Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/06/17
Area Forecast Discussion
National Weather Service Wakefield VA
1200 AM EDT Sat May 6 2017
.SYNOPSIS...
A low pressure system will push a cold front across the region
through this evening. The system will then lift into New
England over the weekend. High pressure returns early to mid
next week.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Latest surface analysis places a cold front over eastern
Virginia as the parent low centers over central Pennsylvania.
Aloft, the anomalous upper trough continues to build into the
region with a pronounced dry slot visible on water vapor. Clouds
have even scattered out over the Piedmont late this evening.
Cannot rule out an isolated shower ahead of the front from the
Northern Neck to the Maryland Eastern Shore as RAP analysis
still indicates some instability and shear. Regardless, the
severe threat has diminished. The front pushes offshore shortly
after midnight, eliminating the chance for any precip as drier
and more stable air spreads over the region. Lows generally in
the mid 50`s.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/...
Turning out partly to mostly cloudy tonight but with dry
conditions. The upper-level low lifts NE along the spine of the
Appalachians tonight/Saturday morning before reorganizing over
the eastern Great Lakes late Saturday as additional energy
diving south from Canada further deepens it. The end result will
be the chance for additional instability showers on Saturday
and overall mostly cloudy/breezy conditions. Will carry 20-30%
pops across the N/NW in the morning, then 30-50% pops across
much of the area in the afternoon (highest NE). Lows tonight in
the 50s. Highs Saturday in the mid 60s to lwr 70s.
The upper-level low heads north into SE Canada Saturday
night/Sunday with additional spokes of energy rotating around
the base of the low. Timing/intensity of these features is tough
to judge but at this time cannot rule out at least lingering
low end pops (15-30%) during this time. Remaining partly to
mostly cloudy with below normal temps. Lows Saturday night from
the mid 40s to mid 50s. Highs Sunday in the mid 60s to around
70.
By Monday, sfc high pressure returns with dry NW flow
aloft behind the departing upper low over New England. Partly
sunny with highs in the 60s.
&&
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
Stacked low continues to spin over the NE CONUS with an
amplified ridge of high pressure over the cntrl U.S., and an
upper low sitting over the Intermountain West. Ridge over cntrl
U.S. is expected to break down (or deamplify) Tuesday night
through Wednesday night. As this occurs, the low over the
Intermountain West will begin to track ewd as the NE CONUS low
retrogrades and flattens out as upper level flow across the Mid
Atlantic becomes more WNW. This set-up will allow a potential
series of weather disturbances to pass across the area Wednesday
through the rest of the week (primarily the swrn half of the CWA
per 05/1200Z model runs). Conditions will remain unseasonably
cool throughout the long term periods. Lows generally in the
mid 40s to mid 50s Tue-Wed nights. Lows Thu night in the 50s.
Highs Wed-Fri in the upper 60s to lower 70s.
&&
.AVIATION /04Z SATURDAY THROUGH WEDNESDAY/...
As of 02z...Showers continued over the CWA early this evening and
were finally diminishing. IFR ceilings at SBY are expected to lift
after Midnight. Scattered showers are expected to redevelop Saturday
as an upper level low pressure system lifts over the area. No
significant impact to aviation is expected.
OUTLOOK...The chance for showers continue into Saturday night with
low chances into Sunday. Dry and VFR conditions are expected Sunday
night through Tuesday as high pressure builds over the region. The
next frontal system affects the area with a chance for showers
Wednesday.
&&
.MARINE...
No changes made to ongoing SCA flags or conditions expected
tonight into Saturday. Low pressure over the WV/MD panhandles
late this aftn will slowly track ENE into nrn NY state and then
more ewd along the St Lawrence River Valley on Saturday. Winds
are generally SE 15-20kt but will become more SSE 20-25kt as a
cold front crosses the waters. Behind the front, drier air
moving overhead will mix stronger winds over the waters and
SW 15-25kt should be anticipated this evening and Saturday. Seas
are currently 5-7ft and may briefly build to 8ft north of
Parramore Island with the drier air punching in. Waves 3-5ft in
the Bay. The wind will become WNW and average 10-15kt later
Saturday into Sunday. Low pressure lingers well NE of the area
into early next week as high pressure builds across the
Southeast States. High pressure over the cntrl U.S. begins to
break down Tuesday night into Wednesday, and the next weather
disturbance may cross the waters on Wednesday.
