Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/28/18
Area Forecast Discussion
National Weather Service Boston/Norton MA
951 PM EDT Tue Mar 27 2018
.SYNOPSIS...
Very light and widely scattered showers may lead to light icing
mainly across W MA and W CT late tonight into early Wednesday morn.
Expect improving conditions through the day on Wednesday. Warmer
air moves north on Thursday, then a cold front sweeps across the
region Friday. Expect mild air and showers during this time. Another
cold front may bring another round of precipitation sometime early
next week.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
10 pm update...
Indications per progression of 0z upper air soundings W to E, low-
level dry air deeper E, further top down saturation W, and notably
surface high dewpoint depressions. Attendant suppressive environment,
anti- cyclonic flow, tough for observed precipitation per WSR-88D
to advance E. Dual-pol included, indications of mixed sleet and rain,
whether as freezing rain depends if its reaching the ground and if
temperatures are sub-freezing.
Isentropic shield progresses along 290-310K surfaces, pressed against
the cut-off low S of Nova Scotia, in-between sinking, drier air. Per
RAP model, watching moisture below H7 which should increase chances
of precip reaching the ground, especially sleet. Trends echoed with
chance PoPs. Greater outcomes after midnight and mainly W MA / W CT
as top down saturation proceeds slowly E against aforementioned
suppressive environment. Lift remains weak, outcomes light overall.
Presently, above freezing, but a diurnal cooling trend plus wet-bulbing
is expected lending to marginal sub-freezing temperatures, especially
over the deeper snow pack high terrain. Again, outcomes light given
circumstances noted above. Will keep the SPS through the morning
as a precaution.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
Wednesday...
Risk for precipitation ends as the moisture dissipates rather
rapidly through the day, likely thanks to the synoptic- scale
enhanced subsidence provided between the two systems mentioned
above. This should lead to some breaks in the clouds through the
day as well. The continuation of modest low- mid lvl WAA will
lead to H85 temps approaching +4C, with an isothermal layer down
to H92. Given this, mixing should allow temps to approach the
upper 40s across much of the region, with the likelihood of more
widespread low-mid 50s especially where the sun is observed.
Generally a pleasant day after a damp start.
Wednesday night...
Warm front will be approaching from the S, which will lead to a
combination of increasing moisture and resulting cloud cover
through the overnight hours. Not expecting any precip as the
overruning is very weak and the moisture is confined mainly well
above the sfc. However, the clouds will lead to a milder night
than recent nights with min temps likely only dropping into the
mid 30s to around 40 in most spots.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
Big Picture...
The weather over North America will be dominated by a closed upper
low over Hudson`s Bay and vicinity. This will direct several
shortwaves through the flow and up across the St Lawrence Valley or
Northern New England. The flow across us will be fast-moving,
leading to uncertainty in exactly timing the passage of individual
shortwaves.
The upper jet placement and storm track near or up the St Lawrence
Valley suggests a milder than normal late week for our area. Upper
heights are also above normal for this period. Heights quickly lower
to normal or a little below behind the Friday-Friday night
shortwaves, so expect temps cooling to around normal.
Model mass and thermal fields are in general agreement through
Saturday, then diverge early next week. Confidence is moderate-high
through Saturday, and low due to timing issues Sunday through
Tuesday.
Details...
Thursday to Saturday...
Weak high pressure overhead Thursday with stalled front over PA-NJ.
As the upper ridge shifts east of us and shortwaves approach through
the Great Lakes, we expect the westerly upper flow to turn from the
southwest. This will nudge the front north as a warm front. The warm
fropa should generate some light rain/showers Thursday, followed by
mild and humid air.
The surface low passes west of us Thursday night and north of us
Friday. This will swing a cold front through the region Friday.
Expect a chance of showers in the warm sector during this time,
tapering off Friday afternoon/evening. A 50-60 knot southwest low
level jet moves over the top during this time, with the potential
for surface wind gusts as high as 30-35 mph.
Surface high pressure moves over us Saturday and should bring dry
weather.
Warm advection in the warm sector Thursday will limit the depth of
mixing, but temps at 950 mb and 1000 mb show potential for max sfc
temps near 60 in the interior and 45-50 along the coast. If clouds
are thick and showers frequent, then 55 inland and 40-45 coast may
work better. We compromised, going a little higher than guidance but
lower than full potential. Friday will have a better chance of 60
degrees inland with 50s along the coast. Deep mixing Saturday in
cold advection, but temps aloft support max sfc temps in the 50s.
Sunday to Tuesday...
Less confidence in timing within this part of the forecast.
Consensus of the models would suggest a cold front moving through on
Sunday. The ECMWF stalls the front close enough to our south to
bring a trailing precip shield along the front and reaching to the
South Coast and Islands Sunday. The GGEM brings is slower with this
precip and brings it to all of Southern New England on Monday.
Another shortwave may affect us with showers Tuesday. Timing
questions of shortwaves in a fast flow, although it is a reasonable
scenario that one or two shortwaves could bring showers during this
period. We used a blend of model values.
&&
.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short Term /through Wednesday Night/...
Tonight...
VFR, lowering MVFR over W CT / W MA with -RA/-FZRA/-PL. Spotty.
Looking to remain dry with little to no ice accretion. Light
winds.
Wednesday into Wednesday night...
Spotty morning precipitation, then improving, CIGs lifting.
VFR. Winds becoming SW, increasing.
KBOS Terminal...High confidence in TAF.
KBDL Terminal...Spotty -SHRA/-PL towards Wednesday morning push.
May not be enough to wet runways. Little to no impacts. MVFR to
low-end MVFR CIGs after midnight into Wednesday morning possible.
Outlook /Wednesday Night through Sunday/...Moderate Confidence.
Thursday Night: MVFR/IFR conditions possible. Breezy. Chance
SHRA, patchy BR.
Friday: Mainly VFR, with local IFR possible. Windy with local
gusts to 30 kt. Chance SHRA.
Friday Night: VFR. Breezy. Slight chance SHRA.
Saturday: VFR. Breezy.
Saturday Night through Sunday: VFR. Breezy. Slight chance SHRA.
Sunday Night: VFR.
Monday: Breezy. Slight chance SHRA.
&&
.MARINE...
Short Term /through Wednesday/...
Through the overnight hours...High confidence.
Diminishing NE winds, likely dropping below Small Craft
thresholds by midnight as they shift to the S-SW. However, with
an offshore storm still churning south of Nova Scotia, swells
will continue to impact the waters with 9-11ft seas on the open
ocean. Small Craft Advisories will therefore continue, in spite
of the weakening winds.
Wednesday and Wednesday night...High confidence.
Winds become variable at times, but predominantly W-SW and
mainly below 15kt. Swells continue, with 10+ ft seas beginning
the day on Wed, gradually lowering through the overnight. Small
Craft Advisories linger due to these higher seas.
Outlook /Wednesday Night through Sunday/...Moderate Confidence.
Thursday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft. Slight chance of rain showers.
Friday: Winds less than 25 kt. Areas of rough seas. Chance of
rain showers.
Friday Night: Winds less than 25 kt. Areas of rough seas.
Slight chance of rain showers.
Saturday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Local rough seas.
Saturday Night: Winds less than 25 kt. Areas of rough seas.
Slight chance of rain showers.
Sunday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Areas of rough seas. Chance of rain showers.
Sunday Night: Winds less than 25 kt. Areas of seas approaching
5 ft.
Monday: Winds less than 25 kt. Slight chance of rain showers.
&&
.EQUIPMENT...
Due to our move to the new forecast office in Norton, MA, we
are still trying to resolve some communication issues. The
following NOAA Weather Radio transmitter is back on the air...
