Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/06/20
Area Forecast Discussion
National Weather Service Bismarck ND
832 PM CDT Sun Apr 5 2020
.UPDATE...
Issued at 832 PM CDT Sun Apr 5 2020
Latest summary of radar sites across the region continue to show
isolated showers south central through the James River Valley.
Harvey had a brief period of mixed precipitation, rain/snow per
Carrington BUFKIT sounding and surface observation. Will continue
to see this trend over south central and the James River Valley
through 06z as mentioned in the previous discussion. Threat for
thunderstorms appears to remain in South Dakota, but will watch
for any changes. For now, will maintain showers without a mention
of thunder in the gridded forecast. Stratus/fog forecast remains
on track this evening (beginning around 04z) and through Monday
morning. It is possible the stratus will linger over the James
River Valley well into Monday afternoon per RAP13 925mb relative
humidity field.
UPDATE Issued at 556 PM CDT Sun Apr 5 2020
Latest water vapor satellite imagery shows southwest flow aloft
with an initial 700mb shortwave trough now sliding through the
northern James River Valley. Surface observations and radar
reflectivities over this area show clouds are based between 9000ft
and 11,000ft above ground level, and no precipitation has reached
the surface; cloud bases just a tad too high. Looking farther upstream,
clouds are developing along with increasing radar reflectivities
over south central as a few more mid and upper level shortwaves
approach this evening. SPC has a general thunderstorm outlook/non-
severe across south central and the James River Valley tonight.
Surface low associated with a shortwave in southwest South Dakota
will scoot into north central South Dakota by 06z Monday. Comparing
current surface based cape and most unstable cape from SPC mesoanalysis
to the NAM/GFS, both seem to capture the 100-500J/Kg of cape across
western South Dakota. The NAM takes this area of instability up
to and over our border by around 06z, about 200 J/Kg. The GFS
dampens/washes the cape out to less than 100 J/kg along and south
of our border by 06z. Low level lapse rates appear meager at this
time and are forecast to continue through the evening, however mid
level lapse rates remain sufficient at 7.5C/Km. The HRRR simulated
composite reflectivity is the most aggressive in generating the
highest reflectivities compared to the remaining high resolution
guidance; however there is agreement that some precipitation will
develop south central and into the James River Valley now through
06z Monday. Based on current radar trends agree with this scenario,
and will expand current PoPs to account for this. Will hold off
on thunder mention with this update and monitor the upstream radar
trends and observations before adding thunder to the grids.
Stratus and fog as mentioned from the previous discussion
continues to have support from the high resolution guidance and
BUFKIT soundings. Continued easterly flow/upslope will result in
stratus/fog to form north central this evening, then expand south
overnight.
&&
.SHORT TERM...(This evening through Monday)
Issued at 246 PM CDT Sun Apr 5 2020
Patchy to areas of fog are again featured for tonight, forming
mainly after midnight and slowly burning off Monday. A cool low
layer will be over run by warmer temperatures aloft favoring fog
formation. There may be a small risk of some patching freezing
drizzle late tonight across the James river valley but have not
included this yet. few showers will continue across teh James
River Valley this evening then end.
On Monday, mainly cloudy skies are expected. Increasing
southerly winds and moisture will crate some instability, and a
few thunderstorms are possible across teh south late Monday into
Monday evening.
.LONG TERM...(Monday night through Sunday)
Issued at 246 PM CDT Sun Apr 5 2020
It will be mild and breezy Tuesday, with highs in the lower 60s
across much of southwest and south central North Dakota, and the
50s elsewhere. So by Tuesday evening much of the new snow from
this past week will be well on its way to melting.
A cold front will pass through Wednesday, and it will be breezy
to windy and blustery, with highs just into the lower 40s.
However not much in the way of precipitation is expected in the
extended. Wednesday, Thursday and Friday expected to be dry, with
some chances for light snow Saturday and Sunday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 556 PM CDT Sun Apr 5 2020
Stratus and fog will develop across the northern terminals this
evening, 04z-06z Monday, then expand south and east overnight,
reaching KDIK/KBIS/KJMS 09z-12z. Expect IFR to LIFR cigs, and
vsbys ranging from MVFR to VLIFR, especially at KMOT/KDIK.
