Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/19/19

Northern Alaska Forecast Discussion

National Weather Service Fairbanks AK

 324 PM AKDT Sun Aug 18 2019

.DISCUSSION...
Our main forecast concern in the short term will be high water on
rivers in the Interior. While the heavy rainfall ended Friday
night, it will take a few days for all of the water to work its
way through the system.

The operational models are all in relatively good agreement out
through Tuesday. Thereafter, they begin to diverge on the
synoptic scale pattern. The ECMWF and the NAM both want to drop a
500 mb low south from the Brooks Range into the Interior on
Wednesday, while the GFS wants to keep it over the Brooks Range.
We will lean more with the NAM/ECMWF solution as it seems to be
more consistent from run to run.

Interior: Recent heavy rains have left many rivers across the
Interior high. There is ongoing flood products out for parts of
the Chena, Salcha, Tanana and Nenana Rivers. This will be
described in more detail in the hydrology section below.
Relatively clear skies tonight will allow for temperatures to
drop into the 30s tonight with a few places dropping down into
upper 20s. For Fairbanks, we expect that the temperatures will
remain in the upper 30s in town; however, it is not out of the
question that some of the lower elevation locations on the
outskirts of Fairbanks will see a frost overnight. Shortwaves
around an upper low over the eastern Brooks Range will bring
chances for showers to areas along the Canadian Border during the
day on Monday. The HRRR actually has the showers as far west as
Fairbanks. We opted to give this a little bit of play by extending
the isolated PoPs into Fairbanks. Chances for showers for Tuesday
and Wednesday; however, the exact placement and amount of
precipitation expected still remains a little bit fuzzy. The fine
scale details with this will depend on the placement of the upper
low. The ECMWF has the low diving to the ECMWF has the low diving
to the south Tuesday night, bringing around a quarter of an inch
of rainfall to the Interior, mainly along a line from Coldfoot to
Fairbanks to Denali National Park, the Nam doesn`t bring the low
as far to the south and keeps bulk heaviest precipitation east of
Fairbanks, mainly over the Fortymile Country. The GFS doesn`t
really move the low that far south and keeps most of the
precipitation along the Canadian Border. We kept out PoPS chance
over the area at the moment until we can get some better agreement
with the models.

North Slope and Brooks Range: We will likely see some fog and low
stratus overnight tonight. An upper low will move west to be
situated over the eastern Brooks Range by Tuesday afternoon. This
low will bring precipitation to the eastern Arctic Coast and the
eastern Brooks Range late Tuesday into early Wednesday. Along the
coast this we expect that this precipitation will be in the form
of rain. In the Brooks range, we expect snow for areas above 2,000
feet in elevation. This system has the potential to bring a
couple of inches of snow. The models aren`t in the best of
agreement on how this low will progress on Wednesday. The GFS
keeps the low in place over the eastern Brooks Range longer than
the ECMWF or the NAM. The GFS solution would result in higher
snowfall totals over the Brooks range given the more persistent
upslope flow on the north side of the range. We are leaning more
to the NAM/ECMWF solution that moves the low and the associated
precipitation south into the Interior much quicker.

West Coast: A shortwave will dive south over the west coast on
Monday this will bring rainfall to the Seward Peninsula (including
Nome) during the Morning hours on Monday and to the Yukon Delta
in the afternoon. After this precipitation passes through the
area we aren`t expecting any precipitation for the remainder of
the week.

Coastal Hazard Potential Days 3 and 4...None.

&&

.FIRE WEATHER...
No big concerns for the upcoming week. A cool and mainly dry
pattern will persist into Monday. Minimum RH values are expected
to remain above 35 percent across the entire area for Monday. RH
values will increase slightly for Tuesday.

