Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/21/24
Area Forecast Discussion
National Weather Service Boston/Norton MA
1007 PM EDT Wed Mar 20 2024
.SYNOPSIS...
A strong cold front will move across the region this evening with
showers and perhaps an isolated rumble of thunder. Gusty wind
develops overnight into Thursday, accompanied by drying
conditions. While there are still details to be ironed out, a
more active weather pattern then evolves for Friday night into
the weekend. A strong frontal system may bring the risk for
minor accumulating snow in the interior Friday evening, but
transition to widespread soaking rain Saturday, capable of poor
drainage flooding and rises on rivers and streams. A risk for
minor coastal flooding and beach erosion is possible this
weekend as well.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Update: 10pm
Showers have largely come to an end as the cold front clears
eastern Massachusetts. Behind the front clearing skies and
increasing wind gusts from the WNW and NW, generally 25 to 35
mph, with a few isolated reports of 40 mph. CAA is already
driving in the colder temperatures with many reporting current
temperatures in the upper 20s across western Massachusetts to
the middle/upper 30s across the coastal plain. Overall the
forecast remains in good shape with no significant changes
needed at this time. See prior discussions below.
703 PM Update:
Though there are a few ongoing light showers across east CT,
central/eastern MA and RI per obs and radar mosaic, the focus
for more active weather turns to western MA and northwest CT. A
powerful cold front is producing a narrow "fine line" of brief
but intense convective showers with local gusts up to 40 kt;
while rain initially begins, webcams and spotters in western MA
and eastern NY indicate rain is changing over to a brief period
of graupel then ending as a brief bout of snow showers. NLDN
indicates there has been instances of lightning associated with
this line, and we did have a spotter report seeing lightning in
northwest MA. Most recently, BAF reported gusts to 40 kt with 1
mile rain upon this front`s passage. Opted for an SPS to handle
this situation, initially for northern Hartford County and the
Berks/I-91 corridor but wouldn`t discount needing additional
statements if this line of gusty showers continues to generate
lightning. This line of gusty showers is also moving rather
quickly, and it should make it all the way to the coast by 02z.
The best chance for coatings of snow is across the higher
terrain but will be too brief for anything greater than a
coating. Tried to better show the timing a little better with
this forecast update.
Upon passage of this cold front, expect a marked and significant
change in air mass, along with frequent NW gusts in the 25 to
35 mph range. Temps are now around freezing in the post-frontal
air mass in eastern NY, but dewpoints have also crashed through
the 20s and it is hard not to ignore dewpoints down into the
low teens back across western NY. So it will turn significantly
drier, and will go with dry wx after midnight in all areas.
Think lows were on track, though did blend some of the 22z HRRR
guidance into the going forecast to better show the rapid fall
in temps immediately after FROPA.
Previous discussion:
KBOX radar currently revealing a few clusters of showers over
southern New England at this hour. Dewpoint depressions still have a
rather large spread so precip intensity is on the lighter side. We
may see intensity increase into the evening showers as forcing for
ascent ahead of an advancing cold front strengthens. Furthermore
moisture will be on the rise as well. This may lead to a few local
downpours and possibly even some graupel/small hail with limited
CAPE and very steep lapse rates through the mid-levels. Immediately
behind the front temperatures drop rapidly and may support a brief
period of snow, particularly over the higher elevations across
interior MA. Not expecting any accumulations given surface temps
likely won`t fall below freezing until after the precipitation has
come to an end. Fair agreement among hi-res model guidance indicates
precipitation should taper off from west to east between 8PM and
midnight.