Improvement to VFR conditions are forecast at KXWA/KDIK by 18z,
however cigs at the remaining terminals remain in MVFR/IFR status.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...KS
SHORT TERM...waa
LONG TERM...waa
AVIATION...KS
Area Forecast Discussion
National Weather Service Louisville KY
857 PM EDT Sun Apr 5 2020
.Forecast Update...
Issued at 856 PM EDT Sun Apr 5 2020
Bumped winds a little stronger over the next few hours to match
current conditions and cleared skies just a little. Also, added
around a 10% chance of precip in the northern half of our area. The
HRRR has been hinting at some light showers forming south of
Louisville and moving east expanding as they move into the
Bluegrass. Currently, watching light returns over southern Indiana
in Orange and Washington Counties. If anything more forms tonight,
it will be very light and isolated in nature. Not expecting much.
&&
.Short Term...(This evening through Monday)
Issued at 250 PM EDT Sun Apr 5 2020
Surface high pressure centered over Lake Michigan this afternoon
will drift east through Monday. Aloft, weak ridging over the eastern
2/3 of the country will combine with the surface ridge to result in
clear to partly cloudy skies for much of the forecast area over the
next 24 hours. The main exception to this will be areas north of
the Ohio River, where low clouds persisted much of the day today.
With a weak surface pressure gradient associated with the Lake
Michigan high, the low cloudiness will slowly erode rather than
quickly move out. Even there, however, Monday looks to see more sun
than today.
Temperatures will bottom out from 45 to 50 tonight, and in the lower
70s for highs Monday. Those highs will be a pleasant warm-up for
southern Indiana, where the clouds held temperatures into the upper
50s for many today. Elsewhere, Monday`s highs will be at or just
above today`s maximums, all of which are 5-10 degrees above seasonal
norms.
.Long Term...(Monday night through Sunday)
Issued at 245 PM EDT Sun Apr 5 2020
Unsettled weather looks to start the long term as an upper level
shortwave over the northern Great Plains dives SE towards the Ohio
Valley. SW winds at the sfc will allow for ample warm Gulf moisture
to be funneled into the region, causing dewpoints to rise in the
upper 50s to low 60s, with afternoon highs forecast to climb into
the mid 70s. Current soundings show relatively steep mid-level lapse
rates (7-8 deg C/km), decent instability (1000-1500 J/kgK, along
with long hodographs, implying that organized convection may
certainly develop. However, this will largely depend on how much we
can destabilize throughout the day, so have decided to continue with
model blend of PoPs at this time.
Another round of showers/storms looks to impact the region late
Wednesday night into Thursday morning ahead of a strong cold front.
Given the current instability and shear values in place, wouldn`t be
surprised if a few of these storms became severe ahead of the line.
By Thursday evening, the aforementioned cold front will have exited
the region. While a few post-frontal showers may linger in its wake,
expect mostly dry conditions and cooler temps to prevail heading
into the weekend. A frost/freeze threat may even develop Friday
through Sunday morning as overnight lows fall into the 30s.
&&
.Aviation...(00Z TAF Issuance)
Issued at 731 PM EDT Sun Apr 5 2020
A weak upper wave and pool of deeper moisture near STL this evening
will move to the east and may bring lower clouds and perhaps a small
shower or two to southern Indiana and north central Kentucky between
midnight and dawn. Down south at BWG clouds should be fewer but that
will leave the door open for some light fog to form.
Morning low clouds should become VFR over the course of the day
tomorrow through lifting and possibly scattering.
Winds will be light through the period with surface high pressure in
the region.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...None.
&&
$$
Update...KDW
Short Term...JBS
Long Term...SSC
Aviation...13
Area Forecast Discussion
National Weather Service Marquette MI
630 PM EDT Sun Apr 5 2020
.SHORT TERM...(This evening through Monday)
Issued at 411 PM EDT SUN APR 5 2020
WV imagery and RAP analysis indicated a mid/upper level trough off
the northern CA coast and a broad ridge over the southeastern CONUS
resulting in anticyclonic westerly flow through the northern Plains
and northern Great lakes. An upstream shortwave trough was moving
into western North Dakota. At the surface, high pressure centered
over Lake Michigan that has brought sunshine and light winds to the
area was slowly moving off to the east. An initial batch or WAA
mid/high clouds was sliding through Upper Michigan.
