Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/29/19
Area Forecast Discussion
National Weather Service Bismarck ND
1044 PM CDT Sat Sep 28 2019
.UPDATE...
Issued at 1042 PM CDT Sat Sep 28 2019
As discussed below, will allow the wind advisory to expire with
obs below criteria.
UPDATE Issued at 1015 PM CDT Sat Sep 28 2019
Will be letting the wind advisory southwest expire within the
hour. Observations in southwest ND have been below adv level
criteria now for a few hours, and expect the winds to continue to
slowly wind down as we move into the early morning as the mixing
layer shrinks under mid level warm air advection taking place now.
Will add thunder to the forecast southwest. Embedded thunderstorms
moving into that area from southeast MT/northwest SD. SREF hinted
at this earlier and now it has become reality. Will also throw a
mention in for the overnight south as mid level instability
increases northward with the WAA.
UPDATE Issued at 824 PM CDT Sat Sep 28 2019
Forecast remains on track for tonight. Updated POPs to better
reflect latest radar imagery across the area.
UPDATE
Issued at 549 PM CDT Sat Sep 28 2019
Will hoist a wind advisory for far southwest ND this evening.
Winds have already gusted to 41 mph at both Bowman and Hettinger
as gradient forcing increases across the region. The high winds
should remain confined to the higher terrain of far southwestern
ND. Otherwise, tweaked POPs based on latest radar and near term
trends for this update.
&&
.SHORT TERM...(This evening through Sunday)
Issued at 200 PM CDT Sat Sep 28 2019
Widespread light to moderate rain will overspread western and
central North Dakota this evening and continue through Sunday. A
few strong thunderstorms are also possible on Sunday to the south.
Observed 12z upper air analysis depicts a large upper level low
centered over the northwest United States, with low amplitude
ridging downstream and a few shortwaves embedded within southwest
flow across the Dakotas. This puts the Northern Plains region in
an area of strong PVA and weak WAA, contributing to synoptic
scale forcing for ascent. At the surface, a low pressure system is
beginning to develop over northeast Wyoming. This low will
continue to deepen as it progresses northeastward across the
Dakotas. Widespread light to moderate rain will be accompanied
with this low, which has already begun spreading into southwestern
North Dakota early this afternoon. The latest suite of model
guidance agrees well on the timing and coverage of this area of
rain, which will continue spreading across North Dakota this
evening through tonight. Ridging across the Great Lakes region
will contribute to the slow movement of this surface low on
Sunday, leading to another stormy day.
In fact, some thunderstorms will be possible Sunday afternoon
through Sunday night across southern North Dakota as a well
defined warm sector forms across the Dakotas. The 12z GFS/EURO
both agree well on 500 to 1000 J/kg of MUCAPE across southern
North Dakota during this time, collocated with 50 to 65 kts of
effective bulk shear. In addition, a surface cold front will also
be present. With that being said, shear vectors will be oriented
nearly parallel to the front, which would suggest a congealed
multicellular storm mode after a few initially discrete storms.
Forecast soundings depict an environment that would require
thunderstorms to be elevated in nature, which should somewhat
limit the threat for damaging wind gusts. Nevertheless, large hail
up to the size of half dollars may be possible with any initially
discrete cells that may form. The 12z iteration of the HRRR does
show a few discrete cells Sunday afternoon and evening across
portions of southwest and south central North Dakota. Overall, the
severe weather threat looks rather low given the low CAPE/high
shear environment and the messy storm mode/elevated nature of
these storms. It is unclear if shear will be too high for the
rather limited amount of CAPE that will be present on Sunday.
Heavy rain will also be a concern, as areas that receive the
heaviest rain rates could experience some flooding.
Expect lows in the mid 30s to mid 40s tonight, with highs ranging
from the mid 40s north to the mid 60s south for tomorrow.
.LONG TERM...(Sunday night through Saturday)
Issued at 200 PM CDT Sat Sep 28 2019
The cooler and wetter than normal weather pattern will continue
through the long term forecast.
Saturday and Sunday`s low pressure system will linger over the
area Sunday night, before departing the region on Monday.
Widespread rain is likely across all of western and central North
Dakota Sunday night through Monday morning, with conditions
beginning to dry out Monday afternoon and evening. Excess cloud
cover and precipitation will keep temperatures on the chilly side
for this time of year, with highs mainly in the upper 40s to upper
50s on Monday. A cold front looks to move through the area Monday
night.