Overnight, winds shift to the west and gradually strengthen to
sustained speeds of 15 to 25 mph with gusts from 30 to 40 mph across
the forecast area. Winds will likely be stronger from 45 to 55 mph
over The East Slopes of The Berkshires where a wind advisory is in
effect through tomorrow evening. A chilly air mass follows the
frontal passage with clearing skies, though mechanical mixing in the
CAA regime will limit significant cooling. Nonetheless, overnight
lows still well below normal with most locations in the 20s prior to
sunrise.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
Tomorrow
Post frontal air mass dominates the weather tomorrow in southern New
England. Low pressure to the north and high pressure to the south
will place southern New England beneath a tight pressure gradient in
a CAA regime which will support gusty west/west northwest winds
through tomorrow night. Deep mixing will allow 30 to 40 knot winds
aloft to mix to the surface, so despite a dry sunny/day it will be
cold and blustery. 925 hPa temps around -5 Celsius will only support
high temps in the upper 30s to low 40s. A wind advisory will be in
effect for The East Slopes of The Berkshires through tomorrow
evening where 45 to 55 mph wind gusts will be possible at times.
Deep mixing will also allow drier air aloft to mix to the surface,
supporting low dewpoints. Leaned on 10th percentile NBM for dewpoint
guidance which paints single digit dewpoints across much of southern
New England. This will support minimum relative humidity values
below 30 percent. With gusty winds in place, there may be an
elevated risk for fire weather, though recent wetness may help
offset the dry/windy weather. We will be collaborating with state
fire weather partners to determine if a special weather statement
for elevated fire danger is necessary for tomorrow.
Tomorrow Night
Pressure gradient relaxes and allows gusty winds to come down to
more modest levels ranging from 20 to 30 mph. This will continue to
support mixing overnight that will limit cooling potential. Expect
tempts to be a bit cooler tomorrow night with some interior
locations falling into the upper teens with low to mid 20s
elsewhere.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Highlights:
* Dry weather on Fri with easing winds.
* Unsettled Fri night and especially Sat/Sat night. Though minor
snow accum possible Fri night in the interior, mainly
widespread soaking rain capable of urban and poor drainage
flooding and river rises is possible. Where the heaviest rain
may fall is still highly uncertain.
* Possible splashover or minor coastal flooding along the South
Coast Sat.
* Trending drier for Sun and Mon. However persistent, enhanced
easterly flow Sun/Mon may bring beach erosion and minor coastal
flooding risks for the eastern coasts.
Details:
Friday:
Seasonably strong 1030 mb high pressure area builds in on Friday,
relaxing the NW pressure gradient and supporting mostly clear skies
and dry weather. The air mass will still be quite dry, and should be
drier than on Thurs. Lowest relative humidities may drop to around
25-35 percent. Thus a possible period of elevated fire weather
concerns given these low relative humidities, however wind speeds
will be substantially lighter than Thurs and out of the W/WSW. Highs
mainly in the lower to middle 40s.
Friday Night into Saturday Night:
While there are still uncertainties, there is growing consensus on
more active weather being centered primarily in this forecast
period.
A potent northern stream shortwave trough combined with rich
Atlantic moisture, focused by an inverted surface trough associated
with low pressure over the Atlantic seaboard looks to spread
increasing chances for precipitation. It looks like precipitation
may begin after midnight Friday night, and in interior sections of
Southern New England, air mass looks sufficiently cold enough to
start as a period of light snow. Though a couple of inches of wet
snow accumulation are possible particularly along and north of the
Mass Pike, the strong warm thermal and moisture advection should
transition any snow over to plain rain with very limited if any
impact from minor accumulation of snow. While snow may begin at
outset in the coastal plain, little to no accumulation is expected
with a rapid changeover to plain rain.
The period of greater adverse impact is on Sat into Sat night.
Widespread soaking rains are likely in all areas as an anomalous
PWAT plume (up to an inch, per the SREF mean) interacts with the
inverted surface trough. Both global model ensembles and their
deterministic solutions show an narrow axis of heavy rainfall of
both varying magnitude and placement that makes it difficult to
project more specific location and timing impacts. But there is a
growing potential for heavy rainfall somewhere across SNE Sat into
Sat night which could lead to poor drainage/urban street flooding as
well as rises on larger rivers and smaller creeks/tribs. MMEFS
probablilistic hydrographs from GEFS-based QPF bring several
rivers in RI into minor flood stage (including the Pawtuxet and
Wood River basins), with lower potential for stages in the
Moderate category. Between this soaking rain and potential for
snowmelt both locally and upriver, rivers should stand to rise
during the weekend but exactly which locations receive the most
rain and thus experience the greatest rises is still unclear at
the time.
