Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/29/18
Area Forecast Discussion
National Weather Service Birmingham AL
803 PM CDT Wed Mar 28 2018
.UPDATE...
MESOSCALE UPDATE.
&&
.SHORT TERM...
Closely monitoring a QLCS moving across central Mississippi at
this time. Warnings still ongoing over there, but have not seen
many severe reports lately, which certainly does not mean storms
are not severe. These storms have indicated large hail, damaging
winds and rotation on the comma head feature and with additional
southern flank convection.
The latest convection allowing models and RAP analysis have
convection weakening as it approaches the Alabama state line in
more marginal instability. But these shorter term models do not
have the current situation diagnosed adequately. The storms are
much farther east and are indicative of stronger updrafts. These
storms were forming near a weak wave along a quasi-stationary
boundary/effective warm front/convergence zone that has been
present all day. It appears that the storms have enhanced their
own environment along the boundary as low level winds above
surface winds increase.
Therefore, expect some storms to make it into Central Alabama,
especially Pickens, Lamar, and Marion Counties...possibly Fayette
and Winston Counties. The timing appears to be after 930 pm near
the state line. The main threat with the storms if they hold some
strength will be wind gusts to 45 mph and some dime size hail.
Will closely monitor the tornado threat as there is shear along
the boundary and LCL heights will lower with time. But we need a
sustained updraft and that is the question at this time.
So be aware that some strong storms are possible late this evening
northwest.
75
Previous short-term discussion:
Central Alabama is currently positioned on the west side of an upper
level ridge that extends from the eastern Gulf of Mexico northeast
toward coastal North Carolina. A deep positively tilted trough
at H500 was analyzed from western Kansas extending southwest into
northwest Texas and into eastern New Mexico. Toward the surface,
a stationary front was aligned in a southwest to northeast
position from southern Texas through the Ohio River Valley Region
and into western Pennsylvania. A warm front extended from a
surface low in western Pennsylvania along the front to the
southeast to near the entrance of the Chesapeake Bay in Virginia.
Ongoing convection along the front from central Texas into western
Tennessee has produced an outflow boundary that was analyzed from
central Texas into northwest Louisiana and into northern
Mississippi, generally from just south of Greenville to near Tupelo,
and into west-central Tennessee. Satellite imagery depicts cloud
cover increasing across forecast area from west to east with a
southerly trajectory near the surface and a more southwest flow
aloft. Radar imagery indicates generally light shower activity
associated with the aforementioned outflow boundary from central
Mississippi that extends northeast into far northwest Alabama and
into central Tennessee.
Low-level thermal and moisture advection will persist from the south
winds that will remain gusty at times this afternoon and into early
evening. Winds will decrease to some extent overnight as the
boundary layer decouples with the loss of vertical mixing provided
by daytime heating but expect the warm advection regime to
continue. Cloud cover will continue to stream overhead from the
west and southwest, becoming thicker across our western counties
overnight and gradually increasing in coverage over our eastern
counties this evening into early Thursday morning.
The severe weather potential on Thursday will be provided by wind
shear and helicity provided by dynamical support that has been
fairly consistent in current and recent convection-allowing models
(CAMs). Sufficient near-surface instability is less certain as
thicker cloud cover across the area tomorrow morning through midday
will help to discourage solar insolation and yield lower levels of
instability. However, thermal and moisture advection will continue
to help increase instability in the lower levels and overcome the
impact of the cloud cover present. The biggest limiting factor
will be where exactly is the outflow boundary from tonight`s
activity to our west. If the outflow stays where the models
indicate then the severe potential will remain possible. If it
makes it further east, then the severe potential will be limited
at best.
What is consistent at this point in time is that sufficient dynamics
exist to support strong to severe thunderstorms on Thursday with the
amount of available energy remaining in question. The better
potential of realizing sufficient instability remains across our
southern counties and potentially across our east-central counties
if cloud cover remains less dense through midday. The risk for
strong to severe storms area wide will be dependent on the amount of
low level instability provided by solar radiation. There is enough
consistency to raise the confidence of the threat to a 2, but will
keep the area of concern the same.
05/16
.LONG TERM...
Friday through Tuesday.
A return to quiet weather should return for Friday as the upper
low swings through the north during the morning. Clearing skies by
the afternoon as high pressure builds into the area and will
remain through Sunday. Rain chances could start to increase on
Monday into Tuesday as a front approaches from the north, but does
not make it through the area at all. Temperatures in the north
will be highly dependent on where the front sets up and which way
it fluctuates each day as it will be quasi-stationary through
midweek.
16
&&
.AVIATION...
00Z TAF Discussion.
Attempted to give some trend of weather conditions the next 24
hours but expect updates as the mesoscale will play a prominent
role in the precipitation. A QLCS over central Mississippi is
moving toward the Alabama state line and should remain north of
all terminals overnight.
