Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/28/20
Area Forecast Discussion
National Weather Service Burlington VT
1033 PM EDT Sun Sep 27 2020
Mild to warm weather continues through Tuesday under strong
western Atlantic high pressure. A few very light showers or
sprinkles will be possible later tonight into Monday as Atlantic
moisture streams northward, though amounts will be light to
negligible. Sorely needed rainfall finally arrives by Tuesday
into Wednesday as a cold front pushes across the region. Behind
this front, a trend toward cooler weather is expected for the
back end of the work week.
.NEAR TERM /THROUGH MONDAY NIGHT/...
As of 1029 PM EDT Sunday...Just some small adjustments to the
temperatures and dewpoints for the next few hours as cloud
cover has slowed temps from falling in the Champlain Valley,
while lack of clouds have sped up falling temps in the northern
St Lawrence Valley. Have also allowed SPS for fire weather
concerns to expire along with ending the lake wind advisory for
Lake Champlain. Previous forecast follows.
Another nice early fall day has unfolded across the area under
breezy south winds and variable mid to high level clouds.
Temperatures have climbed to near forecasted values from the mid
70s to around 80. Some smoke aloft has also been evident, and
captured nicely by latest runs of NOAA`s HRRR integrated smoke
For tonight a broad increase in cloud cover is expected once
again as weak low pressure off the Delmarva coast and an
associated push of Atlantic moisture are advected northward into
New England. Will maintain slight to lower end chances of a few
light showers or sprinkles (20-40%) across mainly the higher
terrain and portions of southern/eastern VT later tonight into
tomorrow morning per model consensus. However, with a broad lack
of dynamical forcing I`ve undercut MOS values by about 50%
accordingly and cut back on model blended QPF. Any measurable
amounts that do occur will be very negligible and on the order
of a few hundredths at best. Low temperatures to remain quite
mild by late September standards - mainly in the 60s to locally
near 70 at KBTV.
Any morning sprinkles end and cloud cover gradually trends
partly sunny tomorrow as mean synoptic upper flow continues to
amplify in response to a fairly deep meridional trough digging
southward through the Great Lakes and Mississippi Valley.
Temperatures to warm quite nicely once again, topping out in the
70s to around 80 or so in the broader valleys. Mild weather
then continues into Monday night under variable cloud cover.
Rainfall chances begin to increase late across far western
counties as aforementioned upper trough and associated surface
front begin to approach.
.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
As of 400 PM EDT Sunday...Chance for rain showers will increase
from west to east across our area on Tuesday as cold front
pushes across the north country. Think that most areas will have
measurable precipitation with plenty of deep moisture across
the area. Temperatures will warm into the upper 60s to lower
70s, coolest west where the precipitation arrives the soonest.
This front will be slow to cross the area, and showers will
continue into the overnight hours Tuesday night into early
Wednesday morning. During the second half of the overnight, a
second wave of low pressure will approach from the south, riding
along nearly stationary cold front which is situated across our
area. Overnight min lows will remain mild across Vermont where
showers continue, and a bit cooler across Northern New York
where we`ll start to see some breaks in the clouds as the precip
ends. Lows will be in the 50s across VT and 40s in NY.
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
As of 400 PM EDT Sunday...Active weather will continue into the
long term portion of the forecast as large upper level trough
remains anchored over the eastern conus and will continue to be
focus for shortwaves crossing the area and increased chances for
precipitation. Still pretty good shot at showers Wednesday
morning with low pressure system lifting out of our area,
showers ending towards the afternoon hours. Several of the
longer range models show yet another low pressure system lifting
across Southern New England on Thursday, though looks like
we`ll more on the fringe with this circulation but will still
have increase in pops for eastern Vermont. From Tuesday through
Thursday rainfall totals will range from around an inch in
Northern New York, to about two and a half inches in eastern
Vermont. Since the rain will fall over a period of three days,
do not anticipate any issues with this much rainfall as our
region has been very dry. The weather will remain showery
through the weekend though as upper trough takes a long time to
make it east of our region. Finally, from Sunday into early next
week we`ll see a surface ridge build into the region shutting
down chances for precipitation towards the end of the period and
into early next week. Temperatures will trend back below
seasonal normals over the weekend.
.AVIATION /03Z MONDAY THROUGH FRIDAY/...
Through 00Z Tuesday...VFR conditions with decreasing winds to
start the period. After 05Z scattered to broken mix of VFR/MVFR
expected as lower level stratus pushes northward, mainly over
the eastern most locations. Some scattered very light shower or
sprinkle activity possible with this activity, mainly after 09Z
at KMPV and KRUT but there is still a high level of uncertainty.
Dry elsewhere. After 12Z scattered/broken mix of VFR/MVFR
trends VFR at all terminals under light/modest southerly flow in
the 6-10 kt range.
Monday Night: Mainly VFR, with local IFR possible. Slight chance
Tuesday: Mainly VFR, with areas MVFR possible. Likely SHRA.
