow over the Palmer Divide with the grids
currently having a few inches.
In addition, the location of the baroclinic zone will affect the
surface temperatures. The warmer GFS tries to mix out the Raton
Mesa area Monday with warmer temperatures. The GFS tends to mix
out the lower level cold air too quickly, even if the upper level
solution verifies. As a result, I have cooler the temperatures
Monday on the eastern plains in collaboration with DDC.
Given the uncertainty with the solutions, that the heavier snow
will be over the higher elevations, and most of the accumulations
will be Monday and Monday night, will not issue any winter
highlights at this time.
.Tuesday...Upper trough starts moving east of the region with a
cool upslope airmass on the plains. Expect some showers to
continue on Tuesday over the eastern mountains and plains with
generally light QPF amounts.
.Wednesday through Saturday...Upper ridge builds over the region
with a warming and drying trend. A weak disturbance may move into
the region late in the week with some chances to showers or
thunderstorms Friday and Saturday. NBM has silent to isolated PoPs
with light QPF, which summarizes the pattern well. --PGW--
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 327 PM MDT Sat May 8 2021
At KCOS, cold front moving through the terminal as of 22z, with
n-ne winds gusting to 35 kts behind the front continuing into the
evening. Risk of a vcts behind the front from 22z-01z, though with
limited moisture, gusty and erratic winds will be the main features
of any storms. Clouds will thicken and lower overnight, with MVFR
cigs and a vcsh by 10z-12z Mon. Prolonged period of MVFR/occasional
IFR cigs and periods of showers/isolated thunderstorms then likely
through Sunday.
At KPUB, gusty w-nw winds will shift to the n-ne behind a cold
front 23z-01z. Clouds then thicken and lower overnight, with some
MVFR cigs and showers/isolated thunderstorms likely from Sunday
morning onward.
At KALS, strong w-sw winds gusting to 30-40 kts may produce some
blowing dust and brief periods of MVFR visibility into early
evening, with perhaps a vcsh adding to wind speeds as well. Winds
diminish with VFR conditions overnight and early Sunday.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 8 PM MDT this evening for COZ224.
Red Flag Warning from 11 AM to 8 PM MDT Sunday for COZ224.
&&
$$
SHORT TERM...PETERSEN
LONG TERM...PGW
AVIATION...PETERSEN
Area Forecast Discussion
National Weather Service Springfield MO
649 PM CDT Sat May 8 2021
.SHORT TERM...(This evening through Sunday)
Issued at 235 PM CDT Sat May 8 2021
A warm front was lifting northeast through the area this
afternoon. Breezy south winds with temperatures in the upper 70s
to lower 80s were occuring southwest of Springfield. Conditions
were much cooler across the eastern Ozarks as the front had not
lifted through there yet as clouds kept temps in the mid 60s. The
front will likely lift completely through the whole area by this
evening and will generally reach the Interstate 70 corridor before
stalling.
Shortwave energy was currently moving through the Rockies and a
deepening surface low was developing across southwest Kansas. A
strong elevated mixed layer/cap was moving into the area and will
keep precip chances virtually zero through this evening. By late
evening however, a very strong 850mb jet (70knots) will develop
from Oklahoma into southern Kansas. Thunderstorms will develop across
northern Kansas and will likely consolidate into a cluster,
becoming more linear with time. They will likely move through the
Kansas City area around Midnight and then start taking a turn
more to the east/southeast along the warm front and edge of the
capping inversion. This complex will likely begin affecting areas
north of Highway 54 sometime between 1-3am. MU capes in the
2000-2500j/kg range and 50kts of bulk shear will be more than
sufficient to sustain this convection as it moves into the area.
Given the expected linear nature, damaging wind gusts to 70 mph
will be the main risk, however large hail to the size of quarters
and a tornado will also be possible, especially with storms that
can interact with the warm front, or with segments that align
favorably with 0-3km wind shear vectors which look to be pointed
east about 40kts. 12z HREF probabilistic data as well as SPC probs
show the highest chances for severe storms tonight generally north
of Interstate 44, especially closer to the Lake of the Ozarks
region and locations near/north of Highway 54 after midnight.
Lesser chances are expected along/south of I-44 in the 3am-7am
timeframe, however there could still be a rather strong outflow
boundary/effective front that moves through with gusty winds.
Also, as the low level jet and surface low strengthens tonight,
should see surface winds increase out of the south to around 30mph
with gusts of 40-45mph possible, mainly from Springfield and
points west. Therefore a Wind Advisory is in effect from 10pm-7am
to account for this pre frontal wind threat.
PW values in the 1.5-1.7in range will likely allow for some very
heavy rainfall rates, however with a fairly progressive line,
should see mainly a limited/localized risk for flash flooding,
mainly with any cells that can train on the western periphery of
the complex as the llj feeds into it. This matches WPC slight risk
for excessive rainfall well. Overall rainfall amounts of 0.5-1.5
inches looks likely across the northern half or so of the area.
Locations south of Highway 60 will not see as much with this
system.
Strong cold air advection looks likely for Sunday and with cloud
cover remaining most of the day, high temps in the 60s will be
reached early in the day, with readings dropping into the lower to
middle 50s by afternoon. A rather raw and unseasonably cool Mothers
Day is expected.
.LONG TERM...(Sunday Night through Saturday)
Issued at 235 PM CDT Sat May 8 2021
Surface high pressure builds down into the central US which will
lead to several cool days that last through mid week. Highs in the
60s and lows in the 40s are a good bet. Can not rule out some
upper 30s for lows a few nights. While models do show some light
precip chances, a dry airmass and northeasterly winds with the
high pressure may preclude much rainfall through early week.
