Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/21/16
Area Forecast Discussion
National Weather Service La Crosse WI
633 PM CDT Tue Sep 20 2016
.SHORT TERM...(This evening through Wednesday)
Issued at 325 PM CDT Tue Sep 20 2016
Main concerns are on heavy rainfall tonight through Thursday and the
possibility for flash flooding. This could potentially be a
serious flooding situation!
Ongoing showers and isolated thunderstorms will weaken this
afternoon then severe thunderstorms are expected to develop late
this evening into the overnight hours with the main threat of
heavy rainfall. Some of the storms may also produce damaging winds
and perhaps large hail if updrafts are rotating.
A warm front lifts north into the area tonight brining a tropical
airmass into the area with precipitable water values climbing to 1.5
to 1.8. These values combined with warm cloud depth of 3.5 to 4 km
will set the stage for a potential flash flood event. The nose of
the low level jet focuses into the front tonight with 850 mb
moisture transport of 300 to 500 units slamming into the front.
All of this combined with 30 day mean precipitation values of 200
to 300 percent over the mean, primes the area for flash flooding.
Storms look to initiate over portions of southeast Minnesota into
west central Wisconsin along the front and then edge southward
with time. So, the storms/heavy rainfall may build south into
northeast Iowa and southwest Wisconsin. The storms will capable of
producing very heavy rainfall, 2 inch per hour rates are possible.
Damaging winds are also possible. Storms will be ongoing by
sunrise on Wednesday then are expected to gradually taper off
through the morning hours.
Round two of heavy rainfall takes aim on the area late in the day on
Wednesday into the overnight hours. This is when some of the most
serious flooding could develop, especially if this rain falls over
the same areas as Tuesday night into Wednesday morning. A few
forecast models attempt to push this second round of heavy rain
to the north. Not really buying into that given that outflow from
the storms will help to drive the warm front south...potentially
closer to the interstate 90 corridor. The heavy rain threat
finally tapers off by Thursday evening.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 325 PM CDT Tue Sep 20 2016
For Thursday night into Friday...shower and thunderstorm chances
continue, its just a questions of forcing for the storms. The
warm front meanders in the neighborhood so there is the chance of
seeing more rain...potentially heavy. Will continue to monitor
closely since this would only worsen any ongoing flooding issues.
Friday night through Tuesday....
A deep upper-level trough will be in place over the Rockies for the
start of the weekend. Ahead of the trough, lower-level
WAA/isentropic lift will provide forcing for a broad band of
showers, possibly with isolated thunder, stretching from the central
Dakotas into southeast Minnesota/southern Wisconsin Friday night.
20.12z GFS/20.00z ECMWF are in agreement with lifting the thermal
gradient northward into Saturday, temporarily clearing our CWA of
rain chances. Models become increasingly divergent thereafter. As an
upper-level cut-off low detaches itself from the main flow over the
Four Corners region, the GFS becomes much more progressive, racing
the upper-level trough the Great Lakes region by Monday night.
Meanwhile, the ECMWF holds the trough over the Northern Plains until
Tuesday. This will be the determining factor for the timing and
duration of another round of rain Sunday into Monday. After this
system departs the region, high pressure is progged to build in.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 633 PM CDT Tue Sep 20 2016
The latest runs of the hi-res meso models continue to indicate the
warm front over central Iowa will lift north toward the area this
evening. Convection is expected to form north of this front as the
low level jet starts to impinge on it late this evening. The
20.22Z run of the HRRR is the first to bring this activity in and
have gone with a VCTS on its faster timing and then gone with
categorical showers and storms for much of the overnight. Initial
VFR conditions should drop down to MVFR in the convection with
some IFR possible in the heavier rains. This activity should
continue into Wednesday morning until the low level jet weakens
allowing for a break in the rain. Guidance is mixed on whether
ceilings will drop to IFR behind the rain or go up to VFR and
opted to stay with persistence from the previous forecast with
VFR. The front will still be in the area for Wednesday afternoon
with another round of convection expected to develop in the
afternoon. For now, will show a VCTS at both sites all afternoon
but this could hold off until mid afternoon once the low level jet
starts to increase and interact with the front again.
&&
.HYDROLOGY...Tonight through Thursday
Issued at 325 PM CDT Tue Sep 20 2016
A potentially serious flooding situation is taking shape for tonight
through Thursday. Two main rounds of heavy rainfall. The first,
tonight into Wednesday morning. The second round is expected
Wednesday evening into the overnight hours. Rainfall amounts of 2
to 3 inches with locally higher amounts in excess of 7 inches
possible. Given the very wet conditions across the region flooding
could develop quickly. If these two rounds of heavy rainfall occur
over the same area the flooding could be some of the worst
experienced by many. Stay weather aware and be ready to move to
higher ground! Several rivers could go into flood. Minor to major
river flooding is possible.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Flash Flood Watch from 1 AM CDT Wednesday through Thursday
evening for WIZ017-029-032>034-041>044-053>055-061.
MN...Flash Flood Watch from 1 AM CDT Wednesday through Thursday
evening for MNZ079-086>088-094>096.
IA...Flash Flood Watch from 1 AM CDT Wednesday through Thursday
evening for IAZ008>011-018-019-029-030.
&&
$$
SHORT TERM...WETENKAMP
LONG TERM...WETENKAMP
AVIATION...04
HYDROLOGY...WETENKAMP
Area Forecast Discussion
National Weather Service Bismarck ND
947 PM CDT Tue Sep 20 2016
.UPDATE...
Issued at 948 PM CDT Tue Sep 20 2016
Near term high res models doing fairly well this evening. Made
some adjustments to better reflect latest radar imagery otherwise
the forecast is on track with no major edits from the previous
issuance.
UPDATE
Issued at 659 PM CDT Tue Sep 20 2016
The inherited forecast remains mainly on track. Main edit for the
early evening forecast issuance was to tweak POPs based on latest
regional radar and near term guidance along with cloud cover.
Hard to say anything is reaching ground underneath weak radar
returns about the region, but Sidney MT did report light rain an
hour or two ago so inserted a greater coverage of low POPs
northwest and north central.
Will maintain slight thunderstorm chances through tonight with
both the NAM12 and RAP indicating several hundred J/KG of MUCAPE
southwest into far south central now and through the overnight.
Had thunderstorms this morning under a similar environment so
cannot justify removing.
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 302 PM CDT Tue Sep 20 2016
A split flow regime will develop across the western CONUS and Canada
leading to the eventual development of a closed low over the Great
Basin by Thursday. During this development, southwest flow aloft
will become predominant over the northern plains allowing both
shortwave energy and mid to high level moisture to stream north into
the region. This will set up a scenario that will support both
precipitation efficiency due to the tropical plume, and due to
the slow movement of the closed low, a rather extended period for
rain chances.
For the short term period, rain showers and scattered thunderstorms
will develop across western and North Dakota late this afternoon
and tonight as the first in a series of weak shortwaves move
through the region. The CAM models all are in agreement with the
best chances across the north tonight. With Cape very limited will
generally go with showers across the north tonight. By Wednesday
the wave moves through and scattered showers and a isolated
thunderstorms will linger. Highs on wednesday will be cooler, in
the 60s.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 302 PM CDT Tue Sep 20 2016
Main feature in the long term will be the negatively tilted h500 low
forecast to move from the Great Basin region Thursday eventually
merging into the northern stream trough over the northern and
central plains by Saturday-Sunday. While both the GFS and ECMWF
are in general agreement the ECMWF is definitely more progressive
in merging this upper low with the northern stream on Saturday.
With a fair amount of uncertainty on the track and timing will
end up focusing the highest pops west Thursday and Friday where
there is more certainty. Then Saturday a good push of moisture
should swing through the central sections of the region as the
upper low swings through. Storm total rainfall is forecast to be
nearly 2 inches far northwest to around a half an inch south
central.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 659 PM CDT Tue Sep 20 2016
Increasing sky cover with rain showers moving in across western
into parts of north central North Dakota tonight with KISN and
possibly KMOT being impacted with rain. CIGS and VIS should
remain VFR through the 00Z period with a low VFR (4-6K Feet AGL)
the lowest cloud deck expected.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...NH
SHORT TERM...WAA
LONG TERM...WAA
AVIATION...NH
Area Forecast Discussion
National Weather Service Denver/Boulder CO
843 PM MDT TUE SEP 20 2016
.UPDATE...
Issued at 824 PM MDT Tue Sep 20 2016
Satellite pictures show a significant batch of mostly upper level
cloudiness moving over the CWA in southwesterly flow aloft. Some of
cloudiness is lower upstream with radars showing some showers over
the CWAs to the west and southwest. Models keep the extensive mid
and upper level cloudiness over the CWA overnight and much of
Wednesday. Will increase the cloud cover on the sky grids. Pops
overnight look okay. Will keep them out of the dry plains for
sure. Temperatures will stay pretty warm with all the cloud cover
overnight.
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 257 PM MDT Tue Sep 20 2016
For the remainder of today it will unseasonably warm and will
remain dry area-wide other than an isolated storm or two for the
Central Colorado Rockies. This evening and tonight the remnants
of Tropical Storm Paine off the coast of Mexico will phase with a
cut off low off the coast of southern California. Zonal flow at
500 mb exists across the northern Rockies, while the 500 mb ridge
is centered over Oklahoma. The result for Colorado is SW mid and
upper level flow across Colorado with considerable upper level
moisture continuing through the short term. The moisture from the
is advected for the next 36 hours and should keep us mostly
cloudy. A subtle short wave trough crosses Colorado before sunrise
Wednesday and both the NAM and the HRRR initiate light
precipitation in the mountains and sustains the showers across
the Denver metro area. It`s still quite dry in the low levels so
have low confidence in rain reaching the ground, but have seen
enough in the high res model signal to raise PoPs after 3 AM local
time to slight chance for the metro area. Minimum temperatures
tonight will stay in the low 60s across the Denver metro area and
eastern Plains, and in the 40s in the mountains given the warm
temperatures this afternoon and expected cloud cover tonight.
Throughout the day on Wednesday, a deep/strong trough will dig
south along the Pacific Northwest coast. This will continue to
advect upper level moisture across Colorado keeping the area
mostly cloudy. The low-levels will continue to be dry with surface
dewpoints will be in the lower and mid 40s across the Plains, 30s
in the mountains. Once again the best chance for afternoon
thunderstorms will be over the central Colorado Rockies. In terms
of temperatures, the warm overnight lows coupled with the dry low-
level air means temperatures should still have little trouble
getting into the mid 80s east of the mountains despite the mid and
high cloud cover. However, the cloud deck should be thicker than
today as so temperatures will be a few degrees cooler than
Tuesday, but still well above average for this time of year.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 257 PM MDT Tue Sep 20 2016
For Wednesday evening, could see just a couple showers and an
isolated storm drift northeast across the mountains, but overall
the airmass will be too stable and subsident to support much
precipitation. Lower elevations should remain dry. Temperatures
will stay quite mild but a cold front is expected to push into
the northeast plains toward Thursday morning.
This front may usher in some stratus across the northeast plains
and lead to some cooling especially on the northeastern plains for
Thursday. The airmass will destabilize in the afternoon but
mainly over the mountains as the boundary layer cools slightly on
the plains. Could still see a couple storms drift off the higher
terrain or develop on the plains toward late in the day if slight
cooling aloft occurs ahead of the deep upper level low dropping
into the Great Basin.
It appears the best chance of precipitation may occur Friday as
the upper level low approaches from the west. Right now, all
medium range models are pointing to a piece of energy rotating out
of this low and across the forecast area. This along with cooling
aloft should effectively destabilize the atmosphere so will have
the best PoPs then. Winds are also expected to increase from the
mountains eastward across the Palmer Divide and most of the plains
with strong southerly flow and pressure gradient in place.
Temperatures expected to get cold enough in the mountains for some
snow potential but appears we`ll be getting into the dry slot so
threat for much accumulation appears quite limited into Friday
night.
By Saturday, the upper level trough will begin to fill and
gradually shear. We will still be under the cold pool aloft so
will continue to keep a chance of showers and a few storms in the
forecast. Temperatures will turn considerably cooler with highs
mostly in the 60s on the plains and 40s/lower 50s in the
mountains.
The cooler weather will remain in place through Sunday, Monday,
and Tuesday as the trough weakens and/or shears southward into the
Desert Southwest. The chance of precipitation will likely decrease
through this period.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 824 PM MDT Tue Sep 20 2016
Normal drainage winds are in place at DIA this evening. They should
continue with pretty weak speeds. There will be plenty of mid and
upper level cloudiness all night and most of Wednesday. There
should be no precipitation or ceilings under bkn-ovc100.
&&
.BOU Watches/Warnings/Advisories...
None.
&&
$$
UPDATE...RJK
SHORT TERM...Schlatter
LONG TERM...Barjenbruch
AVIATION...Meier
Area Forecast Discussion
National Weather Service Grand Rapids MI
758 PM EDT TUE SEP 20 2016
LATEST UPDATE...
Update/Aviation
.SYNOPSIS...
Issued at 330 PM EDT Tue Sep 20 2016
After a quiet overnight period, scattered showers and thunderstorms
will become possible on Wednesday and linger through Thursday night.
The most commonplace rainfall will occur over Central Lower, with
less rain as one heads south. Very little, or even no rain may
occur toward I-94 through Thursday night.
The scattered rain may linger until Friday evening before we finally
dry out for a what looks like a quiet weekend. Another chance of
rain moves back in for Sunday night.
Wednesday and Thursday will remain warm, with highs in the upper 70s
to lower 80s, but then we will cool down. Highs will mainly be in
the upper 60s to lower 70s Friday through Tuesday.
&&
.UPDATE...
Issued at 747 PM EDT Tue Sep 20 2016
The update reflects more in the way of cloud cover tonight.
Also...I included a potential for showers up north for tonight.
The elevated showers developing in northeastern Wisconsin are
shown to build southeast with some of the HRRR runs...into Big
Rapids and eventually Mount Pleasant. Satellite imagery also shows
cloud building on top of us...so more in the way of cloud cover
is likely to occur for tonight.
&&
.SHORT TERM...(This evening through Thursday night)
Issued at 330 PM EDT Tue Sep 20 2016
Rain chances return early Wednesday and linger into Thursday night
as a surface boundary hangs up over the region.
High pressure will drift off to the east overnight as a slow moving
front sags SE across the U.P. We will begin to see moisture
advection by daybreak and an increase in mid level clouds. We may
even see an isolated shower or storm advance toward the lakeshore by
daybreak Wednesday.
The front stalls over Northern or Central Lower Wed and Thu before
finally drifting a bit south Thu night. Much of the pcpn will be
concentrated near the front. Upper waves will travel along it, but
they appear to weaken as they head our way, being much stronger over
MN/WI/IA. Will continue to feature highest POPs across Central
Lower with placement of the front, but a bit more widespread rain
should be seen late Thursday night with the front advancing a bit
south. Also expect to see an enhanced rain late Wednesday afternoon
into Wednesday night across Central Lower with moderate upper
divergence sliding across from the upper jet.
High temps will be tricky over the next couple of days, largely
depending on the amount of sun that occurs. Mid 80s are certainly
possible with enough sun, which may occur in the far south. But
overall expect more upper 70s to around 80 to occur with a fair
amount of clouds around. Therefore I did lower max temps for Wed in
most places.
.LONG TERM...(Friday through Tuesday)
Issued at 330 PM EDT Tue Sep 20 2016
Plains cyclogenesis may increase mid level warm advection/isentropic
ascent enough to bring showers Friday night into Saturday. This is
followed by shortwave ridging ahead of the western CONUS upper
trough and generally fair weather Saturday into Sunday.
Precip chances increase again Sunday night and Monday as heights
fall and sfc cold front/prefrontal trough moves in. There is still
low confidence here as ensemble spread continues to be large and the
precip may hold off until Monday night and Tuesday as indicated by
the slower solutions.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 747 PM EDT Tue Sep 20 2016
Will need to monitor the thunder risk for late tonight and
Wednesday morning for KMKG and KGRR. Convection is expected to
become widespread over in Wisconsin tonight. The storms should
build east later tonight and eventually reach into MI for
primarily Wed AM. Thus I added this to the forecast. Showers
currently in northern WI will likely build southeast and could
reach KGRR and KLAN in the middle of the night.
The storms should dissipate by noon...with a break expected then.
The risk for storms will increase again after 00z Thu.
&&
.MARINE...
Issued at 330 PM EDT Tue Sep 20 2016
Winds will be fairly light through the short term and will become
offshore. So no headlines are expected. However 2-3 foot waves
will be possible Wed afternoon north of Grand Haven with a south
flow around 15 knots.
&&
.HYDROLOGY...
Issued at 330 PM EDT Tue Sep 20 2016
Hydro impacts through this weekend will be limited. Rain and
thunderstorm chances will exist Wednesday and Thursday, mainly north
of I-96. A frontal boundary draped across Central Lower Michigan
will be the focus for diurnally-driven shower/storm activity.
Total rainfall amounts will likely exceed half an inch (0.50 inches)
well to the north of I-96, affecting the Upper Muskegon River basin
and Pere Marquette River basin. Mostly within bank river rises
are expected.
&&
.GRR Watches/Warnings/Advisories...
MI...None.
LM...None.
&&
$$
UPDATE...MJS
SYNOPSIS...JK
SHORT TERM...JK
LONG TERM...Ostuno
AVIATION...MJS
HYDROLOGY...EBW
MARINE...JK
Area Forecast Discussion
National Weather Service Wilmington NC
1055 PM EDT Tue Sep 20 2016
.SYNOPSIS...
An upper cutoff low across the eastern Carolinas, will catch the
remnants of Julia during Wed. This conglomerate will meander
across the eastern Carolinas through the end of this week before
finally getting drop kicked off to the ne late Fri. This will
accelerate it away from the carolina coasts early this weekend.
Weak high pressure will temporarily build into the area on Sat. A
strong cold front will move across the area during Sunday followed
by strong high pressure in its wake bringing the first hint of
Autumn early next week.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
As of 945 PM Tuesday...The cutoff upper low meandering across the
Carolinas has finally been able to wrap, counter clockwise, the
Atlantic moisture from off the northern Outer Banks, back to the
southwest which is now falling as light rainshowers across the
western portions of the ILM CWA...via latest mosaic radar trends.
The HRRR, RAP and the HighResWrf, all 3 illustrate this potential
increase in the wraparound moisture falling across the FA
overnight into the next period. The forcing from the cutoff low
is aiding the generation of pcpn tonight. If the low clouds areable
to scour out some after sunrise Wed, then instability will be
added to the equation. This will result in a further increase in
convection, with thunder being added to the mix during Wed mid to
late morning. As for cloudiness, increased the low stratus
coverage to mostly cloudy or just plain cloudy phraseology for sky
conditions overnight. For temps, will stay on the milder side of
model Mos Guidance for tonights lows. Overall POPs tonight will
remain in the low to modest chance categories, with the overall
hier chances across the western 1/2 of the ILM CWA. With PWs in
the 1.75 to 2.00 inch range, moisture availability will not be the
problem for pcpn development.
Previous.........................................................
As of 300 PM Tuesday...An upper low spinning around in theACarolinas
will continue to provide unsettled weather across the area through
tonight. Low clouds and spotty light showers or drizzle were
covering much of the area into this afternoon. A moist northerly
flow was wrapping around the remnant low from Julia as some drier
air aloft wraps around the back of the upper low. Sounding data
and time height sections show drier air aloft from h70 and above
which looks like it may mix down enough to produce a few breaks in
the clouds especially across inland.
This all makes for a tricky forecast as the clouds will hamper
heating and therefore instability while areas that see any sunshine
will become more unstable and should see some convective
development this aftn. The cool pool aloft will drift south over
the area helping to sharpen lapse rates and promote some
convection associated with differential heating or low level
convergence. It looks like the best upper level energy and support
will ride around the upper low and combine with best convergence
associated with sfc low to produce best chc of shwrs from N-NE to
S-SW across the area through tonight. HRRR shows pcp mainly
aligned along I-95 corridor and west with only spottier shwrs to
the east closer to the coast. With such a cool pool aloft, you can
not rule out isolated thunderstorms, but temps were struggling to
make it much past the mid 70s limiting the sfc heating needed to
steepen lapse rates.
Temps will hold in the mid 70s in most places and will not drop
too much tonight under a very moist air mass with plenty of cloud
cover.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
As of 300 PM Tuesday...The remnants of Julia or a broad area of
low pressure/trough will remain up the Carolina coast through mid
week. Initially the circulation will drift southwest as it
continues to be pulled by upper low. This will leave a moist
northerly flow across much of the area through Wed into Thurs. The
models are not in total agreement with evolution of this
low/trough but it looks like it will be pulled back westward
briefly on Wed which may produce a period of on shore flow and
possibly enhance low level convergence but also may enhance
thunderstorm activity along the coast. It will depend on the
exact location of the low, both at the surface and aloft, to
determine where the best convergence, lift and upper level support
will be, but the potential will exist with a decent cool pool
aloft. Overall, expect a good deal of clouds and showery weather
through much of the period with isolated thunderstorms possible.
o
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
As of 300 PM Tuesday...Remnant mid-level circulation of Julia will
still be overhead by Friday, before finally lifting off to the NE
as high pressure builds across the area on Saturday. Friday will
be near seasonable temperatures with periods of clouds of showers,
but as subsidence develops behind the departing upper impulse,
Saturday will likely rise to above climo again with mucho more
sunshine. This warmth will be short-lived however, as a deep
trough then digs into the northeast driving a back door type cold
front into the Carolinas Sunday, with much cooler temperatures
lasting into the beginning of next week. Increased clouds and
showers are possible Sunday into Monday with the FROPA, but the
forcing is weak and moisture is limited to the lowest part of the
column. This suggests more clouds/drizzle into Monday than true
showers, but will carry low-end POP before drying out by Tuesday.
Temps Sun-Tue will drop to more seasonable levels, and our first
taste of fall-like temperatures may occur early next week.
&&
.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
As of 00Z...Pretty ugly aviation conditions tonight through the
overnight hours with IFR conditions becoming widespread due to
stratus. Likewise visibilities will lower below two miles at times
due to drizzle. Conditions will be at their worst from 06Z-13Z, with
slowly improving conditions after 15Z. North northwest flow is
expected through Wednesday morning, becoming more easterly in the
afternoon. If we get any sun on Wednesday (which is pretty
unlikely), we could see some heavier convection in the afternoon.
EXTENDED OUTLOOK...Isolated to scattered afternoon and early
evening convection possible underneath the cutoff upper low
through Friday. MVFR/IFR morning stratus/fog possible each day
thru Sunday.
&&
.MARINE...
NEAR TERM /THROUGH TONIGHT/...
As of 1000 PM Tuesday...The cutoff low across the eastern
Carolinas this evening is progged to capture whats left of Julia
at the sfc and become partly barotropic. The sfc pressure pattern
overnight will result in a nw to n wind directions. The resultant
wind speeds will only be around 10 kt due to a somewhat relaxed
sfc pg. Significant seas overnight will run only 2 to 3 ft.
Dominant periods will run 7 to 8 seconds due to a pseudo swell
from the ese around 1 foot. Wind waves at 4 second periods will at
times dominate the significant seas overnight.
Previous..............................................
As of 300 PM Tuesday...Northerly winds will back a little
overnight as low pressure gets pulled southward, but overall
expect N-NW 10 to 15 kts. Winds will diminish a bit and become
more variable overnight. Seas will remain less than 3 ft.
SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGoHT/...
As of 300 PM Tuesday...Northerly winds may become quite variable
as remnant low of Julia gets pulled southward and possibly inland
late Wed. This should produce a more on shore flow on Wed.
Overall winds and seas will be determined by the exact fate of
this remnant low/trough through mid week. A longer period up to 12
second SE swell will mix in by Wed night into Thurs.
LONG TERM /FRIDAY THROUGH SUNDAY/...
As of 300 PM Tuesday...A mostly weak gradient with N/NW winds
will persist Friday and Saturday ahead of a back door type cold
front which will sag across the waters during Sunday. Wind speeds
Fri/Sat will be light, 5-10 kts or less, before steadily
increasing behind the front to 10-15 kts from the NE during
Sunday. WHile the wind will provide littloe contribution to the
sea spectrum, a 3-4 sec/11 sec SE swell from Tropical Cyclone
Karl will exist both Friday and Saturday, producing seas of 2-4
ft. On Sunday, this swell will slowly wane but a NE 5-6 sec wave
will quickly amplify, producing wave heights of 3-5 ft the latter
portion of the extended.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...None.
MARINE...None.
&&
$$
SYNOPSIS...JDW
NEAR TERM...DCH/RGZ
SHORT TERM...RGZ
LONG TERM...JDW
AVIATION...DL
Area Forecast Discussion
National Weather Service Lincoln IL
837 PM CDT TUE SEP 20 2016
.UPDATE...
Issued at 837 PM CDT Tue Sep 20 2016
No significant updates needed this evening as high pressure axis
into central IL combined with westerly flow remaining north of the
area should keep convection forming over the upper Midwest from
moving into central IL overnight. Lows should reach the lower 60s
east of I-57 ranging up to the upper 60s west of I-55 where higher
dewpoints and slightly higher southerly winds prevent as much
cooling.
&&
.SHORT TERM...(This evening through Wednesday)
ISSUED AT 239 PM CDT Tue Sep 20 2016
Weak boundary a bit tough to pick out this afternoon on surface obs,
but best estimates are that it extends from near Macomb to just
north of Danville. Cumulus field continues to expand along the
boundary to near the I-70 corridor this afternoon. No sign of any
convection yet, but SPC mesoanalysis shows CAPE`s are now in the
3000 J/kg vicinity and the cap is eroded. Latest HRRR has now
started hinting at some isolated development, and will maintain the
isolated PoP`s for this afternoon, mainly between the Illinois River
and I-70.
