Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/30/20
AREA FORECAST DISCUSSION
National Weather Service Wakefield VA
951 PM EDT Wed Apr 29 2020
.SYNOPSIS...
A cold front will slowly move across the area Thursday, pushing
off the coast Thursday night. An upper trough settles across
the Middle Atlantic Friday. High pressure returns for the
weekend.
&&
.NEAR TERM /THROUGH THURSDAY/...
As of 950 PM EDT Wednesday...
Latest analysis reveals deepening low pressure over lower MI/IN
this evening. ~1000mb sfc low was analyzed over S MI at 00z,
with the associated sfc front extending S-SW, bisecting the Ohio
Valley and extending into middle TN and the west-central Gulf
coast. Remaining breezy through the overnight, as pressure
gradient tightens between high pressure offshore of the east
coast, and previously referenced low pressure over the Great
Lakes, with resultant SSE low-level flow ushering in more mild,
moist air across the region. Remaining mild and breezy
overnight with lows in the upper 50s across the west to mid 60s
in the southeast.
Overall, have made some minor timing changes per past few runs
of the HRRR and the 18z CAMs. Pre-frontal showers increase from
the west to the I-95 corridor late tonight after 09z/5 am EDT.
Heavier rain holds off until just after sunrise Thursday
morning.
Midwest upper low progresses toward the region Thursday, with
the strong differential PVA allowing the system to take on a
slight negative tilt through midday. This will serve to slow the
frontal passage slightly and keeps the cold front west of the
area thru 12Z, with the front then marching east across the area
Thu aftn before pushing offshore tomorrow evening. The heaviest
rain will be along and just ahead of the front. The entire area
will see a period of heavy rain and overall QPF will be between
1 to 2 inches. While timing is a bit more progressive with the
CAMs and incoming 00z NAM, there remains some concern that a
slow-moving front combined with the a deep Gulf of Mexico
moisture feed could support a prolonged period of moderate to
heavy rainfall producing flooding. In particular, concern is
greatest that precip field will expand in areal coverage late in
the day/Thu evening along the coast (E VA/eastern shore) as the
mid- level trough axis takes on a stronger negative tilt.
Latest ERO from WPC keeps much of the area in a Marginal Risk,
with a Slight Risk from the eastern shore up into the northeast,
with better dynamics and forcing farther north into the
northern Mid- Atlantic. Still, localized flooding and heavy rain
threat is a concern, and will maintain Flood Watch at this
time.
Regarding strong to severe storm potential...SPC has pushed the
MRGL svr risk farther north for Thursday, which is supported
some by a little higher SHERB. While minimal CAPE is
anticipated, owing to the timing and expansive cloud cover,
effective shear and SRH will be an issue...and appears to
portend to a conditional high shear/low CAPE (HSLC) event with
unidirectional winds and potential damaging winds being the main
threat, especially in light of the strong 65-75 kt LLJ nosing
in by morning. Will need to keep an eye to radar trends by late
morning into the aftn with the well-forced line of showers
pushing through the area. Outside of any low-topped convection,
synoptic winds will also be a factor, with breezy to downright
windy conditions to persist through the day. 25-35 mph gusts
inland, with gusts to 45 mph at the coast. Will be sure to note
this in the evening update to the HWO. Highs upr 60s- lwr 70s.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
As of 345 PM EDT Wednesday...
The front pushes off the coast Thu evening and as of now it
appears some short-lived clearing is possible Thu night, before
clouds push back in late into Friday morning as the upper low
pushes across.
The trailing deep upper level low crosses the area through
Friday, keeping skies mostly cloudy Friday with chc PoPs.
Giving the lapse rates and moisture might expect some graupel
(along with potentially some cool air funnels along the coast)
in convective showers Friday as core of cooler air pushes across
the region. Highs Friday in the low to mid 60s.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
As of 305 PM EDT Wednesday...
Forecast period begins with the warmest day of the next week on
Sunday. Compressional heating/WAA ahead of next front will bring a
warm, breezy day on Sunday with highs well into the 70s to low
80s, with some middle 80s possible over inland sections. Rain
chances ramp up late Sunday night out ahead of the next system,
as it moves out of the Great Lakes states into Monday morning.
Despite typical temporal discontinuities at this time range,
the 12z/29 GFS and ECMWF remain in decent agreement with
generally digging the northern stream upper trough down from
the Great Lakes/interior northeast across the northeast
coast/northern Mid- Atlantic Monday through Monday evening.
Though should also note that, once again, the overall timing
has slowed slightly, owing to the more amplified model
consensus. The associated cold front crosses the region Monday
morning, with gradual drying behind the system from west to east
Monday aftn/night. GFS still shows a weak warm front causing
light precip across the forecast area, but the deterministic
non-NCEP models (UKMet, CMC, ECMWF) as well as latest EC
ensembles are dry due to high pressure across the area and
subsidence behind the departing system. Will therefore keep
Tuesday dry, but bring PoPs back on Wednesday, as another spoke
of shortwave energy looks to push across and continue the
unsettled pattern.