A persistent period of onshore flow is also likely to begin Friday
evening and continue potentially into much of the weekend. While
astro tides are on the low side (around 9.5 ft MLLW for Boston
Harbor and around 4.25 ft for Providence/Fox Point), the risk for
splashover or minor coastal flooding could exist across multiple
tidal cycles. With stronger SSE flow on Sat, this risk may initially
be focused along the South Coast, then become more focused toward
the eastern MA coast for the weekend/early next week.
Sunday into Early Next Week:
Forecast confidence in this period remains below normal in this
period; however recent model solutions have backed off a bit on
rainfall chances lingering into Sunday and Monday, trending towards
drier weather as a strong 1040+ mb high pressure builds in from
Canada. Am still a little hesitant to dismiss the potential for
showers into eastern sections of SNE as yet, so I did keep a mention
of shower chances going. We also have to watch for the potential for
the distant ocean low to move northward and spread showers back into
our eastern areas later Sunday or Monday, but this is not well
agreed upon. Once there is better consensus on this evolution across
the model suite, later forecasts can then increase or
remove/decrease shower chances.
However a period of enhanced E/NE onshore flow appears likely in
this period, and that would bring a potentially continued risk for
beach erosion and/or splashover or coastal flooding on the eastern
coastlines.
&&
.AVIATION /02Z THURSDAY THROUGH MONDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High- greater than 60 percent.
00z TAF Update:
Tonight: High confidence.
Generally VFR in the very short term; however strong cold front
to move across the TAFs in the 00-02z timeframe. This will bring
a period of IFR-visby rain to snow showers/graupel along with
an abrupt windshift from SW/WSW to gusty NW winds (gusts 25-30
kt). See TAFs for specific timing. After 02z, rapid clearing to
VFR but with NW gusts 25-35 kt.
Thursday and Thursday Night... High Confidence.
VFR. Strong west/northwest wind 15 to 25 knots, with gust up to 40
knots possible. Gusts begin to back down Thursday evening.
KBOS TAF... High confidence in TAF. Strong cold frontal passage
brings brief period of 1SM RASN between 01-02z, however there
will be no accumulation of snow; gusty windshift to NW takes
place around 02z with VFR conditions, gusts up to 30 kt thru
daybreak. VFR with NW gusts up to 35 kt on Wed.
KBDL TAF...High confidence in TAF. Strong cold frontal passage
brings brief period of 1SM RASN between 00-01z, however there
will be no accumulation of snow; gusty windshift to NW takes
place around 01z with VFR conditions, gusts up to 30 kt thru
daybreak. VFR with NW gusts 35-40 kt on Wed.
Outlook /Friday through Monday/...
Friday: VFR. Breezy.
Friday Night: Mainly VFR, with local MVFR possible. Breezy.
Chance RA, chance SN.
Saturday: MVFR/IFR conditions possible. Windy with gusts up to
30 kt. RA.
Saturday Night: Mainly VFR, with local IFR possible. Windy with
gusts up to 35 kt. Chance RA, chance SN.
Sunday: VFR. Strong winds with local gusts up to 40 kt. Slight
chance RA.
Sunday Night: VFR. Strong winds with gusts up to 40 kt. Chance
RA, slight chance SN.
Monday: VFR. Strong winds with gusts up to 40 kt. Slight chance
RA.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Marine
Tonight through Tomorrow Night
A surface cold front moving over the coastal waters this evening
will be followed by a period of dry/windy conditions. West/west
northwest winds with sustained speeds of 20 to 30 knots are likely
to persist through tomorrow night with periods of 30 to 40 knot
gusts. A gale warning is in effect through tomorrow evening.
Outlook /Friday through Monday/...
Friday: Winds less than 25 kt. Seas locally approaching 5 ft.
Friday Night: Winds less than 25 kt. Chance of rain.
Saturday: Low risk for gale force winds with gusts up to 35 kt.
Local rough seas. Rain. Local visibility 1 to 3 nm.