&&
.TIDES/COASTAL FLOODING...
Tide levels at Cambridge will peak near 3.4 ft and Bishops Head
peaked near 3.6 ft overnight with tide anomalies running
between 1.0-1.4ft above average. Still expect only nuisance
flooding with the high tide cycle at both sites. Water levels
remain elevated at bit into Sat with Cambridge/Bishops Head
potentially within 0.5 ft of minor flood thresholds. The wind
becomes westerly Sat night into Sun, which will allow tidal
anomalies to slowly diminish.
&&
.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...None.
NC...None.
VA...None.
MARINE...Small Craft Advisory until 6 PM EDT Saturday for ANZ630>638-
650-652-654-656-658.
&&
$$
SYNOPSIS...JDM
NEAR TERM...JDM/SAM
SHORT TERM...JDM/MAS
LONG TERM...BMD
AVIATION...LSA
MARINE...BMD
TIDES/COASTAL FLOODING...TMG
Area Forecast Discussion
National Weather Service Taunton MA
1004 PM EDT Fri May 5 2017
.SYNOPSIS...
Low pressure over Pennsylvania will continue to move north
into Upstate NY. This will draw another surge of rain up the
coast overnight, moving off by morning. The weather system will
linger near New England Saturday and Sunday, as will associated
showers. Cooler and unsettled weather follows beginning Sunday
and continues through a majority of next week.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Radar shows another area of rain moving up from south of Long
Island toward RI and Eastern MA. The 00Z HRRR radar imagery
shows the heaviest action moving across SE MA in two
bursts...one around 04Z and the second 08Z to 11Z. The weather
map shows low pressure over PA moving north. A warm front
extends from the low and along our South Coast and extending up
across Southeast Mass. The warm front will be pulled north with
the PA low.
So expect a cloudy night with winds turning from the south as
that warm front drifts north. Off/on rain continues with best
chance for the heavier amounts in RI and SE Mass.
Given the period of light precip this evening...generally less
than 0.05 inches...the likelihood of flooding has diminished
substantially. But we will keep the Flood Watch going for a few
more hours until the nature of the next area of rain becomes
clear on radar rather than on model projections.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
Saturday into Saturday night...
Bulk of the heavy rain shifts offshore but showery weather lingers
throughout the period. Crux of deep-layer moisture pushing slowly
E offshore with the pre-frontal trough. Drier air wrapping into
the system along with cooler air ahead of the pendant low continuing
to deepen and transition into an occluding phase over PA / Upstate
NY. Accompanying fair amount of mid-level energy across the region
as lapse rates steepen with the gradual cold air advection. Available
moisture and some weak instability, expecting some scattered shower
activity, some of it perhaps moderate to heavy. Drying out towards
Sunday morning. Chance PoPs for shower activity. Slight chance thunder
mention.
On a brighter note, literally and however, with drier air entraining
into the region there is the possibility that cloud decks will become
broken to scattered allowing for sunshine. This will aid in steepening
low level lapse rates and potential later shower generation. Also
this may push temperatures in some areas to the 70 degree mark. If
not, thinking highs in the mid to upper 60s. Plenty of clouds overnight
will keep lows around the upper 40s. This in addition to lingering
warmer air aloft, the crux of cooler air associated with aforementioned
occluding low comes Sunday. See discussion below.
&&
.LONG TERM /SUNDAY THROUGH FRIDAY/...
*/ Highlights...
- Unseasonably cool and showery pattern through much of next week
*/ Discussion...
Medium range models and ensembles continue to give us high confidence
in overall pattern next week, that being an anomalous upper low which
takes up residence across Northeast and brings unseasonably cool
weather along with scattered showers from time to time through at
least Thu.
Most of clouds and showers will be diurnally driven, meaning it will
be dry overall but scattered showers are more likely to occur during
afternoon and evening each day. Pattern suggests light rainfall at
any given location, on order of 0.10" or less, but just enough to
keep it feeling damp and chilly.