For temps, expect generally seasonable values for this time of
year. After the warmer temperatures on Sunday, look to have
temps drop back to the low-mid 70s Mon-Wed behind the front.
&&
.AVIATION /01Z THURSDAY THROUGH MONDAY/...
As of 840 PM EDT Wednesday...
VFR conditions across area terminals expected through the
overnight period, with rapid deteriorating flying conditions
after 12z Thu. Winds remain gusty out of the S-SE through the
night, before increasing after sunrise Thu morning.
MVFR ceilings are expected from mid to late morning through Thu
aftn, with moderate to briefly heavy showers reaching the
terminals between 12-18z (RIC 13-14z...reaching coastal
terminals between 15z to 17z). Expect IFR/LCL LIFR CIGs during
periodic heavy rain between 14-17z at RIC, 16-20z at coastal
terminals. Gradually improving conditions expected after 21z at
RIC, and after 23z into the evening along the coast.
Other concern will be with LLWS. Have mentioned low-level wind
shear at all coastal terminals Thu/Thu aftn, as the low level
jet nudges into the area after sunrise Thu morning.
Outlook: Additional showers will be likely overnight Thu into
Friday and into the day on Friday, as a reinforcing cool front
and the parent upper low crosses the area. Drying out by Friday
aftn all terminals.
&&
.MARINE...
As of 800 PM EDT Wednesday...
SSE winds are mainly 15-25 kt with gusts up to 25-30 kt this
evening and will steadily increase into Thursday morning, as a
frontal boundary approaches from the west. Waves in the Bay will
build to 3-4 ft and seas build to 5-8 ft.
The SSE winds will be strongest during Thu right ahead of the
frontal boundary. Winds will be 20-25 kt with gusts 30 to 40 kt
Thu morning through Thu evening. Wind probs for Gale gusts have
increased to 60-90 percent on the coast esply, so have a Gale
Warning for the coastal waters and the mouth of the Ches Bay
during Thu. Waves in the bay will build to 4-5 ft, with 6 ft at
the mouth of the bay. Seas expected to build to 6-11 ft.
Cold front crosses the area waters Thu night into Fri morning.
Winds behind the front will become W/SW 5-15 kt. Gale warnings
will become SCAs again for Thu night into Sat morning, as
elevated seas will be slow to subside.
&&
.HYDROLOGY...
As of 800 PM EDT Wednesday...
Expect significant rises along the James/Appomattox and Chowan
river basins Thursday night into Sat due to the rainfall
runoff. Current forecasts already reflect these trends. James
River Westham gauge shows the potential of reaching minor flood
level by Friday evening.
&&
.TIDES/COASTAL FLOODING...
As of 800 PM EDT Wednesday...
Strong southerly flow ahead of an approaching cold front will
result in rising tidal anomalies on Thursday. Minor coastal
flooding will be possible during Thursday morning`s high tide
along the Chesapeake Bay side of the lower MD Eastern Shore and
also adjacent the Potomac River on the Northern Neck. Additional
minor tidal flooding may be possible in these same locations
with the Thursday evening high tide cycle. A Coastal Flood
Advisory has been issued for these areas.
&&
.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...Flood Watch from Thursday morning through Thursday evening for
MDZ021>025.
Coastal Flood Advisory from 5 AM to 10 AM EDT Thursday for
MDZ021>023.
NC...Flood Watch from Thursday morning through Thursday evening for
NCZ012>017-030>032-102.
VA...Flood Watch from 6 AM EDT Thursday through Thursday afternoon
for VAZ048-060>062-064>069-079-080-087-509>511-513>515.
Flood Watch from Thursday morning through Thursday evening for
VAZ075>078-081>086-088>090-092-093-095>100-512-516>525.
Coastal Flood Advisory from 5 AM to 10 AM EDT Thursday for
VAZ075-077.
MARINE...Small Craft Advisory until 7 AM EDT Thursday for ANZ634-650-
652-654-656-658.
Gale Warning from 7 AM to 7 PM EDT Thursday for ANZ634-654-656-
658.
Gale Warning from 7 AM to 10 PM EDT Thursday for ANZ650-652.
Small Craft Advisory until 6 PM EDT Thursday for ANZ635>638.
Small Craft Advisory until 7 PM EDT Thursday for ANZ630>633.
&&
$$
SYNOPSIS...MAM
NEAR TERM...MAM/JAO
SHORT TERM...JAO
LONG TERM...MAM
AVIATION...JAO
MARINE...CMF/JDM/TMG
HYDROLOGY...
TIDES/COASTAL FLOODING...
Area Forecast Discussion
National Weather Service State College PA
1131 PM EDT Wed Apr 29 2020
.SYNOPSIS...