Tonight, as the North Dakota moves quickly toward the area,
increasing 290k-300k isentropic lift will bring thickening clouds
across the area. Some light pcpn may also develop but should not
amount to more than a trace or a few hundredths. With the
increasing cloud cover, temps should remain mainly above freezing
or slowly climb as any pcpn moves in. Since forecast soundings
indicate a substantial low level dry layer, evaporative cooling
could bring some snow or freezing rain at the onset.
Monday, Some lingering WAA/isentropic lift will support the
potential for additioinal light rain showers over mainly the east.
However, any lift by midday and afternoon will be weak with mainly
just sprinkles at the most expected. Temps will rebound into the
upper 40s to mid 50s.
.LONG TERM...(Monday night through Sunday)
Issued at 349 PM EDT SUN APR 5 2020
On the hemispheric scale, not too much change from the past day or
so with the above normal temps starting the week becoming near to
perhaps slightly blo normal to end the week and into the weekend.
Currently, there remains a strong positive height anomaly near
Hudson Bay with a weakening ridge across the Pacific that will shift
E to the West Coast by the middle of the week. At the same time,
troughing remains just off the West Coast and across the Canadian
Rockies as well as to the S of Greenland. Over the next few days,
ensemble-based forecasts suggest troughing over the West Coast will
dig south with a cutoff feature over the desert SW developing,
bringing a split flow pattern across the CONUS. Through the middle
portion of the week, the Canadian Rockies trough shifts E over the
Great Lakes region as a few shortwaves pass over the region bringing
a few separate chances for precipitation. Late this week, the cutoff
feature shifts E over the southern CONUS and congeals with E CONUS
troughing. Heading into this upcoming weekend and into next week,
medium range ensembles suggest ridging to persist across the Pacific
and develop across the Atlantic. In between, troughing will develop
across the central CONUS persisting through the week.
Monday night into Tuesday begins with rising heights as a mid-level
ridge builds northward. This building ridge is cut short as models
suggest a shortwave will approach from the west. Ahead of this wave
and an associated sfc trof, isentropic ascent and moisture flux
convergence increase as -SHRA develops in the morning across the W
and shifting E into the afternoon. Model Q-vector conv suggests that
the best forcing remains across the northern half of the UP, though
the 12Z GFS brings this forcing across all the UP. Synoptically
speaking, still looks like 0.25 to potentially 0.5 inches of rain is
possible across Upper Michigan. There is some potential for
increased amounts locally in any thunderstorms that develop. GFS
still suggests up to 500J/kg of MUCAPE to move into the UP, mainly
along the WI-MI state line. NAM has consistently not rendered this
solution. Quick look at soundings show this CAPE would be based well
off the sfc, closer to 3-5kft...with some positive area still there
to overcome.
Looks to dry out quickly Tuesday night before the next trough in the
line approaches Wednesday evening into Tuesday. This is also the
trough that looks to change the above normal temperature trend back
towards normal to slightly blo normal. The associated cold front
with this trough moves into western UP Wednesday evening as models
suggest q vector conv and associated -shra begins on either side of
21Z Wed. As this trof moves through, sfc pres begins to deepen which
increases forcing and the instability. Look for an increase in winds
through the night on Wednesday and maintaining through Thursday
evening. A quick fall in heights, increasing CAA, and colder
temperatures aloft will allow the boundary layer to mix quite well
with gusts over 30mph appearing likely, esp along the Lake Superior
shoreline. Gusts approaching 40 mph are also possible across the
eastern half of the UP along Lake Superior and across the Keweenaw.
With 850mb temps falling to near -10C, probably won`t see any lake-
effect shra/shsn, but drizzle/flurries seem possible. At any rate,
it will be gloomy and feel chilly after this week`s warmer temps
with plenty of wind and lake-effect clouds around.
With the colder air aloft and some CAA still around into Friday,
seems likely the UP will be keeping the clouds and maybe some
flurries/drizzle around. On Saturday, models suggest another wave to
move across Upper Michigan bringing another chance for showers. The
EC looks much more impressive than the GFS/GEM at this time, but
they all show some showers across the CWA at some point.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 630 PM EDT SUN APR 5 2020
VFR conditions will continue through the forecast period. However,
there may be some light rain or snow showers at KCMX and KSAW
overnight into Monday.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 411 PM EDT SUN APR 5 2020
Expect light winds of 15 kts or less across Lake Superior through
tonight as high pres lingers over the area. Easterly winds will
increase to 20 knots Mon as a low pres trough approaches from the
west. East to southeast wind gusts could increase up to 25kt over
the east and north central parts of the lake on Tue as the gradient
tightens ahead of the trough. The next big increase in winds will
occur late Wed into Thu as a cold front moves through the area and
west winds increase to 20-25 knots late Wed into Wed evening and
then become northwest gales of 35-40 knots late Wed night into Thu,
strongest over the east half of the lake.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...JLB
LONG TERM...JAW
AVIATION...07
MARINE...JLB
Area Forecast Discussion
National Weather Service Pocatello ID
406 PM MDT Sun Apr 5 2020
.UPDATE...