It appears clouds will linger behind the cold front on Tuesday,
with limited clearing during the afternoon. These clouds, along
with strong CAA, will lead to high temps only in the mid to upper
40s across western and central North Dakota. Although a few post
frontal showers will be possible, a mainly dry day is expected.
Long term model guidance begins to disagree quite a bit on
Wednesday, with the GFS keeping the area dry and the EURO bringing
in another round of rain. Both models keep the area dry on
Thursday and most of Friday. Although the precipitation forecast
is quite uncertain during this time, there is higher confidence
in temperatures remaining cool. The latest iteration of the NBM
suggests highs in the 40s and 50s Wednesday through Friday. A
widespread freeze looks possible Monday night through Wednesday
night as low temperatures drop into the upper 20s to lower 30s for
most areas.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 549 PM CDT Sat Sep 28 2019
Widespread light to moderate rain showers will spread from west to
east across North Dakota this evening, affecting all TAF sites
throughout most of the 00Z TAF period. Expect mainly IFR to MVFR
cigs with incoming low cloud cover. Easterly winds will also
increase across western and central North Dakota now through this
evening, persisting through the period.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...NH
SHORT TERM...TK
LONG TERM...TK
AVIATION...NH
Area Forecast Discussion
National Weather Service Denver/Boulder CO
858 PM MDT Sat Sep 28 2019
.UPDATE...
Issued at 858 PM MDT Sat Sep 28 2019
Current forecast looks on track. For tonight just needed to
refresh the T/Td and sky grids across the far northeast corner
based on latest GOES-16 trends and mesonet observations. This is
the area that has remained under the stratus deck all day. High
res models are indicating some weak moisture advection from the
ESE into the northeast corner, under the stratus deck, which
combined with the fact that it`s night and autumn, could lead to
some patchy fog. Upstream observations are not showing as much
impact as some models, so overall confidence in significant fog is
low. Some high res models can`t agree on whether fog will even
form. For now, given the tight T/Td spreads now and with any bit
of either cooling or moisture advection, patchy fog is possible so
have kept that in the forecast from 2-6 AM. No other updates
needed given the message of the day on Sunday is hot (for the end
of September), very dry, and windy with the approach of a trough
to our northwest...and the existing forecast has this all well
handled.
High confidence in tomorrow`s critical fire danger given the
latest runs of the HRRR and recent HREF guidance. A combination
of winds gusting over 40 mph across the plains and mountain
valleys, and RH 10-15% should result in critical conditions. For
Monday, the threat remains in the mountains and Palmer Divide, but
shifts away from much of the plains given the fact that winds
should be much weaker there. We are confident red flag conditions
are likely across the mountains and Palmer Divide area Monday, so
will keep the watch intact for those areas.
&&
.SHORT TERM...(This evening through Sunday)
Issued at 232 PM MDT Sat Sep 28 2019
A strong upper low over Oregon continues to deepen and slowly move
east while an upper high remains over the southeastern US. A 100kt
jet will push into northwestern Colorado, with increasing
southwesterly winds aloft over the state. Lift from the jet, weak
instability and a ribbon of moisture will allow for a few showers
or storms to occur over the high terrain this afternoon. The jet
is deepening a surface low in southwestern Wyoming, causing the
moderate to strong southerly surface winds across the plains.
Gusts have been in the 25 to 35 mph range today and will continue
into the evening. Higher moisture over the Great Plains will
likely push in on southeasterly winds, with low stratus or areas
of fog likely sneaking into the far northeastern corner of the
state overnight. Southerly winds will continue to blow across the
plains heading toward lower pressure up in Wyoming. Winds over
the high terrain will keep blowing overnight as well as the jet
moves closer.
The jet will strengthen over northwestern CO Sunday and the
surface low will push out into eastern Wyoming and western
Nebraska causing the surface winds to become more downsloping
southwesterly. Warm and dry conditions will bring critical fire
weather conditions, see the discussion below. A few showers may be
possible over the northern mountains but little if any
precipitation will likely fall.