Main steering flow will remain to our north through Wednesday, and
overnight MCS which is progged to develop over southern Minnesota
and northern Iowa will track into Wisconsin and extreme northern
Illinois on Wednesday. Local impacts would mainly be some cirrus
blowoff across the northern CWA, but skies should again be mostly
sunny. With little air mass change going on, have bumped up highs
for tomorrow a couple degrees and mainly went around 88-89 degrees
over the entire forecast area.
.LONG TERM...(Wednesday night through Tuesday)
ISSUED AT 239 PM CDT Tue Sep 20 2016
Somewhat flat ridge will remain anchored over the southern part of
the US for the last part of the week and then begin to build into
the northern Miss valley for the weekend, as an upper level trough
pushes east into the plains. This pattern will bring dry and very
warm conditions to the CWA through the rest of the week and into the
weekend. With 850 temps reaching to between +18C and +20C, expecting
highs in the mid to upper 80s through most of the forecast period.
The extended models remain different in their timing of the upper
level trough for the latter part of the weekend. The ECMWF has been
the most consistent and slowest over the last several days so will
lean toward that solution and have gone several degrees warmer than
guidance for highs for Sun and Mon. The associated frontal system
finally gets into the state Sunday night and this will be the next
real chance of precip in the area. The chance of precip will
diminish as you go east and southeast, so chance pops will be in the
northwest for Sun night/north and northwest Monday/and small area in
the northeast for Monday night. By Tue, dry weather should return to
the area.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 636 PM CDT Tue Sep 20 2016
VFR conditions expected the next 24 hours as high pressure keeps
the track of convective systems to the north. Winds generally S-SE
through the period. Speeds generally under 6 kts overnight, then
8-10 kts after 16Z.
&&
.ILX Watches/Warnings/Advisories...
NONE.
&&
$$
UPDATE...Onton
SHORT TERM...Geelhart
LONG TERM...Auten
AVIATION...Onton
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
911 PM CDT TUE SEP 20 2016
.UPDATE...
911 PM CDT
Main forecast concern continues to be with shower and thunderstorm
potential in the late overnight through Wednesday morning. 00z
RAOBs across the region sampled ample elevated instability. On the
nose of a 30-40 kt 850 mb low level jet, convection is beginning
to fire over southern Minnesota as expected. There is likely to be
an expansion of coverage into extreme NE IA and western WI, with
shear/MUCAPE supportive of some severe storms. The main question
is evolution of this convection later overnight.
High-res guidance has been insistent on clustering/merging into
at least a loosely organized MCS. Mid and upper level thickness
and mean wind pattern, along with Corfidi vectors would argue for
a east- southeast propagation, which could keep it north of our
area. Overall, convection would likely be on a weakening trend
with slightly lower MUCAPE and weakening veered LLJ over our area,
though cannot completely rule out a stronger embedded storm
northwest of Rockford. Another wild card is if there is any cold
pool propagation which could force storms farther south and/or
serve as a focus for additional convection, something that the
HRRR and a few other hi-res models have been trying to hint at.
With variation in guidance and competing factors for how far south
convection may make it into the CWA by the early morning,
confidence is low. Largely maintained previous forecast PoPs, with
some minor tweaks to slow them to predawn hours in far north
areas.
RC
&&
.SHORT TERM...
306 PM CDT
Through Wednesday...
Main forecast concerns/challenges are with thunderstorm chances
very late tonight into Wednesday morning, with a definite
possibility for for an upstream MCS to move southeast into
northern Illinois Wednesday morning.
In the near term, high pressure has settled in across the region,
helping for some quieter weather today. Under sunny skies,
temperatures have rebounded back into the 80s once again with
upper 80s temps being reported across the southern CWA. The
potential for isolated thunderstorms this afternoon is appearing
to quickly lower despite instability and moisture pooling along
remnant boundary over east central Illinois and northwest Indiana.
Increased CU in the zone being observed, but once again, don`t
really anticipate any precip this afternoon into the evening.
Clearer skies this afternoon into the early evening will be
replaced with current upstream cloud cover over the Upper Midwest,
while low temps once again fall to the 60s.
Will see the air mass change significantly tonight into Wednesday
as mid to upper 60s dewpoint air pushes north over the entire CWA.
This higher dewpoint air combined with upper 80s will bring humid
conditions back on Wednesday. Focus will be on how expected
upstream convection over MN/IA/WI will evolve later tonight.
Guidance varying with the evolution of this thunderstorm
development with one scenario keeping this precip to the north of
the CWA through Wednesday morning. However, short term and hires
guidance beginning to really key in on these thunderstorm diving
southeast into northern Illinois early Wednesday morning. This is
beginning to be a very probable solution, and have trended the
forecast in this direction. Guidance consistent with
instability/moisture axis shifting well north across much of the
region by Wednesday morning. With this pattern in place, it would
make sense that these thunderstorms would follow
moisture/instability axis southeast into the CWA. High
instability/steep mid level lapse rates are expected to also be in
place that would support this scenario. So once again, trended
forecast this way and increased pops with coverage wording. Did
not go overly high on pops, given the possibility for this precip
to not go as far south, but could see the evening shift increasing
pops this evening once a better handle is grasped. If this precip
does reach northern Illinois, timing would be 5-7 AM CDT for the
Rockford area and then 8-10 AM CDT for the Chicago area. Would
anticipate this precip to be on a decaying trend, but there is the
possibility for some isolated stronger storms. If more robust
development is present, large hail and strong winds would be the
main threats. Precip chances should diminish by midday and early
afternoon, but will also need to monitor any possible outflow
boundary, which could support additional development in the
afternoon.
Rodriguez
&&
.LONG TERM...
229 PM CDT
Wednesday night through Tuesday...
Wednesday Night through Friday:
Broad 500mb ridging persists across the Southern Plains as an
upstream trough is steadily digging south through California. This
setup will keep the main channel of stronger vorticity oriented
along a Central Plains to Northern Great Lakes. Surface ridging
remains rather diffuse but positioned downstream of the Great Lakes,
which could provide some weak steering of precip back north of
Northern Illinois. In the near term for Wed ngt, the boundary will
be setting up along or just north of I-80 in Northern Illinois, so
have higher POPs in those areas meanwhile maintain dry conds to the
south. Guidance tries to develop a shortwave along the lee-side of
the Rockies in Colorado Thur morning, as the downstream southerly
flow is poised to strengthen, this should help push the quasi-
stationary boundary further north into Wisconsin. Thursday evening
operational solutions continue to push the main frontal boundary
north; however, there is some indications that a weak mid-lvl trough
at 500-700mb may dip over Southern Wisconsin, which could bring some
weakening showers/storms southeast towards Northern Illinois late
Thur/early Fri.
Then heading towards the end of the week the upstream 500mb trough
will transition towards a cutoff low across the Southwest CONUS, as
ridging downstream over the Great Lakes tries to amplify. Depending
on cloud cover and precip chances over the next few days will
dictate how warm surface temps become, but with the several days
in the past being dry, afternoon highs will likely rebound to
above climo conditions in the middle 80s and mild overnight temps
in the low/mid 60s.
Saturday through Tuesday:
Dry conditions look to persist through the first half of the
weekend, as the upstream cutoff low remains over the Central
Rockies. Meanwhile downstream areas will continue to be influenced
by an amplified ridge. Surface ridge over Ontario is progged to
push a surface boundary south across Lower Michigan Saturday,
which could bring slightly cooler air to Northern Illinois for
Sun/Mon. Then ensembles are in good agreement with a trough
sliding east across the High Plains early next week, as a large
ridge develops over the Western CONUS and transitions the Great
Lakes region towards a quasi northwest flow for next Tue.
Beachler
&&
.CLIMATE...
Record highs and warm lows:
Chicago Rockford
High Low High Low
Wed 9/21 92(1970) 76(1931) 94(1920) 70(1895)
Thu 9/22 92(1956) 73(1895) 93(1937) 65(1959)
Fri 9/23 91(1937) 71(1891) 92(1937) 66(1920)
&&
.AVIATION...
For the 00Z TAFs...
Primary concern is with the potential for a round of showers and
thunderstorms Wednesday morning. Despite dry and stable conditions
at the surface, strong instability will form aloft over the region
tonight. Clusters of TSRA are expected to develop over the Upper
MS Valley tonight and then form at least a loosely organized
complex that tracks east-southeast or southeast. Main uncertainty
lies with whether the SHRA/TSRA move mainly across southern WI by
morning, clipping far northern IL, or are able to propagate
farther southeast and impact the terminals.
Guidance remains somewhat split on how things evolve, keeping
confidence low. Thus opted to maintain PROB30 for direct impacts.
Did introduce a VCTS to the RFD TAF. Should the SHRA/TSRA do make
it farther south into the area, shown on recent runs of the HRRR,
then the potential also exists for a wind shift to the north-
northeast, which would delay a return to the overall south-
southwest regime favored tomorrow. Furthermore, cannot rule out
any lingering outflow from serving as a focus for additional
convection during the afternoon. This is a very low confidence
scenario, so after the morning PROB30s, left the TAFs dry.
With better moisture streaming northward at the surface and aloft
tonight, some low clouds in the 2500-3000ft range developing
overnight. MVFR BR is possible as well, though given how dry
conditions are early this evening, confidence is low in occurrence
and opted to pull VSBY restriction from the ORD/MDW/GYY TAFs.
RC
&&
.MARINE...
229 PM CDT
High pressure centered over Southeast Ontario and the Eastern
Great Lakes with a continued light gradient over much of Lake
Michigan through Wednesday; however, as a low pressure develops
across the Southern Plains Wed evening, a frontal boundary will be
strengthening over the Northern Portions of Lake Michigan. This
will bring southeast to south winds stronger over the southern
half of the lake, meanwhile northeast winds increase to the north
of the boundary. Current expectation is that speeds will hover
between 15-20 with gusts around 25 kt. This boundary will meander
from the northern half of the lake to central through Thur/early
Fri, before pushing further south as a area of high pressure
builds across western Ontario Fri evening. This will help to
increase the gradient across the central/southern portions of the
lake with southeast to south winds.
Beachler
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
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Area Forecast Discussion
National Weather Service Marquette MI
726 PM EDT TUE SEP 20 2016
.SHORT TERM...(This evening through Wednesday)
Issued at 414 PM EDT TUE SEP 20 2016
WV imagery and RAP analysis indicated a zonal pattern across most of
the nrn CONUS with a trough moving into the Pacific Northwest. A
weak shortwave trough and area of 800-600 mb fgen supported some
light showers or sprinkles from near KDLH into wrn Upper Michigan.
Very dry air below 700 mb will limit the extent of the pcpn with only
slight chance pops mentioned late this afternoon. Otherwise, mid
clouds were thickening over the area with a broad area of 300-310k
isentropic lift in advance of sfc low pres over South Dakota.
Tonight, expect mid clouds to linger over the region in the waa
pattern with the 850-700 baroclinic zone lingering over the area.
Shra/tsra are expected to remain south of the cwa, closer to the
850mb front and higher MUCAPE values. Otherwise, the clouds will
keep min temps mainly in the 50s.
Wednesday, pcpn chances will increase from s to n as the 850 mb
front gradually lifts to the north. Additional weak shortwaves in
the fast zonal pattern will likely also support shra/tsra
development. However, with the relatively dry low level ne flow
north of the front, the pcpn into the nrn cwa will be slow with
likely pops south and only chance pops north. With MUCAPE values
fcst into the 500-1000 J/Kg over the far south some TS will also be
possible. The thickening clouds will limit highs to the upper 60s to
lower 70s.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 311 PM EDT TUE SEP 20 2016
Still on track to see zonal flow aloft mid week transitioning to
more amplified flow by this weekend as sharp ridge develops over the
central Conus between upper trough over eastern Canada and trough
crossing western Conus. At the sfc, a stationary front will lift
across the Upper Great Lakes Wed night through Thu Night, then
slowly settle south on Fri. Waves of low pressure tracking along
the front will help enhance rain chances. Models have been locked on
to overall scenario with pwats upward of 1.25 inches lifting into
the stationary front and along/ahead of the waves of low pressure
and large scale lift over entire area enhanced by right entrance
region of jet over northern Ontario across Quebec and any shortwaves
that will be sliding through. Heavier rain likely sets up farther
south of Upper Michigan closer to main sfc front and where MLcapes
over 1000 j/kg are located, but some heavy rain could affect south
half of cwa as that area is on gradient of h85 theta-e. Overall
there is fair agreement from the models in this scenario, though
exact placement of heavier rain remains uncertain.
Bigger question still remains on how quickly the front slips south
of area to bring dry weather on Fri. There has been little run-to-
run consistency in all models in whether front and associated
showers will be south of Upper Michigan or still lingering over at
least southern parts of cwa. At this time, GEM is most aggressive in
hanging onto qpf while last two runs of GFS and ECMWF would point to
mostly dry conditions as large Canadian high pressure builds in from
Manitoba and northern Ontario. More differences for Sat as ECMWF
continues to indicate qpf over far west and southwest cwa. Seems
these showers are tied to shortwave/q-vector convergence and h85
frontogenesis on edge of h85 thermal ridge. Trouble is that ECMWF is
not consistent with the solution as it has been back and forth on
this the last couple days. Ribbon of higher h85 RH quite narrow even
on the ECMWF focused over northern WI into sw Upr Michigan so think
it is overdone in showing broadbrushed and light qpf across much of
Upper Michigan in the 06z-18z time frame on Sat. Temps late this
week probably end up near to blo normal in the low to mid 60s,
coolest near Lk Superior with persistent northeast winds btwn the
high pressure over northern Ontario and sfc front to the south.
High pressure builds across the Great Lakes Sat and Sat night. Given
such an amplified pattern aloft, the sfc high may not move out of at
least eastern half of Upper Michigan until later Sun or Sun night.
Though timing is not set, the approaching upper level trough and sfc
trough along with low-level return flow on west side of retreating
high help will bring rain back to the area. Could be dealing with
moderate to heavy rain as pwats in the return flow regime are
forecast to top out over 1.75 inches as deep moisture flows north
off the western Gulf of Mexico. There are differences in how quickly
the sfc trough and axis of higher pwat cross Upper Michigan. This is
tied to how quickly shortwave trough moves across Upper Great Lakes
and what extent of shortwave energy is left out across the Central
Plains on Mon. Similar to late this week, run-to-run consistency on
these details in the models is lacking and agreement among the
models is also poor. Will keep using a consensus, which tilts
slightly toward quicker GFS, until these differences can be sorted
out. Though a slower solution would result in max temps Sun and
possibly Mon above normal in the 70s, will keep with consensus temps
mainly in the 60s due to the uncertainty in the timing for the
front.
Front should be east of here on Tue leaving a breezy day with some
clouds and a few light showers eventually giving way to decreasing
clouds as high pressure begins to build back in from the west.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 725 PM EDT TUE SEP 20 2016
Although there wl be a good deal of mid clds at times, dry llvl air
wl ensure VFR conditions prevail at all 3 TAF sites this fcst
period.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 414 PM EDT TUE SEP 20 2016
West southwest winds to 25 knots will diminish to 20 knots or less
tonight into Wed as the pres gradient weakens with the Canadian low
lifting farther ne across Hudson Bay. Winds will remain blo 20 kts
into Saturday under a weak pres gradient across the Upper Lakes.
Southerly winds will increase Sunday to 20 knots as a low pressure
trough approaches from the west.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...JLB
LONG TERM...JLA
AVIATION...KC
MARINE...JLB
Area Forecast Discussion
National Weather Service Phoenix AZ
Issued by National Weather Service Tucson AZ
730 PM MST TUE SEP 20 2016
.SYNOPSIS...
Tropical moisture continues to cover the region resulting in
extensive cloud cover and some areas of light rain. This scenario
will through Wednesday with slow clearing into Thursday. A strong
low pressure system will develop over the Great Basin during the
latter half of the week bringing cooler air over the region and just
a slight chance for showers.
&&
.DISCUSSION...
WV imagery and objective analysis depicts several distinct
shortwaves impacting (or about to impact) the SW conus this evening.
The first such synoptic wave has lifted into northern AZ with a
secondary trailing wave hovering off the srn CA coast. Lastly, the
circulation of Tropical Depression Paine was creeping north up the
Baja peninsula. In between all these features, much of cntrl AZ has
fallen within a region of subsidence albeit with extensive daytime
cloud cover which has limited instability. Some MLCape has been
noted along the international border where isolated deep convection
has blossomed though northward progression of echoes shows rapid
deterioration into a less favorable environment.
While a few showers could potentially survive into central AZ, the
main focus for the remainder of the night will align with the wave
lifting though SE CA. Based on radar reflectivity, HRRR trends seem
a bit aggressive on shrinking areal coverage of light rain.
Therefore, have kept greatest POPs through the western CWA while
cutting POPs through the eastern 2/3rds slightly (towards isolated
coverage). Light showers may eventually translate eastward into AZ
towards Wednesday morning, though model support for more extensive
coverage is still slim. Otherwise, minor adjustments were made to
capture current observational trends, but nothing astounding
overall.
&&
.PREVIOUS DISCUSSION...
/210 PM MST TUE SEP 20 2016/
Visible satellite imagery is reflecting copious moisture from
Tropical Storm Paine moving over the region, moving towards the
northeast. The western and north portions of our forecast area
remain under overcast skies but we are seeing some breaks in the
overcast, especially in eastern Yuma County and portions of Maricopa
and Pinal counties. This could actually cause a bit of extra heating
which might help promote possible shower and thunderstorm
development. At this time, however, we are not seeing any lightning
strikes so far so this may not come to fruition.
Rainfall amounts have been mostly on the light side. The largest
amounts we have seen so far have been along and near the Colorado
River valley with radar estimates in the 0.6 inch range near Parker
and north of Quartzsite. Still, amounts have been low enough and slow
enough to not lead to any significant flooding concerns.
Rain chances will continue through Thursday but slowly decreasing
across the region as the remnants of the tropical storm will be swept
away in as a short wave. At the same time a developing strong low
pressure system will drop into the Great Basin. This will bring cool
area through the area with just a slight chance of some light showers
possible. Over the weekend dry air will move in. Temperatures will
keep on the cool side, staying below normals for this time of year.
&&
.AVIATION...
South-Central Arizona Including KPHX, KIWA, and KSDL:
Much of the night should remain dry for Phoenix area terminals,
through some light showers may enter airspace Wednesday morning,
then again Wednesday afternoon. Confidence is good that cigs will
remain above 8-10K ft through much of the night, however there is a
slim chance sct cloud bases near 6K ft could form around the area
partially obscuring surrounding mountains later Wednesday morning.
Otherwise, a northerly cross wind will be common through midnight
before backing to a more traditional easterly direction, though
speeds should remain below 12kt.
Southeast California/Southwest Arizona including KIPL and KBLH:
Isold/sct light showers will continue to impact much of SE CA,
though much of the time frame will remain dry (especially during
daylight hours Wednesday). Cigs could briefly fall towards a 6K ft
level, however will hover in an 8-10K ft range for much of the
period. Sfc winds will generally favor a northerly component through
Wednesday morning before becoming more southerly or variable
Wednesday afternoon.
Aviation Discussion not updated for amended TAFs.
&&
.FIRE WEATHER...
Thursday through Monday...
Much drier air will begin moving in Thursday followed by breezy winds
Friday through Monday. Minimum humidity values will fall into the
10-15 percent range. Critical thresholds may be touched at times
Saturday through Monday, especially across southeast California and
the Lower Colorado River Valley.
&&
.SPOTTER INFORMATION STATEMENT...
Spotter activation will not be needed.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&
$$
Visit us on Facebook...Twitter...and at weather.gov/phoenix
DISCUSSION...MO/Waters
AVIATION...MO
FIRE WEATHER...Iniguez
Area Forecast Discussion
National Weather Service Gaylord MI
255 AM EDT WED SEP 21 2016
.SHORT TERM...(Today and tonight)
Issued at 255 AM EDT Wed Sep 21 2016
High pressure continues to exit east away from Michigan as a warm
front/inverted trough lifts northward into the Upper Mississippi
Valley and far Western Great Lakes region. Main area of convection
associated with this feature is currently impacting SE Minnesota and
SW Wisconsin. Another area of much weaker convection/shower activity
has made some eastward progress out of the Green Bay area across
Lake Michigan into our SW CWA...but is having some difficulty
overcoming the dry low level air entrench over our CWA. Both MBL and
FKS have reported some light rain periodically reaching the ground
early this morning...but no thunder has occurred due to a serious
lack of instability attm.
Latest HRRR and RAP13 both depict this light precip across our SW
CWA attm...while the latest NAM12 shows nothing. HRRR/RAP13 solution
steadily dissipates this light precip by around sunrise early this
morning...as focus for convective development remains further to the
SW along the nrn periphery of the instability axis and 850 mb theta
E ridge. All of the latest runs of the short term models continue to
favor this area for best convective development throughout the day
around the northern extent of the inverted trough. They do lift this
favored are into our SW CWA later this afternoon and evening...
suggesting our better chance for POPs will be during this time.
MUCAPES increasing to near 2000 J/kg and 0-3 kg bulk shear values
increasing to around 30 kts would also suggest a marginal risk of a
few strong to possibly borderline severe storms during this time as
well (in agreement with latest SPC Day 1 outlook).
Have backed off just a bit on pops for much of today...opting to
develop higher pops from late afternoon into tonight as better
instability and moisture finally begin to push NE into our CWA along
the northern edge of the inverted trough axis. Will certainly
maintain the chance of thunder as well...but latest model trends
have delayed the possibility for heavy rainfall until Thursday. Above
normal temps will continue today despite increasing clouds...with
afternoon highs ranging from the lower 70s in Eastern Upper Michigan
to the mid to upper 70s across Northern Lower Michigan. Low temps
tonight will cool back into the mid 50s to lower 60s.
.LONG TERM...(Thursday through Tuesday)
Issued at 255 AM EDT Wed Sep 21 2016
Thursday through Friday night...
High impact weather potential: Embedded thunderstorms and
locally heavy rain possible through Thursday evening.
Pattern synopsis/Expected evolution: A strong 130+ kt northern
stream jet streak is draped across southern Canada, nearly
encompassing the entire width of North America. The main focus will
revolve around two pieces of energy converging toward the Great
Lakes region midweek. The first is expected to pinwheel from western
Canada toward southern Ontario by Thursday. The second, currently
ejecting from the four corners region toward northern Michigan
during the same timeframe. The second wave is progged to continue to
trek northeastward toward the Great Lakes, resulting in low pressure
development across the central plains, bringing increased precip
chances across the MS Valley and Great Lakes region Wednesday
afternoon through at least the first half of Friday.
Guidance continues to suggest a rather impressive baroclinic zone
setting up across the northern Great Lakes into southern Ontario by
Wednesday night through the end of the week into the upcoming
weekend as the aforementioned weakly organized low pressure slides
toward the northeast, draping a warm front across the region.
As a result, potentially locally heavy rainfall will be the main
concern.
Thursday - Thursday night: By Thursday morning, deep layer moisture
is nearing its maximum for the event across northern Michigan with
PWs approaching 1.75 inches. As mentioned yesterday, if a value of
1.75 inches were to verify, it would be 1.00 inch higher than the
daily mean and ~0.50 inch greater than the highest recorded PW for
Sept. 22 via SPC`s sounding climatology for APX. With nearly
unidirectional flow through roughly 200mb, the threat for locally
heavy rainfall remains a concern. By Thursday night, surface high
pressure noses into the northern Great Lakes from Canada allowing
drier air to filter in and gradually diminishing precip chances from
north to south late Thursday night through the first half of Friday.
Friday - Friday night: Precip continues to diminish as northern
Michigan lies on the southern periphery of an expansive area of high
pressure centered over northern Ontario. It could end up feeling
like a rather brisk fall day with occasionally gusty winds, mostly
cloudy skies, and much cooler temperatures filtering into the
region (high temps for many locations struggling to top the mid-60s).
Saturday through Tuesday...
Despite a similar flavor to the overall pattern, global model
guidance varies beyond Friday night in terms of sensible weather
across the area. At this point, will hedge the forecast toward the
drier of the two solutions with Canadian high pressure moving very
little through the end of the weekend. Toward the very tail end of
the extended period, low pressure moves from the northern plains
into the southern Canada resulting in increasing precipitation
chances Monday night-Tuesday as a cold front swings through the
Great Lakes. High temperatures in the 60s throughout the extended
period, which falls within a degree or two on either side normal for
the last week of September.
&&
.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1138 PM EDT Tue Sep 20 2016
VFR conditions expected with slowly lowering cigs in intial stages
of top-down saturation regime (even a few light showers to impact
KMBL for the next few hours). Cigs may lower enough later today
to kick off some additional showers, particularly during the
afternoon hours. Will tentatively cover with vcsh wording. Showers
to become more numerous later this evening, although with limited
cig and vis restrictions. Light winds through this taf period.
&&
.MARINE...
Issued at 255 AM EDT Wed Sep 21 2016
Winds and waves will remain below SCA criteria thru Thursday night.
However...chances of showers and thunderstorms will increase today
and especially tonight and Thursday as an inverted trough/warm front
slowly lifts into the Western Great Lakes region. Best chance for
precip will initially be over Lake Michigan today...with better
chances spreading eastward tonight into Thursday.
&&
.APX Watches/Warnings/Advisories...
