Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 07/14/19
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
701 PM CDT Sat Jul 13 2019
.SHORT TERM...
249 PM CDT
Through tonight...
Weak cold front continues to sag south across northern IL this
afternoon in a very unstable but capped atmosphere. Surface based
CAPE values pushing 4000 J/kg remain weakly capped per area
aircraft soundings in an otherwise very weakly forced environment.
Given limited convergence and forcing along the cold front...
expect storms that do pop up this afternoon to remain limited in
coverage. Coverage may be enhanced somewhat however by MCV
currently associated with decaying convection over IA moving east.
Current extrapolations have this MCV reaching north central IL by
late afternoon.
Otherwise lake breeze boundary also beginning to finally make a
good push inland as best evidenced on the ORD TDWR. This
boundary may also provide the bit of forcing needed to break
through the cap and initiate showers and storms. Given these
different possible scenarios will continue 25-35% POPs into the
evening. Given the pop up nature of storms... any extrapolation
won`t be possible until after storms develop.
Challenging forecast into the overnight as well with lack of any
real forcing to support organized convection. That being said...
some CAMS solutions continue to show storms organizing into
clusters to our west this evening supported by an intensifying low
level jet. These storms would then move east into the local area
during the late evening and into the early overnight. Hence will
continue to carry low showers/thunderstorm chances into the
overnight.
Ed F
&&
.LONG TERM...
128 PM CDT
Sunday through Saturday...
For the long term forecast period, main concerns will focus around
temperatures as several days with max temps in the lower to middle
90s are expected.
By Sunday, the upper level pattern will be trending towards zonal
flow over the nrn CONUS, including the Upper Midwest and Great Lakes
regions. The upper level long wave pattern will be comprised of
broad upper ridging centered over the Four Corners region and weaker
upper ridging over the sern CONUS. The remnants of Hurricane Barry
are expected to track north through a weakness in the upper level
pattern, through the Lower Mississippi Valley. The longer range
guidance is in relatively good agreement on the track of the
remnants of Barry, reaching as far north as southern Illinois by
Tuesday evening and then getting picked up and turning eastward as
it interacts with the stronger westerlies, quickly moving away from
the local area. There is a chance that some moisture associated
with the tropical system could spread as far north as the southern
portions of the CWA Tuesday into Tuesday night before lifting off to
the east.
Otherwise, as mentioned above, the trend for the long term forecast
period will be for above normal temperatures with periodic low
chances for shra/tsra. With a zonal pattern setting up across the
region, timing of individual weak, sheared out shortwaves will be
low confidence, so any PoPs will be slight chance to low chance.
Highs from mid week into next weekend are expected to be at or above
90 F, with dewpoints,generally, in the lower 70s. This would suggest
Heat Index reading above 100 F. The warmest and most humid days of
the long term forecast period right now look to be Thursday and
Friday when temperatures in the middle 90s and dewpoints in the
middle 70s would combine for Heat Index readings of 105 to 110
degrees. There is some uncertainty towards the end of the period
with the GFS suggesting a cold front pushing through the region on
Friday, while the ECMWF is about 24 hours slower with the fropa, not
until Saturday.
&&
.AVIATION...
For the 00Z TAFs...
701 PM...Primary forecast concern is thunderstorm potential this
evening and again Sunday afternoon/evening.
A cold front is moving across the area shifting winds to the
northeast. A few thunderstorms have developed west and south of
mdw. Confidence for how widespread thunder activity becomes this
evening is low. Now that a few storms have formed with outflows
along with the lake breeze/cold front...its possible that isolated
thunderstorms will continue through mid/late evening...likely
south of ord/dpa and near mdw/gyy. Maintained vicinity mention for
the next few hours and after sunset any remaining activity should
be well south of the terminals.
Confidence remains low for thunder Sunday afternoon into Sunday
evening. With no significant trends maintained prob mention with
this forecast. There should be a lake breeze/easterly flow for
ord/mdw/gyy and this may allow anything that does develop to
remain west of ord/mdw. cms
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.
&&
$$
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Area Forecast Discussion
National Weather Service Phoenix AZ
527 PM MST Sat Jul 13 2019
.UPDATE...
Updated 00Z aviation discussion.
&&
.SYNOPSIS...
A strong high pressure system will remain parked over the region
through next week providing an extended period of very hot weather.
Moisture will increase very slightly this weekend with the threat of
isolated storms mainly limited to high terrain area of eastern and
southern Arizona, but outflows and dust could sweep into lower
elevations. Drier air will sweep into the area through much of next
week reducing any thunderstorm chances.
&&
.DISCUSSION...
Atmospheric moisture is keeping temperatures slightly cooler than
yesterday despite the reduced cloud cover. Excessive heat
warnings remain in effect just for portions of Southeast
California and the Tonto Basin for today.