.LONG TERM...(Sunday night through Saturday)
Issued at 306 PM MDT Sat Sep 28 2019
Models have very strong southwesterly flow over the CWA Sunday
night through Tuesday night. The speeds are 100 to 125 knots at
jet level all five periods. At the low levels, a cold front and
upslope is progged into the CWA sometime Monday afternoon. Models
keep upslope in place Monday night through Tuesday night well into
Wednesday. The QG Omega fields keep the CWA in upward synoptic
scale energy Sunday night through Tuesday night. For moisture,
there is not much around Sunday night and Monday. Models show
low level moisture over the plains Monday night through Tuesday
night. It is very stable over the plains after the upslope moves
in. The QPF fields do indicate some minor amounts of measurable
rainfall over the plains Monday night and Tuesday; certainly
stratiform in nature if at all. For temperatures, Monday`s highs
are 2-4 C cooler than Sunday`s. Tuesday`s highs cool down 10-20 C
over the plains and lower foothills. For the later days, Wednesday
through Saturday, models show the upper trough over western North
America to finally push east and move across Colorado on
Wednesday. There is upper ridging progged on Thursday. Friday has
southwesterly flow aloft on most of the models, then an upper
trough is progged to move east across the CWA sometime on Saturday
with the models not quite in sync with the feature as far as
timing goes.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 858 PM MDT Sat Sep 28 2019
VFR expected through Sunday. Main concern will be strong and
gusty winds Sunday afternoon. Expect southerly winds at APA and
DEN to continue into the mid morning hours. Light WNW at BJC. By
late morning, mixing and an ejected low pressure system across
Wyoming will cause southwest winds to ramp up significantly. By
mid afternoon we expect southwest winds 20-30 kts with gusts
approaching 40 kts at APA and DEN. Winds are probably going to be
just as strong at BJC. After about 8 PM or so winds will return to
typical values, S to SSW at 8-12 kts at all three metro area
terminals. No chance of precipitation through Sunday.
&&
.FIRE WEATHER...
Issued at 306 PM MDT Sat Sep 28 2019
Critical fire weather conditions will develop right around noon
Sunday across portions of the higher terrain, Palmer Divide and
east central plains due to low humidity and gusty southwest winds.
Humidity will likely be in the 12 to 18 percent range in the
warning areas. Even though criteria needs to be at or below 15
percent, the winds will be strong enough (gusts of 35 to 45 mph)
that the concern will still be there. It will likely remain
breezy overnight but humidity should increase after sunset to
lessen concern.
Another day of critical fire danger may occur again on Monday
across portions of the higher terrain, Palmer Divide and eastern
plains. Gusty southwest winds are expected. Humidities do look a
bit higher on Monday then were progged previously but they a
still pretty low over the southern half of the CWA.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from noon to 7 PM MDT Sunday for COZ212>214-216-
239>241-243>247-249.
Fire Weather Watch from Monday afternoon through Monday evening
for COZ212>214-216-241-245>247-249.
&&
$$
UPDATE...Schlatter
SHORT TERM.....Kriederman
LONG TERM......Koopmeiners
AVIATION...Schlatter
FIRE WEATHER...Kriederman/Koopmeiners
Area Forecast Discussion
National Weather Service Grand Rapids MI
1203 AM EDT Sun Sep 29 2019
LATEST UPDATE...
Aviation
.SYNOPSIS...
Issued at 250 PM EDT Sat Sep 28 2019
- More rain for Sunday
- Summer encore Monday and Tuesday
- Fall returns by mid-week
&&
.UPDATE...
Issued at 1038 PM EDT Sat Sep 28 2019
Overall our on-going forecast is on track. The upstream convective
complex is already spreading an extensive mid and high level cloud
shield our way. This will help keep temperatures from getting
cold enough for a frost advisory for the most part. It would not
be out of the question for Leota to get near freezing tonight even
so. Still overall most area should stay warmer then the mid 30s
in Clair County, which likely will have the coldest lows tonight.
Meanwhile the question remains about the precipitation on Sunday.
As it typically the case, the hi res models have numerous
solutions. The NAMNEST has heavy rain (1"-2" in 6 hours) over the
I-94 area Sunday with a second branch of 1" to 1 1/2" from Grand
Haven to Sparta toward Mount Pleasant. The HRRR seems to like
most of the rain in that later area (Grand Haven to Mount
Pleasant). The moisture transport vectors in the 1000/850 layer
are not nearly like they were yesterday and precipitable waters
due not rise as high either. The instability is elevated but
limited at best. At 10 am the RAP, NAM and GFS have a nearly
saturated sounding over AZO from near 850 mb to 300 mb. The GFS
and NAM are saturated from near the surface to 300 mb. So my guess
it we will see showers, an isolated thunderstorm is not out of
the question. Most locations should see some rain Sunday. Will we
see locations with more than an inch in 12 hours? It is possible,
but it does not at this point look likely.