Mainly dry and pleasant weather will continue for the rest of
today with a mix of mid level clouds and sunshine. A moderate
to heavy rainfall will begin late tonight and last through much
of Thursday. The heavy rain may result in urban/poor drainage,
small stream and river flooding. Showers will linger through
Friday before conditions dry out on Saturday. Expect near
seasonal temperatures for the first weekend of May before the
cooler temperature trend resumes next week.
&&
.NEAR TERM /THROUGH THURSDAY/...
11 PM update: Main north-south rain band still inching eastward
from a Pittsburgh to Clarksburg line. A few showers racing
north ahead of this have moved through the area. Short term high
res models move the main area of rain, with embedded lines of
heavy rain, through mainly the western half of the forecast
area through sunrise.
Previous discussion:
Descending, thermally indirect branch branch of a
115 kt upper jet encroaching on the region from the west will
continue to shield most of the region from rainfall through dusk
across the west, and midnight over the Susq Valley and points
east.
The rest of the day will feature a good amount of sunshine
through mainly thin mid and high clouds with a gusty
southeasterly breeze and temps ranging from 60-65F across the
northern and western mountains, to between 65-70F throughout
the Central and Southern Valleys.
A brief, light shower is possible from the mainly mid cloud deck
across the far east and far western portions of the CWA, but
any rain that does fall through the rest of the daylight hours
will barely wet the ground if that. Both HREF and latest RAP run
indicate basically nothing in the rain dept through 23Z, though
a band of showers forming over far eastern Ohio attm could edge
into our Western Mtns toward dusk.
Strong low pressure will track across southern MI tonight with
trailing cold front reaching the Appalachians by the end of the
period. Hires models show north-south oriented band of moderate
to locally heavy rain along/ahead of aforementioned cold front
moving into the western zones btwn 06-12Z Thu.
Lows will be mainly in the 50s tonight, thanks to a blanket of
thick stratus forming/advecting rapidly north into the region on
the wings of a 55-65 kt LLJ (+4-6 sigma anomaly-wise with
respect to its v-component). The lows will be 10 to 15 degrees
above normal tonight.
&&
.SHORT TERM /THURSDAY NIGHT/...
Deep southerly flow/LLJ with PWs 1-1.5 inches should trigger
locally heavy rains across the Laurel Highlands into the south-
central PA early Thursday.
Flood Watch is in effect for a stripe of counties along and just
to the SE of the Allegheny Front very late tonight through early
Thursday afternoon, and across the Susq Valley and points east
from 18Z Thur through 18Z Friday where 1.5 to localized 3.0
inch rainfall amounts are forecast.
Terrain enhancement shows up well in the hires model data given
strong southeast low level flow. Flooding risk comes in
multiple varieties from shorter- term urban/poor drainage areas
and smaller streams to longer duration mainstem rivers which
would likely not crest until later Friday..
The other twist to this event is that this deep moisture and
anticipated thick, multi-layer cloud cover within the PWAT and
LLJ axis will yield high 0-1 km and 0-3km shear/helicity but
relatively low cape across the Susq Valley and surrounding areas
Thu afternoon.
Any embedded low-topped TSRA that form Thursday could tap this
high shear and show some compact/elevated moderately strong
rotation.
A north/south ribbon of sfc based cape on the order of several
hundred J/kg could be just enough for a few cells to become
rooted in the near sfc layer and allow some of the stronger
winds within 2 kft of the sfc to be mixed down to the sfc in
warm/moist downdrafts.
The cold front will slow down as it moves across central into
eastern PA on Thursday. This is in response to deep mid level
trough digging southeast into the southern Mid-Atlantic states
with secondary low developing near the Delmarva.
Confidence remains high for heavy rain with relatively wet
antecedent conditions and modestly elevated streamflows both
contributing to overall elevated flood risk.
Heavy rain axis shifts eastward late Thursday night with rain
intensity trending lower. Showers now linger through Friday as
upper level trough/closed low rotates across PA. Will have to
wait until Saturday morning before drying things out.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Minor changes made as of mid evening.
Earlier discussion below.
Showers linger through Friday as upper level trough/closed low
rotates across PA. After a decrease in the showers Fri morning,
higher lapse rates develop in the unstable air from midday onward as
showers again become numerous across the region, and a rumble of
thunder not out of the question. The showers retreat to mainly the
NE portion of the CWA Fri night and lighter scattered showers may
persist there into Sat.
Exiting upper trough and weak ridge sliding through should result in
a lower chance of showers Saturday into midday Sunday with gradually
moderating temperatures. Sunday looks like the warmest day we`ve had
around here in a few weeks, as high temps creep just above seasonal
normals, reaching the mid 60s to lower 70s. But clouds thicken for
the afternoon with showers moving in late as weak trough slides
through.
Mon/Tue look generally dry and breezy with below normal temperatures.
The endless parade of shortwave troughs bring shower chances
through the 2nd half of next week while keeping temperatures
below normal.
&&
.AVIATION /04Z THURSDAY THROUGH MONDAY/...
As expected, CIGS starting to come down. Made some minor changes
to the TAFS as of 1130 PM.