Updated forecast to include isolated thunderstorms with small hail
possible across southern Idaho. Radar this afternoon showing
convection across the Magic Valley moving northeastward. High
resolution models show some thunderstorm potential continuing into
the early evening hours.
13
&&
.PREV DISCUSSION... /issued 204 PM MDT Sun Apr 5 2020/
SHORT TERM...Tonight through Tuesday night. Upper low continues
to slowly push into central California tonight through Monday.
Southwest flow aloft spreads moisture across East Idaho for
continued threat of mainly showers tonight and early Monday. Snow
levels stay above valley floors, keeping near a high of 7000-7500
ft across a broad swath of the southeast half of the region
overnight. Instability increases during the day Monday, with
storms strong enough to support at least small hail and gusty
winds. An isolated storm may become stronger, but widespread
threat for severe storms is not expected at this time. Northern
stream trough pushes moisture east late Monday into early Tuesday,
but proximity to advancing low could keep precipitation threat
going in the southern portions of the region into Tuesday.
Otherwise the trend will be for drier conditions for the rest of
the region. DMH
LONG TERM...WEDNESDAY THROUGH NEXT SUNDAY...
Model agreement remains excellent in moderate high pressure
providing mostly sunny skies and a taste of spring for Wed through
most of Fri. High temps are forecast to rise about 5-10 degrees
above climatological norms, especially in the eastern Magic Valley,
Snake Plain, and Raft River region, topping out in the 60s in these
areas and generally 50s elsewhere. Our official, NBM-led forecast
has come down a degree to two compared to yesterday, and still leads
the pack by several degrees compared to projections off of some of
it`s individual input models such as the GFS and ECMWF. However, it
still lies near some decent clustering in the ensembles,
particularly the EC, so it appears reasonable. By Fri afternoon,
model agreement diverges, and forecast confidence drops off. The
Canadian maintains more pronounced high pressure ridging, while the
EC starts to wrap a shortwave trough around a closed low in central
Canada, brushing at least our eastern highlands with a few showers.
The GFS has more of a NW flow moisture signature, also generating a
few showers. All 3 of the core long-range models generally feature a
wetter picture for the weekend as SE Idaho resides along the western
fringes of a Central-Eastern US longwave trough, but there really
isn`t any agreement in the details. For now we carry a low-
confidence chance of showers both days, along with slightly cooler
temps. Assuming adequate lift, the mild temps may help generate
enough instability to support some thunderstorms during this period,
but did not add thunder to the forecast this far in advance,
especially considering the poor model agreement. - KSmith
AVIATION...
A closed low pressure center near the CA coast will continue to
provide unsettled weather and rounds of rain/snow showers. Used the
12z HREF ensemble suite and RAP to try to time out periods of
predominant -SHRA, and blanketed VCSH everywhere else through the
end of the TAF period. Model-projected lifted indices of -1 to -3 C
may support a few thunderstorms this afternoon through 02-03z,
especially the further south you go, so added VCTS to
KBYI/KPIH/KIDA. Cigs/vsbys should generally remain VFR at these
terminals as well as KSUN, except perhaps under a heavier
shower/storm (temporarily reduced cigs). Cooler temps may support a
changeover to snow Mon morning at KDIJ with possible IFR vsbys and
MVFR cigs. MOS and NBM guidance is pretty messy with regard to winds
this afternoon into tonight, and the hourly HRRR guidance is
convectively contaminated by simulated thunderstorm outflows that
may not even materialize, so our forecast confidence in the winds
included in the TAF is pretty low everywhere but KSUN, especially
for direction. Looking ahead to Mon afternoon, slightly better
instability may support a few more thunderstorms, so already
introduced VCTS in the longer KSUN TAF. Winds should be slightly
stronger Mon afternoon, generally out of the SW. - KSmith
&&
.PIH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$