Somers, CT transmitter........WXJ41.....162.475 MHz
However, the following NOAA Weather Radio transmitters are not
yet on the air...
Johnston, RI transmitter......WXJ39.....162.400 MHz
Gloucester, MA transmitter....WNG574....162.425 MHz
Blue Hill, MA transmitter.....KHB35.....162.475 MHz
Hyannis, MA transmitter.......KEC73.....162.550 MHz
Paxton, MA transmitter........WXL93.....162.550 MHz
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 8 PM EDT Wednesday for ANZ232.
Small Craft Advisory until 2 PM EDT Wednesday for ANZ235-237.
Small Craft Advisory until 8 AM EDT Thursday for ANZ250-251.
Small Craft Advisory until 5 AM EDT Thursday for ANZ254-255.
Small Craft Advisory until midnight EDT Wednesday night for
ANZ256.
&&
$$
SYNOPSIS...WTB/Doody
NEAR TERM...WTB/Doody/Sipprell
SHORT TERM...Doody
LONG TERM...WTB
AVIATION...WTB/Doody/Sipprell
MARINE...WTB/Doody
EQUIPMENT...WFO BOX Staff
Area Forecast Discussion...UPDATED
National Weather Service Corpus Christi TX
1031 PM CDT Tue Mar 27 2018
.DISCUSSION...Convection continues to increase over the western
Brush Country along surface trough axis. MLCAPE is in the
1500-2000 J/kg over this region with effective bulk shear of 60
knots. Threat for severe will continue into the overnight hours.
Latest HRRR model depicts possible decreasing trend late tonight.
Forecast update for new Severe Thunderstorm Watch for Webb, La
Salle, and McMullen Counties until 08Z.
&&
.PREVIOUS DISCUSSION... /Issued 636 PM CDT Tue Mar 27 2018
by National Weather Service Houston/Galveston TX/
AVIATION...
Low level moisture will continue to stream into the region beneath
a capping inversion. MVFR ceilings are expected to develop shortly
after 00z and prevail for much of the night. A weak short wave
will bring showers and thunderstorms to the southern TAF sites
between midnight and 6 AM with a break in precipitation over the
eastern TAF sites. An upper level trough will bring additional
showers and storms Wednesday afternoon. Ceilings will likely
remain MVFR or may briefly mix out to low VFR cigs in the early
afternoon. 43
&&
.PRELIMINARY POINT TEMPS/POPS...
Corpus Christi 72 80 65 84 60 / 30 60 80 20 10
Victoria 70 81 62 82 54 / 40 70 80 20 10
Laredo 72 84 63 89 57 / 50 40 60 0 0
Alice 71 83 65 86 57 / 50 60 70 10 0
Rockport 72 77 67 79 62 / 30 60 80 20 10
Cotulla 69 83 59 87 56 / 50 60 40 0 0
Kingsville 73 82 65 85 58 / 30 60 80 20 10
Navy Corpus 72 77 68 80 63 / 20 50 80 30 10
&&
.CRP WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...Small Craft Advisory until 7 AM CDT Wednesday For the following
zones: Coastal waters from Baffin Bay to Port Aransas out
20 NM...Coastal waters from Port Aransas to Matagorda Ship
Channel out 20 NM.
Small Craft Advisory until 1 AM CDT Thursday For the following
zones: Waters from Baffin Bay to Port Aransas from 20 to 60
NM...Waters from Port Aransas to Matagorda Ship Channel
from 20 to 60 NM.
&&
$$
TMT/89...SHORT TERM
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
813 PM CDT Tue Mar 27 2018
.EVENING UPDATE...
Opted to issue a Flash Flood Watch for a locations east of the
Edwards escarpment for tonight and overnight. Throughout the evening,
continued increases in QPF production in the hi-res model suite have
been noted, specifically in the HRRR and TTU-WRF output. These
models have generally been performing well with ongoing convection
along a slow moving outflow boundary draped across the I-35 corridor.
Reasonable confidence has been placed on these models.
Each continues to indicate an enhancement of precip coverage over the
Del Burro mountains in Mexico and spreading northeast towards the
aforementioned outflow boundary. 00Z KDRT sounding is already showing
PWAT values of 1.36 inches with moistening mid levels and elevated
instability to go along with 50+ kts of 0-6 km bulk shear. As this
area of convection progresses eastward, PWATs should increase even
further. The outflow currently sluggishly pushing southeast is
expected to continue to slow and potentially stall just east of the
I-35 corridor, which could set the stage for additional surface based
lift.
Thus, the concern for some locations along and near the I-35
corridor reaching flash flood guidance values is increasing despite
the favorable antecedent conditions (lack of significant rainfall
lately). This is mostly a concern for the metro areas of San Antonio
and Austin that are more susceptible to 1-2 inch per hour rain
rates, however, localized flooding may occur farther east, especially
if the outflow indeed stalls.
&&
.PREV DISCUSSION... /ISSUED 716 PM CDT Tue Mar 27 2018/
AVIATION...
Tumultuous flying and airport operation forecast expected through
the overnight hours and into Wednesday as multiple rounds of showers
and thunderstorms look to impact all sites. KAUS/KSAT/KSSF will have
greater impacts as KDRT will miss the possible second round early
Wednesday morning. Light -SHRA is ongoing near KAUS/KSAT/KSSF as of
00Z. TSRA is expected to then develop over Mexico and spread
northeast from 05Z-12Z into the TAF sites. KDRT will be near or under
TSRA near 02Z-07Z. TSRA could be strong to severe at times along
with very heavy rainfall. Visibilities will be reduced to 2-4SM and
likely lower if strong storms are right over the airport. Turbulence
and around the stronger storms is to be expected. General low-end
MVFR and high-end IFR will occur but brief LIFR conditions will be
possible.
SHRA/TSRA should exit east of the TAF sites by 21Z Wednesday
afternoon as another round of storms develops in the Coastal Plains
and points heat towards KHOU/IAH and KVCT. VFR will return Wednesday
afternoon.
PREV DISCUSSION... /ISSUED 256 PM CDT Tue Mar 27 2018/
SHORT TERM (Tonight through Wednesday Night)...
Key Messages:
- Widespread showers and storms develop late tonight through
Wednesday morning.
- 1-2 inches of rainfall appears likely along the I-35 corridor
counties as well as points east that are north of I-10. Localized
pockets up to 4 inches are possible.
- Despite the likelihood of localized heavy rainfall, widespread
flash flooding is currently not expected given the recent dry
conditions. However isolated pockets of flooding can`t be ruled
out, especially in areas prone to more rapid runoff such as urban
areas.
- Some storms tonight and Wednesday could become severe, containing
large hail and damaging straight-line winds.
- Conditional risk of strong to severe storms near and east of I-35
Wednesday afternoon and evening.
Early convective outflow boundaries and cool pool to the north have
pushed the weak surface boundary southeast to just south of a Llano
Fredericksburg to Del Rio line. The boundary per HRRR will slow
southward movement through the afternoon and early evening. Aircraft
soundings at SAT and AUS continue to indicate cap between 800-700mb,
although weakening since late this morning. Isolated streamer showers
will continue beneath the weakening cap through the afternoon. Can`t
rule out an isolated storm or two through early evening near the
aforementioned surface boundary and across Central Texas.
Bigger concerns to the forecast come tonight into Wednesday morning.
Convection is forecast to rapidly develop upstream across the higher
terrain in northern Coahuila by early evening in response to height
falls ahead of a strong ejecting shortwave impulse. The showers and
storms should expand in coverage as they cross into the southwest
CWA between 02Z-04Z near what`s left of the aforementioned boundary.