Saturday Night: Moderate risk for gale force winds with gusts
up to 40 kt. Rough seas up to 13 ft. Rain. Areas of visibility
1 to 3 nm.
Sunday through Sunday Night: Moderate risk for gale force winds
with gusts up to 40 kt. Rough seas up to 13 ft. Chance of rain.
Monday: Moderate risk for gale force winds with gusts up to
45 kt. Rough seas up to 13 ft. Chance of rain.
&&
.FIRE WEATHER...
330 PM Update:
Thursday and Friday...
Period of elevated fire weather concerns develops Thursday and also
potentially into Friday. Thursday offers a combination of gusty NW
winds between 35 and 50 mph and lowest RHs around 20-35 percent.
For Friday, NW to W winds are lighter but RHs project to be lower in
the upper teens to 30 percent range. Will reassess with incoming
guidance before coordinating with our fire weather partners over the
coming days.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...Wind Advisory from 5 AM to 8 PM EDT Thursday for MAZ002-008-
009.
RI...None.
MARINE...Gale Warning from 2 AM to 8 PM EDT Thursday for ANZ230.
Gale Warning from 2 AM Thursday to 2 AM EDT Friday for ANZ231-
250-251.
Gale Warning until 2 AM EDT Friday for ANZ232>235-237-254>256.
Small Craft Advisory until 2 AM EDT Friday for ANZ236.
&&
$$
SYNOPSIS...Loconto/RM
NEAR TERM...Loconto/Dooley/RM
SHORT TERM...RM
LONG TERM...Loconto
AVIATION...Loconto/RM
MARINE...Loconto/RM
FIRE WEATHER...RM
Area Forecast Discussion
National Weather Service Dodge City KS
540 PM CDT Wed Mar 20 2024
.KEY MESSAGES...
- Major storm system late weekend into Monday to bring a myriad
of potential impacts across the western Great Plains.
- Sunday afternoon into evening is the best forecast time frame
for severe storms, especially east of Highway 283 corridor
- Very strong winds with gusts 50+ mph both ahead the front
Sunday and behind the front Sunday Night
- At least light accumulating snow mainly across far western
Kansas late Sunday Night into Monday, depending on final upper
low track.
&&
.SHORT TERM /THROUGH THURSDAY/...
Issued at 257 PM CDT Wed Mar 20 2024
A cold front pushed south across southwest Kansas this morning,
reaching far northwest Oklahoma early in the afternoon.
Unsurprisingly, surface winds from the east-northeast were a touch
stronger than most guidance (roughly 90-95th percentile of the NBM
membership). Surface winds will gradually decrease through sunset to
10 mph or less. Much of the night, winds will be light, however just
off the surface, the winds will be veering around to the southeast,
and this will draw up come low level moisture yielding increasing
stratus cloud by daybreak, especially the southwestern two-thirds of
the DDC CWA. Temperature forecast for Thursday hedged toward lower
guidance (closer to 25th percentile NBM) given anticipated more
cloud cover. If clouds hold on even longer, it will be difficult for
most locations to reach even the lower 60s for afternoon highs. Any
POPs will be confined to just the Oklahoma line (Red Hills region)
late tonight tied to strongest forcing for ascent as upper level low
will track well to our south across West Texas into the Red River
Valley.
On Thursday Night, surface winds will remain fairly light ahead of
the next cold front, although residual moisture is expected to
prevent temperatures to fall into the 30s except the far western
areas near Colorado line -- especially where low stratus hangs on or
redevelops.
&&
.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
Issued at 257 PM CDT Wed Mar 20 2024
Significant pattern change toward more active weather likely late
weekend into early next week including severe weather chances, very
strong winds, much colder temperatures, and even some snow potential.
Before we get to the big storm system, on Friday we will see a
fairly strong cold frontal passage, but we will only see a small
part of the upstream cold airmass that awaits. This is due to the
fact that immediately after frontal passage, large scale low
pressure will begin developing across Wyoming, Utah, and Colorado
ahead of the big late weekend storm. Winds will quickly become
southerly in response on Saturday.