MI...NONE.
LH...NONE.
LM...NONE.
LS...NONE.
&&
$$
SHORT TERM...MLR
LONG TERM...Gillen
AVIATION...MSB
MARINE...MLR
Area Forecast Discussion
National Weather Service Columbia SC
420 AM EDT WED SEP 21 2016
.SYNOPSIS...
A surface pressure trough near the coast and upper low over the
area will continue through Thursday. These features will weaken
Friday with ridging more dominate Saturday. A cold front will
approach from the north Sunday.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Upper level low over eastern North/South Carolina this morning.
Surface trough along the coast. Current radar at 08z indicating
showers drifting south from the Pee Dee across the central and
east Midlands. HRRR Model suggest showers may increase across the
area later this morning as moisture flux and weak insentropic lift
increases around 15z...so showers may spread further to the west.
Increased pops during the mid morning through early
afternoon....although should be a sharp moisture gradient in the
west and south...so lower pops in the CSRA. Showers may decrease
later this afternoon although weak to moderate instability may
develop although stronger lift associated with upper level low
should remain northeast of the region. Cloudiness may keep
temperatures down a bit...expect temperatures a few degrees cooler
than yesterday especially north. Although air mass moist with
precipitable water above 2 inches in the east...guidance qpf lower
than previous runs and threat for heavy rain appears diminished
due to weak instability. However...if training develops a few
areas could have locally higher qpf amounts mainly in the Pee Dee
where lift stronger associated with upper level trough.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY/...
The models display surface troughing near the Southeast coast with
an H5 cut-off low over the area continuing through
Thursday..although upper trough appears weaker over the area and
moisture more shallow. Highest pops in the east...expect scattered
coverage. Slightly warmer temperatures thursday with more
insolation expected. Followed the consensus for the minimum
temperature forecast.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
The GFS and ECMWF show the h5 low and surface trough weakening
Friday. A remnant of the features linger into Saturday but ridging
is shown more dominate. A backdoor cold front is forecast to move
into the area Sunday or Sunday night with the front just south of
the area Monday. Another front may be in the area Tuesday. The
GFS has been faster with the timing of these fronts. The GFS and
ECMWF MOS have pops around 20 percent Friday, less than 20
percent Saturday, and 10 to 30 percent Monday and Tuesday. The
MOS indicates above normal high temperatures ahead of the cold
front through Sunday lowering to about normal Monday and Tuesday.
&&
.AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
Upper low will remain over the area through the period with
restrictions possible in stratus.
Upper low will remain just northeast of the TAF sites through the
period with surface low pushing moisture onshore from the NC
coast. This will keep showers across the area with stratus
developing around daybreak through the late morning hours. Shower
intensity currently not expected to be heavy enough to impact
vsbys. Have remained with VCSH for the afternoon hours through the
end of the period as onshore flow will continue the threat of
showers...however confidence in coverage and timing remain low.
Winds through the period will be northerly at 9 knots or less.
EXTENDED AVIATION OUTLOOK...Restrictions possible in showers and
thunderstorms as well as late night/early morning stratus and fog
Thursday through Saturday.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
&&
$$
Area Forecast Discussion
National Weather Service Cheyenne WY
238 AM MDT WED SEP 21 2016
.SHORT TERM...(Today through Thursday night)
Issued at 230 AM MDT Wed Sep 21 2016
Mid to high level clouds continue to stream across the southeastern
half of the CWA. Although the global models do not show much
precip through midday, the HRRR does show light showers in areas
along the Colorado Border. Thus, maintained slight chance pops
through the morning. With the dry llvls, not expecting much more
than sprinkles or very light rain showers. Temps today will be
5-10 degrees cooler than Tuesday in most locations. A cold front
will back into the Nebraska Panhandle overnight with widespread
low clouds developing after 06-09Z over much of the Panhandle and
extreme southeast WY. Put some patchy fog into the northern
Nebraska Panhandle with upslope northeasterly sfc winds along the
Pine Ridge.
Low clouds will be persistent across portions of the plains
through the morning on Thursday. The coolest highs (mid to upper
60s) will be over the northern Nebraska Panhandle where some low
clouds could persist through the entire aftn. South to
southeasterly winds will become breezy by the aftn and early
evening over much of the CWA. Kept 20-40 percent pops mostly
confined to areas west of the Laramie Range through the aftn as
the atmosphere will be capped/stable over the plains. Could see a
slightly better coverage of showers and isolated tstms into
Thursday night as the better forcing ahead of the upper trough
arrives. Another round of stratus over the Panhandle is expected
by Thursday night.
.LONG TERM...(Friday through Tuesday)
Issued at 230 AM MDT Wed Sep 21 2016
Unsettled in the long term as low pressure tracks across the area.
Best chances for rain will be Friday and Saturday as the low
tracks across the area. By Saturday evening, the low will be east
of us in North Dakota with chances for precip ending.
It will be cold Sunday as 700mb temperatures fall to -4C across
the area. May not get out of the 50s for highs for many areas with
low temperatures in the 30s for many areas.
Warmer weather returning for the beginning of next work week.
Forecast looks dry as high pressure builds back into the area.
&&
.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1105 PM MDT Tue Sep 20 2016
VFR conditions for the most part. Could start seeing lowering
conditions in the northern Panhandle but confidence is not high.
Will wait and see what happens overnight.
&&
.FIRE WEATHER...
Issued at 230 AM MDT Wed Sep 21 2016
No fire weather concerns through the end of the week. Temperatures
will cool over the next few days, and especially after Friday behind
a cold front. Minimum afternoon humidity values will fall into the
20-30 percent range this afternoon. Further moistening will occur
on Thursday and Friday along with an increasing chance of showers
across portions of the region.
&&
.CYS Watches/Warnings/Advisories...
WY...None.
NE...None.
&&
$$
SHORT TERM...ZF
LONG TERM...GCC
AVIATION...GCC
FIRE WEATHER...ZF
Area Forecast Discussion
National Weather Service Marquette MI
518 AM EDT WED SEP 21 2016
.SHORT TERM...(Today and tonight)
Issued at 515 AM EDT WED SEP 21 2016
WV imagery and RAP analysis indicated a zonal pattern across most of
the nrn CONUS with the exception of a trough digging into the
Pacific Northwest. A shortwave riding along the 850 mb warm frontal
boundary and instability/strong moisture transport gradient at nose
of 30-35 kt 850 mb jet max has supported strong to severe t-storms
over western and central WI early this morning. Some stray showers
from this convective complex have made it into far south central
Upper Mi with MNM reporting some sprinkles/light showers last
evening into early this morning. Another weak shortwave rounding the
broad mid-upper level ridge has triggered a few t-storms over ern MT
and wrn ND. With the exception of the light -shra over the scntrl,
the rest of Upper Mi has remained dry early this morning under
influence of a sfc high pressure ridge over the area. Very dry
airmass over our area reflected in 00z APX and INL soundings with
very dry air noted from sfc up above 700 mb, and this will need to
be overcome before pcpn can occur over Upper Mi today and tonight.
Mid and high clouds have kept overnight temps warmer than last night,
generally in the mid 50s to lower 60s.
Today and tonight, Shortwave rounding the ridge over the Northern
Plains will work its way into the Upper Great Lakes this afternoon.
Models do show a corresponding increase in 305K isentropic ascent
and 850 mb moisture transport with gradual northward movement of the
850 mb warm front in response to the shortwave passage, especially
late in the afternoon into tonight which will likely support shower
development. However, with the relatively dry ne flow developing
north of the warm front below 850 mb, models (particularly the high-
res models) are trending slower with the northward advance of
developing pcpn and showing a sharper cut-off to pcpn over the nrn
sections of Upper Mi deeper into the dry air. As a result have
confined slight chc to low chc pops over the scntrl and wi border
counties this morning with a gradual increase in pops toward the ne
by late afternoon/evening. By late evening/overnight tonight
generally have likely to categorical pops over the south half of the
cwa with chc pops for the north half. Wouldn`t be surprised if the
Keweenaw Peninsula stayed mostly dry through period as some of the
models suggest as they will be farthest away from better
convergence/isentropic ascent along 850 mb warm frontal boundary and
from better 850 mb moisture transport. With MUCAPE values fcst into
the 500-1000 J/Kg over the far south late afternoon into this evening
some TS will also be possible and possibly a strong storm or two with
up to dime-sized hail given strong deep layer shear present. The
thickening clouds and developing ne low-lvl flow will limit highs
today to the mid 60s to lower 70s, warmest south and east. Lows
tonight will generally be in the 50s under persistent cloud cover.
.LONG TERM...(Thursday through Tuesday)
Issued at 432 AM EDT WED SEP 21 2016
An increasingly amplified pattern is still on track to develop
across N America for the remainder of this week into the weekend.
Ridge/positive height anomaly currently moving into nw Canada will
strengthen as it shifts across the Northwest Territories to Nunavut
by the end of the week. The magnitude of the positive height anomaly
at 500mb will reach 3 standard deviations above the long term late
Sept avg. To the s of this anomaly, a trof will amplify over the
western CONUS over the next few days, and the building downstream
ridge over the central CONUS will then link up with the n central
Canada positive height anomaly, leading to a sharp mid continent
ridge for a brief time. In response, trof over se Canada will deepen
and expand into the ne CONUS this weekend. This suggests that after
wet weather into Thu, a drier period should mostly dominate Fri/Sat
and potentially thru Sun as sfc high pres associated with the sharp
upstream ridge builds se into northern Ontario and the Upper Great
Lakes. Early next week, a more progressive flow regime should begin
to take shape again. Initially, building of a ridge into western N
America will send a shortwave se into the Upper Lakes later Mon/Tue.
This wave will incorporate at least some of the energy in the
western CONUS trof with the remainder dropping s. A period of shra
will accompany this shortwave across the area at some point Sun/Mon
with drying following for Tue. As for temps, readings will probably
not stray far from late Sept normals during this period.
Beginning Thu, last in a string of weak shortwave energy lifting ne
thru the western Great Lakes will move e of the area by late aftn.
Meanwhile, downstream of the western Canada ridge, a stronger
shortwave will drop into northern Ontario during the day and then
into Quebec Thu night. Following this wave, sfc high pres associated
with the sharpening mid/upper ridge in central Canada will build se
into northern Ontario Thu night, pushing frontal boundary extending
from the Plains to the Great Lakes southward. As a result, expect a
trend for shra Thu morning to diminish and/or end from nw to se
during the aftn thru Thu night.
With sfc high pres dominating northern Ontario on Fri and frontal
boundary/baroclinic zone shifted farther s and sw, expect a dry day.
Will need to watch development of pcpn into the northern plains
where strengthening southerly flow/isentropic ascent ahead of
western CONUS trof leads to an expanding pcpn area. Right entrance
upper divergence with a reoriented upper jet in a nw-se direction
across northern Ontario to New England could aid the expansion of
pcpn toward Upper MI late Fri or Fri night.
ECMWF has been most insistent on pcpn briefly streaking se into at
least western Upper MI Fri night into Sat underneath right entrance
of upper jet and within an eastward extension of isentropic ascent
from the northern Plains. GFS/CMC have been more varied on whether
or not the pcpn will reach the area, but since majority of GFS/CMC
ensembles support the streak of pcpn, fcst will reflect chc pops
spreading into the far w Fri night and expanding e into central
Upper MI Sat morning before pcpn area dissipates.
Fcst for Sun thru Tue is highly uncertain, much more than is
typically the case at this time range and no different from the last
few days. Over the last 4 days, medium range guidance has shown
considerable spread in what happens with the western CONUS trof and
how the flow evolves across southern Canada this weekend thru early
next week. The 00z GFS is back to showing a mid level low closing
off over the Upper Mississippi Valley/western Great Lakes early next
week, a solution that appeared once days ago though it got to that
solution in a different manner. At this point, consensus of recent
days guidance is for a shortwave which incorporates at least some of
the energy in the western CONUS trof to reach the area early next
week, but wouldn`t be surprised at all if something completely
different occurs. Maintaining some continuity with previous fcst,
will show chc pops spreading slowly e across the area Sun/Sun night,
lingering Mon then trending dry on Tue.
&&
.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 153 AM EDT WED SEP 21 2016
Although there wl be a good deal of mid clds at times and perhaps a
few -shra especially this aftn, dry llvl air wl ensure VFR conditions
prevail at all 3 TAF sites this fcst period. Thicker clds and more
numerous showers will arrive by this evng. While lingering near sfc
dry air wl likely maintain VFR conditions even if some showers
occur, MVFR conditions wl probably dvlp after 22/06Z.
&&
.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 515 AM EDT WED SEP 21 2016
Developing ne flow over Lake Superior with sfc trough moving into
Upper Mi and sfc ridge over Ontario could support some higher wind
gusts to 25 knots over the wrn half of the lake this afternoon into
Thu and across the entire lake Thu night into Fri. As the Canadian
high builds more over the Upper Lakes winds will dip blo 20 kts
Friday night into Saturday night. Southerly winds will increase late
Sunday into Sunday night to 25 to 30 knots over mainly the north
central and eastern part of the lake as a low pressure trough
approaches from the west.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...Voss
LONG TERM...Rolfson
AVIATION...KC
MARINE...Voss
Area Forecast Discussion
National Weather Service Omaha/Valley NE
339 AM CDT WED SEP 21 2016
.SHORT TERM...(today through Friday)
Issued at 330 AM CDT WED SEP 21 2016
Thunderstorm chances this afternoon through Thursday are the primary
forecast concerns this period. Warm temperatures to continue as well.
Upper flow pattern was beginning its change as strong westerlies
across the Northern Plains were progressing east as strong
low/trough dropped into the Pacific Northwest early Wednesday.
Southwest mid level flow will remain over the Central Plains through
tonight, then shortwave ridging will build into our region later
Thursday into Friday. Shortwave within southwest flow aloft is shown
currently by RAP analysis moving through eastern Colorado, heading
toward Nebraska and Iowa later today and tonight. Meanwhile quasi-
stationary surface front extended from northeast Colorado into
southeast South Dakota and western Wisconsin. This boundary will not
move a whole lot much of the day as upper flow parallels front,
waiting for surface low tied to upper shortwave to develop and move
from central Nebraska into northern Iowa this evening. Increased low
level convergence ahead of the low will help ignite storms this
afternoon, then southward drift of front will occur in its wake
helped along by convection.
Expect storms to take some time to get going later today as
inhibition is slowly eroded and where low level convergence is
maximized in northeast Nebraska and southeast South Dakota ahead of
surface low. Instability increases markedly from near 1500 j/kg of
MLCAPE in northeast Nebraska to closer to 2500 j/kg in northwest
Iowa as per GFS, so we may miss initial development northeast of our
area around 00Z. As the evening progresses, southward drift of
surface front behind low combined with increasing moisture transport
over that boundary as low level jet kicks up will bring our best
chance for convection. Appears the best conjunction of those
parameters will lie somewhere between Columbus and Norfolk,
northeast to between Wayne and Tekamah, and into Monona County Iowa.
Expect storms to fire somewhere in this zone by 03Z, then expand
east and west with time. Continued moisture feed into south and
southwest flank will lead to some propagation southward toward
Interstate 80 overnight, but storms south of the Interstate may be
hard to come by.
Certainly could see severe storms given degree of instability but
overall bulk shear is modest at best. Storms becoming more outflow
dominant and loaded with precipitation suggests damaging wind gusts
or microbursts are possible as well. Heavy rain is also likely given
high precipitable water values near 1.75 inches shown by GFS, and
potential for training storms.
Bulk of overnight activity will be pushing off to the east Thursday
morning. Overall mid level pattern of building shortwave ridge
across our area will support northward propagation of frontal
boundary, but will not clear our northern border until later
Thursday night. Thus redevelopment of convection appears likely
Thursday afternoon where models support 2000 j/kg of ML and SB CAPE
and Bulk Shear is near 30kt.
By Friday morning building heights and front lifting north should
leave most of eastern Nebraska and western Iowa under capping mid
level temperatures. Surface temperatures should reach the upper 80s
again most spots Friday afternoon. In fact much of eastern Nebraska
and western Iowa will average mid and upper 80s for highs each
afternoon today through Friday. While highs Tuesday reached the 90s
all areas, more cloud cover today will likely hold temps down a tad,
though areas along and south of Interstate 80 could top 90 again.
And Thursday afternoon northeast Nebraska will be north of
retreating front and may not reach 80 in some areas.
.LONG TERM...(Friday night through Tuesday)
Issued at 330 AM CDT WED SEP 21 2016
GFS and ECMWF are fairly consistent in showing upper low rotating
into the Northern Plains on Saturday with trough axis extending into
New Mexico. They are also fairly close in depicting plume of
tropical moisture streaming into our region Saturday then being
shoved east by Sunday evening. Those models then diverge quite a bit
beyond that, with GFS offering a deep closed cyclone over Wisconsin
solution by Tuesday, and ECMWF maintaining general trough over our
region. As far as sensible weather in concerned, we will be on the
cool side of the system with pockets of cold air aloft rotating
across the region. Some of these may spark some showers from time to
time, but the main weather story appears to be temperatures in the
60s or lower 70s for highs to start next week.
Leading up to that, we will see periods of showers and thunderstorms
Saturday into Sunday when moisture plume is on top of us. GFS again
is painting precipitable water values of 1.75-2.00 inches across our
area Saturday. Thus heavy rain remains a concern Saturday and
Saturday night before bulk of activity pushes off to the east.
&&
.AVIATION...(06Z TAFS for KOFK...KLNK and KOMA.)
Issued at 1215 AM CDT WED SEP 21 2016
High-level clouds will continue to spread east ahead of a low-
amplitude short-wave trough moving into the central Rockies.
Meanwhile, a nocturnal LLJ will strengthen through daybreak
Wednesday from the southern High Plains to mid Missouri Valley,
yielding LLWS through about 14z Wednesday at all three TAF sites.
Gusty south winds will once again materialize by Wednesday
afternoon ahead of a surface low developing from central into
northeast Nebraska. By Wednesday evening, the chance of
thunderstorms will increase at across eastern Nebraska.
&&
.OAX Watches/Warnings/Advisories...
NE...None.
IA...None.
&&
$$
SHORT TERM...Dergan
LONG TERM...Dergan
AVIATION...Mead
Area Forecast Discussion
National Weather Service Pocatello ID
305 AM MDT WED SEP 21 2016
.DISCUSSION...Moisture from a few different sources will work its
way into our region today, tomorrow and Friday. Moisture from a
shortwave trough is currently the dominant feature over our area,
and is providing isolated showers over Nevada. Additional moisture
includes tropical moisture and remnants from what was once
Hurricane Paine in the Eastern Pacific Ocean. Our widespread
rain/snow event will begin today with isolated and scattered rain
showers over the central mountains with increasing coverage by the
afternoon. Rainfall amounts will top out around 1/4 inch in these
areas for today, with 1 to 2 inches of snowfall at highest
elevations (of which is expected to increase to 2 to 4 inches
through Friday). For the Snake Plain areas and elsewhere, coverage
will increase greatly later this afternoon with lighter rainfall
amounts expected. Instability will be marginal this afternoon but
the greatest likelihood for thunderstorms looks to be over the
Eastern and Caribou Highland locations with a similar pattern
setting up for Thursday afternoon. As we go into the overnight
hours, rainfall will shift focus a bit to the east and south where
a decent chance, about 50%, to obtain 1/4 inch of rainfall exists
across the Southern Highlands.
Thursday morning shows another 50% chance for 1/4 inch of rainfall
in portions of the Southern Highlands, especially across the
southern Caribou-Targhee NF. For the rest of Thursday, look for
continued rain showers with a chance for thunderstorms with
increased coverage expected overnight into Friday morning.
Overall, for our area, highest rainfall accumulations look to be
setting up along the Idaho/Utah border including the cities of
Preston, Mink Creek, Malad City, Soda Springs. Rainfall amounts
will continue to be amended as rain begins to fall and the event
unfolds. Right now forecasts are calling for 2 to 4 inches across
this area over a 3-day period starting this afternoon. Snow may
fall at highest elevations in these areas as well Thursday with 1
to 3 inches possible through Friday. Other areas in Southeast
Idaho will see 1 to 2 inches of rainfall but we are pretty
confident everyone in the region will see a drop or two of
rainfall over this event.
A rather drastic temperature drop will occur Thursday and continue
into Friday. Be in store for 10 for 15 degree cooler high
temperatures tomorrow and an additional 5 to 10 degrees cooler on
Friday. Gradual recovery will occur over the weekend and next week
as high pressure builds into our region and the low exits to the
east. Lingering showers are forecast Saturday for the Eastern
Highland locations before ending Sunday. NP/RS
&&
.AVIATION...There is some convection developing in Nevada
this morning which the HRRR would move into KSUN around 14z this
morning and KBYI about 16Z. Less confidence in timing at KPIH but
little embedded bands in satellite imagery are moving east pretty
quick, gave the NAM the benefit of doubt. Moisture deepens and
ceilings lower quickly to MVFR tonight 05-07z time period for TAF
sites along the Snake Plain with the first lobe off the H7 low.
There may be a little period early morning with lighter rain, then
the next band develops mid to late morning with a second lobe coming
up, followed by a third Thursday afternoon. RS
&&
.FIRE WEATHER...Strong low pressure system is entering the Oregon
coast this morning and will track through north Nevada/Utah, then NE
into Wyoming. Isolated thunderstorms are expected this afternoon and
again on Thursday. The central mountains and Caribou should be
favored, but with the system moving across this area, forecast is
generally broad brushed with the potential. Models are consistent
with timing of heavier rain developing this evening and the pattern
remaining quite unsettled through about noon Saturday. Moderate to
heavy rain expected for all of Thursday and most of Friday.
Widespread 1 to 2 inches of rain is expected over the Wed night to
Sat afternoon time period and may be locally higher in the
mountains. RS
&&
.PIH Watches/Warnings/Advisories...
None.
&&
$$
Area Forecast Discussion
National Weather Service Tucson AZ
905 PM MST TUE SEP 20 2016
.SYNOPSIS...There is a chance of showers with a few thunderstorms
through Wednesday. A drying trend will begin Thursday and continue
into this weekend. However, a low pressure system over the southern
Rockies may generate a few showers and thunderstorms mainly east of
Tucson. Cooler temperatures will also occur this weekend.
&&
.DISCUSSION...Isolated showers and thunderstorms were moving
northward across the Tohono O`odham Nation west of Tucson at this
time. This area of showers and thunderstorms associated with a
perturbation moving northeastward into the area from northwest
Sonora as per water vapor satellite imagery has decreased in
coverage and intensity during the past hour. Otherwise, dry
conditions prevailed elsewhere this evening under mostly clear skies
to mostly cloudy skies.
The main forecast challenge into Wednesday is regarding precip
potential, and forecast confidence is not the highest due to some
recent hi-res model solutions. Have noted that HRRR solutions during
the past several hours depicted no rainfall west of Tucson this
evening, which was clearly not reality. For example, the Sells RAWS
has recorded 0.33 inch of rain since mid-afternoon. The AWIPS
version of the NAM12 also depicted no measurable rainfall thru
midnight. Have put slightly more credence in the 21/00Z Univ of AZ
WRF-NAM that does depict some measurable rainfall to occur west of
Tucson later tonight.
At any rate, given at least a marginally unstable environment as per
the 21/00Z KTWC sounding (MUCAPE of 484 J/kg) and similar values as
via the SPC Mesoscale Analysis, have maintained at least a slight
chance of showers and isolated thunderstorms the rest of tonight. A
chance of showers and isolated thunderstorms exists Wed especially
east of Tucson. This scenario is similar to the Univ of AZ WRF-NAM
and to some extent the NAM12. High temps Wed will be quite similar
to temps achieved this afternoon, or perhaps a few degs warmer
depending upon location.
Please refer to the additional sections for further detail.
&&
.AVIATION...Valid through 22/06Z.
Scattered -SHRA and isolated -TSRA with cloud decks generally from
8k-12k ft msl into Wednesday evening. Surface wind will be variable
in direction mostly less than 12 kts. Aviation discussion not
updated for TAF amendments.
&&
.FIRE WEATHER...There is a chance of showers and isolated
thunderstorms through Wednesday. A drying trend will start Thursday
and continue into this weekend. However, moisture will be sufficient
for a slight chance of showers and thunderstorms east of Tucson. 20-
foot winds will be mainly terrain driven less than 15 mph through
Wednesday, then west to southwest breezes to occur Thursday and
Friday afternoons.
&&
.PREV DISCUSSION /210 PM MST/...Water vapor imagery continues to
show high pressure well to our east and is now over west Texas, with
the ridge extending northeast into northern Texas and southwest
Oklahoma. Meanwhile, a weak trough resides just off the southern
California coast. Tropical storm Paine continues to move up the west
coast of the Baja peninsula and is expected to continue to weaken as
it eventually is expected to move inland across the north central
Baja peninsula by late Wednesday afternoon as a remnant low, based
on the latest official track/forecast from the NHC, which was issued
at 8 AM PDT.
IR satellite imagery shows extensive cloudiness across much of the
Desert Southwest, although the most enhanced cloudiness is currently
over southern Utah, northern Arizona and into southern California.