&&

.HYDROLOGY...
Rainfall between Thursday and Saturday was over 1 inch in the
area south of Circle to Tanana (excluding the Fortymile Basin
which was drier), with 2 inches over most of the area south of
Wonder Lake to Fairbanks to the Gerstle River, and 3 to 4 inches
along the Alaska Range between the Delta Junction and Denali, with
the Eielson Visitor Center come in at 4 inches. Most of this rain
fell in a 24 hours period between early Fri morning and Saturday
morning. Most of the water has moved out of streams and into
larger rivers. The Nenana River has a flood advisory, with minor
flooding occuring in the city of Nenana, and that flooding is
expected to continue for several more days. The Tanana River has a
flood advisory from Shaw Creek all the way to the city of Tanana
with flooding in low lying areas along the Tanana River, which
will last for several more days.

The Little Chena and Goodpaster Rivers crested Sat below bankfull
and the threat of flooding is over on both of those rivers. The
Upper Chena River crested Saturday at minor flood stage, and the
Chena River near Hunts Creek is expected to crest today near minor
flood stage, with the Chena in Fairbanks cresting on Monday
below bankfull. The Salcha River will crest today over a foot
above flood stage, which is the highest water level on the Salcha
River since 2014.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory for PKZ245.
&&

$$

AUG 19



Area Forecast Discussion

National Weather Service La Crosse WI

 639 PM CDT Sun Aug 18 2019

.SHORT TERM...(This evening through Monday)
Issued at 258 PM CDT Sun Aug 18 2019

A much quieter short term period today, though plenty of cloud cover
was seen as a cold front was still making its way through the
forecast area and occasionally producing light showers and some
drizzle. Farther northwest and behind the front, high pressure was
leading to mostly sunny skies. Clouds will continue to scatter out
through the afternoon from northwest to southeast, with the entire
area becoming mostly clear just after sunset. This sets the stage
for potential fog development, especially in the river valleys.
Trends in RAP model soundings have been toward a deeper light wind
layer near the surface, which would be favorable for more fog.
However, light northerly winds on the east side of surface high
pressure will continue to bring in drier air which could hinder
development. Overall, still think there will be at least some patchy
fog around.

Quiet weather will remain in place for Monday with zonal flow aloft
and surface high pressure remaining in control just east of the
forecast area. Light southerly winds will start to bring some
slightly warmer and more humid air to the area, with highs
generally in the upper 70s to mid 80s.

.LONG TERM...(Monday night through Sunday)
Issued at 258 PM CDT Sun Aug 18 2019

Monday Night through Tuesday night...High pressure shifts east
Monday night and return flow begins the moisture advection
through IA/MN. A rich, high dewpoint airmass is poised just south
of I-80 Monday and this will rapidly invade on Tuesday. A number
of ingredients are in play for Tuesday, but the orchestration of
those ingredients still seems tough to discern. A well-defined
shortwave trough over northern CA at 19Z today, per GOES water
vapor imagery, will begin tracking for the area and arrive Tuesday
morning. It seems to have enough depth to elicit height falls and
a low-level moisture transport ramp-up and isentropic lift region
from the west Tuesday morning. Good consensus exists Monday in
the High Plains on these features, but the strength and location
vary quite a bit by 12Z Tuesday. Some solutions, however, are
suggesting forcing for rain chances in southeast MN and northeast
IA Tuesday morning. A cold front in the northwest flow will also
push in, during the afternoon or evening depending on the model
chosen, providing another lift source into a developing CAPE pool
in the 2000-30002k J/Kg range. Capping is in play however, and
moderately strong south of I-90. This may favor areas north of
I-90 more for TSRA Tuesday afternoon/evening. Convergence along
the front is weak-moderate, not helping TSRA development in a
capped environment. The 18.12Z NAM 4km Nest at 60hours does have
some TSRA development entering sern MN Tuesday eve for what it is
worth.