Initially, early in the weekend, low level moisture will be confined
to southeastern Texas -- well displaced from southwest Kansas. The
south-southeast winds will eventually tap into the eastern Texas
moisture, most likely by Saturday Night. The moisture will
definitely come back north in to Kansas, but how far west this
moisture reaches is very much in question. A slower and deeper low
in the Southwest will mean a longer duration of south-southeast
winds before they veer out, and this will help bring 50+ surface as
far west as the U283 corridor Sunday afternoon.
The big three deterministic models show a highly impressive sub-
985mb surface low. This is significant, implying a very dynamic jet
approaching western Kansas. This will no doubt manifest as vigorous
convective and non-convective precipitation across a large portion
of the Central CONUS, including western Kansas -- whether it be cold
sector, warm sector, or both. Which ever Medium Range severe
weather forecasting metric is used (Ensemble system probabilistic
data, Analog-based guidance [i.e. CIPS], or Machine-learning
probabilistic prediction systems [i.e. CSU], there is enough
confidence in severe thunderstorm risk close enough or including
portions of southwest, south central, and west-central Kansas to
begin ramping up some of the messaging of severe storms for Sunday
Afternoon/Sunday Night. The Storm Prediction Center Day 5 forecast
is in agreement with this as they have a 15% probabilistic outlook
as far north as a Dodge City to Great Bend line in Kansas. This is
certainly something we will be keeping our eye on.
Regardless of severe weather risk, we will almost certainly see very
strong winds both ahead of and behind the front and the official
forecast will lean heavily on the high side of NBM guidance (heavy
weight or even straight 90th percentile wind speeds) and this may
push winds into High Wind category. If the low travels farther north
and is faster on Sunday, then we will need to bring in critical fire
weather concerns west of the dryline. This is a fairly low
confidence forecast, however.
Then there is the winter side. At this time, the way the mid level
cyclone is currently forecast to track, severe winter impacts are
likely to remain well north of our southwest Kansas region up across
Nebraska into the Dakotas and especially Minnesota. That said, the
mid-latitude cyclone may become so far-reaching, that backside
winter impacts may also include portions of southwest and west-
central Kansas, and we do have some mention of snow in the forecast
late Sunday Night into Monday. Very cold temperatures will follow
the cyclone for at least a day or two including one or two mornings
of lows well down into the lower 20s if not teens in some areas of
west central Kansas. Latest NBM has a low of 17 at Syracuse and
Scott City...21 at Dodge City Tuesday morning 26th.
&&
.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 538 PM CDT Wed Mar 20 2024
A stationary boundary in the higher terrain will be the focus
for weak surface wind and moisture convergence resulting in a
higher chance for stratus development in the vicinity of
Liberal. The NAM model soundings show a persistently saturated
layer from around 850 mb down to 950 mb through at least noon.
The HRRR model is a lot more shallow however, with a quicker
scattering out signal. In either case, the Liberal and GCK are
the most likely to see the IFR-LIFR category ceilings –
onsetting anytime after 4 am.
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...Umscheid
LONG TERM...Umscheid
AVIATION...Russell
Area Forecast Discussion
National Weather Service Des Moines IA
642 PM CDT Wed Mar 20 2024
...Updated for the 00z Aviation Discussion...
.KEY MESSAGES...
- Lingering elevated fire weather concerns this afternoon
- Flurries possible Thursday morning, otherwise dry and a bit warmer
Thursday
-Rain/Wintry Mix expected late Thursday into Friday, snow north
-A larger system bringing additional chances for rain/mix/snow
Saturday into early next week
&&
.DISCUSSION...
Issued at 259 PM CDT Wed Mar 20 2024
Fairly quiet though quite dry across Iowa this afternoon, as
dewpoints continue to fall through the single digits and even a few
degrees below zero. These dry conditions are thanks to a rather
large area of high pressure draped across the Upper Midwest, with
cold air advection bringing breezy winds out of the north/northwest
gusting upwards of 25-30 mph, especially across northern Iowa.
