Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/28/18
AREA FORECAST DISCUSSION
National Weather Service Kansas City/Pleasant Hill MO
630 PM CST Tue Feb 27 2018
.Discussion...
Issued at 253 PM CST TUE FEB 27 2018
Large-scale upper low seen very well on water vapor imagery this
afternoon, with strong southwest winds allowing for ample warm air
advection further downstream across the Nation`s midsection. 70
degrees is currently being reported at MCI, the warmest
temperature since December 4th! Meanwhile, cloud cover associated
with shower activity across the Southern Plains is starting to
lift north this afternoon, but fortunately not in time to prevent
an otherwise stealer day temperature-wise across the lower
Missouri Valley. Heading into tonight, expect cloud cover to
increase, with showers and isolated storms gradually lifting north
with time from southern Missouri. Quick look at several BUFKIT
soundings reveals a few hundred joules of elevated CAPE rooted
above the 850-hPa layer, so a few claps of thunder and flashes of
lightning (especially south and east of KC) will be possible
through the late evening and overnight hours. Latest high-res
solutions to include the HRRR and NAMNest suggest precip will lift
up towards the I-70 corridor before quickly shifting east as main
cold front starts to sink south with time. As a result, northward
extent of overnight precip remains in question right now,
especially for northwest Missouri with these locations standing a
lower chance of seeing much rainfall. In any event, limited
instability and overall lack of forcing in general will curtail
the severe weather threat from any convection that does impact the
area.
Shifting to tomorrow, available guidance suggests low clouds will
hang around for a good portion of the morning and possibly into
the afternoon hours, which should limit the diurnal heating cycle
and instability development. Despite this, models still indicate
a narrow sliver of instability will develop primarily east of
Route 65 and south of Route 50 by late afternoon, which may be
enough to support thunderstorm development Wednesday evening out
in advance of the main cold front expected to move through
tomorrow night. Instability will again be low so widespread severe
weather is not expected at this time. Following FROPA,
deformation band precip will overspread the area early Thursday
which may lead to a wintry mix, especially north of KC. For now
however, major impacts are not expected.
Beyond this, high pressure will build into the region on Thursday
with winds gradually decreasing through the afternoon. Southerly
winds will quickly return to the region by late week which should
lead to another warm up heading into the weekend with upper 50s
possible both Saturday and Sunday. Next chance for precip set to
arrive Sunday night/early Monday when the next cold front is
slotted to move into the region. Severe chances look low at this
point due to timing (early morning), but trends will be monitored.
&&
.Aviation...(For the 00Z TAFS through 00Z Wednesday Evening)
Issued at 605 PM CST TUE FEB 27 2018
Clouds have been steadily building into the area and are expected
to continue to thicken and lower throughout the evening.
Overnight, look for low-level stratus to build in, dropping
ceilings, and most likely visbys along with it. Showers are
anticipated to increase in coverage through the period, with some
thunderstorms in the area possible tomorrow afternoon. Generally
southerly winds tonight will become variable as a front
approaches, transitioning to out of the north toward the end of
the TAF period.
&&
.EAX WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
MO...NONE.
&&
$$
Discussion...32
Aviation...lg
Area Forecast Discussion
National Weather Service Huntsville AL
901 PM CST Tue Feb 27 2018
.NEAR TERM...(Tonight)
Issued at 900 PM CST Tue Feb 27 2018
Showers have moved towards the area a bit quicker than originally
forecast and are currently located across northern MS. However, there
is still a good deal of dry air to overcome, which is very apparent
in the 00z BMX/OHX soundings and surface obs. Temps have remained on
the warmer side with winds staying up and clouds moving in. Think
that as rain begins to fall into the dry layer we`ll see some
evaporative cooling and temps may tumble to the low to mid 50s based
on current dewpoint depressions. They should remain there for much of
night before gradually warming towards sunrise as winds become more
southerly and the warm front moves over the area. Models with the
exception of the 01z HRRR appear to be about 3-4 hours too slow with
the onset but they all do narrow in on the warm front stalling just
across border in TN. The result would be a gradient in precip with
the overrunning showers continuing in TN and more isolated showers
south of the front. Lapse rates and sounding profiles don`t support
thunderstorm potential until near the warm front and have gradually
introduced those into the forecast. PWATs near the front jump up to
around 1.5 inches and could see some brief heavy downpours early
Wednesday morning.