Taking a look at radars from KIWA, KEMX and KYUX indicate that the
bulk of the showers extend from coastal areas of southern California
into west central Arizona and towards the Flagstaff area. There are
some showers extending a bit farther south across the southwestern
deserts between Gila Bend and and Yuma, but all of this activity is
moving generally north. That said, it is looking like we will
struggle to see even scattered type POPs for my forecast area for
the remainder of this afternoon and perhaps even into the late
evening as the focus currently remains well to the west and north of
my forecast area. However, there is some enhancement in IR imagery
well to the northeast of Paine over the north central Baja peninsula
and the northern Gulf of California. With plenty of moisture to our
south we should eventually see shower development, but I pushed it
back to mainly after midnight tonight. Even then, think we will only
see isolated to low end scattered activity during that time, so the
bulk of shower activity for my forecast area should occur overnight
tonight and during the day Wednesday as the weak trough moves
through Arizona.
Once the remnants of Paine become absorbed into the weak trough and
eject northeast Wednesday, another upstream major trough will be
over the Pacific Northwest and will dive into the Great Basin by
late Thursday. As a result, expect a lingering threat for mostly
isolated showers and thunderstorms for deserts/valleys and low end
scattered type POPs for mountains on Thursday.
By late in the day Friday this system is progged to be over the
central Rockies, with the tail end of this system into northern
Arizona. So, expect slight chance of showers/thunderstorms
continuing Friday.
By Saturday the low should be in the general vicinity of the four
corners or northern New Mexico with enough dry air punching in
behind it for a dry forecast. However, beyond Saturday the models
begin to show significant differences, such that the GFS is quite
wet just to our east and along the New Mexico border whereas the
ECMWF has the trough/low farther south and east, instead of a closed
low over Arizona. For now I kept or included a chance of showers and
thunderstorms along the border with New Mexico for Sunday into
early next week.
For Tucson, high temperatures will be near normal for Wednesday and
Thursday, then 5 to 7 degs below normal each day thereafter. Low
temps will be 2 to 4 degs above normal, although the warmest morning
will be tonight/Wednesday morning. For Saturday through Tuesday
mornings, lows will range from 4 to 6 degs below normal.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...None.
&&
$$
Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson
Area Forecast Discussion
National Weather Service Las Vegas NV
927 PM PDT TUE SEP 20 2016
.SYNOPSIS...Weather will remain cool and unsettled through the end
of the week as remnant tropical moisture interacts with a trough
pushing in from the west. As the trough moves in
Thursday...increasing winds and the arrival of drier air will aid in
dangerous fire conditions for some areas along with strong
Thunderstorms in Northwest Arizona and eastern Nevada. Temperatures
will remain cool through Friday before returning to near normal
over the weekend.
&&
.UPDATE...The remains of the weak circulation center from what was
once a southern California upper low was moving across southern
Nevada this evening. The inland progression of this feature has
helped enhance a band of light to moderate rain showers extending
from near Twentynine Palms up to southern Clark County.
Precipitation amounts were generally less than 0.10". The latest
HRRR composite reflectivity forecast indicates the potential for
isolated to scattered light showers extending up across Lake Mead
into northern Mohave County. We could still see a few sprinkles in
the Las Vegas Valley before midnight. However...it will be most
favorable for measurable rain generally from I-40 southward. The
PoP/WX grids were updated to reflect the latest trends and remove
the general mention of thunderstorms through Wednesday morning.
-Adair
&&
.PREV DISCUSSION...
220 PM PDT TUE SEP 20 2016
SHORT TERM...Through Tonight.
Three systems are currently affecting the southwestern U.S. The
first is the rapidly dying Tropical Cyclone (TC) Paine, with
moisture from it streaming well north of its center west of the Baja
Peninsula. The second is an upper-level low slowly moving
northeastward onto the Pacific Coast near San Diego. The third is an
elongated vorticity maximum to the northeast of this upper low
stretching from San Bernardino County northeast to southern Utah and
southwest Colorado. Much of the precipitation in our CWA today has
been associated with this elongated vort max, aided by the moist
advection from TC Paine. However, this afternoon, precipitation has
developed/increased in intensity in closer proximity to the upper
low near San Diego. A quasi-zonally oriented band of rain showers
has developed in southwest Mohave County and southern San Bernardino
County in advance of this upper low. Precipitation rates have
increased somewhat within this band. The HRRR has not handled this
band particularly well this afternoon. Only recently has it caught
onto the idea of its persistence/somewhat stronger intensity, and it
continues to waver on its evolution through this evening. The latest
run shows more convective-type showers continuing northeastward
through southern Mohave County through 00Z Wednesday before rapidly
progressing out of the area. Meanwhile, the western portion of the
band remains anchored to the San Bernardino Mountains and Coachella
Valley before rapidly progressing northeastward and diminishing
somewhat in association with the track of the upper low. This seems
to be a reasonable solution given the proximity to the two vort
maxima; however, given the variability seen with this evolution
simulation to simulation -- not overly confident of this.
PoPs were tweaked but remain consistent with this morning`s update,
in general. Think outside of a few sprinkles, the Las Vegas Valley
will probably not see rain, so kept PoPs confined to south/east of I-
15 through the night. Most of the heavier precip in Mohave County
should end by midnight with lighter showers possible thereafter.
Instability has been meager to nonexistent today, so even an
isolated lightning strike is not particularly likely. Nevertheless,
the increasing precipitation intensities this afternoon and the
stronger lift associated with the passing upper low led me to keep
slight thunder chances in through the night.
&&
LONG TERM...Wednesday through Monday.
Remnant moisture from Tropical depression Paine will remain in play
across the region on Wednesday beneath a broad southwesterly flow
aloft. Some cooling aloft and slightly greater sunshine potential
should allow for some marginal destabilization tomorrow afternoon
which will support the probability of greater thunderstorm coverage
across the region tomorrow as opposed to the more stratiform
precipitation event we are observing today. However, instability
will still not be very impressive and the greatest chance for
thunderstorms will be across the great Basin closer to the
approaching trough...and across Northwest Arizona.
On Thursday, a strong and dynamic trough will push into the Great
Basin region with the base of the trough dragging across our
forecast area. The impacts with this system will be two fold, strong
winds and fire danger will be one concern. While Heavy rain and
thunderstorm potential will be another concern. As far as wind and
fire goes, a dry slot in the lower levels and subsidence on the back
side of the trough will promote strong drying and downward momentum
transport to support widespread winds across much of the Mojave
Desert and low relative humidity values. Winds may require their own
headlines in subsequent updates but felt confident enough in the
fire danger to go out with a fire weather watch for much of San
Bernardino county and Clark County, as well as the Colorado River
for Thursday afternoon. We may see wind gusts exceeding 40 mph
across much of the same areas during this time. As usual with wind
events, blowing dust can be expected as the winds pick up during the
day Thursday.
Meanwhile....across Northwest Arizona and mainly eastern Lincoln
county, strong thunderstorms will be a possibility on the west edge
of remnant moisture and instability from Paine. Southwesterly shear
will be quite impressive with over 65kts of shear forecast at 500mb
and a fairly unidirectional profile. This would favor both strong
convection as well as training convection ahead of the trough. Some
models are suggesting the potential for fairly significant QPF
across northern Mohave county Thursday afternoon so flash flood
potential will need to be monitored as the event approaches.
Conditions will improve Friday as the trough pushes eastward and
high pressure attempts to build back in but temperatures will remain
cool...averaging 10 to 15 degrees below normal. Less confidence in
the longer range period extending from this weekend into next week
as the ECMWF builds a large ridge into the region while the GFS
retrogrades some trough energy into Arizona which would keep us
cooler with possible north winds especially down the Colorado River.
For now maintained a dry forecast with temperatures gradually
returning to near normal.
&&
.FIRE WEATHER...Strong winds and low humidity will combine forces
to create a period of critical fire weather conditions Thursday
afternoon. Fuels remain very dry especially north of I-40 which will
see little benefit from the remnant moisture of tropical depression
Paine. Fire weather watches are in effect for the San Bernardino
County deserts, much of the lower elevations of Clark County, the
lower Colorado River valley and Lake Mead NRA. Improving conditions
are expected friday as the winds relax.
&&
.AVIATION...For McCarran...Winds will be light and diurnally driven
overnight and Wednesday morning until stronger SW winds kick in by
late Wednesday afternoon. A slight chance of storms tomorrow
afternoon/evening.
For the rest of southern Nevada...northwest Arizona...and southeast
California...Showers and ceilings near/below 10 kft will continue
this evening for eastern San Bernardino and southern/eastern Mohave
Counties. Some ceiling improvement is expected by late tonight.
Scattered showers and mountain obscurations are possible in the
Sierra this evening. Winds look to be predominantly S/SE through
tomorrow morning, with speeds generally below 12 kts. Chances of
storms exist tomorrow afternoon, especially near higher terrain,
with stronger S/SW winds commencing by late afternoon.
&&
.SPOTTER INFORMATION STATEMENT...Shower and thunderstorm chances
continue through Thursday. Strong winds are also expected in much of
the area Thursday afternoon and evening. Spotter activation may be
required Wednesday afternoon through Thursday. &&
$$
Short Term/Aviation...Shafer
Long Term/Fire Weather...Outler
For more forecast information...see us on our webpage:
http://weather.gov/lasvegas or follow us on Facebook and Twitter
Area Forecast Discussion
National Weather Service Gaylord MI
1055 AM EDT WED SEP 21 2016
.UPDATE...
Issued at 1055 AM EDT Wed Sep 21 2016
Overview: Surface low pressure analyzed over the central plains
with a warm front arcing across southern Minnesota then down into
the lower lakes region. EML/plume of very steep mid level lapse
rates (pushing 8C/KM) stretches from the central plains and just
into the northern plains and upper Mississippi River Valley.
Strong low level moisture transport/pooling along and south of the
front has pushed dewpoints into the 70s across parts of the
Midwest and a few thousand J/KG of MLCAPE. Instability decreases
rapidly heading into northern Michigan with just a few hundred
J/KG MUCAPE poking into the far S/SW counties.
Ongoing MCS/squall line that developed in srn Minnesota overnight
now diving ESE through lower Michigan with the northern fringe of
a well defined MCV skirting the M-55 corridor. But heart of convection
is diving S/E away from this CWA along the aforementioned instability
gradient. Another batch of showers/storms has developed over srn
Wisconsin but will also stay well south of our area.
Rest of today and tonight: Northern Michigan once again sitting
in "no mans land" with ongoing convection to the south and lighter
precip ongoing across the far northern plains along tight
baroclinic zone on the southern side of the upper jet. Upstream
warm front will very slowly lift northward through tonight with
moisture/instability plume slowly nosing into the region. But by
far, best moisture/instability and low level convergence remains
to our west. There will be renewed showers/storms across the upper
Mississippi River Valley later today through tonight that will
eventually get into our area. But that`s several hours away.
So, after this mornings precip, have diminished pops for the
afternoon into early evening and reworked the Hazardous Weather
Outlook.
&&
.SHORT TERM...(Today and tonight)
Issued at 255 AM EDT Wed Sep 21 2016
High pressure continues to exit east away from Michigan as a warm
front/inverted trough lifts northward into the Upper Mississippi
Valley and far Western Great Lakes region. Main area of convection
associated with this feature is currently impacting SE Minnesota and
SW Wisconsin. Another area of much weaker convection/shower activity
has made some eastward progress out of the Green Bay area across
Lake Michigan into our SW CWA...but is having some difficulty
overcoming the dry low level air entrench over our CWA. Both MBL and
FKS have reported some light rain periodically reaching the ground
early this morning...but no thunder has occurred due to a serious
lack of instability attm.
Latest HRRR and RAP13 both depict this light precip across our SW
CWA attm...while the latest NAM12 shows nothing. HRRR/RAP13 solution
steadily dissipates this light precip by around sunrise early this
morning...as focus for convective development remains further to the
SW along the nrn periphery of the instability axis and 850 mb theta
E ridge. All of the latest runs of the short term models continue to
favor this area for best convective development throughout the day
around the northern extent of the inverted trough. They do lift this
favored are into our SW CWA later this afternoon and evening...
suggesting our better chance for POPs will be during this time.
MUCAPES increasing to near 2000 J/kg and 0-3 kg bulk shear values
increasing to around 30 kts would also suggest a marginal risk of a
few strong to possibly borderline severe storms during this time as
well (in agreement with latest SPC Day 1 outlook).
Have backed off just a bit on pops for much of today...opting to
develop higher pops from late afternoon into tonight as better
instability and moisture finally begin to push NE into our CWA along
the northern edge of the inverted trough axis. Will certainly
maintain the chance of thunder as well...but latest model trends
have delayed the possibility for heavy rainfall until Thursday. Above
normal temps will continue today despite increasing clouds...with
afternoon highs ranging from the lower 70s in Eastern Upper Michigan
to the mid to upper 70s across Northern Lower Michigan. Low temps
tonight will cool back into the mid 50s to lower 60s.
.LONG TERM...(Thursday through Tuesday)
Issued at 255 AM EDT Wed Sep 21 2016
Thursday through Friday night...
High impact weather potential: Embedded thunderstorms and
locally heavy rain possible through Thursday evening.
Pattern synopsis/Expected evolution: A strong 130+ kt northern
stream jet streak is draped across southern Canada, nearly
encompassing the entire width of North America. The main focus will
revolve around two pieces of energy converging toward the Great
Lakes region midweek. The first is expected to pinwheel from western
Canada toward southern Ontario by Thursday. The second, currently
ejecting from the four corners region toward northern Michigan
during the same timeframe. The second wave is progged to continue to
trek northeastward toward the Great Lakes, resulting in low pressure
development across the central plains, bringing increased precip
chances across the MS Valley and Great Lakes region Wednesday
afternoon through at least the first half of Friday.
Guidance continues to suggest a rather impressive baroclinic zone
setting up across the northern Great Lakes into southern Ontario by
Wednesday night through the end of the week into the upcoming
weekend as the aforementioned weakly organized low pressure slides
toward the northeast, draping a warm front across the region.
As a result, potentially locally heavy rainfall will be the main
concern.
Thursday - Thursday night: By Thursday morning, deep layer moisture
is nearing its maximum for the event across northern Michigan with
PWs approaching 1.75 inches. As mentioned yesterday, if a value of
1.75 inches were to verify, it would be 1.00 inch higher than the
daily mean and ~0.50 inch greater than the highest recorded PW for
Sept. 22 via SPC`s sounding climatology for APX. With nearly
unidirectional flow through roughly 200mb, the threat for locally
heavy rainfall remains a concern. By Thursday night, surface high
pressure noses into the northern Great Lakes from Canada allowing
drier air to filter in and gradually diminishing precip chances from
north to south late Thursday night through the first half of Friday.
Friday - Friday night: Precip continues to diminish as northern
Michigan lies on the southern periphery of an expansive area of high
pressure centered over northern Ontario. It could end up feeling
like a rather brisk fall day with occasionally gusty winds, mostly
cloudy skies, and much cooler temperatures filtering into the
region (high temps for many locations struggling to top the mid-60s).
Saturday through Tuesday...
Despite a similar flavor to the overall pattern, global model
guidance varies beyond Friday night in terms of sensible weather
across the area. At this point, will hedge the forecast toward the
drier of the two solutions with Canadian high pressure moving very
little through the end of the weekend. Toward the very tail end of
the extended period, low pressure moves from the northern plains
into the southern Canada resulting in increasing precipitation
chances Monday night-Tuesday as a cold front swings through the
Great Lakes. High temperatures in the 60s throughout the extended
period, which falls within a degree or two on either side normal for
the last week of September.
&&
.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 645 AM EDT Wed Sep 21 2016
Chances of showers and thunderstorms will slowly increase from
west to east today and tonight as a warm front/inverted trough and
associated instability and deep moisture gradually edge into
Lower Michigan over the next 24 hrs. Low levels remain rather
dry...so this process will take some time. Overall conditions will
remain VFR despite increasing chances of precip...but cigs and
vsbys will temporarily decrease to MVFR/possibly IFR within
heavier showers and storms. Overall wind regime will remain
light...lending to lake breeze development this afternoon.
&&
.MARINE...
Issued at 255 AM EDT Wed Sep 21 2016
Winds and waves will remain below SCA criteria thru Thursday night.
However...chances of showers and thunderstorms will increase today
and especially tonight and Thursday as an inverted trough/warm front
slowly lifts into the Western Great Lakes region. Best chance for
precip will initially be over Lake Michigan today...with better
chances spreading eastward tonight into Thursday.
&&
.APX Watches/Warnings/Advisories...
MI...NONE.
LH...NONE.
LM...NONE.
LS...NONE.
&&
$$
UPDATE...Adam
SHORT TERM...MLR
LONG TERM...Gillen
AVIATION...MLR
MARINE...MLR
Area Forecast Discussion
National Weather Service Cheyenne WY
506 AM MDT WED SEP 21 2016
.SHORT TERM...(Today through Thursday night)
Issued at 230 AM MDT Wed Sep 21 2016
Mid to high level clouds continue to stream across the southeastern
half of the CWA. Although the global models do not show much
precip through midday, the HRRR does show light showers in areas
along the Colorado Border. Thus, maintained slight chance pops
through the morning. With the dry llvls, not expecting much more
than sprinkles or very light rain showers. Temps today will be
5-10 degrees cooler than Tuesday in most locations. A cold front
will back into the Nebraska Panhandle overnight with widespread
low clouds developing after 06-09Z over much of the Panhandle and
extreme southeast WY. Put some patchy fog into the northern
Nebraska Panhandle with upslope northeasterly sfc winds along the
Pine Ridge.
Low clouds will be persistent across portions of the plains
through the morning on Thursday. The coolest highs (mid to upper
60s) will be over the northern Nebraska Panhandle where some low
clouds could persist through the entire aftn. South to
southeasterly winds will become breezy by the aftn and early
evening over much of the CWA. Kept 20-40 percent pops mostly
confined to areas west of the Laramie Range through the aftn as
the atmosphere will be capped/stable over the plains. Could see a
slightly better coverage of showers and isolated tstms into
Thursday night as the better forcing ahead of the upper trough
arrives. Another round of stratus over the Panhandle is expected
by Thursday night.
.LONG TERM...(Friday through Tuesday)
Issued at 230 AM MDT Wed Sep 21 2016
Unsettled in the long term as low pressure tracks across the area.
Best chances for rain will be Friday and Saturday as the low
tracks across the area. By Saturday evening, the low will be east
of us in North Dakota with chances for precip ending.
It will be cold Sunday as 700mb temperatures fall to -4C across
the area. May not get out of the 50s for highs for many areas with
low temperatures in the 30s for many areas.
Warmer weather returning for the beginning of next work week.
Forecast looks dry as high pressure builds back into the area.
&&
.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 502 AM MDT Wed Sep 21 2016
VFR for all TAF sites through the day. Tonight though, we see
northeast upslope winds that will begin to bring lowering ceilings
into the Panhandle. Started off MVFR at KCDR, KAIA and KBFF.
Later shifts may need to lower to IFR as the event draws closer.
&&
.FIRE WEATHER...
Issued at 230 AM MDT Wed Sep 21 2016
No fire weather concerns through the end of the week. Temperatures
will cool over the next few days, and especially after Friday behind
a cold front. Minimum afternoon humidity values will fall into the
20-30 percent range this afternoon. Further moistening will occur
on Thursday and Friday along with an increasing chance of showers
across portions of the region.
&&
.CYS Watches/Warnings/Advisories...
WY...None.
NE...None.
&&
$$
SHORT TERM...ZF
LONG TERM...GCC
AVIATION...GCC
FIRE WEATHER...ZF
Area Forecast Discussion
National Weather Service Lincoln IL
949 AM CDT WED SEP 21 2016
.UPDATE...
Issued at 936 AM CDT Wed Sep 21 2016
Convective issues causing a challenging forecast for today.
Outflow boundary, from the earlier line of storms which passed
through Chicago, is currently approaching Galesburg, Peoria and
Bloomington from the northeast. This caused the line to weaken
rather quickly as it began to outrun the line. However, convection
from Wisconsin has now settled into far northern Illinois in an
west-east configuration in the border counties. HRRR has been
struggling to handle the storms over the last several hours, and
has this secondary line weakening as well before reaching us.
Forecast was updated earlier to add some 20-30% PoP`s across the
far northern CWA for a few hours this morning, which appears
sufficient for now. Will monitor the secondary line for a couple
hours to see if any additional PoP`s need to be added for midday
or afternoon.
Temperatures will also be a challenge as well, between the
outflows and the cirrus shield from the decaying MCS to our north.
Already up to 80 degrees across the far southwest CWA, which is
in line with the previous forecast. Have made some adjustments to
the hourly trends across the north to reflect the outflows and
increased cirrus, but the remainder of the forecast area still
expected to get to near 90.
&&
.SHORT TERM...(Today and tonight)
ISSUED AT 325 AM CDT Wed Sep 21 2016
The recent stretch of unseasonably warm weather will persist across
central and southeast Illinois today (and several more days
actually). These warm conditions will be supported by persistent
southerly low-level flow and the continued building locally of a
flat upper-level ridge. Based on yesterday`s high temperatures and
minimal airmass change, boosted today`s highs into the 90s areawide.
The airmass has become more humid over the past 24 hours and may
not heat quite as quickly today, suggesting going even warmer for
highs today would not be prudent.
Aside from the heat, only other concern of note this period is the
threat for showers/storms across the north. A storm complex is
currently chugging across the upper Midwest, and it has shown some
tendency to turn toward the right into the richer
moisture/instability. Some guidance suggests outflow from this
complex may fire off a few storms across our far northern counties
later today or this evening. At this point, think it will be a close
call, but favor keeping forecast dry with any activity staying just
north of the area. Convective trends will need to be monitored
closely today in any event.
.LONG TERM...(Thursday through Tuesday)
ISSUED AT 325 AM CDT Wed Sep 21 2016
Forecast remains unseasonably warm and dry for the rest of the week
in Central Illinois. Temps in the mid to upper 80s through the
weekend. With the persistent delaying of onset of precip with the
next system...think the guidance is actually going a little low on
the max temps this weekend and think the forecast will trend to near
90 in some locations for Fri/Sat.
Main issue with the forecast remains the trof that moves into the
west coast on late Thu/Fri. The models have been modulating back
and forth btwn phasing the wave into the northerly synoptic stream
and producing a more cut off low over the SW, delaying the onset of
precip to the Midwest. Latest GFS and ECMWF runs are more of a
hybrid, progressing a weakly phased wave across the Plains, and
almost stalling in the mid Miss River Valley for late in the
weekend/beginning of next week. As a result, the pops start up Sun
night and continue through at least Tuesday at this point. With the
models struggling with the pattern shift overall, pops are confined
to 20-30 percent for now. After the system arrives Monday...temps
cool off considerably with the trof.
&&
.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 635 AM CDT Wed Sep 21 2016
Generally quiet/VFR aviation weather conditions expected across
the central Illinois terminals through the 12Z TAF valid time. The
only potential exception would be if some convection manages to
fire across parts of the area along an approaching outflow
boundary from northern Illinois. This would mainly be a threat at
KPIA, KBMI, or KCMI, but feel chances of TSRA are too low to
mention at this time.
&&
.ILX Watches/Warnings/Advisories...
NONE.
&&
$$
UPDATE...Geelhart
SHORT TERM...Bak
LONG TERM...HJS
AVIATION...Bak
Area Forecast Discussion
National Weather Service Northern Indiana
1154 AM EDT Wed Sep 21 2016
.SYNOPSIS...
Issued at 318 AM EDT Wed Sep 21 2016
Above normal temperature will continue into at least Thursday with
highs well into the 80s both days. Shower and thunderstorm chances
may return by Sunday as a frontal boundary to the north sinks into
the area and a slow moving front moves towards the area from the
west. More seasonable temperatures can be expected next week.
&&
.UPDATE...
Issued at 1146 AM EDT Wed Sep 21 2016
Upstream convective complex fell apart as expected with just a few
showers entering the northwest. 14z HRRR is now trying to develop
some convection across NW Indiana with outflow from convection.
SPC Mesoanalysis does show a capped but slightly unstable
environment and any outflow could spark a storm or two if weak
capping erodes. Have updated to include slight chance pops from
the US 30 corridor northward over at least central and western CWA
for this afternoon. Once debris cloudiness thins temps should
rebound later this afternoon to near 80 north and lower to middle
80s south.
&&
.SHORT TERM...(Today and Tonight)
Issued at 318 AM EDT Wed Sep 21 2016
Another warm day will be in store for the region as frontal boundary
re-establishes itself across southern Lower Mi and eventually shifts
north. As advertised, convection quickly blossomed across SE
Minnesota and quickly went upscale. 40 to 45 kt LLJ was focused ahead
of the convection allowing for continued maintenance of a bowing
segment taking aim on La Crosse WI as well as a large area of
rain/embedded storms across central WI. Convection across central WI
should continue east and likely weaken as it outruns best low level
support. Storms over SE MN/WCtrl WI into NE IA will continue to drop
SE and remain elevated keeping overall severe threat minimal. For
our area specifically it would appear that any convective threat has
been nearly eliminated. Only lingering concerns is unstable
atmosphere across W/NW areas where CAPE values will push into the
1500 to 2000 J/KG range. If an outflow boundary emanates from the
convection and moves into this area this afternoon, could see some
isolated convection. However confidence very low in this scenario so
no addition of storms with punt to day shift to monitor trends.
Highs will reach into the lower to middle 80s with somewhat
higher humidity values.
&&
.LONG TERM...(Thursday through Tuesday)
Issued at 318 AM EDT Wed Sep 21 2016
Proximity of key features would tend to suggest that the forecast
area will remain high and dry into at least Sunday with highs well
into the 80s Thursday and possibly Friday. Frontal boundary will
remain draped north of the area with complexes of storms moving
along it through Friday before main focus shifts to the west with
stout trough and cutoff low that will meander towards the region
next week to bring increasing chances for precipitation and what
appears to be the potential for a shot of colder air with MEX
guidance showing highs only in the lower to middle 60s by Wednesday.
