Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 05/08/19
Area Forecast Discussion
National Weather Service Lake Charles LA
949 PM CDT Tue May 7 2019
.UPDATE...
IR satellite and regional radar imagery show an area of deep
convection currently ongoing over the Houston metro area. Outflow
from this convection is enhancing low-level convergence along the
coast and is forcing conditionally unstable parcels characterized
by 2000 J/kg MLCAPE to ascend, resulting in continued development
of deep convection. Abundant deep layer moisture indicated by
1.7"-2.0" PWAT and warm cloud layer depths greater than 3 km has
resulted in efficient precipitation processes with totals
approaching 12 inches in some locations. An analysis of Corfidi
vectors across the region indicate the potential for this
convective complex to progress eastward at around 15-20 knots. As
a result, the greatest potential for heavy rainfall is expected to
remain west of the CWA over the next 1-3 hours (for more detailed
information see WPC MPD 204). However, there will be the
potential for the eastern portions of this convective complex to
reach western portions of Jefferson County and southwestern Hardin
County between now and 1 AM. Therefore, PoPs for this timeframe
have be updated to better reflect the greatest potential for
rainfall across the region.
Beyond the next 1-3 hours, the majority of the short term
guidance has the convective complex weakening and ending by the
time it reaches the far SW portions of the CWA. However, given the
mesoscale nature of this system, radar and satellite trends will
continue to be monitored to see if cold pool balance will persist
and result in continued localized forcing for convective
redevelopment. For now, the inherited forecast for the overnight
period remains representative with no changes made at this time.
&&
.PREV DISCUSSION... /issued 647 PM CDT Tue May 7 2019/
AVIATION...
Storms this evening are moving to the north. Radar was indicating
a few around BPT but they should dissipate over the next hour or
two. Storms moving into Rapides parish will move up to Alexandria
over the next 30 to 45 minutes. For aircraft the main threat will
be from winds... low clouds and lightning. Low ceilings overnight
and through sunrise.
PREV DISCUSSION... /issued 425 PM CDT Tue May 7 2019/
DISCUSSION...
Although a bit earlier than expected, scattered to numerous
showers and thunderstorms have begun moving into southeast Texas
this afternoon in association with a weak upper trof moving up the
the central Texas coastline. A few areas of heavy precipitation
have been producing very high rainfall rates as something of a
preamble of things to come over the next few days. Expect this
activity to continue for the next few hours before becoming more
isolated as the upper support shifts off to the northeast. A weak
warm front lingering over the area overnight will allow for
isolated convection to continue overnight with activity
increasing somewhat by mid morning Wednesday.
The area will be warm sectored between this front and a cold
front extending south from a surface low over the northern plains
for much of the day. A few discreet cells will have the potential
to develop across the area although anemic shear should help limit
supercell development. A swath of already ongoing showers and
thunderstorms associated with the cold front will begin to
envelope the region from the west during the afternoon and
evening. Forecast guidance shows considerable differences in the
intensity of this activity with several short range and high res
models showing a general weakening trend as the line moves into
southeast Texas although confidence in the weakening is somewhat
below average owing to the ECMWF`s consistency in maintaining the
convection. This will have to be monitored closely through the
day tomorrow. SPC continues to highlight an area roughly from
Alexandria southwest to Beaumont in a slight risk for severe
weather with damaging winds and large hail being the primary
threats. A marginal risk extends northwest roughly from Lafayette
to Cameron.
The front is still expected to stall somewhere over the area
Wednesday night into Thursday setting up several days of
widespread heavy rainfall and thunderstorms. Several upper level
features are progged to overrun the surface boundary further
enhancing precipitation although the exact timing and intensity of
these upper level features remains highly in question. A low end
severe weather threat will persist Thursday through Saturday
although the threat appears to be confined to damaging winds.
In addition to the severe weather threat, a heavy rain threat
also remains in play. Precipitable water values in the 1.8 to 2
inch range will allow for very efficient rain makers while the
long duration of the event will set up a potential flash flood
threat especially Friday and Saturday when the ground is expected
to be fully saturated. Overall QPF values are a bit lower than the
previous forecast, but the highest values of 6+ inches are still
expected across interior parts of southeast Texas and central
Louisiana while 4 to 5 inches are expected along a large swath of
the I-10 corridor. The QPF values remain highly subject to change
and will likely do so over the next 24 to 48 hours.