Some rain across south central PA as of 1130 PM, but the heavier
rain across far western PA at the current time.
Early evening discussion below.
For the 00Z TAF package, I did slow down the rain and lower
CIGS some. While there is a few showers into the south central
areas now, CIGS quite high, will take a few hours to see more
in the way of widespread rainfall and lower conditions.
Gusty winds and heavy rain taper off from west to east later
on Thursday.
Earlier discussion below.
Dry conditions and VFR expected through the rest of the daylight
hours with a mainly bkn, mid-level cloud deck.
Steadier rain and deteriorating cigs and vsbys arrive tonight
and will continue through much of Thursday ahead of a slow
moving cold front with abundant, deep- layer moisture streaming
north into the state along and ahead of it.
Outlook...
Fri...Scattered showers/tempo vis reductions, esp NW Mtns.
Sat...No sig wx expected.
Sun...Scattered showers possible, especially later in the day.
Mon...Still a chance of showers.
&&
.HYDROLOGY...
1 to locally 3 inches of rain is forecast across central and
eastern PA Thursday-Thursday night. Significant rises are
expected with minor to moderate small stream and river flooding
is possible. Crest on larger mainstem rivers may not occur until
later Friday or even early Saturday based on ensemble river
forecasts. Antecedent conditions are relatively wet and
streamflows are modestly elevated. A flood watch has been issued
for much of the area.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
Flood Watch from Thursday afternoon through Friday afternoon
for PAZ028-037-041-042-046-049>053-056>059-063>066.
Flood Watch from 4 AM EDT Thursday through Thursday afternoon
for PAZ012-018-019-025>027-034>036-045.
&&
$$
SYNOPSIS...Lambert
NEAR TERM...Lambert/Tyburski
SHORT TERM...Lambert
LONG TERM...DeVoir/RXR
AVIATION...Lambert/Martin
HYDROLOGY...Lambert/Steinbugl
Area Forecast Discussion
National Weather Service Glasgow MT
839 PM MDT Wed Apr 29 2020
.DISCUSSION...
Evening update...
Main change to the previous forecast was to introduce POPs in the
morning in the western part of the CWA, with showers/storms
tracking eastward through the day per CAM guidance. Models are
hinting at a ridge-riding shortwave being the trigger tomorrow,
which is currently producing storms in eastern Oregon.
Of note in the RAP forecast soundings for tomorrow is the
inverted-Vs generally east of the Phillips/Valley County line
throughout the day into the early evening. Any convective showers
that develop, thunder-producing or not, would have the potential
to bring some gusty winds down to the surface. 850mb winds peak in
the early evening at around 30 kts. or so. With low RHs expected,
this should be watched for potential fire weather concerns.
97
Previous discussion...
An upper level ridge covering the entire western United States is
bringing plenty of sunny skies, dry weather, and temperatures in
the upper 70s and to lower 80s today and tomorrow. A round of
precipitation may arrive Thursday. Southwest flow along with a
surface low dipping into Eastern Montana Thursday will set the
region up for rain showers and possible isolated thunderstorms
through Friday morning. QPF totals around a few hundred in the
east to a third of an inch west. Any thunderstorm activity could
bring totals higher in isolated locations.
The ridge will attempt to build again at the end of the week,
leaving the majority of Montana under zonal flow Friday and weak
ridging on Saturday. Temperatures will be near 70. Midlevel winds,
lapse rates, and temperature advection are conducive for breezy
conditions Friday along with higher gusts. As new models arrive,
will need to consider Lake Wind and Fire Weather hazard concerns.
The next system to watch for is over the Eastern Pacific Ocean
that will bring an elongated trough of moisture into the area
beginning Sunday through Tuesday morning. There is some
uncertainty on the development and location of this low and will
need to be monitored. Storm total amounts range from a tenth to
half inch. High pressure is expected to return over the western US
by midweek next week. 86
&&
.AVIATION...
FLIGHT CAT: VFR
WINDS: light and variable tonight. Winds shift to the west and
northwest Thursday morning and stay W-NW around 10 kts. during the
day and into the evening
DISCUSSION: Cloud cover will increase this evening, with mostly
cloudy skies expected on Thursday. Ceilings are expected to remain
well above VFR criteria. Convective showers, and associated CBs,
are possible near TAF sites after 17z Thursday.
97
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
weather.gov/glasgow
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
700 PM CDT Wed Apr 29 2020
.SHORT TERM...(This evening through Thursday Night)
Issued at 244 PM CDT Wed Apr 29 2020
Wind speeds have been on a slow decline through the afternoon,
but will drop off pretty dramatically this evening with the loss
of diurnal heating and mixing. Winds will become light and
variable overnight as surface high pressure moves overhead.
Any lingering cumulus will also dissipate this evening, leaving
clear skies through the overnight hours. These clear skies along
with the light winds will set us up for a relatively cool night. I
nudged forecast low temperatures down a couple degrees to the mid to
upper 30s. This is definitely on the low end of guidance, but
recently we`ve "overachieved" on good radiational cooling nights. As
such, some low-lying areas could end up with patchy frost, but we
will hold off on issuing a Frost Advisory for now.