Ceilings should dive into the MVFR range by 4-5z west and spread
to the remainder of the through 09z or so. Nice warm air advection
hodograph and isentropic lift covers the state by morning. Expect
some weakening of the storms in Mississippi, but a boundary sets
up that will allow additional storms on Thursday. Mentioned light
rain and VCTS as early as 15-17z north and ending before 00z with
a few hour delay for southern sites. Once again, this does not
mention the activity now as an expected decrease is anticipated
but may need adjusting if it can hold together.
Predominant MVFR ceilings on Thursday with times of IFR and VFR
here an there. Most areas eventually reach VFR ceilings around
00z, but trends indicate this may not last too long.
Winds south to west during the period with some gusts up to 20kts
or so.
75
&&
.FIRE WEATHER...
Shower and thunderstorm chances will slowly increase from
northwest to southeast tonight, ahead of an approaching front.
Low clouds and patchy fog could become possible Thursday morning
as low level moisture increases. The best rain chances will be
Thursday afternoon and evening, as the front moves through the
area. Drier conditions are expected by Friday. There are no fire
weather concerns at this time.
&&
.PRELIMINARY POINT TEMPS/POPS...
Gadsden 60 73 51 66 39 / 20 100 70 10 0
Anniston 59 75 52 68 40 / 10 90 90 10 0
Birmingham 62 75 52 67 43 / 30 100 60 10 0
Tuscaloosa 64 73 51 69 43 / 30 100 30 10 0
Calera 62 74 52 69 44 / 20 100 70 10 0
Auburn 59 74 56 69 45 / 10 70 100 10 0
Montgomery 61 78 56 72 44 / 10 80 90 10 0
Troy 61 78 57 72 45 / 10 70 100 10 0
&&
.BMX WATCHES/WARNINGS/ADVISORIES/...
None.
&&
$$
Area Forecast Discussion
National Weather Service Columbia SC
739 PM EDT Wed Mar 28 2018
.SYNOPSIS...
High pressure offshore will continue dry weather and above
normal temperatures through Thursday. The chance for showers
will increase Thursday night into Friday ahead of a cold front,
and thunderstorms may also be possible. The return of high
pressure will bring dry weather and mild temperatures for the
weekend.
&&
.NEAR TERM /UNTIL 7 AM THURSDAY MORNING/...
High pressure will remain offshore of the Carolinas overnight
with southwesterly winds continuing to push moisture into the
region. With the increasing moisture there will be potential for
patchy fog development, however this will be offset by
persistent winds between 5 and 10 mph. Expect the wind to keep
the near surface layer mixed enough to prevent fog and have not
mentioned fog in the overnight forecast. With the increased
moisture some cloudiness will develop overnight and will help
insulate the region to keep overnight lows in the mid to upper
50s.
&&
.SHORT TERM /7 AM THURSDAY MORNING THROUGH FRIDAY/...
Warm and dry condition expected Thursday. Downslope flow and
compressional heating will allow temperatures to rise into the
low to mid 80s. The upper level ridge will move offshore
Thursday and surface high pressure ridging into the area from
the western Atlantic will move out to sea Thursday night,
allowing moisture to increase ahead of an approaching cold front
and upper level trough. The cold front will cross the area
Friday morning, then move offshore during the afternoon. The
best chance for showers will be late Thursday night into Friday
morning. Cannot rule out isolated thunderstorms on Friday given
weak instability just ahead of the front. Rainfall amounts will
average one half inch or less.
High temperatures in the 80s expected Thursday with lows in the
lower 60s Thursday night. Highs Friday still expected to be
above normal...in the mid to upper 70s.
&&
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Dry weather expected for the weekend with surface high pressure in
control and a nearly zonal flow aloft. Near normal temperatures in
the low to mid 70s Saturday will warm into the mid and upper 70s for
Sunday. Nighttime lows in be in the 40s.
Unsettle conditions possible Monday through Wednesday. Models
indicate a progressive level pattern with a cold front affecting the
area Monday and again Wednesday. Temperatures are forecast to be at
or above normal with highs in the 70s and lows in the 50s.
&&
.AVIATION /00Z THURSDAY THROUGH MONDAY/...
VFR conditions expected through the TAF period.
High pressure has shifted offshore and southwesterly winds are
expected to prevail through the forecast period. Model forecasts
of a 30 knot low level jet overnight should inhibit fog
formation while helping keep a bit of wind overnight. Some
indications in the MOS guidance that there could be a brief
period of fog around 12z but confidence is low and latest HRRR
not supporting this. Expect some high clouds overnight and then
as heating takes place on Thursday a diurnal cumulus VFR cloud
deck expected to form after 15z. Winds could become gusty with
some gusts over 20 knots.
