Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/21/23
Area Forecast Discussion
National Weather Service Grand Rapids MI
802 PM EDT Fri Oct 20 2023
LATEST UPDATE...
Aviation
.SHORT TERM...(This evening through Saturday night)
Issued at 304 PM EDT Fri Oct 20 2023
-Dry Night Expected-
Showers are expected to continue to decline this afternoon and
evening as shortwave ridging moves over Lower Michigan, as well as
drier low-level air according to model RH progs. This will keep
conditions dry overnight as well as allow some clearing, mainly in
our southwest forecast area. Overnight lows will fall to around 40.
-Numerous Showers Saturday-
Latest model guidance delays the arrival of the lead shortwave until
near 12z and with that the arrival of any precipitation, so have
trended the early morning Saturday drier as a result. Then expect
scattered to numerous showers on Saturday as the initial weak
shortwave and a following stronger shortwave and associated vorticty
advection provide forcing across the region. Rainfall begins from
northwest to southeast, shifting south as the surface low associated
with these waves moves south. RAP and HREF MUCAPE values are minimal
near I94 and zero over much of the CWA so am expecting just showers
with any thunder threat being to low to mention in the forecast.
Rain moves out Saturday evening as a cold front scours out any
remaining low-level moisture. Total rainfall will be under 0.25
inches with the highest amounts near and southwest of a Grand
Rapids to Lansing line where a bit of FGEN is expected to provide
a bit of a boost to rainfall.
Dry conditions then expected for the rest of Sunday night with some
clearing as high pressure approaches the region, though clouds will
get a lake effect boost, mainly near the lakeshore, as 850 mb temps
fall just below zero in NNW flow.
.LONG TERM...(Sunday through Friday)
Issued at 231 PM EDT Fri Oct 20 2023
High pressure will move over the region Sunday and then quickly move
away Monday. We`ll see quite a bit of sunshine Sunday. However,
clouds and rain will quickly move back in Monday as low pressure
rides northeast from the Plains along a southward sinking frontal
boundary toward Lower Michigan. Isentropic lift ahead of the low
will be the cause of the rain but it won`t last long as it moves
north.
A larger and more prolonged area of rainfall will develop Tuesday
and continue into Friday as the cold front slowly sinks south and
another wave rides northeast along it. MUCAPE increases to 200-400
j/kg during this period so we have some thunder in the grids Tuesday
through Wednesday.
Confidence for rain Thursday and Friday is lower due to quite a bit
of model spread late in the week. The ECMWF builds in ridging
Thursday while the GFS develops a very strong Plains low that then
sweeps another cold front through the cwa late Friday with showers
ahead of it.
Tuesday and Wednesday will be the warmest days with highs in the mid
60s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 758 PM EDT Fri Oct 20 2023
Showers have largely cleared out of Southwest Michigan, so now
we`re just working to clear out some of these low clouds. We`re
expecting improvement in the persistent low ceiling conditions at
nearly all locations overnight as a weak (and temporary) ridge of
high pressure moves into the area. Expecting VFR conditions to
develop by midnight, and the southwest sites of Kalamazoo and
Battle Creek have the best chance of actually clearing out toward
morning. If this happens, we could develop a bit of fog in these
areas for a few hours before the next disturbance moves into the
area by mid morning. As rain showers redevelop between 8 and 11am
at most locations ceilings should once again drop to low VFR or
MVFR as light rain moves back into Lower Michigan.
&&
.MARINE...
Issued at 304 PM EDT Fri Oct 20 2023
The ongoing small craft advisory is verifying well with gusts in the
mid to upper 20 knot range and waves of 4-7 feet being reported at
many of our observation sites. Waves and winds calm overnight
tonight as high pressure quickly moves through the region.
Another small craft advisory will likely be needed Saturday Evening
into Sunday morning as a low-pressure system passing to our
southwest brings additional gusty north winds and elevated waves to
the nearshore zones. Will defer any headlines to later shifts to
avoid confusion with the ongoing advisory. High pressure then moves
into the region during the day on Sunday causing marine conditions
to improve.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Small Craft Advisory until 1 AM EDT Saturday for LMZ844>849.