Tuesday Night: MVFR/IFR conditions possible. Definite SHRA.
Wednesday: Mainly MVFR, with local IFR possible. Chance SHRA.
Wednesday Night: VFR. Chance SHRA.
Thursday: Mainly MVFR, with local IFR possible. Chance SHRA.
Thursday Night: VFR. Slight chance SHRA.
Friday: Mainly VFR, with areas MVFR possible. Chance SHRA.
Area Forecast Discussion
National Weather Service Caribou ME
1202 AM EDT Mon Sep 28 2020
High pressure will remain to our east through Monday. Low
pressure will develop along the Mid-Atlantic coast on Tuesday
and track north across the area Wednesday. Another low from the
Mid- Atlantic coast will cross the region on Thursday. The upper
trough will remain over the area Friday.
.NEAR TERM /THROUGH MONDAY/...
1155 pm Update...
Nighttime satellite imagery shows low cloud shield has spread
as far Northeast as the Caribou/Presque Isle areas and South to
the coast. Have made some adjustments to lower chance of
precipitation through daybreak per latest HRRR showing little
if any precipitation expected overnight.No changes to low
temperature forecast. Areas of fog can also be expected, mainly
downeast overnight, especially the coast. Will maintain the
Dense Fog Advisory there overnight.
Southerly flow of mild and humid air will continue through
Monday ahead of an upper level trough slowly building eastward
over the Great Lakes. Current satellite imagery and observations
show the marine layer has eroded for all but the immediate coast
and several miles inland. The marine layer will start its
progress farther inland shortly and should envelop Downeast
Maine before midnight tonight. Fog is likely again tonight and
may be locally dense, particularly along and within a few miles
of the immediate coast. Confidence was not quite high enough to
issue a dense fog advisory, but one may be needed tonight. Low
temperatures will be significantly above normal in the upper 50s
to low 60s, which are near the normal highs for late September.
Water vapor satellite imagery currently shows an upper level
shortwave moving across the Southeast U.S. This disturbance will
be pulled northward ahead of the aforementioned upper level
trough over the Great Lakes, reaching New England by early
Monday morning. Significant diffluence aloft is noted at 250mb,
with the forecast area within the right entrance region of a jet
streak. Forecast profiles show a small amount of elevated
instability, which along with favorable forcing will lead to
scattered to locally numerous elevated, non-surface based
showers and perhaps an isolated rumble of thunder. The 12z HREF
probability-matched mean QPF is generally around or just above a
quarter inch along and southeast of interstate 95, which would
be the most substantial rainfall in about a month with the
exception of Washington County, which saw greater amounts from
the fringes of Hurricane Teddy. Mostly cloudy skies and showers
will keep high temperatures generally a couple degrees cooler
compared to today in the low to mid 70s , but still well above
.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
The combination of a large area of high pressure to our east and a
trough of low pressure digging into the Great Lakes will bring a
persistent southerly flow of moisture and low clouds Monday night
into Tuesday. The trough digging into the Midwest will be complex
with one predominant upper trough over the Great Lakes and a
southern branch component of the trough digging into the southern
states. An area of low pressure is progged to develop over the
southeast coast just east of the southern branch upper low late
Tuesday into Tuesday evening and from there race northeast over our
region late Tuesday night into Wednesday potentially bringing the
most substantial rain we have seen in weeks. Most of the rain will
fall late Tuesday night into midday Wednesday with up to an inch of
rain likely across parts of our area through Wednesday. Meanwhile,
the southern branch trough, beginning to cut off in the southeast,
will be developing another low along the southeast coast.
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
The cutoff upper southern branch low in the southeast will be
supporting a new surface low developing off the Mid-Atlantic coast
Wednesday evening. This low, likely carrying a lot of moisture, will
race north northeast into New England early Thursday morning and has
the potential to bring another soaking rain to the region through
Thursday morning before continuing on into the Maritimes late
Thursday into Thursday night. A corridor of drier air will follow
later Thursday night into Friday bringing a partly sunny and mild
day on Friday. Meanwhile, the longwave central continental trough
will remain over the Great Lakes and central Canada late in the
week. Saturday into Sunday should be mostly dry with partial
sunshine but spotty showers are possible each day. Another shortwave
rounding the bottom of the trough may slide through on Monday
bringing a chance of some rain Downeast. Otherwise, the weekend into
early next week should be mostly dry as the big trough begins to
weaken and lift out to the northeast.
.AVIATION /04Z MONDAY THROUGH FRIDAY/...
NEAR TERM: MVFR from KCAR/KPQI as of midnight but conditions
will lower to IFR overnight in low clouds. MVFR now lifting into
KHUL where conditions will lower to LIFR/IFR late this evening
and continue in Monday morning. IFR to MVFR at KBGR will lower
to LIFR overnight. LIFR will continue at KBHB overnight into
Monday morning. Dense fog is expected in spots overnight into
Monday morning along the coast, including at KBHB at times.