EXTENDED AVIATION OUTLOOK...Restrictions possible Thursday
night and Friday as a cold front with showers...possible
thunderstorms...crosses the region.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
&&
$$
previous package. Previous forecast discussion is included below.
31
/Issued 405 AM EDT Wed Mar 28 2018/
The long term period will start will unsettled weather as a
cold front is forecast to move across the area Thursday night and
possibly early Friday. The front will bring showers and a chance of
thunderstorms. Instability associated with the front and a surface
trough out ahead of the front, will be weakening overnight Thursday
but there is decent low level shear associated as well.
There will be a marginal risk for severe thunderstorms at the
start of Thursday night favoring north and west GA.
Strong gusty winds, frequent lightning and locally heavy rain will
be the mostly likely hazards.
Friday there will be some lingering shower chances with the exiting
front and upper short wave.
The weekend will be mostly dry with moisture from the cold front
skirting mainly far n GA on Sunday. After that, the GFS and European
models are Not very consistent with handling the deeper moisture in
the upper flow but any shower chances look to favor n GA the most
through Tuesday.
Temperatures will start out above normal at the very start of the
long term but return closer to normal for Friday and Saturday.
Sunday through Tuesday look to have near to above normal
temperatures.
BDL
AVIATION...
00Z UPDATE...
VFR cigs around the ATL terminals have largely abated with just
some BKN high clouds to contend with. This will be changing into
the overnight hours however with MVFR cigs moving in from the SW
by 10Z. These look to hold on well into Thu before giving way to
VFR conditions during the afternoon to go along with gusty winds.
SHRA to move in by 22Z to 00Z and have also added prob30 for TSRA
in for ATL.
//ATL CONFIDENCE...00Z UPDATE...
Medium on MVFR cig timing.
High on remaining elements.
Deese
&&
.PRELIMINARY POINT TEMPS/POPS...
Athens 56 76 57 72 / 0 40 70 30
Atlanta 58 73 55 67 / 5 50 80 20
Blairsville 53 68 51 62 / 10 70 90 20
Cartersville 56 72 53 65 / 5 70 80 20
Columbus 59 75 59 73 / 5 50 70 10
Gainesville 56 71 55 67 / 5 50 80 20
Macon 56 79 60 74 / 0 30 70 30
Rome 57 72 53 65 / 10 80 80 20
Peachtree City 56 74 55 69 / 5 50 70 10
Vidalia 58 82 64 75 / 0 0 50 50
&&
.FFC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Deese
LONG TERM....Merritt
AVIATION...Deese
Area Forecast Discussion
National Weather Service Grand Rapids MI
847 PM EDT Wed Mar 28 2018
LATEST UPDATE...
Update
.SYNOPSIS...
Issued at 330 PM EDT Wed Mar 28 2018
Rain showers will develop very late tonight through Thursday as
a low pressure system moves across the Ohio Valley region
Thursday. High pressure will bring fair weather Friday. The next
low pressure system will bring a mix of rain and snow Saturday.
An unseasonably cold airmass will move in behind that system for
Sunday and Monday.
&&
.UPDATE...
Issued at 847 PM EDT Wed Mar 28 2018
I increased the POP and QPF over our central CWA overnight.
As it turns out there is significantly more showers going on
across WI and southern Lake Michigan at 8 pm than either the 12z
or 18z NAM forecast (much father north)showed or forecast. The
HRRR / HRRRX runs continue to do much better in that regard, so,
I update all of our GRIDs into mid morning Thursday to follow a
mix of CONSHORT, HRRRTL and the latest HRRR,HRRRX and RAP13 pop
and qpf. This brings likely rain to GRR overnight and increases
the area of patchy fog into midday Thursday. Seems the major
difference in the models (NAM compared to RAP) is he relative
humidity is close to saturation below 850 farther north on the
high res models than on the NAM. Since it is raining under those
showers north to MKE, seems clear increased pop/qpf is warranted.
Either way it is to warm for snow over all of our CWA into late
afternoon. So I did not change that part of our forecast.
&&
.SHORT TERM...(This evening through Friday night)
Issued at 330 PM EDT Wed Mar 28 2018
Rain showers will develop during the early morning hours Thursday
over our southern fcst area as a low pressure system moves
northeast into the Ohio Valley region Thursday morning.
A consensus of latest short range guidance suggests that the
steadiest rain will occur over our se fcst area where a quarter to
half inch of rainfall is expected. Meanwhile no rain is expected
over our nw fcst area.
A few wet snow flakes may mix in Thursday evening before pcpn
ends. However it still looks like significantly colder
air will not advect in until late Thursday night when pcpn will
already have come to an end. Therefore there will be no snow
accumulation.
High pressure will bring fair and seasonably cool wx Friday. Some
light mixed pcpn will begin to develop Friday night but most of
the pcpn with the next low pressure system will hold off until
Saturday.