&&
$$
SHORT TERM...Thomas
LONG TERM...04
AVIATION...AMD
MARINE...Thomas
Area Forecast Discussion
National Weather Service Marquette MI
809 PM EDT Fri Oct 20 2023
.SHORT TERM...(Through Tonight)
Issued at 309 PM EDT FRI OCT 20 2023
Key Messages:
-Rain showers return to the western U.P. overnight.
Water vapor imagery and RAP analysis show a low-amplitude ridge over
the Rockies and a trof over the Great Lakes region into the SE
States, resulting in nw flow across the Upper Great Lakes. Upstream,
a vigorous wave noted in central Manitoba is producing shra and even
a few tsra in se Manitoba. Closer to home, drier air advecting into
the area has been breaking up low cloudiness over w and central
Upper MI. However, lake effect cloudiness has been increasing across
central Lake Superior and the Keweenaw due to 850mb thermal trof of
-3C nosing s across that area. To the e, last of the lingering -shra
associated with the system from yesterday and last night ended
recently. Current temps are mostly in the mid/upper 40s F, but lwr
50s are noted over the s central.
Under nnw flow, 850mb thermal trof nosing s across central and
eastern Lake Superior for the rest of the aftn should result in
expansion of lake effect stratocu going into the evening hrs where
clouds have scattered out across central Upper MI. To the w and
possibly s central, there will be a window this evening where there
will be mostly clear skies with winds falling off to calm as sfc
high pres ridge arrives. As a result, nudged min temps down to
around 30F. However, temps could easily fall into the mid 20s F if
clouds spreading se from Manitoba wave are delayed. Speaking of that
wave, it will track se reaching ne MN around 12z Sat. In response, a
good push of waa/isentropic ascent per 295k sfc spreads sse into
western Upper MI overnight, resulting in shra development, but the
isentropic ascent weakens dramatically farther e. So, this fcst
issuance has delayed shra development until after midnight far w and
will only carry shra mention as far e as roughly from CMX sse into
Menominee County by daybreak.
.LONG TERM...(Saturday through Friday)
Issued at 251 PM EDT FRI OCT 20 2023
Key Messages:
-System rain ends Saturday over the west and central. North wind
lake-effect rain Saturday into Sunday.
-Some snowflakes possibly mixing in at times Saturday into
Sunday.
-Dry Sunday.
-Cool temps Saturday, but warming to near/above normal Monday.
-Active pattern looks to return early next week.
As the shortwave low begins leaving our area to the southwest
Saturday, expect the system rainfall over the western half of the
U.P. to give way to lake-enhanced/effect rainfall over the north
wind belts by late Saturday afternoon. With the shortwave low
becoming more elongated than what was predicted yesterday, the
system precip may hang around longer into the day Saturday over the
west and south central, possibly not leaving until the afternoon
hours. While the slightly colder air behind the low is enough to
keep lake-effect rain showers going into Sunday, with dry air above
850mb, inversion heights are only going to get to around 3 kft,
meaning that the lake-effect rainfall will be very light/drizzly and
sporadic. It is plausible that rain may mix with some snowflakes at
times Saturday into Sunday over the strongest lake-enhanced/effect
bands, but given the warmth at and near the sfc, nothing should
accumulate. With cloud cover remaining overhead due to the lake-
effect cloud cover, expect highs this weekend to be fairly mild,
being in the low 40s to upper 40s Saturday to the upper 40s to
around 50 Sunday.
Expect the lake-effect rainfall/drizzle to end Sunday as ridging
moves over the area. While the ridging ends the precip, expect lake-
effect clouds to stubbornly hang around in the morning before
becoming mostly sunny by the afternoon. However, if you are a sun-
lover, don`t expect the dry conditions to last all that long, as
shortwave activity starts to pick up again early next week.
For next week, model guidance is honing in on two solutions. The
first is a strong low pressure lifting from the Desert SW into the
Plains and Upper Midwest by the middle of next week. This would
cause a pattern flip and bring a troughing pattern over the Central
U.S. (ridging dominates the eastern U.S. early next week).