Now any minor changes in the frontal position could be a longer
duration of showers Wednesday morning a quicker end before the next
batch arrives later in the day. Something we`ll be keeping an eye on.
The rest of the forecast is in good shape.
.SHORT TERM...(Wednesday through Thursday)
Issued at 303 PM CST Tue Feb 27 2018
A very wet period continues Wednesday and Thursday with the
potential for flash and areal flooding initially on Wednesday and
eventually river flooding Thursday into the weekend. The
aforementioned boundary is progged to stall across or just north of
the WFO HUN forecast area. Generally, the ECMWF, GFS, Canadian, and
some of the newer mesoscale guidance is trending this way. This
scenario would result in a widespread heavy rainfall event of 2 to 4
inches, with higher amounts of 5 inches possible. The Canadian and
ECMWF have trended even higher in their 12z runs, showing a few
localized amounts up to 6" in far Northwest Alabama.
The one outlier is the NAM which stalls the boundary further to the
north across portions of Middle Tennessee. Should this play out,
rainfall totals (and thus the flooding threat) will be much less.
However, most trends (as mentioned) have honed in on this boundary
stalling roughly along the Alabama/Tennessee state border and the
heaviest rainfall occurring across Northwest Alabama and areas along
and north of the Tennessee River. There may well be a sharp
precipitation gradient, with portions of Marshall, Cullman, and
DeKalb Counties likely seeing less rainfall (perhaps closer to 1.5 to
2"). Regardless, things are trending toward a widespread flooding
event across much of the region.
As one might imagine, parameters are very favorable for flooding and
heavy rainfall as these showers and storms will be efficient rain
producers. There will be a deep warm cloud layer, with some modest
CAPE favorable for some organized, deeper convection at times.
Additionally, PWATs will increase to around 1.5" Wednesday
afternoon/night and into Thursday morning, around 300% above the
norm. A low-level jet will enhance lift and shower/storm coverage
during the Wednesday evening/night and a warm front will help to
focus this activity, resulting in training. The best window (as
alluded to earlier) will be Wednesday afternoon/evening through early
Thursday morning in response to the low-level jet feature. A cold
front will sweep across the region on Thursday, bringing an end to
the precipitation from west to east by the afternoon. Even after the
flash/areal flood threat has ended, river flooding will likely be an
issue well into the weekend. In short, we`ll be dealing with these
hydro issues (potentially) for awhile.
.LONG TERM...(Thursday night through Monday)
Issued at 303 PM CST Tue Feb 27 2018
The large upper low that is poised to bring heavy rainfall to the
Tennessee Valley Wednesday/Thursday will slowly exit off the
northeast US coastal waters Friday into Saturday. At the same time
another strong Pacific system will be coming onshore across the
northwest corner of the United States. Between these two notable
systems, a rather high amplitude ridge will be building across the
nation`s midsection. This feature will bring dry weather, generally
clear skies and rather large diurnal temperature ranges in the Day
3-5 time period. Will trend toward the higher end of the guidance
envelope for max temperatures during this period. Morning
temperatures could be rather chilly (well relative to recent weeks)
with patchy frost possible on Saturday morning.
The ridge will begin to break down/slide east on Monday as the
aforementioned west coast trough advances into the Plains. This will
help drag a frontal system toward the Tennessee Valley. At this time,
the front looks to be rather fast moving with a narrow window for
rainfall from late Monday through early Tuesday. Low level moisture
return with this system looks very meager so despite adequate upper
level support expect primary a non convective rain event. The 12z
guidance supports a faster clearing trend behind this system on
Tuesday and will trend this direction with the afternoon package.
However, the current forecast may even be on the slow side if this
trend continues to hold with most of the day Tuesday being rain
free.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 520 PM CST Tue Feb 27 2018
VFR conditions will continue through the evening hours before
gradually dropping towards MVFR as showers spread into the area.
Some lingering dry air may help to limit the onset of the showers and
low clouds for an hour or so but expect cigs around 5,000ft
initially. Then down to as low as 1,000-1,500ft by 12z Wednesday. An
embedded thunderstorm is possible after midnight but confidence is
too low to add these to the current TAF package. Could see vsbys drop
down to 1SM at times under the heaviest showers, otherwise vsbys
should stay around 3SM.