Deep layer shear vectors parallel to the boundary should allow the
convection to organize into clusters on the cool side of the
boundary, which in turn will help push the boundary southeast. Models
indicate increased divergence aloft as 110 kt 300mb jet streak noses
into the region, and deep omega values spreading northeast through
the area, and the convection could expand significantly in coverage
overnight to the northeast, becoming widespread through portions of
the eastern Hill Country, I-35 corridor, and portions of the Winter
Garden and Brush Country regions.
Upwards of 1500-2000 J/Kg of MUCAPE could still be present in
portions of the warm sector coinciding with bulk shear values of
60-70 kts. This will support a risk of severe storms with large hail
and damaging straight-line winds tonight. We have included this
mention in the grids and zones.
PWATs are progged to climb to around 1.4-1.7 inches tonight, near
record values for this time of year. Could be some pockets of
training given the evolution of storms expected above. 1-2 inches of
rainfall average appear likely along the I-35 corridor counties and
east of I-35 and north of I-10. Localized pockets up to 4 inches are
possible through this region, and indicated by GFS, Canadian, and
Texas Tech 4 km WRF. We have added locally heavy rainfall into the
forecast grids and zones. Given the recent drought conditions and
difficulty pinpointing exactly where the heavier pockets fall, we
will hold off on a Flash Flood Watch at this time. Nevertheless, some
localized areas of flooding could occur, especially in urban areas.
The thunderstorm evolution during the day on Wednesday and into
Wednesday evening afternoon remains difficult to pin down. It will
be highly dependent on how progressive and widespread showers and
storms are in the morning that potentially stabilize the atmosphere.
The Texas Tech WRF, which is the most robust with overnight and
early morning convection, does stabilize things across the region
mid morning through early afternoon. An uptick in convective
development is noted near and east of I-35 late Wednesday afternoon
by most global models, than NAM12, and Texas Tech WRF as conditions
de-stabilize ahead of the cold front and main forcing in the base of
the trough swings through. Should storms re-develop late Wednesday
afternoon, can`t rule out some of these storms being strong to
severe, producing hail and damaging straight-line winds, given the
steep mid level lapse rates and strong bulk shear values.
Precipitation should end west to east overnight into Thursday
morning.
LONG TERM (Thursday through Tuesday)...
Drier air will shift into the region Thursday and Friday. A return
flow will setup Saturday and strengthen through the weekend, becoming
breezy at times and producing warmer temperatures and an eventual
return of clouds by Sunday. The ECMWF continues to indicate a
frontal passage Monday and disturbance aloft producing a chance for
precipitation. The GFS is farther north with the front but does show
a disturbance in the southwest flow aloft generating precipitation
over the region Monday, while the Canadian stalls the front over the
area. Confidence in the temperature and PoP forecast is currently
low at this time for Monday and will continue with 20 PoPs.
&&
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 65 74 57 81 53 / 100 90 40 - 0
Austin Bergstrom Intl Airport 65 76 56 81 51 / 100 90 40 - 0
New Braunfels Muni Airport 66 78 57 82 52 / 100 90 40 - 0
Burnet Muni Airport 61 71 51 77 48 / 90 70 20 0 0
Del Rio Intl Airport 63 84 53 86 54 / 70 20 - 0 0
Georgetown Muni Airport 61 72 53 79 50 / 100 90 40 0 0
Hondo Muni Airport 67 80 54 86 52 / 100 60 30 0 0
San Marcos Muni Airport 65 77 56 82 52 / 100 90 40 - 0
La Grange - Fayette Regional 69 78 59 81 54 / 90 90 70 10 0
San Antonio Intl Airport 68 78 59 83 53 / 100 90 40 0 0
Stinson Muni Airport 68 79 59 84 54 / 100 90 40 - 0
&&
.EWX WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through Wednesday evening for Bastrop-Bexar-
Blanco-Burnet-Caldwell-Comal-Fayette-Gonzales-Guadalupe-Hays-
Kendall-Lavaca-Lee-Travis-Williamson-Wilson.
&&
$$
Mesoscale/Aviation...Allen
Synoptic/Grids...TB3
Public Service/Data Collection...Treadway
Area Forecast Discussion
National Weather Service Grand Forks ND
956 PM CDT Tue Mar 27 2018
.UPDATE...
Issued at 956 PM CDT Tue Mar 27 2018
00Z NAM as well as the RAP and HRRR have been trending towards the
less impressive side with our precip tonight. Slowed down the
onset of precip and lowered POPs just a bit, as not all of the
radar returns seen to our west have been reaching the ground.
Temps have stayed fairly steady in the mid 30s, and road temps are
progged to stay near or even above freezing for much of the night.
Think that precip will be mostly rain, although a tiny bit of snow
or freezing rain mixing in is not out of the question. Amounts
look light and impacts minimal.
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 306 PM CDT Tue Mar 27 2018
Diffluent flow aloft is beginning to spread into western ND ahead
of an approaching shortwave trough. Temperatures over eastern
ND/NW MN have reached the low to mid 40s at some locations, whit
all of our CWA above freezing. WAA is shown to remain in place
through most of the night with wetbulb profiles remaining above
freezing through most of the period of peak lift/moisture
advection. Increasing low level winds and cloud cover will also
help keep above freezing surface temperatures in place. This sets
the stage for rain being the favored precip type. Best chance for
the surface layer to drop to freezing will be in our northwest
where stronger CAA spreads into the region first.
As CAA spreads further east Wednesday morning measurable
precipitation should be tapering off. I still can`t rule out a
rain/snow mix or pockets of freezing rain/sleet, but unless a
surface is at or below freezing or lower impacts may be low. This
seems unlikely after the amount of warming observed today. Windy
conditions are expected during the day Monday with stronger CAA
and daytime temperatures may hold steady or even fall a little
through the day. Any lingering measurable or non measurable precip
should end by midday as subsidence/drying overspreads our CWA
from the west.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 304 PM CDT Tue Mar 27 2018
Quiet weather to start this period before a cold front moves across
the Northern Plains Thursday evening into Friday. This will bring
colder temperatures, higher winds, and light snow. The colder
weather will be here to stay into at least early next week. Below
normal temperatures with highs in the upper twenties to low thirties
and lows into the single digits are expected.
The next chance for precipitation will arrive Friday evening into
Saturday. There is still a high amount of uncertainty with this
system as model guidance still varies significantly. The ECMWF is
developing a shortwave while the GFS keeps northwesterly flow aloft.
At the surface the ECMWF has a well developed low move across the
Northern Plains while the GFS keeps much of the precipitation to the
south as it does not develop a similar surface low. The NAM is more
similar to the ECMWF and the CMC is somewhere between the GFS and
ECMWF. Future runs will be needed to increase confidence.
After the system on Saturday passes we will enter a quieter period
with a chance for some light snow Monday. The main story Sunday to
Tuesday will be the below normal temperatures with apparent
temperature in the single digits above and below zero overnight.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 704 PM CDT Tue Mar 27 2018
VFR conditions throughout the forecast area with increasing high
and mid level clouds. Southwest winds at 40kts at the 925mb level
could bring some LLWS to portions of the forecast area later
tonight, so included a mention for all but KDVL. Rain moving into
the area will be mostly near the Canadian border, but included a
TEMPO group mention at KDVL and KGFK. Stratus will move in behind
the precipitation with a cold front, dropping ceilings to the MVFR
category. Winds will increase out of the southwest ahead of the
front to the 15 to 25 kt range, and even stronger out of the
northwest by early morning, with gusts above 25 kts possible. MVFR
conditions and breezy northwest winds will continue for much of
the day tomorrow with some slight improvements by the end of the
period.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
&&
$$
UPDATE...JR
SHORT TERM...DJR
LONG TERM...NC
AVIATION...JR
Area Forecast Discussion
National Weather Service Fort Worth TX
1008 PM CDT Tue Mar 27 2018
.UPDATE...
