Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/18/18
Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
422 PM AKDT Tue Jul 17 2018
.ANALYSIS AND UPPER LEVELS...
An upper long wave trough evident on water vapor is moving
southeast across Southcentral Alaska this afternoon. Showers have
started to develop over the Susitna Valley, Talkeetna Mountains,
and Copper River Basin. These areas will see some isolated
thunderstorms. Subsidence under a building upper ridge over the
eastern/northern Bering Sea is producing widespread stratus and
patchy fog across much of the Bering Sea and portions of the
Kuskokwim Dela and Bristol Bay. A weakening low center over the
southern Bering Sea and leading front, extending to the eastern
Aleutians is producing light rain, stratus, and fog across the
Aleutians.
&&
.MODEL DISCUSSION...
Models in the east are in generally good synoptic agreement.
However, there are some significant model differences which
develop with a front and weak low which moves to the western
Aleutians Wednesday and Thursday. Otherwise, fog and stratus will
be the main challenges out west and warming temps and drying
conditions in the east.
&&
.AVIATION...
PANC...VFR conditions and light winds will persist.
&&
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)...
(Tonight through Friday)
Showers and isolated thunderstorms have once again developed this
afternoon, as daytime heating has allowed some weak instability
to develop per the latest RAP analysis showing lifted indices in
the -1 to -4 range, with 100 to 400 J/kg of SBCAPE across the
Mat-Su Valleys, Copper River Basin, and Kenai Peninsula. The most
prominent storm was located west of the lower portions of the
Little Susitna River, with this storm having remained fairly
organized and likely producing some small hail. However, that`s
been about it thus far concerning any convection.
This convection has been aided by a second short-wave trough that
followed yesterday`s disturbance, with it brushing mainly the
northern and eastern portion of the area. This increased
cooling/ascent may allow for some uptick in precipitation coverage
over the next few hours, before precipitation diminishes
overnight as subsidence behind the departing wave takes hold.
Otherwise, the main weather feature will be a short-wave ridge of
high pressure building across Southcentral, with some difference
in the models regarding how strong of a ridge develops. The GFS
current forecasts 500 mb heights topping out near 576 dkm, where
as the ECMWF is more robust with these heights approaching 580
dkm. The subsequent difference shows up in the 850mb thermal
fields with temps in the 10 to 14 deg. C range. What this means
for us is our current forecast highs of the upper 60s to upper 70s
may need to be increased somewhat if the higher heights/warmer
850 mb temps verify in later model runs.
&&
.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3)...
Ridging will remain over southwest Alaska into Friday as its axis
slowly shifts east. This setup should keep rain away from the area
and allow for some breaks in the clouds. Tonight, fog will form
along the coast and advect into southwest Alaska from weak onshore
flow spreading through many coastal locations and some areas
further inland. The fog will then dissipate Wednesday morning.
&&
.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3)...
The low in the southern Bering will drift slowly to the southeast
moving across the eastern Aleutians tonight. It will bring more
rain to the islands in the area through much of Wednesday until it
tracks further into the North Pacific. However, southerly flow
for the Alaska Peninsula will bring continued rain for much of the
week. Further out west another system is moving towards the
western Aleutians. Its front will move in Wednesday and then
slowly push east through the rest of the week making it to the
central Aleutians Thursday night.
&&
.LONG TERM FORECAST (Days 3 through 7: Friday through Tuesday)...
The entirety of southern mainland Alaska will be under the
influence of broad upper level ridging on Friday, which will
support sunny skies and very warm temperatures, especially across
Southcentral. Near the coast, fog and low stratus will be a
concern during the overnight hours. With Southwest Alaska being on
the western side of the ridge, the southerly flow and troughing
out over the Bering will support more cloud cover, especially for
coastal locations.
On Saturday, the ridge axis slides eastward over the Copper River
Basin, allowing for more cloud cover and cooler temperatures to
move into nearly all of Southwest Alaska, while most of
Southcentral continues baking with very summer-like temperatures.
The exceptions will be Kodiak Island and the coastal areas
impacted by clouds and fog.
Sunday will be the transition day for Southcentral west of the
Talkeetna and Chugach Mountains. The ridge will continue moving
eastward into Canada, allowing for wet weather associated with an
advancing area of low pressure to move into all of Southwest
Alaska, Kodiak, and the southern Kenai Peninsula. For now it looks
like most areas from Kenai northward will remain dry, but
significant cloud cover should temper afternoon highs as compared
with previous days. The Copper Basin will remain very warm.
Monday and Tuesday now look to be significantly wetter as compared
with previous model runs for much of Southcentral, though rainfall
coverage will diminish as one goes eastward. The upper level low
responsible for the southerly push causing the wet weather will
move into the eastern Bering.
&&
.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...None.
&&
$$
SYNOPSIS AND MODEL DISCUSSION...RC
SOUTHCENTRAL ALASKA...PD
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...DK
LONG TERM...JW
Area Forecast Discussion
National Weather Service La Crosse WI
605 PM CDT Tue Jul 17 2018
.SHORT TERM...(This evening through Wednesday)
Issued at 313 PM CDT Tue Jul 17 2018
Main forecast concerns in the short-term are on the potential for
patchy fog tonight in some river valley locations.
Surface high pressure edges east of the region late tonight through
Wednesday as a trough approaches from the high plains. The high
will provide mainly dry and quiet weather across the area at least
through Wednesday. Mostly clear skies and light winds will set
the stage for patchy valley fog, mainly in river valleys. Winds
increase just above the surface through around 1500 feet tonight
which should limit any fog in the main channel of the Mississippi
River. The main fog concerns will be along tributary river valleys
to the Mississippi River. Clouds will gradually increase across
the region from west to east late in the day on Wednesday as the
trough edges into eastern South Dakota/Nebraska.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 313 PM CDT Tue Jul 17 2018
Main forecast concerns are on the potential for heavy rainfall
Wednesday night through Thursday.
The trough is expected to push into the Upper Mississippi River
Valley on Thursday with surface low pressure deepening. Moisture
will be pumped northward into the area ahead of this low with
precipitable water values increasing to around 1.8 inches with
warm cloud depth of 3.5 km. Most of the CAPE will be confined to
areas south of Interstate 90, potentially only portions of
northeast Iowa and far southwest Wisconsin. This will limit the
potential for any stronger storms as far as wind and hail go, with
the primary threat being heavier rains. The bulk of the rain
should spread from west to east across the area after 12Z Thursday
with rain then persisting through much of the day, with scattered
embedded thunderstorms. Any storms could produce locally heavy
rainfall in addition to the ongoing rains. Some differences noted
in the forecast models on the low track, especially with respect
to the 12Z NAM, which takes the low southeast into northern
Illinois. This is the only model doing this at this time so
treating it as an outlier. The ECMWF, GFS, and Canadian take the
low into eastern/northeast Wisconsin Thursday night into Friday
then stalls. The low then sits over this area into Saturday, and
then the big question is how far west will rain showers occur. The
showers could continue into Saturday for areas along and east of
the Mississippi River. High pressure should then finally build in
Saturday night into Sunday, but with the cutoff low in the area,
there is the potential for rain showers to linger, especially over
central Wisconsin. By the time the rain ends, totals of 1.5 to 2
inches are expected. The widespread cloud cover and rain over the
region on Thursday will result in cooler high temperatures in the
upper 60s to lower 70s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 605 PM CDT Tue Jul 17 2018
Quiet VFR conditions expected through Wednesday afternoon. An
area of high pressure centered over Lake Superior will remain
nearly stationary and keep skies clear with light east to
southeast winds. Some concern for valley fog overnight with the
light winds. Forecast soundings from the 17.21Z RAP would suggest
it will be too dry tonight for fog to form as it does not show
saturation occurring at the surface. However the 17.18Z NAM
forecast soundings would be supportive of valley fog with a
visibility reduction at KLSE. For now, will maintain continuity
with the previous forecast and not include any fog at KLSE but
will monitor trends through the evening for possible inclusion
with later forecasts.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...Wetenkamp
LONG TERM...Wetenkamp
AVIATION...04
Area Forecast Discussion
National Weather Service Birmingham AL
717 PM CDT Tue Jul 17 2018
.UPDATE...