So, continued storm chances Tuesday and Tuesday evening, but
confidence is low on the outcome. The mid-level wind max of 45-50
kts is more coincident over the front, per 18.12Z NAM/GFS vs.
yesterdays model guidance, suggesting a tick up on severe storm
chances. Hodographs would suggest a straight-line supercell shear
profile favoring hail/wind. Bottom line: too much spread in the
forcing, timing, and cap to change risk message at this time. /DB

Thursday through Sunday...Towards the weekend, warmer air returns
as the high pressure moves off to the east. Although relatively
low (<30%), precipitation chances also return with the flow
becoming more out of the southwest. /MA

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 639 PM CDT Sun Aug 18 2019

There is the potential for valley fog at KLSE tonight after 10Z
with VLIFR conditions possible. Currently the temperature/dew
point spread is sitting at 20 degrees and KLSE stays in a light
wind gradient through much of the night. Given these two factors,
have held off on including VLIFR conditions in the TAF and
maintained BCFG for dense fog in the area. Will continue to
monitor winds and temperature/dew point spread closely this
evening for a possible update. Otherwise, after the valley fog
dissipates Monday morning, expect VFR conditions with high
pressure in control.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&

$$

SHORT TERM...CA
LONG TERM...Baumgardt/Aufforth
AVIATION...Wetenkamp




Area Forecast Discussion

National Weather Service Bismarck ND

 1010 PM CDT Sun Aug 18 2019

.UPDATE...
Issued at 1009 PM CDT Sun Aug 18 2019

Some clouds continue to pass over the far north late this evening.
These clouds will continue to move off to the east overnight.
Otherwise, quiet weather continues.

UPDATE Issued at 628 PM CDT Sun Aug 18 2019

Quiet weather continues. With the exception of increasing cloud
cover a little bit over the west, remainder of forecast remains in
good shape.

&&

.SHORT TERM...(This evening through Monday evening)
Issued at 127 PM CDT Sun Aug 18 2019

Quiet and warmer in the short term period.

Mostly clear and quiet tonight. A southerly low level flow
develops as a shortwave approaches from the west. Temperatures
will be warmer than last night with lows in the upper 40s to mid
50s.

Mostly sunny and warmer on Monday. A midlevel shortwave and
associated surface trough is expected to track into western North
Dakota by the late afternoon hours. Moist southerly return flow
in the prefrontal region will bring surface dew points into the
low to mid 60s over south central ND, to mid 50s north central.
Steep midlevel lapse rates, 1500-3000 J/kg of MLCAPE is expected
along and east of the front. Thunderstorms will be possible Monday
evening as the surface trough deepens under the approaching upper
level wave.

There`s a little more certainty in precipitation placement with
global models and CAMS that go out through tomorrow evening
generally showing two favored areas of convection. One along the
International Border, closer the the large scale ascent, and
another over southwest/south central ND within the area of
greatest instability and convergence along the surface boundary.

Uncertainty does remain in thunderstorm coverage. Instability has
increased from previous model runs with shear about the same
(around 40kts Bulk Shear) but coverage remains limited. The ECMWF
seems the most robust, developing convection earlier over
southwest ND late afternoon and spreading it into the southern
JRV By evening. And another area of convection near and to the
east of the Turtle Mountains during the evening. The GFS
indicates very little qpf in the evening over western and central
ND with best coverage after midnight far north central and mostly
east of the forecast area. The NAM is basically dry across the
entire forecast area. CAMS that develop convection over the
southwest and south central Monday evening, are quick to suppress
the convection as it propagates east.

All in all with around 40 kts of 0-6 km bulk shear oriented
orthogonal to the initiating boundary and the anticipated
instability, discrete supercell thunderstorms will be possible
with a large hail and damaging wind threat. A nonzero tornado
threat may also be possible with guidance indicating around 15 kts
of 0-1 km shear and some curvature in the lower portions of
forecast hodographs over the southwest, south central. Even with
two favored areas we opted for a blanket slight chance pop Monday
evening at this time as we can not rule out convection anywhere
along the boundary and coverage from all guidance remains
isolated.