Grids to not reflect that drastic a difference as ECMWF remains
slower and not quite as deep on the trough. After several days of
above normal temps certainty exists on a return to near if not below
normal temps next week. How fast this occurs remains to be seen.
&&
.AVIATION...(For the 12Z TAFS through 12Z Thursday Morning)
Issued at 655 AM EDT Wed Sep 21 2016
Wk/ill defined frontal zone will refocus through cntrl lower MI this
afternoon northward of surface ridge centered just north of the OH
river. Expect surface winds to veer southerly by mid morning and
remain blo 10 kts. Otherwise vfr conditions through the period.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...NONE.
&&
$$
UPDATE...Lashley
SYNOPSIS...Fisher
SHORT TERM...Fisher
LONG TERM...Fisher
AVIATION...T
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Area Forecast Discussion...UPDATED
National Weather Service Baltimore MD/Washington DC
1013 AM EDT Wed Sep 21 2016
.SYNOPSIS...
High pressure will build over the region through Thursday. A cold
front will move through the area Saturday. High pressure builds
again over the region early next week.
&&
.NEAR TERM /THROUGH TONIGHT/...
GFS not doing particularly well with extent of high clouds this
morning. ECMWF and HRRR simulated cloud imagery doing much better
and have followed their output closely. Expect current extent of
high clouds to remain pretty much as is through midday with
thining of high clouds in the afternoon and clouds shifting south
and east by evening. Adjusted temps a bit based on model trends
from ECMWF indicating a 2-3 deg rise from yesterday in the east
with temps west of the Blue Ridge not showing any trend at all
from yesterday. Showers to graze southern St. Marys county through
the day with precip shifting south tonight.
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
Onshore NEly flow persists Thursday with above normal temperatures,
mid 80s, under mostly sunny skies as cloud shield looks to be along
southern periphery of the CWA.
Surface high pressure settles south over the area Friday with sunny
skies and light/variable winds. Maxima mid to upper 80s.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
A transition to autumn weather will occur over the weekend after a
cold front tracks down from the north Saturday afternoon. This is
a dry trajectory...so don`t expect much if any rainfall with this
system. After reaching 80 degrees Saturday it does not appear the
area will be seeing that for the next several days. Sunday highs
will likely only reach the mid 70s but the real story will be
Sunday night/Monday morning when lows east of the mountains will
drop into the lower 50s...and likely 40s in the Highlands.
By Tuesday some warming to the atmosphere should take place ahead
of a cold front. This will likely provide the next chance for rain
to the Mid Atlantic.
In somewhat of a coincidence..at IAD both since Sep 1 and Jan 1
the precipitation departure from normal is -2.21".
&&
.AVIATION /14Z WEDNESDAY THROUGH SUNDAY/...
High cloud shield persists over the area from low pressure
lingering along the NC coast. This is limiting fog development
across the DC metros. Best fog chance through sunrise is at MRB
though high clouds are currently over that area too.
VFR conds prevail through Friday high pressure slowly settles south
over the area.
VFR conditions expected this weekend.
&&
.MARINE...
NEly flow 10-15kt down the main portion of the Bay through Thursday
as low pressure lingers along the Carolina coast. Weak Nly flow
Thursday night through Friday as high pressure settles south over
the area.
Winds could increase to near SCA values near/behind a cold front
Saturday into Sunday.
&&
.TIDES/COASTAL FLOODING...
Elevated water levels persist through the rest of the week due to
low pressure off the Carolina coast. Coastal flooding threat is low
through Friday.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...None.
&&
$$
PRODUCTS...BAJ/WOODY!/LFR
Area Forecast Discussion
National Weather Service Marquette MI
655 AM EDT WED SEP 21 2016
.SHORT TERM...(Today and tonight)
Issued at 515 AM EDT WED SEP 21 2016
WV imagery and RAP analysis indicated a zonal pattern across most of
the nrn CONUS with the exception of a trough digging into the
Pacific Northwest. A shortwave riding along the 850 mb warm frontal
boundary and instability/strong moisture transport gradient at nose
of 30-35 kt 850 mb jet max has supported strong to severe t-storms
over western and central WI early this morning. Some stray showers
from this convective complex have made it into far south central
Upper Mi with MNM reporting some sprinkles/light showers last
evening into early this morning. Another weak shortwave rounding the
broad mid-upper level ridge has triggered a few t-storms over ern MT
and wrn ND. With the exception of the light -shra over the scntrl,
the rest of Upper Mi has remained dry early this morning under
influence of a sfc high pressure ridge over the area. Very dry
airmass over our area reflected in 00z APX and INL soundings with
very dry air noted from sfc up above 700 mb, and this will need to
be overcome before pcpn can occur over Upper Mi today and tonight.
Mid and high clouds have kept overnight temps warmer than last night,
generally in the mid 50s to lower 60s.
Today and tonight, Shortwave rounding the ridge over the Northern
Plains will work its way into the Upper Great Lakes this afternoon.
Models do show a corresponding increase in 305K isentropic ascent
and 850 mb moisture transport with gradual northward movement of the
850 mb warm front in response to the shortwave passage, especially
late in the afternoon into tonight which will likely support shower
development. However, with the relatively dry ne flow developing
north of the warm front below 850 mb, models (particularly the high-
res models) are trending slower with the northward advance of
developing pcpn and showing a sharper cut-off to pcpn over the nrn
sections of Upper Mi deeper into the dry air. As a result have
confined slight chc to low chc pops over the scntrl and wi border
counties this morning with a gradual increase in pops toward the ne
by late afternoon/evening. By late evening/overnight tonight
generally have likely to categorical pops over the south half of the
cwa with chc pops for the north half. Wouldn`t be surprised if the
Keweenaw Peninsula stayed mostly dry through period as some of the
models suggest as they will be farthest away from better
convergence/isentropic ascent along 850 mb warm frontal boundary and
from better 850 mb moisture transport. With MUCAPE values fcst into
the 500-1000 J/Kg over the far south late afternoon into this evening
some TS will also be possible and possibly a strong storm or two with
up to dime-sized hail given strong deep layer shear present. The
thickening clouds and developing ne low-lvl flow will limit highs
today to the mid 60s to lower 70s, warmest south and east. Lows
tonight will generally be in the 50s under persistent cloud cover.
.LONG TERM...(Thursday through Tuesday)
Issued at 432 AM EDT WED SEP 21 2016
An increasingly amplified pattern is still on track to develop
across N America for the remainder of this week into the weekend.
Ridge/positive height anomaly currently moving into nw Canada will
strengthen as it shifts across the Northwest Territories to Nunavut
by the end of the week. The magnitude of the positive height anomaly
at 500mb will reach 3 standard deviations above the long term late
Sept avg. To the s of this anomaly, a trof will amplify over the
western CONUS over the next few days, and the building downstream
ridge over the central CONUS will then link up with the n central
Canada positive height anomaly, leading to a sharp mid continent
ridge for a brief time. In response, trof over se Canada will deepen
and expand into the ne CONUS this weekend. This suggests that after
wet weather into Thu, a drier period should mostly dominate Fri/Sat
and potentially thru Sun as sfc high pres associated with the sharp
upstream ridge builds se into northern Ontario and the Upper Great
Lakes. Early next week, a more progressive flow regime should begin
to take shape again. Initially, building of a ridge into western N
America will send a shortwave se into the Upper Lakes later Mon/Tue.
This wave will incorporate at least some of the energy in the
western CONUS trof with the remainder dropping s. A period of shra
will accompany this shortwave across the area at some point Sun/Mon
with drying following for Tue. As for temps, readings will probably
not stray far from late Sept normals during this period.
Beginning Thu, last in a string of weak shortwave energy lifting ne
thru the western Great Lakes will move e of the area by late aftn.
Meanwhile, downstream of the western Canada ridge, a stronger
shortwave will drop into northern Ontario during the day and then
into Quebec Thu night. Following this wave, sfc high pres associated
with the sharpening mid/upper ridge in central Canada will build se
into northern Ontario Thu night, pushing frontal boundary extending
from the Plains to the Great Lakes southward. As a result, expect a
trend for shra Thu morning to diminish and/or end from nw to se
during the aftn thru Thu night.
With sfc high pres dominating northern Ontario on Fri and frontal
boundary/baroclinic zone shifted farther s and sw, expect a dry day.
Will need to watch development of pcpn into the northern plains
where strengthening southerly flow/isentropic ascent ahead of
western CONUS trof leads to an expanding pcpn area. Right entrance
upper divergence with a reoriented upper jet in a nw-se direction
across northern Ontario to New England could aid the expansion of
pcpn toward Upper MI late Fri or Fri night.
ECMWF has been most insistent on pcpn briefly streaking se into at
least western Upper MI Fri night into Sat underneath right entrance
of upper jet and within an eastward extension of isentropic ascent
from the northern Plains. GFS/CMC have been more varied on whether
or not the pcpn will reach the area, but since majority of GFS/CMC
ensembles support the streak of pcpn, fcst will reflect chc pops
spreading into the far w Fri night and expanding e into central
Upper MI Sat morning before pcpn area dissipates.
Fcst for Sun thru Tue is highly uncertain, much more than is
typically the case at this time range and no different from the last
few days. Over the last 4 days, medium range guidance has shown
considerable spread in what happens with the western CONUS trof and
how the flow evolves across southern Canada this weekend thru early
next week. The 00z GFS is back to showing a mid level low closing
off over the Upper Mississippi Valley/western Great Lakes early next
week, a solution that appeared once days ago though it got to that
solution in a different manner. At this point, consensus of recent
days guidance is for a shortwave which incorporates at least some of
the energy in the western CONUS trof to reach the area early next
week, but wouldn`t be surprised at all if something completely
different occurs. Maintaining some continuity with previous fcst,
will show chc pops spreading slowly e across the area Sun/Sun night,
lingering Mon then trending dry on Tue.
&&
.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 649 AM EDT WED SEP 21 2016
Although there wl be a good deal of mid clds at times and perhaps a
few -shra late this aftn, dry llvl air wl ensure VFR conditions
prevail at all 3 TAF sites into early evening. Thicker clds and more
numerous showers will arrive late this evening into overnight as
conditions lower to MVFR at IWD by late evening and at SAW after 06Z.
CMX may stay mostly dry through the period but they could also see
MVFR conditions develop late tonight with increasing low-level
moisture and developing upslope easterly flow. Look for IWD to lower
to IFR by around 06z. &&
.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 515 AM EDT WED SEP 21 2016
Developing ne flow over Lake Superior with sfc trough moving into
Upper Mi and sfc ridge over Ontario could support some higher wind
gusts to 25 knots over the wrn half of the lake this afternoon into
Thu and across the entire lake Thu night into Fri. As the Canadian
high builds more over the Upper Lakes winds will dip blo 20 kts
Friday night into Saturday night. Southerly winds will increase late
Sunday into Sunday night to 25 to 30 knots over mainly the north
central and eastern part of the lake as a low pressure trough
approaches from the west.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...Voss
LONG TERM...Rolfson
AVIATION...Voss
MARINE...Voss
Area Forecast Discussion
National Weather Service Omaha/Valley NE
616 AM CDT WED SEP 21 2016
.SHORT TERM...(today through Friday)
Issued at 330 AM CDT WED SEP 21 2016
Thunderstorm chances this afternoon through Thursday are the primary
forecast concerns this period. Warm temperatures to continue as well.
Upper flow pattern was beginning its change as strong westerlies
across the Northern Plains were progressing east as strong
low/trough dropped into the Pacific Northwest early Wednesday.
Southwest mid level flow will remain over the Central Plains through
tonight, then shortwave ridging will build into our region later
Thursday into Friday. Shortwave within southwest flow aloft is shown
currently by RAP analysis moving through eastern Colorado, heading
toward Nebraska and Iowa later today and tonight. Meanwhile quasi-
stationary surface front extended from northeast Colorado into
southeast South Dakota and western Wisconsin. This boundary will not
move a whole lot much of the day as upper flow parallels front,
waiting for surface low tied to upper shortwave to develop and move
from central Nebraska into northern Iowa this evening. Increased low
level convergence ahead of the low will help ignite storms this
afternoon, then southward drift of front will occur in its wake
helped along by convection.
Expect storms to take some time to get going later today as
inhibition is slowly eroded and where low level convergence is
maximized in northeast Nebraska and southeast South Dakota ahead of
surface low. Instability increases markedly from near 1500 j/kg of
MLCAPE in northeast Nebraska to closer to 2500 j/kg in northwest
Iowa as per GFS, so we may miss initial development northeast of our
area around 00Z. As the evening progresses, southward drift of
surface front behind low combined with increasing moisture transport
over that boundary as low level jet kicks up will bring our best
chance for convection. Appears the best conjunction of those
parameters will lie somewhere between Columbus and Norfolk,
northeast to between Wayne and Tekamah, and into Monona County Iowa.
Expect storms to fire somewhere in this zone by 03Z, then expand
east and west with time. Continued moisture feed into south and
southwest flank will lead to some propagation southward toward
Interstate 80 overnight, but storms south of the Interstate may be
hard to come by.
Certainly could see severe storms given degree of instability but
overall bulk shear is modest at best. Storms becoming more outflow
dominant and loaded with precipitation suggests damaging wind gusts
or microbursts are possible as well. Heavy rain is also likely given
high precipitable water values near 1.75 inches shown by GFS, and
potential for training storms.
Bulk of overnight activity will be pushing off to the east Thursday
morning. Overall mid level pattern of building shortwave ridge
across our area will support northward propagation of frontal
boundary, but will not clear our northern border until later
Thursday night. Thus redevelopment of convection appears likely
Thursday afternoon where models support 2000 j/kg of ML and SB CAPE
and Bulk Shear is near 30kt.
By Friday morning building heights and front lifting north should
leave most of eastern Nebraska and western Iowa under capping mid
level temperatures. Surface temperatures should reach the upper 80s
again most spots Friday afternoon. In fact much of eastern Nebraska
and western Iowa will average mid and upper 80s for highs each
afternoon today through Friday. While highs Tuesday reached the 90s
all areas, more cloud cover today will likely hold temps down a tad,
though areas along and south of Interstate 80 could top 90 again.
And Thursday afternoon northeast Nebraska will be north of
retreating front and may not reach 80 in some areas.
.LONG TERM...(Friday night through Tuesday)
Issued at 330 AM CDT WED SEP 21 2016
GFS and ECMWF are fairly consistent in showing upper low rotating
into the Northern Plains on Saturday with trough axis extending into
New Mexico. They are also fairly close in depicting plume of
tropical moisture streaming into our region Saturday then being
shoved east by Sunday evening. Those models then diverge quite a bit
beyond that, with GFS offering a deep closed cyclone over Wisconsin
solution by Tuesday, and ECMWF maintaining general trough over our
region. As far as sensible weather in concerned, we will be on the
cool side of the system with pockets of cold air aloft rotating
across the region. Some of these may spark some showers from time to
time, but the main weather story appears to be temperatures in the
60s or lower 70s for highs to start next week.
Leading up to that, we will see periods of showers and thunderstorms
Saturday into Sunday when moisture plume is on top of us. GFS again
is painting precipitable water values of 1.75-2.00 inches across our
area Saturday. Thus heavy rain remains a concern Saturday and
Saturday night before bulk of activity pushes off to the east.
&&
.AVIATION...(12Z TAFS for KOFK...KLNK and KOMA.)
Issued at 616 AM CDT WED SEP 21 2016
Mesoanalysis as of 11z showed a surface low over southwest
Nebraska with an associated stationary front stretching northeast
through far northeast Nebraska into northwest Iowa. Aloft,
considerable high cloudiness was present over the mid Missouri
Valley, downstream from a mid-level impulse moving through the
central Rockies. LLWS will likely persist at all three TAF sites
for the next couple of hours, prior to the cessation of the
nocturnal LLJ. Thereafter, deeper boundary-layer mixing will yield
gusty south winds which should subside by evening.
The above-mentioned mid-level impulse will combine with the
surface front to foster scattered thunderstorms this evening into
tonight. Considerable uncertainty still exists with respect to the
exact location of this convection. Therefore, only PROB30 groups
have been included at this juncture.
&&
.OAX Watches/Warnings/Advisories...
NE...None.
IA...None.
&&
$$
SHORT TERM...Dergan
LONG TERM...Dergan
AVIATION...Mead
Area Forecast Discussion
National Weather Service Pueblo CO
416 AM MDT WED SEP 21 2016
.SHORT TERM...(Today and tonight)
Issued at 343 AM MDT Wed Sep 21 2016
Currently...
Abundant moisture associated with remnants of TC Paine were moving
over the southwest CONUS. Several bands of showers were noted in the
radar mosaics (Note: KGJX is out for scheduled long term
maintenance upgrade). It was still quite mild at 4 am as temps were
still mostly around 70F across the plains with cooler temps over the
higher terrain. Some snow was likely falling well above treeline.
Today...
The combination with a tightening 500 mb gradient associated with a
major trough moving onshore from the Pacific and the remnant
moisture of TC Paine will allow for lots of mid and high level
clouds over the region today. On and off showers will occur over the
higher terrain with the southwest mountains being favored. Areas
from the La Garitas to the Salida region may also see an enhanced
area of showers as per latest HRRR guidance. Isolated showers and
storms will also occur over the plains...especially along a trough
axis which will extend from roughly Trinidad to Lamar. Some locally
heavy showers will be possible.
Another warm day will occur across the plains although temps should
be tempered a bit due to the cloudiness over the region. Breezy
southwest winds will occur at times over the plains. It will be
windy across the mountaintops today...especially this morning.
Tonight...
Somewhat drier air will move into the region and precip chances will
significantly decrease across most of the region as the evening
progresses. Breezy conditions will continue over the higher
elevations and over the plains mainly south of a line from Lamar to
Trinidad. Another mild night is likely across the plains due to the
breezy conditions and clouds...and lows will likely remain in the
50s to around 60.
.LONG TERM...(Thursday through Tuesday)
Issued at 343 AM MDT Wed Sep 21 2016
Models in good agreement through the extended period. Much cooler
temperatures are on the way after a few more warm days.
Thursday and Friday...a strong upper level low is forecast to
develop over the Great Basin, forcing high pressure to build
across the central plains. This will bring continued moist
southerly flow to southern Colorado. Expect to see showers and
thunderstorms develop over the mountains on Thursday afternoon,
and spread northeast across the Palmer Divide into northeast
Colorado Thursday evening. Gusty winds are also expected across
the plains on Thursday, however, humidity values are expected to
remain in excess of 15 percent, with near critical fire weather
conditions expected. Models are also developing scattered showers
and thunderstorms over the far eastern plains Thursday evening,
which will move east into Kansas overnight.
Severe weather and dangerous fire weather conditions are possible
on Friday. The upper low is forecast to shift east into Utah on
Friday with increasing southerly flow across Colorado. Models
develop a surface low over northern Colorado by Friday afternoon
with a dryline extending south across our plains. Decent moisture,
strong shear and modest instability should allow for thunderstorm
development Friday afternoon along the boundary. Strong to severe
storms are possible, with strong out flow winds in excess of 60
mph and 1 inch diameter hail being the main threats. Current model
projections have the greatest threat for severe weather east of a
Fowler to Trinidad line, but much will depend on how far east/west
the dryline sets up.
Strong southwesterly winds and drier air is expected west of the
dryline, generally in the lee of the eastern mountains into the
I-25 corridor. Humidity values look to fall right near 15 percent
Friday afternoon producing dangerous fire weather conditions. This
will need to be monitored closely.
Temperatures will remain warm Thursday and Friday with upper 80s
to mid 90s expected across the lower elevations.
Saturday into Sunday...the upper low is forecast to lift into the
northern plains over the weekend with energy splitting over the
desert southwest. Saturday looks to be generally dry across the
area as the upper system splits. Temperatures will be much cooler
with mostly 70s across the area. A strong cold front will drop
south Saturday night with a northerly wind shift by Sunday
morning. Models agree on the front, but not with precipitation
chances. The GFS is dry behind the front on Sunday. Meanwhile, the
ECMWF develops widespread showers across the area behind the
front due to better upslope flow and moisture. For now have low
pops for upslope favored areas of the plains. Reduced afternoon
highs on Sunday to the upper 60s to lower 70s, however, a few
solutions are indicating temperatures may not get out of the upper
50s. If precipitation does fall over the mountains this weekend, a
few inches of snow are possible above 10 kft.
Monday into Tuesday...the upper system will continue to lift into
the Great Lakes region while high pressure builds over the western
states into Colorado. This should bring drier conditions along
with a warming trend early next week. Any precipitation should
remain confined to the higher terrain and be diurnally driven.
Temperatures will rebound back into the 70s to lower 80s. Mozley
&&
.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 343 AM MDT Wed Sep 21 2016
VFR conditions are expected during the next 24h at all 3 taf
sites...kpux...kals and kcos. Breezy 20ft sfc winds will prevail
this afternoon. An isold shra.-tsra will be possible but any precip
will likely be brief. Lots of clouds will prevail but they will be
mid and upper lvl clouds.
&&
.PUB Watches/Warnings/Advisories...
NONE.
&&
$$
SHORT TERM...HODANISH
LONG TERM...MOZLEY
AVIATION...HODANISH
Area Forecast Discussion
National Weather Service Blacksburg VA
905 AM EDT Wed Sep 21 2016
.SYNOPSIS...
An upper low will meander about eastern North Carolina and South
Carolina through late week before finally shifting out into the
Atlantic ocean. High pressure will gradually build in from the
west during the latter half of the week. A backdoor cold front
drops south through the area later Saturday followed by cooler
high pressure Sunday into Monday.
&&
.NEAR TERM /THROUGH TONIGHT/...
As of 905 AM EDT Wednesday...
Made some minor adjustments in temperatures shaping towards
sfc obs and lamp guidance for this morning, then allowing for a
rise in the east this afternoon. (Clouds cover and scattered
showers will hold temperatures down this morning in Southside.)
Also, modified pops for this morning with latest WSR- 88d trends
and push isolated chances a little further west for this
afternoon. The Hiresw-arw-east, WRF-arw-rnk and HRRR support the
mention of isolated to scattered showers across the southeast
portions of forecast area. Expecting a nice day under sunshine in
the west and northwest portions of forecast area. More changes
later this morning.
As of 315 AM EDT Wednesday...
Looking at lingering low pressure from Julia combined with upper low
over Eastern NC to keep the eastern half of the forecast area in
clouds for most of the day today. Models in general agreement in
showing a sharp gradient to showers, mainly keeping them southeast
of a line from Farmville to Yadkinville. The 00z ECM is a little
more broad in coverage as far west as the Blue Ridge. The 00z NAM
actually seems to have a good handle of ongoing showers east of our
forecast area, but is showing some higher qpf later today across the
northwest piedmont of NC east of Reidsville into Halifax county
Virginia. For the forecast today, am leaning toward a drier scenario
from the foothills west into the mountains with high chance pops in
the extreme southeast cwa to slight chance/20 pops toward
Lynchburg/Martinsville and Yadkinville. High level clouds will
obscure the sunshine at times as far west as the I-81 corridor with
more sunshine in Southeast WV and generally cloudy in the east.
Highs will still be warm with mid 70s to around 80 expected, but
possibly warmer toward Abingdon and Richlands in the lower 80s.
The gradient today will also tighten to allow a breeze of 10 mph
with gusts to 20 mph especially along and east of the Blue Ridge.
Tonight, the upper low remains fixed across the coastal Carolinas.
At the surface the low jogs somewhat southwest. Orientation for best
shower coverage will wrap tighter toward the coast, so will dry
things out overnight with lingering low chance pops in the evening
in the far southeast from South Boston VA to Reidsville, NC.
Otherwise will be clearing in west but remains mostly cloudy in the
piedmont south of Lynchburg, as well as across the NC mountains and
foothills. Lows should stay mild in the east with mid 60s, with
upper 50s to lower 60s west, which is still about 5 to 10 degrees
above normal.
&&
.SHORT TERM /THURSDAY THROUGH SATURDAY NIGHT/...
As of 230 AM EDT Wednesday...
During this portion of the forecast, a upper low over South Carolina
will make slow progress to the southeast, all while an upper ridge
builds over the Ohio and Mississippi Valleys. Concurrently, a broad
upper trough will reside over southeast Canada, and southerly flow
on its west side will propel a backdoor cold front into our region
Saturday into Saturday night.
The result of this transition will be even less coverage of isolated
showers across the south and southeastern portion of the region.
Only the Canadian solution at this point has more of a glancing blow
of precipitation for this portion of the forecast area. The forecast
will reflect the last isolated showers departing the far
southeastern sections Thursday evening.
High pressure will provide for limited cloud cover on Friday into
Friday night with no precipitation forecast. The backdoor cold front
at this point is progged to have little if any precipitation
associated with in Saturday into Saturday night, but an increase in
cloud cover is anticipated. Lower dew point air will start moving
into northern sections of the area by late Saturday night.
Temperatures will continue to average about ten degrees above normal
through Saturday night.
&&
.LONG TERM /SUNDAY THROUGH TUESDAY/...
As of 130 PM EDT TUESDAY...