Temperature profiles indicate it`s also possible that higher
elevations of NW MA see some wet snow mixed in Sun night or again
Mon night in any rain showers, but we don`t see any risk of
accumulation right now.
While timing of short waves around upper lows are nearly impossible
to accurately pinpoint this far out, models are suggesting best chance
of showers to be Thu as last of short waves rotates around exiting
upper low. It`s also possible that models are exiting system too
quickly, but for now we`ll follow consensus which indicates improvement
on Fri.
&&
.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short Term /through Saturday Night/...Moderate confidence.
Overnight...
IFR/LIFR prevails due to low ceilings, showers, and fog. Most of
showers will be focused near Cape Cod and Islands where embedded
thunder is also possible. Still have a concern for LLWS early
tonight as 2000 ft winds increase to 40-60kt from S/SE.
Should see drier conditions over W New England towards Saturday
morning while remaining under widespread rain and embedded +RA E.
Saturday into Saturday night...
Widespread -RA/RA pushing offshore with IFR/LIFR pushing E of the
terminals of S New England. SCT -SHRA/SHRA developing and lingering
through a majority of the timeframe, with a drying trend expected
overnight W to E. CIGS lifting, through the day W to E there is the
expectation of SCT-BKN MVFR / low-end VFR CIGS. S winds continue
with gusts up around 20 to 25 kts at times throughout.
KBOS TAF...Moderate confidence. IFR/LIFR tonight with E/NE flow.
LLWS thru 06z Sat due to S winds up to 40kt at 2000 ft.
KBDL TAF...Moderate confidence. IFR for most of tonight as flow
turns S/SE. Gradual improvement to MVFR toward daybreak Sat.
Outlook /Sunday through Wednesday/...
Moderate confidence.
Areas of MVFR ceilings and scattered showers at times, otherwise VFR
much of the time with ceilings 040-060.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short Term /through Saturday Night/...Moderate confidence.
Overnight...
Areas of rain with embedded heavier showers, thunderstorms
overnight. SE winds with gusts up to 30 kts, potential for
stronger gusts up to 40 kts with any heavier precipitation,
thunderstorms. Heightened waves 5-8 feet. Will address the gale
force wind threat in the SMALL CRAFT ADVISORY. Lowered
visibility with any moderate to heavy rain.
Saturday into Saturday night...
S winds continue with gusts up around 25 kts at times. This will
keep seas heightened around 5 to 8 feet. SMALL CRAFT ADVISORIES
continued. Morning rain followed by afternoon into evening
scattered shower activity. May see some breaks of sunshine in-
between. Lowered visibility with any moderate to heavy rain.
Outlook /Sunday through Wednesday/...
High confidence.
Weak low pressure meanders near southern New England through period
with scattered showers from time to time.
Winds diminish Sun but seas probably don`t fall below 5 ft on outer
coastal waters until late Mon. Light winds/calm seas Tue into Wed,
but winds shift to NE Wed and increase late in day, probably staying
under 25kt.
&&
.HYDROLOGY...
Keeping Flood Watch posted a few more hours overnight as we
continue to monitor runoff from earlier heavy rainfall into
small streams, and flooding of urban areas continues to ease.
We are also monitoring another surge of rain that is expected to
move up into RI and SE Mass after midnight with up to an inch
additional rain possible. Lesser amounts farther north and west.
Monitoring Pawtuxet River at Cranston RI for possible minor
flooding Saturday morning per coordination with NERFC.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...Flood Watch until 8 AM EDT Saturday for MAZ005>007-012>024.
RI...Flood Watch until 8 AM EDT Saturday for RIZ001>008.
MARINE...Small Craft Advisory until 6 AM EDT Sunday for ANZ231>237-250-
251-254>256.
Small Craft Advisory until 10 PM EDT this evening for ANZ230.
&&
$$
SYNOPSIS...Sipprell/JWD
NEAR TERM...WTB/Sipprell/JWD
SHORT TERM...Sipprell
LONG TERM...JWD
AVIATION...WTB/Sipprell/JWD
MARINE...WTB/Sipprell/JWD
HYDROLOGY...