With western North Dakota west of the surface trough late Monday
afternoon, breezy westerly winds and temperatures around 90 are
expected. On the eastern side, breezy southerly winds and highs in
the 80s are forecast. NBM guidance was a tad lower than the
previous forecast so we stuck with the previous forecast highs for
Monday. We did blend some of the latest HRRR dewpoint guidance
with Official to better indicate the expected mixing out and
drying behind the front in the far west Monday afternoon.

.LONG TERM...(Monday night through Sunday)
Issued at 127 PM CDT Sun Aug 18 2019

Convection is expected to be exiting the eastern CWA around or
shortly after midnight. There will be a period of gusty winds
behind the cold front late Monday and Tuesday morning with
generally subsiding winds by Tuesday afternoon as surface high
pressure builds over the area. We utilized a blend of Official and
CONSMOS Monday night into Tuesday for winds. Cooler with highs in
the 70s on Tuesday.

Chances for convection return beginning Thursday afternoon as an
upper ridge breaks down into a quasi-zonal pattern and a trough
approaches from the west. The envelope of model solutions widens
as we head into next weekend, but expect periodic chances for
convection through the weekend.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 628 PM CDT Sun Aug 18 2019

VFR conditions will prevail through the forecast period.


&&

.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...JJS
SHORT TERM...TWH
LONG TERM...TWH
AVIATION...JJS



Area Forecast Discussion

National Weather Service Detroit/Pontiac MI

 653 PM EDT Sun Aug 18 2019

.AVIATION...

Line of convection has developed along the near surface trough axis
upstream. These storms will affect the Detroit regional terminals
and Flint in the first couple hours of the forecast. Winds will snap
around to the west in the wake of the front for a few hours before
relaxing back to southwest overnight. Enough moisture will remain
locked into the boundary layer to support nocturnal fog and low cloud
development. A cold front will slide south through the region Monday
morning - flipping winds to light northerly during the morning
hours. Post-frontal clouds are expected across the southern
terminals but should remain VFR.

For DTW...line of thunderstorms should begin to affect the western
areas of the DTW airspace after 00z with the main window of
affecting the terminal in the 01z-02z window. Light fog and low
cloud development is expected after midnight. Lingering ceilings
below 5kft are likely Monday.

.DTW THRESHOLD PROBABILITIES...

* Moderate for ceilings aob 5kft tonight and Monday.

* High for thunderstorms 01-02Z.

&&

.PREV DISCUSSION...
Issued at 319 PM EDT Sun Aug 18 2019

DISCUSSION...

The numerous showers and thunderstorms which worked through
southeast Michigan this afternoon (a few severe), helped drop
temperatures into the 70s, leading to a significant stabilization of
the airmass (see 19z SPC mesoscale analysis). Thus, confidence is
low that activity with the actual cold front will be severe, not to
mention the coverage of activity is in question this far north. At
least, the 17z Rap looks to be trending in the right direction (less
activity). None-the-less, still a short window to destabilize (lower
80s) before sunset, and the upper level dynamics/shear (50 knots of
effective shear) needs to be respected as it sweeps through around
00z. On the flip side, could be in the shadow of the organizing
thunderstorm complex developing over central Indiana into Ohio where
the max instability (MLcapes of 2500 J/kg) presently resides, which
should help mitigate our severe chances as well.

Strong upper level low (545 DAM at 500 MB) over northern Manitoba
will be the main influence/director to our weather over the several
day, as it swings through Ontario during the mid week period,
supporting a significant cool down.

An extension of trough axis will be lifting through the northern
Great Lakes tonight, with 500 MB heights beginning to rebound over
southern Lower Michigan on Monday. Thus, the cold front that slips
through southeast Michigan tonight, will more or less wash out. With
the lingering low level moisture, especially with the rainfall from
this afternoon, and weak surface convergence, some fog and/or low
stratus development appears possible late tonight.