Evening Update and 00Z Aviation.
&&
.SHORT TERM...
Summer time cold front still in central Tennessee with surface dew
points even north of the front. It appears that the
outflow/prefrontal trough is near the I-20 corridor early this
evening. The latest RUC analysis has drier air entrenched over
much of Central Alabama, making storm development tough in most
places. The best moisture was southeast and west. The main upper
trough passes eastward into Wednesday, but some drier air filters
into the northern half of the area.
Adjusted pops slightly for the overnight hours. With a surface
trough, cold front, and several outflows, kept some mention of
storms developing at almost anytime. But there will be some
decrease in intensity with the loss of daytime heating.
75
Previous short-term discussion:Through Tonight.
Low clouds have kept temperatures down and diurnal thunderstorm
development at a minimum. The most significant low level boundary
appears to be across far north Alabama. Convection along this
boundary will likely sink southward this afternoon and evening,
and carried highest rain chances across the northern counties.
There is also a MCV over Southeast Arkansas tracking towards the
southeast. This feature may trigger some development across
southwest Alabama later tonight.
58/rose
58/rose
.LONG TERM...
Wednesday through Monday.
Northwest flow will remain in place aloft on Wednesday between a
mid-level trough extending from New England southward to the
northern Gulf, and a mid-level ridge extending from the Southern
Plains westward to the Pacific. A shortwave ridge will also be in
place over the Midwest, ahead of a shortwave trough over the
Northern Plains. Northerly low-level flow associated with high
pressure over the Great Lakes will allow the cool front to sink
southward towards the I-85 corridor afternoon. The ECMWF has
actually trended towards the other models in showing some drier
air mixing down across the northern counties during the afternoon.
This will set up a sharp moisture/PoP gradient with scattered to
numerous showers/storms across the south and rain-free conditions
across the north. Heavy rainfall/localized flooding will remain
possible in the high PWAT airmass along/south of I-85/Highway 80.
Dew points look to mix down into the 60s over at least some of the
northern counties, but temperatures will still hit 90 in most
spots. Isolated to scattered showers/storms will remain possible
Wednesday night in the far southern counties near the front. Any
MCS that develops over the Plains/Ozarks would likely remain well
to the west over the ArkLaMiss.
On Thursday, the Northern Plains shortwave/upper low will move
into MN while a lead shortwave will extend southward towards
northwest Alabama. A wave of low pressure more noticeable at 850mb
than at the surface will develop in the area of convection along
the stalled front along the Gulf Coast. The ECMWF has trended
slower with the development of this feature more in line with the
other models, and therefore the model consensus now indicates the
front will be a bit slower to lift back north as a warm front.
This will keep the drier air mass in place longer across the area.
PoPs were reduced and may be reduced further in future updates in
north-central/interior portions of the area. Best rain chances
will be in the far southeast closest to the stalled front.
The GFS and ECMWF remain in some disagreement for Friday. The
ECMWF is quicker to lift out the wave of low pressure up the East
Coast and therefore has more moisture return compared to the GFS.
Will go with PoPs in the scattered category areawide. Any storms
that do develop Friday afternoon could be strong with 0-6 km bulk
shear values of 20-25 kts, dry air aloft, and increasing mid-
level lapse rates.
Troughing will continue to amplify over the eastern CONUS Friday
night into Saturday, as an unseasonably strong vertically stacked
low moves into the Great Lakes with a trailing cold front. An
area of unseasonably strong northwesterly mid and upper-level flow
will be located along its southern flank. Friday night, there will
be the potential for one more more MCSs to form along the front.
The best upper-level forcing will remain north of the area, but
Corfidi vectors would support some activity making it into our
northern counties. If an MCS or organized cluster is able to hold
together when it arrives Friday night, 0-6 km bulk shear values of
30-35 kts and strengthening mid-level lapse rates would be
supportive of the potential for it to be strong to severe.
However, confidence in the strength/track of any MCSs this far out
is too low to mention in the HWO at this time, especially given
the nocturnal timing.
The cold front will move into the area on Saturday. Unusually
strong (for late July) 0-6 km bulk shear values of 30-40 kts and
decent mid-level lapse rates would be supportive of a threat of
strong to severe storms assuming sufficient instability. Main wild
cards are outflow from the possible MCS Friday night and what
impact that could have on destabilization. Some drier air may move
in aloft which could limit storm coverage. Given the uncertainty
this far out, will not add a severe mention to the HWO to this
time, but one could be added in future updates if trends continue.
The potential main threat would be damaging winds.
A drier air mass looks to move into much of the area
Sunday/Monday as the trough remains over the eastern CONUS,
resulting in reduced rain chances, dependent on where the front
stalls and residual boundary layer moisture.
32/Davis
&&
.AVIATION...
00Z TAF Discussion.
Mentioned some convection to start off the period for a few hours
this evening, then mentioned only pops south on Wednesday.
Believe there will be patchy fog and some low clouds around the
area by daybreak, most likely south. Added MVFR vis mention north
and low cloud restrictions south. Direr air filters into the
region above the surface overnight, but a large inversion sets up
trapped moisture below it. Therefore, think there will be enough
moisture near saturation to mention these restrictions overnight.
How far the drier air axis moves on Wednesday will determine the
areas likely to experience showers and thunderstorms. At this
time, mention some activity at MGM/TOI by 16z.
75
&&
.FIRE WEATHER...
Above normal coverage of mainly afternoon and early evening
showers and thunderstorms is expected again today as a weak front
moves towards the area. Highest rain chances will become confined
to the southern counties Wednesday and Thursday as the front
stalls. Localized fog will be possible each morning where
rainfall occurs during the previous afternoon and evening. There
are no fire weather concerns.
58/rose
&&
.PRELIMINARY POINT TEMPS/POPS...
Gadsden 70 92 67 92 69 / 40 10 0 20 10
Anniston 72 92 69 92 70 / 40 10 0 20 10
Birmingham 74 92 71 92 72 / 40 10 0 20 10
Tuscaloosa 74 94 72 94 73 / 40 20 10 20 10
Calera 73 91 70 92 71 / 40 20 10 20 10
Auburn 73 90 71 90 71 / 40 50 20 30 20
Montgomery 74 92 73 93 73 / 40 60 30 30 10
Troy 74 90 72 92 72 / 40 70 40 50 20
&&
.BMX WATCHES/WARNINGS/ADVISORIES/...
None.
&&
$$
Area Forecast Discussion
National Weather Service Denver/Boulder CO
854 PM MDT Tue Jul 17 2018
.UPDATE...
Issued at 853 PM MDT Tue Jul 17 2018
Reduced PoPs most areas as the best forcing and convection has
moved to Washington and Lincoln Counties. The storms are moving
southeast and should move out of our CWA or weaken altogether
within the next 60-90 minutes. The SVR watch has been cancelled
for all of our counties as storm intensity has really waned over
the past hour. The HRRR tries to redevelop weak convection over
the central mountains east of the Continental Divide later this
evening but do not see a obvious (nor subtle for that matter)
reason why convection would redevelop there. ESRL/PSD Platteville
profiler showing the trough axis has already passed across the
I-25 corridor over the last couple hours, and GOES-16 WV and IR
trends underwhelming for significant upstream convection. Cannot
rule out a stray shower through midnight across the central
mountains and Palmer Divide, but feel the subsidence and
stabilization should end shower activity area wide around midnight
or so. Otherwise the forecast looks on track overnight through
Wednesday with no convection expected area-wide and day #34 of 90+
degF max temp at Denver.