High pressure exits the area on Thursday as upper level ridging
amplifies over the western CONUS. This will bring a return of
southerly winds and will push high temperatures back into the mid
70s to low 80s. For a discussion on the fire weather threat, see
the fire weather section below.
A weak perturbation will move through the area Thursday night into
early Friday morning. This may lead to some light showers or
sprinkles, but most of the area will remain dry.
.LONG TERM...(Friday through Wednesday)
Issued at 244 PM CDT Wed Apr 29 2020
Friday will be the warmest day of the week, with highs still
expected to be in the mid 80s to low 90s.
Precipitation chances creep back into the forecast on Saturday as
the first shortwave trough approaches the area. The best chances
for rain and thunderstorms will be Saturday night, and at this
time it doesn`t look a significant severe threat for most of the
local area. Models generally keep the highest instability confined
to portions of Kansas.
It now appears that Sunday will remain mostly dry before the next
system arrives Monday and Monday night. Despite these multiple rain
chances through this period, model ensembles are generally only
outputting 0.50-1.00 inch of QPF through the 7 days. This will be
welcome given our relatively dry stretch we`ve been in, but it
might not be enough for some locations. After this system moves
through, overall drier and cooler weather is forecast to persist
into the middle of next week.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Friday)
Issued at 700 PM CDT Wed Apr 29 2020
VFR conditions forecast. Wind should continue to decrease this
evening as the low-level lapse rate lessens with loss of daytime
heating.
&&
.FIRE WEATHER...
Issued at 244 PM CDT Wed Apr 29 2020
Winds are trending down this afternoon, but will remain supportive
of critical fire weather criteria through sundown. Relative
humidities largely will remain in the 30 to 40 percent range, only
dipping to around 20 percent in the western extents of the current
RFW counties.
Tomorrow`s fire weather potential is a little more uncertain. Most
models have RH values lower than today, but winds will be more
questionable. Southerly winds will pick up during the day, but there
is some question to whether they actually get strong enough to
support a Red Flag Warning. The 15Z RAP and 12Z NAMnest are both
quite low with their gusts tomorrow afternoon, but the global models
are a bit stronger. Therefore, we will hold off on any fire
headlines for now. The midnight shift will be able to take
another look at the near-term models before making a decision.
Friday will be even warmer with lower RH values, but fortunately
the winds are forecast to remain below critical thresholds.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
SHORT TERM...Mangels
LONG TERM...Mangels
AVIATION...Heinlein
FIRE WEATHER...Mangels
Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
632 PM CDT Wed Apr 29 2020
.SHORT TERM...(This evening through Thursday night)
Issued at 300 PM CDT Wed Apr 29 2020
Warmed temperatures up for Thursday with 850 temps nearing 20 to
26 degrees celsius. There should be some good mixing by afternoon
allowing surface temperatures to warm into the mid 70s and 80s.
There may even be a possibility we could see some areas across
western Nebraska hit 90 degrees. If any place sees 90 degrees this
would be the first time since the end of September, regardless if
temperatures reach 90 or not this will be one of the warmest days
so far this year across western and southwest Nebraska.
Winds were another concern in the short term. Forecast soundings do
show winds aloft around 25 kts that would be able to mix down,
however there is a little concern in how much mixing will happen.
Confidence is low to medium with mixing potential across western
Nebraska, this area might see WAA and unidirectional winds up to the
mixing level which could hinder the potential mixing height, which
would lead to lower wind gust. Confidence is a little higher in wind
gust reaching close to 25 kts from near HWY 83 eastward, however min
RH is slightly higher in this area. This creates marginally
favorable conditions for critical fire weather concerns as RH values
will generally 18 percent and lower across much of western and
southwest Nebraska. Since there is still low confidence in the
winds, after collaboration with surrounding offices, a Fire Weather
Watch was issued and will continue to monitor conditions with next
forecast whether or not this would need to be upgraded.
.LONG TERM...(Friday through Wednesday)
Issued at 300 PM CDT Wed Apr 29 2020
Temperatures remain warm through the forecast period.
Friday will be another warm and dry day with only isolated
precipitation chances on Thursday night, conditions will continue
to remain favorable for fire weather concerns on Friday as well.
Friday night there is a chance for showers and maybe even a few
thunderstorms. The best chance looks to be across the northern
Sandhills and north central Nebraska with a little bit more
uncertainty across our southern CWA. Then going into the weekend
there are a lot of uncertainties with precipitation chances this
Saturday and Sunday. There are discrepancies in timing and
location with the models on convection Saturday night, Sunday and
Sunday night. Forecast confidence is medium in precipitation
chances Saturday night but forecast confidence is low for
precipitation chances on Sunday, one model brings in a disturbance
through the forecast area which may aid in shower and
thunderstorm development but at this time given the uncertainty
PoPs remain low.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 615 PM CDT Wed Apr 29 2020
VFR is expected throughout western and north central Nebraska
tonight through Thursday afternoon.