500 MB heights rise to around 588 DAM on Monday, but still enough
residual low level moisture/850 MB Theta-e and instability around to
support low chance pops along/south of I-94.

Pseudo zonal upper level flow with upper level energy/PV coming out
of the Rockies and tracking through Midwest Monday night. It appears
the potential thunderstorm complex will track off to the southeast
during Tuesday and miss the state. This will also help cut off some
of the moisture advection ahead of the cold front, which tracks
through late Tuesday night or Wednesday. Thus, a dry frontal passage
remains possible.

Warmer temperatures, with highs in the 80s, will remain in place on
Wednesday before cooler temps come back for the remainder of the
week.  By Thursday, 850mb temps will be back in the single digits. A
slight chance of precipitation also remains in the forecast
Wednesday afternoon, as a wave passes over.  The rest of the
forecast period going into the weekend will feature pleasant
temperatures and dry weather as high pressure settles in over the
region.

MARINE...

A low pressure system lifting through lake Superior this afternoon
will pull a cold front through the region this evening. This front
may produce another round of thunderstorms this evening before
pushing east of the area. Southwesterly winds will veer westerly
behind this front tonight and to the northwest on Monday as a
secondary front drops through the region. Winds will be strongest
this evening out of the southwest with gusts reaching 25 knots.
Though cooler air will advect in behind the front tonight, high
pressure building in will weaken the gradient and prevent stronger
gusts tonight and Monday. Though mostly a dry forecast beyond
tonight, additional showers and thunderstorms will continue to be
possible over Lake Erie and St. Clair with the frontal boundary
stalling nearby.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Small Craft Advisory until 4 AM EDT Monday for LHZ421-422.

Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&

$$

AVIATION.....Mann
DISCUSSION...SF/SP
MARINE.......DRK


You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.




Area Forecast Discussion

National Weather Service Quad Cities IA IL

 1104 PM CDT Sun Aug 18 2019

...AVIATION UPDATE...

.SYNOPSIS...
Issued at 310 PM CDT Sun Aug 18 2019

18Z surface data had the cold front from KLSE to KOMA with a pre-
frontal trof from northeast Illinois back through KOTM. Dew points
were in the 70s from Ohio Valley into the southern Plains and deep
South. Behind the front dew points were in the 50s and 60s.

&&

.SHORT TERM...(This Evening through Monday)
ISSUED AT 310 PM CDT Sun Aug 18 2019

Cloud cover has resulted in a slow recovery of the atmosphere today.
Satellite trends show very weak diurnal cumulus clouds developing
along the front in central Iowa. So the question is will any diurnal
convection develop along the front late this afternoon and overnight.

RAP has shown convergence in the frontal zone as it moves into the
area late this afternoon and evening with unstable air aloft.
However the trends with the convergence has been to slowly weaken
with each new run.

If convection develops late this afternoon it would be confined to
the immediate frontal zone and likely isolated in nature. There may
be a small area where areal coverage becomes scattered.

Thus will go with isolated showers and storms developing late this
afternoon and persisting through the evening as the front moves
through the area. After midnight any convection that develops will
slowly dissipate through sunrise.

On Monday there may or may not be a few lingering showers in the far
southeast and east areas around sunrise. If there are showers they
will end by mid-morning. The rest of the day will be warm and humid
as skies slowly clear. Heat index readings of 90 to 95 are possible
south of an Ottumwa, IA to Galesburg, IL line.

.LONG TERM...(Monday Night through Sunday)
ISSUED AT 310 PM CDT Sun Aug 18 2019

Models are in good overall agreement through the long term period.
The main forecast concerns are temperatures on Tuesday and chances
of precipitation through the period.

