Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/27/19
Area Forecast Discussion
National Weather Service Des Moines IA
1001 PM CDT Fri Apr 26 2019
...Updated for Forecast Trends...
Issued at 1001 PM CDT Fri Apr 26 2019
High resolution models, namely the HRRR and RAP, have been
shifting southward with the low pressure this evening. The 00z
NAM, which has come in recently, is ever so slightly (less than a
county) farther southward. Have tried to blend in some of the RAP
into the inherited forecast. Even with the southward shift, the
negating factor to adjusting headlines is the time of year and
that much of the snow will fall during daylight hours. This often
makes it challenging for snow to accumulate on roads, but can
occur with high snow rates, which are expected briefly.
.SHORT TERM.../Tonight through Saturday Night/
Issued at 405 PM CDT Fri Apr 26 2019
Active Weather Through Saturday Night
Short-wave trough will be kicking off the Rockies with surface Lee
Cyclogenesis taking place. This storm system will be moving rather
quickly across central/northern Plains into the Upper Midwest.
Biggest change in today`s 12z runs have been a southward shift in
both the GFS and ECMWF, the NAM track did not change all too much.
From a synoptic perspective, this system is looking to be in rather
good health for strengthening with plenty of warm-moist air to
provide fuel for diabatic processes to allow the surface low to
deepen rather quickly. Although the mid-level trough does not dig
far south, the PV anomaly associated with it is rather impressive.
Large scale lift will not be hard to come by with this system, as by
early Saturday morning most of Iowa will be within the left-exit
region of 100 knot jet streak at 300mb. Along the warm front, all
models are in good agreement that isentropic ascent will be rather
strong. In addition, there is no shortage of strong frontogenetical
forcing along the temperature gradients with this system. With that
being said, precipitation will be very widespread and abundant
across the entire forecast area, with the heaviest axis of QPF
across northern and northeastern Iowa. With respect to snow, this is
where the forecast gets tricky. Temperatures will largely determine
the actual snow amounts and snow accumulation that occurs. GFS and
ECMWF came in with surface temperatures closer to 40F. The NAM was
the cooler model from the 12z runs today. For temperatures on
Saturday, have elected to use NAM temperatures and bump them down a
few degrees, given strong dynamic cooling likely. If the
temperatures are able to cool during the afternoon, then the heavy
accumulating snow is likely. Another limiting factor to snowfall
could potentially be where the best lifting occurs. As already
established, there is no shortage of lift. However, examining model
cross section analysis does reveal that the bulk of lift may occur
below the DGZ. Model soundings also are not showing the best DGZs
from the 12z runs, which could be another concern. So even despite
the strong lift, if this does not occur in the DGZ this could
certainly limit snowfall amounts across the north. Thus with this
low confidence and multiple factors that could reduce snowfall, have
opted to stick mainly with a Winter Weather Advisory instead of
Warning for the northern counties, with the exception of Worth
County which has the best potential to see 6-7 inches of snow within
a 12 hour period. The other story with this system will be the winds
across most of the state. In the areas with heavy snowfall, wind
gusts will be up to about 30 miles per hour, which will present
impacts to visibility. However, in southwestern Iowa where the
precip will be mostly rain, wind gusts could reach up to 40-45 MPH.
This may push Wind Advisory criteria, but for now have held off. A
Special Weather Statement will likely be needed for southwest Iowa
tomorrow afternoon for gusty winds.
For Sunday, high pressure will come in and clear skies just as quick
as this storm system came in. Temperatures will be cooler than
normal for this time of year. With heavy rainfall from Saturday,
flooding may be an issue along some rivers and streams across the
.LONG TERM.../Sunday Through Friday/ Issued at 405 PM CDT Fri Apr
Active pattern stays the course through the long term period,
beginning with another shortwave trough quickly passing through
the northern Plains Sunday. Upper level QG forcing phases with low
level thermal advection to generate widespread rain showers by
Sunday evening, continuing into the overnight hours before
tapering off early Monday. Precip trends remain on track from
previous forecast as models wavered little with their latest runs.
QPF amounts look to be on the lighter side for most of the
forecast area, but some in southern Iowa may see 0.50"-1" where
elevated instability could support some convective activity.