Winds become gusty out of the S/SE during the day Wednesday with
gusts of 15-20kts possible at times. The frontal boundary bringing
these showers may stall either over the area or just to the north and
result in continued moderate to possibly heavy rainfall through much
of Wednesday and into Thursday.
&&
.HYDROLOGY...
Issued at 900 PM CST Tue Feb 27 2018
Various forecasts concerning some of the main streams that feed the
Tennessee River, namely the Big Nance, Flint and Paint Rock rivers
are forecast to rise in response to rainfall runoff during Wednesday
and Thursday. Rainfall totals across the Tennessee Valley into
Thursday should range between 2 and 4 inches, with locally higher
amounts possible. The water levels in these rivers will exceed
bankfull stage during Wednesday night and early Thursday, and likely
rise above flood stage during Thursday and Friday. Other area rivers
and streams will also rise to higher than normal levels. Water levels
on the Tennessee River will also rise late this week, with river
levels nearing or exceeding flood stage this weekend and possibly
continuing into early next week.
Those with activities in or near areas rivers and streams should
stay abreast of the latest forecasts from the National Weather
Service.
&&
.HUN WATCHES/WARNINGS/ADVISORIES...
AL...Flood Watch from 6 AM CST Wednesday through Thursday afternoon for
ALZ001>010-016.
TN...Flood Watch from 6 AM CST Wednesday through Thursday afternoon for
TNZ076-096-097.
&&
$$
NEAR TERM...Stumpf
SHORT TERM...AMP.24
LONG TERM...15
AVIATION...Stumpf
HYDROLOGY...RSB
For more information please visit our website
at weather.gov/huntsville.
Area Forecast Discussion
National Weather Service Louisville KY
955 PM EST Tue Feb 27 2018
.Forecast Update...
Issued at 955 PM EST Tue Feb 27 2018
SREF and RAP are verifying well, and the GFS is decent, with the
placement of the widespread rain over Arkansas and adjacent states
this evening. These models support a southward leaning of the
heaviest precipitation late tonight into Wednesday, with the highest
QPF amounts over Tennessee.
However, they also support a lesser, secondary maximum spreading
from southern Indiana into northern Kentucky as isentropic lift and
column moisture increase late tonight into Wednesday. 6hr FFG
numbers are up around two inches and OHRFC forecasts don`t show much
response on the rivers from the expected rainfall. Right now it
looks like amounts from southern Indiana into northern Kentucky
Wednesday morning look to be on the order of one-half to two-thirds
of an inch. Thunder looks unlikely until perhaps a few rumbles
Wednesday afternoon and evening.
So, given this and after chatting with IND, will continue the
current forecast without a headline north of the Flood Watch already
out for southern Kentucky. However, will issue an SPS since we could
still see some minor ponding in poor drainage areas, and the rain
will be coming through during the morning rush.
QPF numbers are actually not very impressive in southern Kentucky
through Wednesday evening, but there is a large mass of rain taking
shape upstream in area of strong moisture transport and 850mb theta-
e ridging. There is a chance that heavier precipitation amounts
could fall both north and south of the current watch, but after
talking with JKL and considering the QPF that is expected Wednesday
night, will keep the watch going.
&&
.Short Term...(Tonight through Wednesday night)
Issued at 245 PM EST Wed Feb 27 2018
...More Flooding Possible Wednesday and Thursday...
As of mid afternoon, clear skies and light winds were found across
the lower Ohio Valley thanks to surface high pressure centered over
the Commonwealth of Virginia. Nice late February temperatures as
readings have warmed into the lower to middle 60s.
The focus in the short term is on the rainfall forecast, totals, and
potential impacts starting late tonight through Thursday as a couple
rounds of showers and perhaps a thunderstorm cross through the
region.
First round of showers comes late tonight into early Wednesday on
the nose of increasing 850 mb moisture transport. This will bring in
higher PWATs on the order of 1 to 1.2 inches. While not record, it
is anomalously high for late February. Onset is expected to be after
midnight along/west of I-65 and closer to 4-6 am EST across the I-75
corridor. A look at the latest hi-res models show 2 possible areas
of concentrated rainfall. The first, across south central Indiana
and north central Kentucky, and the other across mid TN into
southern KY. Lighter precipitation may fall in between and it`s
possible there could be a gap across portions of central Kentucky.