Temperatures look to moderate by late week with NBM generally
showing highs increasing into the 70s. Low confidence in rain
chances by the weekend with substantial model differences in the
overall pattern.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 620 PM CDT Sat May 8 2021
Thunderstorms over Kansas and Nebraska are expected to form into a
large complex that will move east into NW Missouri then shift
south across the forecast area tonight. Exact details are still
somewhat uncertain, but confidence is good given model
consistency. Leaned heavily on the HRRR model for timing and
coverage, which favors KSGF for the highest probabilities of
thunderstorms and most intense convection. KJLN and KBBG look more
on the periphery of the thunderstorm area. A damaging wind and
large hail threat will exist.
Strong winds aloft with gusts at the surface will also be a
continued and increasing concern tonight. As the low level jet
strengthens tonight, winds in the 2-4 thousand foot elevation
range should be 60 to 70 knots. This will lead to increased
surface gusts and low level wind shear.
Convection clears out Sunday morning.
&&
.SGF WATCHES/WARNINGS/ADVISORIES...
MO...Wind Advisory from 10 PM this evening to 7 AM CDT Sunday for
MOZ066-077-078-088>090-093>095-101>104.
KS...Wind Advisory from 10 PM this evening to 7 AM CDT Sunday for
KSZ073-097-101.
&&
$$
SHORT TERM...Burchfield
LONG TERM...Burchfield
AVIATION...Titus
...Update to aviation forecast discussion...
.DISCUSSION...
Issued at 259 PM CDT Sat May 8 2021
1930Z water vapor imagery showed a closed low over western MT with a
shortwave rotating through the base of the trough over the central
Rockies. A low pressure system as been steadily deepening across
southwest KS and southeast CO. The warm front extending northeast of
the surface low had lifted into south central NEB and far northeast
KS.
Severe thunderstorms remain probable tonight as guidance from the
CAMs as well as the synoptic scale solutions develop a complex of
storms and move them east along the warm frontal boundary tonight.
If there has been a trend in the CAMs, the HRRR has been a little
west with the initiation of storms and slower to bring them into the
western parts of the forecast area. Otherwise they`ve been pretty
consistent. Aircraft soundings near MCI show a substantial capping
inversion near the warm front at 18Z and one near ICT at 1822Z also
shows a cap over the warm sector. With the shortwave still to the
west, will need to wait for storms to form near the triple point and
move east. Forecast soundings from the NAM and RAP continue to
forecast a mid level weakness in the wind field causing the
hodograph to have an inflection. This would suggest storms would
tend to split with cell mergers causing disruption with the updrafts
and this seems to be what the CAMs depict this evening. However the
low level jet is progged to strengthen as the shortwave moves into
the plains and 12Z NAM forecast soundings show a brief window just
ahead of the cold front where the hodograph elongates and loses the
inflection. So there could be a risk for tornadoes into the evening,
especially if a supercell storm could set up on the south of the
convective cluster with uncontaminated access to the warm sector.
There continues to also be a large hail risk and damaging winds.
Some of the forecast soundings analogs show the potential for hail
over 2 inches in diameter and with storms expected to congeal into a
line, damaging winds may be the more widespread hazard to deal with
tonight.
As for flash flooding, there is a bit more uncertainty in excessive
rainfall for a couple reasons. First storms look to be fairly
progressive. If there was going to be a training concern, it would
be along the warm front, but eventually the cold front should catch
up and push the convection east and south. Second, models have
trended further north with the axis of heaviest rainfall, and this
makes some sense as the warm front has lifted into southern NEB.
North central and northeast Kansas missed out on the isolated
rainfall this morning and flash flood guidance of 2+ inches an hour
support the idea that the ground could take a quick one or two inch
downpour. Ultimately I think any flash flooding risk is going to be
to isolated for a watch and driven by repeated convection over the
same spot which isn`t a forgone conclusion.
Something else to be concerned with tonight are the gradient winds
behind the surface low. Models show the pressure gradient increasing
as the low passes south of the forecast area. There is the potential
for winds to remain up overnight and into Sunday morning, but it
looks like the stronger pressure gradient forcing and wind gusts are
coincident with the convection expected to occur. Even the HRRR
keeps wind gusts below advisory levels. Think that if the gradient
winds could reach advisory levels, it would be brief and right after
storms pass, with the gradient beginning to relax shortly after
storms move out. Because of this have opted not to issue a wind
advisory and will monitor trends.
Rain is expected to push east of the forecast area fairly early in
the day Sunday with surface ridging building in. Cloud cover for a
good portion of the day along with low level cold air advection is
expected to keep temps in the 50s on Sunday and breezy north winds
will make it feel cooler than that. The surface ridge remain over the
central plains through Wednesday keeping temps below normal. There
remains some potential for rain Monday through Wednesday as models
show some energy kicking out from the west and riding over the
central plains. There has been some variability in model runs with
respect to the energy lifting out across the area and as a result
POPs have bounced around a little bit. At this time it appears the
better forcing for precip may impact the area Tuesday. But
confidence in POPs is only so-so. Return flow redevelops Thursday
with temps warming into next weekend. Differences between the GFS
and ECMWF lead to more uncertainty in the forecast by Saturday, so
did not stray from the national blend of models. This has chances
for showers and thunderstorms Thursday night through Saturday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 610 PM CDT Sat May 8 2021
Only minor changes to going forecast. Convective complexes slowly
taking shape to the west and thunderstorm impacts are on track
for the next several hours. Post-complex winds continue to veer
into the end of this forecast though MVFR cigs will likely
persist.
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION...Wolters
AVIATION...65