.LONG TERM...(Saturday through Wednesday)
Issued at 330 PM EDT Wed Mar 28 2018
A strengthening low pressure system will move east across the
northern Great Lakes region Saturday and bring a mix of rain and
snow. There is still some uncertainty with regard to the exact
track of the low pressure system which has large implications on
potential for accumulating snow. At this time we will continue to
fcst a mix of rain and snow and potential for light snow
accumulations mainly over our northern fcst area.
Strong nw flow caa will occur behind this system Saturday night.
H8 temps will plummet to -15 to -17 C by 12Z Sunday yielding delta
t/s in the lower 20`s. Therefore nw flow lake effect snow showers
will develop Saturday night and continue into Sunday. It will be
unseasonably cold Sunday with high temps only reaching the lower
to perhaps middle 30`s.
The active wx pattern will continue early next week as another low
pressure system moves east across our region Monday into Tuesday.
This system will bring potential for mixed pcpn once again from
Monday afternoon through Monday night into Tuesday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 742 PM EDT Wed Mar 28 2018
I have gone with the high resolution model forecast for just how
far north the rain gets tonight into Thursday. This would suggest
meaningful rain may get as far north as MKG in the 09z to 15z time
frame. The I-69 TAF sites will get solid IFR cigs/vsby from 09z
through 15z (more or less). All areas should see improving
cigs/vsby in the 18z to 21z time frame.
&&
.MARINE...
Issued at 330 PM EDT Wed Mar 28 2018
Wave heights will ramp up Thursday afternoon through Thursday
evening as northerly winds increase to the north of the Ohio
Valley low pressure system. Therefore we will issue a small craft
advisory for all our nearshore zones from Thursday afternoon
through Thursday night.
&&
.HYDROLOGY...
Issued at 1021 AM EDT Wed Mar 28 2018
Rivers are experiencing small rises due to the recent rain, but
flooding is not expected. Several chances for rain and/or snow are
on tap this week, with under a half inch tonight into Thursday
night. Additional light rain/snow is possible Saturday and early
next week. This precipitation is not expected to lead to flooding.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Small Craft Advisory from noon Thursday to 6 AM EDT Friday for
LMZ844>849.
&&
$$
UPDATE...WDM
SYNOPSIS...Laurens
SHORT TERM...Laurens
LONG TERM...Laurens
AVIATION...WDM
HYDROLOGY...63
MARINE...Laurens
Area Forecast Discussion
National Weather Service Houston/Galveston TX
902 PM CDT Wed Mar 28 2018
...LOCALLY HEAVY RAIN POSSIBLE TONIGHT...
.DISCUSSION...
Concern is increasing that heavy to excessive rain will
persist/develop overnight. At the surface a weak area of low
pressure was noted near Alice with a weak trough of low pressure
extending to the north to near Tyler. G 00z sounding showed PW
values around 1.80 inches with CAPE values between 2500-4500 J/Kg
and unstable lapse rates. GOES-R PW field show values between
1.80 and 2.00 inches and this matches up well model progs and
soundings. 00z 300 MB wind analysis shows a splitting jet
structure over East Texas with a speed max rotating around the
base of the upper trough. SE TX will lie in the RRQ of a 140 kt
between 06-09z and feel there will be a period of heavy rainfall
with training of cells along the Highway 59 corridor late this
evening into the overnight. Some of the latest short term guidance
is becoming quite generous with rainfall amounts tonight with
some 3 to 6 inch totals possible. PoPs were already high tonight
but have increased the QPF over the area for the possible training
of cells later tonight. Tornado Watch will be allowed to expire
and the Flash Flood Watch will be maintained as is with the north
expiring at 100 AM and areas to south at 7 AM Thursday. 43/11/08
&&
.PREV DISCUSSION... /ISSUED 651 PM CDT Wed Mar 28 2018/
AVIATION...
Radar imagery currently shows the worst of the thunderstorms
located east of CXO and IAH, but anticipating redevelopment this
evening for TAF sites at HOU and northward. HRRR shows the
possibility for showers and isolated thunderstorms moving across
the northern TAF sites at CLL between 02-05z. The main line of
precip will continue to sag southward impacting CXO until 09Z and
pushing south of GLS between 12-13Z. Light and variable winds are
anticipated Thursday morning, and ceilings should begin to lift
eventually clearing out by 18Z across all TAF sites. Southwesterly
flow around 5-8 kts will prevail by the afternoon hours.
Hathaway
PREV DISCUSSION... /ISSUED 354 PM CDT Wed Mar 28 2018/
DISCUSSION...
Active day across Southeast Texas today as a line of thunderstorms
continues to slowly drift to the southeast. Expectations for
severe and flooding potential through tonight have changed little
from earlier. Once any lingering rain tomorrow morning clears out,
look for fair weather until early next week.
