Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/18/18
Area Forecast Discussion
National Weather Service Bismarck ND
926 PM CDT Mon Sep 17 2018
.UPDATE...
Issued at 926 PM CDT Mon Sep 17 2018
Current forecast looks good with no changes.
UPDATE Issued at 624 PM CDT Mon Sep 17 2018
The remainder of the stratus deck across southwest North Dakota
has cleared out and skies remain clear across the southern two
thirds of the state. Scattered mid and high clouds remain across
the north. Current forecast looks good for tonight.
&&
.SHORT TERM...(This evening through Tuesday)
Issued at 129 PM CDT Mon Sep 17 2018
Latest visible satellite imagery shows a stratus continuing to
erode for most of western and central ND. The exception is from
Beach to Killdeer, south to Dickinson and Glen Ullin where the
HRRR 925mb RH field delays this until 21Z-00Z. High resolution
models showing boundary layer winds not favorable for another
round of stratus tonight, although patchy fog possible at
Dickinson with a light east to southeast wind allowing a shallow
moist layer to develop late tonight. Also, there could be some
fog/stratus straddling the northern border, where boundary layer
west to northwest winds may push some stratus to the far north
toward daybreak Tuesday. The latest HRRR indicates some evidence
of this in Divide County late tonight. Otherwise, for the short
term period, a broad west-southwest flow continues with minimal
shortwave activity embedded within the flow. Will keep some
mention of isolated showers across the northwest this evening, but
overall expect a mostly clear to partly cloudy sky tonight with
mostly sunny and dry conditions Tuesday. Lows tonight will be in
the upper 30s north to lower 40s elsewhere. Highs Tuesday will be
in the 60s.
.LONG TERM...(Tuesday night through Monday)
Issued at 129 PM CDT Mon Sep 17 2018
Cooler than average temperatures remain on track in the extended
range period as noted by CPC and CIPS analogs. Highs will be in
the 60s, with the coolest day being Thursday with highs in the 50s
as showers take control over western and central ND. A 700mb
shortwave scooting along the northern border Tuesday evening/night
will result in a chance of showers north through Wednesday. The
upper flow becomes more southwest Wednesday, in advance of a more
potent shortwave trough ejecting out from the Intermountain West.
Widespread rainshowers Wednesday night through Thursday remains
on track with highs mostly in the 50s. The showers will end
Thursday night followed by a cold frontal passage Friday. Not much
if any precipitation expected with the cold front; however, warm
air advection rain/snow mix is possible in the far north and along
the border Friday night into Saturday. Elsewhere, it should be
mainly dry. Should be dry Saturday and Sunday with a more active
period developing Monday through Wednesday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 624 PM CDT Mon Sep 17 2018
A weak region of high pressure over the Dakotas and Manitoba will
maintain VFR conditions across the region through the 00Z
forecast period.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...WAA
SHORT TERM...KS
LONG TERM...KS
AVIATION...WAA
Area Forecast Discussion
National Weather Service Boston/Norton MA
1004 PM EDT Mon Sep 17 2018
.SYNOPSIS...
Conditions will change quickly very late tonight, and especially
Tuesday, when the remnants of Florence brings heavy rain along
with the threat for Flash Flooding. Ebb and flow pattern for the
remaining week on through the weekend into early next week.
Seasonable conditions followed by touches of Autumn from the
north. Shots of wet weather in-between but nothing of a washout.
&&
.NEAR TERM /UNTIL 8 AM TUESDAY MORNING/...
Leading edge of light rain moving into western New England this
evening, with heavier rainfall along the nose of a modest 850
mb jet back across central NY. Expect showers to overspread much
of SNE through the overnight period. Lightest precip will be
across SE New Eng with heavy rainfall and a few t-storms moving
into western New Eng 09-12z as the low level jet moves into the
region. Axis of heaviest rainfall through 12z will likely be
across western MA near the low level frontal boundary and deep
layer theta-e ridge axis, but some heavier rainfall may make
into northern CT as well. Max rainfall of 1-2 inches possible
through 12z.
MUCPAES forecast to increase late tonight, up to 500 J/kg, and
hi-res guidance indicates convective elements developing toward
daybreak in response to increasing instability and forcing for
ascent. While deep layer shear is marginal, approaching low
level jet will lead to increasing low level shear so will have
to watch any convection for possible rotating storms. RAP 0-1km
shear increases to 25-30 kt with 0-1km helicity 100-200 units.