Scattered showers and perhaps an isolated thunderstorm will be
possible beginning Monday morning, with the best chances from
KHUL south. Marginal LLWS overnight, mainly at at KHUL Breezy
southerly winds will continue with gusts up to 20 kts possible
during the day. Northern Tafs sites will see conditions improve
to MVFR by Monday afternoon, but IFR conditions may persist
Downeast into the afternoon.
Monday night: MVFR, possibly lower to IFR Downeast. S wind.
Tuesday: IFR to MVFR Downeast, MVFR north. S wind.
Tuesday night: IFR to LIFR. Rain. S wind.
Wednesday: LIFR becoming MVFR. S wind.
Wednesday night: MVFR becoming IFR Downeast late. NE wind.
Thursday: IFR becoming MVFR from south to north late NE to NW wind.
Thursday night: VFR. SW wind.
Friday: VFR. SW wind.
The wind will increase and the seas will gradually build through
Monday, but should remain just below small craft advisory levels
with gusts to around 20 kts and wave heights of around 4 feet by
later Monday. Seas were further adjusted down this evening
based on the latest observations. The primary wave system Monday
will be a southerly swell with a period of around 6 seconds.
Gusts up to 25 kt in south winds may affect the offshore waters
Wednesday into Thursday. Seas may build up to 8 ft Wednesday and
10 ft Thursday in response to the south winds. The wind and seas
should diminish and subside Friday into the weekend.
Gusty south to southwest winds and humid conditions will continue
Monday and Tuesday. Scattered showers are expected Monday with
isolated showers on Tuesday. Despite warm temperatures in the
low to mid 70s and south wind gusts of up to around 25 mph, the
overall fire weather threat will be dampened by cloud cover,
humid conditions, and showers Monday. A wetting rain is likely
Tuesday night through Thursday with most areas expected to
receive between 1 and 3 inches of rainfall.
A preliminary record high temperature was set today, 9/27 in
Caribou, Maine. The high of 78F broke the previous record of 76F
set in 1973. Weather records in Caribou date back to 1939. A
preliminary record high temperature was tied in Houlton, Maine
today. The high of 76F tied the record last set in 2017. Weather
records in Houlton date back to 1948.
ME...Dense Fog Advisory until 9 AM EDT Monday for MEZ029-030.
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
758 PM EDT Sun Sep 27 2020
Longwave ridging and associated deep midlevel tropospheric dry air
will remain in place over Southeast Michigan throughout much of the
night. Despite this larger scale forcing for subsidence, shallow
shower activity has developed within the past hour as moisture
between 2500-4500 ft gets shoved into the area amidst a narrow
corridor of low level isentropic lift. RAP soundings show a lapse
rate pocket within the moisture advection now, but then wanes
rapidly during the evening. Model data then suggests increasing low
level frontogenesis across central Lower Michigan after 06Z and
eventually across eastern sections of the forecast area Monday
morning. Forecast soundings support continued high stability in the
midlevels, suggesting precipititon will remain limited initially.
Continue to believe that bulk of precipitation heavier/widespread
precipitation should remain west of the terminals as MVFR clouds to
build into the state. Categorical rain is expected by late Monday
morning at MBS and FNT. Wave of low pressure is expected to ride
along the front Monday afternoon leading to widespread rain activity
For DTW...Shallow rain showers will be possible the first hour or
two of the period. Widespread showers will then develop after 18Z
.DTW THRESHOLD PROBABILITIES...
* Moderate for ceiling 5000 ft or less through tonight, high
Issued at 358 PM EDT Sun Sep 27 2020
Daytime observations indicate the cold front making slow progress
through the central Great Lakes with minimal consequence considering
the above normal temperature and moisture pattern in place across
Lower Michigan. The primary reason for the benign conditions
initially is shown in the 12Z DTX sounding as a layer of very warm
air centered around 800 mb provides a firm cap to surface based
convection. The warm layer is captured well by the models in forecast
soundings which show some erosion during late afternoon and this
evening for a lingering chance of showers within the surface
convergence zone. Erosion of the stratocu field is also anticipated
and required as an indication leading to weak surface based
convection. It still looks like a good call holding off on
thunderstorms as potential remains limited by low instability.
Consensus of model MLCAPE estimates struggle to project 500 J/kg
during peak heating.