Threat Summary:
Flooding - Individual storms continue to train to the northeast
while the entire line drifts slowly southward. This creates
continued potential for flash flooding into tonight, following the
drift of the line. Widespread rains of 1-3 inches are still
expected, but localized rains of 4-7 inches are possible. In
general, this will be most impactful on streets and areas of poor
drainage. Street flooding will become increasingly more dangerous
after sunset, as it will become even more difficult to determine
the true state of roads in the dark. As always, never attempt to
travel on any water-covered roads, and it may simply be best to
find a safe place and stay in for the night. Rivers and bayous are
expected to rise, but most should stay within their banks.
However, flooding in some channels may be possible and flows even
for streams within their banks will be faster than normal.
Hail - Severe hail is possible with the strongest storms. High
freezing heights/wet bulb zeroes will limit potential size of
hail below two inches.
Luchs
MARINE...
South winds 15 to 20 knots and gusty will be on tap the remainder of
the afternoon then should gradually diminish as outflow from storms
over SETX expands toward the coast. Strong to severe thunderstorms
possible in the bays and nearshore waters this evening. This long
fetch has seas of 5-9 feet pushing through the area toward shore.
Elevated tides and runup continues with moderate south winds. Minor
flooding around 87 near High Island possible.
Outflow should reach the coast tonight making for more chaotic
winds. A cold front should finally push through early Friday morning
with offshore flow but only short lived as winds come back around to
the east and southeasterly by Saturday morning. Southeasterly flow
then continues through at least Tuesday. Some differences with
respect to the next front (GFS washing out in SETX Wednesday
afternoon and ECMWF outflow possibly nearing the coast Thursday
morning) so confidence low at that time but fortunately the marine
forecast only goes out to Monday night.
45
CLIMATE...
As of 3pm CDT, Easterwood Field in College Station has recorded
3.12 inches of rain. This already exceeds the record rainfall of
2.87 inches, which was set in 2006. Rain has not yet begun in
earnest at any of the other main climate sites, but for what it is
worth, the forecast rainfall for the City of Houston (IAH) and
Hobby Airport are near their record values.
Luchs
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 61 80 54 76 54 / 60 10 0 0 0
Houston (IAH) 65 82 57 78 54 / 90 10 0 0 0
Galveston (GLS) 67 75 63 74 62 / 100 30 0 0 0
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Flash Flood Watch until 1 AM CDT Thursday for the following
zones: Austin...Brazos...Burleson...Colorado...Grimes...
Houston...Madison...Montgomery...Polk...San Jacinto...
Trinity...Walker...Waller...Washington.
Flash Flood Watch until 7 AM CDT Thursday for the following
zones: Brazoria...Chambers...Fort Bend...Galveston...
Harris...Liberty...Matagorda...Wharton.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION until 1 AM CDT Thursday for
the following zones: Galveston Bay...Matagorda Bay.
SMALL CRAFT SHOULD EXERCISE CAUTION until 7 AM CDT Thursday for
the following zones: Coastal waters from Freeport to the
Matagorda Ship Channel out 20 NM...Coastal waters from High
Island to Freeport out 20 NM.
Small Craft Advisory until 7 AM CDT Thursday for the following
zones: Waters from Freeport to the Matagorda Ship Channel
from 20 to 60 NM...Waters from High Island to Freeport from
20 to 60 NM.
&&
$$
Discussion...43
Area Forecast Discussion...UPDATED
National Weather Service Huntsville AL
838 PM CDT Wed Mar 28 2018
.NEAR TERM...(Tonight)
Issued at 837 PM CDT Wed Mar 28 2018
Clusters of showers and thunderstorms associated with a slow moving
cold front are now at our doorstep as they slowly progress ENE across
Mississippi. Thanks to the strengthening 50-60 kt 850 mb jet along
the AL/MS border, this activity has been able to organize into two
distinct clusters and broken line segments. The northern line,
located from near Bolivar, TN to near Pontotoc, MS should lift ENE
into far Northwest Alabama around 0230z. The second line to the
southwest is located roughly from Oxford, MS to Durant, MS, which may
approach Franklin County by 3:30z. While both lines possess the
capability for locally heavy rainfall and gusty winds, this southern
line has been notably stronger and maintained a couple of strong
mesocyclones across over the past 2-3 hours.
The thermodynamic environment across Northwest Alabama (and
especially east of there) is more stable, with only 300 J/kg of MLCAPE
observed near the MS/AL border. A more backed surface flow has
helped maintain a slightly drier boundary layer, with dewpoints in
the upper 50s to around 60 degrees. However, as this LLJ lifts
northeast, low-level and bulk shear will become more favorable for
the maintenance for these organized strong to marginally severe line
segments. Thus, a localized damaging wind gust cannot be ruled out
with any of this activity. Also, a diffuse, but remnant outflow
boundary over this area and the good low-level directional shear
means a brief, isolated, weak tornado cannot be ruled out -- though
the probability is very low. The peak severe threat will likely be
confined to Northwest Alabama, and generally in the 03-06z window,
tied to this LLJ feature. The overall lack of instability will keep a
vast majority of this activity from getting too strong.