&&
.DISCUSSION...(This evening through next Saturday)
Issued at 250 PM EDT Sat Sep 28 2019
Fairly active weather pattern continues through mid week as a wavy
front meanders across the central Great Lakes region with periodic
chances for rain and thunder, mostly for Sunday and again Tuesday
night and Wednesday.
For tonight, the front is south of the forecast area but clouds
will hang tough across the southern zones closer to the front. At
least partial clearing across the north will make for a big
temperature gradient from the upper 50s across the south to the
lower 40s across the north. Some showers could creep into the far
south by daybreak.
On Sunday and into Sunday night, showers and thunderstorms spread
north as warm front lifts in advance of sfc low tracking west of
the Great Lakes. Rain chances continue into Monday morning but
upper ridging should build in by the afternoon putting an end to
the rain until later Tuesday when the front returns south into the
juicy airmass. Max temps on Monday and Tuesday should be in the
low to mid 80s across the south and a bit lower across the north
where clouds and a few showers could linger.
Heavy rain potential on Tuesday night and Wednesday will have to
be watched as front moves into juicy airmass. Model trend is for a
quicker southward movement of the front as the upper ridge is
flattened and eventually replaced by troughing at the end of the
week. High temperatures Thursday and Friday are forecast to be 20
to 25 degrees lower than Monday and Tuesday. Clouds and showers
may linger into Thursday.
At least scattered frost is possible by Thursday night if the
Canadian sfc high builds in as strongly as suggested by some
model guidance, and more likely Friday night as model consensus is
for drying and clearing with the sfc high over the central Great
Lakes.
&&
.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1202 AM EDT Sun Sep 29 2019
Broken clouds at or just below 5000 feet will stream in from the
southwest with widely scattered showers during the early morning
hours. A more coherent area of showers will move in from the
southwest after sunrise and persist for much of the daylight
hours. An embedded thunderstorm is possible but coverage is
expected to be isolated enough to prevent mention in any TAFs at
this time. Ceilings and visibilities will fall as the day
progresses, bottoming out to IFR category (700 ft and 2-3 miles,
respectively) and persisting through much of the rest of the TAF
period. Conditions may improve at AZO/BTL/JXN during the last hour
or two of the TAF period but will not advertise as such in the
outgoing package. Easterly winds will prevail through the majority
of the TAF period, with a few gusts toward 20 kts during the
afternoon hours.
Confidence is high in the occurrence of IFR cigs, medium in IFR
visibilities, and medium on timing.
&&
.MARINE...
Issued at 818 PM EDT Sat Sep 28 2019
Winds and waves have fallen below small craft criteria early this
evening and are not expected to exceed criteria again until Sunday
night at the earliest. So, I expunged the small craft advisory
that was in effect for our northern two marine zones.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&
$$
UPDATE...WDM
SYNOPSIS...Ostuno
DISCUSSION...Ostuno
AVIATION...Borchardt
MARINE...WDM
Area Forecast Discussion
National Weather Service Newport/Morehead City NC
951 PM EDT Sat Sep 28 2019
.SYNOPSIS...
A weak cold front will push through tomorrow followed by high
pressure from the north early to mid week. A strong cold front
will move through by the end of the week.
&&
.NEAR TERM /THROUGH SUNDAY/...
As of 950 PM Saturday...00Z MHX sounding showing a pronounced
dry layer below 850 mb this evening, relatively in line with
HRRR soundings. HRRR in turn shows the potential for possibly
very patchy shallow fog early Sunday morning and still think the
overall fog potential precludes mention in the grids. No changes
for this update.
Prev disc...Upper ridging continues over the area tonight with
weak high centered offshore. Mainly clear skies will prevail
with light winds. A warm and muggy airmass will persist across
the area with lows around 70 inland to mid 70s coast. While the
airmass at the surface has changed little, model soundings show
a bit of drying in the lower levels just above the surface
compared to last night and guidance is not developing much fog
tonight, so continue to keep fog out of the forecast.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH 6 PM SUNDAY/...