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 400 PM MDT Tue Jul 17 2018
It`s looking like convection will be a mess through this evening.
A preliminary round of convection that started on the foothills
convergence zone looks like it will put out an organized wind
boundary that will move eastward. This is ahead of the still
slower lift from the jet streak which is now over northwestern
Colorado. This means the lift will be separated from the good
moisture and the developing convergence along the outflow
boundary. So, as usual around here, we won`t have one good focus.
A possible exception is the storm near Cheyenne which is the best
organized and is probably rolling through the greatest
instability. This still could drift toward a splitting
supercellular structure as it moves into both better instability
and a little better low level wind field, though it`s pretty
linear now. Mesoscale models have been trending away from the
strongly right-turning storm they had earlier, but this storm
still looks to be in a favorable position.
This leaves Denver and our other big cities in a hole, with
surrounding convection, but cooler and cloudy for the most part.
Still expecting scattered weaker convection, mainly north and
south of Denver, with a second batch coming over this evening tied
to the jet. But the severe risk for Denver is looking fairly low,
and the risk for more than minor street flooding as well.
Drying/clearing/subsidence will move in behind the jet streak
overnight, along with a bit more westerly flow. A little bit of
drying should result in much less convection, and over and west of
the mountains the low level moisture should mix out, almost
eliminating convection. There could be an isolated storm around
Park county, or near the eastern border late in the day, but the
odds are pretty low. Forecast temperatures are a little above
guidance, which has been good for our warm dry days. There will be
a little breeze in the mountains and low humidities, but not up to
Red Flag Criteria, and the recent rain has temporarily lowered
the fire danger in most areas anyway.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 400 PM MDT Tue Jul 17 2018
An upper level ridge centered over the Great Basin will progress
to the east bringing subsidence to the forecast area through
Thursday. This will continue the hot temperatures. GFS and NAM
indicate light QG ascent Thursday evening but there is very little
to no moisture present in model soundings so the grids will
remain dry.
Friday through the weekend there will be an increased chance for
late day showers and thunderstorms. Forecast soundings show
precipitable water (PW) values will reach 1.00 to 1.32 inches
Friday afternoon through the weekend.
Monday there will be a slight cool down as the ridge flattens.
Chances for showers and storms will continue with high PWs through
most of the day.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 853 PM MDT Tue Jul 17 2018
VFR conditions will prevail through Wednesday. The airmass for
the rest of this evening is becoming more stable with time.
Latest trends in radar/satellite show all showers weakening
upstream of the metro area terminals and forcing to the west
looks too weak to warrant further shower development. Thus, TAF
sites should remain dry the rest of this evening and into the
overnight hours. Active gust fronts are all well east of the TAF
sites and the strongest outflow boundary from early evening
convection is washing out north of KDEN. Can`t rule out an outflow
boundary from the convection across far E. Colorado overnight but
if one forms we should be able put it in the TAF with lead time.
No significant impacts to the terminals or approach/departure
gates on Wednesday with no convection expected across central and
northeast Colorado. Light north winds around 10 kts are expected
tomorrow after 17Z or so, then drainage winds after 03Z or so
Wednesday evening.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Schlatter
SHORT TERM...Gimmestad
LONG TERM...Sullivan
AVIATION...Schlatter
Area Forecast Discussion
National Weather Service Boston/Norton MA
944 PM EDT Tue Jul 17 2018
.SYNOPSIS...
Scattered showers and a few left over thunderstorms will come to
an end in most locations by midnight...but linger a bit longer
across southeast New England. Other than perhaps some lingering
showers early Wednesday across Cape Cod and Nantucket, dry
weather is anticipated the rest of the work week along with much
lower humidity including warm afternoons and cool nights.
Unsettled weather may return sometime Sunday into Monday along
with increasing humidity.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
10 pm update...
Line of widespread light rain with embedded heavier showers,
perhaps a rumble of thunder, continues SE ahead of a sweeping
cold front expected to push offshore of S New England towards
morning. Have toned down on thunder overnight prevailing as
isolated. With isolated thunderstorms, a mention of heavy rain.
Near-term high res guidance, especially HRRR and HRRR-TLE, is
doing a decent job with handling trends.
Low clouds, patchy fog likely to be an issue along the S/SE
coast towards morning with moist SW flow as nocturnal cooling
proceeds. Soupy conditions prevailed, should stay fairly mild
overnight with lows around 70.
However, scouring dry air NW as noted in observations and within
RAP/HRRR models RH fields through the column. Expect improving
conditions across the interior overnight. Yet, with partial
clearing, falling temperatures, light winds behind the front
and antecedent rains, likely to be contending with patchy
shallow ground fog for interior locales. Dry air advection will
be proceeding which should limit the widespread nature, but
wouldn`t be surprised to see lower valley issues per cold air
drainage of a very moist airmass immediately above the damp
ground. Locally dense in spots, around 1 mile possible.
With cold frontal passage, dewpoint discontinuity, likely will
see with further progression into the tropical, moist air a
brief burst of NW flow. By morning, locations across the S-coast,
Cape and Islands may see gusts up around 20 mph with cold frontal
passage.
&&
.SHORT TERM /6 AM WEDNESDAY THROUGH 6 AM WEDNESDAY/...
Wednesday...
A much better day of weather on tap for Wednesday behind the
cold front. Perhaps a few lingering showers across the
Cape/Islands into mid to late morning. Otherwise...becoming
mostly sunny with high temperatures into the 80s in most
locations although a bit cooler across portions of the
Cape/Islands. Much lower humidity though will make for a much
more comfortable day across the entire region.
&&
.LONG TERM /WEDNESDAY THROUGH TUESDAY/...
Highlights...
* Dry and much less humid later Wed thru Fri, possibly into Sat
* Highs 80-85 each afternoon and 50s at night
* Showers/storms and humid conditions return Sunday/Monday
Overview...
17.00z ensembles (ECENS & GEFS) show northeast trough Wednesday
departing and deamplifying which gives way to ridging Friday and
likely lingering into Saturday. At the surface this translates to a
cold front slowly exiting the Cape Wed followed by 1018 mb high
pressure building into New England Wed night/Thu and accompanied by
a much less humid airmass. The high then moves offshore Friday but
with ridge axis arcing back into New England thru Saturday.
Ensembles suggest northern stream remains active with robust mid
level trough entering the Great Lakes this weekend and taking on a
negative tilt along the eastern seaboard Sun/Mon. This will support
a return to more humid weather along with risk of showers/T-storms.
Temperatures...
850 mb temps begin Wed around +13C/+14C but then lower to about +11C
in the post frontal airmass Thu morning, but modify to +13C by days
end, yielding highs in the low 80s away from coastal seabreezes.
Airmass slow warms to about +15C Friday and Saturday which will
support highs in the mid 80s inland. However humidity remains
comfortable as seen by GEFS PWATs remaining below normal (1 to
2 standard deviations below normal) thru Sat with core of dry
air over the region Wed night into Thu. This dry airmass will
support lows in the 50s overnight, very comfortable. Also given
high pres overhead Thu ngt decided to lean toward the cooler MOS
guidance per ideal radiational cooling conditions. This dry
column will also yield plenty of sunshine Thu and Fri, possibly
Sat as well. 850 mb temps remain about +15C Sunday but do warm
to about +17C Mon. However the main story Sun/Mon will be the
increasing humidity as the low level flow becomes southerly and
advects dew pts into the 60s Sunday and then low to mid 70s
Monday!