Strong upper ridging centered along the Mississippi River to start the
weekend will gradually get pinched back to the southwest as a rather
high amplitude troughing regime develops over the northeast U.S. by
early next week. This will allow increasing northwest flow aloft to
take shape across the region between the departing 500 mb ridging and
eventual upper level low pressure over New England. Cooler high
pressure expected Sunday into Monday. This before yet another
cold front arrives from the northwest on Tuesday with the next
stronger mid level shortwave. However deeper moisture looks quite
limited with both frontal passages given a dry west/northwest flow
aloft so only including slight shower pops later Saturday west and
again Tuesday. Low level flow turning more east/northeast behind
the initial boundary, per the developing wedge could allow for a
slight uptick in shower coverage southern sections Saturday night,
although iffy for much more than clouds/sprinkles at this point
per lower amplitude/drier ensembles.
Subsequent rounds of decent cool advection look to arrive with
each frontal passage into late Tuesday with potential for Sunday
into Monday to remain quite cool if clouds are more widespread.
This timing continues to vary between solutions as each may be too
strong, although thinking highs mostly 70s Sunday-Tuesday, with
50s for lows and possible 40s valleys Monday morning with high
pressure overhead.
&&
.AVIATION /13Z WEDNESDAY THROUGH SUNDAY/...
As of 735 AM EDT Wednesday...
MVFR ceilings to affect DAN and at times LYH early then become
VFR. A few showers are possible near DAN but coverage is such that
it was not considered to be mentioned in the tafs. The fog never
developed at LWB, and we should be seeing VFR for most of the taf
period. Winds will be breezy along and east of the Blue Ridge with
the gusts reaching 20kts at times between 16-22z.
Tonight the skies will clear from northwest to southeast to a
point, but remain broken at the high cloud level overnight in the
DAN area. Model forecast soundings with easterly flow suggest
potential for low cloud development or advecting in from the east
along with patchy fog. Will keep it optimistic and go no lower
than MVFR at LYH/DAN/BLF/BCB on vsbys with IFR at LWB late
tonight.
Extended aviation discussion...
Thursday and Friday, outside of late night/early morning fog/low
clouds, expect mainly VFR conditions. The slight chance of showers
will remain just east of KLYH and KDAN through Thursday night.
GFS/ECMWF have been consistent in filling and lifting out the low
to the northeast on Friday.
A back-door cold front will come through the Mid-Atlantic region
on Saturday. High pressure will build in for Sunday. The chance of
precipitation or any sub VFR conditions will increase through the
day Sunday and into Sunday night.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...RAB/WP
NEAR TERM...KK/WP
SHORT TERM...DS
LONG TERM...JH
AVIATION...AMS/RCS/WP
Area Forecast Discussion
National Weather Service Las Vegas NV
845 AM PDT WED SEP 21 2016
.SYNOPSIS...Weather will remain cool and unsettled through the end
of the week as remnant tropical moisture interacts with a trough
pushing in from the west. The trough will bring increasing winds and
and drier air which will aid in dangerous fire conditions for some
areas along with the possibility of strong thunderstorms in northwest
Arizona and eastern Nevada. Temperatures will remain cool through
the weekend before inching back to near normal early next week.
&&
.UPDATE...Made some adjustments to the grids this morning to
increase the PoPs across northern Mohave county where persistent
rain continues this morning. Best chances for showers will again be
across areas south of I-15 today though chances will increase across
our Northwestern zones this afternoon as a trough begins to approach
the region.
-Outler-
&&
SHORT TERM...Through Friday night.
At 4 am, showers continue to stream up from the south moving across
western San Bernardino, far southern Clark and central and northern
Mohave counties. Radar return intensity and rain gauges suggest
mainly light and occasional brief moderate rain.
The latest HRRR forecasts spotty shower activity today tied
primarily to the mountains. The NAM and GFS forecast better coverage
with the best chances in Mohave County. Abundant moisture remains in
place through the day and models forecast weak instability for a
better shot at embedded thunderstorms this afternoon. The trough
advances into central California and western Nevada tonight with a
cold front pushing into the northwestern regions of the CWA. A
period of stronger winds are forecast across the Sierra with some
potential for winds to reach the lower western slopes of the Owens
Valley. Issued a Wind Advisory for these areas beginning late this
afternoon and continuing through noon Thursday. The front continues
to move south through the area on Thursday creating strong southwest
to west winds ahead of it and gusty north winds behind it. Wind
Advisories were also issued for portions of southeast California,
southern Nevada and northwest Arizona beginning at noon Thursday.
The cold front will push moisture to the east as it advances through
the area Thursday with showers and storms limited to mainly the
eastern portions of the forecast area. There is some concern for
training storms and the potential for flash flooding in Mohave
County Thursday prior to the decrease in moisture. Model forecasted
instability is not overly impressive so will let the day crew take a
look at it. The trough moves agonizingly slow and it not forecast
to be east of the area until late Friday. However, dry air is
solidly in place and no precipitation is expected on Friday. Breezy
north to northeast winds and cooler temperatures are expected. High
temperatures Friday will be 10-15 degrees below normal with a chilly
morning low Friday around 10 degrees below normal.
.LONG TERM...Saturday through Tuesday. Forecast confidence is above
average for Saturday and Sunday as what little spread the models
show would be of little impact on our sensible weather, then
confidence quickly deteriorates Monday and Tuesday as spread
increases and also begins to focus in and around our area. For
Saturday and Sunday, the low pressure system which affected the area
in the short term will have moved away to the east, with Pacific
high pressure nearing the coast. This puts our area in northerly
flow aloft with very dry air in place. The main foci for this period
will be gusty northerly winds down the Colorado River Valley and a
substantial warming trend area wide. For Monday and Tuesday, as the
low and its associated trough roll east across the Plains, a
significant number of model perturbations break a piece of energy
out of the base of the trough over Texas, and then retrograde it
west as a closed low around the southern periphery of the Pacific
high. A smaller number of these perturbations /including the
operational GFS20/ ingest tropical moisture into this closed low and
pull it into our area late in the week. This is a long way off, and
would be an unusual pattern evolution to say the least. Will keep an
eye on Thursday and Friday as they move into the seven-day forecast
period.
&&
.FIRE WEATHER...Strong winds and low humidity will combine forces
to create a period of critical fire weather conditions Thursday
afternoon. Fuels remain very dry especially north of I-40 which will
see little benefit from the remnant moisture of tropical depression
Paine. Red Flag Warnings are in effect for the San Bernardino County
deserts, much of the lower elevations of Clark County, the lower
Colorado River valley and Lake Mead NRA. Improving conditions are
expected friday as the winds relax.
&&
.AVIATION...For McCarran...Winds will be light and diurnally driven
this morning then stronger SW winds kick in by late this afternoon.
A slight chance of storms tomorrow afternoon/evening.
For the rest of southern Nevada...northwest Arizona...and southeast
California...Primarily S/SE winds this morning increasing in the
afternoon. An increasing chance of storms by this afternoon. Strong
winds will develop over the Sierra tonight and possibly into the
lower western slopes of the Owens Valley. Westerly winds could reach
as far as KBIH with gusts up to 20 kts possible tonight.
&&
.SPOTTER INFORMATION STATEMENT...Shower and thunderstorm chances
continue through Thursday. Strong winds are also expected in much of
the area Thursday afternoon and evening. Spotter activation may be
required Wednesday afternoon through Thursday. &&
$$
Short Term/Aviation/Fire Weather...Salmen
Long Term...Morgan
For more forecast information...see us on our webpage:
http://weather.gov/lasvegas or follow us on Facebook and Twitter
Area Forecast Discussion
National Weather Service Albuquerque NM
319 PM MDT WED SEP 21 2016
.SYNOPSIS...
Scattered showers and thunderstorms will move northeast across New
Mexico through Friday. Some of the stronger storms may produce brief
strong wind gusts and perhaps some small hail. Temperatures will be
above normal in many areas through Friday before a strong cold front
surges through the state by late in the day. Low temperatures will
be the coldest since last spring for much of the state. Lows will
range from the 20s and 30s across the northern and western high
terrain to the 40s and 50s across the eastern plains. Temperatures
will likely stay cooler through early next week with a chance for
some showers across the eastern half of the state.
&&
.DISCUSSION...
The remnant upper level wave from what was formerly Hurricane Paine
is shifting quickly northeast across NM this afternoon. It`s low
level center dissipated off the northern Baja and any moisture that
was associated with it has been washed out across a vast area of the
southwest CONUS. Enough forcing is present aloft to combine with
afternoon heating for a decent crop of storms around the central and
western high terrain. Activity is cruising along and has potential
to tap stronger winds aloft. Strong outflow winds and perhaps some
small hail are possible with any of the stronger storms. The latest
HRRR and SPC SSEO merges convection into an area over the San Juan
Mts and the RGV this evening. Thursday is expected to be a repeat of
today with perhaps a better focus along and west of the Cont Dvd.
Friday will be a dynamic day across NM as a potent Pacific cold
front surges southeast through the area. High temperatures will
still be quite warm ahead of the front. Veering wind profiles and
abundant moisture still in place over the region should allow for
at least a thin line of storms along the main frontal forcing. 12Z
guidance is still paltry with precip development and has actually
trended drier than previous runs. Will maintain chance POPs for now.
700mb temps fall from near +14C to around +4C behind the front.
This strong cold advection along with impressive dry air advection
will lead into the coldest night since last spring for much of the
state. Folks around Farmington will want to keep a close eye on the
min temp forecast as we are currently advertising 35F. Sheltered
areas that are typically colder may see their first freeze.
Overall Saturday appears to be a tranquil day with cool northwest
flow over the state. Max temps will be 10 to 20F colder than Friday.
The upper level trough is now shown by most of the 12Z guidance to
push slowly east away from the area while developing into a large
scale upper low over the Great Plains. This is yet another change in
the outlook so confidence remains low. Nonetheless, temps will stay
cooler through early next week with the greatest potential for any
precip over the east.
Guyer
&&
.FIRE WEATHER...
Moisture levels surface and aloft considerably higher today than
on Tue thanks in large part to moisture shunted northeast from
the remnants of once Hurricane Paine. Enough sunshine has
materialized to generate some spotty showers and thunderstorms
across roughly the nw half of the fcst area. More isolated
activity struggling to keep going just east and ne of the
Sacramento mtns. Majority of the storms should be able to manage
wetting rainfall.
On Thu this moisture will begin to yield a bit to a drier sw flow
out ahead of a deepening trough aloft moving into the Great Basin.
Winds through a deep atmospheric layer over NM will be picking up
as the upper trough and associated Pacific cold front approach.
Lee side surface troughing across the east Thu will encourage
development of breezy to locally windy conditions most areas by
aftn. Despite some modest drying in the atmosphere Thu there will
still be a decent chance of a few showers and storms mainly to the
west of the eastern plains thanks to the dynamic forcing of the
approaching trough. The main Pacific front should push into and
through NM between late Thu night and Fri but moisture will be
less Fri than Thu so fewer wetting showers and storms are
expected, especially east of the Continental Divide. High temps
behind the front across nw and west central NM will be a few to
around 10 degrees below seasonal normals.
With passage of a pretty healthy back door front Sat night and Sun
daytime temps will be below normal pretty much all across the area.
Chances for wetting rain later in the weekend and early next week
still look to be less than what appeared would be the case a day or
two ago, though eastern areas still have a pretty good chance. a
developing closed low over to just west of the state looks a little
less likely now than was the case over 24 hours ago. In fact by mid
to late week next week daytime temps may head back well above
normal. The Canadian fcst model though is still holding to a
somewhat weaker upper low or deep trough hanging out over the state
so dry and warmer for this time period not certain yet by any means.
43
&&
.AVIATION...
18Z TAF CYCLE
VFR conditions will remain the rule across most of the fcst area,
however the nw third of the area may still see a few instances of
relatively brief MVFR cigs in stronger TSRA that develop this aftn
into this eve. KGUP and KFMN still have a small risk of this
occurring into this eve, but generally kept their fcst above the
MVFR category. Elsewhere there will also be isold to occasionally
sct SHRA/TSRA coverage mostly from the AZ line east to the
highlands immediately to the east of the central mt chain. Some
mt obscurations likely as well, especially over the north. The
activity will diminish to far fewer in number between 03Z and 07Z,
but a few patches of MVFR conditions could redevelop late tonight
across roughly the nw third of the fcst area along with a few
instances of mt obscurations redeveloping late also.
43
&&
.PRELIMINARY POINT TEMPS/POPS...
Farmington...................... 57 82 52 68 / 20 20 40 30
Dulce........................... 49 78 47 65 / 50 60 60 60
Cuba............................ 51 76 48 65 / 40 40 30 50
Gallup.......................... 50 80 49 66 / 20 20 30 30
El Morro........................ 49 78 46 63 / 30 20 30 40
Grants.......................... 52 82 48 70 / 30 30 30 30
Quemado......................... 52 80 50 72 / 20 20 20 30
Glenwood........................ 59 84 56 75 / 20 20 10 30
Chama........................... 47 71 45 59 / 60 60 60 60
Los Alamos...................... 55 78 53 69 / 40 40 30 40
Pecos........................... 53 78 52 72 / 60 40 40 30
Cerro/Questa.................... 49 76 50 68 / 30 30 30 40
Red River....................... 45 70 43 66 / 30 30 30 40
Angel Fire...................... 41 72 42 68 / 40 50 30 40
Taos............................ 50 79 50 71 / 30 30 30 30
Mora............................ 52 76 52 70 / 40 50 30 30
Espanola........................ 58 83 57 77 / 30 20 30 30
Santa Fe........................ 57 77 54 72 / 50 30 40 30
Santa Fe Airport................ 56 82 54 77 / 40 20 30 30
Albuquerque Foothills........... 61 83 59 77 / 40 30 30 20
Albuquerque Heights............. 62 86 59 80 / 40 20 20 20
Albuquerque Valley.............. 60 87 59 82 / 40 20 20 20
Albuquerque West Mesa........... 61 87 58 81 / 40 20 20 30
Los Lunas....................... 59 88 56 83 / 40 20 20 20
Rio Rancho...................... 61 87 58 81 / 40 20 20 30
Socorro......................... 62 89 59 85 / 30 30 20 20
Sandia Park/Cedar Crest......... 57 79 54 73 / 50 30 40 30
Tijeras......................... 58 83 55 77 / 40 30 30 30
Moriarty/Estancia............... 54 80 53 79 / 50 30 30 20
Clines Corners.................. 54 80 52 76 / 40 30 20 20
Gran Quivira.................... 57 80 56 76 / 30 30 20 20
Carrizozo....................... 61 86 60 82 / 20 20 20 20
Ruidoso......................... 54 78 54 74 / 30 30 20 30
Capulin......................... 56 81 56 77 / 20 30 10 20
Raton........................... 54 83 54 78 / 20 30 10 20
Springer........................ 56 84 55 80 / 20 30 10 10
Las Vegas....................... 53 81 54 76 / 30 30 20 20
Clayton......................... 61 87 60 83 / 20 20 10 20
Roy............................. 59 83 58 79 / 20 20 10 20
Conchas......................... 66 90 64 86 / 20 20 10 20
Santa Rosa...................... 62 90 61 85 / 20 20 10 20
Tucumcari....................... 65 93 63 90 / 10 10 5 20
Clovis.......................... 61 88 60 87 / 10 5 5 10
Portales........................ 62 88 62 87 / 10 5 5 10
Fort Sumner..................... 63 88 61 87 / 10 10 5 20
Roswell......................... 62 90 62 90 / 10 10 5 10
Picacho......................... 59 84 59 83 / 10 20 10 20
Elk............................. 57 80 57 78 / 10 20 20 20
&&
.ABQ WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Area Forecast Discussion
National Weather Service Denver/Boulder CO
322 PM MDT Wed Sep 21 2016
.SHORT TERM...(This evening through Thursday)
Issued at 322 PM MDT Wed Sep 21 2016
The strong mid and upper level trough we have been watching for
the past several days is currently located across the Pacific
Northwest. It will dig south and west over the next 36 hours and
by Thursday evening it will be located over the northern half of
Nevada. The trough continues to advect mid level moisture into
Colorado while the low levels remain dry until overnight tonight.
The moist southwest flow will provide a slight chance of
thunderstorms in the mountains and across parts of the Plains the
remainder of the day. Early this evening the HRRR and NAM generate
showers over the mountains and and the HRRR has been consistent in
sustaining the showers across the urban corridor and then further
east across Morgan, Lincoln, and Elbert Counties. Both models did
the same thing yesterday under similar atmospheric conditions yet
nothing materialized. Will introduce 10-20 percent PoPs in those
areas but not expecting much if anything to reach the ground.
Tonight a cool front brings mid 50s dewpoint air in through the
backdoor across northeast Colorado after 3 AM. Stratus is possible
if not likely across northeast Colorado. Less confidence in the
stratus making it to metro Denver but it could come close to
Denver International Airport.
On Thursday strong southwest flow aloft continues and the
atmopshere is fairly moist with PWATs east of the Rockies in the
0.75-1.00 inch range. The good news is that surface dewpoints east
of the Rockies will be the highest they have been in many days.
The bad news is that the moisture is shallow, short lived, and
there is too little instability available to generate convection
of any significance. As the trough approaches Colorado the low to
mid level flow turns more south-southwest and will act to dry out
the lower levels from west to east starting Thursday evening. Best
chances for afternoon thunderstorms will be across the mountains.
Temperatures should be in the mid 80s most areas though if stratus
hangs on as long as expected, the north and northeast corner of
Colorado may stay in the 70s.
.LONG TERM...(Thursday night through Wednesday)
Issued at 322 PM MDT Wed Sep 21 2016
For Thursday night, we could see a couple high based showers/
storms drift northeast out of the mountains onto portions of the
adjacent plains, but overall airmass on the plains is still rather
dry and stable so only low PoPs warranted if at all.
By Friday, the unseasonably deep upper level low in the Great
Basin is expected to lift northeast across Utah. Upper level
support will increase but latest runs indicate some splitting of
this energy, and a couple models including the GFS are very
aggressive with the dry slot moving across the plains. At this
time it`s looking like the drier airmass should prevail as a very
strong and deep southerly flow develops across much of the
forecast area. Winds will increase with lowering humidities
increasing fire danger...see Fire Weather discussion below. There
is still enough lift for a few high based afternoon showers and
thunderstorms. Again, the best chance would be over the mountains
and far northern sections of the forecast area where a little more
moisture should hold in place.
Friday night, the upper level trough or at least a piece of it and
the cold front will move across the state. This will usher in
cooler temperatures and also bring some snow to the mountains. At
this time, looks like mainly light snow but some accumulation
would be possible mainly over the far northern mountains from
Rabbit Ears to Rocky Mountain National Park where deeper moisture
and stronger orographics exist. That same general weather pattern
will remain in place through Saturday with highs mainly in the 60s
on the plains and 40s/lower 50s in the mountains.
By Sunday, a few of the models are now indicating a second wave of
energy now dropping across the area in Northwest flow aloft. That
is in contrast to the shearing trough noted in yesterday`s model
suite. In any case, will maintain the low PoPs but trend temps a
bit cooler. If ECMWF verifies then we could see snow down through
most of the foothills.
For Monday and Tuesday, again in contrast to yestereday`s runs,
models now show the deeper upper level low developing into the
Midwest. Not sure exactly how this will eventually play out but
will keep temperatures cooler than normal with only a slight
chance of showers returning by Tuesday only if another wave drops
into the area on northwest flow. Wednesday should see a return to
near normal temperatures as long as upper trough moves to the
east.
&&
.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 322 PM MDT Wed Sep 21 2016
|There is a slight chance of showers across the terminals this
evening that would temporarily cause shifting and gusty winds.
Around 12Z a backdoor front approaches KDEN. Winds behind the
front will be light but with high low-level moisture in place,
stratus is a concern. Not confident the stratus will make it to
KDEN but put in a TEMPO group to provide a heads up for the
potential. Aside from the low but nonzero chance of IFR ceilings
between 12 and 15Z, VFR conditions should prevail with diurnal
winds under 10 kts until late Friday afternoon when winds will
pick up from the south.
&&
.FIRE WEATHER...
Issued at 322 PM MDT Wed Sep 21 2016
Fire danger will increase in all areas Friday as strong southerly
flow results in gusty winds. Anywhere from the Mountains east
across the Denver/Palmer Divide area onto the plains could see
gusts around 40 mph due to the strength of low level flow and
pressure gradient. Humidity is still marginal but if latest GFS
trends continue we`ll have to upgrade to a Fire Weather Watch.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...Schlatter
LONG TERM...Barjenbruch
AVIATION...Schlatter
FIRE WEATHER...Barjenbruch
Area Forecast Discussion
National Weather Service Cleveland OH
658 PM EDT WED SEP 21 2016
.SYNOPSIS...
High pressure will remain in control of the weather across the
region into Thursday. A cold front will move into the Great Lakes
on Friday then sag south of the area by Friday night. A cooler
Canadian high pressure will arrive Saturday into Sunday.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Only minor changes to cloud cover and hourly temperatures were
made to reflect current trends.
Previous Discussion...
A few clouds around this evening...primarily across northern OH
and nw PA. Some of this is afternoon cumulus which will fade
quickly late this afternoon. The mid/high clouds emanated from a
decaying MCS across MI this morning. They should drift across the
lake this evening. Although it cannot be ruled out
entirely...current satellite trends do not look favorable for
shower/ts development across southeast MI...so Toledo and across
the lake should stay dry. HRRR only guidance showing development
early this evening. Otherwise another quiet night with high
pressure overhead. Temperatures will be running above normal
tonight...but still a number of inland locations will get into the
50s.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY NIGHT/...
Pattern begins to amplify for the remainder of the week. While an
upper low takes up the Rockies/West Coast and ridge will build
across the Mississippi Valley. Precipitation Thursday will remain
north of the area along stalled frontal boundary across the Great
Lakes. This will provide yet another day with temperatures well
above normal. For reference...normals have now dropped into the
lower 70s.
A shortwave across central Canada will carve a trough across New
England and bring the Great Lakes front southward. This front has
the cooler weather bottled up to its north...so with its passage
Friday temperatures will be brought back closer to normal going
into the weekend. We will still likely reach and top 80 degrees
Friday. Saturday all will be in the 70s with some upper 60s likely
for highs across nw PA and a north-northeast flow. Little has
changed with the outlook for precipitation with this front.
Moisture and lift limited. Will continue with silent 20 percent
chances Friday into Saturday.
&&
.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
A rather substantial shift in the long range models is noted over
the last 24 hours with a trend towards an upper level low closing
off over the plains states. This blocking pattern would support a
high amplitude ridge building back into the Great Lakes Region with
temperatures trending warmer through the extended. Models had shown
this blocking pattern last weekend and feel the shift back to it is
supported by the strong upper jet over the North Pacific. With that
said, started trending the forecast drier and warmer during the
early part of next week. This pattern shift will need to continue to
be monitored on later model cycles.
&&
.AVIATION /18Z Wednesday THROUGH Monday/...
VFR conditions with only cirrus will continue through the
overnight. expect patchy mvfr br toward daybreak.
OUTLOOK...Some MVFR possible Saturday night in scattered shra/tsra.
&&
.MARINE...
A ridge over the eastern Great Lakes will shift south and weaken
through the end of the week. A weak area of low pressure will pass
north of Lake Erie on Thursday with a weak cold front settling south
across the lake on Friday. Northeast winds of 10-20 knots will
develop behind the front Friday afternoon and night causing waves to
build to 2 to 4 feet into Saturday morning. High pressure will
strengthen over the eastern Great Lakes over the weekend maintaining
easterly winds on the lake.
&&
.CLE WATCHES/WARNINGS/ADVISORIES...
OH...None.
PA...None.
MARINE...None.
&&
$$
SYNOPSIS...Oudeman
NEAR TERM...Mullen/Oudeman
SHORT TERM...Oudeman
LONG TERM...KEC
AVIATION...DJB
MARINE...KEC
AREA FORECAST DISCUSSION
National Weather Service Des Moines IA
344 PM CDT Wed Sep 21 2016
.SHORT TERM.../This evening through Thursday/
Issued at 344 PM CDT Wed Sep 21 2016
The primary concern into tonight is obviously convective trends
include heavy rain and severe potential. The current Grinnell-Forest
City outflow boundary from morning convection continues to try and
initiate new convection but is having little luck sustaining
anything or anchoring to it. A detailed look at the cells and radar
fineline notes development on either side of the boundary suggesting
this is mainly elevated. Thus even though uncapped 3000 j/kg MLCapes
are in place just west of the feature there seems to be lRegarding rainfall potential, precipitable water and warm cloud
depth values are not extreme, but seasonally high vs climatology
promoting efficient rainfall rates. The outflow boundary has reduced
confidence in high resolution solutions, but the HRRR, RAP and
HopWRF had the best handling on earlier Upper MS Valley convection
and suggest the northern few tiers of IA, eastward to the MS river
could get hit with heavy rains overnight with 15z ESRL HRRR amounts
up to an alarming 5-10 inches and the 15z HopWRF showing high
neighborhood probabilities of at least 5 inches over NE IA out of
our forecast area. Other models only show a few inches however,
which is possible if the stronger Corfidi vector movement makes the
convection too progressive north to south. So again it needs to be
emphasized that a very high impact event is certainly possible but
with somewhat diminished confidence due to model spread and
uncertainties.
Remember that this uncertainty is also carried over into the current
river forecasts which include 48 hours worth of QPF rather than the
typical warm season 24 hours. Current QPF depicts a widespread but
middle of the road 2-3 inches of rainfall affecting the Winnebago
and Cedar basins which results in moderate flooding in several
locations. Changes in location or rainfall amounts on either side of
that spread could result in lower or higher forecast stages. This is
why Hydrological Outlooks rather than warnings have been issued
until confidence in locations and magnitude increases.ow chances
of anything getting rooted surface based at the moment.