The long term period opens with northwesterly flow aloft as closed
area of high pressure expands eastward across Texas and Oklahoma and
into western Missouri and Arkansas.  Tuesday looks to be the warmest
day of the period ahead of a cold front that will move across the
region Tuesday afternoon and evening. This will bring the chance of
showers and thunderstorms area during peak heating. There is a
marginal risk of severe thunderstorms across the area on Tuesday.
The timing of the front and potential precipitation calls into
question how warm we could get during the day.  Current highs are in
the mid to upper 80s with dewpoints in the lower to mid 70s could
produce heat indices of 100 to 104 for 3 or 4 hours so there is also
the potential for a heat advisory but that will depend on the timing
of precipitation.

After Tuesday night, a strong upper level low will dig southward out
of eastern Canada and into the northeastern US. This will continue
to bring pieces of shortwave energy across the area every 18 to 24
hours with daily chances of showers and thunderstorms.  There will
be dry periods in the forecast as ridging will follow in the wake of
these shortwave troughs but timing individual features this far in
advance is very difficult. Temperatures will be near normal on
Wednesday but then run slightly below normal Thursday into next
weekend.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday Night)
ISSUED AT 1102 PM CDT Sun Aug 18 2019

Light northeast winds may allow for some fog and MVFR cigs/vis
late tonight into Monday morning, then followed by VFR conds for
most of the day on Monday. North to northeast winds less than 10
knots.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&

$$

SYNOPSIS...08
SHORT TERM...08
LONG TERM...Cousins
AVIATION...Haase




Area Forecast Discussion

National Weather Service Lincoln IL

 844 PM CDT Sun Aug 18 2019

.SYNOPSIS...
Issued at 843 PM CDT Sun Aug 18 2019

Very warm and humid conditions are on tap for the next couple
days, as heat index values return to triple digits by Tuesday.
Scattered thunderstorms are possible again on Monday, primarily in
east central and southeast Illinois. Storm chances will increase
on Tuesday, and a few may be strong to severe.

&&

.UPDATE...
Issued at 843 PM CDT Sun Aug 18 2019

Storm activity has pushed east of the forecast area this evening,
with water vapor imagery showing the upper wave along the Indiana
border. Have largely eliminated much of the PoP`s overnight,
though some isolated showers/storms may still linger across the
eastern CWA. Concern overnight will be more with fog potential,
especially across the northeast CWA where the heavy rains occurred
a few hours ago. Skies have already largely cleared there, though
some narrow bands of stratocumulus linger from near Decatur to
Danville. Latest HRRR/LAMP guidance has been hinting at this for
the last few runs, though varying in the overall coverage. For
now, will only mention the fog from about Decatur eastward.

&&

.SHORT TERM...(This evening through Monday)
ISSUED AT 330 PM CDT Sun Aug 18 2019

A broken line of strong to severe thunderstorms was over far
southeast IL into se MO and ne AR at mid afternoon. These storms
formed along an outflow boundary the was pushing southeast through
southeast IL and strongest storms currently south of CWA in
Edwards and southern Wayne counties. Unstable CAPEs of 2500-3600
j/kg were east of I-57, highest along the Wabash river. A
thunderstorm was over Champaign county from Savoy/CMI airport
south and tracking eastward toward Vermilion county. Surface
analysis shows the main synoptic front extended from 1001 mb low
pressure over eastern Lake Superior thru central WI/IA and into
central KS. Aloft a broad/weak upper level trof was over the
Great Lakes, much of the Midwest and over the northern
Plains/Rockies, while 594 dm 500 mb subtropical ridge was near
the southeast atlantic coast and sprawled back into TX/NM.

Diurnally driven scattered convection in eastern IL should
diminish toward early evening as sunsets, and only carried slight
chances or dry rest of tonight into mid Mon morning over CWA. Lows
overnight in the upper 60s to around 70 degrees. The latest models
show the frontal boundary pushing se into IL river valley around
midnight tonight and into southeast IL near I-70 by 18Z/1 pm Mon.
This boundary to help develop more isolated to scattered
convection by midday Monday and continue into early Mon evening
mainly over areas from I-72 south. Airmass gets unstable again
over areas south of I-72 by Mon afternoon and could see a few more
strong thunderstorms especially in southeast IL. Highs Mon of
85-90F warmest in southeast IL where heat indices reach the upper
90s to near 100 Mon afternoon.