Precipitation...
Any organized showers/T-storms will be focused across Cape Cod and
Nantucket Wed morning as slow moving cold front and frontal wave
move across this region in the morning. Trailing short wave sweeps
across the region later in the day along with attending cold front
moving offshore. Thus drying trend Wed which persist Thu, Fri and
likely into Sat. Next chance of showers/T-storms likely arrives Sun
and Mon as negative tilt mid level trough dives out of the Great
Lakes into the Mid Atlc region. Heavy rainers possible as
subtropical stream gets captured by negative tilt trough sending
PWATs of +1 to +2 standard deviations up the eastern seaboard into
New England Sun/Mon.
&&
.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short Term /through Tonight/...
Tonight...Moderate confidence.
Line of widespread -RA with embedded RA/+RA, perhaps a rumble of
TSRA. Given isolated nature of TSRA, have removed from terminals.
Focused lowest conditions associated with -RA SE of LWM-ORH-HFD
with potential IFR-LIFR CIGs and MVFR VSBYs. Expected mixed outcomes
S/E with terminals wobbling VFR-IFR.
Should see clearing SE towards morning with a sweeping cold front.
Lowest conditions pushed towards Cape and Islands. However, across
the interior, light winds, recent rains, partial clearing, likely
will be dealing with patchy IFR-LIFR shallow ground fog towards
morning. Noted 3SM BR roughly 8-11z for higher confidence terminals.
With cold frontal passage, could see a brief burst of NW winds
around 320 with 10G20KT, pushing offshore around 12z over Cape
and Islands.
Wednesday...High confidence.
Lingering low clouds/fog patches across the Cape/Islands during
the morning lift by late morning/early afternoon. Otherwise...VFR
conditions. Gusty N winds roughly 15-21z over Cape and Islands
with 10-15KT sustained, gusts up to 25 kts.
KBOS Terminal...
Hold BKN008 for the first couple of hours but should scour out
towards midnight then hold VFR with winds turning N.
KBDL Terminal...
Ground FG possible towards morning. Will hint at the potential
9-11z with 3SM BR for now. Increase if greater confidence is
obtained.
Outlook /Wednesday through Sunday/...
Wednesday Night through Saturday: VFR.
Saturday Night: MVFR/IFR conditions possible. Slight chance
SHRA.
Sunday: Mainly VFR, with areas MVFR possible. Chance SHRA,
chance TSRA.
Sunday Night: Mainly MVFR, with local VFR possible. Chance
SHRA, chance TSRA.
Monday: Chance SHRA, chance TSRA.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short Term /through Tonight/...High confidence.
Tonight...
Cold front pushing offshore overnight towards morning. With
passage by morning could see a brief uptick in winds out of the
NW with sustained values 10-15 kts with gusts up to 25 kts.
Otherwise, through the remainder of this evening, SW flow around
10 kts, widespread light rain with embedded heavier showers,
perhaps a rumble of thunder. Contributions to low clouds and
lower visibility for most of the time.
Waves above 5 feet on the outer waters, small craft headlines
continue towards midnight. Will evaluate whether extension is
necessary with cold frontal passage with later forecasts.
Wednesday...
Winds and seas should remain below small craft thresholds. Some
northeast wind gusts up to 25 knots or so are possible across
the Cape/Islands by mid-morning continuing into afternoon,
diminishing towards sundown.
Outlook /Wednesday through Sunday/...
Wednesday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft.
Thursday: Winds less than 25 kt. Seas locally approaching 5 ft.
Thursday Night through Saturday: Winds less than 25 kt.
Saturday Night: Winds less than 25 kt. Seas locally approaching
5 ft.
Sunday: Winds less than 25 kt. Seas locally approaching 5 ft.
Chance of rain showers, chance of thunderstorms.
Sunday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. Chance of rain showers, chance of thunderstorms.
Monday: Winds less than 25 kt. Areas of rough seas. Chance of
rain showers, chance of thunderstorms.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 11 PM EDT this evening for
ANZ250-254>256.
&&
$$
SYNOPSIS...Frank/Nocera
NEAR TERM...Frank/Sipprell
SHORT TERM...Frank
LONG TERM...Nocera
AVIATION...Frank/Nocera/Sipprell
MARINE...Frank/Nocera/Sipprell
Area Forecast Discussion
National Weather Service Cheyenne WY
715 PM MDT Tue Jul 17 2018
.UPDATE...
Issued at 709 PM MDT Tue Jul 17 2018
Upgraded inherited fire weather watch to a warning for Carbon and
Albany Counties for Wednesday. Conditions out there are close to
Red Flag conditions now with 700mb winds of 10-15 knots. Forecast
for tomorrow showing 700mb winds of 20-25kts, so do expect
stronger winds. Confidence very high in this happening given
current conditions. Also added extreme southwest Carbon County
(FWZ 304). Updates have been sent.
As for ongoing Severe Thunderstorm Watch...instability still quite
high east of the Laramie Range with surface based Capes around
3000 J/KG on SPC`s Mesoanalysis page. HRRR showing redevelopment
of convection over the next couple hours. So will keep the watch
going for now. By sunset, we should know what the convection is
going to do.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 206 PM MDT Tue Jul 17 2018
Convection starting to fire around the Laramie Ranges so far and
expect this to continue as activity moves east through this
evening. Potential for some severe storms there with the best area
looking to be over northern parts of the CWA plains into this
evening where better instability and shear is expected. Storms
should move a little faster than yesterday but with wet grounds
over the Panhandle any heavy rain could produce some flooding so
will maintain the watch there for tonight. Convection should taper
off/move out later tonight as a shortwave move by the area.
Dry and pretty warm conditions will be over the CWA Weds through
Thursday under a dry wnw flow atop an upper high centered over
the 4 corners area. This will cut off the monsoonal flow for the
with the high in that position. Concerns will be more with fire
conditions the next two days as the airmass dries.
.LONG TERM...(Thursday night through Tuesday)
Issued at 206 PM MDT Tue Jul 17 2018
Little change seen for Friday though a minor cool front should
nudge temps down a bit as it passes by in association with a weak
impulse. Chances for mainly afternoon and evening convection
should increase a bit over the weekend into early next week as
moisture begins filtering back over the area. An upper low moving
east over the Canadian prairies may drive a decent cool front
across the CWA towards Monday and help chances for pcpn then.
&&
.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1141 AM MDT Tue Jul 17 2018
The main concern with this forecast package is the thunderstorm
chances again this afternoon and evening.
Latest water vapor loop was showing a shortwave tracking through
northern Wyoming. This feature was tracking east and should cause
some thunderstorms to flare across northern Wyoming this
afternoon. There is also enough moisture and upslope flow to
trigger some isolated convection along the southern Laramie Range.
Therefore, we went ahead and inserted some VCTS in the LAR/CYS TAF
sites early this afternoon. Not as confident during the early
evening at this point, but we will continue to monitor through the
afternoon. Further north in KCDR and KAIA thunderstorm chances are
looking fairly good this evening as an area of thunderstorms
should blossom northeast Wyoming and track east-southeast towards
the KCDR and KAIA taf sites between 04-06z. Meanwhile, KSNY and
KBFF may be on the southern edge of this complex of storms.
&&
.FIRE WEATHER...
Issued at 206 PM MDT Tue Jul 17 2018
Increased fire weather concerns over the next couple days as drier
air moves over the area. Some gusty winds out west both Weds and
Thursday afternoon and with dry fuels have opted to post a Fire
Weather Watch for tomorrow afternoon/early evening for zones 303
and 308 where at least marginal conditions should occur. Similar
setup for Thursday. Otherwise mainly dry and warm weather for the
rest of the week then some increase in moisture should allow for
an uptick in convection over the weekend.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Red Flag Warning from 11 AM to 8 PM MDT Wednesday for WYZ303-304-
308.