Deeper mixing achieved with mainly clear skies through the rest
of the afternoon will likely bring continued breezy conditions,
before mid-level clouds fill into the state out of the
northwest this evening. The aforementioned cold air advection
has brought in much colder temperatures compared to conditions
yesterday, with temperatures 20-25 degrees cooler in the upper
30s to mid 40s expected yet this afternoon. These temperatures
should continue to help limit fire weather concerns, though
remaining elevated for the drier and lingering breezy
conditions. As the high pressure slowly lifts back northward,
winds are expected to shift more southeasterly as low level flow
turns more westerly, bringing warmer air into the region. As a
weak wave pushes through the area Thursday morning, weak lift
paired with moisture in the mid levels may allow for some
flurries to occur at times, though the main drawback would be
continued dry air near the surface that would limit much if
anything from reaching the ground.
Active weather will be the main focus into the rest of the week,
with the first system of note developing over western Nebraska
Thursday afternoon within a passing shortwave, tracking
eastward towards Iowa by late evening into Friday. With this,
increasing frontogenesis is expected, which is quite strong.
Further analysis into model soundings indicates the strong lift
through the midlevels, along with a notable warm layer in the
low levels. Among model members, this warm layer is generally
warmer per NAM and GFS guidance, versus a generally less
pronounced warm layer over portions of north-central Iowa. With
near surface dry air present to start, precipitation onset looks
to be delayed, as saturation of the column does not look to
occur until around or after midnight into Friday. Overall
expecting to see precipitation in the form of rain further into
central and southern Iowa along with some thunder, while
northern Iowa continues to see a better chance for a wintery mix
to snow. As the strongest forcing continues to trend further
north into Minnesota, cannot rule out snow accumulations around
1-2 inches over northern Iowa, along with minor ice
accumulations. Rain totals further south generally look to be
around or under a quarter inch with this system. Something of
note that models such as the RAP and NAM have hinted at is some
banding snow potential early on Friday morning, though location
and track continues to hold uncertainty so will have to keep an
eye on this.
As the shortwave weakens through the day Friday as it pushes
east out of the state, conditions are expected to dry out as
upper level ridging moves in and high pressure drops back into
the region. Highs are expected to reach into the upper 30s to
low 50s Friday. As lee cyclogenesis occurs within a larger scale
trough and develops a deep surface low into the weekend, this
will bring additional precipitation into the region. Model
guidance depicts deep moisture return out of the Gulf of Mexico
and increasing southerly flow pushing into the region ahead of
the circulating low pressure system, which will bring warmer
temperatures gradually through the weekend and into the early
next week, with highs in the 50s and nearing 60 degrees by
Monday. As the initial wave of precipitation looks to lift
through the state Saturday, dry air may again be an issue to
start before the richer moisture further south makes its way
into the region. With this, the best chances for precipitation
look to Sunday and Monday, lingering though at least a portion
of Tuesday. Could again see a rain/snow mix through the weekend,
with better chances for snow looking to occur after the colder
air settles in with arriving northwesterly flow Monday into
Tuesday. Still much uncertainty in the evolution and exact
tracking of this system, so will be keeping a very close eye on
this. Please stay tuned for more details as they become more
clear.
&&
.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 639 PM CDT Wed Mar 20 2024
VFR conditions to prevail through the period with midlevel
clouds covering the state overnight. -SN possible across the
northern half of the state with highest confidence at KFOD at
this time. Will continue to monitor trends. Winds become
southeasterly in the morning hours and not become gusty until
after the TAF period.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
DISCUSSION...Bury
AVIATION...Jimenez
Area Forecast Discussion
National Weather Service Flagstaff AZ
430 PM MST Wed Mar 20 2024
.SYNOPSIS...As a lingering storm system gradually departs the
region, shower and thunderstorm chances become more limited
today. Warmer and drier weather then settles in for the end of the
week. Increasing winds this weekend with unsettled weather returns
for the start of next week.
&&
.DISCUSSION...Today and Thursday...Low pressure moves eastward
into New Mexico today, and moisture begins to decreases across
Arizona. However, enough moisture combined with daytime heating
should allow for some isolated showers and thunderstorms to
develop later this morning into the afternoon. These storms look
to initially develop over the higher terrain (namely the Mogollon
Rim, Chuska Mountains, Santa Maria, and Bradshaw Mountains) then
move off the terrain through the afternoon. RAP guidance this
morning shows that the greatest instability this afternoon (~500
J/Kg) should reside along and south of the Mogollon Rim, coupled
with a 25-35 kt shear gradient over the eastern Rim and White
Mountains. Thus, a stronger storm or two will be possible,
producing small hail and gusty winds.