Of greater concern is the potential for heavy rainfall and localized
flash flooding in the Flood Watch area of Northwest Alabama. PWATs
are currently around 1.5". With the advection of richer moisture
(thanks to the LLJ), a slow moving boundary, and the mean flow
parallel to this boundary, the environment will be primed for
training overnight. In the heavier cores, rainfall rates of 0.75" to
1" per hour are possible. It is conceivable that 2"/3-hr flash flood
guidance may be exceeded in a few spots in this watch area
overnight. The latest runs of the HRRR continue to resolve this and
paint a heavier band of 2-3" of rain along the AL/MS border
overnight, just clipping far western Colbert and Lauderdale Counties.
Have bumped in QPF slightly given these trends and will certainly
need to monitor the flash flood threat closely in areas where
training does occur.
Due to the nature of slow moving boundary, areas east of I-65 will
likely only see scattered showers (at best) and may stay dry all
together. Thus, a tight precipitation gradient will exist from west
to east. Have maintained this thinking in the forecast, with 90-100%
across our far western areas and 20-30% along the AL/GA border.
.SHORT TERM...(Thursday through Friday)
Issued at 232 PM CDT Wed Mar 28 2018
Latest model runs are showing the mid level ridge breaking down
slightly quicker than previous forecasts which means the upper level
trough will be able to swing through and push that cold front east
into N. AL quicker. This more progressive solution means less overall
rainfall as the rain, which will actually be along a prefrontal
trough/leftover surface low, will move through faster on Thursday.
By 18z, the leading edge should be over Huntsville and in NE AL by
21z. By 00z, the GFS/CMC clear out NW AL with the ECMWF/NAM a little
later and not drying NW AL until 06z. It was also noted that some
guidance is showing a bullseye of higher QPF along the Gulf coast
and into central AL which would help slow the moisture stream over N
AL and lower the rainfall amounts. Total rainfall amounts have
therefore continued to decrease to a little over 2 inches in NW AL to
half an inch to an inch in NE AL and southern middle TN. Outside of
NW AL, the bulk of the rain will fall after 15z Thursday.
In terms of thunderstorms, it`s quite tricky and not certain. It
looks like by 17-18z ish, we do realize a few hundred J/KG of CAPE,
coupled with bulk shear values of 50-60kts and low level shear of
20-30kts. The deep layer lift will be more than sufficient so the
only thing that is questionable is the instability and moisture. We
are only forecasting dew points around 60-63 and temps around 70,
and if we get cut off by gulf convection, both of these could be
even lower. The surface based CAPE mentioned above is based on high
temperatures getting to a least 70 so that could be an uncertainty
point. Model reflectivity is consistent in showing a QLCS/line of
storms strengthening as it reaches Huntsville around 17-18z. So I do
think there`s a window of 18-22z where a few severe storms could
occur with damaging wind gusts being the highest threat.
The bulk of the rain/pre-frontal trough should be out by 12z at the
latest in NE AL and the front will be starting to get through NW AL
by 6-9z, shifting winds to the NW. There will probably be a few
showers accompanying the front as it moves across the area.
Guidance is trying to clear out the clouds fairly quickly on Friday
but this forecast package did push that back a little to be slightly
more pessimistic. The front itself may not even get through
Huntsville until 12-15z and there is lingering low level moisture and
light showers with it. Soundings are showing drying and subsidence
at the mid levels on Friday which creates a low level inversion,
trapping the low level moisture. So by the end of the afternoon there
will likely be some sun but don`t expect a fully sunny day!
In terms of temps, Thursday highs will be in the upper 60s near 70
and cooler highs on Friday behind the front, only around 60. Lows
Thursday night will be around 50.
.LONG TERM...(Friday night through Tuesday)
Issued at 232 PM CDT Wed Mar 28 2018
Friday Night through Saturday Night will be quiet and dry with high
pressure, a departing trough, and fairly seasonable temperatures.
After what might be a frosty start Saturday morning (given good
radiational cooling, temps in the mid-upper 30s, and a small dewpoint
depression), Saturday looks like a pretty nice day with highs
rebounding to near 70 and mostly sunny conditions.
The forecast goes downhill from Sunday onward due to a low-
predictability pattern, despite solid agreement among medium-range
models & ensembles. A weak front (and associated showers) will push
into the area Sunday and stall out/wash out as it begins paralleling
the mid /upper-level flow. Another mid-level shortwave will make a
run at driving the front through early Monday with little success.