Early next week the synoptic pattern transitions to a southwesterly
flow regime over the western two-thirds of the CONUS. Several
shortwaves propagating through the mean flow look to deliver
multiple periods of showers and storms to the state. The first such
wave ejects out of the Four Corners on Tuesday/Wednesday and
deamplifies as it crosses the central Plains. Heaviest precipitation
and convection likely remains along and south of a stationary front
draped across OK through MO. Isentropic ascent north of the frontal
boundary should generate rainfall over the cwa, highest chances
residing across the south. Limited instability north of the front
will suppress most potential for severe weather, but can`t rule
out some rumbles of thunder in our area. Significant model
difference arise past Wendesday which lends to high uncertainty
with the forecast. Low chances PoPs remain scattered through the
Day 5-7 periods, but is more an artifact of the blends. PoPs
should become more focused as models begin to hone in on a common
.AVIATION.../For the 00Z TAFS through 00Z Saturday evening/
Issued at 657 PM CDT Fri Apr 26 2019
VFR conditions will deteriorate into MVFR as low pressure swings
through the region bringing rain showers to the area. Colder air
will cause the rain to mix with snow at ALO and change to snow at
MCW during Saturday and this will likely bring at least IFR
conditions. Strong, gusty winds will also accompany this storm
through much of the day before decreasing after 00z Sunday.
Restrictions will improve into VFR late in the afternoon over
northern and western Iowa.
Winter Weather Advisory from 7 AM to 7 PM CDT Saturday for
Winter Storm Warning from 7 AM to 7 PM CDT Saturday for IAZ007.
Area Forecast Discussion
National Weather Service Quad Cities IA IL
946 PM CDT Fri Apr 26 2019
Issued at 935 PM CDT Fri Apr 26 2019
Have added sprinkles into forecast rest of evening into
the early overnight, with first bout of lift attendant
to passing weak mid level wave. Lift is fighting dry low
levels and mostly evaporating before reaching the surface,
but have seen evidence of a trace at a couple of obs out
Otherwise, with dynamic spring storm system to impact the
area tomorrow the Latest NAM is trending a tad slower and
further southwest from previous run. However, it`s still
clustered with most solutions, which shifted south a bit
today. RAP is on the southern edge of the guidance envelope
and colder, and would support primarily snow north of
Hwy 30 with potential for a bit higher amounts, and possible
for changeover to snow further south through I-80 corridor
toward late in the day through early evening before system
exits. Per vort max trends can`t rule out a bit more change
yet in the track of storm system, which if any delta could be
of a bit southerly and colder similar to RAP model. With the
expectation of a very sharp cutoff from accumulation to
nothing, the slightest shift in track will have huge impacts
on forecast. Thus, for now we`ve opted to maintain the current
watch and let the next shift review the rest of 00z guidance
before making any changes. Stay tuned!
Issued at 250 PM CDT Fri Apr 26 2019
Windy conditions representative of this "warm season" clipper
pattern are taking place in the transition from the rapidly
progressing areas of strong high and low pressure. Today, northwest
winds and dry air are sweeping into the region, with winds of 20 to
30 mph, and a few gusts to around 40. Looking to the west, strong
warm advection is already ongoing in Nebraska, in response to the
small, but intense upper wave crossing through Idaho and Utah this
.SHORT TERM...(This Evening through Saturday Night)
ISSUED AT 250 PM CDT Fri Apr 26 2019
A rapid transition to the incoming storm will happen tonight,
with the main challenge being snow totals with this storm. There
has been a decided shift south today in model guidance, much like
often occurs when forecasting a clipper snow system. To be honest,
a change in track is still possible yet as this storm arrives.