Some very isolated shower look possible again thursday afternoon,
however with drier air and increasing subsidence, the vast majority
of the area will be dry. Virga (if anything) looks to be most likely
where any moisture remains.
Friday and Saturday...Heights maximizes over Arizona on Friday as
the ridge becomes centered over the state. Warm and dry conditions
prevail as a result, with afternoon high temperatures peaking in the
70s F across the lower elevations and mid-50s F to mid-60s F over
the High Country.
Slightly cooler temperatures and windier conditions set in to start
off the weekend as the next storm system approaches. Model soundings
show decent mixing, which should allow for some of the stronger
winds around 700-650 mb to mix down. Thus, gusts of 30-40 kts
look probable during the afternoon on Saturday.
Sunday through Tuesday...Guidance continues to show a broad trough
moving into the western US later in the weekend into next week.
Between much of the EPS, CMCE, and GEFS members, QPF amounts look to
be on the lighter side, with generally under a half an inch to three
quarters of an inch expected. Enough cold air does look to make into
the region to keep snow levels down to around 5500-6500 feet.
However, given low QPF amounts and marginal daytime temperatures,
significant snowfall doesn`t appear likely at this time. A lot
can change though, so stay tuned!
&&
.AVIATION...Thursday 21/00Z through Friday 22/00Z...Spotty MVFR due
to convective showers will end by 02Z-04Z, otherwise VFR through the
period. ISOLD convective possible along the eastern Mogollon Rim
and White Mtns Thursday afternoon. Sfc winds generally light.
OUTLOOK...Friday 22/00Z through Sunday 24/00Z...VFR conditions with
strengthening daytime southwest winds through the period.
&&
.FIRE WEATHER...Thursday and Friday...Isolated showers will be
possible Thursday afternoon over the Mogollon Rim, White Mountains
and Kaibab Plateau. Dry on Friday. Otherwise, look for warming
temperatures with west-northwest winds of 5-15 mph on Thursday
shifting to southwest on Friday.
Saturday through Monday...A storm system will approach on Saturday
then move across the area on Sunday and Monday. As a result, gusty
southwest winds at 15-25 mph will develop on Saturday shifting to
west on Sunday. Winds becoming lighter on Monday. The storm will
deliver good chances for showers on Sunday which will linger into
Monday. Look for much cooler daytime temperatures.
&&
.FGZ WATCHES/WARNINGS/ADVISORIES...None.
&&
$$
PUBLIC...Humphreys
AVIATION...Peterson
FIRE WEATHER...McCollum
For Northern Arizona weather information visit
weather.gov/flagstaff
Area Forecast Discussion
National Weather Service Morristown TN
930 PM EDT Wed Mar 20 2024
...New UPDATE...
.UPDATE...
Issued at 914 PM EDT Wed Mar 20 2024
A weak cold front appears to be near the southern and eastern
edges of the CWA. Winds are becoming more northerly and some clouds
have moved into the region. Clouds are expected to clear out
shortly after midnight. Guidance is trending warmer for lows
tomorrow morning, so temps were bumped up slightly for tonight
during the evening update. Otherwise, no changes.
&&
.SHORT TERM...
(This evening through Thursday)
Issued at 247 PM EDT Wed Mar 20 2024
Key Messages:
1. Slightly cooler temperatures spread into the area following a dry
frontal passage tonight.
2. Another afternoon of low relative humidities expected Thursday,
however, light winds limit fire weather concerns.
Discussion:
Recent surface observations depict relative humidity has largely
fallen into the lower 30s/upper 20s across the forecast area. This
has been accompanied by breezy conditions, mostly in extreme
northeast Tennessee and southwest Virginia, where some gusts between
20-25kts have been observed. Overall, the Fire Danger Statement has
worked quite well. That will come to an end at 00Z tonight.