A deep upper trough digging through southern New Mexico continues
to set off round after round of convection across the Southern
Plains. A broad surface low is positioned across southwestern
Texas with a slow-moving front draped to the northwest toward
Abilene, Graham, and Ardmore, Oklahoma. A consolidated outflow
boundary from the previous several rounds of convection has surged
southward through the entire forecast area into Central Texas
which has stabilized the boundary layer while keeping surface
winds generally easterly. Elevated thunderstorms with a threat
for hail will still be possible as MUCAPE of up to 1000 J/kg
remains in place across some of our southern counties.
The main concern continues to be the potential for heavy rain and
some flooding concerns, especially across our southern and eastern
zones. The next round of widespread heavy rain will be taking
shape over the next ~6 hours, and the greatest flooding risk
generally lies south of I-20 and along/east of I-35. Lift should
be enhanced by the front as it finally sinks southward toward
Central Texas by daybreak. Rainfall totals could reach as high as
3-5" (in very localized areas) in a short amount of time
overnight, and a Flash Flood Watch remains in effect though
tomorrow. With this update, have only trimmed a few of the
western/northern counties from the Watch as rainfall is expected
to be lighter and less widespread in these areas through the
remainder of the event.
Products for this update have already been sent.
-Stalley
&&
.AVIATION... /Issued 708 PM CDT Tue Mar 27 2018/
/00z TAFs/
Waves of showers and isolated thunderstorms will continue to
affect TAF sites through this evening and overnight. Convective
activity will be due to lift from numerous shortwaves pivoting
through the deep upper trough centered over AZ/NM, along with
aided ascent from a slow-moving frontal boundary currently located
through North Texas. In addition, an outflow boundary has surged
southward into Central Texas which is leading to isolated showers
and storms south and east of the Waco TAF site.
The trend over the past few hours has been for thunderstorms to
develop southwest of the DFW Metroplex in an area of slightly
higher elevated instability. As they move northeastward, they
encounter increasingly stable air and become predominantly showery
activity with a very limited TS potential. For this reason, have
not included TS in the Metroplex TAFs for this evening, but will
amend if trends suggest otherwise. In the meantime, cigs/vsbys
will vary drastically between VFR and IFR, with the poorest
conditions occurring within heavier rain showers.
There should be a relative lull in precipitation late this evening
and through part of the overnight hours, but widespread low
stratus should prevail throughout this time. Several hours of
IFR/MVFR cigs seem likely at all TAF sites. The slow-moving cold
front will also continue sinking southward, and light NE winds
will become more northerly. The combination of the front and
another impulse aloft should result in another large wave of
showers and thunderstorms affecting much of the area beginning
around midnight. The thunder potential will continue to be low in
the DFW area, but will keep some TS at Waco with more favorable
instability forecast to be present. Another lull in rainfall
should occur through midday Wednesday, but IFR/MVFR conditions are
expected to prevail at all airports through the entire day.
-Stalley
&&
.SHORT TERM... /Issued 347 PM CDT Tue Mar 27 2018/
/Through Tonight/
Scattered to numerous showers and thunderstorms continue across
North Texas this afternoon as a large upper low remains to the
west sending waves of ascent across the region. In addition, an
outflow boundary is surging southward through the region and is
now helping to ignite new convection across our southeast
counties. A cold front remains across the northern half of the
area, just south of the Red River. The front will actually slide
farther south tonight and be the main focus for additional
showers and thunderstorms through the overnight hours.
For the remainder of the afternoon and evening, the main area of
concern will be across the southeast counties where afternoon
heating has resulted in a narrow corridor of instability. A few
strong to marginally severe storms could develop through the
evening hours in this area.
Otherwise, as the front slides southward tonight, the upper low to
the west will edge closer. Stronger height falls will again
overspread North Texas with the right entrance region of a 130 kt
upper jet becoming positioned across the region. With the increase
in upper divergence associated with the jet and strengthening low
level convergence along the frontal boundary, we should see
reinvigorated convection late tonight from Central Texas into
northeast Texas. The potential for heavy rainfall and some
flooding issues will continue mainly along and east of I-35. We`ll
have high PoPs through the overnight across much of the area, but
precipitation should become concentrated along the frontal
boundary later tonight.
For now, we`ll leave the Flash Flood Watch intact but some western
counties may be trimmed later this evening.
Dunn
&&
.LONG TERM... /Issued 347 PM CDT Tue Mar 27 2018/
/Wednesday through next Monday/
The main highlight in the first part of the long term forecast
period will be the potential for rain and storms through Thursday.
Conditions should be drier and warmer for most locations late
Thursday at least through Saturday evening. A front will slide
southward through the area through the day on Sunday resulting in
the return of some rain chances and perhaps another round of
thunderstorms. Rain chances will linger thereafter into early next
week.
Wednesday and Thursday---Another batch of showers and
thunderstorms is expected to develop Tuesday night into Wednesday
morning across the Big Country and western North TX. This activity
should slowly push eastward, but the overall maintenance of this
convection is unknown. For now, given the moist environment and
broad troughing to the west, I`ll maintain some likely PoPs even
as far west as our Big Country and western Red River counties.
The more certain area for widespread showers and thunderstorms on
Wednesday morning will be across eastern and southeastern parts of
our area down across the Brazos River Valley. This area will
technically remain in the warm sector and so thunderstorms are
more probable here. With the front slowing due to the largely
parallel flow through a deep portion of the atmosphere, there will
be the potential for training of showers and thunderstorms,
especially east of I-35.
Given that a majority of the heavier rain activity will likely
remain to the east and southeast, we contemplated pulling the
Flash Flood Watch for parts of the area. For now, we will let the
evening/overnight shifts examine radar/satellite trends as well as
new hi-res guidance. before making any refinements. As it
pertains to the severe weather risk on Wednesday, some model
guidance advertises a fair amount of instability of around 1000
J/kg along with deep layer wind shear of around 50 knots. This
would be supportive of strong to possibly severe storms. While
these instability values are currently being suggested by RAP
guidance for this afternoon, outflow from this morning`s
convection may sweep southward and temper instability on Wednesday.
This outflow could further re-establish itself should any new
convection develop along the true front. If this occurs outflow
may be re-invigorated and surge southward which would likely halt
the northward progression of richer instability. If instability
does surge northward and storms can become surface-based, there
could be a window for a few strong to severe storms Wednesday
morning and early afternoon. I`ll keep high rain chances during
the afternoon hours as large scale ascent from an approaching
strong mid-level jet streak overspreads the area from the
southwest.
Rain chances will decrease some during the evening hours on
Wednesday as the true front finally slides eastward thanks to the
progression of the upper trough. I won`t completely clear our
area from the rain chances as the potent upper trough still
remains to the west of the area.
Conditions should be relatively drier on Thursday, but a potent
shortwave trough is advertised to translate to the east very
quickly near and just north of the Red River Valley.
Interestingly, there`s not a lot of guidance that actually
outputs precipitation with the exception being the latest NAM NEST
and ECMWF output. Given the vigor of the vorticity lobe and
likely large scale ascent, I wouldn`t be surprised to see some
showers or maybe even a rumble of thunder or two, mainly near and
north of I-20 on Thursday afternoon. If the column dries out very
quickly, it`s possible that only a high based cumuliform clouds
result, but for now, I`ll advertise a low chance for PoPs on
Thursday across North TX. The aformentioned upstream vorticity
lobe should be efficient and bringing down some cooler and
eventually less humid area on Thursday and I`ve nudged high
temperatures down by a few degrees. Most areas will likely remain
in the 60s to near 70 degrees. If NAM guidance is to verify, it
could be even cooler with highs in the 50s and 60s. At this time,
the NAM remains a colder outlier and for now, I`ll trend warmer.