As of 245 PM Saturday...A backdoor cold front is progged to be
positioned near Hampton Roads in the morning and push across ENC
late morning through the afternoon hours. Ridging will continue
aloft, so upper level forcing will be weak but descent moisture
and instability will be in place with PW values approaching 2"
and MUCAPE peaking around 2500-3000J/kg and could see isolated
to scattered showers and thunderstorm during the afternoon with
frontal forcing. Shear also remains weak, mainly 10 kt or less,
so not expecting storms to become organized or even that strong.
Temps continue to be well above normal with highs in the lower
90s inland to mid 80s coast. NE sections may be a tad cooler
with winds becoming N/NE by the afternoon behind the front
bringing onshore flow.
&&
.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
As of 340 PM Saturday... Strong deep layered ridging will
extend across the Southeast states through Thursday resulting in
mostly dry and warm weather, though there is a small risk for
showers early Sunday evening and again Monday, though any
precipitation amounts would be very light and not enough to make
a dent in our very dry spell. The strong ridge aloft will start
to break down as a strong mid level trough allows a strong cold
front to move across the area Fri night bringing a chance for
showers and thunderstorms late Fri into Fri night. Highs will be
in the upper 80s to around 90 degrees Wed and Thurs, while Mon,
Tue, and Fri will be in the low/mid 80s which is still above
normal. Much cooler is expected behind the front next weekend
behind the front.
&&
.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
Short Term /through Sunday/...
As of 730 PM Saturday...High confidence in VFR conditions for
the night well into Sunday evening. Upper level ridge continues
aloft with high pressure shifting offshore and a backdoor cold
front sliding through the region late Sunday morning. Mainly
clear skies expected tonight with some high cirrus tonight
expected to gradually dissipate. Some very shallow patchy fog is
possible tonight although guidance is bearish on this prospect;
confidence in fog formation is too low to warrant explicit
mention in the TAFs.
Light and variable winds tonight give way to NW/N winds Sunday
morning, eventually veering NE/ENE by Sunday evening in the wake
of the front. An isolated shower or storm is possible in the
afternoon with brief sub-VFR conditions for any directly
impacted sites.
Long Term /Sunday night through Thursday/...
As of 340 PM Saturday...VFR conditions will dominate most of
the period, except Monday. There is only a very small risk for a
brief shower Sunday evening and Mon. Low stratus is likely to
develop Mon as high pressure builds in from the north.
Otherwise, could see patchy shallow ground fog or stratus
during the early morning hours each day with light to calm winds
through the rest of the week.
&&
.MARINE...
Short Term /through Sunday/...
As of 3 PM Saturday...High pressure will be centered offshore
tonight, then a backdoor cold front will push south across the
waters Sunday. Generally light winds around 10 kt or less will
continue ahead of the front, mainly out of the S to SW this
evening, then veering to W to NW late tonight into Sunday
morning, then will become N to NE around 15 kt Sunday afternoon
behind the front. Seas will continue around 2-3 ft through
Sunday morning, then will build to around 4 ft across the
northern/central waters late in the day. Leading swells from
Hurricane Lorenzo will begin to move into the waters late
tonight bringing 17-18 second swell periods.
Long Term /Sunday night through Thursday/...
As of 340 PM Saturday...SCA conditions, mainly in swell from
Tropical Cyclone Lorenzo well out in the Atlantic, is expected
Mon through Wed night. NE flow will be increasing to 15-20 kt
with higher gusts behind the back door cold front late Sun
night into Mon evening. Tue NE winds will diminish to 10-15 kt
becoming L/V early Wed and S/SW 10-15 kt Thu. Seas will build to
AOA 6 ft by early Mon, peaking at 6-8 ft Mon/Mon night when
combined with the easterly Lorenzo swell will create chaotic sea
conditions. Though winds will diminish to 15 kt or less Tue
through Thu, seas are forecast to remain AOA 6 ft Tue through
Wed night. Seas are forecast to slightly subside to 3-5 ft Thu.
&&
.MHX WATCHES/WARNINGS/ADVISORIES...
NC...Beach Hazards Statement from 8 AM EDT Sunday through Sunday
evening for NCZ203-205.
MARINE...None.
&&
$$
SYNOPSIS...MHX
NEAR TERM...SK/MS
SHORT TERM...SK
LONG TERM...JME
AVIATION...JME/MS
MARINE...JME/SK
Area Forecast Discussion
National Weather Service Omaha/Valley NE
631 PM CDT Sat Sep 28 2019
.SHORT TERM...(Tonight through Tuesday)
Issued at 330 PM CDT Sat Sep 28 2019
Shower and thunderstorm chances tonight, a conditional risk for
severe storms Sunday into Monday, then potentially heavy rains
beginning Tuesday, are the primary forecast concerns.