A moisture starved cold front will pass through the region
overnight. Favorable radiational cooling conditions and cold air
advection will allow for temperatures to fall sharply. SW Virginia
and portions of NE Tennessee, including the northern Cumberland
Plateau, will see temperatures reach at or a few degrees below
freezing. As the growing season has not been activated yet, no
frost/freeze products will be issued.
Another quiet day tomorrow afternoon where the main focus will be
on continued low afternoon RHs. Some high-resolution guidance
such as the HRRR and ARW suggest some places may actually fall
into the teens(mainly along & north of I-81 and along the northern
Plateau). Otherwise, locations along and north of I-40 are most
likely to see RHs fall into the 20s once again. On a positive
note, the pressure gradient will have diminished and light winds
will limit fire weather concerns.
&&
.LONG TERM...
(Thursday night through next Wednesday)
Issued at 247 PM EDT Wed Mar 20 2024
Key Messages:
1. Unsettled long term period with several systems moving through,
each brining chances of precipitation across the area. No threat of
thunderstorms as of now.
2. Near Wind Advisory criteria on Friday and Friday night across the
east TN mountains and foothills due to downsloping winds.
Discussion:
We begin the forecast dry on Thursday night but that is short-lived
as a southern stream shortwave approaches from the west. Precip will
begin to spread into the area by Friday afternoon from southwest to
northeast. Precip may not begin across northeast TN and southwest VA
until Friday evening. As the low pressure center approaches, the
pressure gradient will tighten due to high pressure anchored off the
east coast and the 850 mb winds will strengthen. This will bring
breezy winds across the higher terrain of the east TN, southwest NC,
and southwest VA mountains late Friday morning through late Friday
night. Winds will also be gusty across the foothills of the east TN
mountains due to downsloping winds. As of now, it looks like max
wind gusts will stay near to just below Wind Advisory criteria for
most of these locations with gusts between 30 and 40 mph.
Additionally, lesser precip amounts are expected along the foothills
of the east TN mountains due to the downsloping winds, with
generally around half an inch of QPF.
Winds become less gusty Friday night into Saturday morning as the
center of the low passes to our east. This also coincides with when
POPs begin to decline, as we get on the backside of this system.
Areas along and west of I-75 should be mostly precip free by
Saturday morning. Areas east of I-75 will take longer to clear out,
especially along the east TN mountains and foothills, as well as
southwest VA. Precip may linger across these areas through mid
afternoon Saturday.
Afterwards, high pressure begins to build into the region and will
remain through Monday. Expect near to above normal temperatures
during this time. Monday night into Tuesday a cold front approaches
from the west with a deep upper low near Minnesota. As of now,
timing appears to be Monday night into Tuesday morning but the ECMWF
is notably slower with a later arrival time of Tuesday afternoon.
Nonetheless, expect widespread precipitation with this system,
affecting most of if not all areas. Models disagree thereafter with
what happens with the cold front. Because of a blocking patter to
our east in the Atlantic, the front could hang up across our area.
This would mean showers would persists into Wednesday. An additional
shortwave also looks to move in during this timeframe which would
further enhance POPs across the area. So while timing is still up in
the air it appears the Tuesday through Wednesday timeframe could be
quite unsettled. As of now, ensembles are showing all the
instability remaining well to our south with this system, so no
threat of storms at this time.
&&
.AVIATION...
(00Z TAFS)
Issued at 728 PM EDT Wed Mar 20 2024
Mid level clouds will continue near TRI for most of the night. VFR
conditions are expected across the region. Winds will become more
northerly as a weak cold front moves through this evening.
Tomorrow will be mostly sunny with light northeasterly winds.
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 44 69 49 63 / 0 0 0 70
Knoxville McGhee Tyson Airport, TN 39 64 43 66 / 0 0 0 50
Oak Ridge, TN 38 65 43 66 / 0 0 0 50
Tri Cities Airport, TN 32 59 38 63 / 0 0 0 40
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...NONE.
VA...NONE.
&&
$$
SHORT TERM...KRS
AVIATION...McD