It`ll also be a tad breezy on Thursday with northerly winds of 10
to 15 MPH.
Friday and Saturday---The start of the weekend appears largely
uneventful in terms of the sensible weather elements as northwest
flow aloft develops. It`ll turn warmer and breezier as well on
Friday and Saturday as surface winds increase to the 15 to 20 MPH
range and become more southerly. Afternoon high temperatures will
be above normal with temperatures in the 70s and 80s.
Sunday and beyond---Sunday presents the next challenge as model
guidance has become a bit more aggressive with the passage of a
cold front. The GFS model still appears to be the fastest guidance
and places the front across our western Red River counties as
early as 00 UTC Sunday (Saturday evening). The ECMWF and Canadian
are a tad slower with FROPA closer to 06 UTC Sunday. The big
difference between the two model camps, however, is that the GFS
quickly lifts the front to the north, while the Canadian and ECMWF
blast the front southward through the area. The zonal flow aloft
would support a stalling frontal boundary, but closer examinations
of surface pressure tendencies and forecast CPC temperature
anomalies would argue that there should be a decent push southward
with this front. I`ve trended cooler (towards the Canadian/ECMWF
guidance) and continued the mention of precipitation on Sunday.
At this time, I don`t think it`ll be a complete washout, but it`s
possible that there could be some impacts to Sunday morning
activities.
The weather pattern for Monday and beyond will likely remain
active as return flow re-establishes itself across the region.
Mostly zonal mid-level flow precludes any specific orientation of
PoPs and I`ve gone with some slight chance to chance broad-
brushed PoPs with near seasonal temperatures due to generally weak
forcing.
24
&&
.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth 54 65 52 69 49 / 70 70 30 20 10
Waco 59 66 52 75 47 / 100 90 20 5 10
Paris 55 64 52 67 43 / 80 80 40 20 10
Denton 53 63 49 68 42 / 60 70 30 20 10
McKinney 54 63 50 68 44 / 70 80 30 20 10
Dallas 56 63 53 70 49 / 70 80 30 10 10
Terrell 58 66 51 70 46 / 90 90 40 10 10
Corsicana 60 68 53 73 49 / 100 100 30 5 10
Temple 59 67 53 76 47 / 100 90 10 5 5
Mineral Wells 53 62 47 68 42 / 60 50 20 20 10
&&
.FWD WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through Wednesday evening for TXZ093>095-
103>107-118>123-133>135-144>148-157>162-174-175.
&&
$$
26/82
Area Forecast Discussion
National Weather Service Grand Rapids MI
1001 PM EDT Tue Mar 27 2018
LATEST UPDATE...
Update
.SYNOPSIS...
Issued at 311 PM EDT Tue Mar 27 2018
A cold front will push east of the region this evening taking the
rain with it. A break in the precipitation will occur on Wednesday
as a weak area of precipitation moves in. Another storm system
heads on our direction for Thursday. Rain will spread into the
area. Temperatures will fall on the backside of this departing
storm.
&&
.UPDATE...
Issued at 1001 PM EDT Tue Mar 27 2018
I have increased the cloud over overnight as our latest enhanced
night time image loops show low clouds building out into central
Lake Michigan as of 9:45 pm. The HRRR cloud forecast is matching
this best so that suggests the clouds will hold on most of the
night into the mid morning hours. This would decrease the chance
of dense fog but I still kept the fog in the forecast as winds
will be light and thus fog is still possible.
&&
.SHORT TERM...(This evening through Thursday night)
Issued at 311 PM EDT Tue Mar 27 2018
Clouds have remained relatively thick through the day while the
axis of rain has shifted east of the region. If we do see
extensive clearing...fog could become widespread. However...high
level clouds will move in as the lower clouds move out. Thus the
risk for widespread fog looks low at this time. Will maintain the
patchy fog wording in the forecast for now.
There is still considerable uncertainty with the next storm
system with regards to the timing...strength and type of
precipitation Thursday. The GFS would support falling temperatures
on Thursday with snow in the afternoon and evening...with the NAM
similar. The latest High Res Euro keeps this system as mainly a
rain event...with perhaps a brief period of mix towards the end on
Thursday night. The timing of the arrival of the colder air into
the system would have to be just right for this to end up as a
snow event...which looks like a low potential. Will continue to
feature a forecast closer to the Euro...more of a rain scenario. I
did lower temperatures on Thursday.
.LONG TERM...(Friday through Tuesday)
Issued at 311 PM EDT Tue Mar 27 2018
Next up is the storm potential for Saturday. Again there is
considerable uncertainty on this one. The GFS draws down a very
cold airmass from central Canada...as the storm system will be
pulling through. This would allow for steady accumulating snow on
Saturday. The High Res Euro shows little or no chance for this to
happen. I will blend the two scenarios. Low POPs Friday night
could be snow...then a rain event followed by a potential for some
mixed precipitation at the end for Saturday night. Will need to
monitor this one closely.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 718 PM EDT Tue Mar 27 2018
Dense fog is possible overnight into the early morning hours of
Wednesday. In fact as I write this AZO and BTL have just gone IFR
in fog. No matter happens tonight we should see enough dry air
come in so that all areas should improve to MVFR cigs by midday
Wednesday. If things go really well, we may even see mostly sunny
skies by afternoon.
The cold front has come through the area by late afternoon.
Normally that would bring in enough dry air to clear the skies.
However this time there is not all that much push behind the cold
front that came through. It is not entirely clear to me that the
low clouds will really clear. If they do not clear, then dense
fog is much less likely. If, on the other hand, they do clear out
by say, 06z or so, then even with the dense cirrus overcast
tonight we would likely have dense fog due to light winds an wet
ground from the 1/4 to 1/2 inch of rain that fell today. For now I
when conservative with the TAF forecasts but we will have to
watch this closely.
&&
.MARINE...
Issued at 311 PM EDT Tue Mar 27 2018
Overall the pressure gradient remains relatively weak through
Wednesday night...limiting impacts to mariners. On Thursday the
winds will be on the increase behind the departing wave of low
pressure. Small Craft Advisories may be needed then.
&&
.HYDROLOGY...
Issued at 311 PM EDT Tue Mar 27 2018
Rain amounts Monday night through 11AM Tuesday generally ranged
between 0.3 and 0.5 inches. While runoff from this rainfall will
cause a minor rise in river levels through the middle of the week,
flooding is not expected. Dry weather is expected tonight and
Wednesday. Low pressure tracking through the area will provide a
good chance for additional rain Thursday and Thursday night, with
amounts possibly reaching about a half-inch. This is also not
expected to cause flooding.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&
$$
UPDATE...WDM
SYNOPSIS...MJS
SHORT TERM...MJS
LONG TERM...MJS
AVIATION...WDM
HYDROLOGY...HLO
MARINE...MJS
Area Forecast Discussion
National Weather Service Houston/Galveston TX
859 PM CDT Tue Mar 27 2018
.DISCUSSION...