Through early Wednesday afternoon, between 1/4 and 1/2 of an inch of
rain is expected broadly brushed across the area. There may be
locally higher amounts up to 3/4 or even 1 inch across the north and
south, but intense rainfall isn`t expected overnight into Wednesday
morning.
There will be a break in the rainfall Wednesday afternoon and
evening for pretty much the entire area. Then as the surface low
tracks to lower Michigan Wednesday night and Thursday, another round
of showers and perhaps a thunderstorm will be possible. PWATs climb
further to around 1.3 inches across much of central KY and southern
IN. The heaviest axis of rain is expected to fall across southern
Kentucky and along the KY/TN border. The 27.12z NAM continues to be
a heavier and more northerly outlier with a swath of heavier rain
impacting the extreme south-central KY counties. The last few frames
of the hi-res ARW and NMM also show a northern band across parts of
central Kentucky, so this is something will need to be watched.
Rainfall Wednesday night and Thursday will total 3/4 to 1 inch, so
total rainfall over the next 48-60 hours ranges from 1 to 1.5 inches
across southern Indiana and north central Kentucky to 1.5 to 2
inches across southern Kentucky.
With this in mind, and the antecedent conditions, high water, and
swollen rivers still in place, a Flood Watch will be issued for the
greatest risk area for flooding concerns across southern Kentucky
for Wednesday and Thursday. This might need to be expanded northward
into north central KY or even parts of southern IN if it looks like
higher rainfall amounts will fall but the watch was placed where the
greatest risk area is and confidence for flooding based on the
highest rainfall totals forecast.
&&
.Long Term...(Thursday through Tuesday)
Issued at 245 PM EST Tue Feb 27 2018
Upper level ridging through the weekend will provide near normal
temperatures for early March with highs in the 50s and lows in the
20s to 30s.
By early next week, a strong storm system will move from the central
Plains to the Upper Midwest, eventually pushing a cold front through
the lower Ohio Valley in the Monday night and Tuesday time frame.
Moisture return is not impressive (dewpoints only climb up to the
mid/upper 40s) and the current timing (overnight / early Tues)
really dampens instability potential, so stronger storms don`t look
likely at this point. Nonetheless, a blended model approach puts in
60-70 percent chances during this period.
&&
.Aviation...(00Z TAF Issuance)
Issued at 637 PM EST Tue Feb 27 2018
We can expect a mostly quiet night with increasing mid and high
clouds ahead of an approaching storm system. Borderline LLWS will
develop late as winds increase off the surface ahead of that system.
On Wednesday low pressure will cross Kansas and Missouri while a
couple of upper level disturbances eject eastward out of the
southern Plains. Showers will quickly become widespread early
Wednesday morning and continue into early afternoon before coverage
starts to decrease. Ceilings will go below VFR as the showers
establish themselves, and will fall into IFR in the afternoon and
evening as high 0-1km RH sweeps northward from the western Gulf of
Mexico.
&&
.Hydrology...
Updated at 230 PM EST Tue Feb 27 2018
Many of the area rivers have crested and are now receding but still
remain above flood stage. Rainfall amounts of 1 to 2 inches are
possible Wednesday through Thursday evening across the region. For a
complete listing with forecast hydrographs, please visit our website
at: https://water.weather.gov/ahps2/index.php?wfo=LMK
The forecast rainfall through Thursday is not expected to result in
any new river flooding. However, it will slow the fall on some
rivers and will likely result in minor rises on the flashier basins.
Smaller creeks, streams, and rivers will be most at risk along with
areal flooding of low lying areas. Many locations are still
recovering from the recent heavy rainfall and while 2 days of drying
helped, the soils remain very saturated and soft. With the
antecedent conditions, river flooding, and saturated soils, a Flood
Watch has been issued for parts of central Kentucky.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...Flood Watch from 7 AM EST /6 AM CST/ Wednesday through Thursday
evening for KYZ053-054-062>067-071>078-081-082.
&&
$$
Update...13
Short Term...ZT
Long Term...ZT
Aviation...13
Hydrology...ZT
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
612 PM CST Tue Feb 27 2018
.SHORT TERM...(This evening through Wednesday)
Issued at 210 PM CST Tue Feb 27 2018
A cold front moved into far southern Minnesota this afternoon,
with a weak surface low in south central Minnesota as of 2 pm.