Pronounced mid level shortwave moving through the High Plains of
Kansas early this afternoon was enhancing theta-e advection from
central Kansas into southeast Nebraska where scattered showers and
thunderstorms were noted. Only modest instability was shown on RAP
analysis with MUCAPE between 500-1000 J/kg along the KS/NE border.
This convection is scheduled to overspread most of the southern half
of our CWA during the afternoon, but begin to wane from southwest to
northeast as upper wave ejects through the region. A secondary
shortwave moving into the region later tonight will enhance low level
jet over warm front lifting into northern Kansas, increasing
instability across eastern Nebraska. Thus we should see convection
breaking out late tonight in our south, with that area spreading
north through Sunday morning as warm front travels through the CWA.
Front should be north of our are late in the day with majority of
convection occurring north of the boundary. However increase in low
level moisture with surface dew points in the lower 70s will
contribute to 1500-2000 J/kg of MLCAPE across much of our CWA in
warm sector south of warm front. Bulk shear in the 40-50kt range
combined with instability suggests if storms do develop, organized
convection is likely with all modes of severe possible. However warm
mid level temperatures and lack of low level focus for development
will likely inhibit initiation, and if initiation occurs, will limit
coverage. The most likely area for storms to fire will be northeast
Nebraska where instability, shear and weak low level convergence
will reside.
By Monday a cold front will begin settling into northeast Nebraska
in the wake of mid level trough riding through the Northern Plains.
Low level moisture, instability and shear will still be favorable
for severe storms in convergence zone along front, however
inhibition will still have to be overcome for storms to fire
before 00Z. We are more likely to see storms Monday night when low
level jet enhances lift over frontal zone. Severe risk appears to
be marginal at this time as forecast soundings show elevated
instability waning after dark.
Cold front makes only slow progress to the southeast on Tuesday as a
continuous feed of moisture overspreads eastern Nebraska and
southwest Iowa. Precipitable water is forecast to approach 2
inches, which is about 250 percent of normal. Training of storms
along the slow moving cold front in an efficient rain-producing
environment suggest several inches of rain are possible across a
large part of our area during the day Tuesday. As things become
more clear in the next day or so, we will likely need flood or
flash flood watches for that time period.
.LONG TERM...(Tuesday night through Saturday)
Issued at 330 PM CDT Sat Sep 28 2019
A continued threat for heavy rain Tuesday night is the primary
concern for the longer term period. Cooler temperatures and sporadic
rain chances to end the week are highlights as well.
Models have begun to nudge Tuesday cold front southward a little
more quickly with their latest runs as compared to 24 hours ago.
However not quickly enough as much of Tuesday night will bring a
chance for heavy rain across the southern half of our CWA. As front
settles south and takes focus for heavy rain south of our CWA on
Wednesday, we will still have a chance for showers through
Wednesday night as upper trough swings through the Northern
Plains. Much cooler air will plunge south for Thursday into Friday
when highs struggle to reach 60 and lows fall back into the 40s.
A quick return to southerly flow as heights build back into the
region for Saturday will be accompanied by another slug of warm
advection shower chances.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 628 PM CDT Sat Sep 28 2019
MVFR conditions are expected to be in place by 00Z. Ceilings will
lower to below 1000 ft AGL leading to IFR conditions. IFR
ceilings will be in place until about 16Z. From 12-16Z, there is a
chance of thunderstorms over eastern Nebraska as warm moist air
continues to surge north. After 16Z, ceilings should lift to MVFR
conditions.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.
&&
$$
SHORT TERM...Dergan
LONG TERM...Dergan
AVIATION...Fajman
Area Forecast Discussion
National Weather Service Blacksburg VA
821 PM EDT Sat Sep 28 2019
.SYNOPSIS...
High pressure offshore will continue to weaken as a weak cold
front approaches from the north tonight into Sunday. This front
should backdoor through the region later Sunday into Sunday
night before sliding into the Carolinas by Monday. Cooler high
pressure will then wedge south along the eastern slopes of the
Appalachians for early next week.
&&
.NEAR TERM /THROUGH SUNDAY/...
As of 800 PM EDT Saturday...