Given tropical environment with high dewpoints and low LCLs,
there is a low risk for an isolated tornado toward daybreak and
through the morning across the interior. The main issue is the
low level jet and resulting shear appears to outrunning best
instability which is a limiting factor, but there appears to be
a window where both factors overlap.
&&
.SHORT TERM /8 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
* Florence remnants bring heavy rain/flash flood threat
* Low risk for a very localized/high impact severe weather event
Tuesday morning will be right in the thick of the heaviest
rainfall which should occur from generally 5 AM in the western
zones through the afternoon/early evening in the eastern zones.
Generally still expecting 1 to 3 inches of rain across the
region with localized 4 to 6 inches. Some of these heavy
downpours could potentially put down 2 to 3 inches in an hour.
Of course with this kind of rain we know poor drainage urban
flooding will be an issue. However, with rivers at their 90th
percentile, river flooding and flash flooding will be possible.
A Flash Flood Watch has been issued through the day Tuesday.
As far as severe weather goes, the threat is low but present.
We obviously won`t get much instability from heating tomorrow,
and mid level lapse rates are marginal. Synoptic models show
low level helicity values over 200 m2/s2 and an 0-1km shear
values near 30 kts. Given the circulation still associated with
the post tropical system and the strong forcing mentioned above,
we`ll have a chance for an isolated tornado or a wet microburst
event.
Tuesday night...
Showers and heavy rainfall threat finally comes to an end
overnight as the surface trough sinks to the southeast. A few
showers will linger into early Wednesday morning for the far
eastern zones as flow switches out of the northeast.
Temperatures drop into the low 60s.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
*/ Highlights...
- Ebb and flow pattern for the foreseeable future
- Wet weather chances Wednesday and Friday
- Low confidence forecast weekend onward other than a cooling
trend
*/ Overview...
Still expecting a nearly zonal mid level flow the second half of
this week into this weekend. Southern New England should be
right on the edge between a strong mid level ridge to the south,
and a cutoff low over Hudson Bay. Just a subtle shift north or
south could have a significant impact on temperatures. In
general, expecting below normal temperatures mid week, with a
warmup Thursday and Friday. Near to below normal temperatures
expected this weekend into early next week.
Precipitation-wise, widespread rain should be tapering off
Wednesday as the remnants of Florence moves out. Likely looking
at some scattered showers, mainly during the morning hours.
The next chance for rainfall after that is expected to be with a
warm front/cold front combination associated with a low pressure
moving across eastern Canada sometime Friday into Friday night.
High pressure should then take over Saturday into Sunday. The
cold front from Friday may be stalled close by, so forecast
confidence in the details heading into this weekend is not very
high.
&&
.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short Term /through Tuesday Night/...
Tonight...Moderate to high confidence.
VFR conditions lowering to MVFR/IFR as CIGs drop ahead of
Florence remnants. -RA/RA expanding after midnight with +RA
western MA 09-12z. LLWS threats emerge 220 at 40 kt 2 kft AGL
over SE coastal terminals.
Tuesday...Moderate to high confidence.
Widespread MVFR-IFR CIGs with lower VSBYs associated with RA/+RA,
a lower risk of TSRA. SW winds with gusts 20-30 kts especially
over S/SE coastal locations. Continued LLWS threats over SE New
England. Yet by midday, SW winds shifting N roughly NW to SE
over New England, wind related threats pushing offshore towards
evening.
Tuesday night...Moderate to high confidence.
Continued widespread MVFR-IFR CIGs with lower VSBYs associated
with RA/+RA, continued lower risk TSRA, all moving off SE off-
shore along with LLWS threats. N/NE flow prevailing, despite
RA/+RA elements moving offshore, MVFR-IFR CIGs remain with SCT
SHRA.
KBOS Terminal...Moderate confidence in TAF.
Cigs lower to MVFR as showers move into the region late tonight.
Rain expected to continue through the night and much of Tuesday
with mainly MVFR conditions. Still some uncertainty on exact
timing of the onset of heaviest showers and lower conditions,
including exact cigs and vsbys.
KBDL Terminal...Moderate confidence in TAF.