At 800 PM, a cold front extended from just north of Shreveport to
Centerville to north of San Antonio. A pre-frontal trough extended
just south of the front and this feature is helping to generate
scattered to numerous showers and thunderstorms over the northern
third of the region. Some of the short term guidance is bullish
with rainfall totals overnight and if the HRRR is correct, some
spots north of a Brenham to Trinity line could receive between 4
and 6 inches of rain overnight. Have expanded the FFA to include
Wharton and Colorado counties tonight and started the Watch at 03z
(1000 PM). WPC has expanded the moderate risk for flash flooding
into the CWA and slight risk for flash flooding now extends north
of a Columbus to New Waverly to Livingston line. GOES-R derived PW
values show PWATs near 1.80 inches over the the NW corner of SE
TX. 300 MB winds are broadly divergent over East Texas. 850 MB
moisture is is present with 850 mb Tds between 13-15 C. Moisture
flux convergence is targeting areas north of a Brenham to Trinity
line as well so all the ingredients are in place for a heavy rain
event tonight as storms train along the weak front tonight. Have
bumped PoPs up over the north and sped up the onset but the
previous forecast was on the right track. 43
&&
.PREV DISCUSSION... /ISSUED 701 PM CDT Tue Mar 27 2018/
AVIATION...
IFR/MVFR ceilings in place at all TAF sites for the 00Z package.
Radar imagery this evening shows a line of showers continuing to
move southeastward and will first impact CLL. VCTS should become
TSRA around 02Z at CLL, and the possibility for TSRA will hold
through the morning hours as the frontal boundary continues to
slowly move into SE TX with this first round of precip. UTS will
lag behind about an hour or two this evening, but should see
similar conditions. CXO is also dealing with RA which should
transition to VCSH through the overnight hours. Short term
guidance such as the Texas Tech WRF shows a short break in precip
for the northern TAF sites mid morning until the early afternoon,
and second round of thunderstorms will fill in around 19Z.
Expecting TSRA to continue through the TAF period for these sites.
IAH and southward begin to see showers associated with the first
round of precipitation by the early afternoon hours, transitioning
to TSRA around 20-21Z. This precip will also continue through the
TAF period for these southern sites. Have began to hint at the
arrival of the second round of TSRA for IAH in the early evening
hours.
Across all sites, expecting southeasterly winds to stay up around
10 kts this evening, until becoming more southerly tomorrow
morning. These southerly winds will increase in speed to around
15 kts tomorrow afternoon. Occasional gusts could be possible at
times underneath thunderstorms.
Hathaway
PREV DISCUSSION... /ISSUED 334 PM CDT Tue Mar 27 2018/
DISCUSSION...
.Heavy rainfall and strong to severe thunderstorms possible
early Wednesday morning through midnight...
In the short term warm southeasterly flow in place feeding into
the showers and thunderstorm that stretch from near Sanderson in a
broad swath through Stephenville to northern Arkansas.
Temperatures will remain above normal this evening with the WAA
and should start to see the band shifting east and southeast
throughout the night.
Rain chances ramp up quickly starting around midnight near College
Station and Crockett with scattered storms. As the s/w over Baja
rotates east then northeast around the upper trough axis expecting
to see a flare up in the overall coverage and intensity around 3
am moving into the College Station area and tracking eastward with
more storms developing all along the band. Sounding support
periods of heavy rainfall with the storms and 2"/hr rainfall
rates. SPC has the area highlighted with a slight risk of severe
and model soundings show a favorable profile mainly in the
afternoon Wednesday. The associated boundary is slow to move
through the region and Wednesday at noon the boundary will only be
getting close to College Station. This will keep the area in an
increasingly unstable atmosphere with deep layer shear and
abundant moisture. The primary mode of severe weather will
probably be hail and gusty winds winds across the north and closer
to the coast the threat of tornadoes increases especially in the 1
pm to 6 pm window Wednesday on the incoming nose of the 850
speedmax. SRH 1km 125-200/MUCAPE 1400-2700j/kg with the higher end
conditions closer to the coast. Some of the high res guidance also
indicating long lived supercell characteristics mainly along and
south of the I-69 corridor. At this point expect to see some
strong/severe thunderstorms lined up from Jackson county along the
69 corridor with greater instability focused toward the
Jackson/Matagorda area. The band should continue to shift slowly
southward and the heavy rain threat after 10 pm-midnight should
be tailing off along the 69 corridor and shift to the coast.
Widespread rainfall of 1-3 inches looks likely with narrow bands
of 4 to 5 inches. Have issued a Flash Flood Watch for the
northern areas beginning at 1 am and the southern areas at 7 am.
Pared off the southwest counties based on the drier SPoRT LIS data
and the recent lack of rainfall across those areas
(Colorado/Wharton/Matagorda/Jackson)...they will likely get heavy
rainfall but the threat for flash flooding should be lower there.
Looking at the Return Interval for the current suite of guidance
indicates we may be approaching 25 to 100 year return qpf for
this time of year.
Thursday by 7 am the deeper and stronger convection should be
mainly over the nearshore waters with residual showers still
possible across the area until the dry air filters in Thursday
afternoon.
High pressure builds south out of the Plains Friday and SETX
should have very pleasant weather Thursday night through Saturday.
The high moves eastward with light east winds Thursday and the
modified return flow from the Gulf impinging on the area Saturday
with a second cold front dropping south to move through the area
Monday/Monday night. Clouds should increase and may get some over-
running rain fall though the models aren`t in good agreement yet
and so for now have favored the ECMWF Monday and beyond in the
guidance.
45
MARINE...
Moderate onshore winds and elevated seas will prevail into
Wednesday. A small craft advisory remains in effect for the Gulf
waters. Conditions are borderline for the nearshore waters, but kept
the SCA going for the next couple of hours. Caution flags will be in
effect for the nearshore waters with a Small Craft Advisory
remaining in effect for the offshore waters through tomorrow
evening.
A high risk of rip currents continues for the rest of today and has
been extended into tomorrow as swells and higher surf will still be
around. A Beach Hazards Statement is in effect through tomorrow
evening.
Unsettled wx, with periods of showers and thunderstorms are expected
ahead of and along a weak frontal boundary that`ll be sagging toward
the coast Wednesday afternoon before pushing off the coast sometime
around early Thursday morning. A brief period of offshore winds can
be expected in the wake of the front, but they will become onshore
again late Thursday. 11
AVIATION...
Several small showers have erupted across the area this afternoon
from ARM to just south of CLL and UTS. These showers are quickly
moving north and not expected to produce much, if any, accumulation.
Have added VCSH to all TAFs from SGR/HOU northward for the rest of
the afternoon for these low impact showers. Have made no other
changes at this time to the rest of the forecast period.
Luchs
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 69 75 60 77 52 / 80 90 90 10 10
Houston (IAH) 70 80 66 81 56 / 40 90 90 30 10
Galveston (GLS) 71 76 68 75 63 / 30 40 90 60 0
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Flash Flood Watch through late Wednesday night for the following
zones: Austin...Brazos...Burleson...Colorado...Grimes...
Houston...Madison...Montgomery...Polk...San Jacinto...
Trinity...Walker...Waller...Washington.
Flash Flood Watch from 7 AM CDT Wednesday through Thursday
morning for the following zones: Brazoria...Chambers...Fort
Bend...Galveston...Harris...Liberty...Matagorda...Wharton.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION until 1 AM CDT Wednesday for
the following zones: Galveston Bay...Matagorda Bay.
SMALL CRAFT SHOULD EXERCISE CAUTION through late Wednesday night
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 1 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
National Weather Service Baltimore MD/Washington DC
912 PM EDT Tue Mar 27 2018
.SYNOPSIS...
A developing warm front will approach from southern West
Virginia overnight, then oscillate over the area through
Friday. Low pressure moving from the Ohio Valley to the eastern
Great Lakes will drag a cold front across the Mid-Atlantic
Friday. Canadian high pressure will return for the middle of the
weekend before another storm system approaches from the Great
Lakes by early next week.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
A warm front will move north and east toward our area overnight.