Area Forecast Discussion
National Weather Service Green Bay WI
1045 PM CDT Fri May 5 2017
Updated aviation portion for 06Z TAF issuance
.SHORT TERM...Tonight and Saturday
Issued at 222 PM CDT Fri May 5 2017
The latest rap analysis and satellite/radar imagery show a weak
ridge of high pressure currently moving across northern Wisconsin
early this afternoon. Meanwhile, equally weak low pressure is
moving southeast over northern Minnesota. Scattered showers in a
mid-level warm advection zone ahead of the low are sliding southeast
across western Lake Superior and about to enter into north-central
WI. Additional showers are also moving towards northern Lake
Superior just ahead of a rather impressive and compact shortwave. As
this shortwave and associated surface low move south across the
forecast area, precip chances and trends are the main forecast
concerns.
Tonight...The compact shortwave will quickly move southward across
the forecast area during the evening before exiting early overnight.
QG forcing and steep mid-level lapse rates accompanying the
shortwave should lead to fairly widespread shower activity, though
models bring the highest qpf axis in different locations. Based on
the latest observations, tend to think that the most widespread
shower activity will track across north-central WI to the southern
Fox Valley. Given the magnitude of the forcing, cannot rule out a
few thunderstorms either. Once the showers depart, another cool
airmass will filter into the region with breezy north winds. Would
not be surprised to see another low stratus deck push into northern
WI late tonight.
Saturday...Any low stratus deck should erode by mid-morning because
of the shallow nature of the cool airmass and increasing mixing of
dry air downward. Then mostly sunny conditions should resume region-
wide as very dry air pushes in from the north. Though temps should
only top out around 50 in the north and upper 50s south, dewpoints
in the teens and 20s should support relative humidities between 25
and 35 percent. Some of the sandy soil locations could see
humidities fall even further. Fire weather concerns will become
elevated with these conditions, though some rainfall tonight would
alleviate some of the concerns.
.LONG TERM...Saturday Night Through Friday
Issued at 222 PM CDT Fri May 5 2017
Focus in the long term period will be on temperatures, relative
humidity, and the resulting elevated fire weather conditions
during the day and frost/freeze potential overnight.
The Hudson Bay high will continue sinking southward into the area
Saturday night and Sunday, bringing a dry air mass with it. Dew
points are in the upper teens and 20s, but there will be enough
wind Saturday night to keep temperatures in the upper 20s in
north- central Wisconsin and in the low and middle 30s in east-
central Wisconsin. This will likely need to be monitored more
closely in later shifts with southern counties currently featuring
frost/freeze headlines. As winds subside Sunday evening, would
expect cooler temperatures on Monday morning, with lows in the low
to middle 20s in nor, making widespread frost and/or freeze
conditions more likely to occur. Meanwhile, daytime relative
humidity values Sunday, Monday, and even Tuesday will fall into
the 25 to 35 percent range, with some northern locations falling
close to 20 percent. These details are highlighted further in the
latest Fire Weather Forecast (FWF).
Models are in somewhat better agreement when it comes to the
middle of next week. The overall pattern keeps Wisconsin
positioned between two systems, one over the northeast CONUS and
the other one in the southern Rockies. Models generally agree that
this block remains intact until the middle or end of next week,
and the ridge over the Plains will slowly break down. A few
pieces of energy may eject out and bring a slight chance of
showers to parts of the area, but nothing substantial at this
point.
Temperatures will be below normal through the weekend. Next week
high temperatures moderate to right around normal, with lows still
slightly below.
&&
.AVIATION...for 06Z TAF Issuance
Issued at 1045 PM CDT Fri May 5 2017
A fast moving cold front will bring scattered showers and
isolated thunderstorms across the region this evening. Mainly VFR
cigs expected with the precipitation, though vsbys may fall to
MVFR in the heavier downpours. Potential remains for MVFR cigs
developing overnight in the wake of the system and influx of
colder air behind it. Any low cigs should clear by mid-morning on
Saturday, then north winds to become gusty through Saturday
afternoon.
&&
.MARINE...
Issued at 222 PM CDT Fri May 5 2017
After the fast moving system moves through tonight, winds
will then turn north and become gusty again along the nearshore
waters, especially for Saturday. Will end the the current small
craft advisory and reissue a new small craft advisory for late
tonight into Saturday night.