Conditions lowering to MVFR cigs and vsbys associated with
showers moving into the region. RA/-RA will continue through
the night and into Tuesday. Uncertainty lies with the exact
timing of onset of heaviest shower and lower conditions.
Outlook /Wednesday through Saturday/...
Wednesday: Mainly VFR, with local IFR possible. Breezy. Slight
chance SHRA, patchy FG.
Wednesday Night: Mainly VFR, with local MVFR possible. Breezy.
Thursday: VFR. Breezy.
Thursday Night: Mainly VFR, with local MVFR possible. Slight
chance SHRA.
Friday through Friday Night: Mainly VFR, with local MVFR
possible. Breezy. Slight chance SHRA.
Saturday: VFR. Breezy.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short Term /through Tuesday Night/...
Tonight...High confidence.
High pressure will continue to slowly move east of the waters.
However, the pressure gradient will remain weak enough to keep
winds/seas below Small Craft Advisory thresholds.
Tuesday...Moderate to high confidence.
Modest low level jet will result in southwest wind gusts of 20
to 30 knots developing across our southern waters and 3 to 5
foot seas. Will go ahead and hoist small craft headlines. Bands
of heavy showers and isolated thunderstorms are expected with
the remnants of Florence. Fog patches are possible too...both
which may reduce vsbys for mariners at times.
Tuesday night...Moderate to high confidence.
Departing remnants of Florence and high pressure over the
Canadian Maritimes will result in winds shifting to the NNE with
gusts between 20 to 30 knots. Small craft headlines will be
continued for many waters. Seas will also build across our
eastern waters with a better fetch.
Outlook /Wednesday through Saturday/...
Wednesday: Moderate risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of rough seas. Slight chance of rain
showers, patchy fog.
Wednesday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of rough seas.
Thursday: Winds less than 25 kt. Local rough seas.
Thursday Night: Winds less than 25 kt. Seas up to 5 ft. Slight
chance of rain showers.
Friday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Areas of rough seas. Slight chance of rain showers.
Friday Night: Moderate risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of rough seas. Slight chance of rain
showers, isolated thunderstorms.
Saturday: Winds less than 25 kt. Areas of seas approaching
5 ft. Slight chance of rain showers.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Flash Flood Watch from 5 AM EDT Tuesday through late Tuesday
night for CTZ002>004.
MA...Flash Flood Watch from 5 AM EDT Tuesday through late Tuesday
night for MAZ002>019-026.
RI...Flash Flood Watch from 5 AM EDT Tuesday through late Tuesday
night for RIZ001>004.
MARINE...Small Craft Advisory from 8 AM Tuesday to 8 AM EDT Wednesday
for ANZ231>235-237-254>256.
Small Craft Advisory from noon Tuesday to 8 AM EDT Wednesday
for ANZ250.
&&
$$
SYNOPSIS...Belk/BW
NEAR TERM...KJC
SHORT TERM...BW
LONG TERM...Belk
AVIATION...Belk/BW
MARINE...Belk/BW
Area Forecast Discussion
National Weather Service State College PA
1133 PM EDT Mon Sep 17 2018
.SYNOPSIS...
The remnants of Tropical Depression Florence will move through
the region overnight and early Tuesday. Dry weather is expected
Wednesday into Thursday before the next opportunity for rain
arrives late week.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
The shield of steady rain extends from just north of Pittsburgh
up into the Poconos. The rain over southern areas is more
disorganized and showery, but with locally heavy downpours
embedded.
Rap shows some marginal instability poking up into southern PA,
with some moderate shear over SERN zones. The low CAPE/high
shear environment could support a rotating storm if an updraft
can become robust, but the chances will tend to dwindle as we
get deeper into the evening.
The HRRR shows the scattered showers continuing to move across
in waves for much of the overnight. Each new run places a
locally heavy max-bullseye anywhere from the Northern Mountains
to the lower Susq Valley, so the best that can be said is some
of the showers could be locally heavy.
The main threat remains flooding, given combination of
saturated conditions and high streamflows with moderate to
locally heavy rain. We have dropped the Flood Watch over western
areas, deciding to keep it up in areas that have seen the
heaviest rains over recent weeks.