Beyond Saturday, guidance remains highly divergent with the ECMWF
shunting the frontal boundary and the associated moisture offshore
by late Sunday morning showing dry conditions to start the week.
The GFS meanwhile continues to stream copious moisture over the
region within the subtropical jet. Presently have no justification
to lean one way or the other so the official forecast follows a
split the difference philosophy and carries low end PoPs into
early next week.
Jones
MARINE...
Moderate southeasterly winds can be expected this afternoon into
tonight as the pressure gradient tightens in response to lowering
pressures from West Texas to the Plains. A series of upper level
disturbances will traverse the region and a weak frontal boundary
will stall across the area Thursday through the weekend resulting
in several days of widespread showers and thunderstorms some of
which could be strong to severe.
&&
.PRELIMINARY POINT TEMPS/POPS...
AEX 69 85 72 83 / 20 60 40 70
LCH 74 84 75 83 / 30 50 20 60
LFT 72 87 75 86 / 10 40 20 50
BPT 74 82 75 83 / 40 50 40 60
&&
.LCH WATCHES/WARNINGS/ADVISORIES...
LA...None.
TX...None.
GM...Small Craft Exercise Caution through Wednesday evening for
GMZ450-452-455-470-472-475.
Small Craft Exercise Caution from Wednesday morning through
Wednesday evening for GMZ430-432-435.
&&
$$
PUBLIC...26
Area Forecast Discussion...Corrected
National Weather Service Phoenix AZ
602 PM MST Tue May 7 2019
.UPDATE...
Updated aviation discussion.
&&
.SYNOPSIS...
A series of weather disturbances will sweep through the Desert
Southwest for the remainder of the week into the weekend to cause
a prolonged period of cooler than normal temperatures. Isolated to
scattered showers and a few thunderstorms will develop north and
east of Phoenix tomorrow afternoon, with a slight chance of storms
moving into the metro. After a brief warm up to around 90 degrees
on Thursday, better chances for more widespread showers will
arrive this weekend as the storm system deepens over the Desert
Southwest. Isolated thunderstorms will be possible on Sunday
afternoon over the Phoenix metro and Gila County.
&&
.DISCUSSION...
A closed mid-to-upper level low pressure system continues to push
into eastern Arizona as slightly cooler air advects into the
region. Isolated showers and thunderstorms are currently pushing
out of Gila County as scattered to broken clouds with ceilings
generally remaining above 6 kft continue to persist over the
lower deserts with new convection developing over northern
Yavapai County and pushing south. Hi-res models generally show
these storms dissipating before pushing into Maricopa County. This
is corroborated by drier air, negative differential vorticity
advection, and a weak stable layer pushing into midlevels evident
on water vapor imagery and aircraft soundings. Therefore, the
remainder of the day should be quite pleasant across most of the
region with high temperatures struggling to reach 80 degrees over
the lower deserts of south Central Arizona and mid 80s over
southwest Arizona and southeast California. Tonight will be very
pleasant with low temperatures in the mid 50s to lower 60s over
the lower deserts under light diurnal winds.
Another shortwave currently pushing into northern Utah will dig
south tonight into northern Arizona for tomorrow. Models are
continuing to trend towards an increased coverage of storms along
and north of the Rim tomorrow afternoon which seems reasonable
given the midlevel forcing associated with the aforementioned
vorticity center. Moisture may be somewhat limited over northern
Arizona, but precipitable water values will increase to 0.7-0.8
along and south of the Rim. This should be sufficient to initiate
thunderstorms with daytime heating tomorrow afternoon when
temperatures should be 7-10 degrees warmer than today without
significant capping evident on model soundings. Therefore, there
is about a 10-20 percent chance of a thunderstorm or two slipping
into north or northeast portions of the Phoenix metro tomorrow
afternoon compared with less than a 5 percent chance today.
However, most of the Phoenix metro, particularly further south
and west, should remain dry.