Convergence is shallow per the lack of 0-2km moisture convergence
and surface winds east of the boundary are veering suggesting a
downward trend in overall convergence. Some strong to severe
elevated storms are still possible however with higher effective
shear and ESRH still in place north and east of the boundary.
The question into tonight then turns to where new MCS development
will occur and its movement. Confidence is not the highest however
as none of the models are handling the strength of the outflow
boundary well. Examination of 305K isent surfaces show the NAM and
GFS focusing 30-40kts of flow and convergence from the Mason City
area into southern MN while the latest Rap washes this out more and
highlights MN. The latest objective analysis shows the 925/850mb
fronts and associated frontogenesis into MN so this would appear to
be the favored MCS genesis region. It does not mean IA will be
spared however. The strength of the inflow results in Corfidi
vectors with a pronounced southern motion suggesting the MCS will
eventually be drawn into IA. MUCapes of a few thousand should
persist into the night with around 30kts of effective shear
suggesting severe storms would remain possible with favorable shear
orientation north to south into IA.
.LONG TERM.../Thursday night through Wednesday/
Issued at 344 PM CDT Wed Sep 21 2016
Little change in going forecast for the next few days. Confidence in
overall trends for heavy rainfall potential remains high...but
details still debatable due to daily mesoscale interactions.
By early Thursday morning still expecting ongoing convection
across the north with old outflow boundary still the focus for
some thunderstorm activity over the north half of the forecast
area. Though the better forcing will be in the overnight period
tonight...there will still be enough instability during the
morning and afternoon hours to promote thunderstorms with locally
heavy rainfall potential over the north half of the forecast area.
Will maintain FFA across the area through tomorrow afternoon.
Through the night another strong push of thetae advection will
precede the next upstream wave propagating northeast by 12z
Friday. Most of any convection should be confined to the north
third Thursday night and north into Minnesota. With the boundary
holding on there will still be the potential for additional
locally heavy rainfall across the north. If trends continue...
there may be a need for an extension of headlines there. By 12z
Friday models push the warm front well into southern Minnesota.
This will temporarily limit convection over our area as all of the
forcing will be moving north. With the warm sector fully realized
once again Friday...highs will move back into the upper 80s to
lower 90s during the afternoon hours. Surface dew points will
again remain rather uncomfortable in the mid to upper 60s...with
heat indices well into the 90s by late afternoon. With the approach
of an upper level trough over the northern Plains Saturday a cool
front will move into the area by 12-18z. Models have advanced the
front a bit faster...though the boundary begins to slow as it
crosses the region from Sunday through Monday morning. Unfortunately...
the tropical moisture feed will remain intact just along and east
of this boundary. There is some uncertainty but if the boundary is
hung up long enough additional moderate to locally heavy rainfall
amounts of 1 to 2 inches may occur over the region between Saturday
evening and Monday morning...especially east of I35. The GFS and
Euro diverge thereafter...with the GFS focusing the boundary southeast
of the region from Monday through Wednesday. The Euro holds the boundary
over eastern Iowa and with a more northerly track of the northern
Plains system into midweek next week as well as a rather strong southern
stream H500 system developing by 12z Monday. The GFS has the northern
system looping back southeast by 00z into the Central Plains with
virtually no southern stream component at H500 at that time. The
result here is that the surface boundary and rain is pushed out of
the region by the GFS. For comparison...the GEM is even slower and
farther west than the Euro. At this time...will have to weight the
Euro/GEM solutions a bit higher and will need to closely monitor
trends through the weekend. If the latter proves a better solution...the
resultant rainfall over the region could additionally add several
more inches of precipitation on top of what is projected through
Monday. The reason...both the direct fetch from the Gulf and potential
for another old tropical system being injected into the area from
the southern Plains. Highs next week should be cooler with extensive
cloud cover and chances for rainfall.
&&
.AVIATION.../For the 18Z TAFS through 18Z Thursday afternoon/
Issued at 1259 PM CDT Wed Sep 21 2016
VFR conditions are in place area wide with main feature an outflow
boundary along KMPZ-KFXY line at 17z with a sharp discontinuity
from SW to SE wind. Convection is expected to develop near this
feature into the evening and also along a NE/SD warm front. Thus
expect periods of convection to affect KFOD/KMCW/KALO into the
night. Timing, location and duration of MVFR or less conditions
and thunder is still in question however so have nothing more than
vicinity wording and VFR for now.
&&
.HYDROLOGY...
Issued at 344 PM CDT Wed Sep 21 2016
Regarding rainfall potential, precipitable water and warm cloud
depth values are not extreme, but seasonally high vs climatology
promoting efficient rainfall rates. The outflow boundary has reduced
confidence in high resolution solutions, but the HRRR, RAP and
HopWRF had the best handling on earlier Upper MS Valley convection
and suggest the northern few tiers of IA, eastward to the MS river
could get hit with heavy rains overnight with 15z ESRL HRRR amounts
up to an alarming 5-10 inches and the 15z HopWRF showing high
neighborhood probabilities of at least 5 inches over NE IA out of
our forecast area. Other models only show a few inches however,
which is possible if the stronger Corfidi vector movement makes the
convection too progressive north to south. So again it needs to be
emphasized that a very high impact event is certainly possible but
with somewhat diminished confidence due to model spread and
uncertainties.
Remember that this uncertainty is also carried over into the current
river forecasts which include 48 hours worth of QPF rather than the
typical warm season 24 hours. Current QPF depicts a widespread but
middle of the road 2-3 inches of rainfall affecting the Winnebago
and Cedar basins which results in moderate flooding in several
locations. Changes in location or rainfall amounts on either side of
that spread could result in lower or higher forecast stages. This is
why Hydrological Outlooks rather than warnings have been issued
until confidence in locations and magnitude increases.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through Thursday evening for IAZ004>007-
015>017.
Flash Flood Watch from 7 PM CDT this evening through Thursday
evening for IAZ023>028-033>039-044>048.
&&
$$
SHORT TERM...Small
LONG TERM...REV
AVIATION...Small
HYDROLOGY...Small
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
657 PM EDT WED SEP 21 2016
.AVIATION...
Recent satellite data indicates localized subsidence across Lower
Mi, which is currently causing the convection across Wisconsin to
diminish as it moves east. Overnight, showers and thunderstorms are
expected to eventually expand east into the northern Great Lakes
along a frontal boundary, while some degree of subsidence holds
across Se Mi. The subsidence is expected to keep convection north of
the terminals through the night and well into Thursday. While MBS
will be closer to the better feed of moisture/instability along the
frontal boundary draped across the nrn Great Lakes, the
probabilities of TSRA at MBS are still rather low, too low to
include in the terminals attm. Satellite trends have shown enough
thinning/decrease in high clouds working into Se Mi to suggest some
periods of decent radiational cooling overnight. Given that sfc
dewpoints are well in the 60s, a chance of some MVFR type
visibilities in fog toward daybreak will be added to the TAFs.
For DTW...Metro Detroit will remain far enough removed from the
region of moisture and instability to the north and west to provide
little to no chance for TSRA through the TAF period. The thicker
cirrus will likely remain north of metro, so radiational cooling
potential may support a brief period of light fog early Thurs
morning.
//DTW Threshold Probabilities...
* None
&&
.PREV DISCUSSION...
Issued at 344 PM EDT Wed SEP 21 2016
DISCUSSION...
Energetic upper levels continue through mid week as a nearly zonal
140+ knot jet streaks across the US/Canada border. Weak southern
stream jet lifting northeast out of the developing west coast upper
level trough, will send a series of shortwaves through the plains
and into northern MI. The pattern has also resulted in a broad
surface developing over the central plains with a warm front taking
shape across the Central Great Lakes. This pattern will deviate very
little now through the end of the week as the strong Hudson Bay low
remains in place.
Area should remain dry through the rest of the evening and into the
overnight hours as subsidence in the wake of the early afternoon MCS
settles over southern MI. Hires HRRR and RAP advertise some
redevelopment this evening along I94 on the sinking outflow boundary
but confidence is low in the occuring. The current cap will make it
hard for anything to develop, even with a bit of late afternoon
heating. Radar trends through the day have shown the convection
struggling to advance much further west than Chicago away from the
stronger height falls. Without any forcing locally and no shortwaves
to speak of during the evening, think convection will struggle even
with peak heating as skies begin to clear out somewhat.
Tonight through Friday will focus on the warm frontal positioning
and shortwaves/MCSs that will ripple along the front for possible
showers and thunderstorms. Models have shifted north with the
positioning of the surface front which in turn refocuses the
developing isentropic forcing north. A brief shortwave ridge
rounding the base of the Hudson Bay low will allow the jet to arch
northward as well which will steer the approaching shortwaves
further north as well. All this leads to shifting the pops north
which really only leaves the Saginaw Valley and northern Thumb with
a short at precip through Thursday. Will highlight the period from
09-15Z Thursday for the best opportunity as the shortwave lifts
through northern lower aided by nocturnal low level jet and next
surge of theta e. The rest of the afternoon will likely dry out for
everyone again but with the front just to the north will leave a
slight chance for the extreme north.
The front will start to sag southward into mid MI Thursday night as
a strong trough rotates around the Hudson Bay low giving it a push.
It should passing through southeast MI by Friday afternoon which
will be the next chance for showers and thunderstorms. Should see a
good thermal gradient across southern MI on Friday with the front
draped across the region. This will mark the end of the current
stretch of 80 degree days as highs north of I69 will struggle to
reach 70 with strengthening northeast flow off Lake Huron. Timing of
the front will decide just how warm the Metro Detroit area can get
before cooling back off.
High pressure over Ontario will keep surface flow with an easterly
component locally over the weekend. Sharp NW/SE low-mid level theta-E
boundary across SE MI, and cannot totally rule out some light
showers Saturday with weak positive theta-E advection and PWAT
around 1.5 inches, but at this point expect most of the weekend to be
dry. Low predictability early next week with guidance indicating a
cutoff low taking shape somewhere to our west over the Northern
Plains/Upper Midwest, with meridionally-oriented moisture plume
ahead of it. Eastward progression of these features will determine
rain chances early next week, and not a whole lot of model consensus
at this point, so chance PoPs early next week will suffice for now.
Despite rather warm mid-level temps, easterly surface flow is
expected to keep temps in check near or slightly above normal.
MARINE...
A front will remain stalled over the northern Great Lakes tonight
through Thursday. An active pattern of showers and thunderstorms
will be the primary marine weather impact, mainly over northern Lake
Huron, while wind and waves remains light/low over other marine
areas. That will change Thursday night and Friday as the front
settles southward into Ohio and opens moderate northeast flow over
all areas. The long fetch of onshore, unstable flow over southern
Lake Huron and into Saginaw Bay will likely produce waves exceeding
SCA levels through Friday night before high pressure settles in
Saturday.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&
$$
AVIATION.....SC
DISCUSSION...DRK/DT
MARINE.......BT
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Forecast discussion for routine afternoon forecast issuance
.SHORT TERM...Tonight and Thursday
Issued at 226 PM CDT Wed Sep 21 2016
The latest RAP analysis and satellite/radar imagery show a surface
warm front snaking from southern Minnesota to northern Illinois
early this afternoon. Showers and thunderstorms continue to fire
along the boundary over the same areas that received heavy rainfall
last nite, namely southeast Minnesota and southern Wisconsin.
Additional storms are firing over western Wisconsin in a region of
low level moisture convergence. These storms will likely continue
to develop and push into the I-39/route 51 corridor later this
afternoon. An isolated severe storm will be possible from Lincoln
to Waushara counties with mu capes above 1000 j/kg and 0-6 km shear
of 45-50 kts. As a weak shortwave lifts across the Plains and into
the western Great Lakes tonight, thunderstorm trends and potential
for heavy rain/severe weather are the main forecast concerns.
Tonight...An active period of weather, with an atmosphere conducive
for heavy rainfall. A weak shortwave, currently over southwest
Nebraska will lift northeast and across the region late tonight.
Ahead of the shortwave, a strengthening 30-40 kt low level jet is
anticipated to ride over the slowly northward advancing warm front
later this afternoon into this evening. With ample instability and
shear as shown on mesoanalysis imagery, showers and thunderstorms
are expected to develop and expand upstream of the current
thunderstorm activity over southern and central Minnesota, before
sliding east through the night. Elevated capes of 1000-1500 j/kg
suggest a severe storm cannot be ruled out through the evening,
especially over areas from west of the Fox Valley and south of route
29. In addition, long duration of forcing combined with plentiful
moisture (pwats of 1.75 to 2.00) continues to imply that a flood or
flash flood threat is possible. The latest guidance shows that
central WI from Lincoln to Waushara counties have the most risk for
receiving heavy rainfall, with amounts of 1-3 inches possible
(locally higher). Though concerns are not as high for flooding
further east within the flood watch, potential for heavy rain will
remain, especially over the southern Fox Valley where rainfall over
an inch has already fallen early this morning. Temps ranging from
the mid 50s north to mid 60s south.
Thursday...Model guidance continues to show that the front will
remain stalled over central and northeast Wisconsin. Though weak
shortwave impulses will be passing to the east during the morning,
periods of showers and storms will likely continue through the day.
Weaker forcing and instability suggests rainfall only has a limited
potential to be on the heavy side, so thinking additional amounts of
a quarter to a half inch will be possible, locally higher in storms.
With the rainfall and clouds, temps will remain cooler in the mid
60s to mid 70s.
.LONG TERM...Thursday Night Through Wednesday
Issued at 226 PM CDT Wed Sep 21 2016
A frontal boundary that was just to the southwest of Wisconsin
early this afternoon is the main concern through the end of the
week before a surface low pressure system brings a cold front into
the state.
The approaching warm front will keep at least a chance for
showers and thunderstorms in the forecast through Saturday
morning. Central and east central Wisconsin will be the main
concern for heavy rainfall since the front is expected to be in
that general area before it finally makes a stronger push to the
northeast and clears the state late in the week. Looks like there
could be a period of dry weather, with not even a slight chance
POP, Saturday afternoon but confidence in timing is low.
Have shower and thunderstorm chances returning with the approach
of a cold front from the west, which may take a while to clear the
state. The 12Z GFS, ECMWF and Canadian all started to exhibit
significant differences for early next week but all looked quite
wet through the end of the forecast period.
Highs during the day should be within a couple of degrees of
normal, and lows should be warmer than normal due to all of the
clouds and rain.
&&
.AVIATION...for 18Z TAF Issuance
Issued at 1204 PM CDT Wed Sep 21 2016
Periods of showers and storms will impact the region later this
afternoon through Thursday morning as a warm front lifts northward.
Though storms are not expected to be severe, a few strong storms
could move across the central WI taf sites, and produce small hail
and gusty winds to go along with heavy rainfall. Cigs and vsbys are
expected to deteriorate as the showers and storms arrive this
evening, and only expected very slow improvement on Thursday morning.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through Thursday evening FOR WIZ018>020-030-
031-035>040-045-048>050.
&&
$$
SHORT TERM.....MPC
LONG TERM......MG
AVIATION.......MPC
Area Forecast Discussion
National Weather Service Wilmington NC
606 PM EDT Wed Sep 21 2016
.SYNOPSIS...
The remnant circulation of former Tropical Storm Julia will maintain
scattered showers through Friday. Drier weather should develop
Saturday as high pressure pokes in from the north. A cold front will
move through early Sunday, followed by several days of onshore winds
and slightly cooler temperatures next week.
&&
.NEAR TERM /THROUGH TONIGHT/...
As of 300 PM Wednesday...Low pressure over southeast NC will
drift slowly SW becoming more elongated along the SC coast by this
evening with a trough extending northward from center of low. An
easterly on shore flow will exist on the front end of low/east
side of trough along the coast and continued NE-N flow inland, on
back end of low/west side of trough. This pseudo warm front/trough
will provide a warmer easterly flow and will allow for some
drying and thinning of the clouds. At the same time energy will
continue to rotate around this upper low combining with deeper
layer moisture inland to produce showers and isolated
thunderstorms wrapping around to the S-SE into Northeast SC. Pcp
water values show a plume of deeper layer moisture with values
over 2 inches running from VA/NC coast around to the SW to S
through central NC/SC. Coastal NC will have some drier air
wrapping around from the S to SE with pcp water values down closer
to 1.7 inches this aftn. Overall, instability will remain marginal
due in part to significant cloud cover, so although clouds will
blanket most of the area, expect modest QPF amounts of most areas
with greatest amounts aligned inland mainly just west of I-95
corridor. If areas break out along the coast, expect some heating
and differential heating to produce some further convective
development mainly across central portions of forecast area inland
from the coast.
As this deep low drifts S-SW toward the GA/SC coast through
tonight, some deeper layer moisture will wrap back around over
the Cape Fear region and should increase shwr activity over the
eastern portions of the forecast area overnight as moisture and
showers spread from the coastal waters along the coast in a
deeper E-SE flow. Expect mainly light to moderate rain but some
embedded heavier rain amounts are possible. Overall the cool pool
aloft and continued moist flow will produce plenty of clouds and
potential for pcp through tonight.
Temperatures inland in northerly flow on back side of low will
remain in the mid 70s this aftn while temps along the coast will
reach over 80 especially where some breaks or thinning in the
clouds occurs.
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
As of 300 PM Wednesday...The persistent mid to upper low will
become more elongated and may drift westward before opening up
into a trough along the east coast and moving off shore by Fri
night. The center of the low will remain south of the area with
trough extending northward maintaining a deeper on shore flow
through the period. The trough looks like it will be just along or
off shore which will keep a N-NE flow over much of the area but
should see more of an E-SE flow at times along the coast and off
shore as trough and diurnal shifts take place. Pcp water values
will remain up above 1.75 inches through much of the period in a
very moist air mass. With such deep layer moisture and a deep
low/trough over the region through the period, expect unsettled
weather to continue. While POP areal coverage should remain
scattered most of this period, there will be bands of showers with
more moderate to heavy rain across portions of the area associated
with upper level energy rotating around over the region.
Drying will finally take place late Fri into early Saturday as
trough finally moves off to the east. Skies will begin to clear
from west to east leaving partly cloudy skies by Fri night over
most places. Max temps will reach near or around 80 during the
afternoons overnight lows near 70 Thurs night but slightly lower
Fri night as some clearing occurs.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
As of 300 PM Wednesday...The upper levels will certainly not look
anything like summer with a very amplified trough-ridge-trough
pattern expected to develop across North America. Models have
struggled to form a consensus over the past few days with details,
however the new 12z GFS may be on to something with its depiction of
an Omega block developing by Tuesday. Due to this blocked pattern,
the potential of a strong cold frontal passage late this month is now
in jeopardy and we may remain in the tropical/subtropical humidity
through the remainder of September.
A 500 mb ridge centered across the Mississippi Valley on Saturday
will only slowly work east into the Carolinas by Tuesday and Wednesday.
A deep upper level low moving across the Canadian Maritime provinces
will push a cold front southward along the East Coast, reaching the
Carolinas early Sunday. The surface high behind this front won`t dive
south, and in fact may only reach coastal New England by late Tuesday
or Wednesday. This will create an extended period of onshore winds
and the potential for scattered showers as a band of convergence
behind the old front could settle across the area, coincident with at
least shallow Atlantic moisture.
&&
.AVIATION /00Z THURSDAY THROUGH MONDAY/...
As of 00Z...A low level convergence boundary will affect LBT and FLO
through about 01Z, with most of the convection dissipating after
that. Overnight, fairly high confidence for IFR conditions at all
locations with abundant low level moisture. Surface low pressure
will have convection on the increase toward morning at ILM, well
depicted by the HRRR model. This precip will likely continue through
early afternoon, spreading inland after that. Light mainly northeast
flow through midday on Thursday.
EXTENDED OUTLOOK...Isolated to scattered afternoon
and early evening convection possible underneath the cutoff upper
low through Friday. MVFR/IFR morning stratus/fog possible each day
through Sunday.
&&
.MARINE...
NEAR TERM /THROUGH TONIGHT/...
As of 300 PM Wednesday...A deep low over the Cape Fear region will
drift southwest through tonight. This will result in a weak pressure
gradient with winds 10 knots or less through the day. Wind direction
will also be somewhat variable, but in general, an onshore flow will
continue as the low center drifts southwest. It should kick back to
a more northeasterly direction close the coast on the back end of
the low and more E-SE farther off shore on the front end of low. Mid-
level dry air over the waters is expected to limit storm development
today, but should increase overnight in deeper on shore flow. Seas
will remain less than 3 ft mixing in with some longer period SE
swells arriving tonight.
SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
As of 300 PM Wednesday...Low pressure will weaken south of the
waters with trough aligned up the coast through the period.
This will keep an on shore flow through the period and depending
on the exact position of the trough, the winds will fluctuate
between E-SE to E-NE over the waters...remaining 10 kts or less.
Winds will turn more northerly and pick up a bit by Fri night as
low finally moves off to the east. Showers and isolated TSTMS
will remain in the mix. Seas will basically remain 3 ft or less
with a slight, slow and steady rise as a longer period up to 12
second SE swells mix in.
LONG TERM /SATURDAY THROUGH MONDAY/...
As of 300 PM Wednesday...Julia`s remnants should be long gone from
the weather map by Saturday. High pressure dropping southward from
the southern portion of Hudson Bay will push a cold front through the
Carolinas early Sunday. This front will sink to coastal Georgia
Monday with easterly winds developing across the Carolinas. Scattered
showers should develop mainly behind the front beginning Sunday
night.
Wave heights of 2-3 feet are expected south of Cape Fear Saturday
into the first half of Sunday, with the potential for 3-4 foot seas
near and north of Cape Fear due to residual swells emanating from
distant Tropical Storm Karl. By Sunday night modest onshore winds
will create the potential of shorter period 2-4 foot waves away
throughout the area, continuing into Monday.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...None.
MARINE...None.
&&
$$
SYNOPSIS...TRA
NEAR TERM...RGZ
SHORT TERM...RGZ
LONG TERM...TRA
AVIATION...43
Area Forecast Discussion
National Weather Service Northern Indiana
329 PM EDT Wed Sep 21 2016
.SYNOPSIS...
Issued at 326 AM EDT Wed Sep 21 2016
There is a slight chance of a thunderstorm early this evening over
northwest Indiana and southwest Lower Michigan. Otherwise it will
be dry and warm again. Low temperatures tonight will drop into the
lower 60s. Partly to mostly sunny skies are expected Thursday with
highs once again rising well into the 80s. A weak cold front is
expected to drop south later Friday and Friday night. This will
bring slightly cooler temperatures for the weekend...but highs are
still expected above normal in the middle 70s. The next chance for
a widespread rain will not be until early next week.
&&
.SHORT TERM...(This Evening through Thursday)
Issued at 324 PM EDT Wed Sep 21 2016
So far upstream convection has behaved as advertised and continues
to weaken as it moves east out of deeper instability and away from
stronger synoptic forcing. HRRR still wants to occasionally develop
an isolated cell in our north through 00z with modest instability
and decent mid level lapse rates. So far outflow boundaries have not
been strong enough to force any development. Vis sat loop does show
some cu trying to develop over the northwest in vicinity of where
HRRR has tried to convect. Also watching remnant convection sliding
southeast from northern Illinois. Will carry the slight chance pops
over the north and northwest through 00z followed by dry conditions
for the overnight period as main front lifts north. This boundary now
looks to reside far enough north on Thursday that pcpn chances will
be 10 percent or less and upstream convective complex tonight over
WI to stay north of our area tomorrow. Should still see some cloud
debris but expect more sun than today and temps will once again
recover nicely well into the 80s. ECE MOS kicking out upper 80s over
parts of the region but will hold shy of this in the mid 80s with
the potential for the debris clouds at times.
&&
.LONG TERM...(Thursday Night through Wednesday)
Issued at 324 PM EDT Wed Sep 21 2016
Upper level pattern to transition from zonal to a meridional flow
through the period. This will complicate forecast by early next
week with various model solutions revolving around cut off upper
low and an occluded front.
Backdoor front will begin to slide into the area later Friday and
Friday night. Moisture limited and not much synoptic forcing. Slight
chance pops continue in the northeast. This boundary will bring
northeast winds and cooler temps through the weekend but still above
normal for late September. Highs in the middle to upper 70s still
expected.
More uncertainty exists with potential frontal boundary early next
week. GFS and ECMWF continue to have differences with respect to a
cut off upper low over the central CONUS and how an occluded front
associated with it will translate east. GFS continues to be faster
model while ECMWF remains slower. These differences being dictated
by large trough off the northeast CONUS and stout ridge between that
trough and the developing upper low over northern Plains. GFS wants
to push sfc boundary through the ridge while ECMWF stalls this
boundary to our west. For now will be using the Superblend init
until more certainty develops. Preference is toward ECMWF as GFS has
a bias of breaking down ridges and seems to be doing that here as
well. Temps remain mild in the 70s but should trend closer to normal
next week.
&&
.AVIATION...(For the 18Z TAFS through 18Z Thursday Afternoon)
Issued at 135 PM EDT Wed Sep 21 2016
Focus for convection should remain primarily north and west of the
local area this period as effects of broad mid level ridge and
capping issues persist. Outflow/convective vorts from upstream
convection may be enough to support an isolated shower or storm
at KSBN late this afternoon, but confidence remains too low for
inclusion at this time. Otherwise, light south/southeast winds to
become light and variable tonight, and then south-southwest 5 to
10 knots Thursday. Some potential of some shallow fog once again
early Thursday morning, but not expecting significant impacts at
this time.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...NONE.
&&
$$
SYNOPSIS...Lashley
SHORT TERM...Lashley
LONG TERM...Lashley
AVIATION...Marsili
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Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
449 PM EDT Wed Sep 21 2016
.SYNOPSIS...