The increased forward speed of Florence should help cap
rainfall totals outside of well trained/persistent heavy
downpours. Blended multi-model mean QPF amounts are still
between 1-2", though given the impressive deep layer moisture
parameters, localized amounts of 3+ inches are possible. HREF
shifts heaviest rain toward northeast PA into early Tuesday
morning.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
Expect generally improving conditions from northwest to
southeast on Tuesday. HREF shows the best chance of sct
showers/tstms over the far southeast zones during the early-mid
afternoon timeframe with bulk of activity likely to develop
along the I-95 corridor. More sun should push max temperatures
into the mid to upper 70s in most locations.
&&
.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
An upper lvl ridge will build across the region after Tuesday.
This will bring several much needed dry and sunny days to the
area. Wednesday into Thursday will be dry, along with much of
Friday. I did up temperatures and dewpoints for this period,
given brisk southwest flow by Friday. We have not seen much
southwest or west flow this summer, just easterly flow much
of the season.
A cold front moves southeastward into the area late Friday.
After some showers and storms late Friday, the first part of
the weekend looks to be dry.
Still have a chance of showers in on Sunday into early Monday,
as the warm air returns, before the next cold front.
&&
.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
Showers continue to move through the region with widespread MVFR
and periods of IFR due to the convection with heavy rain. IFR
ceilings will form overnight due to plenty of low level
moisture. The IFR ceilings and visibilities will overspread the
region overnight once the rain becomes more scattered.
Conditions will slowly improve late tomorrow morning as high
pressure will build into the region Wednesday and Thursday. MVFR
ceiling reductions will be likely Tue night over the
western/northern higher terrain as flow turns to the NW, but
otherwise conditions midweek will be mainly VFR.
.Outlook...
Tue...Widespread reductions in rain early, then improving
conditions.
Wed-Thu...Overnight cig reductions north/west. Morning fog
poss. Otherwise no sig wx.
Fri...Fair early. SHRA/TSRA aftn/eve. CFROPA late.
&&
.HYDROLOGY...
The latest guidance from OHRFC and MARFC keep all river points
below flood stage. Several points are forecast to exceed action
or caution levels. Will need to monitor rainfall very closely
with streams running very high.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through Tuesday morning for PAZ028-037-041-
042-046-049>053-056>059-063>066.
&&
$$
SYNOPSIS...La Corte/Steinbugl
NEAR TERM...La Corte/Steinbugl
SHORT TERM...Steinbugl
LONG TERM...Martin
AVIATION...Ceru/Tyburski
HYDROLOGY...
Area Forecast Discussion
National Weather Service Green Bay WI
923 PM CDT Mon Sep 17 2018
Updated aviation portion for 06Z TAF issuance
and new information added to update section
.UPDATE...
Issued at 907 PM CDT Mon Sep 17 2018
The behavior of the convection this evening has been a bit
perplexing. The initial development along/near the front with
downburst potential fit expectations well, though it was more
intense than initially expected. The continued regeneration back
over the frontal boundary and well north of the combined outflows
is harder to explain. Low-level flow is veering with the passage
of the front so there isn`t a LLJ feeding it. There is some QG
forcing pulling through the area, though that is not particularly
strong.
In any case, the heaviest rains have fallen on the east side of
the City of Green Bay thus far. Much of that area is in a lull
now. Additional development over northwest Brown County and
Shawano County may need to shift through before things settle
down, though the latest radar trends suggest a more easterly
movement with that cluster of storms. The FFW will certainly need
to run through it`s schedule expiration. Although the rains
should be waning by then, will need to see how bad the water
problems are and make a decision on a possible extension as we
approach the expiration time for the warning.
&&
.SHORT TERM...Tonight and Tuesday
Issued at 304 PM CDT Mon Sep 17 2018
Another very warm day across much of the region with temperatures
in the 80s to lower 90s. Cooler air was now working into northern
Vilas County where temperatures were in the lower to middle 80s.
For tonight, the cold front will continue to sag southward with
gusty north/northeast winds just behind it as well as low clouds
which lag several hours behind the front. Main concern for tonight
will be the chances of thunderstorms. First cluster of storms
was across eastern Minnesota and was now moving into far western
Wisconsin. Latest HRRR model indicated this cluster would work
into western Wisconsin and then dissipate by the time it got
to Wausau. Latest mesoanalysis indicated mixed layer capes 500
to 1000 J/KG across central Wisconsin. Would expect cluster of
storms to move a little further east than the HRRR was suggesting
before dissipating. Behind the first cluster of storms, more
showers and storms are expected to develop west of the area
and the move into the region late this evening, if not overnight
and continue into Tuesday morning. There is expected to be a break
in the rain later tomorrow morning into tomorrow afternoon before
more rain returns Tuesday night. High temperatures on Tuesday
should be some 15 to 20 degrees cooler than today.