.LONG TERM...(Monday night through Sunday)
ISSUED AT 311 PM CDT Sun Aug 18 2019

Isolated to scattered convection over southern CWA early Mon
evening to diminish after sunset, with another lull expected into
mid Tue morning. A disturbance and possible MCS to affect area by
Tue afternoon and evening bringing next chance of thunderstorms.
SPC has much of area in a slight risk of severe storms Tue
afternoon/evening as very unstable airmass develops with CAPES
rising to 3000-4000 j/kg during Tue afternoon over southern CWA.
Highs in the upper 80s/lower 90s on Tue with afternoon heat
indices in the upper 90s to around 105F, highest in sw CWA where
heat advisory may eventually be needed Tue afternoon.

The main frontal boundary to push sse into nw CWA late Tue night
and thru rest of CWA during the day Wed. This will likely continue
chances of showers and thunderstorms on Wed especially central and
southern CWA. Highs Wed range from lower 80s by Galesburg, to the
upper 80s to near 90F in southeast IL where heat indices peak
around 100F in southeast IL Wed afternoon.

Frontal boundary pushes south of area during Wed night and Thu
while upper level trof over the Great Lakes brings in cooler and
less humid air into central IL. Still have 20-30% chance of
convection over areas south of I-74 Wed night into Thu as Ecmwf
model is keeping qpf over southern half of CWA thru Thu afternoon,
and not as far south with frontal boundary as the GEM and GFS
models which are dry over our CWA overnight Wed night and Thu.
Stayed close to model consensus for convection chances here but
confidence of convection chances is low during Wed night and Thu.
Highs Thu and Fri of 79 to 83 degrees, warmest in southeast IL.
Lows Thu and Fri nights in the upper 50s and lower 60s.

Generally dry conditions expected much of the time from Thu night
thru next Sunday, with weak high pressure over the Great Lakes.
But the subtropical ridge over the sw and southern states and
upper level trof moving into the eastern Great Lakes and New
England puts IL in a WNW upper level flow, and could see some
disturbances tracking ESE and possibly affecting the area, though
timing and placement of these are difficult to project that far
out. Consensus of models has slight chance of convection over much
of CWA on Fri afternoon, Sat and again Sunday afternoon. Highs in
the low to mid 80s next weekend and humidity levels gradually
increase.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 645 PM CDT Sun Aug 18 2019

A broken band of convection was well se of the central IL airports
and will continue to pull away from central IL during this
evening. Clearing wedge pushed into areas from I-55 west early
this evening and will move into DEC and CMI during next hour or
two, but still VFR conditions prevailing there with mainly
scattered to broken mid/high clouds present early this evening. A
frontal boundary over southeast parts of WI/IA and far nw MO has
4-7k ft cloud decks in central and southern IA into far northern
IL with isolated showers in central IA. This front to move toward
the IL river valley late tonight and be over central IL much of
Monday. This should increase clouds during overnight with ceilings
of 3-6k ft possible and some fog to develop especially by CMI
which had half inch rain this afternoon. The HRRR and GFSlamp even
brings some patchy dense fog to east central IL around CMI by
sunrise, while RAP keeps dense fog patches just se of DEC and CMI
late tonight. Will need to watch for fog development and possibly
lower vsbys especially at CMI and maybe DEC too. Have VCSH at PIA
and BMI after 15Z/Mon and VCTS along I-72 after 19Z/Mon where
instability will become higher Monday afternoon. SW winds 5-10 kts
early this evening stay fairly light next 24 hours, and become
light and variable during tonight.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...Geelhart
SYNOPSIS...Geelhart
SHORT TERM...07
LONG TERM...07
AVIATION...07