As of now, visible satellite shows convection over the
Mogollon Rim as well as a cluster of weak showers over southern
Maricopa County. For later this afternoon and evening,
thunderstorm development over southern Arizona, aided by over 1000
j/kg of downdraft CAPE, may produce downbursts and perhaps send
the most significant outflow of this dawdling monsoon northward
towards southern Maricopa and Pinal Counties. Outflows in this
area will likely be able to kick up dust as it traverses over
open desert and fallow farm fields. The potential for a dust storm
impacting Casa Grande westward towards Gila Bend along the
Interstate 8 corridor is the greatest but latest model trends are
moving away from this solution. Additional convection is possible
late across the higher terrain east of Phoenix and may again be
able produce a weak shower or over the lower desert, similar to
Friday night, with enough outflow interaction. However, the impact
of any activity over the Valley is not likely to be significant
by most measures. Otherwise, the hi-res models also paint the Kofa
range and the Imperial Valley as other potential areas for storm
activity, primarily due to terrain features, but coverage will be
isolated.
Lingering moisture on Sunday will again favor afternoon convection
over the Arizona High Country with minimal chances for the lower
desert as model trends continue to show less activity for Sunday.
A sagging Pacific trough to our west will redirect the flow aloft
to a more southwesterly direction pushing the monsoon high and
the deepest moisture further east out of our forecast area for
the start of the week. Surface dew points will plummet well below
50 degrees and mixing ratios will drop below the desired 8 g/kg
usually needed for thunderstorms. The drop in moisture will also
allow afternoon high temperatures rise into the 112-116 degree
range Monday/Tuesday leading to another excessive heat warning for
the Phoenix area.
Moisture from Sonora and nightly gulf surges may seep into
southern Arizona later in the week bringing a temporary moisture
flux into the area. Still, storm chances will remain over
southeast Arizona and the Rim, far away from the lower desert.
Phoenix and everywhere else further west will not likely see much
monsoon activity at all next week. Long range model guidance is a
little more optimistic beyond the forecast period into next
weekend but much can change before then.
&&
.AVIATION...Updated at 0027 UTC
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Westerly 20-25 knot wind gusts will continue for the next few
hours at the Phoenix terminals as isolated thunderstorms continue
to develop along the higher terrain to the east and southeast.
Steering flow above 10 kft is out of the E-SE, so the storms
currently north and east of TUS will be of greatest concern.
Although aircraft soundings currently do not show enough moisture
at midlevels or the surface to maintain storms into Phoenix, these
storms should be strong enough to push at least a weak E-SE
outflow into KIWA between 02-03Z and KPHX and the other terminals
between 03-04Z. A brief period of blowing dust with reduced MVFR
visibilities is possible, though gusts are currently expected to
remain below 30 knots. Hi-res models are also showing isolated
showers or virga moving through overnight as well, but confidence
is low considering these models are not handling the current
evolution of convection well. Winds will most likely become light
and variable overnight with ceilings remaining above 10 kft.
Southeast California/Southwest Arizona including KIPL and KBLH:
Southerly winds continue to remain around 15-20 knots with slow-
moving isolated thunderstorms about 20 SM E-NE of KBLH. Although
thunderstorms are currently not expected at KBLH, there is a low
chance of an easterly outflow producing blowing dust or triggering
new convection after 02Z. However, confidence is too low to
include this so for now we just have winds veering a bit to the
S-SW and gradually subsiding this evening. At KIPL, SE winds
should rapidly veer to southwesterly sometime between 01-02Z with
gusts up to 25 knots before subsiding later in the evening.
Aviation Discussion not updated for amended TAFs.
&&
.FIRE WEATHER...
Tuesday through Saturday:
Temperatures will drop to more seasonal conditions through the
week. Daytime RH values will struggle to stay above 15% with
overnight recovery into the 25-40% range for most locations. The
winds will remain fairly light with some afternoon breezes
favoring typical diurnal tendencies. Chances for thunderstorms
will be very low, and any that do develop, will favor the higher
terrain well north and east of Phoenix with hardly any chance for
rain for the lower desert.
&&
.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Excessive Heat Warning from 10 AM Monday to 8 PM MST Tuesday for
AZZ537-540>544-546-548-550-551-553-554.
Excessive Heat Warning from 10 AM to 8 PM MST Monday for AZZ532-
534-536-538-539-559.
Excessive Heat Warning until 8 PM MST Tuesday for AZZ556.
CA...Excessive Heat Warning until 8 PM PDT Monday for CAZ566>568.
&&
$$
DISCUSSION...Deems
AVIATION...Hopper
FIRE WEATHER...Deems