NE...Flash Flood Watch until 6 AM MDT Wednesday for NEZ002-003-
019>021-054-055-095-096.
&&
$$
UPDATE...GCC
SHORT TERM...RE
LONG TERM...RE
AVIATION...REC
FIRE WEATHER...RE
Area Forecast Discussion
National Weather Service Dodge City KS
1100 PM CDT Tue Jul 17 2018
...Updated Aviation...
.SHORT TERM...(This evening through Wednesday)
Issued at 321 PM CDT Tue Jul 17 2018
Outflow boundary from an early morning MCS over western Nebraska
into central Kansas had pushed through southwest Kansas by late
morning. Satellite imagery shows the boundary continuing to push
south through central Oklahoma while western portions of it have
become nearly stationary over the Oklahoma Panhandle. Surface
winds north of the boundary over far southwest Kansas have veered
with time and become light and variable to southerly at 5-15 mph.
Visible satellite and radar imagery are indicating some
thunderstorms developing along the outflow boundary over the
Oklahoma Panhandle where surface moisture convergence has been
focused for the past several hours.
Model output concerning the timing and areal coverage of convection
late this afternoon through tonight is pretty variable which does
not make for much confidence in this forecast. Given the way the
surface features have lined out this afternoon, it seems that the
HRRR has the best handle on the near term storm evolution,
especially regarding the OK Panhandle storms. Later this evening
and through the overnight hours, the HRRR has been suggesting that
clusters of thunderstorms developing off the Colorado Front Range
will propagate east into southwest Kansas later this evening into
the overnight hours. This seems reasonable given the increasingly
unstable airmass developing north of the outflow boundary over far
southwest/southern Kansas as indicated by the SPC Mesoanalysis
page. A weak upper disturbance showing up in the water vapor
imagery over northwest Kansas at this time could aid in sustaining
this overnight convection. Have reconfigured late afternoon and
overnight precipitation chances to reflect this thinking. Far
northeast sections of the forecast area may not see any storms
tonight but can`t totally rule them out there either.
Thunderstorms will be winding down or moving out of the forecast
area by daybreak Wednesday. The exception to this will be the
northeast part of the area around Hays. The NAM has also been
hinting at another MCS diving out of eastern Wyoming into northern
Kansas by Wednesday morning. Current forecast tracks would take it
east of the Hays area but will maintain some slight chance pops
there in the morning for that.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 321 PM CDT Tue Jul 17 2018
The extended period will see the upper level ridge building
eastward toward the central and southern High Plains. The models
continue to show a break in thunderstorm activity across western
and central Kansas through the end of the week, along with the
possibility of warmer temperatures at least on Thursday and
possibly Friday. Disturbances passing by through the northern High
Plains could force frontal boundaries down into western Kansas
that will keep the very hot temperatures confined to the southern
Plains. By early next week the models show the upper level high
pressure retrograding back into the western states with northwest
flow aloft over the central High Plains. This is a favorable
pattern for late evening and overnight convective complexes
developing off the eastern slopes of the Rockies and rolling
southeast through western Kansas so we could be looking at a
return to wetter weather by the middle of next week.
&&
.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1100 PM CDT Tue Jul 17 2018
As of 04z, a large thunderstorm complex was moving east near P28
and a smaller complex was slowly weakening over eastern Colorado.
Outside of a mention of VCSH at GCK, do not see convective impacts
at any of the terminals for the next several hours. Some models
drag convection eastward over SW KS overnight, others don`t, so
kept TSRA out of the TAFs for tonight for now. Consensus of short
term models show MVFR (perhaps IFR) stratus developing at HYS/DDC
after 09z Wed, with some support from 00z NAM. With the very
moist boundary layer and weak upslope components, included this
stratus in the DDC/HYS TAFs around 12z/sunrise. Daylight
Wednesday, light SE winds and a VFR cumulus field will prevail.
Additional scattered convection is expected after 21z Wed, most
likely across the NE zones near HYS, and this is where a TEMPO
convective group was included.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 68 94 70 100 / 40 10 10 0
GCK 66 92 67 99 / 30 10 10 0
EHA 69 96 68 101 / 30 10 10 10
LBL 69 97 69 102 / 40 10 10 0
HYS 69 89 69 97 / 30 20 10 10
P28 72 94 72 101 / 60 10 10 0
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Gerard
LONG TERM...Gerard
AVIATION...Turner
Area Forecast Discussion
National Weather Service Wilmington NC
1055 PM EDT Tue Jul 17 2018
.SYNOPSIS...
Increased chance of showers and thunderstorms will continue as a
cold front moves slowly across the area tonight into Wednesday. The
front will dip south of the region on Thursday before shifting back
to the north this weekend.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
As of 1030 PM Tuesday...Most of the convection has faded away later
this evening leaving only some lingering areas of pcp across the
forecast area. Main activity back to the west associated with cold
front and should move slowly southeast and diminish in intensity
leaving mainly chc of lingering lighter pcp overnight with only a
slight chc of any stronger convective development possible
overnight.
Discussion from 300 PM follows...
The shortwave trough moved off the coast this morning and is
still producing widespread convection off the coast. The latest
models show the large scale trough to our north and only a few
weak shortwaves embedded in the upper level flow. Currently
scattered convection is occurring inland and 16 UTC HRRR is
showing coverage increasing after 6 PM and then lingering
overnight mainly over southeast North Carolina through sunset.
The weak cold front is expected to reach the coast around sunrise
Wednesday and then slowly shift just south of the area. The models
continue to show the deep moisture over the forecast area through
Wednesday and thus will a good chance of showers and thunderstorms
for our area on Wednesday.
Lows tonight are expected to be around 73 inland to 77 at the
beaches, and the highs will reach the mid to upper 80s.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 305 PM Tuesday...The front will continue to drift southward
Wednesday night, stalling just south of the forecast area during
Thursday and Thursday night. A moisture gradient will become
established as a result with high precipitable water values clipping
the far southern zones to the waters east of Cape Fear, and the
lowest values toward the northern Pee Dee and LBT zones. POPs will
follow a similar striation through the short term with the best
chances Wednesday night. The continued chance of rain, cloud cover,
and surface ridge from the north will keep highs a few degrees below
normal during Thursday.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
As of 305 PM Tuesday...Cold front and weak surface wave will be
lifting north across the region on Friday. This low level ascent
will be bolstered by mid level height falls and vorticity advection
and even upper level divergence. These factors in the face of
precipitable water values approaching all time high values of 2.4"
points to the potential for heavy rainfall. Models are not in
agreement with the placement of the front/track of the low and thus
where the heaviest rainfall occurs (coastal vs inland). Some of the
ECMWF QPF forecasts have been quite impressive and the recent 12Z
run has joined the GFS in favoring coastal areas. At some point on
Saturday there may be a lull in the heavy rain as the first energy
aloft moves offshore but another source of lift will impinge upon
the area soon thereafter as the Great Lakes trough reloads. Models
show the next slug of rain Saturday night or Sunday. By Monday the
deep moisture along the front will be shunted offshore but lingering
dynamic-type showers could linger area-wide.
&&
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
As of 00Z...Convection will remain active over the southern portion
of the CWA through 02Z, then wind down but still isolated overnight.
A cold front will drop into the CWA toward morning, but will stall
along the coast. Some near IFR conditions are possible especially
inland overnight with post frontal stratus. Wednesday, the front
still hangs out along the coast with still a decent chance for
thunder. The inland terminals will be in a bit more stable air, but
still could get a scattered shower. Winds will be northerly by
daybreak at the inland terminals, finally becoming northerly in the
afternoon along the coast.