An upper level ridge of high pressure will continue to present generally
clear skies across the region. Some high clouds will drift through
the area. These clouds are associated with a storm system
affecting the West Coast.
&&
.FIRE WEATHER...
Issued at 630 PM CDT Wed Apr 29 2020
The late afternoon run of the HRRR and RAP models show a good size
swath of 20 percent or less RH spreading into the Fire Weather
Watch area Thursday afternoon and evening. The Watch has been
been upgraded to a Red Flag Warning and extended until 9 pm CDT or
8 pm MDT Thursday. 500m AGL winds increase to near 20kt which
supports sfc winds of 20 mph.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 9 PM CDT /8 PM MDT/ Thursday for NEZ204-
206-210-219.
&&
$$
SHORT TERM...Gomez
LONG TERM...Gomez
AVIATION...CDC
FIRE WEATHER...CDC
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1015 PM EDT Wed Apr 29 2020
.SYNOPSIS...
A warm front will make its way northward through the area into
this evening, as low pressure over the Great Lakes stretches a
strong cold front into the Ohio Valley. This front will cross
the area through Thursday evening. Weak high pressure will
build to our south heading into the weekend, with another cold
front approaching from the west Sunday night.
&&
.NEAR TERM /THROUGH THURSDAY/...
Very little of significance was changed headline wise for the
evening package. Main adjustment was an attempt to refine the
most likely time for heavier rain.
Otherwise, a warm front bisects central Maryland this evening.
The warm front will continue to lift to our north overnight.
Low pressure situated on the east side of Lake Michigan will
push a cold front into Ohio this evening, knocking on the
western fringes of our CWA after midnight. Ahead of the front,
we will see surging PWATs in the 1-1.5 inch range while
dewpoints approach 60 degrees. The wind field at the surface and
aloft will be increasing out of the south as the front nears
and the upper low/trough digs southeastward.
Rain will encroach on our far western zones around or shortly
after midnight, with moderate to heavy rain expected as it
slowly pushes eastward. A Flood Watch goes into effect for our
Blue Ridge westward zones starting at 4am, as the heaviest axis
of rain overnight will remain primarily over this area. While
instability will be limited, an embedded thunderstorm will be
possible given the digging trough and approaching upper jet.
Winds will be gusty overnight as southerly flow gets cranking,
with winds gusting 30 to 40 mph at times. Combined with
saturated soils, could see some instances of downed trees with
isolated power outages possible. The highest rainfall totals
through daybreak will fall along the higher terrain of the
Alleghenies and central VA Blue Ridge, with rainfall totals in
the 1 to 2 inch range, with locally higher amounts possible.
Flooding of low lying areas and small creeks/streams will be
possible through the overnight hours.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
The heavy rain will shift slowly eastward during the day on
Thursday, pushing east of the mountains during the morning
hours, favoring the I-95 corridor and eastward during the
midday and afternoon. A Flood Watch for our zones east of the
Blue Ridge goes into effect at 10am Thursday, as the heavy rain
marches eastward. Again, the potential for flooding will exist
across any low lying areas and small streams/creeks. With
instability still limited, the upper jet/low will be favorably
positioned to allow for the added lift and an enhancement in
rainfall rates, especially along and east of I-95. Rainfall
totals will range generally between 1 to 2 inches, with locally
higher amounts up to 3 inches possible. The highest totals are
expected to reside higher terrain of the Blue Ridge Mountains
and across northeast Maryland.
Do think the axis of heaviest rain starts to push east of the
Chesapeake Bay during the late afternoon and early evening
hours, with the front tracking right along with it. Any
flooding, particularly any river flooding, will persist
Thursday night into Friday. The upper low will dive into West
Virgina and western Virginia Thursday night, dropping down
toward the VA/NC border on Friday. This will maintain cloudy
conditions and continued shower chances, with cooler than
normal temperatures persisting. The upper trough finally kicks
east of the Delmarva Peninsula Friday night as drier conditions
prevail. Temperatures Thursday through Friday will run below
normal with the elevated rain chances and cloud cover, with
highs in the 60s, while lows remain mild in the 50s.
&&
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Low pressure over the mid-Atlantic Coast will deepen slightly
more Friday into Friday evening as reinforcing energy approaches
from the west. The combination of wrap-around and residual
moisture will feed this additional energy to spawn additional
rain showers across much of our region midday Friday into Friday
evening. Any additional warmth could aid in spawning a
thunderstorm or two due to differential heating. Temperatures
should be in the middle 60s for the most part.
As the low slowly pulls away from the East Coast, the rain
showers will lessen in coverage and intensity with high pressure
building in from the west later Friday night and Saturday. A
gusty northwest wind could also become a factor with the
interaction between the low pressure and the building high
pressure through midday Saturday.