Convection has ended across the forecast area except for some
isolated lingering showers across southeastern WV. This
activity, per all of the HIRES CAM models, is expected to
dissipate before midnight. Overnight hours will bring fair
weather conditions to the entire area with late night/early
morning fog developing. The fog should be a bit more widespread
in recent days thanks to the showers/thunderstorms that left
moist ground in some areas Saturday. Thus, there could be some
areas that see dense fog overnight that may need to be addressed
with an SPS or DFA, but at this time it does not appear that the
fog will be widespread. Temperatures and dewpoints were pretty
much on track, except at some isolated locations where late day
showers/thunderstorms left the temperature cooler than expected.
These cooler pockets will even out overnight.
Sunday will be a very warm and humid day for the end of
September. It will definitely feel more like August! Convection
appears unlikely Sunday at this point due to a much more stable
atmosphere and northeasterly dry low-level flow.
As of 310 PM EDT Saturday...
Clusters of deep convection continue to propagate over and east of
the Blue Ridge late this afternoon within an area of high
instability and decent moisture convergence. Expect some of this
coverage to gradually shift east but likely weaken upon entering the
piedmont where more in the way of weak downsloping and to the east
of the better support. However will maintain high chance to low
likely pops Blue Ridge for a while longer with chance coverage to
the east and west of the main convective corridor.
Short term guidance then quickly weakens showers/storms with loss of
heating as instability wanes and the axis of convergence slides
east. This should act to shut down pops this evening in all except
perhaps the far west where will still have some weak westerly
upslope flow ongoing. Thus left in some low end pops over the
southwest before cutting to more clearing and patchy fog/stratus
overnight espcly where earlier heavy rain occurred. Lows mostly in
the 60s given moist dewpoints in place.
Mid level ridging strengthens again on Sunday in advance of the
surface based backdoor cold front that looks to drop toward the area
by late in the day. However with the column drier and instability
less under west/northwest flow, appears convection more isolated at
best, and mainly confined to along the ridges espcly northwest near
the front, and along the southern Blue Ridge per differential
heating. Thus only carrying low chance pops in these spots with a
ribbon of more isolated coverage elsewhere along the mountains and
little out east. Otrw will be another very hot/humid day under weak
compression and warming aloft that may again shoot highs up to around
90 or higher southeast and well into the 80s elsewhere at this
point.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
As of 330 PM EDT Saturday...
During this portion of the forecast, the upper ridge that has been
centered over the Florida Panhandle, will pivot northwest into the
mid-Mississippi Valley. This transition will open the door for the
potential for some upstream shortwave troughs across the Great Lakes
and Ohio Valley to potentially skirt northern and eastern parts of
the region. Also, guidance has been persistent on a backdoor cold
front making its way south of the area on Monday. The result
will be daily chances of isolated to scattered showers,
especially in areas along and near the crest of the Blue Ridge,
and potentially some isolated thunderstorms. Temperatures on
Monday will be some of the coolest we have had for a while, but
still be above normal -- about five to ten degrees above normal.
The backdoor front and its associated lee side high pressure
wedge dissipate by Tuesday, with temperatures increasing a bit
again, and precipitation chances limited to isolated coverage
across mainly the Northern Mountains of North Carolina.
Confidence in this portion of the forecast is moderate to high.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 345 PM EDT Saturday...
For Wednesday through Saturday, the general synoptic pattern across
much of CONUS morphs such that more amplified and deeper trough
progress eastward along the U.S./Canadian border, the flow across
our region becoming more zonal, and the upper ridge that has been
over much of the eastern U.S. becoming narrow, latitudinal, and
confined to near the Gulf of Mexico. Where models deviate on this
transition is the timing of a substantial longer wave trough that
moves into the northeast U.S. While the GFS and European solutions
are comparable with a Friday/Saturday timing for the feature
crossing our region, the Canadian solution holds on to remnants of
the upper ridge longer with more of a Sunday/Monday timing for the
trough and its associated potent cold front.
Our forecast will reflect a persistence forecast that leans more
towards the quicker GFS/European solution.
Temperatures during the first half of this portion of the forecast
are expected to be around fifteen degrees above normal. By the
second half of this portion of the forecast readings are expected to
be more on the order of five degrees above normal on Friday and
around normal to perhaps a couple of degrees below normal on
Saturday.
Confidence in this portion of the forecast is low to moderate with
the biggest question mark being the timing of the expected upper
level long wave trough and associated potent cold front.