The shallowness of the front and its alignment with SW flow aloft
keep the boundary moving slowly or even stalling from the Thumb
region to the west end of Lake Erie tonight. This provides the
opportunity for a couple waves of low pressure to ripple along it
that are mainly the result of vertical motion surges forced by the
upper jet. Defined leaf structure in WV satellite imagery and the
banded structure of showers in radar composite in the Midwest this
afternoon depict the strong organization of the jet and favorable
alignment with elevated portions of the frontal zone. Lightning
strikes in the pattern have been confined farther south locations
along the surface front feeding into respectable shower intensity
farther north through eastern Iowa and southern Wisconsin. GFS
timing and location into Lower Michigan tonight is preferred judging
by its farther west positioning of the QPF axis centered on Iowa
today. The solution may be slightly slower by a few hours after
midnight before the shower band moves into the Tri Cities with
categorical coverage and then spreading eastward through Monday
Upper level jet energy in the upstream flank of the current long
wave trough axis initiates aggressive height falls across the
southern Plains tonight and the mid Mississippi valley during
Monday. The process also spawns a lead short wave that moves along
the front and leads to cyclogenesis nearly overhead in SE Michigan
Monday afternoon. Expect an uptick in both coverage and intensity of
showers due to this forcing and interaction with the elevated
frontal zone. Lower resolution/coarser model solutions show good
consensus on the added smaller scale forcing in 12 hr QPF fields
that have a meaningful areal coverage footprint approaching 1 inch
before the system dry slot punches in Monday night. The other
notable aspect of conditions will be much cooler temperatures
compared to recent days as the clouds and rain combine to hold
readings in the 60s Monday afternoon except for possibly Detroit to
The long wave trough matures full latitude during the mid week
period carved out by additional surges of strong upper level jet
energy. Each surge generates or is accompanied by small scale
circulations that keep unsettled weather in place in the central
Great Lakes. Predictability is on the low side with these features
however that being said it does look like SE Michigan will be in
between waves during much of Tuesday. Should dry weather hold, then
a few intervals of sunshine can help lift temperatures into the mid
60s for afternoon highs. Similar conditions are expected Wednesday
leading up to the next front and step down on temperatures. Guidance
highs are only in the 50s by Thursday with the added aspect of rain
showers likely augmented by activation of the Great Lakes. The cold
air last well into next weekend accompanied by lows in the 30s, at
least 10 degrees below normal to start October.
A slow-moving cold front is positioned northeast-to-southwest across
the central Great Lakes this afternoon. This front will progress
eastward across Lake Huron tonight and reach Lake St. Clair and
western Lake Erie Monday morning. Winds will generally become light
and variable with the frontal passage, while showers begin to move
in late tonight and likely persist through much of Monday with the
front stalling out. Model consensus points to a low pressure system
developing along this front over the Ohio Valley and tracking north-
northeast through the central/eastern Great Lakes Monday night. The
exact track and strength of this low will have meaningful impacts on
the wind direction and magnitude. Some of the more aggressive
solutions with the low tracking farther west hint at possible gales
across Lake Huron late Monday night into Tuesday morning. Will hold
off on a Gale Watch until better confidence is reached. Small Craft
Advisories may be needed during this period as well. Breezy
southwest wind looks to follow the departure of the low on Tuesday
and Wednesday with additional showers lingering across the region.
A slow moving cold front generates scattered showers this evening
and then supports a band of steadier rain after midnight through
Monday morning. The front stalls over SE Michigan by Monday
afternoon allowing showers to increase coverage and intensify.
Moderate to locally heavy rainfall occurs over much of the region
producing rainfall totals averaging around 0.5 inch. A few locations
could see totals of .75 to 1 inch mainly during the time from 6 AM
to 6 PM Monday. These rainfall amounts have been revised higher but
still do not pose significant flooding potential outside of water
ponding on roads and in other prone areas.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
You can obtain your latest National Weather Service forecasts online
AREA FORECAST DISCUSSION
National Weather Service Eureka CA
251 PM PDT Sun Sep 27 2020
.SYNOPSIS...Warm and dry conditions along with robust northeast
and east winds will result in critical fire weather conditions
through Monday. The offshore flow is expected to produce record
heat for coastal areas and possibly smoke aloft Monday. Dry
weather with no chance for rain and above normal temperatures are
expected for the remainder of next week.
.DISCUSSION...High pressure building into the areas is bringing
mainly clear skies and dry conditions. A few valleys saw some fog
this morning, but this has cleared up. The northeast winds were
gusty on the higher ridgetops this morning and the RH was low at
the higher elevations, mainly above 4,000 feet. At the coast
northerly winds have increased to around 15 to 20 mph with gusts
to 30 mph. This is helping to keep the temperatures near the
coast from getting out of the upper 60s to 70s. Inland areas are
expected to see temperatures warm to around 100 in the interior
Tonight moderate to strong northeast to east winds are expected
again. RH is expected to start off lower than it was this morning
and the poor recoveries are expected to extend lower in the
valleys. Monday the winds will start to diminish, but remain
offshore. This should allow temperatures at the coast to warm into
the 80s. The record for Eureka is 79 degrees so it may be broken.
Heat risk continues to look moderate, especially near the coast
due to the unusably warm temperatures expected, but will continue
with just messaging about it and not issue an advisory.