.LONG TERM...Tuesday Night Through Monday
Issued at 304 PM CDT Mon Sep 17 2018
Transition to cooler and more unsettled weather expected through
much of the upcoming work week as a front meanders through the CWA.
The greatest potential for heavier rainfall and stronger storms will
be Wednesday into Wednesday night and especially on Thursday.
Tuesday night through Thursday night: Zonal flow and the outer edges
of a weak surface ridge will remain in place through Tuesday
evening; however, a warm front is expected to lift north as it
initially stretches from around the NE/SD border eastward to
southern WI/northern IL. This will be ahead of a low pressure system
that is expected to eject/deepen across Colorado. Ahead of the low
and along the warm front, moisture and warm air advection will
increase from the south late Tuesday night.
The warm front is expected to lift through the CWA late Wednesday
afternoon into Wednesday night. This will be the main focus for
precipitation through Thursday afternoon. Indications are that a LLJ
will develop ahead of the deepening low. This would help to increase
moisture flow and forcing over the warm front, which would lead to
the potential for heavier rainfall. Current thinking is that a
widespread 1 to 2 inches of rainfall across much of CWA Wednesday
night through Thursday night. PWAT values are progged to be around 1
- 2 inches for this time period, which is around 150% to 200% of
normal for this time of year. The low pressure center is progged to
slide over north-central WI Thursday afternoon into Thursday evening
based on the GEM/GFS/EC; however, the NAM is farther southeast with
the low track. If the northwestern solutions pan out, this would
lead to the potential for some strong to severe thunderstorms late
Thursday afternoon into Thursday evening. The northwest third of the
CWA would likely remain on the cooler side of the low with any of
the solutions, helping to lower the severe potential, while the rest
of the CWA may be in the warmer/more moist (dewpoints possibly in
the low 70s) sector to the southeast of the low and ahead of the
cold front. Instability may increase, possibly up to 1000-2000 J/kg
ahead of the front along with deep-layer shear values in the 45 to
55 kt range. Shear vectors also look to be perpendicular to the cold
front favoring a more organized severe event. Again, this is a
possibility, but there is still some disagreement among the models
at this point in overall cloud cover and the exact track of the low.
In fact, if the NAM solution verifies, then it would keep most of
the CWA on the cooler side of the low, still rainy, but a lower risk
of severe storms. Will definitely be a system to watch Thursday
afternoon into Thursday evening. At this point decided to highlight
in the potential in the HWO.
Rest of the extended: Friday morning, the cold front will be to the
east and southeast of the area as dry high pressure builds in,
allowing for more tranquil and cooler conditions. This will be the
case into the upcoming weekend as zonal flow remains in place and
only minor disturbances push through the area. Consensus worked well
for this time period.
&&
.AVIATION...for 06Z TAF Issuance
Issued at 907 PM CDT Mon Sep 17 2018
Thunderstorms over east-central Wisconsin should end, but
lingering moisture will increase the potential for low clouds
later tonight into tomorrow morning.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE.........Skowronski
SHORT TERM.....Eckberg
LONG TERM......Cooley
AVIATION.......Skowronski
Area Forecast Discussion
National Weather Service Grand Rapids MI
908 PM EDT Mon Sep 17 2018
LATEST UPDATE...
Update
.SYNOPSIS...
Issued at 157 PM EDT Mon Sep 17 2018
A cold front will slip down from the north later tonight into
Wednesday. A local shower or thunderstorm could form but it will
be dry for most of the time. A more organized area of low pressure
tracks through the region Thursday into Friday leading to perhaps
several rounds of showers and thunderstorms.
&&
.UPDATE...