Extended Outlook...Occasional MVFR to IFR conditions due to
scattered to numerous showers and TSTMs Wednesday, Friday, Saturday,
and Sunday.
&&
.MARINE...
NEAR TERM /THROUGH WEDNESDAY/...
As of 1030 PM Tuesday...Will continue with precautionary headlines
for sustained up to 20 knot southwest winds and up to 4 to 5 foot
seas across the coastal waters. These elevated winds and seas shoudl
linger only for a few more hours.
Discussion from 300 PM follows...
Southwest to west winds of 15 to 20 knots will continue ahead
of a weak front that should drift along the coast early
Wednesday. As the front slows the pressure gradient will weaken
and the winds will weaken to 10 to 15 knots of Wednesday. Seas
are expected to build to 3 to 5 feet and then drop slightly by
late Wednesday. Conditions are expected to remain just below
small craft advisory.
SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 305 PM Tuesday...Southwest winds early Wednesday evening
will shift to a northeasterly direction with a very slow frontal
passage during the early morning hours Thursday. High pressure
over the northeast U.S. will ridge southward across the Carolinas
during Thursday with the front just offshore. This pattern will
maintain northeast-east flow during the day with speeds
potentially in the 15-20 knot range. The old boundary may begin
drifting back to the north late in the period, but for the
majority of the adjacent coastal water the flow will remain out
of the northeast-east. Seas will build in the post-frontal regime
during Thursday. The fetch will not allow sea to drop
significantly until late in the period. Potential for scattered
to showers/tstms each part of the forecast given the proximity of
the front.
LONG TERM /FRIDAY THROUGH SUNDAY/...
As of 305 PM Tuesday...Front will return northward back into the
area on Friday with a weak wave of low pressure moving along it.
Wind turns southerly with only a minor increase in speed-the
stronger gradient remaining offshore. Broad cyclonic flow develops
across most of the eastern U.S. by Saturday yielding a category of
wind speed increase Saturday into Sunday. As this flow persists a
few advisory-worthy 6 ft seas could develop.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...Beach Hazards Statement until 8 PM EDT this evening for SCZ054-
056.
NC...Beach Hazards Statement until 8 PM EDT this evening for NCZ106-
108.
MARINE...None.
&&
$$
SYNOPSIS...III
NEAR TERM...TRA/DRH
SHORT TERM...III
LONG TERM...MBB
AVIATION...43
Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
838 PM CDT Tue Jul 17 2018
.SYNOPSIS...
Issued at 310 PM CDT Tue Jul 17 2018
H5 analysis from this morning Had a broad trough of low
pressure extending form northwestern Quebec-south into West
Virginia. Ht. falls of 50 to 60 Meters extended from northern
Michigan into srn Quebec this mroning. Further west, northwesterly
flow extended into the northern Rockies of the CONUS and Canadian
Rockies. West of this flow, a strong shortwave trough of low
pressure was centered over central Idahao/far swrn Montana this
morning. South of this feature, high pressure was anchored over
southern Nevada, central Texas and the western Caribbean. WV imagery
as of midday had the Idaho shortwave slightly farther east into
Western Montana with a secondary shortwave noted in northwestern
Wyoming. At the surface, a stationary front extended from
southeastern Montana into northern Iowa. Low pressure was noted over
sern Montana with a sutrace trough extending south into central
Wyoming. Across western and north central Nebraska this afternoon,
skiws were partly cloudy and readings as of 3 PM CDT ranged from 81
at Imperial to 85 at North Platte.
&&
.UPDATE...
Issued at 838 PM CDT Tue Jul 17 2018
A new forecast is in place using the RAP and HRRR plus time
lagging. The models are backing off on the thunderstorm coverage;
probably because of increasing nocturnal stability. The new
forecast focuses the best rain changes across ncntl Nebraska which
would appear to be consistent with lack of thunderstorm coverage
across the Panhandle.
UPDATE Issued at 616 PM CDT Tue Jul 17 2018
A forecast update is in place which carries the thunderstorms
across Northeast WY southeast through wrn and ncntl Nebraska
overnight. The forecast uses a blend of the HRRR, HREF and RAP
plus time lagging. This might be too aggressive as the RAP dives a
MCS mostly west of highway 83 and while the HRRR carries it right
over North Platte. HREF splits the system and weakens its as it
approaches highway 83 toward sunrise.
The westward moving plume of low level moisture located near
highway 83 on radar adds some uncertainty to the forecast as the
models don`t seem to capture this. The RAP does show a 20-30kt low
level jet developing tonight and this should fuel the forecast
for likely thunderstorm development. If the storms across WY move
south of the Black Hills in a few hours then the forecast sould
verify.
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 310 PM CDT Tue Jul 17 2018
Precipitation chances continue to be the main forecast challenge
in the near periods. A strong shortwave, currently over
southwestern Montana/northwestern Wyoming will initiate convection
across the Bighorn Mountains mid afternoon. As this activity
moves east into the northern panhandle, the models congeal it
into a MCS this evening. As to where the MCS tracks overnight is
somewhere up in the air with this mornings model runs. The GFS is
the outlier at this time, lifting convection due east overnight.
Other model solutions including, the Canadian, WARW, and NAM 12
solutions lift this convetion southeast into the northwestern
forecast area, then central and southern forecast area late
tonight. The prescence of a decent low level jet and enhanced
moisture axis, extending from swrn into northwestern portions of
the forecast area tonight. That being said, am favoring the latter
model solution which forces convection se across the forecast
area overnight. PWATS once again will be above 1.5 inches in my
west, which will facilitate a heavy rain threat tonight. In
addition, wouldn`t be surprised if we see some strong wind gusts
as the complex pushes southeast. With this in mind, and given
portions of Sheridan county which are prone to flooding saw some
heavy rain last night, am going to hoist a flash flood watch for
Sheridan county tonight. South southeast of Sheridan county, a
swath of decent rainfall fell across the western sandhills and far
swrn Nebraska overnight. In these areas, the main concern for
flash flooding would be in swrn Nebraska. Given the latest model
forecasts track the heaviest rainfall east of this axis of heavy
rain from last night, am not as concerned about a flash flood
watch attm. The convective complex will push into south central
Nebraska overnight with a lingering threat for thunderstorms in
the east and sern forecast area Wednesday morning. The shortwave
trough will track across South Dakota and northern Nebraska on
Wednesday. There will be a lingering threat for thunderstorms,
mainly east of highway 83.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 310 PM CDT Tue Jul 17 2018
Wednesday night through Friday...The upper level trough
will slowly track into eastern South Dakota Wednesday night with the
trough axis aligned with the Missouri River Thursday morning. There
will be a lingering threat for thunderstorms Wednesday evneing,
before convection pushes east of the area. The upper level low will
lift slowly east Thursday into central Minnesota then Wisconsin on
Friday. Subsidence behind the exiting trough and drier air will push
into the region with dry conditions expected. Temperatures will
remain seasonal with readings in the 90s for Thursday, followed by
upper 80s for Friday.
Friday night through Tuesday...Ridging will amplify across the
central and northern Plains Friday night into Saturday with dry
conditions continuing. On Saturday night, the ridging will break
down thanks to a strong shortwave approaching the northern Rockies.
Mid level warm air advection will increase as the ridging breaks
down. This will lead to a chance for thunderstorms Saturday night
into Sunday. Another round of thunderstorms are possible Sunday
night into Monday as a cold front is forced through the forecast
area.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 616 PM CDT Tue Jul 17 2018
The thunderstorms across WY are expected to move southeast, into
and through wrn and ncntl Nebraska tonight. Scattered to numerous
thunderstorm coverage is expected unti 15z Wednesday. Isolated
thunderstorm coverage is expected along and east of highway 83
15z-21z Wednesday. Scattered thunderstorm coverage is expected
east of highway 83 21z-00z Wednesday afternoon.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch until 6 AM MDT Wednesday for NEZ004.