Monday night into Tuesday morning there is still some offshore
flow, but the winds aloft diminish significantly from Monday
morning. Still, this should be enough to keep most of the stratus
away from the coast again, but not expecting to extend the Red
Flag warning. It may also continue to bring smoke to the coast,
but this will largely depend on how much smoke the fires are
Tuesday afternoon the ridge of high pressure starts to move off to
the east. This will bring southerly winds to the coastal areas and
will likely bring a southerly surge of stratus to the Mendocino
coast. It is expected to be fairly shallow and may bring some
dense fog as well. For now am only expecting it to make it to Cape
Mendocino, but it could make it farther than expected.
Wednesday the high pressure moves slightly more to the east and at
some point during the day stratus coverage is expected to expand
into the northern waters. Temperatures will cool in the near
coastal areas as the marine layer starts to influence temperatures
more, but inland areas should remain in the upper 90s to near 100.
Thursday and into the weekend the models are in good agreement on
the ridge slowly shifting to the east. The WPC ensemble clusters
all show ridging, although late in the period there a few small
variations in the exact location of it. This is expected to
gradually deepen and expand the marine layer. Thursday night or
Friday some models are showing a weak shortwave riding up the west
side of the ridge. This could bring the potential for
thunderstorms, but for now it looks to remain too dry. MKK
.AVIATION...Prevailing northerly winds with gusts of 20 knots or
more are expected to intensify this afternoon at KCEC and
eventually ease to gentle breezes around midnight. North winds at
KACV increased this afternoon and are expected to get peak gusts
around 20 knots. Northerly winds will diminish and ease to a
southerly bearing with a light breeze, early in the evening at
KACV. MVFR/VFR flight categories are expected for the TAF period
at the coastal terminals as high pressure intensifies, clearing
out skies. Light winds at KUKI and VFR conditions are expected to
prevail with HRRR smoke models showing the possibility of smoke
plume intrusion this evening. /EYS
.MARINE...Northerlies have intensified over the coastal waters
today with Gale conditions developing over the outer waters. The
inner waters have also become hazardous with stronger winds around
Point Saint George and Cape Mendocino. Winds will begin to taper
off later tonight from south to north. Headlines are in place for
all zones and will begin to fall off this evening as winds weaken
and as we head into the upcoming work week. Winds will become
generally in the light to gentle breeze range Monday afternoon,
with some southerlies developing over the waters. Northerlies are
forecast to redevelop and increase by Wednesday evening.
Otherwise, the current northwest swell will slowly continue to
wane with another NW swell set to move through the waters on
.FIRE WEATHER...The higher elevations this morning saw gusts of
around 45 mph with RH only in the 20s. In general winds were
lighter and RH was higher below 4,000 feet. Winds have diminished
some this afternoon, but RH remains low in many areas. Tonight
the higher winds are expected to be slightly more widespread and
the low RH recoveries will be in more areas than just the highest
peaks. Monday afternoon will see very low RH with many inland
areas seeing around 10 percent. The light offshore flow will
likely bring warm temperatures and low RH fairly close to the
coast. Winds will likely diminish in the afternoon, but for now
will leave the RFW in place through the evening due to the very
low RH. Monday night into Tuesday morning RH recoveries will still
be poor, but will should improve slightly from Monday morning.
Also winds are expected to be quite a bit lighter. The surface
winds still show some 5 to 10 mph winds on the ridges, but the
winds aloft become much lighter.
No rain is expected through the end of the week. High pressure
will start to edge out of the area. This should bring slightly
cooler temperatures and a deeper marine layer. MKK
.BEACH HAZARDS...A northwest swell peaking around 8 feet at 16
seconds, will move through the waters Monday. It is possible that
this could produce a small sneaker wave threat, however locally
generated short period waves should limit the threat. A beach
Hazard Statement to highlight this will not be issued at this time
as the threat looks to be minimal. Conditions will continue to be
CA...Red Flag Warning until 9 PM PDT Monday for CAZ201>204-211-212-
NORTHWEST CALIFORNIA COASTAL WATERS...
Small Craft Advisory until 3 AM PDT Monday for PZZ450.
Gale Warning until 3 AM PDT Monday for PZZ470.
Small Craft Advisory until 9 PM PDT this evening for PZZ455.
Gale Warning until 10 PM PDT this evening for PZZ475.
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AREA FORECAST DISCUSSION
National Weather Service Hastings NE
649 PM CDT Sun Sep 27 2020
.DISCUSSION...(This evening through Sunday)
Issued at 314 PM CDT Sun Sep 27 2020
As mentioned in the previous update, precipitation has been more
persistent than previously expected. Models also haven`t been
handling the coverage very well. One band of rain and even a few
thunderstorms clipped southeastern portions of the area this
morning on an area of 850-700mb frontogenesis. A more persistent
band of light rain continues to slowly dip southward across the
area. This appears to be more closely associated with 700-500mb
frontogenesis on the southern edge of the upper trough that
digging southward over the Plains.
This band of light rain will slowly slide southward and dissipate
late this afternoon into this evening. Rain totals have generally
been 0.01-0.05" under this band, so unfortunately it will have
little to no impact on any drought conditions. The HRRR shows a
few more showers or sprinkles may percolating across eastern and
east-central Nebraska later this evening, so I added a sprinkle
mention to account for this. Tonight, skies will slowly clear, but
we should keep enough of a breeze to avoid a significant
cooldown. Lows are forecast to be in the low to mid 40s.