The driest and warmest conditions of the forecast period are
expected on Thursday as southwest flow briefly redevelops as the
trough axis becomes very positively tilted to our west. Therefore,
temperatures will briefly warm back up to near 90 degrees for the
lower deserts, albeit still a couple degrees below normal. Beyond
Thursday, a cutoff low is forecast to develop off the coast of
southern California and slowly push east through the weekend
before becoming centered over southern Arizona or northern Sonora
on Monday. Not only will this low pressure entity feature heights
aloft substantially below average (and consequently consecutive
days with temperatures some 10 deg F below normal), but better
quality moisture profiles will materialize via both Pacific and
cross continental origins.
By the weekend, total column precipitable water values will
approach 0.8-1.0 inches (near or above the 98th percentile for
early/mid May) coincident with an unusually cool airmass and
broad cold core aloft. An increasing lobe of vorticity will swing
over this nearly saturated environment with ample SW-to-NE-
oriented isentropic ascent to yield scattered showers on Friday
night into Saturday morning. Surface-based instability also
appears to increase for Sunday and Monday to 200-500 J/kg of CAPE
as the cold core center moves overhead, making isolated
thunderstorms a decent possibly on Sunday afternoon over the
Phoenix metro and Gila County and Monday afternoon north and east
of Phoenix. The timing uncertainty precludes pinpointing higher
POPs for any specific time, but showers and possibly a few
thunderstorms will occur at least once, if not twice between
Friday night and Monday morning.
&&
.AVIATION...Updated at 0100 UTC.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Late this afternoon, the greater Phoenix area is in the wake of
departing low that brought showers to the area earlier today. A
drier and more subsident northwest flow aloft is in place behind the
low, resulting in thinning of the cumulus field that formed over the
central deserts. There is another disturbance dropping in from the
north - behind the main departing low - that has generated an area
of showers north of the Phoenix area. However, this cluster of
showers and/or storms will likely dissipate within the next 1-2
hours. as it moves off high terrain and into the deserts, and
thus should not reach the terminals.
Outflow winds moving in from the north early this evening -
associated with the area of showers - is not likely; threat is not
zero but too low to mention in the TAFs. Winds this evening should
favor the west/southwest with a few gusts into the teens possible
thru about 03z. Expect some lingering high based cumulus/mid level
debris cloud overnight, with mid could thickening up after 11z.
Thus, expect areas of BKN CIGs 10-12k feet during the morning hours
before the mid cloud thin leaving behind some SCT cumulus decks with
bases 7-9k feet. Otherwise, winds should return to the
east/southeast after midnight, and at KPHX this transition may be
late and not until 11-12Z. West winds return again after 19z with
gusts into the teens likely for the TAF sites.
Southeast California/Southwest Arizona including KIPL and KBLH:
Winds to favor the west next 24 hours at KIPL with gusts to 25kt
possible thru around 05z, after midnight wind taper off to around
10k. Winds to favor the south/southwest at KBLH next 24 hours. Skies
generally clear through Wednesday afternoon with just some high
clouds possible at times.
Aviation Discussion not updated for amended TAFs.
&&
.FIRE WEATHER...
Friday through Tuesday:
A series of weather disturbances will result in much cooler than
normal temperatures, rising humidity values, and increased chances
for light showers and thunderstorms over most districts. Although
most areas will remain dry on Friday, several weather systems will
congeal over southern California and Arizona during the weekend
into Monday with showers and a few thunderstorms likely over both
higher elevations and the lower deserts. Pockets of wetting rains
will certainly be possible. Afternoon humidity levels will be
quite moist by mid May standards only falling into a 20-30% range
every day. Occasional breezy afternoon winds will exist with the
approach of these weather systems, but winds may become light and
variable over the weekend into Monday as clouds and showers settle
over the area. Drier and warmer conditions should begin to filter
into the region by Tuesday into the middle of next week.
&&
.SPOTTER INFORMATION STATEMENT...
Spotter activation is not expected for the next 7 days.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&
$$
DISCUSSION...Hopper/MO
AVIATION...CB
FIRE WEATHER...Hopper/MO