High pressure will build over the region through early
Thursday then weaken through Friday. A cold front will move
through the area early Saturday. High pressure builds again over
the region early next week.
&&
.NEAR TERM /THROUGH THURSDAY/...
A few light showers are seen on radar over southern MD and the
Fredericksburg area, but these are expected to dissipate early
tonight as high pressure builds in and air mass dries out. Biggest
question for tonight is whether high clouds will thin out and
skies become clear. Latest 12Z ECMWF and HRRR simulated cloud IR
imagery show high clouds sticking over the area around much longer
than earlier runs with clearing not indicated now until after
midnight or early Thu. Fog is not expected as models show sfc
dewpoints dropping tonight.
A few high clouds still possible Thu if the ECMWF is correct, but
any high clouds are likely to be thin enough for a mostly sunny
day. High pressure will be in control, although it will be
weakening.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
Weak high pressure in control during this period. Temperatures
are expected to warm up into the upper 80s and possibly reach 90F
in a few spots on Fri.
&&
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Surface cold front will likely have passed south of the region by
Saturday morning, behing pushed along by a 1030+ mb high pressure
center originating near Hudson Bay Canada. The center of this high
and coolest air will pass over New England, but much cooler
weather is expected over the Mid-Atlantic as well especially
during the second half of the weekend into early next week.
Onshore flow may result in elevated humidity and low clouds and
drizzle especially early next week. The operational GFS runs have
been the quickest with an approaching cold front next week but have
been trending slower towards a GEFS/EC blend. A slower solution
seems more likely given the large blocky nature of the high pressure
center that will be stationed just northeast of the region next
week. This should keep more substantial rain chances at a minimum
through much of the forecast period.
&&
.AVIATION /21Z WEDNESDAY THROUGH MONDAY/...
VFR conditions next 24 hrs, except for possible 3-5SM mist at
KCHO.
Mainly VFR expected Saturday with northerly winds 10 to 15
knots. Sub-VFR possible later in the weekend with lower clouds as
winds become easterly around 10 knots.
&&
.MARINE...
Winds will gust to around 15kt in the lower Bay through midday
Thu before they begin to diminish.
A pressure surge, aided by northerly channeling, will likely
push winds into Small Craft Advisory territory on Saturday. Winds
should gradually diminish and veer to the east Saturday night into
Sunday.
&&
.TIDES/COASTAL FLOODING...
Water levels running less than a foot above astronomical normals,
but departures are on the rise. Nonetheless this is proving to be
enough to flirt with minor inundation thresholds at senstive
locations. Have issued Coastal Flood Advisory for St. Marys and
Anne Arundel Counties. We still have a couple of hours to ensure
that the current forecast remains on track in the upper tidal
Potomac. If it does, we will need to issue for DC/Alexandria as
well.
Elevated water levels persist through the rest of the week due to
low pressure off the Carolina coast.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Coastal Flood Advisory from 8 PM this evening to midnight EDT
tonight for MDZ014.
Coastal Flood Advisory until 8 PM EDT this evening for MDZ017.
VA...None.
WV...None.
MARINE...None.
&&
$$
SYNOPSIS...LFR
NEAR TERM...LFR
SHORT TERM...LFR
LONG TERM...DFH
AVIATION...LFR/DFH
MARINE...LFR/DFH
TIDES/COASTAL FLOODING...HTS/LFR
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
411 PM CDT WED SEP 21 2016
.SHORT TERM...(This evening through Thursday)
Issued at 326 PM CDT Wed Sep 21 2016
The next 12 hours will feature widespread showers and
thunderstorms across a large portion of Minnesota and western
Wisconsin. While a few straight-line wind gusts and a weak tornado
are not impossible, the two greater threats this evening are
heavy rain with the potential for flash flooding and hail between
1-2" in diameter.
You don`t have to be a meteorology major to find the main warm
front this afternoon in Minnesota. North of a line from roughly
Granite Falls, to the southern Twin Cities metro, to Eau Claire
there is overcast skies temperatures in the 60s and northwest
surface winds. South of this line, the winds are southerly and
temperatures are in the 70s and 80s with dewpoints in the 70s. The
instability gradient is stretched out along this line with max
values near 3500-4000 J/kg (SBCAPE and MLCAPE) in far south
central MN and near 0 J/kg in the far northern TC metro. Good
elevated instability and steep mid-level lapse rates extends well
north of the surface boundary. In addition to the building
instability, the 925-850mb moisture transport and warm advection
have increased quite a bit over the past couple hours. The FGEN
in this area has also increased since mid afternoon. The result
has been the expansion of thunder along or north of the boundary.
Storms have been efficient rainfall producers with rain rates
between 2-3". The storms have also been efficient hail producers
as well, not too much of a surprise given the instability in the
hail growth zone, shear profile, and due to the fact that the
surface temperatures are in the 60s along and north of the
boundary. We expect the radar scope to continue to expand in
coverage this evening. The placement of the Flash Flood Watch is
still looking good, although some of the convective allowing
models are developing convection back farther to the southwest.
Though the HRRR has admittedly struggled with the short term
trends. Settle in, its going to be a busy night for weather in
MN/WI over the next 12 hours. There will likely be elevated hail
and heavy rain north of the front that move east northeast, but
there will also likely be a broken line of storms that form along
the boundary and sag south with time.
.LONG TERM...(Thursday night through Wednesday)
Issued at 326 PM CDT Wed Sep 21 2016
Highly amplified flow in the extended will evolve into a cut off low
which is a pattern that has high uncertainty. For that reason and
given the high impact weather expected in the next 24 hours, did not
stray from blended guidance in the extended period. There`s a few
highlights below.
The warm front responsible for the heavy rain will be laid out
somewhere along I-90. Storms should continue to Thursday night. On
Friday the warm front will lift northward and showers and
thunderstorm chances will be tied to the front. There will be warm
and dry conditions in the warm sector, but this will be short-lived
as a cold front moves in Saturday and brings a few showers and
thunderstorms.
Beyond this period, the upper level wave will cut off and bring a
prolonged period of clouds and light rain. As mentioned above, there
is uncertainty in this pattern, so would not be surprised if the
forecast changes. The GFS is a bit quicker with the cutoff low, but
the ECMWF catches up by the middle of next week.
&&
.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 113 PM CDT Wed Sep 21 2016
This is a messy weather pattern with a lot of moving parts. There
is a strong warm front across the area. This runs east to west
from KRWF to KMSP to KEAU...along and north of this line winds are
out of the northeast and there is MVFR/IFR ceilings. South of this
line winds are out of the southeast, conditions are VFR and there
is even sunshine. We expect thunderstorms to become more numerous
across MN and WI this evening. Thunderstorms with heavy rain are
likely at KRNH/KEAU/KMSP and possible at KAXN/KSTC/KRWF.
KMSP...
Besides the scattered to broken low clouds in the metro. It will
be quiet for the next couple hours at the airport. However, we
expect a busy evening with widespread storms developing in eastern
MN.
/OUTLOOK FOR KMSP/
Fri...MVFR/SHRA possible. Wind E 5-15kts.
Sat...VFR with MVFR/TSRA likely. Wind SE at 10g15kt.
Sun...VFR. Wind W-SW 10g20kt.
&&
.MPX Watches/Warnings/Advisories...
WI...Flash Flood Watch through Thursday evening for WIZ024-026-028.
Flash Flood Watch through Thursday morning for WIZ014>016-023-
025-027.
MN...Flash Flood Watch through Thursday evening for MNZ067-069-070-
074>078-082>085-091>093.
Flash Flood Watch through Thursday morning for MNZ051>053-
059>063-066-068.
&&
$$
SHORT TERM...CLF
LONG TERM...JRB
AVIATION...CLF
HYDROLOGY...CLF
Area Forecast Discussion
National Weather Service Portland OR
259 PM PDT Wed Sep 21 2016
.SYNOPSIS...An upper level trough extends from southern BC to the
Oregon coast, keeping cool and somewhat unsettled weather across the
forecast area. This system will continue to dig south into northern
CA tonight before moving across the Sierra Nevada Thursday. A few
showers and perhaps a thunderstorm will linger into the evening, but
most showers should decrease tonight with the loss of daytime
heating. A few lingering showers are possible in the Cascades
Thursday, but Thursday should be dry for the most part. The next good
chance for widespread rain comes Friday as another moist Pacific
frontal system aims toward the Pacific Northwest. High pressure
rebuilds over the region for the start of next week.
&&
.SHORT TERM...(Tonight through Saturday)...Visible satellite imagery
shows cumulus buildups forming over the higher terrain. This due to
an upper trough extending from southern BC to the coastal waters near
the OR/CA border, providing relatively cool air aloft for a little
bit of instability. 21z RAP surface analysis shows a couple hundred
J/kg of sfc-based CAPE across much of NW Oregon, with only a small
amount of CIN - mainly closer to the north coast. With little to no
convective inhibition, expect showers to continue to develop mainly
over the higher terrain this afternoon. Convective allowing models
suggest there is a chance that a couple of these showers could form
or drift over the Willamette Valley, so we left a mention of showers
into this evening for all but our northern coastal zones. With some
model soundings showing the potential for deeper convection with tops
>20kft, cannot rule out a couple lightning strikes from the heavier
showers. Kept the thunder mention limited to the higher terrain south
of a Newport-Mt Hood line, where instability should be most ripe for
convection. With model soundings showing very little wind up to
500mb, expect little to no storm motion with any cells that develop.
As a result, it appears any convection would be the pulse variety,
lasting 30-60 min or less and dumping a localized burst of rain. In
other words, expect hit-or-miss showers this afternoon with the
better chance being in the higher terrain south of Portland.
Most showers should diminish quickly with the loss of daytime
heating, though there is some potential showers or rain will continue
over the Cascades as the upper trough axis passes through later
tonight. If skies remain clear enough, expect another cool morning
with areas valley fog Thursday...similar to the past couple mornings.
Models then show decent agreement that our upper trough will evolve
into a closed upper low over the Great Basin by Thursday afternoon.
Drier northerly flow behind this system will likely result in less
shower coverage Thursday, and mainly over the Cascades. Temperatures
could be a bit tricky Thursday afternoon, as a lot may depend on how
quickly any valley fog/low clouds can burn off. The air mass aloft
remains cool...with 850 mb temps generally around +5 deg C across the
forecast area per the latest NAM/GFS runs. Suspect that either way,
temperatures will struggle to break out of the 60s Thu... perhaps a
couple spots will reach the lower 70s.
Thursday night should start off clear to partly cloudy and cool due
to shortwave ridging, so some valley locations could see some fog
develop before high clouds increase in advance of the next Pacific
frontal system. This could result in a dreary day Friday with temps
struggling to get much above 60 degrees. The incoming system is
showing a good tap into tropical moisture at the moment, with
precipitable water (PW) values in excess of 2 inches embedded within.
While the splitty flow pattern will probably keep the deepest
moisture plume from affecting our area, it does appear enough
moisture will hang on to provide some decent isentropic lift over our
existing cool air mass. This should be enough for at least some rain,
so we bumped up our PoPs into the likely category Friday. Rainfall
amounts will probably be modest, as the split-flow pattern will keep
the best jet dynamics out of our forecast area. 18z NAM does still
hold the front together enough for some gusty winds on the beaches
and headlands Friday morning.
Any rain should gradually come to an end Friday night and Saturday as
models show good agreement in having a strong upper ridge build north
across the Pac NW from California over the weekend. While 850mb temps
warm up very quickly in this pattern, we will need to keep an eye on
valley inversions possibly keeping temperatures cooler than they
otherwise would be. Especially if we receive additional rainfall,
night and morning valley fog may be stubborn... we are getting to
that time of year. Autumn starts at 7:21 am local time tomorrow
morning. Weagle
.LONG TERM...(Saturday night through Wednesday)...Ridging and high
pressure will dominate Sunday and Monday, with offshore winds
keeping Southwest Washington and Northwest Oregon sunny and dry.
We`ll see temperatures jump up above normal as well, with highs in
the low-to-mid 80s in the Willamette Valley and 70s along the Coast.
By Tuesday, the ridge starts to flatten as it starts to get pushed
off to the east by an approaching trough. Tuesday will probably be a
transition day with clouds returning to the Coast, but inland should
remain mostly sunny a bit cooler. Trough should at least bring
cooler, more typical Fall weather for later next week, if not a
little bit of rain to far northern portions of our area. -McCoy
&&
.AVIATION...Upper low will gradually shift over the region tonight
and early Thu, but not much in way of moisture. Will see cumulus
clouds and even a few isolated showers, mainly over Oregon
Cascades and Coast mtns. Instability not great, but could be
enough to trigger an isolated thunderstorm over the Oregon
Cascades until 03z tonight. Mix of clouds and clear skies tonight
but think will see increasing MVFR along the coast and the
interior again later tonight as onshore flow increases a bit.
KPDX AND APPROACHES...VFR with a few cumulus, May see an isolated
shower or two, but best threat will be to east over the Cascades.
Generally dry overnight and Thu, but will have increasing MVFR
after 10z as onshore flow increases.Rockey.
&&
.MARINE...Weak high pressure over the coastal waters will
maintain overall northerly winds at 15 kt or less through
Thursday, with west swell 4 to 6 ft.
A moderately strong cold front will approach later Thu night and
Fri, and move across the waters late Fri am into the early
afternoon. Will see southerly winds increase, with gusts 25 to 35
kt expected. No advisory for those winds at this time, but will
likely hoist Small Craft Advisory or possibly a Gale Watch on Thu.
Winds and swell will push combined seas to around 10 ft on Fri,
with seas gradually subsiding Sat. High pressure returns for the
rest of the weekend, with northerly winds generally 10 to 20 kt.
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...None.
&&
$$
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This discussion is for Northwest Oregon and Southwest Washington from
the Cascade crest to 60 nautical miles offshore. The area is commonly
referred to as the forecast area.
Area Forecast Discussion
National Weather Service Pueblo CO
332 PM MDT WED SEP 21 2016
.SHORT TERM...(This evening through Thursday)
Issued at 255 PM MDT Wed Sep 21 2016
...A Warm and Breezy Thursday...
Current water vapor imagery and upper air analysis is indicating
moist southwest flow aloft across the state, as remnant moisture
from tropical system Paine continues to lift out across the region.
Water vapor imagery is also indicating drier air embedded within the
flow across the Desert Southwest moving into western New Mexico and
western Colorado, ahead of an upper trough digging across the West
Coast at this time. Regional radars indicating isolated to scattered
showers lifting north and east across the region, with a few
thunderstorms across northwestern New Mexico at this time.
Tonight and tomorrow...Latest models remain in fairly good agreement
with southwest flow aloft slowly increasing across the region
through the day tomorrow, as digging upper trough across the West
Coast carves out an upper low across the Great Basin tomorrow
afternoon.
With that said, should continue to see showers with a few embedded
thunderstorms moving across the area through the rest of the
afternoon and into the early evening, with HRRR remaining consistent
with the best coverage of storms being across the Pikes Peak region
and the Raton Mesa region into Baca County. Showers and storms to
diminish through the late evening, with loss of solar heating.
However, could see some showers developing across the ContDvd and
especially the southwest mountains, into early tomorrow morning,
with increasing orographic flow. Overnight lows to be at or above
seasonal average, especially across the eastern plains, where lee
troughing will keep breezy southerly winds across the far se plains
overnight.
Will see more sun across the area early tomorrow, and with the
increasing flow aloft and lee troughing across the plains, should
see breezy southerly winds mixing across the area through the late
morning and afternoon. Mid and upper level moisture slowly increases
across the area again ahead of the Great Basin system, along with
southerly low level winds across the plains keeping low level
moisture in place, owning to another round of isolated to scattered
afternoon showers and storms, with the best coverage over and near
the higher terrain. Models continue to suggest near record high
temperatures in the 80s to lower 90s across the plains for tomorrow,
with highs in the 60s and 70s across the higher terrain and mainly
40s and 50s at the peaks. Current records for tomorrow are 85F at
ALS...88F at COS and 93F at PUB.
.LONG TERM...(Thursday night through Wednesday)
Issued at 255 PM MDT Wed Sep 21 2016
...Critical Fire Weather conditions I-25 corridor...Severe
thunderstorm potential eastern plains...and snow possible higher
mountains Friday...
Western U.S. upper low will move across the Great Basin Thursday
night before lifting northeastward into WY and MT Friday and
Friday night. Deep southerly flow across the plains will advect 50
dewpoints northward into the southeast plains Thurs night into
Friday morning. Initially will see some showers confined to the
mountains Thurs night and Fri with snow levels down to around
12kft at times along the continental divide. Dry air moves in
Friday afternoon as the trof axis moves across...which shallows out
the moisture along the continental divide. By this time...westerly
winds will be spreading eastward into the plains...sharpening up a
dry line just east of the I-25 corridor. All areas will see gusty
west to southwest winds west of the dry line...and gusty southerly
winds to the east of the dry line. CAPE values could be up to
around 1000 J/kg (according to the NAM12) with deep layer shears
around 30-40 kts. This will lead to a potential for severe
thunderstorms across the eastern counties including...Kiowa...
Bent...Prowers and Baca. Severe wind gusts and large hail will be
the primary storm threats.
To the west...RHs dropping to around 15 percent...and
the dry fuels will combine with gusty winds up to 40 mph to
create the potential for critical fire weather conditions Friday
afternoon and evening along the I-25 corridor. There are still
some questions as to the position of the dry line and how low
surface dew points will drop...however NAM12 seems too moist which
is its bias...and have leaned grids towards the drier GFS and EC
solutions for locations west of the dry line. For now have
restricted the Fire Weather Watch to the southern I-25 corridor
and a couple counties bordering to the east...but its possible
that the watch may need to be expanded northward and eastward a
bit more. Will let later shifts make any needed adjustments.
As the trof axis lifts out to the north Friday night...should see
drying conditions from west to east overnight. Any snowfall into
the mountains looks brief and relatively light...with spotty
amounts of an inch or two possible above 12kft. The San Luis
Valley could see a fairly widespread hard freeze Friday night.
While the main upper low lifts off to the northeast...more energy
digging into the base of the trof across CO will keep generally
unsettled weather over the region through the weekend. A cold
front will drop through the region on Saturday with another surge
of colder air for Saturday night. Models keep majority of
precipitation across the southeast mountains and adjacent plains
where H7 temperatures dropping to 0 to -2C could drive snow levels
down to 9kft or a tad lower Sat night and again Sunday night. EC
and GFS differ with QPF during these periods...with EC on the
wetter side. Hard to say at this point how much snow will fall
across the southeast mountains...but at this point a few inches
of wet snow across the higher elevations look possible as GFS has
trended back towards a wetter solution.
Models shift the upper low eastward into the plains early next
week...though differ with the track as GFS keeps the upper low
center to the north across the Dakotas through Wed...while ECs
track is farther south. Either way...CO is on the back side of the
system with drier but cooler northerly flow. This will keep below
normal temperatures across the region through the longer ranges.
-KT
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 255 PM MDT Wed Sep 21 2016
VFR conditions expected to persist at COS, PUB and ALS over the next
24 hours. Monsoonal moisture embedded within the west to southwest
flow aloft will keep scattered showers and thunderstorms in the
forecast across the higher terrain with more isolated storms
possible across the lower elevations through the evening, though
probability of storms affecting terminals too low to include in
TAFs. Breezy south to southwest winds of 15-20kts expected at
terminals through the evening. Less cloud cover expected tomorrow
morning, with breezy south to southwest winds and isolated
afternoon showers and storms again possible at the terminals.
&&
.PUB Watches/Warnings/Advisories...
Fire Weather Watch from Friday afternoon through Friday evening
for COZ227>232.
&&
$$
SHORT TERM...MW
LONG TERM...KT
AVIATION...MW
Area Forecast Discussion
National Weather Service Blacksburg VA
303 PM EDT Wed Sep 21 2016
.SYNOPSIS...
An upper low will meander across the eastern Carolinas through
Thursday before finally weakening and shifting offshore by the end
of the week. High pressure will gradually build in from the west
Friday into Saturday. A backdoor cold front drops south through
the area late Saturday into Saturday night followed by cooler
high pressure Sunday into early next week.
&&
.NEAR TERM /THROUGH THURSDAY/...
As of 245 PM EDT Wednesday...
Closed low over the Southeast Coast will continue to interact with
the Post tropical remnants of Julia during the period. As been the
case for a couple of runs, the ECMWF and NAM remain slightly west
of the GFS. One of the forecast challenges is the western edge of
the moisture and the sharp gradient in showers. The HiResw-arw-east,
wrf-arw-rnk, RAP and HRRR support the mention of isolated to
scattered showers in southeast portions of forecast area this
afternoon into tonight.
The upper low remains fixed across the coastal Carolinas tonight
into Thursday morning. believe that shower coverage may wrap
tighter towards the coast tonight with drier air pushing into
northwest portions of forecast area. Cloud cover tonight will vary
from clear in the northwest to cloudy in the southeast. Lows tonight
will range from the mid 50s in the northwest mountains to the
mid 60s in the east.
The closed upper low will slowly weaken and lift northeast on
Thursday. The result of this transition will be even less coverage
of isolated showers across the south and southeastern portion of the
region. High temperatures Thursday will vary from the mid 70s in the
mountains to the lower 80s in the Piedmont.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/...
As of 230 PM EDT Wednesday...
Persistent upper low will finally open up and shift northeast
Thursday night in response to ridging nudging east from the
Midwest. However may still be enough moisture around with the
deformation axis on the back of the coastal system to produce a
few added showers far southeast so left in an isolated mention
early.
Otherwise expecting a drier northerly flow to take shape under weak
high pressure later Thursday night into early Saturday. This should
bring clearing/sunny skies for late week into the weekend. However
passing 500 mb trough well to the north by Saturday will propel a
backdoor cold front toward the area Saturday afternoon and into parts
of the region Saturday night. This a bit slower than previous given
strong upper ridging overhead and warmth ahead of the front that should
slow it down until Saturday night. Other than perhaps some developing
post frontal low level cloudiness by late Saturday per the GFS, deep
moisture to remain limited so not including any pops with the boundary
for now. Given gradual 850 mb warming Friday and weak compression
ahead of the front Saturday, looks like will return to above
normal highs with mostly low/mid 80s both days with most surface
based cool advection holding off until Saturday night at this
point.
&&
.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
As of 130 PM EDT Wednesday...
High amplitude blocky pattern looks to evolve later in the weekend into
next week as potential cut off upper lows develop off New England and
across the upper Midwest. This could basically sandwich the area within
a sharp shortwave ridge axis between these two features pending exactly
where the upper block develops. Differences between models continue in
regards to strength of the upper systems and subsequent speed of
surface features in this setup. However still appears will see a rather
significant backdoor cold front drop south into the region by Saturday
night/early Sunday before the boundary fades crossing into the
Carolinas. Guidance still suggests some spotty shower potential Sunday
with the front aloft nearby and developing onshore flow. Thus thinking
more clouds and spotty shower pops Sunday and southern sections Sunday
night with a shallow moisture axis lingering but iffy.
Lots of uncertainty to take shape early next week as model spread
remains large in just how fast a second cold front to the west will be
able to slide east given eastern ridging in place. Latest 12Z GFS
has continued to make a shift toward the slower ECMWF from
overnight in keeping this slow moving front west of the mountains
through midweek. However these solutions remain much slower and
stronger than the GEFS which looks too weak/fast in lifting
support out to to the north, while spilling the front quickly
east. Overall the slower scenario would keep the area in more or
less a more stable low level wedge formation per high pressure to
the north under ridging aloft. Tendency in this setup likely to
lead to more clouds and spotty showers/drizzle including much
cooler temperatures into midweek. Therefore have trended in this
direction with highs below Mos, but still mostly 70s and lows 50s-
mid 60s, although highs by early week could be only in the 60s if
more widespread low clouds do materialize.
&&
.AVIATION /19Z WEDNESDAY THROUGH MONDAY/...
As of 108 PM EDT Wednesday...
Scattered to broken MVFR clouds with patches of showers mainly east
of the blue ridge this afternoon into tonight. Northeast winds may
be breezy this afternoon into this evening with gusts to 20kts along
and east of the Blue Ridge Mountains. Winds will become light
easterly tonight into Thursday morning.
Tonight the skies will clear from northwest to southeast to a
point, but remain broken at the high cloud level overnight in the
DAN area. Model forecast soundings with easterly flow suggest
potential for low cloud development or advecting in from the east
along with patchy fog. Will keep it optimistic and go no lower than
MVFR at LYH/DAN/BLF/BCB on vsbys with IFR/LIFR at LWB late tonight.
Morning fog and low clouds will lift by mid morning, return all taf
sites to VFR conditions by Thursday afternoon. Winds Thursday
afternoon will be light and variable.
Medium to high confidence in ceilings,visibilities and winds during
the taf period.
Extended aviation discussion...
The slight chance of MVFR showers will remain just east of KLYH and
KDAN through Thursday night. VFR conditions will prevail Thursday
night outside of late night/early morning fog/low clouds. GFS/ECMWF
have been consistent in filling and lifting out the low to the
northeast on Friday. VFR conditions will prevail on Friday.
A back-door cold front will come through the Mid-Atlantic region
on Saturday. High pressure will build in for Sunday. The chance of
precipitation or any sub VFR conditions will increase through the
day Sunday and into Sunday night. Next cold front arrive by Midweek
with potential for MVFR/IFR conditions.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...JH/RAB/WP
NEAR TERM...KK
SHORT TERM...JH
LONG TERM...JH
AVIATION...KK/WP