&&
$$
UPDATE...CDC
SYNOPSIS...Buttler
SHORT TERM...Buttler
LONG TERM...Buttler
AVIATION...CDC
Area Forecast Discussion
National Weather Service Marquette MI
700 PM EDT Tue Jul 17 2018
.SHORT TERM...(This evening through Wednesday)
Issued at 411 PM EDT TUE JUL 17 2018
WV imagery and RAP analysis indicated a mid/upper level trough from
nrn Quebec into the ern CONUS and a ridge from the nrn plains into
Saskatchewan resulting in nw flow through the wrn Great Lakes. At the
surface, high pressure was building into Lake Superior and Upper
michigan bringing diminishing winds and clearing skies with mainly
just few/sct inland cu. Seasonably cool dry air has also spread
across the area with temps from the low and mid 60s north to the the
lower 70s south and dewpoints around 50.
Tonight, favorable radiational cooling conditions with light winds,
clear skies and PWAT values at or below 0.5 inch will allow temps to
drop to the lower end of guidance with mins into the lower 40s
inland, with a few upper 30s possible in typical cold spots.
Wednesday, Another day with light winds and mostly sunny skies as
the sfc high builds slowly to the southeast of the area will allow
prominent lake breezes to develop. Expect highs to range from
around 70 near the Great Lakes to near 80 inland.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 411 PM EDT TUE JUL 17 2018
Models suggest that a developing cutoff low moving from the Upper MS
valley into the western Great Lakes will dominate the weather late
this week into the weekend. Another low will approach the area,
moving into Manitoba early next week. This will keep high temps at
or below normal with wet/unsettled weather.
Wednesday night into Thursday, As the high slowly moves away to the
east, increasing southerly winds and WAA will bring temps back to
around 80 with the coolest conditions along Lake Michigan. Clouds
will also thicken over the west by Thu afternoon as the mid level
and sfc low move into MN.
Friday through Sunday, The models continue to show some differences
in handling the evolution of the low with the ECMWF now remaining
farther north with the track compared to the GFS/GEFS. Regardless of
the eventual track, sct/nmrs showers are expected to develop from sw
to ne Friday and continue through Saturday before slowly diminshing
from the west Saturday night into Sunday morning. The greatest
instability and tsra chances are expected Fri afternoon into Fri
evening with modest MUAPE values in the 500-1000 J/Kg range
possible. Only isold tsra may be possible over the east by Saturday
as more stable air with nrly low level flow moves in by Saturday
evening.
Mon-Tue, confidence is low with the timing of rain chances early
next week as the ECMWF is faster with the progress of the mid level
low and shortwave trough moving into the region Monday compared to
the GFS/GEM which maintain sfc riding over the area before pcpn
chances finally move in Tuesday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 700 PM EDT TUE JUL 17 2018
VFR conditions will prevail through the forecast period.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 411 PM EDT TUE JUL 17 2018
High pressure will continue to build across Lake Superior tonight
bringing diminishing winds. The high pressure will slowly slide off
to the southeast Wednesday/Thursday. South to southeast winds will
increase again late Thu into Fri to possibly as high as 25 knots
over eastern Lake Superior ahead of an approaching low pressure
system over the Plains.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...JLB
LONG TERM...JLB
AVIATION...07
MARINE...JLB
Area Forecast Discussion
National Weather Service Blacksburg VA
1046 PM EDT Tue Jul 17 2018
.SYNOPSIS...
A cold front will travel east to the coast by Wednesday morning.
High pressure follows with drier and somewhat cooler weather
into the end of the week.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
As of 1040 PM EDT Tuesday...
Still some lingering showers in the piedmont east of Lynchburg
as well as across the NC foothills/mountains ahead of the cold
front. Mesoanalysis shows deeper moisture convergence in these
areas as well.
Drier air starting to work into the WV mountains, and will take
all night to edge to the Blue Ridge. Should still see showers
diminish across the area by 1-2am, with fog mainly in the
mountains.
Previous discussion from early evening...
Best instability and storm coverage has exited the piedmont with
just a few showers/storms across the mountains in a secondary
axis of higher instability ahead of the front. High-res solution
still painting a threat of showers in a scattered nature
early this evening before things dry out, mainly in the NC
portion of the forecast area. Otherwise, still some delay in
drier air late will provide opportunity for fog formation
overnight, especially in the mountains. No other major changes
to the forecast from earlier.
Previous discussion from early this afternoon...
A cold front in the mountains this afternoon will move east tonight
into Wednesday. Scattered to numerous showers and thunderstorms are
expected ahead and along the cold front. A pre-frontal trough across
the piedmont and southside trigger convection aided by a weak upper
shortwave. SPC Mesoscale analysis at 18z showed CAPEs 2 to 3k j/kg
and Lis from minus 1 to minus 3. Isolated severe thunderstorms may
be possible this afternoon with gusty winds and hail as main threat.
With high PWATs from 1.5 to 2.0 inches, some of the storms will
contain heavy rains. Hiresw-ARW-EAST, HRRR and NAMnest showed a
couple of clusters or bands moving east across the forecast area.
The GFS and ECMWF also have showers and thunderstorms moving
across the area this afternoon into tonight. The convection
should diminish with the loss of solar heating tonight. The
frontal boundary should push out of the region overnight
allowing the flow to turn northwest with decent cool advection
developing northwest half late as the upper trough passes across
the region. Areas of fog will develop overnight into Wednesday
morning. Low temperatures will range from the mid 50s in the
northwest mountains to around 70 degrees in the piedmont.
High pressure will build southeast out of the Ohio Valley on
Wednesday in our region. High temperatures Wednesday will vary from
the lower 70s in the mountains to the mid 80s in the piedmont.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 310 PM EDT Tuesday...
High pressure over New England will wedge south into the Carolinas
Wednesday night and linger into Friday morning. Most of the forecast
area will remain dry with the exception of the Mountain Empire of
West Virginia to the High Country of North Carolina where the wedge
will erode and an inverted surface trough stretches north from the
Tennessee Valley to the southern Ohio Valley Thursday. Coverage of
convective will be isolated. Any afternoon showers will fade during
the evening.
Dry cooler air will bring a dramatic drop in humidities Wednesday
night into Thursday night as dew points fall into the lower 50s.
Overnight lows will also trend cooler with 50s across the mountains
to lower 60s east. With dry air and abundant sunshine in the
afternoon, Thursday`s highs will range in the 80s with mid 70s along
ridgetops.
The wedge will hang around through Friday, but will erode from the
west and southeast. An upper level trough is expected to become a
close low over the Great Lakes on Friday. This low will send short
waves into the Ohio Valley and erode the wedge from the west. Across
the Southeastern states, a tropical disturbance is expected to track
along the wedge boundary, then off the North Carolina coast Friday
night. As this disturbance advances north, it will erode the wedge
from the southeast. As the wedge erodes, the chances for showers and
thunderstorms will increase, especially across the mountains Friday
afternoon into the evening. Temperatures and humidity will also be
on the increase Friday with highs in the upper 70s to lower 80s west
of the Blue Ridge to the mid to upper 80s east.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 245 PM EDT Tuesday...
On Saturday, the closed low expands into the Deep South and covers
most of the US from the Mississippi Valley eastward. In the
afternoon, there is a negative tilt to the trough in the eastern US
that could bring active weather to the region. A weak cold front
will then slide across the region Saturday night. Sunday, moreso
Monday and Tuesday, could be active days with heating occuring under
the cold pool as the closed low may dive south over the area.