Currently, the GFS suite of models has retained this line of
thinking, bringing with it multiple shots of rainfall across our
area, with the low from the Desert SW bringing up to possibly an
inch or more of rainfall in places as it taps into an atmospheric
river from the Gulf of Mexico. The second solution keeps the low
over the Desert SW for the work week. Should this occur, expect the
high pressure over the Southeastern U.S. and low pressure over the
Hudson Bay to rotate multiple shortwaves across our area as mainly
zonal flow aloft dominates. Regardless of the solution, expect
multiple shots of rainfall next week, with above normal temps at the
beginning decreasing each day as colder Canadian air slowly slips
southward with time.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 809 PM EDT FRI OCT 20 2023
MVFR cigs have been slow to clear out of SAW and do not expect a
return to VFR in this TAF period as another disturbance approaches
Upper Michigan. And, the brief period of VFR at IWD and CMX will
end Saturday morning, too, due to that disturbance. Highest precip
chances for this TAF period will be at IWD where there will be
visibility restrictions as well as a period of IFR after daybreak
Saturday. Northerly winds have weakened and will remain that way
for this TAF period.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 251 PM EDT FRI OCT 20 2023
As a low pressure over Georgian Bay leaves to southern Ontario the
rest of this afternoon into this evening, expect the northerly winds
of 20 to 25 kts over the eastern lake to die down to 20 kts or less
before midnight tonight. However, a low pressure currently over
Manitoba quickly races down to the Wisconsin border by Saturday
morning. As this second low continues southeastward towards the Mid-
Atlantic, expect northerly winds of 20 to 25 kts to return over the
eastern lake late Saturday afternoon. However, with ridging coming
swiftly behind it, expect the winds to become 20 kts or less again
by Saturday night. Expect the light winds to remain until Monday,
when a shortwave brings south to southwesterly winds of 20 to 25 kts
back across Lake Superior. Additional shortwaves during the middle
and latter part of next week could also bring higher winds to the
lake, but there is currently too much model spread to know if and
when these higher winds arrive.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...Rolfson
LONG TERM...TAP
AVIATION...TDUD
MARINE...TAP
Area Forecast Discussion
National Weather Service Blacksburg VA
1016 PM EDT Fri Oct 20 2023
.SYNOPSIS...
Clouds and showers continue for the mountains through the
weekend. Gusty wind and cool conditions will develop in the
wake of the cold front tonight through Sunday. A strong area of
high pressure will develop over the area next week, allowing
temperatures to moderate and for dry weather.
&&
.NEAR TERM /THROUGH SATURDAY/...
As of 1015 PM EDT Friday...
Key Messages:
1. Showers in the mountains overnight.
2. Gusty winds tonight into Saturday morning.
Minor changes to probability of precipitation in the mountains
tonight based on latest radar trends and HRRR guidance.
No adjustment needed to overnight lows or wind.
Previous Discussions:
As of 800 PM EDT Friday...
Forecast remains on track. Temperatures and dewpoints only
required minor changes, mainly a slight increase in temperatures
overnight because of wind and cloud cover with a slight decrease
in dewpoints later in the night. Main concern overnight will be
wind. Models suggest the strongest winds will be in the 09Z-14Z
time frame, which is common with a northwest flow pattern and
timing of frontal system and increased cold advection. NBM model
trends for pops looked good, with upslope showers persisting
much of the night and morning in the west and frontal associated
showers ending in the east during the next couple of hours.
Discussed potential for wind advisory with neighboring offices
and decided that it was marginal. While there will be some 40kt
gusts at the higher elevations of the far southwest VA mountains
and the NW NC mountains, the amount of real estate covered with
such wind speeds will be limited. Thus, no Wind Advisory will be
issued at this time.
As of 115 PM EDT Friday...
A cold front in the mountains this afternoon will travel east
into tonight. Scattered showers and a few thunderstorms will
develop ahead and along the front. An upper disturbance in the
southern Ohio River Valley will move southeast Saturday into
saturday night. Upslope clouds and scattered showers with gusty
winds are possible behind the front tonight into Saturday.