Like a clipper, this is a small system in size and scope, but very
intense. All signs point to an extreme frontogenesis event
impacting our CWA, especially the north 1/2. A low amount of
MUCAPE is likely going to be entrained into this process, allowing
for some embedded thunder near and north of the low track, which
should move near Highway 34. The amount of rain is challenging, as
extreme dynamic lift will wring out every bit of QPF it can while
the system moves past. In the north, enough dry air below 700 mb
will evaporatively cool the atmosphere aloft for it to change to
snow, after the precip develops. This means, after 3 to 4 hours of
rain, some areas will change to snow north of the low track. The
intensity of lift suggests thundersnow and bursts of heavy snow
are possible, leading to a potential that northern areas could
reach 5-8"+, THIS IS NOT A CONFIDENT TOTAL! None the less, the
potential is there, and with the southern global model shift, a
watch seems warranted in the northern counties.
If snow is heavy, it will have high impact to trees that are leafing
out, as winds will be 30 to 40 mph. Roads are likely going to be
slushy, and visibilities poor, thus it`s far from a classic winter
Farther south, rain and thunderstorms will continue, with the peak
intensity as the low passes by mid afternoon. Winds will rapidly
transition to north, and increase to 25 to 35 mph, gusting to 45 for
a period of 2 to 4 hours, as the high pressure behind this low will
be in place over the CWA, by early Sunday morning! Temperatures
will be critical to snow transition, but are forecast to reach the
lower 60s south, to near 40 north. That`s likely the 8 AM
temperature in the north, with falling readings to the mid 30s by
Noon and lower 30s by mid afternoon. As temperatures reach 34, a
full transition to snow is expected.
Elsewhere, snow will likely occur in a short period through I-80 as
the system pulls away. This may lower visibilities, but should not
accumulate significantly on anything.
Frost/Freeze conditions are expected overnight, and a headline for
that is likely going to be issued at a later time.
.LONG TERM...(Saturday Night through Friday)
ISSUED AT 250 PM CDT Fri Apr 26 2019
An active weather pattern will continue next week with several
rounds of rain, possibly heavy, expected. The models have suggested
a slight southward shift with the heavy rain.
Quiet, dry and cool conditions will be seen Sunday with below normal
Assessment...high confidence on another storm system. Low confidence
on track and rainfall amounts.
The next storm system will impact the Midwest Sunday night into
Monday. However, the models continue to disagree on the track the
storm system. The difference in track appears to be related to the
position of the developing front and the strength of the high from
the Great Lakes into the upper Midwest.
The ECMWF and FV3 have the front from Kansas into the Ohio Valley
with the heaviest rainfall from Missouri into central Illinois.
The GFS is slightly north of the ECMWF and FV3 solutions with the
front from Kansas into northern Indiana. The heavy rain is along the
IA/MO border into northern Illinois.
The CMC global is the most ominous as it brings heavy rainfall from
southern Iowa to northern Illinois.
The model consensus has likely to categorical pops Sunday night with
chance to categorical pops on Monday.
Monday night on...
Monday night through Wednesday
Assessment...high confidence on another storm. Low confidence on
track and rainfall amounts.
The track of this storm system will depend upon where the front is
The ECMWF keeps the area dry Monday night and Tuesday with rain
moving in Tuesday night and Wednesday. The ECMWF has the heaviest
rain from the IA/MO border into northern Illinois.
The FV3 keeps the area dry Monday night with the next storm system
arriving Tuesday and Tuesday night with the heavy rain across
Missouri into the southern half of Illinois. The FV3 has Wednesday
The CMC global has heavy rain Monday night and Tuesday from Missouri
into southern Illinois with very light precipitation Tuesday night
The GFS has Monday night dry with a system moving through on Tuesday
with another storm system Tuesday night into Wednesday. The GFS has
the heaviest rain from Missouri into northern Illinois on Tuesday
and then Missouri into central Illinois Tuesday night and Wednesday.
Given all the differences in timing and position of the front/heavy
rainfall, the model consensus has slight chance to chance pops
across the south third of the area Monday night, chance to likely
pops across the entire area Tuesday and Tuesday night, and chance
pops on Wednesday.
Wednesday night through Friday
The models diverge considerably with their respective solutions in
regards to the sensible weather.
The ECMWF has dry conditions Wednesday night through Friday as a
strong Canadian high slowly moves through the Midwest.
The GFS has another storm system moving through the Midwest
Wednesday night through Thursday night with dry conditions on
The CMC global has mainly dry conditions Wednesday night followed by
dry conditions Thursday through Friday.