Temperatures this afternoon, and the effect of the snowpack and
albedo, shows a sharp contrast along the Minnesota River Valley,
vs. the Twin Cities Metro area, and more forested areas of east
central Minnesota, and west central Wisconsin. Where the albedo is
much higher due to the terrain/lack of vegetation in west central
Minnesota, temperatures have only managed to rise into the low to
mid 30s. Where the albedo is lower, like the Metro area and more
trees in east central Minnesota, and west central Wisconsin,
temperatures were in the 40s. The deeper snowpack across southeast
Minnesota has also had a major impact on temperatures. Around
Rochester, Winona and La Crosse, temperatures have managed to rise
into the 50s this afternoon.
The forecast tonight is based on a weak upslope flow (northeast
winds) across southwest/west central Minnesota where fog/stratus
is likely to form. Elsewhere, patchy fog is likely, especially
considering the amount of melting this afternoon and the moist
boundary layer. Wednesday afternoon will have a weak short wave
moving across Minnesota by late in the day. Due to the weak short
wave, and the lack of phasing from the southern jet stream,
anything that develops will be light, and affect areas from south
central Minnesota, northeast to west central Wisconsin. Wednesday
afternoon temperatures will be cooler than today, but still above
normal for late February.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 230 PM CST Tue Feb 27 2018
The weak short wave will exit the Upper Midwest Wednesday night.
Some residual sprinkles, flurries or freezing drizzle is possible
along and east of this short wave, but most areas will remain dry.
The extended period can be characterized as mild and uneventful
through most of the upcoming weekend. This is mainly due to an
upper ridge building across the Plains, and Upper Midwest. Plus, a
strong and blocking ridge will remain centered across southern
Greenland.
Over the past several runs of both the EC/GFS, and their
ensembles, indicated that the upper ridge will hold longer across
the Upper Midwest for the first half of the weekend. Thus,
precipitation chances have been lowered, especially Saturday, and
most of Sunday. In addition, and due to the prolonged milder air
moving northward as the upper ridge holds, the chance of more rain
vs. snow is increasing for the onset of the precipitation Sunday.
Once the upper ridge finally begins to break down over the Upper
Midwest/Great Lakes region, does our weather begin to become more
unsettled. There remains differences with both the EC/GFS by early
next week on the strength of the storm system, but there is
enough consistence that the milder air will be replace with much
cooler conditions by Monday. The conflict between the mild air,
and the cooler air mass, a strong storm system will likely form.
It is too early to tell on how it will affect the Upper Midwest,
but anytime there is a significant change in the air mass, a major
storm is likely near the gradient. Please check back for further
updates on the potential of a winter storm early next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 612 PM CST Tue Feb 27 2018
Like last night, we will likely see patches of dense fog develop
in valleys and other low lying areas late tonight, though that
will be dependent on trends in mid level clouds. HRRR and other
high res models continue to highlight greatest fog potential out
along the SD/MN border, then down the upper MN River Valley.
Confidence in dense fog occurring at any of the terminals is
pretty low, so soft played the fog potential with some prevailing
MVFR vsbys. Question then for Wednesday turns to when does the
stratus move in. Majority of the guidance says it really starts
advancing NW out of IA/SE MN during the afternoon, so delayed
arrival of MVFR several hours from the 18z TAF to get the timing
in line with the LAV.
KMSP...Like this morning, we will likely see reduced visibilities
from 9z to 16z. For the most part, it will be a VFR haze, but we
could see an MVFR vis around sunrise. For stratus Wednesday, went
with a later LAV timing, though we could really see it set in at
any point during the day when looking forecast soundings.
/OUTLOOK FOR KMSP/
Thu...MVFR with -SN possible early. Wind NW 5-10 kts.
Fri...VFR. Winds SE 5-10 kts.