Monday will be chilly and breezy as we stay in the well-established
northerly flow at the surface and aloft. Gusts are forecast to be
around 30 MPH and highs will struggle to reach the mid 60s. Skies
are forecast to be mostly clear across most of the area, but
another lobe of vorticity at 500mb may bring some mid to high
clouds to northeastern portions of the forecast area.
Winds will decrease Monday night as the upper trough slowly moves
east and high pressure passes to our southwest. This could allow us
to drop into the 30s, and potentially produce the first frost of the
year for portions of the area. Even if we miss out on this frost
Monday night, we will have plenty more opportunities coming up.
Tuesday will likely end up being the nicest day of the week.
Temperatures should return to the 70s and winds will back off as the
colder air at 850mb shifts off to the southeast. This trend will
continue into Wednesday, but a broad trough centered over the Hudson
Bay will continue to expand, pushing another shot of cold and breezy
weather in for late Wednesday into Thursday.
This cold airmass is poised to bring us our first freeze of the
season Thursday night. Forecast temperatures have not changed much
with this forecast package, still ranging from 30 to 35 degrees.
There is still some uncertainty on how cold we actually get, but
synoptically it is certainly a favorable setup with models showing a
1028mb surface high sliding in.
Beyond that, it looks like temperatures will moderate some headed
into the weekend, but we will still stay below normal and have some
potential frost issues each morning. There is an outside chance for
some rain Saturday into Sunday, but the probability is too low to be
included in the forecast at this point.
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Tuesday)
Issued at 640 PM CDT Sun Sep 27 2020
Wind gusts should back off a bit for tonight, but still remain a
bit breezy behind a second cold front coming through in two days.
We might have been close to LLWS issues overnight, especially for
KEAR, but wind speeds at the surface should be strong enough to
preclude this as an issue. We may have a mid- level ceiling from
time to time, but VFR conditions are forecast for the entire
Area Forecast Discussion
National Weather Service Indianapolis IN
1153 PM EDT Sun Sep 27 2020
The AVIATION Section has been updated below.
Issued at 215 PM EDT Sun Sep 27 2020
A cold front over the Upper midwest and plains stats will push
toward Indiana tonight and across Indiana on Monday. The front is
expected to bring rain showers to Central Indiana...mainly late
tonight and Monday.
Cooler High pressure will build across Indiana on Tuesday and
Wednesday...bringing dry weather and highs only in the 60s.
The cooler and mainly dry weather is expected to persist into the
weekend...as below normal temperatures will be expected.
.NEAR TERM /Rest of Tonight/...
Issued at 930 PM EDT Sun Sep 27 2020
Inserted mention of thunder for the next few hours to match
current radar trends. Also, sped up timing of rain across the
forecast area through Mon 06Z. Otherwise, no other changes to
Surface analysis early this afternoon shows a cold front
stretching from SE WI to Western IL...Central MO and SE KS.
National Radar mosaics show showers and a few thunderstorms in
the wake of the front. High pressure was found over the Carolinas
resulting in a moderate SW surface flow in place across the
forecast area. Dewpoints were in the 60s. Water vapor imagery
shows a trough over the northern United States with a digging
trough over the Dakotas.
The models tonight show trough aloft over the northern Plains to
continue to deepen...providing a kicker for the surface cold
front to push eastward tonight. SW flow is expected in place aloft
tonight as forcing dynamics arrive aloft. GFS 305K Isentropic
surface shows some lift...mainly along the front overnight with
favorable specific humidities...near 4.5 g/kg. This best forcing
looks to arrive within the forecast mainly overnight. HRRR agrees
as it progs precip with the front arriving after 04z-06z.
Forecast soundings show a gradual saturation through the overnight
periods. Thus confidence is high for some light rain
amounts...mainly overnight and will trend pops higher then. Given
the expected clouds and rain...will trend lows at or above the
.SHORT TERM /Monday through Wednesday/...
Issued at 215 PM EDT Sun Sep 27 2020
Monday morning will begin with the cold front over
Indiana...beginning to push out of the state through the day.
Forecast soundings on Monday morning show the best saturation as
the system passes...mainly across the central and eastern parts
of the forecast area. Pwats look to remain over 1.3 during the
morning hours. Aloft...a deepening trough axis looks to be pushing
across the Indiana...again providing more forcing. Thus
confidence remains high for rain on Monday morning as these
features pass. Will trend pops at or above the NBM...particularly
across the east as timing is best there. Will trend highs at or
below the NBM as cold air advection will be in play along with
rain showers in the wake of the front.
Forecast soundings and time heights show the arrival of
subsidence on Monday night as forecast soundings dry out through
the column. Isentropic surfaces show downglide as surface high
pressure begins to build across the plains. Cyclonic flow aloft
may lead to some lingering clouds in the evening across
Indiana...but overall decreasing cloudiness should be the main
trend. Given our strong cold air advection that will be expected
through the day will trend low at or below the NBM.