&&
.FIRE WEATHER...
Issued at 222 PM CDT Fri May 5 2017
A very dry air mass will drop into the Great
Lakes Region this weekend on north to northeast winds from a
Hudson Bay high pressure system. Much of northern Wisconsin will
likely see afternoon minimum humidity in the mid 20s, with lower
humidity in the upper teens over sandy regions. Temperatures will be
on the cool side but north winds will be gusty. Will continue
to highlight these parameters in the forecast for the weekend.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM.....MPC
LONG TERM......KLB
AVIATION.......Kurimski
MARINE.........MPC
FIRE WEATHER...MPC
Area Forecast Discussion
National Weather Service Gray ME
1155 PM EDT Fri May 5 2017
.SYNOPSIS...
A broad low pressure system approaching from the Tennessee
Valley will bring a return to cool temperatures and widespread
rain through Saturday. Some of that rain could be heavy at
times...and lead to new or continued flooding on some area
rivers. The system will stall over the region into next week
with the cool and unsettled weather expected to continue.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
1155 PM...Minor ESTF update to reflect current radar trend and
the mesonet in near term grids.
Prev Disc...
1035 PM Update...Have made a few mainly minor adjustments to the
forecast this evening. The bulk of the earlier heavier rain has
moved out of the CWA. However, light rain and even some drizzle
remains. Contemplated taking the flood watch down for a good
portion of the CWA here this evening. However, latest HRRR runs
show a reemergence of heavy shower/tstm potential later tonight
in the deep layer moist meridional flow. Therefore, will leave
the flood watches up at this time. Otherwise, lowered pops for
the next few hours until more widespread shower activity
arrives.
745 PM Update...Have updated the forecast, mainly PoPs for the
next few hours. Radar mosaics show the heaviest rain just
offshore of Portland at this time, which will move to the
midcoast over the next couple of hours. Other than that, we
expect mainly showery, drizzly precipitation for the rest of the
region through midnight. Elevated instability does come into
play after midnight all areas, so a few rumbles possible. In
addition, winds may gust up to 30 MPH, mainly on the coastal plain
this evening as the low level jet traverses the region.
6 PM Update...Just a few minor adjustments to the going forecast
based on latest trends in radar returns and temperatures.
heaviest band of rain of the night is currently sliding
northward across southeastern zones at this time. This band will
continue to move northward throughout the evening with locally
heavy rain. This could result in local urban and poor drainage
flooding as well as rises on rivers.
Previously...
The deep upper low over the Tennessee Valley slowly lifts
northeast tonight and become negatively tilted allowing a very
moist south to southeast flow at all levels to advect high
PWAT`s across the area. Models still suggesting highest QPF to
be over coastal and eastern most areas of our CWA with amounts
in the range of 2.0-3.0 inches with 1 to 2 inches further north
and west. We will be issuing a Flood Watch for tonight through
18z Sat across southern and eastern areas (see hydro section
below). Stayed close to RFCQPF forecast. There could be enough
of a wind field/shear to produce widely scattered thunderstorms
tonight over southern areas. Temps will move little tonight and
remain in the mid-upper 40s based due to the cool onshore flow
off the Atlantic.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
The moist unstable south to southeast flow will continue
Saturday through Saturday night. Models indicate there may be a
dry slot that briefly moves through the area in the afternoon
so some brief partial clearing will occur but scattered showers
will still linger due to the instability and moist flow. Clouds
and showers will continue through Saturday night along with the
southerly flow. Not much of a diurnal temp range from Sat to Sat
night with temps ranging from the upper 40s to mid 50s, coolest
along the coast.
&&
.LONG TERM /SUNDAY THROUGH FRIDAY/...
Models continue to hold onto the very blocky 500 mb pattern
across NOAM and adjacent oceans through next week, with closed
lows influencing New England through the period. The
models...especially the 12Z Euro...is showing a bit more
variability through the period with some slightly stronger
ridging N of the main closed low to our south. An optimist
could hope for some breaks in the shower chances and a little
more sun at times based on these forecasts, but in these
situations, the pessimist says that the models will change again
and could bring us into an even more dreary pattern. As such
have tried some fine tuning earlier in the forecast, but then
went with general chc pops Tue-Fri, and SuperBlend temps thru
the period which produce cooler than normal highs and near to
above normal mins.