Sat...VFR. Winds SE 10-15 kts.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
&&
$$
SHORT TERM...JLT
LONG TERM...JLT
AVIATION...MPG
Area Forecast Discussion
National Weather Service Marquette MI
719 PM EST Tue Feb 27 2018
.SHORT TERM...(This evening through Wednesday)
Issued at 317 PM EST TUE FEB 27 2018
All the attention in the short term is on Fgen forced precip on the
N side of a surface trough axis nosing into the region. Models have
significantly increased QPF over the S-central to eastern U.P. and
have followed that trend in the forecast. Low-mid level temps will
be cooling dynamically as the precip develops, which will push the
rain/snow line farther south to southern Menominee County. Where
rain is expected, surface temps should be above freezing. Elsewhere,
0.5-1.0 inch of snow is forecast from Stephenson to Escanaba,
Manistique, and Newberry. There is a possibility for greater amounts
as the HRRR shows total QPF around 0.50 inches, but that seems
overdone and definitely on the high side of guidance. Did not issue
any headlines or SPSs given limited amounts.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 317 PM EST TUE FEB 27 2018
Overall, through the extended the weather looks to remain fairly
quiet across the Upper Great Lakes region. Zonal flow will break
down towards the end of the work week as a lead shortwave tracks
eastward across the central and eastern CONUS, allowing a deepening
low pressure system to track across the southern Great Lakes on
Thursday. Given the southern track of the system and models still
showing most, if not all of the precipitation remaining south of the
area, do not expect much if any precipitation to reach southern
portions of Upper Michigan. We could see some light wintry
precipitation off of Lake Superior as the system continues to move
over the eastern Great Lakes region on Friday, but with 850mb
temperatures being very marginal and high pressure quickly moving
into the region any precipitation should remain light.
For the up and coming weekend, we will be sandwiched in between two
systems with upper-level ridging slowly moving eastward across the
Upper Great Lakes region. As a result, high pressure will give way a
pleasant weekend with mild conditions and dry weather. Cloud cover
will be on the increase, along with winds, towards the end of the
weekend into early next week as deep, longwave trough slowly ejects
out across the Plains. This upper-level trough is progged to slowly
track across the Upper Great Lakes region through early next week
allowing for better chances for widespread precipitation and cooler
temperatures. Precipitation type as this system tracks across the
region will be highly dependent on the track of the system, which
models continue to diverge on. Temperatures following the system
will also depend on the strength and track of the system. If
temperatures are able to cool down enough aloft to support any lake
effect precipitation, it will depend highly on the ice coverage
over Lake Superior.
&&
.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1238 PM EST TUE FEB 27 2018
VFR conditions are expected at all TAF sites. However, there is
potential for lowered conditions at KSAW late this evening and early
tonight as an area of snow and showers passes just to the SE.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 317 PM EST TUE FEB 27 2018
Today through the end of the week, winds are expected to remain
below 25 knots.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...Titus
LONG TERM...Ritzman
AVIATION...Titus
MARINE...Titus
Area Forecast Discussion...UPDATED
National Weather Service Morristown TN
1008 PM EST Tue Feb 27 2018
.DISCUSSION...
The forecast appears on track this evening as rain spreading E-NE
across MS and western AL is expected to reach our area near or after
06Z. Regional 00Z raobs show a very dry layer between 850-700 mb that
precip aloft will have to saturate before measureable precip is
likely at the ground. The latest HRRR supports the onset timing
near or after 06Z. No changes are planned at this time.
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...Flood Watch from Wednesday afternoon through Thursday evening
for Cherokee-Clay.
TN...Flood Watch from Wednesday afternoon through Thursday evening
for Anderson-Bledsoe-Blount Smoky Mountains-Bradley-
Campbell-Claiborne-Cocke Smoky Mountains-East Polk-Grainger-
Hamblen-Hamilton-Jefferson-Knox-Loudon-Marion-McMinn-Meigs-
Morgan-NW Blount-North Sevier-Northwest Cocke-Northwest
Monroe-Rhea-Roane-Scott TN-Sequatchie-Sevier Smoky
Mountains-Southeast Monroe-Union-West Polk.
VA...None.
&&
$$
DGS
Area Forecast Discussion
National Weather Service Nashville TN
802 PM CST Tue Feb 27 2018
.UPDATE...
FOR EVENING DISCUSSION.
&&
.DISCUSSION...
Mostly mid and upper level cloudiness is on the increase across
the mid state this evening. A few breaks are noted in the Plateau
areas where temps are running a couple degrees below guidance.
Otw, we should see the increasing cloudiness trend continue. As
for the onset of the shower activity, so far the showers are
reaching the ground over northwest MS. Reflectivity returns are
well in advance of that. Latest Hrrr data suggests that measurable
rainfall will reach into our southwestern counties just after 11
pm. This seems reasonable. Thus, will opt to make no changes to
the current fcst which of course, ramps up pops after midnight.