Issued at 910 PM EDT Mon Sep 17 2018
I have increased the threat of showers and thunderstorms
overnight, mostly over western sections. There is an MCV over
Wisconsin heading east southeast just behind the cold front. The
Hi-Res models are not doing all that great in picking up on the
convection near GRB (9 pm). The HRRR does show a band of increased
precipitable water near the front and it has an assoicated area
of enhanced moisture transport along the front. It would seem to
me we have at least a chance of seeing showers and a few
thunderstorms. The model sounding at MKG and GRR show very little
negative area and around 1600 j/kg of most unstable cape between
midnight and 10 am. Now there is some dry air (20% rh) between 850
mb and 500 mb so it may be hard to overcome that but on the other
hand the MCV is there and does not seem to weakening all that
fast. Bottom line putting a chance of showers and thunderstorms
overnight seems like a reasonable idea.
&&
.SHORT TERM...(This evening through Wednesday night)
Issued at 157 PM EDT Mon Sep 17 2018
A weakening cold front slips down from the north later tonight and
dissipates near or just south of the region on Tuesday. Forcing
remains weak with this feature but moisture does increase. A few
pop up showers or perhaps a thunderstorm could be around. While
the change of airmass is not that significant behind the front in
the mid levels...the temperature does drop off considerably at
around 900 mb. Forecast soundings do show this wedge of colder air
down low. The main impact of this would be lower daytime
temperatures and perhaps low clouds.
A digging mid level wave pushes into the NW U.S. Wednesday into
Wednesday night. This results in a strengthening southwesterly
low level jet. Elevated instability arrives here in MI along the
strengthening warm frontal zone. This should result in a increased
potential for showers and thunderstorms. We will feature
relatively high POPs.
.LONG TERM...(Thursday through Monday)
Issued at 157 PM EDT Mon Sep 17 2018
This mid wave takes on a negative tilt as it enters the Upper
Plains. The combination of stronger dynamics...favorable moisture
and stronger instability does increase the potential for severe
weather. It looks like the warm front lifts just north of the CWA
on Thursday...with much of the CWA in the warm sector. This would
support breezy and warm conditions. Deep layer and low level shear
become impressive and any storm that does form would have the
potential for impacts. The cold front does not push through until
late Thursday night or Friday morning...so timing is somewhat of a
limiting factor. Models are in relative agreement on this
scenario. Will keep the POPs high and continue to mention the
risks in our products.
A mid level zonal flow sets up for the weekend. Embedded within
this flow is a weak wave. Also a southern stream wave will be
lifting northeastward out of the Southwest U.S. Models are
struggling somewhat with this scenario...so confidence is somewhat
lower than normal. If these two features link up over the region
it could be a wet weekend. For now high pressure will be around
to start the weekend...so we will feature a dry start. Then with
the passage of these waves...we will have a risk for some rain.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 739 PM EDT Mon Sep 17 2018
I expect solid VFR conditions through at least midnight. Some fog
is possible in the I-69 TAF sites early Tuesday morning ahead of
the cold front. I expect the area of convection over MN and WI
head toward SW MI after midnight but it seems to me it will have a
hard time reaching our TAF sites due to much dry air to overcome.
Even so it is a decent cold front so I have VCSH for the western
TAF sites (not LAN or JXN) since whatever showers do manage to
make it on shore, they should be gone before they get that far
inland. There may be a area of low clouds behind the front that I
did not include in the TAF at this point since my confidence for
that was to low but I did want to mention it.
&&
.MARINE...
Issued at 157 PM EDT Mon Sep 17 2018
The winds and waves will increase around the frontal zone tonight
into Tuesday. Overall conditions are forecasted to become
marginally hazardous for small craft up near Little and Big Sable
Points. A much greater chance for hazardous boating conditions
exists for Thursday into Friday as a deepening area of low
pressure moves through.
&&
.HYDROLOGY...
Issued at 157 PM EDT Mon Sep 17 2018
River levels remain steady or continue to slowly fall following more
than a week of dry weather. Rain chances through Tuesday night will
be confined to isolated showers and thunderstorms. These will not
affect a large area, and are unlikely to produce rises in river
levels.
