Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS64 KMRX 271846

Area Forecast Discussion
National Weather Service Morristown TN
146 PM EST Fri Jan 27 2023

...New AVIATION...

(18Z TAFS)
Issued at 143 PM EST Fri Jan 27 2023

VFR will prevail, but minor wind gusts to near 20KT on occasion
through sunset.


Issued at 1110 AM EST Fri Jan 27 2023

Quick update to the zones to clean out morning wording. Nice
chilly, sunny day.



.SHORT TERM...(Today and tonight) Issued at 320 AM EST
Fri Jan 27 2023

1. Clearing skies today but temperatures cold this morning.
Higher pressure builds in and warmer this afternoon with southwest
winds increasing.


Currently, a few lingering snow flurries earlier this morning as low
level moisture hung on overnight across the northeast part of the
forecast area. Higher pressure was building in from the west and
southwest this morning and upper trough behind yesterdays system was
flattening the flow to become more zonal for today. Temperatures
early this morning are in the upper 20s to mid 30s with winds west
to northwest at 10 to 15 mph. Wind chill temperatures were in the
20s. Low level clouds have decreased across the south and west
overnight as the atmosphere dries out. The forecast for today and
tonight will be influenced by a broad upper trough across the
eastern U.S. with surface high pressure centered along the Gulf
Coast. The surface high will continue to build in and winds will
increase from the southwest in the afternoon which will warm
temperatures into the 40s. As the atmosphere continues to dry this
morning expect the clouds to continue to dissipate. During the day
skies will be sunny west and south and become sunny northeast by
afternoon. Tonight skies will stay clear. Light south to southwest
winds will hold temperatures up slightly with lows in the mid 20s to
the lower 30s.


.LONG TERM...(Saturday through Friday) Issued at 320 AM EST Fri
Jan 27 2023

1. An active pattern will continue through next week with rain
Sunday and then off and on through the rest of the week.

2. Locally heavy rainfall and/or a period of wintry precipitation
are possible next week.

3. While we have high confidence in an unsettled weather pattern,
forecast confidence is low in the extended with regard to exact
precipitation type and timing.


We begin the period with an anomalous ridging across the Eastern GoM
through the Bahamas and an amplified ridge pattern across the
eastern North Pacific. Zonal flow aloft will be the predominant
pattern with the upper-level flow across our area from the WSW.

A series of shortwaves traversing the upper flow will move across
the region over the coming days. On Sunday, a shortwave and
associated cold front will move across the area. Broad upper
divergence and increasing southerly boundary layer flow will result
in increased moisture and low-level convergence across the forecast
area bringing likely rain showers.

This front will stall near the area and will be a focus for
cyclogenesis with a couple of systems next week. The first system
will be Monday night into Tuesday as a strong 150 kt upper 300mb jet
produces broad upper divergence across the region and a weak
shortwave moves across the area. Cyclogenesis and isentropic lift is
expected to produce some precipitation across the region. However,
model guidance is uncertain with this system and has continued to
differ from run to run with the magnitude of cold air across the
region. At this point, moisture with this system appears minimal,
and will trend toward the NBM which keeps us mostly rain. The colder
GFS solution would bring some snow to our northern zones along the
Cumberland plateau and mountains through southwest Virgina, but at
this time, the GFS continues to be the colder outlier.

We continue to see several waves of unsettled weather through mid-
week with the next main system expected to arrive Wednesday night
into Thursday. The 180 kt upper jet across the Great Lakes through
the Northeast will result in fairly strong upper divergence from the
Tennessee Valley through the Central Appalachians with cyclogenesis
along the front in the lower Mississippi Valley. This low pressure
system will track northeast with heavier precipitation expected.
NAEFS ensembles show PW values reaching the 97th percentile across
the Tennessee Valley which is a decent moisture signal this far in
advance. We expect period of heavier rain to be possible with this
system, but much will depend on the exact track of the system. The
trend has been to keep the cold air to our north and west with
precipitation being primarily rain across our region. Model
agreement remains poor, so we will continue to trend toward the NBM
consensus during the extended. With the potential hazardous weather
but high uncertainty, we will maintain the low probability wording
within the HWO.


Chattanooga Airport, TN             32  58  42  51 /   0   0  30  90
Knoxville McGhee Tyson Airport, TN  32  55  38  49 /   0   0  30  80
Oak Ridge, TN                       30  55  38  47 /   0   0  30  90
Tri Cities Airport, TN              26  54  33  47 /   0   0  20  80





AVIATION...GC is the U.S. government's official web portal to all federal, state and local government web resources and services.