Will keep an eye on those Plateau temps, although they should
begin to level off as well.
&&
.AVIATION...
00Z TAF DISCUSSION.
BNA/CKV/MQY/CSV...Previous forecast/forecast reasoning continues
to hold true for the vast majority of the upcoming terminal
forecast period. VFR conditions still look like they will continue
thru late tonight. A trend toward MVFR ceilings is still likely
after 28/10Z, as it continues to look like an area of shwrs will
move in from the southwest resulting in lower ceilings and
visibilities. Believe MVFR ceilings will persist also thru 28/24Z,
but vsbys could fall into IFR thresholds after 28/20Z. Enhancement
in sfc pressure gradient influences could result in sly sustained
winds generally around 10kts gusting to 14kts-18kts at times.
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
Flood Watch from Wednesday afternoon through Thursday morning
for Bedford-Cannon-Cheatham-Clay-Coffee-Cumberland-Davidson-De
Kalb-Dickson-Fentress-Giles-Grundy-Hickman-Houston-Humphreys-
Jackson-Lawrence-Lewis-Macon-Marshall-Maury-Montgomery-Overton-
Perry-Pickett-Putnam-Robertson-Rutherford-Smith-Stewart-Sumner-
Trousdale-Van Buren-Warren-Wayne-White-Williamson-Wilson.
&&
$$
DISCUSSION......21
AVIATION........31
Area Forecast Discussion
National Weather Service Pocatello ID
120 PM MST Tue Feb 27 2018
.SHORT TERM...Tonight through Friday. The latest satellite imagery
was showing a weak disturbance embedded in the NW flow digging
rapidly SE through the Canadian Rockies which will likely bring some
light snow to the ERN mountains tonight and to a lesser extent
Wednesday. Further upstream, the next stronger storm system was
noted advancing into the Gulf of Alaska and will push into the NW
coastal waters Wednesday night and then south along the Washington
and Oregon coast Thursday and Friday. As the low shifts south along
the coast, a very moist SW flow will impinge upon the CNTRL
mountains with moderate to heavy snow expected Thursday and Thursday
night. Hence, a Winter Storm Watch has been issued for the CNTRL
mountain zones during this time frame. By early Friday morning, a
frontal boundary and associated precipitation will spread east into
the Snake River Plain and ERN mountains. I fully anticipate
additional highlights for these ERN zones as the event continues to
take shape. Temperatures ramp up toward climatological norms ahead
of the low in deep southerly flow Thursday. The current forecast is
warmer than the GFS statistical guidance in this regard and may be
too cool yet. Temps should cool Friday behind the front and have
generally followed guidance here. Huston
.LONG TERM...Friday night through next Tuesday. Upper low will
dominate the PAC NW with unsettled weather expected through much of
Saturday and into Sunday. Models drive through a series of
shortwaves through the upper low over the weekend. Not yet enough
confidence to tie sensible weather to the individual waves, but
keeping PoPs tied to higher elevation through the extended periods.
ECMWF is the drier solution for Sunday evening through Tuesday. Both
GFS and ECMWF pull the upper low out of the region starting Sunday
while developing another upper low off the California coast by
Tuesday. Southeast Idaho will lie between systems, and under a
transient upper ridge heading into Tuesday. Hinsberger
&&
.AVIATION...GOES Snow/Fog RGB imagery is quite revealing today.
A large area of stratus is barreling across the Magic Valley and has
overcome KBYI as of 17Z. Ceilings are around 2000 ft, but may drop
below as seen upstream at KTWF and KJER. While one patch of stratus
clears KPIH around noon, this next one will show up around 20Z,
taking the terminal back to MVFR, possibly IFR. RAP soundings in
BUFKIT are starting to pick up on this low-level moisture. The same
field of stratus will likely hit KSUN as diurnal wind changes bring
that moisture up the Big Wood River Valley. A little less certainty
for KIDA and KDIJ though as models show mixed solutions to the
ceilings, particularly for KIDA in the overnight hours. Hinsberger
&&
.PIH WATCHES/WARNINGS/ADVISORIES...
Winter Storm Watch Thursday through Thursday night for IDZ018-031-
032.
&&
$$