A better chance for showers and thunderstorms exists Wednesday
through early Friday as low pressure tracks through the region. Rain
amounts will be highly variable due to a weather pattern that favors
convection over a more steady type of rain. At this time, it looks
as if areas north of I-96 stand the best chance of rain with each
round. Rain will be heavy at times, exceeding rainfall rates of more
than an inch per hour. This could lead to ponding of water on roads
and low lying areas. We could also see rises in smaller creeks and
streams.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&
$$
UPDATE...WDM
SYNOPSIS...MJS
SHORT TERM...MJS
LONG TERM...MJS
AVIATION...WDM
HYDROLOGY...HLO
MARINE...MJS
Area Forecast Discussion
National Weather Service Tucson AZ
340 PM MST Mon Sep 17 2018
.SYNOPSIS...Scattered showers and thunderstorms mainly east to south
of Tucson Tuesday afternoon and evening. A good chance of showers
and thunderstorms exists Wednesday into Thursday as deep moisture
moves across the area. Showers and thunderstorms decreasing in
coverage Friday, then a slight chance of thunderstorms continues
east of Tucson this weekend. Much cooler temperatures will occur
Wednesday into Thursday followed by a warming trend this weekend.
&&
.DISCUSSION...Isolated showers occurring at this time mainly from
near the Tucson metro area southward into Santa Cruz County. Only a
few gauges have recorded measurable amounts - mostly a few
hundredths of an inch in Redington Pass northeast of Tucson and just
north of Nogales. A gauge on the Catalina Mountains recorded about
0.20 inch of rainfall during the past three hours. Several HRRR
solutions suggest that showers and a few thunderstorms will end
around or shortly after sunset this evening.
Strong high pressure aloft on Tuesday will become centered over the
southern CONUS Plains as an upper trough approaches the California
coast. Meanwhile, an inverted trough will continue south of this
forecast area. In addition, a tropical disturbance will also reside
about 250 miles south of the southern tip of Baja California.
Various 17/12Z numerical weather models were similar to previous
solutions with depicting a markedly wetter period will occur across
this forecast area, especially Wednesday into Thursday. Expect
isolated to scattered showers and thunderstorms to occur Tuesday
afternoon and evening mainly east to south of Tucson. These solutions
suggest that showers and thunderstorms will increase in coverage
late Tuesday night in response to a deepening southerly flow regime.
Based on the 17/12Z solutions, PoPs were increased about 10-20
percent or so Wednesday into Wednesday night versus the inherited
forecast, and only minor PoP adjustments were made Thursday. Thus,
scattered to numerous showers and thunderstorms are forecast to
occur Wednesday into Thursday as deep subtropical moisture moves
northward across the area. A quick glance at the 17/18Z GFS suggests
that coverage of showers/tstms on Thursday would decrease
markedly especially north of Tucson, but this solution is in
contract to the more widespread coverage depicted via the 17/12Z
GFS/ECMWF.
The models depict a gradual shift toward a more westerly flow aloft
regime starting Friday and continuing into the weekend. However, the
17/18Z GFS departs from this scenario and maintains a more sly 700-
500 mb flow into the weekend. At any rate, the official forecast
Friday continues with scattered showers/tstms especially from Tucson
eastward/southward, then a slight chance of showers/tstms Saturday
mainly east of Tucson. Any showers/tstms Sunday into Monday should
be confined to locales near the New Mexico state line.
Although high temps Tuesday may be a few degrees lower versus this
afternoon, temps will remain several degrees above normal. Markedly
cooler temps will then occur Wednesday given the increased moisture/
rain chances. A gradual warming trend is forecast at this time to
prevail by Friday and continue into early next week.
&&
.AVIATION...Valid through 19/00Z.
A few showers and storms have developed on the mountains east of
Tucson as well as near the US/Mex border. Could see a stray shower
move through OLS through early evening, otherwise expect FEW-SCT
clouds mostly around 8k-12k ft AGL at all sites. Lingering cloud
cover is expected area-wide overnight into Tuesday morning, then
isolated to scattered -TSRA/-SHRA mainly east to south of KTUS
Tuesday afternoon. Outside of thunderstorm induced winds, expect
typical diurnal directions and speeds through Tuesday afternoon.
Aviation discussion not updated for TAF amendments.
&&
.FIRE WEATHER...Isolated to scattered thunderstorms mainly east to
south of Tucson Tuesday afternoon and evening. A good chance of
showers and thunderstorms will prevail late Tuesday night into
Friday. A drying trend will then occur this weekend, but enough
moisture for a slight chance of thunderstorms mainly near the New
Mexico state line. 20-foot winds will be terrain driven mainly less
than 15 mph. However, gusty and erratic winds may occur at times due
to thunderstorms.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...None.
&&
$$
DISCUSSION...Francis
AVIATION...Leins
FIRE WEATHER...Leins
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