None of these days look like a washout, but there is little
confidence in dry days either. Middle-of-the-road chance PoPs
(30-50%) are reasonable, focused for now on Sunday and Monday, though
this could change. Temperatures through this time period will likely
be depressed by clouds and scattered showers, though ensemble
mean/blended guidance is preferred since the position of the front
will dictate how cool (or warm) things get.
Models agree well on a broader, deeper trough pushing into the
eastern CONUS for Days 6-7, but diverge in the details. As is
typical, the GFS is a fast and dry outlier whereas the ECMWF and CMC
are slower and wetter. Blended guidance splits the difference and
this works for such a far-ranging time period. Again, temperatures
will depend on the speed of the front, so it is hard to deviate much
from blends.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 618 PM CDT Wed Mar 28 2018
VFR conditions this evening will gradually give way to MVFR to IFR
conditions overnight as a cold front and associated showers and
storms slowly track toward the region. Have added prevailing TSRA at
KMSL from 04-08z to account for better confidence of thunder there,
but have left it out of KHSV. The actual cold front will move
through the region tomorrow. Ahead of the boundary, gusty SW winds will
prevail, before switching to the NW in wake of the front.
Additionally, a second line of showers and isolated storms will move
through the region during the afternoon, so have maintained a mention
of VCTS. Late in the period, precip will taper off, but low ceilings
will remain in place through Thursday evening.
&&
.HUN WATCHES/WARNINGS/ADVISORIES...
AL...Flood Watch through Thursday evening for ALZ001>003.
TN...NONE.
&&
$$
NEAR TERM...AMP.24
SHORT TERM...LN
LONG TERM...BCC
AVIATION...AMP.24
For more information please visit our website
at weather.gov/huntsville.
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1104 PM EDT Wed Mar 28 2018
.UPDATE...
Issued at 1104 PM EDT WED MAR 28 2018
The relative lull in shower activity is starting to relent in the
northern half of the area. There appears to be a mesoscale
boundary aligned from approximately Paintsville to Mount Vernon,
as scattered showers have been forming along this fairly distinct
line over the past hour. On the SPC mesoanalysis page, there is
some subtle convergence at 925 mb. Meanwhile, further south, a
convective line is currently moving east across TN/MS. The HRRR
has been suggesting some of this activity making it into our area
overnight, with some of this focusing somewhere near the
aforementioned boundary, with much of the Bluegrass areas getting
more cutoff from the better moisture. The 00z NAM continues to
shift the heavier QPF further northwest with time, although it
does show more modest QPF further southeast compared to the 18z
run. Given that the HRRR has been fairly consistent with the
convective trends, have allowed for a strip of three quarters to
an inch of QPF along the boundary, with still around a half inch
or so across the Bluegrass counties. All of this will fall within
the Flood Watch area, so updates planned for the headline. Have
also included some patchy dense fog through the overnight, as
there have been some reports of this in places. Updates have been
sent.
UPDATE Issued at 806 PM EDT WED MAR 28 2018
Moderate showers have diminished to light showers through early
this evening, as forcing gradually relaxes across the area. The
higher rainfall amounts occurred along a corridor from
Salyersville to Mount Vernon, where an inch to an inch and a
quarter fell. The 18z model suite as well as some of the shorter
term model guidance has shifted the better QPF coming in late
tonight and into Thursday a bit more northwest. The HRRR has been
fluctuating between further northwest and right across the
southeastern portion of the watch area. For now, have only made
some POP adjustments, mainly to allow for more of a lull in the
activity until after midnight. Will continue to monitor model
trends and reassess things in a few hours. Also freshened up the
hourly temperatures and dew points through the rest of the
evening, with readings remaining in the 50s and 60s, closer to
normal highs for this time of year.
&&
.SHORT TERM...(This evening through Thursday night)
Issued at 304 PM EDT WED MAR 28 2018
We will maintain the flood watch in its current configuration,
with the watch beginning this evening at 8 PM and running through
8 AM Friday morning. Latest event total QPF forecast, including
some QPE from today`s rain generally has 1.5 to 3 inches of rain
in the flood watch through 8 AM Friday, with generally 0.5 to 1.5
inches outside the flood watch area. The total rainfall forecast
for the flood watch area remains very similar to the previous
forecast amounts.
Current satellite and radar imagery shows the wave that brought
today`s rain exiting off to the northeast. The next wave to
affect the area will emerge from the lower MS valley this evening,
with rain ramping back up later tonight. Another lull in the rain
looks to be in store Thursday morning into the afternoon before
the final round of showers and possible thunderstorms occurs from
Thursday afternoon into Thursday night. At the surface a
stationary front remains draped from northern AR to western KY
into western PA. As the last mid level wave in a series of waves
moves northeast on Thursday, the final wave of surface low
pressure will move northeast as well, and into western PA
Thursday evening. This will result in the surface front moving
east across our area as a cold front Thursday night.