Quiet and Dry weather is then expected from Tuesday through
Wednesday. Forecast soundings show a dry column through this
period as Westerly surface flow looks to remain in place. Surface
ridge of high pressure will remain in place across the region on
Tuesday and Tuesday night...before a secondary dry surface trough
passes on Wednesday. Aloft Deep troughing remain in place and
moisture will remain a problem for Wednesday`s system. Thus will
trend toward partly cloudy skies and temps at or below the NBM.
.LONG TERM /Wednesday night through Sunday/...
Issued at 157 PM EDT Sun Sep 27 2020
As the long term begins, models are in good agreement that a cold
front will be near/just through the forecast area, with a large
upper trough in place over the Great Lakes. Central Indiana will
remain in a cyclonic flow pattern, with a Canadian surface high
pressure system building into the area over the end of the week and
moving through during the weekend. The cyclonic, cold advection
pattern will mean temperatures quite a bit cooler than normal with
highs in the 50s to lower 60s and lows in the 30s and 40s, with some
potential for frost. Until the surface high can get overhead, the
cyclonic upper flow will likely mean mostly cloudy skies during the
afternoon hours. At this time, chances for precipitation during the
long term look anemic with very little moisture available.
.AVIATION /Discussion for the 28/06Z TAF Issuance/...
Issued at 1145 PM EDT Sun Sep 27 2020
VFR conditions continue to hold at all TAF sites for now except
KLAF where rain has been falling. KLAF is right around the
MVFR/VFR mark at this time and anticipate all TAF sites to still
trend downward to MVFR as well between Mon 06-09Z and even
further to IFR around Mon 12Z. Forcing will strengthen and rain
showers will become more widespread with approaching cold front.
The bulk of the precipicitation will be in the Mon 10-18Z time
frame. As the front pushes farther southeastward through the day
though, there will be a gradual improvement from IFR to MVFR and
then back to VFR by mid to late afternoon. Meanwhile, winds will
shift to the northwest with frontal passage and become a bit
breezy from Mon 16-22Z with some gusts up to 19 kts.
AREA FORECAST DISCUSSION
National Weather Service Raleigh NC
940 PM EDT Sun Sep 27 2020
A strengthening southerly flow will bring increasing moisture into
North Carolina tonight through Monday, ahead of a cold front that
will push slowly east through the region late Monday night through
Tuesday night. This front will stall near the Carolina coast Tuesday
night, ahead of a strong upper level disturbance that will cross the
region Wednesday into Wednesday night and push the front offshore.
Cool high pressure will build into the area late week into the
.NEAR TERM /THROUGH TONIGHT/...
As of 930 PM Sunday...
1014mb surface high pressure has shifted to the SC coast this
evening, while aloft a lower amplitude trough is lifting across the
southern Appalachians. An area of rain has been moving north from
GS/SC into the Piedmont and coastal plain, though with rather dry
air below 600mb, rain has either been very light or not hitting the
ground, despite 40m height falls assoc with the trough. Will keep
low-end chance POPs in the coastal plain through early morning, but
expect most areas will be dry. The other concern has been the
potential for fog given that the near surface airmass this still
moist. While the surface high is not directly overheard, many areas
have or will decouple. The back edge of the mid and highs clouds is
approaching the western Piedmont, so perhaps those areas will be
best suited for fog, though forecast soundings and HRRR guidance
tend to support more stratus. Lows 63-66.
.SHORT TERM /MONDAY THROUGH MONDAY NIGHT/...
As of 330 PM Sunday...
A deep upper-level trough will dig into the lower Mississippi River
Valley Monday and approach western NC by Monday night. Ahead of the
trough, moist, south to southwesterly flow and weak MLCAPE will help
generate isolated to scattered showers across southern portions of
central NC Monday morning, then across all of central NC by the
afternoon. Sufficient heating will create the possibility of a
thunderstorm or two, mainly across southern portions of central NC
in the afternoon. Precipitation chances increase late Monday night
as the main trough approaches the region and upper-level support
becomes favorable for heavier showers and isolated thunderstorms.
Highs Monday will range from the upper 70s NW to the low 80s SE, and
lows will range from the mid to upper 60s.
.LONG TERM /TUESDAY THROUGH SUNDAY/...
As of 415 PM Sunday...
As a strong trough amplifies over the Midwest, a mid and upper
level low moves over SC into NC Tuesday and into Tuesday night. A
warm southerly flow will help the moisture move north into the
Central NC and bring showers and thunderstorms making flooding the
main concern. Strongest of these storms are to occur in the late
afternoon and evening hours of Tuesday with some remnants in the
east Wednesday morning. QPF amounts for Tuesday and Tuesday night
range 1 inch to 1.25 inches in the south east. SPCs outlook for
Tuesday currently has all of Central NC in a marginal risk for
Severe weather and WPCs Excessive Rainfall Outlook has all of
Central NC in a slight risk.