&&
.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
As of 800 PM EDT Saturday...
Improving aviation conditions expected this evening as nearly
all of the convection has dissipated. All of the HIRES CAM
models suggest that any additional convection will remain
confined to the western mountains and likely dissipate
completely before midnight. Cirrus debris, scattered low/mid
clouds will be all that remain across the region over the next
few hours with mostly VFR ceilings through 06Z. After 06Z, would
expect patchy dense fog to begin to develop, especially in areas
that saw rain Saturday afternoon, as well as the usual spots,
such as LWB, BCB, LYH. In these areas, IFR-LIFR
ceilings/visibilities will be possible. Given that the air is
cooler and rain was scattered around the region, plus winds will
mostly be calm overnight, fog development seems likely.
However, the HIRES HRRR surface visibility is not excited about
widespread IFR or worse ceilings overnight.
Surface high pressure will begin to move toward the New England
coast as the weak front stalls to our south, very similar to the
scenario of last week`s backdoor front. This will allow the
surface winds to come around to the northeast east of the Blue
Ridge and east-southeast west of the Blue Ridge at speeds of 5-8
mph. Convection is unlikely Sunday as the air mass will be much
more stable in the pseudo-wedge and northeasterly flow. Thus,
expecting mainly VFR conditions after the morning fog/low clouds
burn off.
/Confidence in Forecast Parameters/
Ceilings - Moderate,
Visibilities - Moderate,
Winds - Moderate to High,
Thunderstorm Threat - Low.
.Extended Aviation Discussion...
High pressure aloft will build across the region into the middle
of next week, promoting mainly dry VFR conditions. There will
be the normal early morning fog/stratus in the mountain
valleys...mainly confided to the 4AM-9AM time frame. A strong
cold front will bring a chance of showers and much cooler
temperatures by the end of the week. A brief period of at least
sub-VFR conditions appears likely to accompany the front.
&&
.CLIMATE...
Records for Sunday 09/29/2019
Site MaxT Year
KBLF 92 1953
KDAN 92 1998
KLYH 90 1953
KROA 93 1953
KRNK 91 1953
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...JH
NEAR TERM...JH/RAB
SHORT TERM...DS
LONG TERM...DS
AVIATION...JH/PM/RAB
CLIMATE...RCS
Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
802 PM EDT Sat Sep 28 2019
.UPDATE...
Latest RAP model has mid level ridging centered over the southern
MS/AL line dominating the Gulf region over night while high
pressure south of the Canadian Maritimes stretches across the
southeast U.S. coast to the Gulf of Mexico...with a slowly
tightening gradient.
Model PWAT values and ascending TBW sounding indicate a generally
dry airmass in place. Although with enough moisture to support a
few lower clouds and isolated light showers that streamed in from
the east earlier this afternoon...these showers will be ending
with the loss of daytime heating. The afternoon sea breeze was
limited and is now giving way to a northeast or east surge
sweeping in from the east coast with some robust winds. These
winds diminish by midnight but pick up again late Sun morning and
afternoon.
&&
.AVIATION...
29/00Z Issuance. VFR with FEW-SCT CU/SC along with low ST PSBL
08Z-15Z. Afternoon sea breeze has just about collapsed...giving
way to a robust NE or E surge TIL 03Z. NE winds through the rest
of the period...strong enough to preclude any afternoon sea
breezes impacting the main terminals and also resulting in some
gusts AFT 17Z.
&&
.MARINE...
High pressure along the eastern seaboard into the Gulf of Mexico
will slowly strengthen during the next few days with east and
northeast winds...robust at times especially in evening surges
when caution to advisory conditions may be possible. This high
pressure will begin to relax later in the week and allow winds and
seas to to diminish.
&&
.Preliminary Point Temps/PoPs...
TPA 73 90 75 90 / 0 0 0 20
FMY 74 91 73 91 / 0 10 0 20
GIF 72 92 73 91 / 0 20 0 20
SRQ 75 91 75 90 / 0 0 0 20
BKV 71 91 71 92 / 0 0 0 20
SPG 75 89 76 90 / 0 0 0 20
&&
.TBW WATCHES/WARNINGS/ADVISORIES...
FL...None.
Gulf waters...None.
&&
$$
UPDATE/AVIATION/MARINE...09/Rude
UPPER AIR...97/Flannery
DECISION SUPPORT...Jillson