The FV3 has two or three weak systems moving through the Midwest
Wednesday night through Friday bringing light precipitation to the
The model consensus is biased toward the GFS solution and has slight
chance to chance pops Wednesday night and Thursday night, chance
pops Thursday, and dry conditions on Friday.
.AVIATION...(For the 00Z TAFS through 00Z Saturday Evening)
ISSUED AT 655 PM CDT Fri Apr 26 2019
Potent spring clipper system to bring deteriorating conditions in
rain/snow and strong winds Saturday.
Primarily VFR tonight, but lowering to MVFR and IFR Saturday.
Rain changing to snow by midday at DBQ with moderate to heavy snow
and several inches of accumulation into early evening. Thundersnow
is possible. Mainly rain at CID and MLI, but mixing or changing
to a period of snow from mid afternoon into early evening before
ending. Predominately rain at BRL, with some dry hours possible
late morning and early afternoon. Then showers expected to return
in the afternoon which may be accompanied by thunder.
Generally 2-5SM in the precipitation, with periods of around 1/2SM
or less at DBQ in heavy snow.
Becoming strong/gusty from E/SE at 20-30+ kts on Saturday shifting
from northeast at 25-40+ kts at northern sites Saturday PM. BRL
is likely to see a lighter period of winds for a time in the
afternoon with the low passing nearby, but then will become strong
from NNW 25-40+ kts by late afternoon.
Issued at 848 PM CDT Fri Apr 26 2019
Only minor rises of a tenth of a foot or two were made to the
Mississippi River crest forecasts this evening.
The Mississippi River will remain high or in flood through the
Memorial Day Weekend.
The Mississippi is rising from Dubuque LD11 down through
Burlington. South of Burlington the river will begin rising on
The crest is currently between La Crosse and Prairie du Chien,
Issued at 320 PM CDT Fri Apr 26 2019
HOWEVER, the current 7 day Mississippi forecasts do not, repeat,
do not take into account predicted snow on Saturday and rainfall
from Sunday night through next Thursday.
The weather models indicate a narrow band of heavy snow will occur
on Saturday from northern Iowa into southern Wisconsin. Runoff
from this snowmelt will cause a slightly higher and delayed crest
on the Mississippi.
The active weather pattern continues well into next week with the
potential for several rounds of rain, some of which may be heavy.
However, the weather models vary greatly on possible storm tracks
and potential rainfall amounts.
The high probability of above normal rainfall next week is
expected to result in rises on tributary rivers in eastern Iowa
and northern Illinois.
Looking further out into May, the Climate Prediction Center
indicates a 40 percent chance of above normal rainfall through
the first 10 days of May along with a slight risk of heavy
Individuals with interests along the Mississippi River are
strongly urged to pay attention to future weather and river
IA...Winter Storm Watch from Saturday afternoon through Saturday
evening for Delaware-Dubuque-Jackson.
Winter Weather Advisory from 1 PM to 10 PM CDT Saturday for
IL...Winter Storm Watch from Saturday afternoon through Saturday
evening for Carroll-Jo Daviess-Stephenson.
Area Forecast Discussion
National Weather Service Lubbock TX
835 PM CDT Fri Apr 26 2019
Thunderstorms approaching from eastern New Mexico have been
gradually weakening over the past 90 minutes, but holding together
well enough to spread fair coverage of rain chances across the
extreme southwest Texas Panhandle and northwestern South Plains
this evening. HRRR runs have been most agressive with forecast
coverage though indicate what looks like appropriate weakening.