For the details in the early part of the long range, the models
keep the closed low to the west into sunday, with a more
pronounced S-SW flow, and warmer air aloft. This will increase
the chance for breaks of sun, especially away from the coast,
and lower the threat for showers. Also temps will be a few
degrees warmer ranging from the low to mid 60s in interior srn
NH and CT vly to 55-60 on the coast and in central ME.
Models have been producing a wave moving around the base of the
trough Sunday night and then tracking N across the CWA Sun
night, which will provide a greater threat for rain, although
there is a trend for this slug of precip to move further N and
E. Monday could see some drier air move in behind the wave with
some weak sfc ridging showing up, So could see some sun during
the morning. However cold pool aloft will be shifting overhead
and this will likely allow clouds and sct showers to develop
during the afternoon with highs in the 50s. Monday night may
also be drier but chilly with lows in the upper 30s to low 40s.
After Monday, forecast confidence dwindles, as closed lows and
blocking begins to shift around a bit, so have just kept things
mostly cloudy with chc pops and highs in the 50s with lows in
the 40s. There will probably be more variability to the
forecast than this, but trying to time the changes is a daunting
prospect at this point.
&&
.AVIATION /04Z SATURDAY THROUGH WEDNESDAY/...
Short Term...IFR/LIFR conditions expected tonight improving to
MVFR with LCL IFR on Sat into Sat night.
Long Term... MVFR variable to VFR on Sunday, with MVFR to IFR
returning Sun night, then back to VFR-MVFR on Monday. Tue/Wed
will likely see conds vary between VFR and MVFR, with the best
chc of VFR during each morning.
&&
.MARINE...
Short Term /through Saturday/...An increasing south to
southeast flow will bring a return of small craft conditions
tonight through Saturday. Winds and seas will reach minimal SCA
conditions tonight but conditions to diminish on Saturday.
Long Term...Seas likely to remain high due to swell Sunday and
Monday, but otherwise conds should be sub-SCA through Wednesday.
&&
.FIRE WEATHER...
A prolonged wetting period with cool damp conditions continues
through the weekend.
&&
.HYDROLOGY...
High flow continues to come through the upper Androscoggin
River as noted at Errol. The Androscoggin at Gorham will remain
mostly steady a few tenths of a foot above flood stage
today...before slowly falling based on current model forecasts
from the Northeast River Forecast Center.
Another round of widespread rainfall...on top of already swollen
rivers may bring renewed or prolonged flooding across the
forecast area by the weekend. Highest totals will be along the
Midcoast region of Maine where over two inches of rain is
expected. Much higher totals appear possible just east of our
forecast area. The location of this precipitation max will need
to be monitored with upcoming model runs.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Flood Watch through Saturday afternoon for MEZ009-013-014-
018>028.
NH...Flood Watch through Saturday afternoon for NHZ010-013-014.
MARINE...Small Craft Advisory until 8 AM EDT Saturday for ANZ151-153.
Small Craft Advisory until 8 AM EDT Sunday for ANZ150-152-154.
&&
$$
ES
Area Forecast Discussion
National Weather Service Louisville KY
1028 PM EDT Fri May 5 2017
.Forecast Update...
Issued at 1015 PM EDT Fri May 5 2017
The rain band over east central KY will continue to move east
through around midnight and then exit the region. Lows tonight still
look to bottom out in the lower 40s with patchy light fog possible
in spots.
We`ll see a break in the precip overnight before a potent, fast
moving low pressure dives southeast into the Ohio Valley. This wave
will bring rain showers back to the region around sunrise and last
through the morning and early afternoon hours before tapering off
during the late afternoon/evening hours. A cool, rainy Sat morning
still looks on track for much of the area. Some uncertainty still
exists as to when precip will completely exit the region, but at
least coverage of showers will be less from mid afternoon onward.
Also this potent wave is producing lightning over Wisconsin late
this evening and will need to better evaluate 0Z models to determine
the best area for isld storms based on the track this weather
system. For now, left the t-storm chances over east central KY late
tomorrow afternoon/evening.