The warm front will likely remain draped across the Appalachians
into southern Virginia and North Carolina overnight. Our area
will remain on the cool side of the boundary, but a southerly
flow will allow for noticeably milder conditions compared to
recent nights. In fact, temperatures for most areas will remain
nearly steady and even rise along the ridges.
With the warm front approaching, anticipating overcast skies
with spotty light rain. Weak forcing will be north of the warm
front. This would place the best chance for intermittent/spotty
light rain over the Allegheny and Potomac Highlands toward
northern Maryland. Patchy light rain or drizzle is possible
elsewhere as well.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
Pretty much all model guidance is trying to lift the warm front
north to near the Potomac, perhaps even a touch further north on
Wednesday. I`m skeptical of this given the unseasonably strong
wedge of high pressure in place. Boundary layer winds may
increase to 10-15 kts by Wednesday afternoon which could aid the
front lifting northward some. To the south of the boundary,
temperatures should reach well into the 60s to near 70 with
breaks in the cloud cover. Meanwhile, it will be stuck in the
50s under overcast skies and spotty light rain north of the
warm front.
Any northward progress of the front should be halted by
Wednesday evening. A small disturbance riding along the front
will cause a batch of light rain to move west to east across the
region, reinforcing the warm front and possibly forcing it back
south a bit. Patchy fog is possible in the wake of evening light
rain overnight Wednesday.
Guidance has persistently been trending very warm for Thursday
(into the 70s). But low level winds remain rather weak until
late in the afternoon, making it seem a little unlikely the warm
front will push too far north. If the aforementioned perturbation
is a little stronger than currently forecast, subsidence in its
wake could result in some clearing/increased mixing through
Thursday morning, resulting in slightly stronger boundary layer
winds and aid in northward progress of the warm front. Model
guidance has high temperatures ranging anywhere from around 60
to close to 80 on Thursday. For now, stuck with SuperBlend and
took a middle of the road approach for highs.
Lift will increase ahead of an approaching upper trough/surface
cold front late Thursday night resulting in a re-generation of
showers. A rumble or two of thunder is possible given a little
elevated instability.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
An area of low pressure will pass off to the northwest of the
forecast area on Friday. It`s trailing cold front will work its way
across the area from west to east late Thursday Night through Friday
Morning. In association with that front, rain showers (possibly with
a couple rumbles of thunder) are likely for most locations Friday
morning. The bulk of the precipitation will end by early afternoon.
However, some lingering showers will still be possible in eastern
portions of the area, as well as west of the Allegheny Front where
some upslope precipitation could occur.
High pressure will build into the area from the southwest on
Saturday. Another cold front will slowly approach the area from the
west later in the weekend. Model guidance differs on the exact
timing of the front, but some precipitation will be possible out
ahead of the front in the Sunday through Monday time period.
Following the passage of this front, model guidance differs
significantly with the evolution of the pattern early next week,
casting uncertainty on the forecast for that time period.
&&
.AVIATION /01Z WEDNESDAY THROUGH SUNDAY/...
MVFR cigs have developed over the terminals this evening.
Forecast confidence is low for cigs/vsbys overnight given the
fact that the warm front is to our south but a southerly flow
may usher in drier air at the low-level just off the deck.
Did lean toward the LAMP and HRRR ensemble which shows IFR
conditions developing overnight across KBWI and KMTN where weak
isentropic lift will remain north of the warm front. However,
cigs may lift farther to the south and west overnight as the
low-level flow backs from the southeast to the southwest.
Looking upstream, VFR conditions are in place. However, patchy
fog may develop overnight most likely causing MVFR vsbys with
perhaps IFR across the northern terminals.
VFR should return briefly by late tomorrow morning as the warm
front slowly lifts north. Spotty light rain will be possible,
mainly near MRB during the first part of the day, then pressing
eastward during the afternoon.
MVFR/IFR possible tomorrow night, with VFR more likely Thursday.
More restrictions possible Thursday night as a cold front moves
in from the west.
Sub-VFR conditions will be possible on Friday as a cold front
moves through the area. Conditions will improve to VFR as high
pressure builds in Friday Night through Saturday. Sub-VFR
conditions will likely return Sunday as a slow moving cold
front approaches the area from the west.
&&
.MARINE...
Brief/marginal SCA conditions are possible in southerly
channeling this overnight. Left the SCA for lower MD Chesapeake
Bay/Tangier Sound waters for a few hours this evening.
Gradient/winds should remain light enough to preclude any marine
headlines Wednesday into Wednesday night. Southerly gradient
increases markedly late Thursday with SCA becoming more likely
during this time.
On Friday, winds will be near the SCA threshold, therefore an
advisory is possible. Winds will decrease Friday Night into
Saturday, and are expected to remain below the SCA criteria for
the remainder of the weekend.
&&
.TIDES/COASTAL FLOODING...
Tides will come close to minor thresholds at Annapolis/Straits
Point tonight, but this high tide cycle is the lower of the
two. Therefore, held off on headlines for now. Water levels will
remain elevated until a cold front crosses late in the week.
&&
.CLIMATE...
Dulles Airport had its 20th consecutive day with a low
temperature at or below freezing this morning. This is the
longest such streak this late in the season for this site, where
records began in 1960. Lows tonight will likely stay above
freezing, ending the streak at 20 days.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory from 1 AM to 4 AM EDT Wednesday for
ANZ534-543.
&&
$$
SYNOPSIS...BJL/DHOF
NEAR TERM...BJL/DHOF
SHORT TERM...DHOF
LONG TERM...IMR
AVIATION...BJL/IMR/DHOF
MARINE...BJL/IMR/DHOF
TIDES/COASTAL FLOODING...DFH/BJL
CLIMATE...DHOF
Area Forecast Discussion
National Weather Service Memphis TN
957 PM CDT Tue Mar 27 2018
.UPDATE...
Light to occasionally moderate rainfall has been a little slower
to develop east this evening, persisting mainly west of the MS
River.
Latest HRRR and RAP guidance depicted increased rain rates lifting
into the I-40 corridor from southern AR overnight, focused along
and north of a slow moving cold front and aided by a strengthening
low level jet. Regional radar mosaic showed this scenario may
getting underway.
Most recent forecast update included a slight delay in eastward
expansion of rain for the late evening, and reduction in rain
chances over northeast MS overnight.
PWB
&&
.PREV DISCUSSION... /issued 653 PM CDT Tue Mar 27 2018/
UPDATE...
Updated to include 00Z aviation discussion below.
PREV DISCUSSION... /issued 351 PM CDT Tue Mar 27 2018/
DISCUSSION...
A split flow pattern persists across the CONUS this afternoon. A
northern stream trough is moving east across the northern tier
states with a downstream ridge building up the East Coast. A
southern stream trough continues to spin over the Four Corners
area this afternoon with a cold front is located to our north,
extending across southeast MO into northeast TX. This boundary
will sag slowly south over the next 1-2 days, providing a focus
for widespread showers with occasional thunderstorms.
The warm conveyor belt downstream of the Four Corners trough will
shift eastward over the Mid-South tomorrow with precipitable
water increasing to around 1.75" along and ahead of the
aforementioned cold front. This is a good 2-3 standard deviations
above climatology and will set the stage for heavy rainfall over
the next 36 hours. The first wave of heavy rain is expected late
tonight into Wednesday morning and there may be a lull Wednesday
afternoon. However, another round of heavy rainfall is expected
Wednesday night before tapering off on Thursday and Thursday night
as drier air advects into the CWA.
In addition to the heavy rainfall potential, a few strong to
severe storms are possible tomorrow late afternoon and evening,
primarily south of I-40. Models are in better agreement today in
pulling the upper-level support and moisture east of the area
Thursday night. Thus, PoPs were removed for Friday. Temperatures
will be a bit cooler on Friday with highs in the low/mid 60s.