As clouds fade behind sunshine Saturday afternoon, temperatures
will warm a couple of degrees compared to Friday. Skies will
become partly cloudy Saturday night and continue into the day on
Sunday.
While temperatures should become 5 to 7 degrees warmer Sunday
than Saturday due to increasing thicknesses, a light southwest
flow, and some sunshine, a few pop-up showers can`t be ruled
out midday Sunday and become more scattered Sunday afternoon
into Sunday night. Temperatures should top out in the middle
70s.
A cold front should slice through the region Sunday night that
will bring this added threat for rain showers. A thunderstorm
can`t be ruled out in the afternoon and early evening.
High pressure will build in behind the front Monday and Monday
night. A light and cool breeze could develop and bring our
temperatures downward a couple of degrees to start next week.
A low pressure system could impact the area Monday night and
Tuesday. At this time, models have this low tracking to our
south or at least across our southern areas. This would result
in a stratiform rainfall versus showers and thunder.
Temperatures perhaps topping out in the upper 50s to middle 60s.
&&
.AVIATION /02Z THURSDAY THROUGH MONDAY/...
A warm front has been lifting northward through the terminals
this evening as southeasterly winds gust up to 20 knots and VFR
conditions prevail.
Clouds will thicken and lower overnight, approaching MVFR
status after midnight as a strong cold front approaches to the
west. Winds will remain strong and gusty out of the south
through the overnight period as rain begins to spread eastward
through daybreak. Rain will be heavy at times tonight at
MRB/CHO. Southerly winds will gust up to 30 knots at times
tonight and into Thursday morning, with LLWS being a factor.
Moderate to heavy rain will continue Thursday morning and
afternoon with IFR conditions likely at all terminals. The front
will finally push to our east Thursday evening, allowing for
slowly improving conditions as we head into Friday, however MVFR
CIGs may linger with passing showers possible. Upper level
disturbance pushes to our east Friday night, resulting in a
return to VFR conditions.
MVFR conditions with rain showers Friday into Friday evening.
The IAD, DCA, BWI, and MTN terminals seem more likely than MRB
and CHO. Winds generally northwest around 10 knots, becoming
gusty to around 20 knots by Friday night. VFR conditions
overnight Friday through Saturday night. Winds diminishing
northwest to southwest 5 to 10 knots.
&&
.MARINE...
A warm front has been lifting northward through the waters this
evening, allowing southeasterly breezes to increase and become
gusty. As such, SCA conditions have emerged and persist through
Thursday evening as a strong cold front slowly crosses. Gusty
southerly winds will near gale force on Thursday, but
confidence in frequency and occurrence is low at this time.
Moderate to heavy rain at times Thursday afternoon and Thursday
night will result in reduced visibility over the waters as well.
Winds look to slacken behind the front late overnight Thursday
and into Friday, but as the low begins to rap up along the New
England coast, SCA gusts could return to the waters late Friday
and Friday night.
No marine headlines anticipated Saturday and Saturday night.
&&
.TIDES/COASTAL FLOODING...
Water levels have settled down to around a foot above normal.
Anomalies have not yet surged and at a glance it looks like the
next cycle will fall short, but given southerly flow, am mainly
maintaining course, keeping Advisories for Annapolis and
Baltimore and adding an Advisory for SW DC.
The big push comes Thursday and perhaps into Thursday night.
The range of possibilities has diminished from yesterday, but
there are still questions yet to answer. Forecast more closely
reflects higher CBOFS, which performs better in these
situations. Added a Coastal Flood Watch for DC. Again, the rest
is the same.
The next challenge will be how quickly the water recedes. Some
Watches may be a little long based on 12Z guidance, but that is
a detail that can settle out in the cycles ahead. There is also
a hint that there may be a either freshwater contribution at
Georgetown or the tide will be significant enough to bring minor
inundation that far north.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Flood Watch from Thursday morning through Thursday evening for
DCZ001.
Coastal Flood Watch from 8 AM EDT Thursday through Friday
morning for DCZ001.
Coastal Flood Advisory until 8 AM EDT Thursday for DCZ001.
MD...Flood Watch from 4 AM EDT Thursday through Thursday afternoon
for MDZ003-502.
Flood Watch from Thursday morning through Thursday evening for
MDZ004>006-011-013-014-016>018-503>508.
Coastal Flood Watch from 4 AM EDT Thursday through Friday
morning for MDZ017.
Coastal Flood Watch from Thursday morning through Thursday
evening for MDZ508.
Coastal Flood Watch from 4 AM EDT Thursday through late
Thursday night for MDZ014.
Coastal Flood Advisory until 4 AM EDT Thursday for MDZ014.
Coastal Flood Watch from 6 AM EDT Thursday through late
Thursday night for MDZ011.
Coastal Flood Advisory until 6 AM EDT Thursday for MDZ011.
VA...Flood Watch from 4 AM EDT Thursday through Thursday afternoon
for VAZ025>031-036>040-503-504-507-508.