&&
.Short Term (Now through Saturday Night)...
Issued at 255 PM EDT Fri May 5 2017
Broad upper low continues a very slow trek across the Tennessee
Valley today, with a deformation band still pivoting slowly across
southern Indiana and central Kentucky. This band continues to
produce steady light/moderate precip just west of the I-65 corridor.
HRRR has had a very good handle on this feature all day, and is the
model of choice for at least the next 6-12 hrs.
Expect the band of precip to slowly make its way eastward across
central Kentucky for the rest of the afternoon and evening, clearing
the I-65 corridor roughly 00-02Z and finally exiting the Bluegrass
around or just after midnight. QPF does not look as impressive as
what we saw earlier today, as there has been an overall decreasing
trend in intensity, so most locations can expect an additional
quarter inch.
Look for a break in the precip overnight once the main upper low is
far enough east, but a secondary disturbance will dive SSE out of
Manitoba, bringing another round of showers to the Ohio Valley on
Saturday and keeping temps unseasonably chilly. Will carry likely
POPs especially during the morning hours, with a drying trend by
mid/late afternoon as the precip pushes off to the south and east.
Could have some embedded thunder in the Bluegrass region and
into south-central Kentucky where there is more opportunity to
destabilize. Low freezing levels and steep low-level lapse rates
could even support some small hail late in the day in east-central
and south-central Kentucky. Persistent cloud cover will limit max
temps to the mid/upper 50s north and east of a line from Tell City
to Lake Cumberland, and just the lower/mid 60s in south central KY.
We`ll clear off from west to east Sat night as high pressure builds
in. Temps will drop into the mid/upper 30s by Sunday morning in
many areas, but with just enough wind to keep the temps fairly
uniform and preclude much in the way of frost formation.
.Long Term (Sunday through Friday)...
Issued at 255 PM EDT Fri May 5 2017
...Frost Potential Increasing For Sunday Night...
Rising heights and building surface high pressure will dominate
Sunday into Monday, but temps will continue to run solidly below
climo as the low-level thermal trof is slow to depart. Main impact
is potential frost Sunday night into Monday morning, especially
across the Bluegrass. We are still talking about 5th period here,
and any freezing temps will be quite localized, so no need yet for a
Freeze Watch and too early for a Frost Advisory. Will continue to
mention in the Hazardous Weather Outlook, and likely ramp up
messaging over the weekend as confidence in this scenario increases.
Low-confidence forecast from Monday night onward with a blocking
upper low just off the East Coast through the middle of the week.
NW flow pattern over the Ohio Valley will be less progressive than
most, but will likely have disturbances interacting with a nearly
stationary front. POPs will remain in the 20-30% range for most
during the middle of the week, but chances will increase later in
the week as moisture continues to feed northward. Best chances will
be across the Tennessee Valley, and will follow the model consensus
of likely POPs Thu-Fri across south-central Kentucky.
&&
.Aviation (00z TAF Update)...
Issued at 745 PM EDT Fri May 5 2017
Light rain band oriented north-south has finally pushed east of the
I-65 corridor, with SDF and BWG lifting to VFR. VFR will be
predominant for the remainder of the evening and overnight hours.
The only concern could be some light fog at BWG given the clearing
trend. Northwest winds will gradually slacken overnight and become
more westerly toward 12z. IFR continues at LEX this hour, but this
should improve to Fuel Alternate MVFR around or shortly after
01z. Expect a period of light rain over the next few hours, with
MVFR persisting at LEX through midnight or so.
For the overnight period, skies look mostly clear. Can`t rule out
some patchy, light fog, but low level moisture profiles don`t
suggest dense fog. Clouds and rain return for Derby Day, however,
with MVFR ceilings returning between 12-15z at all three sites. MVFR
vsbys will be common as well in steady rain. Some of the recent hi-
res guidance suggests the bulk of this steady rain could pass just
southwest of LEX. Expect improving conditions as rain moves off to
the southeast by mid afternoon.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...None.
&&
$$
Update...AMS
Short Term........RAS
Long Term.........RAS
Aviation...EBW