The area will remain under a trough through most of next week as a
strong blocking ridge drifts westward in the Western Atlantic.
Afternoon and evening showers and thunderstorms are likely each day
from this weekend into the following week. Temperatures will run
cooler than normal through the period.
&&
.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
As of 713 PM EDT Tuesday...
A cold front in the mountains will move east tonight. Most
convection will be away from the terminals though could see a
few showers still near enough to Danville to keep in the TAFS
for now around 01-02z.
Drier air will arrive Wed morning, so with some residual
humidity and wet ground with clearing skies, fog will be likely
in the mountains. KLWB is the taf site with the best chance
for IFR/LIFR fog, with MVFR to IFR at times at BLF/BCB. High
pressure building in from the north should bring widespread VFR
under drier air for Wednesday.
Medium confidence in ceilings, visibilities and winds during the
taf period.
Extended Aviation...
Return flow looks to transport moisture back into the area
Thursday and Friday but still looking at mainly VFR. Scattered
showers and thunderstorms with sub- VFR conditions are expected
Saturday ahead of the next cold front. Scattered showers and
thunderstorms are likely on Sunday.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...KK
NEAR TERM...KK/WP
SHORT TERM...RCS
LONG TERM...RCS
AVIATION...JH/KK/WP
Area Forecast Discussion
National Weather Service Tucson AZ
905 PM MST Tue Jul 17 2018
.SYNOPSIS...Plenty of moisture and instability will remain in
place to support daily showers and thunderstorms through at least
the middle of the week. Partial drying from the east may lead to
reduced thunderstorm coverage by the weekend, along with hotter
temperatures.
&&
.DISCUSSION...Thunderstorms continue this evening mainly SW of
Tucson where greatest instability resides, but a couple of storms
even occurring over the Rim at this hour. 00z sounding showed
increased easterly mid level flow which is aiding in storm
intensities, increasing storm movement and providing increased
potential for strong wind gusts. HRRR has been verifying well
since late this afternoon and continues to show that thunderstorms
will continue to move across primarily western and central Pima
County into the overnight hours. Cannot completely rule out a
stray shower or storm in the Tucson Metro eastward through at
least midnight. Will keep the 10 percent chances there as in the
going forecast.
&&
.AVIATION...Valid through 19/06Z.
Isolated to scattered SHRA/TSRA mainly west of KTUS and near the
International Border through the night. The Wednesday morning
hours should be dry but at least ISOLD TSRA coverage is expected
again after 18/19z. Cloud bases 8k-12k ft AGL with SCT- BKN
clouds above 20k. Winds remain below 12 kts through the period,
with stronger gusts possible around TSRA. Aviation discussion not
updated for TAF amendments.
&&
.FIRE WEATHER...A shift in the weather pattern will begin to
take place, bringing in drier air and reducing rain chances.
However, isolated storms could still develop, especially over the
higher terrain. Temperatures also gradually warm through the week.
20-ft winds remain below 15 mph, although the Upper Gila River
Valley will experience gustier northwesterly winds at times.
&&
.PREV DISCUSSION...The upper low moving through Sonora, Mexico
along with the northern extent of the inverted trough passing
through Arizona was showing up nicely in Satellite water vapor
imagery. Showers and a few thunderstorms were developing this
afternoon in the vicinity of this upper low and across far western
Pima county. This general area will be the main focus of showers
and thunderstorm this evening and tonight. Cannot rule out a few
thunderstorms farther north though. Otherwise, high pressure aloft
will become established over the Great Basin region around
Wednesday before shifting over the Desert Southwest this coming
weekend. This adjustment in the position of the upper high will
result in some warming and drying aloft by the end of the week.
This warmer and drying will eventually translate to less
thunderstorm activity and hotter daytime temperatures by the
weekend.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...None.
&&
$$
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Area Forecast Discussion
National Weather Service Las Vegas NV
700 PM PDT Tue Jul 17 2018
.SYNOPSIS...Hot and humid conditions will continue through mid week
with thunderstorms possible across much of the forecast area
through the end of the week, especially in the higher terrain.
&&
.UPDATE...At 7 pm...scattered thunderstorms were primarily confined
to parts of Lincoln County and northern Mohave County with a couple
of weak cells in western Clark County. The activity in Lincoln
County is expected to drift to the southeast into the northeast
portion of Clark County over the next few hours. In general, there
should be a downward trend in most of this activity after sunset.
Updates are out. -Salmen-
&&
.PREVIOUS DISCUSSION...231 PM PDT...
.SHORT TERM...through Thursday night.
Two primary weather features influencing our weather are high
pressure currently centered over the central California coastline
and an inverted trough moving across southern Arizona and northern
Mexico. Overnight, the high pressure center moves inland over
central California and the inverted trough pushes into southern
California. Any storms that survive or develop overnight, will
generally move to the southwest across Mohave County and southern
San Bernardino County. The last several runs of the HRRR has trended
away from bringing storms out of Lincoln County into Clark County.
Left a chance of showers/storms in the Spring Mountains and Sheep
Range this evening but kept the Las Vegas Valley dry based on the
latest HRRR forecast.
On Wednesday, high pressure shifts east into central Nevada while
the inverted trough lifts northwest across San Bernardino County.
This track will bring higher moisture and increasing instability
across the Sierra and Inyo County. More than sufficient moisture and
weak instability elsewhere will give most areas a chance of showers
and storms Wednesday afternoon/evening with the possible exception
of San Bernardino County which will lie in an unfavorable region of
downward motion behind the trough.
The high is forecast to re-position over the four corners area on
Thursday with a general southeasterly flow setting up across the
forecast area. Any embedded disturbances or decaying MCS that form
south-southeast of our area Wednesday night could become a player
influencing convective activity Thursday.
An Excessive Heat Warning is in effect through Wednesday evening for
the Owens Valley and Esmeralda County with a Excessive Heat Advisory
in effect for the White Mountains of Inyo County. Hot and humid
conditions are expected with sky conditions and temperatures greatly
influenced by the amount of clouds spread across the region from
decaying overnight convection.
.LONG TERM...Friday through Tuesday.
By FRI, an upper level trough over NW Canada and the NW Pacific will
help nudge the ridge overhead eastward, eventually moving it over
New Mexico and Texas by Saturday. The eastward propagation of the
high should result in some mid-level dry air off the SoCal coast to
filter in across southwestern portions of our CWA FRI-SAT. However,
lingering low level moisture combined with daytime heating will
still allow for thunderstorms to develop mainly along higher terrain
through the weekend. By SUN-MON, models are now shifting the high
pressure back across the southwest and over Arizona. This westward
propagation will increase temps and continue to keep thunderstorms
chances mainly focused over the higher terrain through TUE. Main
threats with any thunderstorm development will be localized
flooding, small hail, and strong to severe outflows capable of
producing damaging winds and blowing dust.
Besides storm chances, expect light winds less than 10-15 mph,
temperatures to increase a degree or two each day and partly sunny
to partly cloudy skies.
&&
.AVIATION...For McCarran...Outside of convective influence, light,
variable winds below 10 knots will continue across the terminal
through the afternoon, favoring an easterly direction. Probability
of outflow affecting the terminal this evening is low. CIGs should
remain above 10k feet.
For the rest of southern Nevada, northwest Arizona and southeast
California...Scattered to isolated thunderstorms across the region
through the remainder of the afteroon with storms likely to persist
through the night along and south of Interstate 40 through southern
California and southwest Arizona. Outside of thunderstorm
influences, winds will follow diurnal trends with speeds of 5-15
knots. CIGs at or above 10k feet in general but CIGs may drop to 5-7
k feet in shower and storms.
&&
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&
$$
SHORT TERM/AVIATION...Salmen
LONG TERM.............Kryston
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