After a brief lull of the first round of storms from Tuesday, storms
will continue once again on Wednesday and Wednesday night, but as
the strong upper level low starts to move over the area mixed with
convective elements, some storms will likely produce small
hail/graupel and thunder. As the front finally moves through on
Thursday there is a chance of showers mainly in the NE coastal plain
regions. For the remainder of the forecast, central NC should remain
dry as a Canadian high pressure builds in.
Temperatures on Tuesday are near normal in the upper 70s and low 80s
in the south- before the front approaches. As October approaches
things take a quick turn as high temperatures on Thursday become 5
degrees below normal. Our coldest nights are expected to be Friday
and Saturday night as the cool high pressure builds in with lows in
the mid to upper 40s.
.AVIATION /00Z MONDAY THROUGH FRIDAY/...
As of 740 PM Sunday...
Currently an area of rain extends from the SC/GA coastal area north
into central NC, although most of the rain is not hitting the ground
in central NC owing to dry air below 15k ft. Some additional
showers and storms over northern GA have been weakening since 21Z,
so the general expectation is that some light rain or showers may
impact FAY and RWi between 02Z and 08Z, with otherwise dry
conditions to the west. Mid/high clouds will limit fog development
early, but with no change in airmass since last night and drier air
aloft working in from the west, should see some IFR/LIFR cigs spread
into the Piedmont, with the potential for a shorter period of fog
closer to 12Z...mainly at KGSO/INT, although confidence is not high
enough to rule it out anywhere.
Low clouds will lift through the morning hours on Monday, likely
return to VFR by the afternoon, with scattered showers possible in
the afternoon as well.
Outlook: A strong low pressure system will bring the potential for
widespread adverse aviation conditions later Tuesday into Wednesday.
Mostly dry weather is expected Thursday, then a small chance for
showers returns on Friday.
Area Forecast Discussion
National Weather Service Shreveport LA
905 PM CDT Sun Sep 27 2020
With the aid of the Nighttime Microphysics GOES 16 RGB Channel
and 02z observations and regional radar mosaic, able to pick the
leading edge of a much cooler airmass in the form of a cold front
extending from between Fayetteville and Fort Smith, Arkansas to
south and east of Mcalester, Oklahoma to near Mineral Wells,
Texas. Southeast winds ahead of this cold front along with strong
northerly winds behind the boundary is still supporting some weak
to moderate frontal forcing which upper forcing still lags the
surface boundary a good bit. Mesoanalysis showing plenty of sfc
based CAPE near 2000J/KG but a strengthening boundary layer
suggests that the convection along and in the wake of the cold
front itself may be becoming slightly elevated. Still cannot rule
out the possibility of an isolated severe thunderstorm or two
near and northwest of the I-30 Corridor overnight but the window
of opportunity for this possibility will be closing quickly the
closer we get to the midnight hour.
For the update, previous forecast calls for categorical pops
across our northwest third with likely pops as far south as the
I-20 Corridor in Northwest Louisiana through 12z in the morning
and the latest HRRR along with 00z NAM output is in good agreement
with this timing and coverage. Sharp temperature drop behind the
cold front and thus a good 10 to 20 degree temperature drop can be
expected by 12z for those behind the boundary. May need a Lake
Wind Advisory for strong post frontal winds on Monday but will
forego that possibility to the next shift with further model data
to make this determination or not.
.PREV DISCUSSION... /issued 528 PM CDT Sun Sep 27 2020/
Much advertised cold front as of 22z was located across NE OK into
NW and W TX early this evening. Cu field ahead of this feature
across our airspace should continue to diminish this evening
before reforming later tonight as the boundary nears our northwest
airspace by midnight. With the aid of surface convergence, low
level moisture and upper level forcing, should see convection
develop along this boundary and move south and east through our
airspace during this TAF period. Began VCTS at the TXK/TYR/GGG/ELD
and SHV terminals beginning at 06z and slightly later for the LFK
and MLU terminals with TEMPO groups during the predawn hours for
TSRA, VSBY restrictions as well as MVFR ceilings and wind gusts
with convection. Otherwise, MVFR ceilings should quickly become
VFR and/or scatter out from northwest to southeast during the day
Monday with strong post frontal winds from the northwest,
sustained near 10-15kts with gusts upwards of 20 to 25kts at most
terminals on Monday.
.PRELIMINARY POINT TEMPS/POPS...
SHV 63 74 54 74 / 70 50 0 0
MLU 65 76 54 74 / 30 70 0 0
DEQ 58 73 49 72 / 90 10 0 0
TXK 60 71 51 69 / 90 20 0 0
ELD 60 74 51 72 / 80 60 0 0
TYR 61 73 50 74 / 70 10 0 0
GGG 61 75 51 74 / 70 20 0 0
LFK 64 76 54 77 / 40 50 0 0