Have trended a little less than HRRR coverage but also expanded
isolated thunder coverage a little larger after midnight. Isolated
strong wind gusts remain a threat and will add a mention to the
overnight Hazardous Weather Outlook. RMcQueen
.PREV DISCUSSION... /issued 557 PM CDT Fri Apr 26 2019/
Breezy south to southwesterly winds will continue this evening
into the early morning hours on Saturday. Isolated thunderstorms
currently in eastern New Mexico will attempt to make it into the
region late tonight or early Saturday morning. However, this
activity is not expected to make it to any of the terminals. A
cold front will move into the area Saturday afternoon shifting
winds to the northwest at KLBB and KPVW and to the northeast at
PREV DISCUSSION... /issued 351 PM CDT Fri Apr 26 2019/
Well, we appear to be heading into a busy weather period. Our
immediate question - will we have a repeat of overnight/early
morning showers/storms? Storms are once again breaking out over the
high terrain of NM this afternoon and slowly pushing eastward. Our
upper flow is transitioning from favorable NW to westerly (and weak)
flow; however, a LLJ of 30-40 KT is expected to spread south into
our FA and strengthen to 45 KT (few pockets of 50 KT) It will veer
with time to the SW, so that is not as helpful, though if there are
storms, it could mix down and create strong wind gusts at the
surface. The main impulse feeding these storms is well to the north,
entering the Central Plains tonight. All this to say, there may be
just enough energy, moisture and assistance from the LLJ tonight to
produce another small round of showers/storms across the FA like
last night/this morning.
As we head into tomorrow afternoon, we do see about the eastern half
of the FA in the marginal risk category for severe thunderstorms.
This is a highly conditional situation, in fact, much of our rain
this week will be in the conditional category. A front is poised to
push through around the eastern two-thirds of the FA tomorrow and
stall. Storm initiation is expected along the front near a weak
dryline feature, but there are caveats. The first, which is always a
concern out here, is moisture. Moisture transport appears to be
cutoff early Saturday with the next good surge not coming until
Monday. Second, we`ll be capped. There will be plenty of energy, on
the order of 1000-1500 J/kg, but if we can`t warm enough to erode
the cap, it`ll be of no use. There may be a brief window in the late
afternoon to early evening that the cap gets weak enough to
overcome, but we`ll have to watch that closely tomorrow.
Monday is much like last Monday where we had a front moving through
and an upper low off over the Desert SW. Once again, we`ll have to
watch to see how far south the front makes it on Monday to determine
where the brunt of the storms (possibly severe) will be. Much like
last Monday night, storms will move north of the frontal boundary,
able to produce locally heavy amounts of rain. As the upper trough
approaches and eventually moves by on Tuesday, it will be the track
of this feature that determines the highest rainfall amounts. Attm,
the current track has those highest amounts moving just to our
south, but we aren`t left high and dry either. This is Day 5, so
much can change by then. As for highs on Tuesday, models were
extremely spread, based on whether we are dry or not. Chose to go
cooler on this package as rainfall from the previous day would aid
in cooler temps, plus cloud cover should abate the highest temps.
Did not, however, go with the coldest temps, as we`ll have to wait
until the track of the storm shows itself. Another disturbance
approaches Thursday, with a shot at storms, followed by another
front, which, you`ve probably guessed by now, appears to be the
focal point for another round of storms late Thursday night. An
interesting weather period...a challenging one...and one that we
must keep a very close eye on.
Area Forecast Discussion
National Weather Service Marquette MI
727 PM EDT Fri Apr 26 2019
.SHORT TERM...(This evening through Saturday)
Issued at 437 PM EDT FRI APR 26 2019
Water vapor imagery and RAP analysis show a negatively tilted trof
extending from northern Ontario to the Carolinas. Shortwave that was
over southern Manitoba 24hrs ago is now over the northern Great
Lakes. This shortwave has ushered in much colder air on blustery nw
winds today. Strongest measured wind gusts so far was at the
Munising ASOS at 49 mph at 1900z. Otherwise, gusts have generally
been under 40 mph. Low-level moisture, upslope winds and daytime
heating helped to generate some -shra across portions of the higher
terrain of the nw and n central fcst area earlier today. Some snow
was also reported. After rising to around 50F this morning over the
e, strong nw winds/caa has dropped temps into the mid 30s to lower
40s. With increasing sunshine toward the MI/WI stateline, temps in
that area are currently pushing into the upper 40s.
A quiet short term is shaping up after the winds this evening. Low-
level winds will reach their max over the next few hrs over the e
half of the fcst area. So, before the sfc layer begins to stabilize
a bit with the setting sun, there should be higher wind gusts yet to
be observed. Per momentum transfer suggested by fcst soundings,
gusts should frequently be in the 35-45mph range with the potential
of up to 50mph. To the w, winds will be lighter, lightest toward
KIWD. Winds will diminish w to e during the evening/overnight.