Flood Watch from Thursday morning through Thursday evening for
VAZ050>057-501-502-505-506.
WV...Flood Watch from 4 AM EDT Thursday through Thursday afternoon
for WVZ050>053-055-502-504>506.
MARINE...Small Craft Advisory until midnight EDT Thursday night for
ANZ530>534-537>543.
Small Craft Advisory until 6 PM EDT Thursday for ANZ535-536.
&&
$$
SYNOPSIS...BKF/RCM
NEAR TERM...BKF/RCM
SHORT TERM...BKF
LONG TERM...HTS
AVIATION...BKF/HTS/RCM
MARINE...BKF/HTS/RCM
TIDES/COASTAL FLOODING...HTS/RCM
Area Forecast Discussion
National Weather Service Melbourne FL
920 PM EDT Wed Apr 29 2020
.DISCUSSION...
Current-Overnight/Thursday...All eyes turning toward the approaching
line of storms nearing the east central Gulf this evening. Latest
HRRR model speeding up timing with initial round approaching
Lake/Volusia counties near 2AM, then showing a weakening trend as
this first wave moves across the I-4 corridor ahead of sunrise.
There is some re-development past sunrise and into mid-morning as
showers/storms approach the Space Coast and through Osceola County.
Moving into late morning-early afternoon the Treasure Coast and
Okeechobee County should get in on the action. Any duration of
stronger storms for a particular area will last up to two hours.
Storms will be moving toward the east-northeast at 40 to 50 mph.
Storm impacts remain frequent lightning, strong to damaging winds of
40 to 60 mph, small to quarter-size hail, and torrential downpours
averaging around one-half inch, but locally could approach 1 to 2
inches if multiple rounds of precip are received. Cannot rule out an
isolated shower out ahead of the line. The Storms Prediction Center
(SPC) will monitor for a Weather Watch later overnight.
Otherwise, a mild night with lows well into the 60s to L70s. Mostly
clear skies this evening will gradually thicken as moisture
increases ahead of the approaching showers/storms. A cool front will
follow the precip and move through during the day on Thu. Clouds
will decrease later in the day into the evening behind the front.
Highs Thu in the U70s to around 80F north of I-4 with L-M80s
southward. SERLY winds this evening will veer to southerly
overnight, then SW/W during the day on Thu. The wind will increase
later in the morning and afternoon with breezy/gusty conditions
expected. Speeds approaching 15-20 mph sustained with frequent
higher gusts in the late morning/afternoon. A Lake Windy Advisory
may be necessary, but a mix of clouds/precip could distort the wind
field enough to keep the Advisory mention absent.
&&
.AVIATION...Expect increasing cloudiness through late evening and
overnight ahead of an approaching line of showers and storms. Latest
HRRR model has sped up this activity with arrival into the I-4
corridor past 2AM and perhaps Orlando Metro by 4AM continuing to
spread southeastward through the morning and early afternoon. SERLY
winds will veer southerly overnight, then SW/W during the day on
Thu. Wind speeds will increase during the late morning/afternoon
approaching 15-20 kts with frequent higher gusts at many terminal
sites. A cool front will move southward during the day behind the
last band of precip. MVFR CIGs/VSBYs with precip and ISOLD IFR.
Clouds will decrease from north to south by late day/early evening
Thu. Storm threats include lightning, gusty winds in excess of 35-45
kts, small hail, and torrential downpours.
&&
.MARINE...Overnight-Thu...Deteriorating marine conditions as the
pressure gradient tightens in advance of an approaching line of fast-
moving showers/storms (40-50kts) ahead of a cold front that will
move across the waters late in the day on Thu. Expect offshore
moving activity to push across the Volusia coast after 4AM and
possibly at the Cape ahead of daybreak should activity hold
together. Models suggest weakening of this first line with a
secondary development pushing off the Space Coast thru mid-morning
and points further south late morning-early afternoon. Storm threats
include cloud to water lightning, wind gusts in excess of 35-45 kts,
small hail, and torrential downpours.
A Small Craft Advisory exists for offshore waters north of Sebastian
Inlet (until 12Z/8AM Thu morning) and near shore Volusia waters
until 08Z/4AM -- will extend by two hours with evening update. Some
models are suggesting some stronger winds into Thu morning/early
afternoon and will allow next shift to explore any extension from
here. Seas will build to 5-7 ft over the Advisory area and will need
Cautionary Statements most everywhere else. Both winds/seas will be
on a slow decrease thru the day on Thu.
&&
.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...Small Craft Advisory from 4 PM this afternoon to 2 AM EDT
Thursday for Flagler Beach to Volusia-Brevard County Line 0-
20 nm.
Small Craft Advisory from 4 PM this afternoon to 8 AM EDT
Thursday for Flagler Beach to Volusia-Brevard County Line
20-60 nm-Volusia-Brevard County Line to Sebastian Inlet 20-
60 nm.
&&
$$
Sedlock/Volkmer/Watson