Area Forecast Discussion

National Weather Service Memphis TN

 903 PM CDT Sun Aug 18 2019

.DISCUSSION...GOES-16 Satellite trends/00Z upper air analysis
depicts a weak mid-level shortwave trough located across Illinois
then into West Tennessee and North Mississippi. This mid-level
shortwave acting as a lifting mechanism combined with instability
triggered the isolated to scattered showers and thunderstorms
across the Mid-South this afternoon into this evening. KNQA WSR-
88D radar trends have shown some dissipation of showers and
thunderstorms across the forecast area with the only areas
remaining thus far along a line from Jonesboro, Arkansas to
Ripley, Tennessee and including a small area near West Memphis. As
of 8 PM CDT, temperatures across the Mid-South are predominantly
in the 70s to lower 80s.

Latest short term model trends including Convective Allowing
Model (CAM) solutions and especially the HRRR suggest this
activity should continue to weaken for the rest of the night and
perhaps ending by 6Z if not sooner. Some adjustments to rain
chances, temperatures, and the potential for some patchy fog
overnight will be made to the forecast to account for these short
term trends.

Updated grids will be available shortly.

CJC

&&

.PREV DISCUSSION... /issued 620 PM CDT Sun Aug 18 2019/

UPDATE...Aviation Discussion.

PREV DISCUSSION... /issued 238 PM CDT Sun Aug 18 2019/

Higher humidity across a good portion of the area this
afternoon...with a few locations in the current heat advisory
reaching 105F+ this hour. Winds were also higher with most
observations in the 10-15 mph range. Showers had developed across
the southwest Delta counties...with thunderstorms just outside of
the CWA.

Late this afternoon and tonight...have increased PoPs across the
northern and western counties for tonight...and late this
afternoon based off the current radar. CAM`s are indicating more
activity this evening along this morning`s lingering outflow
boundary draped across southeastern Missouri/northern Arkansas. A
convective watch was issued just north of the AR/MO border a short
while ago. Main threat would be strong gusty winds that could push
south across the western counties this evening. Plan on adding a
strong storm wording in the HWO. Current heat advisory goes
through 8pm.

Monday and Tuesday...no changes really necessary this period.
Temperatures will climb into the low and mid 90s with potentially
a larger area of 105F+ heat indices. Have held off on extending
or issuing a new heat advisory for Monday as tonight`s convection
could disrupt both timing and area needed. Isolated convection
can be expected both days with activity quickly waning during the
overnight hours. Will have to watch for any lingering outflow
boundaries that enhance storm intensity.

Wednesday through Friday...models still suggesting the wettest
period of the course of next week...mainly as the eastern edge of
the Southern Plains ridge breaks down as heights gradual lower
over the Midwest. A weak surface front will edge closer to the
KY/TN and MO/AR borders sometime early Thursday with a series of
passing shortwaves aloft aiding in convection coverage and
intensity. Some of these storms may be strong as well...but will
leave that wording out of this afternoon`s HWO. Highs will range
from the upper 80s to low 90s...with Wednesday posing the best day
for a heat advisory across southwest portions of the area.

Next weekend...extended models show seasonal to slightly above
normal temperatures with isolated diurnal convection.

JAB

&&

.AVIATION...
00Z TAF Set

Showers and thunderstorms have become outflow dominant and should
gradually weaken and diminish in coverage this evening. Outflow
from storms will result in temporary increased wind speeds and
non-uniform directions. There is some potential for some brief
redevelopment over NW Tennessee/NE Arkansas as outflow boundaries
interact...but will have to wait to see how that develops.
Gradient flow will remain from the South over the next 24+ hours
with wind speeds generally 3-7kt or less. Additional
showers/storms may develop tomorrow afternoon but coverage is
expected to be limited.

30


&&

.MEG WATCHES/WARNINGS/ADVISORIES...
AR...None.
MO...None.
MS...None.
TN...None.
&&

$$