Already by late evening, winds will have dropped off to under 5mph
over the far w. Winds may continue to gust to 15-25mph thru the
night over the e. A few -shra/-shsn are possible over the e this
evening with indication of sharper 850mb troffing pushing down the
far eastern part of Lake Superior. As for temps, with light winds
and a dry air mass over the w (precipitable water under 0.2 inches),
favored the low side of guidance. A few of the traditional interior
cold spots may slip blo 20F. Winds will keep temps higher over the
e, upper 20s/around 30F.
Although a very dry low-level air mass will dominate on Sat, models
suggest considerable high cloudiness spreading across the area in
association with shortwave tracking e toward the southern Great
Lakes. With sun dimmed by high clouds and gradient northerly winds
across Lake Superior, it will be a cool day. Expect highs only in
the mid 30s/around 40F near Lake Superior to the mid 40s interior w
.LONG TERM...(Saturday night through Friday)
Issued at 431 PM EDT FRI APR 26 2019
Models suggest that a progressive pattern will prevail through the
CONUS as a mid level trough over north central Canada slowly drifts
southwest into western Canada. Shortwaves moving through the
northern Great Lakes will bring pcpn chances to Upper Michigan
Monday and again from late Wed into Fri. Temperatures are expected
to remain at or below normal through the period.
Saturday night into Sunday, Mid level and sfc ridging will continue
to dominate the region with dry weather. After a cold start with
favorable radiational cooling conditions allowing temps to drop into
the lower 20s inland, expect gradual warming as highs rebound into
the mid and upper 40s north to the lower 50s south.
Sunday night into Monday, A shortwave with moderate to strong 700-
300 qvector conv will bring pcpn through Upper Michigan. Forecast
wet-bulb zero heights suggest that much of the pcpn will fall as
snow before daytime warming and weak lift move in during the
afternoon. With QPF values at least into the 0.20-0.30 range, a few
inches of wet snow may accumulate over the west half, mainly on
Tue, expect dry weather in the wake of the Mon shrtwv as high
pressure builds toward the region from the Plains.
Wed-Fri, there is lower confidence with the timing/strength of the
shrtwv and sfc trough lifting northeast from the plains from Wed
into Thu. Although the GFS keeps pcpn south of Upper Michigan,
several GEFS members and the ECMWF bring rain into the area from the
southwest by late Wed into Wed night. Uncertainty lingers into the
end of the week as the GFS/GEFS bring more substantial pcpn, as rain
possibly mixed with snow, into the western Great Lakes while the
ECMWF is weeks and farther nw with any impacts.
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 726 PM EDT FRI APR 26 2019
AS weak high pressure builds into the region, winds will relax with
speeds dropping below 10 knots very early on in the forecast,
similar to what has already occurred at KIWD. VFR conditions to
prevail through the forecast as drier air moves in. Expect
increasing mid level clouds for Saturday.
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 437 PM EDT FRI APR 26 2019
NW gales of 40-45kt over the e half of Lake Superior will gradually
diminish to blo gale force tonight as low pres over southern Ontario
lifts ne and pres gradient weakens. Winds have already mostly
diminished to under 20kt over western Lake Superior. On Sat, winds
should be mostly under 15kt over the w half of Lake Superior while
15-25kt winds are expected over the e half. Winds will mostly be
under 15kt on Sun with a high pres ridge over the area, but as the
ridge shifts e, winds will begin to increase Sun night and Mon. SE
winds will reach 15-25kt over the central and eastern part of the
lake on Mon.
Wind Advisory until 8 PM EDT this evening for MIZ005-006-013-014-
Wind Advisory until 2 AM EDT Saturday for MIZ007.
Gale Warning until 4 AM EDT Saturday for LSZ251-267.
Gale Warning until 2 AM EDT Saturday for LSZ250-266.
Gale Warning until 8 PM EDT this evening for LSZ248-249-265.
Gale Warning until 3 AM EDT Saturday for LMZ248-250.
Gale Warning until 1 AM EDT Saturday for LMZ221.