A brief dry period is anticipated area wide Friday and Friday
night in the wake of the departing trough, but light rain showers
are back in the forecast on Saturday across the northern portion
of the CWA. The synoptic pattern will be more quasi-zonal by this
time and a fast-moving shortwave trough is progged to be
approaching the Ohio Valley during the weekend. This will drive
another cold front south into the area Saturday night. This front
is then forecast to lift back north on Sunday and Sunday night as
the next trough approaches the region. Yet another trough is
progged to affect the area on Tuesday, bringing rain chances back
to the Mid-South through early Wednesday. Temperatures will be a
bit below normal Sunday through Tuesday, with highs generally in
the low/mid 60s and overnight lows in the 40s.
Johnson
&&
.AVIATION...
00Z TAF Set
Mainly VFR conds to start with developing IFR/LIFR conds later
tonight. A cold front is already through JBR at this hour, with a
windshift to the north being reported on site. This front is
expected to push through MEM in the 06-08Z timeframe, with a
significant windshift to the west and eventually north. The front
is expected to slow down and possibly stall just to the south of
MEM. This will create obstructed VSBYS, lowered CIGS, and push
flight rules into LIFR and possibly VLIFR along and north of the
boundary.
Confidence beyond about 12Z is low at this time, due to
considerable model differences on where the frontal boundary
stalls out. Decided to use a VCSH north of the front, as each
model depicts scattered activity beyond 14Z. To the south of the
boundary VCTS was placed at TUP, where greater instability will
exist.
AC3
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...Flood Watch from 1 AM CDT Wednesday through Thursday morning for
Clay-Craighead-Crittenden-Cross-Greene-Lawrence-Lee AR-
Mississippi-Phillips-Poinsett-Randolph-St. Francis.
MO...Flood Watch from 1 AM CDT Wednesday through Thursday morning for
Dunklin-Pemiscot.
MS...Flood Watch from 1 AM CDT Wednesday through Thursday morning for
DeSoto-Tunica.
Flood Watch from Wednesday afternoon through Thursday afternoon
for Alcorn-Benton MS-Calhoun-Chickasaw-Coahoma-Itawamba-
Lafayette-Lee MS-Marshall-Monroe-Panola-Pontotoc-Prentiss-
Quitman-Tallahatchie-Tate-Tippah-Tishomingo-Union-Yalobusha.
TN...Flood Watch from 1 AM CDT Wednesday through Thursday morning for
Benton TN-Carroll-Chester-Crockett-Decatur-Dyer-Fayette-
Gibson-Hardeman-Haywood-Henderson-Henry-Lake-Lauderdale-
Madison-Obion-Shelby-Tipton-Weakley.
Flood Watch from Wednesday afternoon through Thursday afternoon
for Hardin-McNairy.
&&
$$
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1033 PM CDT Tue Mar 27 2018
.SHORT TERM...(This afternoon through Wednesday)
Issued at 1156 AM CDT Tue Mar 27 2018
Surface analysis this afternoon shows high pressure centered over
the Central Plains, extending NE into MN/WI and SW into eastern
CO. One cold front is now well off to the east, into the Ohio
Valley and mid-Mississippi River Valley regions while a second
cold front lingers to the north over south-central Canada. The
high pressure area will be the prevailing feature through the
overnight hours as skies continue to clear out from eastern MN
into western WI this afternoon and remain mostly clear across the
entire coverage area for much of tonight. Conditions do look
conducive to producing some patchy fog, particularly over far
southern MN into southwestern WI, closer to the center of the
high. By daybreak, the aforementioned northern cold front will
drop through the Dakotas and into far northwestern MN. A spoke of
the main upper level trough originating in central Canada will
nudge a developing low pressure center just north of the
international border from southern Manitoba into southwestern
Ontario. The cold front of this system will quickly slide
southeast through much of MN and northwestern WI by late day. Not
much in the way of deep moisture will accompany the front as the
bulk of the moisture will be concentrated near the low pressure
center. Yet, enough frontal lift plus the pivoting of the upper
trough may produce some isolated light rain/snow showers across
much of the area tomorrow. Only about a hundredth or two of QPF is
expected with any shower. The main impact will be a minor surge
of warmer air in advance of this front for the area which will be
realized in the form of highs ranging from the lower 40s in
western MN, which will have the cold frontal passage first, to
highs in the lower 50s in far eastern MN into western WI. Because
of the clear skies tonight, lows will again drop to the upper 20s
to lower 30s.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 244 PM CDT Tue Mar 27 2018
Once the cold front of Wednesday drops through the region, this
will commence a period lasting through early next week of colder
than normal temperatures, including occasional chances for light
snow going into the start of April and lows into the teens.
Low level flow will become more predominantly west to northwest as
a series of fronts are expected to pass through the region, namely
Friday into Saturday then Monday into Tuesday. In conjunction with
these frontal passages, the prevailing upper level low rotating
generally over Hudson Bay will maintain a longwave trough over
eastern NOAM with northwest flow aloft. Within this flow, several
shortwave trough axes will aid in not only pushing the
aforementioned cold fronts through the region but also bringing
down chunks of arctic air, in a modified fashion, into the Upper
Midwest which will contribute to keeping below normal temperatures
in place.
With the first frontal passage, the best chances for
precipitation will come Friday morning through Saturday morning,
most of which will come as light snow though some light rain could
mix in. Not a lot of moisture is associated with this frontal
passage so will look for snow amounts in the 1-2 inch range for
much of the area, over this 24-36 hour period.
With the second frontal passage, the best chances for
precipitation will come Sunday into Monday. Again, moisture will
be relatively limited, so will not look for much in the way of
accumulation but the majority of this precipitation will come as
light snow (with some occasional mixing with light rain).
There are still some uncertainties to iron out due to the
transitional season nature of these systems and the strong
temperature gradients involved but the overall lack of deep
moisture gives the thinking that QPF and hence snow accumulations
will be on the lower side of the spectrum.
&&
.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1033 PM CDT Tue Mar 27 2018
Keeping an eye on the potential for fog tonight, with MKT/EAU
already dropping down to a 6sm vis. We look to keep a gradient and
wind in place through the night, so that should keep fog from
getting out of hand. Still think greatest potential for fog will
be over the snowpack that comes up out of IA into southwest and
south central MN, with MKT having the greatest potential for fog,
though EAU down by the river will have potential as well. FROPA
timing has not changed much from 00z TAFs. Maintained dry TAFs as
well, with nothing more than sprinkles expected. Also favor the
HRRR/RAP idea with MVFR cigs coming in behind the front, likely
down in the 2k-3k foot range, which is what we are seeing now up
in southern Alberta and Saskatchewan. The LAV continue to downplay
the post frontal cloud threat, but forecast soundings from the
GFS/NAM continue to support the post frontal cloud idea.
KMSP...Still a threat for some problematic cross winds in the
morning and upped winds a bit in the morning hours looking at the
HRRR and GFS forecast soundings for MSP. May get a sprinkle or two
with the fropa around 19z, but nothing more than that. Confidence
is high we will see MVFR cigs behind the front, coming in as early
as 20z. Less confidence on when they will dissipate, but could be
as early as 2z, or they could hang tight most of the night.
/OUTLOOK FOR KMSP/
THU...VFR. Wind NW 5-10 kts.
FRI...MVFR chc IFR. Chance mrng -RASN. Wind SW bcmg nw 5-10 kts.
SAT...Chance MVFR/-SN early. VFR by aftn. Wind NW 10-20 kts.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
&&
$$
SHORT TERM...JPC
LONG TERM...JPC
AVIATION...MPG