QPF amounts between about a third of an inch to around an inch over
the mountains and foothills, and around a third of an inch or less
for the piedmont of VA and NC.
Gusty westerly winds arrive tonight behind the cold front, however
plenty of cloud cover should keep the strongest winds from mixing
down. Still, the mountains and foothills will gust into the 20-30
mph range overnight.
Low temperatures tonight with CAA will range from the upper 30s in
the mountains to mid 40s in the Piedmont. High temperatures Saturday
will vary from the upper 40s in the northwest mountains to the mid
60s in the Piedmont.
Confidence is Moderate in the Near Term Forecast.
&&
.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
As of 1250 PM EDT Friday...
Key Messages:
1: Blustery and cool Saturday night
2: Frost possible in the mountains Monday morning
On the back end of a frontal system moving off the coast, a few
upslope rain showers could persist into the overnight period on
Saturday in southeastern WV. This will taper off and the CWA should
be rain free Sunday morning. Winds will be gusty into Sunday
morning, with the mountains and foothills of NC potentially seeing
gusts around 25-35 MPH.
As things calm down on Monday and a broad surface high takes hold of
most of the eastern CONUS, overnight lows Sunday into Monday morning
will be some of the lowest we`ve seen so far this season. Clear
skies and calming winds make for a recipe that could make for frost
most areas west of the Blue Ridge. Lows will touch the low 30s west,
mid to upper 30s east.
&&
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
As of 1250 PM Friday...
Key Messages:
1: Dry weather with moderating temperatures
A surface high will dominate our weather pattern most of next week.
As it drifts just east of the area southerly flow will pick up over
the second half of the week. Under the high pressure with warm
advection, temperatures will moderate back from the frost lows of
the early week and most should see the thermometer touch 60 to 70
degrees. Winds should be calm and the high will suppress
precipitation activity through Friday.
&&
.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
As of 800 PM EDT Friday...
Synopsis: Strong cold front moving east of the region this
evening. Upslope conditions developing in earnest across the
West Virginia mountains with scattered to numerous upslope rain
showers developing. Temperatures too warm for snow this event.
Strong and gusty northwest winds will develop overnight peaking
in the 09Z-16Z time frame, then diminishing Saturday afternoon
and evening. Another short wave will enhance wind across
primarily the northern part of the CWA and mountains for Sunday.
Upslope precipitation will diminish by Saturday afternoon.
Ceilings...Look for ceilings to become mainly VFR east of the
Blue Ridge with MVFR ceilings prevailing along and west of the
Blue Ridge with primarily IFR ceilings across southeast West
Virginia and the highest elevations of southwest Virginia and
northwest North Carolina until around 14Z Saturday. Ceilings
will trend to VFR all areas by late Saturday.
Visibilities...mostly VFR except in scattered light rain showers
in the upslope areas of the west.
Winds...main concern this TAF valid period. West to northwest
sustained 10-20 kts with gusts 25-30 kts. Isolated gusts,
mainly at the higher elevations of the NW NC and SW VA mountains
to 40kts. Strongest winds overnight/early Saturday 09Z-14Z and
across the southwest part of the CWA (i.e., NW NC and SW VA
mountains). Winds will diminish toward 00Z Sunday.
/Confidence Levels in Forecast Parameters/
- Moderate confidence in Ceilings,
- Moderate to High Confidence in Visibilities,
- Moderate to High Confidence in Wind Speed,
- High Confidence in Wind Direction.
EXTENDED AVIATION OUTLOOK...
Another strong short wave will sweep through the region Saturday
night and Sunday. Moisture will be limited, but some rain
showers will be possible mainly along and north of the I-64
corridor and in the mountains of SW VA and eastern WV. Gusty
winds are expected once again, more so in the northern parts of
the mountains with this next short wave. High pressure will
build over the area early next week and remain in place
throughout much of the week providing mostly VFR conditions and
much lighter winds.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...AMS/KK/SH
NEAR TERM...AMS/KK/RAB
SHORT TERM...VFJ
LONG TERM...VFJ
AVIATION...RAB