Some of the high resolution models such as the HRRR had a good
handle on the rain that occurred today and have followed the HRRR
idea with rain chances diminishing late this afternoon and then
ramping back up from the southwest after 02Z this evening. The
axis of heaviest rain tonight should be over the far west and
northwestern part of the forecast area. Rain from Friday afternoon
into the Friday night should mainly occur in a band with the
approaching cold front, but with shower and thunderstorm activity
likely diminishing as it moves east Friday night, so that rainfall
amounts in the east end up being less than the rainfall amounts
in the west for the Thursday into Thursday night.
.LONG TERM...(Friday through Wednesday)
Issued at 357 PM EDT WED MAR 28 2018
An active weather pattern will continue through the long term
portion of the forecast with several frontal passages and waves
of low pressure bringing repeated rounds of precipitation. As a
result precipitation will be in the forecast just about every day
of the forecast.
After the cold frontal passage Thursday night, cooler air will
spread into the area for the end of the week. Surface high
pressure will slide across the area Friday night, and with mostly
clear skies and light winds, temperatures will fall into the
middle 30s, with frost possible. This was already highlighted in
the HWO and we will continue to highlight the frost threat for
Friday night into Saturday morning. With high pressure slipping to
our east by Saturday morning, and a cold front approaching from
the northwest Saturday afternoon a nice warm up will occur, with
highs Saturday in the 60s. However the cold front will move across
the area on Saturday night with another round of showers, and
then much cooler weather for Easter Sunday.
A mid level wave will move across the OH and TN valleys Sunday
night. The ECMWF is much colder than the GFS across our forecast
area, with the GFS having 850mb temperatures from 6 in the south
to -1 in the north by 12Z Monday, and the ECMWF having 850
temperatures from -1 in the south to -6 in the north at the same
time. It is possible that some snow may mix with rain or even
change to all snow in some spots late Sunday night into Monday
morning. At this time no impacts are expected and will not mention
in the HWO. Another cold front looks to move across the area
Tuesday night with more rain chances and then another mid level
wave keeping rain chances in the area into mid week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
ISSUED AT 806 PM EDT WED MAR 28 2018
Low pressure will ride up along a stationary frontal boundary
positioned just northwest of the area late tonight and into
Thursday. This will bring an additional round of widespread
showers to most locations along and northwest of a line from JKL
to SME, with MVFR/IFR conditions prevailing for most of the
period, especially after 06z. Mainly VFR conditions will hold on
across far southeastern Kentucky through most of the period,
besides during periods of passing showers. An increasing low
level jet moving in from the Tennessee valley will provide a
threat of low level wind shear across eastern Kentucky generally
between 08 and 14z. Southwest winds will average around 5 kts
through the mid- morning hours on Thursday, before increasing to
around 10 kts, with gusts of 15 to 20 kts. A cold front will
approach the area towards the end of the period, with perhaps a
few thunderstorms to contend with at times.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Friday morning for KYZ044-050>052-058>060-
068-069-079-080-083-104-106>109-111-112-114.
&&
$$
UPDATE...GEOGERIAN
SHORT TERM...SBH
LONG TERM...SBH
AVIATION...GEOGERIAN
Area Forecast Discussion
National Weather Service Norman OK
927 PM CDT Wed Mar 28 2018
.UPDATE...
Lift from approaching wave and some increase in isentropic lift
have resulted in development of scattered showers and
thunderstorms across the Texas panhandle into far western Oklahom
and western north Texas this evening. Have increased precip
chances through the night time period based on this as well as
agreement in last several runs of HRRR and 00Z NAM. Expect to see
this activity continue to increase in areal extent as it moves
east into the area. Still do not anticipate any severe weather,
but a few strong storms may occur.
&&
.PREV DISCUSSION... /issued 652 PM CDT Wed Mar 28 2018/
DISCUSSION...
Please see the 00Z aviation discussion below.
AVIATION...
Flight conditions will deteriorate quickly tonight as very low
cigs and FG/BR develop. Expect at least IFR to apply over most
terminals for 3-5 hours tonight. Thunderstorms will also develop
over WWR around 03Z and move southeastward close to OKC/OUN during
the early morning hours. A wind shift from the north will result
in some improvement to flight conditions after 12-14Z for most
terminals, but still expect MVFR to IFR cigs through most of
Thursday.
&&
.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK 47 58 39 67 / 60 20 10 0
Hobart OK 46 61 37 69 / 30 20 10 0
Wichita Falls TX 47 62 41 70 / 20 20 10 0
Gage OK 41 58 36 68 / 40 20 10 0
Ponca City OK 46 57 35 66 / 40 20 10 0
Durant OK 51 68 44 70 / 30 20 10 0
&&
.OUN WATCHES/WARNINGS/ADVISORIES...
OK...None.
TX...None.
&&
$$
30/03